CN211348423U - High-frequency signal measuring device - Google Patents
High-frequency signal measuring device Download PDFInfo
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- CN211348423U CN211348423U CN201922119814.8U CN201922119814U CN211348423U CN 211348423 U CN211348423 U CN 211348423U CN 201922119814 U CN201922119814 U CN 201922119814U CN 211348423 U CN211348423 U CN 211348423U
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Abstract
The utility model provides a high frequency signal measuring device, include: the device comprises a mixer, a programmable attenuator, a phase-locked loop frequency synthesizer, a switched capacitor filter, a comparator, a voltage measuring module, an analog-to-digital converter, a microprocessor and a display screen. The utility model discloses a phase-locked loop frequency synthesizer is connected program controlled attenuator again and is connected with the mixer as the local oscillator signal source after, and this modular structure is when handling input signal, and the accurate frequency jitter that does not have of mixing output signal frequency can measure the frequency and the amplitude of the signal of awaiting measuring fast accurately through follow-up module processing.
Description
The technical field is as follows:
the utility model relates to a signal measurement field especially relates to a high frequency signal measuring device.
Background art:
in the field of signal measurement, the frequency and the amplitude of a signal are generally required to be measured, and related equipment with a spectrum analyzer function is developed; however, the challenge of various new technologies using computers as the core at present puts requirements on digitization, high precision, multiple functions and the like on high-frequency signal measuring devices. In the current application, for the frequency analysis of low-frequency signals, an FFT analysis method is mostly adopted, namely, a time domain signal is subjected to fast Fourier transform, and the time domain signal is converted into a frequency domain signal for analysis, and the method is only suitable for measuring the low-frequency signals; for higher frequency signals, a spectrum analyzer using a tunable band-pass filter is generally used, but the requirements on hardware equipment are high, and the measurement accuracy is difficult to meet the actual production requirements.
The utility model has the following contents:
to the problem that the background art exists, the utility model provides a can measure measuring device of higher frequency input signal frequency and range fast high-efficient and higher precision ground. The signal to be measured is input into the system, and the frequency and the amplitude of each frequency point are displayed by a display screen of the system.
In order to realize the technical problem, the utility model adopts the following technical scheme:
a high frequency signal measuring apparatus comprising: the device comprises a frequency mixer, a programmable attenuator, a phase-locked loop frequency synthesizer, a switched capacitor filter, a comparator, a voltage measurement module, an analog-to-digital converter, a microprocessor and a display screen;
the frequency mixer is connected with the programmable attenuator in a wired mode; the programmable attenuator is connected with the phase-locked loop frequency synthesizer in a wired mode; the frequency mixer is connected with the switched capacitor filter in a wired mode; the switched capacitor filter, the voltage measuring module, the analog-to-digital converter and the microprocessor are sequentially connected in series in a wired mode; the switched capacitor filter, the comparator and the microprocessor are sequentially connected in series in a wired mode; the microprocessor is connected with the phase-locked loop frequency synthesizer in a wired mode; the microprocessor is connected with the programmable attenuator in a wired mode; the microprocessor is connected with the display screen in a wired mode.
The input end of the frequency mixer is used for accessing a signal to be detected, the phase-locked loop frequency synthesizer is used for generating a high-frequency local oscillation signal, the generated local oscillation signal is input into the programmable attenuator to control the amplitude of the local oscillation signal, the local oscillation signal is accessed into the frequency mixer from the output of the programmable attenuator to be mixed with the signal to be detected, the output of the frequency mixer is accessed into the switched capacitor filter to filter out the high-frequency signal, the filtered alternating current local oscillation signal is respectively input into the voltage measuring module and the comparator, the voltage measuring module converts the filtered alternating current local oscillation signal into a direct current analog signal, and the input comparator converts the filtered alternating current local oscillation signal into a square wave signal; the output of the voltage measurement module is connected with the analog-to-digital converter to obtain a digital signal, a direct current analog signal obtained by the voltage measurement module is converted into a direct current digital signal, and then the direct current digital signal is input into the microprocessor to acquire the value of the direct current digital signal so as to obtain the effective value of the voltage; the output of the comparator is connected with the input of the microprocessor, and the frequency of the square wave signal output by the comparator is measured, so that the frequency of the filtered alternating current local oscillation signal output by the switched capacitor filter is measured; the microprocessor controls the frequency of the local oscillation signal through the phase-locked loop frequency synthesizer, and the microprocessor controls the amplitude of the local oscillation signal through the program-controlled attenuator.
