WO2016121393A1 - Cn比検出回路及び受信回路 - Google Patents
Cn比検出回路及び受信回路 Download PDFInfo
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- WO2016121393A1 WO2016121393A1 PCT/JP2016/000425 JP2016000425W WO2016121393A1 WO 2016121393 A1 WO2016121393 A1 WO 2016121393A1 JP 2016000425 W JP2016000425 W JP 2016000425W WO 2016121393 A1 WO2016121393 A1 WO 2016121393A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/26—Measuring noise figure; Measuring signal-to-noise ratio
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/10—Measuring sum, difference or ratio
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/005—Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller (comparing phase or frequency of 2 mutually independent oscillations in demodulators)
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/309—Measuring or estimating channel quality parameters
- H04B17/336—Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/20—Modulator circuits; Transmitter circuits
- H04L27/2003—Modulator circuits; Transmitter circuits for continuous phase modulation
- H04L27/2007—Modulator circuits; Transmitter circuits for continuous phase modulation in which the phase change within each symbol period is constrained
- H04L27/2017—Modulator circuits; Transmitter circuits for continuous phase modulation in which the phase change within each symbol period is constrained in which the phase changes are non-linear, e.g. generalized and Gaussian minimum shift keying, tamed frequency modulation
Definitions
- One embodiment of the present disclosure relates to a CN ratio detection circuit and a reception circuit that are provided in a wireless receiver or the like that receives a wireless signal of a modulation method having a constant amplitude such as FM.
- the audio signal output voltage (audio output voltage) is lowered (mute) or the high frequency component voltage of the audio is lowered according to the received radio signal voltage.
- signal processing such as high-cut is performed. The reason is to mitigate noise that is annoying in a low electric field environment.
- the car radio detects that the received radio signal voltage has dropped and performs signal processing (mute) to lower the audio output voltage.
- Signal processing (high cut) for lowering the voltage of high frequency components of audio is also performed for the same purpose.
- an antenna amplifier that amplifies a received signal is used together to compensate for a decrease in reception gain of the antenna element due to the miniaturization of the antenna element.
- An antenna with such an antenna amplifier is called an “active antenna”.
- An antenna amplifier of an active antenna amplifies not only radio signals including broadcast waves but also noise. That is, the active antenna has a noise floor that is higher than that of the rod antenna, so that the radio signal voltage is less likely to decrease even in a low electric field environment.
- This radio signal voltage may be used as a reference (operation point) for determining the application of the audio signal processing described above.
- S meter as a parameter
- S meter the radio signal voltage of the reception channel that is tuned and demodulated by the radio receiver.
- the signal processing operating point may be changed in accordance with the gain of the antenna amplifier.
- the audio signal processing is controlled using a carrier-to-noise ratio (CN ratio) as an index indicating the quality of the received radio signal. It is desirable.
- CN ratio carrier-to-noise ratio
- a received digital broadcast signal is demodulated to obtain a measurement constellation, and an error (power ratio) between the demodulated measurement constellation and the theoretical constellation is calculated as CN ratio 1
- a modulation error ratio (MER) corresponding to one-to-one
- JP 2002-124931 A Japanese Patent Laid-Open No. 5-63593
- the present disclosure provides a CN ratio detection circuit and a reception circuit that can accurately calculate the CN ratio of an FM broadcast reception signal.
- the CN ratio detection circuit includes a voltage detection unit, an averaging unit, a time variation calculation unit, and a CN ratio calculation unit.
- the voltage detector measures the input voltage of the signal.
- the averaging unit calculates an average value of the input voltage within a predetermined time.
- the time fluctuation range calculator calculates the time fluctuation range of the input voltage within the predetermined time.
- the CN ratio calculation unit calculates the CN ratio of the signal using the average value of the input voltage and the time fluctuation range.
- the reception circuit includes a demodulation unit, a CN ratio detection circuit, and an audio signal processing unit.
- the demodulator demodulates the received signal.
- the CN ratio detection circuit calculates the CN ratio of this received signal.
- the audio signal processing unit performs audio signal processing on the received signal after demodulation according to the calculated CN ratio.
- the CN ratio detection circuit includes a voltage detection unit, an averaging unit, a time fluctuation width calculation unit, and a CN ratio calculation unit.
- the voltage detector measures the input voltage of the received signal.
- the averaging unit calculates an average value of the input voltage within a predetermined time.
- the time fluctuation range calculator calculates the time fluctuation range of the input voltage within the predetermined time.
- the CN ratio calculation unit calculates the CN ratio using the average value of the input voltage and the time fluctuation range.
- the CN ratio of the FM broadcast reception signal can be calculated with high accuracy.
- FIG. 9 is a block diagram illustrating a configuration of a wireless receiver according to the second embodiment.
- FIG. The figure which shows the measurement result of the standard deviation of S meter in Embodiment 2
- the figure which shows the measurement result of CN ratio in Embodiment 2 FIG.
- FIG. 4 is a block diagram illustrating a configuration of a wireless receiver according to a third embodiment.
- FIG. 9 is a block diagram showing another configuration of the wireless receiver according to the third embodiment.
- Block diagram of CN ratio detection circuit in the fourth embodiment The figure which shows the measurement result of CN ratio and S meter in Embodiment 4
- Patent Document 1 The method disclosed in Patent Document 1 is based on a digital modulation radio system, and obtains a constellation symbol by performing synchronous detection. Therefore, it cannot be applied to FM radio broadcasting, which is an analog modulation radio system.
- FIG. 1 is a block diagram showing an example of the configuration of a wireless receiver examined by the present inventors.
- the radio signal received by the antenna 11 is input to the antenna amplifier 12, and the output signal of the antenna amplifier 12 is input to the reception circuit 13.
- the receiving circuit 13 outputs an audio signal that is an output of the audio signal processing to the speaker 14.
- the wireless receiver 10 receives FM radio broadcast as a radio signal, and outputs sound of the broadcast content from the speaker 14.
