JP6946238B2 - Radar device and radar signal processing method - Google Patents

Description

An embodiment of the present invention relates to a pulse compression radar device and a radar signal processing method thereof.

With conventional pulse radar equipment, when the transmission output level is as high as several hundred watts to several kW or more, radar observation cannot be performed because the receiving circuit is saturated due to the wraparound of the transmitted wave during pulse transmission. There is an essential problem. In particular, solidarized weather radar using pulse compression uses pulses with a long time width of tens of μs to several hundreds of μs (long pulses), so the unobservable blind region becomes as large as tens of kilometers. There's a problem.

In order to interpolate this blind region, the current solid-state weather radar also uses observations using short pulses with a pulse width of about 0.5 μs to 1 μs. However, for the purpose of preventing mutual interference between the long pulse and the short pulse, the occupied bandwidth of the frequency is doubled by using the center frequencies of each with a shift. In addition, long-pulse observations and short-pulse observations are performed continuously, which causes problems such as an increase in observation time or a decrease in observation distance. In order to improve the harmful effects caused by the combined use of these long pulses and short pulses, it is desired to realize a solidified pulse compression radar that can be viewed only with long pulses (= can be observed even during pulse transmission).

JP-A-59-232 Japanese Unexamined Patent Publication No. 9-69803

As described above, in the conventional pulse compression radar device, since the reception circuit is saturated due to the wraparound of the transmitted wave during the transmission of the pulse and the blind region where the radar observation cannot be performed is interfered, the observation using the short pulse is also used. However, the occupied bandwidth of the frequency is doubled in order to prevent mutual interference between the long pulse and the short pulse. In addition, since long pulse observation and short pulse observation are performed continuously, there are problems such as an increase in observation time or a decrease in observation distance.

This embodiment has been made in view of the above problems, and is a pulse compression radar device capable of performing radar observation even during transmission while suppressing wraparound of the transmission signal and suppressing deterioration of the reception NF, and a radar signal processing method thereof. The purpose is to provide.

The pulse compression radar device according to one embodiment includes a transmission coupler, a reception coupler, a regulator, a power synthesizer, a first reception circuit, and a second reception circuit. In the transmission coupler, a pulse signal modulated for pulse compression is frequency-converted and coupled with an output transmission signal to acquire a transmission coupling signal, and in the reception coupler, the transmission is transmitted. signal and the received signal coupled to be received is reflected acquires reception coupling signal by observation target, in the regulator include an amplitude and phase of the transmission coupling signals to the reception coupling signal the adjusted depending around inclusive component of the transmission signal, in the power combiner, and the reception coupling signal and the transmission coupling the signal subjected to adjustment of the amplitude and phase to power combining. In the first receiving circuit, the subjected to pulse compression processing on a time to input the received coupling signal output from the power amplifier axis, and in the second receiving circuit, the receiving coupling output from said receiver combiner A signal is input and pulse compression processing is performed on the time axis. The signal level of the reception coupling signal acquired by coupling with the reception signal is higher than the signal level of the power-synthesized reception coupling signal.

The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 1st Embodiment. The figure which shows the relationship between the observation area and acquired data in 1st Embodiment. The block diagram which shows the structure of the pulse compression radar apparatus which concerns on 2nd Embodiment. The figure which shows the relationship between the observation area and acquired data in 2nd Embodiment. The block diagram which shows the specific structure of the wraparound suppression circuit in 1st or 2nd Embodiment. The block diagram which shows the structure which controls the adjustment of the amplitude and the phase of the wraparound suppression circuit in 1st Embodiment. A block diagram and a conceptual diagram showing another configuration for controlling the adjustment of the amplitude and phase of the wraparound suppression circuit according to the first embodiment. The block diagram which conceptually shows the example of the digital signal processing performed in the latter part of the 1st and 2nd embodiments. The block diagram which shows the structure of the protection circuit of the low noise power amplifier in 1st Embodiment. The block diagram which shows the structure of the protection circuit of the low noise power amplifier in 2nd Embodiment.

