CN101888252A - Method and system for improving dynamic range in RF system - Google Patents

Abstract

The invention discloses a method and a system for improving a dynamic range in an RF system. In the system, an emitter, a power distributor, an amplifier and antenna are connected in turn, the antenna, a coupler, a low noise amplifier and a receiver are connected in turn, and a delay line and a vector regulator are connected between the power distributor and the coupler; the output end or input end of the power amplifier is connected with the input end of the delay line through the power distributor, and the output ends of the delay line and the vector regulator are connected with the input end of the low noise amplifier through the coupler; the power distributor is used for coupling part of carrier signals f; and the vector regulator is used for regulating the amplitudes of coupled carrier signals f and inverting the coupled carrier signals to obtain signals f1. The method and the system have the advantages that: firstly, a pre-feeding back method is used to inhibit radio frequency interference to a maximum degree; secondly, the amplitude of interference signals is lowered, the signal-to-noise ratio is improved, the dynamic range and sensitivity of a receiving system are improved; and thirdly, the structure is simple and easy to realize.

Description

A kind of method and system that improve dynamic range in the RF system

Technical field

The present invention relates generally to receive-transmit systems such as continuous wave radar, RFID, mainly is the method and system of dynamic range in a kind of RF of the raising system.

Background technology

Receive-transmit system such as continuous wave radar, RFID adopts circulator as the transmitting-receiving isolating device usually, but the circulator isolation is limited, excessive being leaked to that cause easily transmitting receives in the path, therefore, adopts the double antenna technology to reduce the leakage signal that receives in the path usually.Nonetheless, still being faced with a great technical problem in the receive-transmit system, is exactly the closely interference of barrier, for example radome.

Because continuous wave radar or rfid system all use continuous wave to transmit, and the interference f1 of closely strong reflection target is not only arranged, also include reflected signal f2, the Doppler signal f3 of other target at a distance in received signal.Because signal f1 signal amplitude is bigger, closely the reflection echo of barrier is than the low about 30dB of transmitted wave, usually than more than the high 20dB of signal f2, can make the performance of receiver reduce, be embodied in: the signal to noise ratio that 1, has reduced received signal, also correspondingly reduce the receiving sensitivity of receiver, shortened the scope of communication; 2, increase the excursion of signal, reduced the dynamic range of useful signal.3, cause saturated, the nothing gain of low noise amplifier in the receiver easily, reduce the receiver reliability even burn receiver.Reduced the detectivity of little echo signal.4, produce intermodulation signal, increased the power consumption of interference and system.

Several defectives are arranged in processing method in the past, 1, the echo-signal excursion is bigger, system need increase system signal and handle burden than the AD of long number, has increased system cost.2, adopt the low noise amplifier of high 1dB compression point, alleviated the saturation pressure of prime low noise amplifier to a certain extent, but do not solve the problem of dynamic range of signals.3, often only pay close attention to the leakage that transmits, and ignored the closely strong reflection signal of barrier.

Summary of the invention

The present invention will solve the shortcoming of above-mentioned prior art, and a kind of method and system that suppress the strong reflection echo are provided, to improve the dynamic range and the receiving sensitivity of system.The mode that the present invention cancels out each other by anti-phase power reduces the radio frequency interference of strong reflection echo in the receiving loop, thereby improves dynamic range and little Target Detection Ability of Infrared.

The present invention solves the technical scheme that its technical problem adopts: the system of dynamic range in this raising RF system comprises power divider, power amplifier, antenna, coupler, low noise amplifier, delay line, attenuator, phase shifter.Power divider is connected with power amplifier with delay line, and transmitter, power divider, power amplifier, antenna connect successively, the commutative order of its intermediate power amplifier and power divider, and reception antenna, coupler, low noise amplifier connect successively.Delay line, attenuator, phase shifter and amplifier are connected successively, and exchange sequence arbitrarily between them can be without amplifier or attenuator under suitable situation.Output or input at power amplifier are connected with the input of delay line by power divider, and delay line, vector controller output are connected with the input of low noise amplifier by coupler; Wherein power divider is used for carrier signal f is coupled out a part; Delay line, the signal f that is used for taking out postpones certain hour, and vector controller is used for the carrier signal f adjusting range that will be coupled out, the anti-phase signal-f1 that obtains; Coupler is used for echo-signal fr and the adjusted signal-f1 of vector superimposed.Input at power amplifier is connected by the input of coupler 1 with delay line 2, and the output of vector controller 2 is connected with the input of low noise amplifier by coupler 4.