Compared with the prior art, the utility model discloses a phase-locked loop frequency synthesizer is connected program controlled attenuator again and is connected with the mixer as the local oscillator signal source after, and this modular structure is when handling input signal, and the accurate frequency jitter of mixing output signal frequency can measure the frequency and the amplitude of the signal that awaits measuring fast accurately through follow-up module processing.
Description of the drawings:
FIG. 1: a system overall block diagram;
FIG. 2: a mixer circuit design schematic;
FIG. 3: the design schematic diagram of the phase-locked loop frequency synthesizer and the programmable attenuator circuit;
FIG. 4: a switched capacitor filter circuit design schematic;
FIG. 5: a comparator circuit design schematic;
FIG. 6: a voltage measurement module design schematic diagram;
FIG. 7: the analog-digital converter module circuit design schematic diagram.
The specific implementation mode is as follows:
to facilitate understanding and practice of the invention for those skilled in the art, the invention is described in further detail below with reference to the accompanying drawings, it being understood that the embodiments described herein are merely illustrative and explanatory of the invention and are not restrictive thereof.
The system block diagram of the present invention is shown in fig. 1. The utility model discloses embodiment's technical scheme is a high frequency signal measuring device, include: the device comprises a frequency mixer, a programmable attenuator, a phase-locked loop frequency synthesizer, a switched capacitor filter, a comparator, a voltage measurement module, an analog-to-digital converter, a microprocessor and a display screen;
the frequency mixer is connected with the programmable attenuator in a wired mode; the programmable attenuator is connected with the phase-locked loop frequency synthesizer in a wired mode; the frequency mixer is connected with the switched capacitor filter in a wired mode; the switched capacitor filter, the voltage measuring module, the analog-to-digital converter and the microprocessor are sequentially connected in series in a wired mode; the switched capacitor filter, the comparator and the microprocessor are sequentially connected in series in a wired mode; the microprocessor is connected with the phase-locked loop frequency synthesizer in a wired mode; the microprocessor is connected with the programmable attenuator in a wired mode; the microprocessor is connected with the display screen in a wired mode.
The principle of the mixer is to multiply two paths of input signals to obtain a sum frequency signal and a difference frequency signal. The frequency mixing is a linear moving process of frequency spectrum, and the signal to be measured can be moved to a low frequency in a frequency mixing mode, so that the processing is convenient. In the system, the difference frequency signal is a low-frequency signal, can be converted into a digital signal through an analog-to-digital converter and then input into the FPGA, and the amplitude and frequency information of the digital signal are calculated, so that the frequency spectrum of the signal to be measured is obtained. The mixer in the system is realized by adopting a four-quadrant analog multiplier AD835 with broadband, high speed and voltage output of ADI company. Two high-frequency signals of 80 MHz-110 MHz are input at the IN1 and IN2 ends, wherein the input signal to be tested is connected with the IN1 pin of the chip, and the sum-frequency and difference-frequency signals are output at the No. 13 pin after being multiplied IN the mixer, and the specific circuit is shown IN figure 2.