- the front-end circuit (F / E circuit) 15 appropriately performs amplification of the radio signal output from the antenna amplifier 12, frequency conversion, filtering using a band-pass filter, and the like.
- the F / E circuit 15 finally outputs a signal (FM modulation signal) of the frequency of the reception target channel (reception channel) to the demodulation unit 16 and the S meter detection unit 17.
- the demodulator 16 performs FM demodulation on the signal input from the F / E circuit 15 and outputs the obtained audio signal to the audio signal processor 18.
- the S meter detection unit 17 calculates an S meter from the signal input from the F / E circuit 15 and outputs the calculated S meter to the audio signal processing unit 18.
- the audio signal processing unit 18 lowers the voltage (mute) of the audio signal input from the demodulation unit 16 according to the S meter input from the S meter detection unit 17 or decreases only the voltage of the high frequency component ( Audio signal processing such as high cut). That is, the audio signal processing unit 18 uses the S meter as an operating point of audio signal processing (determination criteria for processing application).
- FIG. 2 is a diagram showing a radio signal voltage measurement system 20 that is equivalent to the reception environment of the radio receiver 10 shown in FIG.
- the measurement system 20 includes a standard signal source 21, an antenna dummy circuit 22, an antenna amplifier 23, and a reception circuit 24.
- the output of the standard signal source 21 is connected to the input part of the antenna dummy circuit 22
- the output of the antenna dummy circuit 22 is connected to the input part of the antenna amplifier 23, and the output of the antenna amplifier 23 is the reception circuit 24. Connected to the input section.
- the antenna amplifier 23 and the receiving circuit 24 correspond to the antenna amplifier 12 and the receiving circuit 13 shown in FIG.
- FIG. 3 shows the measurement result of the radio signal voltage (S meter) in the receiving circuit 24.
- S meter shows the measurement result when using an antenna amplifier (S meter (with amplifier)) and a measurement result when not using an antenna amplifier as a simulation of a rod antenna (S meter (without amplifier)) are shown. Show.
- the gain of the antenna amplifier 23 is 10 dB.
- the S meter when the antenna amplifier is used is about 10 dB higher than the S meter at the same input level when the antenna amplifier is not used.
- the S meter when used as a criterion for applying the audio signal processing, the input level at which the audio signal processing (mute or high cut or the like) operates varies depending on the presence or absence of the antenna amplifier.
- the audio signal processing software is set to apply the audio signal processing when the S meter is 8 dB ⁇ V or less.
- the audio signal processing is applied at an input level of 8 dB ⁇ V or less, but when the antenna amplifier is used, the audio signal processing is applied at an input level of ⁇ 5 dB ⁇ V or less. That is, the input level at which the audio signal processing operates is shifted depending on the presence or absence of the antenna amplifier.
- the audio signal processing software is set to apply the audio signal processing when the S meter is 0 dB ⁇ V or less.
- the audio signal processing is applied at an input level of 0 dB ⁇ V or less.
- the audio signal processing is not applied because the S meter does not drop to 0 dB ⁇ V.
- an S meter which is a simple radio signal voltage, makes it possible to perform audio signal processing equivalent to when an antenna amplifier is not used in a weak electric field environment when the antenna amplifier is used. End up.
- An object of one embodiment of the present disclosure is to accurately calculate a CN ratio for an analog modulation type radio signal such as FM.
- FIG. 4 is a block diagram showing a configuration of the radio receiver according to the present embodiment.
- the same components as those of the wireless receiver 10 shown in FIG. 4 are identical to the wireless receiver 10 shown in FIG.
- the wireless receiver 100 shown in FIG. 4 includes an antenna 11, an antenna amplifier 12, a receiving circuit 101, and a speaker 14.
- the wireless signal received by the antenna 11 is input to the antenna amplifier 12, and the output signal of the antenna amplifier 12 is input to the receiving circuit 101.
- the receiving circuit 101 outputs an audio signal that is an output of the audio signal processing to the speaker 14.
- the radio receiver 100 receives FM radio broadcast as a radio signal and outputs the audio of the broadcast content from the speaker 14.
- the reception circuit 101 includes an F / E circuit 15, a demodulation unit 16, a CN ratio detection circuit 102, and an audio signal processing unit 18.
- the CN ratio detection circuit 102 calculates the CN ratio of the signal input from the F / E circuit 15 and outputs the calculated CN ratio to the audio signal processing unit 18.
- the audio signal processing unit 18 lowers the voltage (mute) with respect to the audio signal input from the demodulating unit 16 according to the CN ratio input from the CN ratio detection circuit 102 or decreases only the voltage of the high frequency component ( Signal processing such as high cut). Specifically, the audio signal processing unit 18 uses the CN ratio input from the CN ratio detection circuit 102 as an operating point for audio signal processing.
- the CN ratio detection circuit 102 includes a voltage detection unit 103, an averaging unit 104, a time fluctuation width calculation unit 105, and a CN ratio calculation unit 106.
- the output signal from the F / E circuit 15 is input to the CN ratio detection circuit 102. Also, the CN ratio that is the calculation result of the CN ratio detection circuit 102 is output to the audio signal processing unit 18.
- the voltage detection unit 103 measures the input voltage.
- the voltage detection unit 103 outputs the measured input voltage to the averaging unit 104 and the time variation calculation unit 105.
- the input voltage obtained by the voltage detection unit 103 may be a value reflecting the intensity of the received signal, and is not limited to a voltage value at a specific location in the receiving circuit 101.
- the input voltage of the received signal may be a value obtained by adding a calculation to the measured voltage value.
- the following values can be used as the input voltage of the reception signal in this embodiment.
- the input voltage may be a baseband signal voltage in the subsequent stage of the F / E circuit 15 or a radio signal voltage in the previous stage of the F / E circuit 15 of the receiving circuit 101.
- the radio signal voltage (S meter) is calculated as a value obtained by back-calculating the gain or loss of the processing (for example, LNA (Low Noise Amplifier)) in the F / E circuit 15 to the voltage of the baseband signal.