The method that improves radio frequency leakage inhibition in the RF system of the present invention comprises the steps:

(1), the carrier signal f of transmitter output behind power divider, part signal power ingoing power amplifier is gone out by aerial radiation.Run into closely and obtain echo-signal behind the barrier, this echo-signal is received antenna induction, obtains signal f1, and signal f1 is the time delay of signal f, and its frequency plot is identical, its amplitude difference.

(2), receive in the path signal f1 not only arranged, also comprise the signal f2 of other frequency, f2 is that the different time of signal f postpones, out of phase moves and the stack of multipath effect etc., contains the target signature information of needs.Formed received signal fr jointly by f1 and f2.

(3), another road signal f of being coupled out of coupler 1, delayed line, attenuator, phase shifter, amplifier adjusting range and phase place, obtain one with high reject signal f1 constant amplitude, anti-phase signal f3, through coupler 2, two signal cancellations obtain the signal Fout2 approximate with echo-signal f2.

The effect that the present invention is useful is: method provided by the invention, by the coupling that will transmit, amplification, a series of method such as anti-phase, make because closely strong radio frequency interference is inhibited, thereby reduce the harmful effect that receiving system is caused, can be widely used in systems such as continuous wave radar, RFID, have a good application prospect.In sum, the present invention has the following advantages: the first, utilize the method for pre-feedback, suppressed radio frequency interference to greatest extent.The second, reduce the amplitude of interference signal, improved signal to noise ratio, improved the dynamic range and the sensitivity of receiving system.Three, simple in structure, realize easily.

Description of drawings

Fig. 1 is the theory diagram of prior art;

Fig. 2 is the theory diagram of the embodiment of the invention 1;

Fig. 3 is the theory diagram of the embodiment of the invention 2;

Fig. 4 is the theory diagram of coupler 1 of the present invention;

Fig. 5 is the theory diagram of coupler 2 of the present invention.

Embodiment

The invention will be further described below in conjunction with drawings and Examples:

Embodiment 1: Fig. 2 is a system block diagram of the present invention, and the system of dynamic range comprises transmitter, power splitter, power amplifier, antenna, coupler, low noise amplifier, receiver, delay line, phase shifter, attenuator and amplifier in this raising RF system.Transmitter, power splitter, power amplifier, antenna connect successively, and antenna, coupler, low noise amplifier connection successively are connected successively with power splitter, delay line, attenuator, phase shifter, amplifier and coupler.Power splitter is told a part of signal with transmitter power, delayed line, attenuator, phase shifter, amplifier carry out amplitude, phase place and adjust time of delay after obtain signal-f1, send into low noise amplifier in the receiver by coupler again.Most of signal of transmitter is gone out by aerial radiation after power amplifier amplifies.Signal is received antenna induction to signal f1 after running into and closely launching target reflection by force, is received the signal reflex signal f2 that also has other target that antenna receives simultaneously, i.e. fr=f1+f2.Signal f2 is the stack of other a plurality of echo signals and Doppler signal and noise signal.Delayed backward signal-f1 with transmit fr after coupler stack, obtain a signal fout who is similar to f2.

Input at power amplifier is connected with the input of delay line by power splitter, and the output of amplifier is connected with the input of low noise amplifier by coupler, and wherein power splitter is used for carrier signal f is coupled out a part; Delay line, attenuator, phase shifter and amplifier are used for carrier signal f adjusting range, phase place and the time of delay that will be coupled out, obtain signal-f1; Coupler is used for signal fr and signal-f1 stack.Compare with existing system, the present invention has added coupling circuit, vector is adjusted circuit, after coupling, vector adjustment, coupling, obtain one with strong reflection signal constant amplitude closely, anti-phase, with the signal of time-delay, after superposeing, make interference signal be inhibited.