The phase-locked loop frequency synthesizer module is connected to an IN2 input port of the frequency mixer, the function of a local oscillation signal source is realized by adopting an integrated phase-locked loop chip ADF4351, and the locking time can be controlled to be less than 1ms by reasonably designing a loop filter. The program-controlled attenuator is used for realizing amplitude control, amplitude control is carried out by adopting the program-controlled attenuator DAT-31R5-SP +, and a local oscillation signal of 10 mV-100 mV is obtained. The local oscillator signal circuit is shown in fig. 3. The utility model provides a phase-locked loop is a phase feedback automatic control system. Its function is to synchronize the phase difference of the clock on the circuit and the external reference signal. It consists of three basic components: a Phase Detector (PD), a loop filter (LPF) and a Voltage Controlled Oscillator (VCO). The working principle of the phase-locked loop is as follows: the output of the voltage-controlled oscillator is collected, divided and simultaneously input with a reference signal into the phase discriminator, the phase discriminator outputs a direct current pulse voltage to control the VCO by comparing the phase difference of the two signals, so that the frequency of the VCO is changed, and the output of the VCO can be stabilized at a certain expected value after a short time. The utility model discloses the output of well system test phase-locked loop is not standard sinusoidal signal, consequently adds a seven orders passive Butterworth wave filter that cutoff frequency is 110MHz behind programmed attenuator DAT-31R5-SP + for filter out high frequency noise signal, can obtain a standard sinusoidal local oscillator signal.
The switched capacitor filter is designed by a MAX297 chip, the input end of the switched capacitor filter is connected to a No. 5 output pin of the mixer, and the switched capacitor filter is used for filtering high-frequency signals output by the mixer to obtain low-frequency signals obtained by linear frequency shifting. The utility model discloses in, switched capacitor filter's performance is the important factor of influence frequency spectrum test, if switched capacitor filter's passband is uneven, so under the unchangeable circumstances of resolution ratio, the amplitude of surveying probably has great error. If the switched capacitor filter transition band is not sharp, a single frequency signal may be falsely detected as two frequencies. The system utilizes a MAX297 chip to design a 2-order Butterworth low-pass filter with the cut-off frequency of 100kHz and an 8-order elliptic filter with the cut-off frequency of 37.5 kHz: the 2 nd order Butterworth filter is designed by an internal integrated operational amplifier and is used for filtering high-frequency clutter and sum frequency signals, and the 8 th order elliptic filter is obtained by utilizing an internal switch capacitor. Tests show that the signal of 37.5kHz passes through the filter without attenuation, and the signal is attenuated by 60dB at 50kHz, so that the requirements are met. The filter circuit is shown in figure 4.
The chip used by the comparator is LM311 of TI company, the circuit converts the input sinusoidal signal into square wave output, if the input signal is larger than the voltage threshold value, the comparator outputs high level, if the input signal is lower than the threshold value, the comparator outputs low level, therefore, the comparator can be used for waveform conversion and frequency measurement. The LM311 comparator is added with a hysteresis circuit to eliminate high-frequency oscillation, and the low-frequency sinusoidal signal obtained by mixing the input signal has good response effect. In the system, the output of the comparator is connected to a microprocessor, and the frequency of the mixed intermediate frequency signal is measured.
The voltage measuring module adopts an integrated chip AD637 of the company AD, which can convert an alternating current signal into a corresponding direct current level for output and can calculate effective values of various complex waveforms. The measurable input signal effective value can be up to 7V, and for the signal of 1VRMS, the 3dB bandwidth is 8MHz, which is suitable for the system to measure the signal amplitude after mixing.
The core of the analog-to-digital converter is ADS805 of TI company, and the module is connected behind the voltage measurement module and used for sampling the obtained direct current effective value signal and inputting the sampled direct current effective value signal into an FPGA (field programmable gate array) and calculating an amplitude value. In order to increase the input range of signals, a fully differential chip THS4151 is adopted for buffer amplification. Analog to digital converter see fig. 7.