- voltage detector 103 calculates an S meter as the input voltage.
- the averaging unit 104 averages the voltage for the predetermined time T0 with respect to the S meter (input voltage) input from the voltage detection unit 103, and calculates the average value S_ave of the S meter within the predetermined time T0.
- the averaging unit 104 outputs the calculated average value S_ave of the S meter to the CN ratio calculation unit 106.
- the time fluctuation width calculation unit 105 calculates the time fluctuation width S_dev of the S meter within a predetermined time T0 for the S meter (input voltage) input from the voltage detection unit 103.
- the time fluctuation width calculation unit 105 outputs the calculated time fluctuation width S_dev of the S meter to the CN ratio calculation unit 106.
- the CN ratio calculation unit 106 calculates the CN ratio using the average value S_ave of the S meter input from the averaging unit 104 and the time variation width S_dev of the S meter input from the time variation width calculation unit 105. For example, the CN ratio calculation unit 106 calculates the ratio of the square of the average value S_ave of the S meter and the product of the square of the time variation width S_dev of the S meter and a constant N as shown in the following formula (1). C / N [dB]. In equation (1), the unit of S_ave and S_dev is volt.
- Equation (2) The reason why the CN ratio can be calculated using Equation (2) is that the noise energy is obtained as the time fluctuation width of the S meter.
- the average energy of the noise is proportional to 2 ⁇ (square of the standard deviation of the S meter).
- the calculation accuracy of the standard deviation in the time variation calculation unit 105 can be improved as the calculation time T0 is increased.
- the calculation accuracy is determined by the number of data samples.
- the probability that the calculation error of the CN ratio is 2 dB or more can be reduced to 10% or less by setting the number of data to 30 samples or more.
- the calculation time T0 in the averaging unit 104 and the time variation calculation unit 105 is preferably set to 1 millisecond or less in consideration of tracking of electric field variation and calculation accuracy.
- FIG. 5 shows the measurement result of the CN ratio in the CN ratio detection circuit 102 according to the present embodiment.
- FIG. 5 shows the CN ratio when the antenna amplifier 12 is used and the CN ratio when the antenna amplifier 12 is not used.
- the gain of the antenna amplifier 12 is 10 dB.
- the measurement result shown in FIG. 5 is a result of actual measurement performed by the inventor by mounting the CN ratio detection circuit 102 on the car radio tuner. At that time, the voltage detection unit 103 is provided in the baseband signal unit, and the CN ratio detection circuit 102 is micro-coded and mounted.
- the CN ratio detection circuit 102 calculates substantially the same CN ratio for the same input level regardless of whether the antenna amplifier is used.
- the audio signal processing unit 18 does not depend on the presence or absence of the antenna amplifier, and the antenna amplifier can be used even when the antenna amplifier is used. Audio signal processing equivalent to when no amplifier is used can be performed.
- the CN ratio detection circuit 102 calculates the CN ratio of the received signal using the average value of the input voltage of the received signal and the time fluctuation range. That is, the CN ratio detection circuit 102 calculates the CN ratio using the input voltage of the received signal.
- CN ratio can be calculated
- the CN ratio detection circuit 102 calculates the CN ratio using the received signal of the reception channel. Therefore, as in Patent Literature 2, the CN ratio detection circuit 102 separately uses a channel other than the reception channel in the case of FM radio broadcasting. The CN ratio can be measured without extracting a noise component. Thereby, in this Embodiment, CN ratio in a receiving channel can be measured accurately.
- the CN ratio of the FM broadcast reception signal can be calculated with high accuracy.
- the receiving circuit 101 can perform audio signal processing using the CN ratio calculated in the CN ratio detecting circuit 102. Therefore, even when the antenna amplifier 12 is used, the antenna amplifier As in the case of not using 12, the sound signal processing of the weak electric field can be appropriately performed.
- the audio signal processing can be performed using substantially the same CN ratio for the same input level regardless of whether the antenna amplifier is used or not. Complex processing such as changing the operating point of the audio signal processing in accordance with the gain of the antenna amplifier can be avoided.
- the receiving circuit 101 can appropriately perform audio signal processing such as mute and high cut according to the CN ratio in consideration of the noise voltage, and the wireless receiver 100 can eliminate the uncomfortable feeling of the audio output from the speaker 14. it can.
- the CN ratio detection circuit 102 is provided in a digital circuit that handles baseband signals.
- the CN ratio detection circuit 102 is placed in an RF analog circuit that handles intermediate frequency signals or radio signals. It is also possible to provide it.
- the averaging unit 104 and the time variation calculation unit 105 can be realized by using a low pass filter (LPF: Low Pass Filter), a peak hold circuit, or the like.
- LPF Low Pass Filter
- FIG. 6 is a block diagram showing a configuration of radio receiver 200 according to the present embodiment.
- the same components as those in the first embodiment (FIG. 4) are denoted by the same reference numerals, and detailed description thereof is omitted.
- a band-pass filter 201 is provided between the F / E circuit 15 and the demodulator 16 and a time variation correction unit in the CN ratio detection circuit 102. 202 is provided.
- the band-pass filter 201 extracts and extracts only the signal in the reception target frequency band (reception channel) from the FM modulation signal output from the F / E circuit 15. The signal is selectively output to the demodulator 16 and the CN ratio detection circuit 102. Further, the band pass filter 201 outputs the set bandwidth BPF_bw to the time fluctuation width correction unit 202 of the CN ratio detection circuit 102.
- the voltage detection unit 103 is electrically connected to the output terminal of the band pass filter 201, measures the voltage output from the band pass filter 201, and in the S meter as in the first embodiment. Convert. Also in the present embodiment, the S meter calculated by the voltage detection unit 103 is used as the input voltage.