1. transmitter among the figure is used for output and transmits, be i.e. carrier signal; 2. power splitter is used to distribute the power between the two-way.3. power amplifier is used for carrier signal is amplified to the amplitude that enough radiate; 4. antenna is used to launch carrier signal and receives echo-signal; 5. low noise amplifier is used for faint echo-signal is amplified to enough amplitudes, is used for later signal processing; 6. coupler superposes echo-signal fr and inhibit signal-f1, suppresses the carrier signal of closely strong reflection; 7. delay line is used to adjust the time difference between the two-way.8. attenuator, phase shifter and amplifier constitute vector controller, the carrier signal adjusting range that is used for being coupled out, anti-phase.

Wherein signal flow graph is as follows: the carrier signal f of transmitter output is through behind the power splitter, a part is to power amplifier, amplifying the back is gone out by aerial radiation, run into and obtain echo-signal f1 after target is closely launched in detection by force, owing to also have other reflected signal f2 in the echo-signal, form echo-signal Fr=f1+f2 jointly with signal f1.Another road signal of power splitter output, through delay line, vector controller, adjusting range, phase place, obtain one with signal f1 constant amplitude, anti-phase, with the signal of time delay-f1. through coupler, two signal cancellations, it is approximate to obtain Fout2 and f2, thereby realizes the function that radio frequency interference suppresses.

The first, as shown in Figure 1, with power splitter carrier signal is taken out a part, be used for RF and suppress, wherein power splitter adopts microstrip line directional coupler, and signal reaches 2 ends from 1 end, wherein 2,3,4 is called the end that direct transfers, isolation end and coupled end.The important parameter that wherein reflects the directional coupler characteristic is coupling coefficient and direction coefficient, and they are:

Coupling coefficient $C\left(\mathrm{dB}\right)=10\log \frac{P_1}{{\mathrm{<figure-callout\; id="4"\; label="P"\; filenames="HSA00000075630300021.png"\; state="\{\{state\}\}">P</figure-callout>}}_4}$ Direction coefficient $D\left(\mathrm{dB}\right)=10\log \frac{P_4}{{\mathrm{<figure-callout\; id="3"\; label="P"\; filenames="HSA00000075630300021.png"\; state="\{\{state\}\}">P</figure-callout>}}_3}$

Wherein, P ₁It is the input power of 1 end; P ₃And P ₄Be respectively power from 3 ends and the output of 4 ends.Coupling coefficient has reflected the size of amplitude that is coupled to the signal of port 4 by port one, and direction coefficient has characterized the direction of coupling.

The second, delay line and vector controller, the amplitude of the carrier signal that adjustment is coupled out, phase place is also passed through time delay, obtains and original signal constant amplitude, anti-phase signal with time delay.Wherein adjusting the amplitude of carrier signal, is to finish by amplifier in the vector controller and attenuator.The stock that constitutes the RF power attenuator is a resistive material, and common resistance is a kind of citation form of attenuator, and the resistance attenuator network of Xing Chenging is exactly the lumped parameter attenuator thus.Resistance material is placed into the attenuator that has just formed corresponding frequencies in the RF circuit structure of different-waveband by certain technology.The technical indicator of attenuator comprises working band, attenuation, power capacity, return loss of attenuator etc., and the power of signal input part is P1, is P2 and output gets power, and the power attenuation amount of attenuator is A (dB).If P1, P2 are with dBm (dBm) expression, then the pass between the power of two ends is

P2(dBm)＝P1(dBm)-A(dB)

Here need to design suitable attenuation.