The microprocessor is a control core of the whole system, the microprocessor adopts an FPGA, and a capacitive display screen is used as a human-computer interaction interface. The outputs of the comparator and the analog-to-digital converter are connected with the microprocessor, the frequency and the amplitude of the intermediate frequency after frequency mixing are calculated, the preset values of the local oscillator amplitude and the frequency are input through the display screen, and the measured spectrogram is displayed through the display screen. The functions of the programmable gate array in the system mainly comprise phase-locked loop frequency sweep stepping control, analog-to-digital converter control, comparator output frequency measurement and interactive interface reading and writing.
The utility model discloses based on the heterodyne principle, realized a high frequency signal measurement system based on phase-locked loop. The local oscillation signal of the system is realized by adopting an analog phase-locked loop, the accurate high-frequency scanning frequency is quickly obtained by controlling the ADF4351, and the output amplitude is adjustable in a stepping mode by controlling the programmable attenuator. For high-frequency signals, the system can accurately test frequency components and amplitudes, displays frequency spectrums on a screen, and can accurately position and count stray frequencies smaller than 2% of main frequency. In a word, the system realizes the established and additional requirements of the measurement system through reasonable design, and has certain index expansion. The whole system works stably and has good human-computer interaction.
The following describes the embodiments of the present invention with reference to fig. 1 to 7:
the input end of the frequency mixer is used for accessing a high-frequency signal to be detected, the phase-locked loop frequency synthesizer is used for generating a high-frequency local oscillation signal, the generated local oscillation signal is input into the programmable attenuator to control the amplitude of the local oscillation signal, the local oscillation signal is accessed into the frequency mixer from the output of the programmable attenuator to be mixed with the signal to be detected, the output of the frequency mixer is accessed into the switched capacitor filter to filter out the high-frequency signal, the filtered alternating current local oscillation signal is divided into two paths and is respectively input into the voltage measuring module and the comparator, the voltage measuring module converts the filtered alternating current local oscillation signal into a direct current analog signal, and the comparator converts the filtered alternating current local oscillation signal into a square wave signal; the output of the voltage measurement module is connected with the analog-to-digital converter to obtain a digital signal, a direct current analog signal obtained by the voltage measurement module is converted into a direct current digital signal, and then the direct current digital signal is input into the microprocessor to acquire the value of the direct current digital signal so as to obtain the effective value of the voltage; the output of the comparator is connected with the input of the microprocessor, and the frequency of the square wave signal output by the comparator is measured, so that the frequency of the filtered alternating current local oscillation signal output by the switched capacitor filter is measured; the microprocessor controls the frequency of the local oscillation signal through the phase-locked loop frequency synthesizer, and the microprocessor controls the amplitude of the local oscillation signal through the program-controlled attenuator.
Although the present description uses terms such as microprocessor, mixer, phase-locked loop frequency synthesizer, switched capacitor filter, comparator, voltage measurement module, analog-to-digital converter, display screen, etc., more generally, the possibility of using other terms is not excluded. These terms are used merely to more conveniently describe the nature of the invention and should not be construed as imposing any additional limitations thereon which would depart from the spirit of the invention.
It should be understood that parts of the specification not set forth in detail are well within the prior art.
It should be understood that the above description of the preferred embodiments is given in some detail, and not as a limitation to the scope of the invention, and that various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the invention as defined by the appended claims.
Claims (2)
1. A high-frequency signal measuring apparatus, comprising: the device comprises a frequency mixer, a programmable attenuator, a phase-locked loop frequency synthesizer, a switched capacitor filter, a comparator, a voltage measurement module, an analog-to-digital converter, a microprocessor and a display screen;
the frequency mixer is connected with the programmable attenuator in a wired mode; the programmable attenuator is connected with the phase-locked loop frequency synthesizer in a wired mode; the frequency mixer is connected with the switched capacitor filter in a wired mode; the switched capacitor filter, the voltage measuring module, the analog-to-digital converter and the microprocessor are sequentially connected in series in a wired mode; the switched capacitor filter, the comparator and the microprocessor are sequentially connected in series in a wired mode; the microprocessor is connected with the phase-locked loop frequency synthesizer in a wired mode; the microprocessor is connected with the programmable attenuator in a wired mode; the microprocessor is connected with the display screen in a wired mode.