- the time fluctuation width correction unit 202 calculates the time fluctuation width S_dev of the S meter (or the standard deviation S_devst of the S meter) input from the time fluctuation width calculation unit 105 according to the bandwidth BPF_bw input from the band pass filter 201. Correction is performed, and the time variation width S_dev_cor after correction of the S meter (or the standard deviation S_devst_cor after correction of the S meter) is output to the CN ratio calculation unit 106. Specifically, the time fluctuation range correction unit 202 determines that the value of the time fluctuation range S_dev of the S meter is lower than a reference value (hereinafter referred to as a noise level reference value N_lv) set according to the bandwidth BPF_bw. Corrects the value of the time variation width S_dev of the S meter to the noise level reference value N_lv.
- a reference value hereinafter referred to as a noise level reference value N_lv
- the CN ratio calculation unit 106 calculates the S meter average value S_ave input from the averaging unit 104 and the corrected time variation S_dev_cor of the S meter input from the time variation correction unit 202 (or after correction of the S meter).
- the CN ratio is calculated using the standard deviation S_devst_cor).
- the CN ratio calculation unit 106 may replace the time variation width S_dev of the S meter in Equation (1) with the time variation width S_dev_cor after correction of the S meter.
- the CN ratio calculation unit 106 may replace the standard deviation S_devst of the S meter in Equation (2) with the standard deviation S_devst_cor after correction of the S meter.
- a noise level reference value N_lv corresponding to the bandwidth BPF_bw of the band pass filter 201 is set in advance.
- the time fluctuation range correction unit 202 compares the time fluctuation range S_dev of the S meter input from the time fluctuation range calculation unit 105 with the magnitude of the noise level reference value N_lv.
- FIG. 7 shows a comparison result between S_dev and N_lv in the time variation correction unit 202 and an output value based on the comparison result.
- the time variation width correction unit 202 when the time variation width S_dev of the S meter is equal to or greater than the noise level reference value N_lv, the time variation width correction unit 202 outputs the time variation width S_dev of the S meter as it is (Case 1: no correction). On the other hand, when the time fluctuation width S_dev of the S meter is less than the noise level reference value N_lv, the time fluctuation width correction unit 202 outputs the noise level reference value N_lv as the corrected time fluctuation width S_dev_cor of the S meter (Case 2: With correction).
- the purpose of correcting the time fluctuation width of the S meter in the time fluctuation width correction unit 202 is to extend the CN ratio measurement range to a low CN ratio area (low CN ratio area).
- the thermal noise power (kTB: k is defined by the bandwidth BPF_bw of the bandpass filter 201).
- the Boltzmann constant, T should be an absolute temperature, and B should not drop below a voltage determined by the bandwidth (ie BPF_bw).
- FIG. 8 shows an actual measurement result of the input level characteristic of the standard deviation S_devst of the S meter.
- time variation width S_dev of the S meter decreases in the low CN ratio region is that the value of the S meter is close to the lower voltage limit (0V), and the distribution of time variation of the S meter deviates from the normal distribution. is there. In this state, it is considered that the time fluctuation width S_dev of the S meter output from the time fluctuation width calculator 105 of the S meter does not represent the actual noise level.
- the CN ratio in the low CN ratio region appears higher than the actual value. Therefore, in the low CN ratio region, the calculation accuracy of the CN ratio is deteriorated as compared with other regions.
- the time variation correction unit 202 presets the noise level reference value N_lv as the lower limit value of the voltage determined from the power of the thermal noise defined by the bandwidth BPF_bw of the band pass filter 201, and the time variation width S_dev of the S meter.
- the noise level reference value N_lv is used as a threshold value for determining whether or not represents an appropriate noise level. That is, when the time fluctuation width S_dev of the S meter is less than the noise level reference value N_lv, the time fluctuation width correction unit 202 determines that the value of the time fluctuation width S_dev of the S meter is not an appropriate value, and the noise level reference value N_lv is output as the time variation width S_dev_cor after correction of the S meter.
- FIG. 9 shows the measurement result of the CN ratio in the CN ratio detection circuit 102 according to the present embodiment.
- FIG. 9 shows a CN ratio when the time variation width of the S meter is corrected and a CN ratio when the time variation width of the S meter is not corrected.
- FIG. 9 shows a case where the antenna amplifier 12 is not applied.
- the CN ratio in the low CN ratio region (for example, CN ratio: 10 dB or less)
- the time variation width of the S meter is uncorrected
- the measured value of the CN ratio is reduced only to 5 dB.
- the CN ratio has dropped to around 2 dB. That is, by correcting the time variation width of the S meter, the actual noise level can be specified more accurately than when the time variation width of the S meter is not corrected, and the CN ratio in the low CN ratio region can be specified. The calculation accuracy of can be improved.
- the time fluctuation width correction unit 202 corrects the time fluctuation width S_dev of the S meter, thereby calculating the accuracy of the time fluctuation width (noise level) of the S meter used for calculating the CN ratio. Can be improved. As a result, the CN ratio measurement range can be extended to the low CN ratio region, and the operating point of the audio signal processing in the low CN ratio region can be appropriately set.
- the CN ratio of the FM broadcast reception signal can be calculated more accurately than in the first embodiment.
- the receiving circuit 101 may include a plurality of bandpass filters 201 having different bandwidths, and may employ a configuration in which different bandpass filters 201 having different bandwidths are used depending on the reception state.
- the time fluctuation width correction unit 202 holds a noise level reference value table corresponding to each of the bandwidths of the plurality of bandpass filters 201 in advance, and noise corresponding to the bandwidth of the bandpass filter 201 being used.
- a level reference value may be used.
- the CN ratio detection circuit 102 can reduce the low CN ratio region.
- the CN ratio can be detected with high accuracy.
- FIG. 10 is a block diagram showing a configuration of radio receiver 300 according to the present embodiment.
- the same components as those in the first embodiment (FIG. 4) or the second embodiment (FIG. 6) are denoted by the same reference numerals, and detailed description thereof is omitted.
- a band pass filter 201 is provided between the F / E circuit 15 and the demodulator 16 as in the second embodiment, and the CN ratio detection circuit.