Inverter, by 180 ° of realizations of phase shifter phase shift, its effect is to change electromagnetic phase shift.Originally, the row ripple will produce respective phase and move Δ φ=β l when passing through the transmission line of any certain-length, but sometimes for some specific needs, often require electromagnetic phase place can change within the specific limits, this just requires to utilize special phase shifter.To the basic demand of phase shifter be ripple by the time phase shift that produces can regulate, but do not wish to produce supplementary load loss.According to

As seen to change phase place, by adjusting

Value realize.

Delay line is realized by transmission line.The transmission of electromagnetic wave in media always needs certain hour, and the dielectric constant of its time of delay and medium is relevant.Usually require delay line to have that time-delay is big, loss is little.General delay line is 50 ohm of coaxial lines.

Three, with coupler two paths of signals is mixed,, suppress the carrier signal of revealing Fr and the adjusted signal of vector-f1 stack.As shown in Figure 5, the signal of 3 ends advanced certain coupling, and to port 2, the signal of anti-phase constant amplitude is offset, and made the radiofrequency signal of revealing be inhibited.

Embodiment 2, and difference from Example 1 is: what embodiment 1 adopted is the transmitting-receiving dual-antenna system, is guaranteed to receive and dispatch by antenna coupling each other and isolates, and what embodiment 2 adopted is that isolator is realized the transmitting-receiving isolation.Generally adopted similar know-why to improve system's receive-transmit isolation.

The present invention makes to be inhibited owing to closely reflecting the radio frequency interference that causes, thereby reduces the harmful effect that it causes receiving system by add delay line and vector controller in system.The method that the present invention adopts, the method by the coupling that will transmit, vector are adjusted suppresses the radio frequency interference in the receiving system, can be widely used in systems such as continuous wave radar, RFID, has a good application prospect.

It should be noted last that: above embodiment is the unrestricted technical scheme of the present invention with explanation only, although the present invention is had been described in detail with reference to the foregoing description, those of ordinary skill in the art is to be understood that: still can make amendment or be equal to replacement the present invention, and not breaking away from any modification or partial replacement of the spirit and scope of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.

Claims (3)

1. a system that improves dynamic range in the RF system comprises transmitter, power divider, power amplifier, antenna, low noise amplifier, coupler, delay line, vector controller, and vector controller comprises attenuator, amplifier and phase shifter; Transmitter, power divider, amplifier, antenna connect successively, and antenna, coupler, low noise amplifier and receiver are connected successively, are connected with delay line, vector modulator between power divider and the coupler; It is characterized in that: output or input at power amplifier are connected with the input of delay line by power divider, and delay line, vector controller output are connected with the input of low noise amplifier by coupler; Wherein power divider is used for carrier signal f is coupled out a part; Delay line, the signal f that is used for taking out postpones certain hour, and vector controller is used for the carrier signal f adjusting range that will be coupled out, the anti-phase signal-f1 that obtains; Coupler is used for echo-signal fr and the adjusted signal-f1 of vector superimposed.

2. the system that improves dynamic range in the RF system according to claim 1, it is characterized in that: the input at power amplifier is connected by the input of coupler 1 with delay line 2, and the output of vector controller 2 is connected with the input of low noise amplifier by coupler 4.

3. an employing method that improves the system of dynamic range in the RF system as claimed in claim 1 is characterized in that: comprise the steps:

(1), the carrier signal f of transmitter output is behind power divider, part signal power enters power amplifier, go out by aerial radiation, run into closely and obtain echo-signal behind the barrier, this echo-signal is received antenna induction, obtains signal f1, and signal f1 is the time delay of signal f, its frequency plot is identical, its amplitude difference;

(2), in the reception path signal f1 is arranged not only, the signal f2 that also comprises other frequency, f2 is that the different time of signal f postpones, out of phase moves and the stack of multipath effect, contains the target signature information of needs, has formed received signal fr jointly by f1 and f2;

(3), another road signal f of being coupled out of coupler 1, delayed line, attenuator, phase shifter, amplifier adjusting range and phase place, obtain one with high reject signal f1 constant amplitude, anti-phase signal f3, through coupler 2, two signal cancellations obtain the signal Fout2 approximate with echo-signal f2.

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