2. The high-frequency signal measuring apparatus according to claim 1, characterized in that:
the input end of the frequency mixer is used for accessing a signal to be detected, the phase-locked loop frequency synthesizer is used for generating a high-frequency local oscillation signal, the generated local oscillation signal is input into the programmable attenuator to control the amplitude of the local oscillation signal, the local oscillation signal is accessed into the frequency mixer from the output of the programmable attenuator to be mixed with the signal to be detected, the output of the frequency mixer is accessed into the switched capacitor filter to filter out the high-frequency signal, the filtered alternating current local oscillation signal is respectively input into the voltage measuring module and the comparator, the voltage measuring module converts the filtered alternating current local oscillation signal into a direct current analog signal, and the input comparator converts the filtered alternating current local oscillation signal into a square wave signal; the output of the voltage measurement module is connected with the analog-to-digital converter to obtain a digital signal, a direct current analog signal obtained by the voltage measurement module is converted into a direct current digital signal, and then the direct current digital signal is input into the microprocessor to acquire the value of the direct current digital signal so as to obtain the effective value of the voltage; the output of the comparator is connected with the input of the microprocessor, and the frequency of the square wave signal output by the comparator is measured, so that the frequency of the filtered alternating current local oscillation signal output by the switched capacitor filter is measured; the microprocessor controls the frequency of the local oscillation signal through the phase-locked loop frequency synthesizer, and the microprocessor controls the amplitude of the local oscillation signal through the program-controlled attenuator.
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| CN201922119814.8U CN211348423U (en) | 2019-11-29 | 2019-11-29 | High-frequency signal measuring device |
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| CN201922119814.8U CN211348423U (en) | 2019-11-29 | 2019-11-29 | High-frequency signal measuring device |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112491414A (en) * | 2020-10-23 | 2021-03-12 | 北京无线电测量研究所 | Locking indicating circuit for monitoring locking state of phase-locked loop circuit in real time |
| CN112710897A (en) * | 2020-12-07 | 2021-04-27 | 广东电网有限责任公司韶关供电局 | Frequency measuring circuit |
| CN113193812A (en) * | 2021-05-08 | 2021-07-30 | 中国北方车辆研究所 | Electromagnetic compatibility filtering system of variable frequency driving motor |
| CN113589035A (en) * | 2021-09-11 | 2021-11-02 | 北京芯同汇科技有限公司 | Frequency measuring device and measuring method |
| CN113589037A (en) * | 2021-09-11 | 2021-11-02 | 北京芯同汇科技有限公司 | Frequency spectrum detection device and detection method |
-
2019
- 2019-11-29 CN CN201922119814.8U patent/CN211348423U/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112491414A (en) * | 2020-10-23 | 2021-03-12 | 北京无线电测量研究所 | Locking indicating circuit for monitoring locking state of phase-locked loop circuit in real time |
| CN112710897A (en) * | 2020-12-07 | 2021-04-27 | 广东电网有限责任公司韶关供电局 | Frequency measuring circuit |
| CN113193812A (en) * | 2021-05-08 | 2021-07-30 | 中国北方车辆研究所 | Electromagnetic compatibility filtering system of variable frequency driving motor |
| CN113193812B (en) * | 2021-05-08 | 2024-04-26 | 中国北方车辆研究所 | Electromagnetic compatibility filtering system of variable-frequency driving motor |
| CN113589035A (en) * | 2021-09-11 | 2021-11-02 | 北京芯同汇科技有限公司 | Frequency measuring device and measuring method |
| CN113589037A (en) * | 2021-09-11 | 2021-11-02 | 北京芯同汇科技有限公司 | Frequency spectrum detection device and detection method |
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