- the determination unit 301 and the switch 302 are provided in 102.
- the voltage detection unit 103 converts the voltage output from the band-pass filter 201 into an S meter as in the second embodiment, and uses the S meter as an input voltage.
- the determination unit 301 compares the S meter input from the voltage detection unit 103 with the CN ratio input from the CN ratio calculation unit 106, and the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal. It is determined whether or not it is in a state.
- the determination unit 301 outputs the determination result to the switch 302.
- the switch 302 is a 2-input 1-output switch.
- the switch 302 receives the S meter output from the voltage detection unit 103 and the CN ratio output from the CN ratio calculation unit 106.
- the switch 302 selects one of the S meter and the CN ratio based on the determination result of the determination unit 301, and outputs the selected value to the audio signal processing unit 18.
- the switch 302 outputs an S meter, and the determination unit 301 outputs the band pass.
- the CN ratio is output.
- the bandwidth of the band-pass filter 201 When the bandwidth of the band-pass filter 201 is narrower than the occupied bandwidth of the input signal, a part of the input signal is lost by the band-pass filter 201, so that the sound distortion is relatively large. Further, when the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal, a part of the input signal is lost, so that the time fluctuation width calculation unit 105 in the CN ratio detection circuit 102 has a noise level. As a result, it becomes impossible to calculate an appropriate time fluctuation range.
- the frequency of the carrier wave varies with time.
- the bandwidth of the bandpass filter 201 is narrower than the occupied bandwidth of the input signal, the frequency of the carrier wave goes out of the passband of the bandpass filter 201 or returns to the passband of the bandpass filter 201. Will repeat.
- the measured voltage also decreases instantaneously.
- the voltage measured by the voltage detection unit 103 is significantly lower than the original voltage of the input signal, so that the time fluctuation width of the input voltage (S meter) becomes large.
- the output value S_dev of the time variation calculation unit 105 is such that the bandwidth of the band pass filter 201 is wider than the occupied bandwidth of the input signal. It becomes a larger value than when it is (the normal state).
- the calculation result of the CN ratio in the CN ratio calculation unit 106 is compared with the calculation result of the CN ratio in the normal state. It becomes very small value. That is, the accuracy of the CN ratio calculated when the bandwidth of the band-pass filter 201 is narrower than the occupied bandwidth of the input signal has deteriorated, and is not suitable for use in controlling audio signal processing.
- the determination unit 301 determines that the bandwidth of the bandpass filter 201 is narrower than the occupied bandwidth of the input signal, the determination unit 301 instructs the switch 302 to select the S meter (that is, the determination result). Is output.
- the switch 302 switches to a state in which the S meter is output to the audio signal processing unit 18.
- the determination unit 301 when determining that the bandwidth of the bandpass filter 201 is equal to or greater than the occupied bandwidth of the input signal, the determination unit 301 outputs a control signal (that is, a determination result) instructing the switch 302 to select the CN ratio. To do.
- the switch 302 switches to a state in which the CN ratio is output to the audio signal processing unit 18.
- 11 to 13 show the measurement results of the S meter and the CN ratio in a normal state and in a state where the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal.
- the maximum frequency deviation ⁇ f [kHz] 75 [kHz] ⁇ modulation rate r (the modulation rate r is usually expressed as a percentage (%)).
- the modulation rate r is usually expressed as a percentage (%)).
- the bandwidth of the bandpass filter 201 under the measurement conditions for acquiring the data of FIGS. 11 to 13 is 120 kHz.
- FIG. 11 shows the time characteristics of the S meter and the CN ratio at a modulation rate of 60% (normal state)
- FIG. 12 shows the time characteristics of the S meter and the CN ratio at a modulation rate of 70%.
- Reference numeral 13 denotes time characteristics of the S meter and CN ratio at a modulation rate of 80%.
- FIGS. 11 and 12 show a normal state (bandwidth of the bandpass filter 201> required bandwidth B), and FIG. 13 shows a state where the bandwidth of the bandpass filter 201 is narrower than the necessary bandwidth B. Show.
- the S meter also shows time fluctuations depending on the modulation rate. However, the S meter does not change as markedly as the CN ratio.
- the change in the time characteristic of the measured CN ratio according to the magnitude relationship between the bandwidth of the band-pass filter 201 and the occupied bandwidth of the input signal (required bandwidth B). Appears significantly in comparison with the change in the time characteristics of the S meter. Specifically, the time variation of the CN ratio (difference between the CN ratio and the S meter) increases as the occupied bandwidth (required bandwidth B) of the input signal increases with the bandwidth of the bandpass filter 201 being constant. Become.
- the determination unit 301 pays attention to the time characteristic of the CN ratio, and the bandwidth of the band-pass filter 201 depends on whether the calculated CN ratio is within an assumed range or not. It is determined whether or not the state is narrower.
- FIG. 14 shows the relationship between the S meter and the CN ratio in consideration of the influence of the amplifier gain.
- the S meter is X [dB ⁇ V]
- the gain of the antenna amplifier 12 is Y [dB]
- the noise level when the antenna amplifier 12 is not applied May be considered as a noise level in the case of]] to be Z [dB ⁇ V] in terms of S meter.
- the noise level Z is a value that depends on the bandwidth of the bandpass filter 201.
- the noise level is a level (Y + Z) [dB ⁇ V] obtained by amplifying the noise level Z when the antenna amplifier 12 is not applied with the amplifier gain Y of the antenna amplifier 12.
- the CN ratio is represented by the ratio of the S meter X to the noise level (Y + Z), that is, X ⁇ (Y + Z) [dB].
- the difference between the S meter X and the CN ratio (X ⁇ (Y + Z)) is represented by (Y + Z). That is, in a normal state, the difference between the S meter and the CN ratio takes the value (Y + Z). In other words, when the difference between the S meter and the CN ratio takes a value equal to or greater than (Y + Z), since the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal, It can be determined that the CN ratio is small. That is, by detecting whether the difference between the S meter and the CN ratio is equal to or less than the threshold (Y + Z) or exceeds the threshold (Y + Z), the bandwidth of the bandpass filter 201 is narrower than the occupied bandwidth of the input signal. It can be determined whether or not.
- the CN ratio can be calculated as X ⁇ (Y + Z), which is 10 [dB], and the difference between the S meter X and the CN ratio is 20 [dB]. That is, even if it is instantaneous, when the CN ratio is lower than 10 [dB] (that is, when the difference between the S meter and the CN ratio exceeds 20 [dB]), it is not a normal state. Since the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal, it can be determined that the CN ratio is small.
- the bandwidth of the bandpass filter 201 is greater than the occupied bandwidth of the input signal. It can be determined whether the state is narrow.
- the determination unit 301 calculates the difference between the S meter and the CN ratio, and determines whether the band of the band pass filter 201 is based on whether the difference is within the range assumed by the amplifier gain of the antenna amplifier 12. It is determined whether or not the width is smaller than the occupied bandwidth of the input signal. That is, the determination unit 301 determines that the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal when the difference between the S meter and the CN ratio exceeds a predetermined threshold.
- FIG. 15 shows a comparison result between the difference between the CN ratio and the S meter and the threshold value in the determination unit 301 (that is, a determination result as to whether or not the difference is within an assumed range) and a comparison result.
- the output of the based switch 302 is shown.
- the determination unit 301 determines that the bandwidth of the band pass filter 201 is not narrower than the occupied bandwidth of the input signal when the difference between the S meter and the CN ratio is within the assumed range.
- the switch 302 outputs the CN ratio to the audio signal processing unit 18. That is, the switch 302 outputs the CN ratio when the difference between the S meter and the CN ratio is equal to or less than the threshold (Case 3).
- the determination unit 301 determines that the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal. In this case, the switch 302 outputs the S meter to the audio signal processing unit 18. That is, when the difference between the S meter and the CN ratio is greater than the threshold, the switch 302 outputs the S meter (Case 4).
- the determination unit 301 compares the S meter and the CN ratio as shown in FIG. 15, a value obtained by adding a margin considering time variation to the difference between the S meter and the CN ratio is assumed. What is necessary is just to determine whether it is in the range. That is, in FIG. 14, the determination unit 301 may determine whether the difference between the S meter and the CN ratio is within the range of ⁇ (Y + Z) + margin ⁇ . That is, the threshold value used for determination by the determination unit 301 may be ⁇ (Y + Z) + margin ⁇ .
- the margin can be determined to be, for example, 5 [dB] in consideration of the time variation of the S meter.
- the CN ratio detection circuit 102 determines whether or not the bandwidth of the bandpass filter 201 is narrower than the occupied bandwidth of the input signal. When the bandwidth of the band pass filter 201 is not narrower than the occupied bandwidth of the input signal, the CN ratio detection circuit 102 outputs the CN ratio to the audio signal processing unit 18 as in the first embodiment. To do. On the other hand, the CN ratio detection circuit 102 outputs an S meter to the audio signal processing unit 18 when the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal.
- the CN ratio detection circuit 102 can detect a state where the bandwidth of the bandpass filter 201 is narrower than the occupied bandwidth of the input signal. It is possible to provide the audio signal processing unit 18 with a value (a value used for the audio signal processing operation) suitable for the detected state.
- FIG. FIG. 16 is a block diagram illustrating a configuration of a wireless receiver 300 a that controls the bandwidth of the bandpass filter 201 using the determination result in the determination unit 301.
- the same components as those in FIG. 10 are denoted by the same reference numerals, and detailed description thereof is omitted.
- the difference between the wireless receiver 300a and the wireless receiver 300 (FIG. 10) is that the determination result of the determination unit 301 is also output to the band pass filter 201.
- the bandpass filter 201 increases the bandwidth of the pass filter to be used. Set. By doing so, it can be avoided that the bandwidth of the band-pass filter 201 becomes narrower than the occupied bandwidth of the input signal. That is, in the wireless receiver 300a, it is possible to avoid the state where the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal, and to appropriately perform the audio signal processing using the CN ratio. Thereby, it is possible to improve sound quality distortion that deteriorates in the wireless receiver 300a when the bandwidth of the band-pass filter 201 is narrower than the occupied bandwidth of the input signal.
- the determination unit 301 determines whether or not the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal based on the difference between the S meter and the CN ratio. explained. However, the determination unit 301 may determine whether or not the bandwidth of the band pass filter 201 is narrower than the occupied bandwidth of the input signal based on the CN ratio value. For example, in FIG. 14, the determination unit 301 may determine that the CN ratio is in a normal state if the CN ratio is equal to or greater than the ratio of the S meter X and the noise level (Y + Z), that is, X ⁇ (Y + Z). On the other hand, in FIG.
- the bandwidth of the bandpass filter 201 is the input signal. It may be determined that the state is narrower than the occupied bandwidth. Further, as described above, the threshold used for determination by the determination unit 301 may be ⁇ X ⁇ (Y + Z) + margin ⁇ in consideration of the temporal variation of the CN ratio.
- FIG. 17 is a block diagram showing a configuration of radio receiver 400 according to the present embodiment.
- the same components as those in the first embodiment (FIG. 4) are denoted by the same reference numerals, and detailed description thereof is omitted.
- a blend unit 401 is provided in the CN ratio detection circuit 102.
- the blend unit 401 outputs the input voltage (here, S meter as in the first embodiment) output from the voltage detection unit 103 and the CN ratio calculation unit 106. CN ratio is input. Also, the blending unit 401 holds in advance a CN ratio application upper limit value (CNR_lim) and a threshold value (S_lim) indicating an S meter application lower limit value.
- CNR_lim CN ratio application upper limit value
- S_lim threshold value
- the blend unit 401 selects or interpolates the CN ratio and S meter according to the input CN ratio and S meter value, and outputs the obtained blend value to the audio signal processing unit 18.
- the blending unit 401 outputs the CN ratio as a blend value to the audio signal processing unit 18 when the input CN ratio is equal to or less than CNR_lim.
- the blend unit 401 outputs the S meter as a blend value to the audio signal processing unit 18.
- the blend unit 401 outputs the interpolated value of the CN ratio and the S meter as a blend value to the audio signal processing unit 18. .
- the audio signal processing unit 18 performs various types of audio signal processing using the blend value input from the blending unit 401.
- the upper limit of the dynamic range of the CN ratio is determined by the calculation accuracy of the time variation calculation unit 105.
- the value of the CN ratio is increased, a digit loss occurs and the calculation accuracy is lowered. Therefore, the CN ratio tends to be saturated at a medium electric field (approximately 40 dB ⁇ V) or more.
- FIG. 18 shows the CN ratio including the medium electric field (40 dB ⁇ V) or more and the measurement result of the S meter. Note that FIG. 18 shows characteristics when an antenna amplifier is applied.
- the S meter shows a linear characteristic.
- the CN ratio has a linear characteristic at an input level of 30 dB ⁇ V or less, but at an input level of 40 to 70 dB ⁇ V, it is saturated at a CN ratio of about 40 dB.
- the CN ratio detected by the CN ratio detection circuit 102 has a problem that the dynamic range is narrower than that of the S meter. For this reason, the CN ratio detected by the CN ratio detection circuit 102 is not suitable for use as an index of audio signal processing at a medium electric field or higher.
- the audio signal processing unit 18 needs to switch processing according to the input level, and the control of the audio signal processing becomes complicated. .
- the blend unit 401 blends both according to the input CN ratio and the S meter value, and outputs the obtained blend value. That is, the blending unit 401 unifies the input CN ratio and S meter numerical values as a blending value so that the control of the audio signal processing unit 18 is not complicated.
- the blending unit 401 sets an application meter lower limit S_lim of the S meter and an application upper limit CNR_lim of the CN ratio. The blending unit 401 then determines whether (1) the S meter is greater than or equal to S_lim, (2) the CN ratio is less than or equal to CNR_lim, and (3) the above (1), ( It is determined whether any of 2) is applicable.
- the blending unit 401 outputs the S meter to the audio signal processing unit 18.
- the blending unit 401 outputs the CN ratio to the audio signal processing unit 18.
- the blending unit 401 calculates the internal division ratio k.
- FIG. 18 shows an example of a blend value that is an output of the blend unit 401.
- the CN ratio detection circuit 102 includes the blending unit 401 that blends the input S meter and the CN ratio into one value (blend value).
- the blending unit 401 outputs the CN ratio when the CN ratio is equal to or less than the application upper limit value CNR_lim, and when the CN ratio is greater than the application upper limit value CNR_lim, the blending unit 401 outputs the input voltage (S meter) or the CN ratio and the S Outputs the interpolation value with the meter.
- radio receiver 400 can perform audio signal processing in a low electric field according to an accurate CN ratio as in the first embodiment.
- the wireless receiver 400 can avoid the use of only the CN ratio whose accuracy has deteriorated even in a medium electric field or more where the accuracy of the CN ratio deteriorates, and can perform appropriate audio signal processing according to the S meter or the interpolation value. Become.
- the input S meter and CN ratio are blended into one value as an index for the audio signal processing unit 18 in the blending unit 401, the control of the audio signal processing unit 18 can be avoided from becoming complicated.
- the wireless receiver 400 can smoothly perform audio signal processing of a medium electric field or higher and audio signal processing of a weak electric field.
- the blending method of S meter and CN ratio is not limited to the method mentioned above.
- the blending unit 401 may have a hysteresis by separating a threshold for switching from the CN ratio to the S meter and a threshold for switching from the S meter to the CN ratio. In this case, the time change of the blend value can be stabilized.
- a radio receiver that receives an analog FM radio signal has been described.
- a digital modulation method (FSK (frequency shift keying), PSK (phase shift keying) with constant amplitude is used. It is also applicable to a wireless receiver that receives a wireless signal of)).
- the above embodiments may be arbitrarily combined.
- the time variation width of the input voltage (S meter) is corrected in the same manner as in the second embodiment, and the CN ratio is calculated using the corrected time variation width. May be.
- the present disclosure is useful as a circuit for determining the quality of a received signal in a radio signal receiver of a modulation method with a constant amplitude.
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- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Quality & Reliability (AREA)
- Electromagnetism (AREA)
- Circuits Of Receivers In General (AREA)
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Abstract
Description
次に、本開示の各実施の形態を説明する前に、本発明者が行った実験について説明する。
[無線受信機の構成]
図4は、本実施の形態に係る無線受信機の構成を示すブロック図である。なお、図4において、図1に示す無線受信機10の構成部と同一の構成部には同一の符号を付し、その説明を省略する。
受信回路101は、F/E回路15、復調部16、CN比検出回路102、音声信号処理部18から構成される。
CN比検出回路102は、電圧検出部103、平均化部104、時間変動幅計算部105、CN比計算部106からなる。
以上のようにして構成されたCN比検出回路102の特性について説明する。
[無線受信機の構成]
図6は、本実施の形態に係る無線受信機200の構成を示すブロック図である。なお、図6において、実施の形態1(図4)と同様の構成については同一符号を付し、その詳細な説明は省略する。
時間変動幅補正部202には、帯域通過フィルタ201の帯域幅BPF_bwに対応する雑音レベル基準値N_lvが予め設定されている。
図10は、本実施の形態に係る無線受信機300の構成を示すブロック図である。なお、図10において、実施の形態1(図4)又は実施の形態2(図6)と同様の構成については同一符号を付し、その詳細な説明は省略する。
次に、判定部301及びスイッチ302における出力切替処理の詳細について説明する。
次に、判定部301において、帯域通過フィルタ201の帯域幅が入力信号の占有帯域幅より狭い状態であるか否かを判定する方法について説明する。
[無線受信機の構成]
図17は、本実施の形態に係る無線受信機400の構成を示すブロック図である。なお、図17において、実施の形態1(図4)と同様の構成については同一符号を付し、その詳細な説明は省略する。
以下、ブレンド部401におけるブレンド処理の詳細について説明する。
11 アンテナ
12,23 アンテナアンプ
14 スピーカ
15 フロントエンド回路(F/E回路)
16 復調部
17 Sメータ検出部
18 音声信号処理部
21 標準信号源
22 アンテナダミー回路
13,24,101 受信回路
102 CN比検出回路
103 電圧検出部
104 平均化部
105 時間変動幅計算部
106 CN比計算部
201 帯域通過フィルタ
202 時間変動幅補正部
301 判定部
302 スイッチ
401 ブレンド部
Claims (8)
- 信号の入力電圧を測定する電圧検出部と、
所定時間内における前記入力電圧の平均値を算出する平均化部と、
前記所定時間内における前記入力電圧の時間変動幅を算出する時間変動幅計算部と、
前記平均値及び前記時間変動幅を用いて、前記信号のCN比を算出するCN比計算部と、を備えた、
CN比検出回路。 - 前記電圧検出部は、帯域通過フィルタの出力端に電気的に接続されて、前記帯域通過フィルタの出力信号の電圧を前記入力電圧として測定し、
前記CN比検出回路は、前記時間変動幅の値が、前記帯域通過フィルタの帯域幅に応じて設定される基準値より低い場合に前記時間変動幅の値を前記基準値に補正する時間変動幅補正部を更に備え、
前記CN比計算部は、前記時間変動幅の値が前記基準値より低い場合には、前記平均値、及び、前記時間変動幅補正部で補正された時間変動幅の値を用いて、前記CN比を算出する、
請求項1に記載のCN比検出回路。 - 前記電圧検出部は、帯域通過フィルタの出力端に電気的に接続されて、前記帯域通過フィルタの出力信号の電圧を前記入力電圧として測定し、
前記CN比検出回路は、
前記入力電圧と前記CN比とを比較して、前記帯域通過フィルタの帯域幅が前記信号の占有帯域幅より狭い状態であるか否かを判定する判定部と、
前記判定部において前記帯域通過フィルタの帯域幅が前記信号の占有帯域幅より狭い状態であると判定された場合に前記入力電圧を出力し、前記判定部において前記帯域通過フィルタの帯域幅が前記信号の占有帯域幅より狭い状態ではないと判定された場合に前記CN比を出力するスイッチと、を更に備えた、
請求項1に記載のCN比検出回路。 - 前記入力電圧と前記CN比との差分が閾値以下であるか否かを判定する判定部と、
前記差分が前記閾値より大きい場合、前記入力電圧を出力し、前記差分が前記閾値以下の場合、前記CN比を出力するスイッチを更に備えた、
請求項1に記載のCN比検出回路。 - 前記CN比が第1閾値以下の場合には当該CN比を出力し、前記CN比が前記第1閾値より大きい場合には、前記入力電圧、又は、前記CN比と前記入力電圧との補間値を出力するブレンド部を更に備えた、
請求項1に記載のCN比検出回路。 - 前記ブレンド部は、前記CN比が前記第1閾値より大きく、かつ、前記入力電圧が前記第1閾値より大きい第2閾値以上の場合には当該入力電圧を出力し、前記CN比が前記第1閾値より大きく、かつ、前記入力電圧が前記第2閾値未満の場合には前記補間値を出力する、
請求項5に記載のCN比検出回路。 - 前記CN比計算部は、前記平均値の平方と、前記時間変動幅の平方と定数の積との比を前記CN比として算出する、
請求項1に記載のCN比検出回路。 - 受信信号を復調する復調部と、
前記受信信号のCN比を算出するCN比検出回路と、
前記CN比に従って、前記復調後の受信信号に対する音声信号処理を行う音声信号処理部と、を備え、
前記CN比検出回路は、
前記受信信号の入力電圧を測定する電圧検出部と、
所定時間内における前記入力電圧の平均値を算出する平均化部と、
前記所定時間内における前記入力電圧の時間変動幅を算出する時間変動幅計算部と、
前記平均値及び前記時間変動幅を用いて、前記CN比を算出するCN比計算部と、を有する、
受信回路。
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EP16742997.6A EP3252956A4 (en) | 2015-01-28 | 2016-01-28 | C/n ratio detection circuit and signal receiving circuit |
US15/542,410 US10393787B2 (en) | 2015-01-28 | 2016-01-28 | C/N ratio detection circuit and signal receiving circuit |
CN201680006895.7A CN107210768B (zh) | 2015-01-28 | 2016-01-28 | 载噪比检测电路以及接收电路 |
JP2016571869A JP6650580B2 (ja) | 2015-01-28 | 2016-01-28 | Cn比検出回路及び受信回路 |
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JP2001108720A (ja) * | 1999-10-05 | 2001-04-20 | Hitachi Kokusai Electric Inc | Cn測定方法および測定回路 |
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JPH0563593A (ja) | 1991-08-29 | 1993-03-12 | Toshiba Corp | シグナルレベル表示装置 |
US5703954A (en) | 1996-02-20 | 1997-12-30 | Usa Digital Radio Partners, L.P. | Method and apparatus for improving the quality of AM compatible digital broadcast system signals in the presence of distortion |
JP3625760B2 (ja) | 2000-10-13 | 2005-03-02 | アンリツ株式会社 | 変調誤差比測定装置 |
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US8831546B2 (en) * | 2011-11-07 | 2014-09-09 | Ibiquity Digital Corporation | MRC antenna diversity for FM IBOC digital signals |
CN103323702B (zh) * | 2013-05-28 | 2016-04-13 | 西南交通大学 | 复合电能质量扰动信号识别方法 |
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JPH09261147A (ja) * | 1996-03-19 | 1997-10-03 | Nec Corp | 受信c/n検出方式および検出装置と送信電力制御方式 |
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