Hereinafter, embodiments will be described with reference to the drawings.
(First Embodiment)
FIG. 1 is a block diagram showing a configuration of a parabolic radar using a transmission / reception shared antenna as the pulse compression radar device according to the first embodiment. In FIG. 1, 100 is a transmission circuit, 200 is a first reception circuit, 300 is a second reception circuit, 400 is a wraparound suppression circuit, 500 is a circulator, and 600 is a transmission / reception shared antenna.

The transmission circuit 100 plays a role of generating a modulated pulse signal necessary for radar and amplifying it to a specified transmission frequency and transmission output. First, a pulse signal frequency-modulated by the modulation signal generator 100a is generated as a digital signal, converted from a digital signal to an analog signal by the D / A converter 100b, and then converted into an RF frequency by the frequency converter 100c. Then, the high frequency power amplifier 100d amplifies the power to the specified transmission output and outputs it as a transmission RF signal.

The transmission RF signal output from the transmission circuit 100 is transmitted from the transmission / reception shared antenna 600 via the directional coupler 400a and the circulator 500 of the wraparound suppression circuit 400 described later, and is received from the observation target received by the transmission / reception shared antenna 600. The reflected wave of the above becomes a received RF signal and is sent to the second receiving circuit 300 via the circulator 500 and the directional coupler 400e of the wraparound suppression circuit 400.

Here, the wraparound suppression circuit 400 suppresses the transmission wave in which the transmission RF signal wraps around the reception circuit through the circulator 500, and a part of the transmission RF signal output from the transmission circuit 100 by the directional coupler 400a is suppressed. It is taken out, the phase and amplitude are adjusted by the phase adjuster 400b and the amplitude adjuster 400c, and then it is sent to the power combiner 400d. On the other hand, the received RF signal is taken in, a part thereof is taken out by the directional coupler 400e, sent to the power synthesizer 400d, and combined with the phase / amplitude adjustment result of the transmitted RF signal to combine the received RF signal with the transmitted RF signal. Suppresses the wraparound component of. The output of the power synthesizer 400d is sent to the first receiving circuit 200.

The first receiving circuit 200 takes in the received RF signal, amplifies the power with the low noise power amplifier 200a, converts it into a received IF signal with the frequency converter 200b, converts it into a digital signal with the A / D converter 200c, and then converts it into a digital signal. Pulse compression is performed by the pulse compressor 200d, and the signal is output as a received output signal 1 (observation region 1). Similarly, the second receiving circuit 300 takes in the received RF signal, amplifies the power with the low noise power amplifier 300a, converts it into a received IF signal with the frequency converter 300b, and converts it into a digital signal with the A / D converter 300c. It is converted, pulse-compressed by the pulse compressor 300d, and output as a received output signal 2 (observation region 2).

In the above configuration, the processing operation of the present embodiment will be described below.
In a parabolic radar that uses a shared antenna for transmission and reception, a circulator is usually placed between the transmission circuit and the reception circuit. By the action of the circulator, the transmission signal from the transmission circuit is connected to the antenna, and the reception signal received by the antenna is received. Connected to the circuit. As a circulator, the signal flow from the transmitting circuit to the receiving circuit works in the direction of suppression, but usually only a suppression amount of about 15 dB to 30 dB can be taken. Therefore, the transmission signal and noise leak from the transmission circuit to the reception circuit via the circulator, and this wraps around the transmission to the reception circuit.

In a high-power radar with a transmission output of several hundred watts or more, it is impossible to observe the received signal during radar transmission because the reception circuit is saturated or the noise level rises due to the wraparound of the transmission signal and noise. Alternatively, the performance deteriorates. In particular, in the pulse compression radar that performs pulse width compression processing on the time axis in the receiving circuit, there is a problem that the unobservable area expands in a circular shape with the radar installation location as the center of the circle because a long pulse width signal is used. be.

Therefore, in the present embodiment, since reception is possible even during transmission of the radar transmission wave, in the first embodiment, the wraparound suppression circuit 400 is used as a circuit for suppressing the wraparound of the transmission signal included in the received signal. It is arranged.
In the wraparound suppression circuit 400, the output from the transmission circuit 100 is branched by coupling a part of the transmission signal by the directional coupler 400a. The coupled transmission signal is input to the power synthesizer 400d after adjusting the phase and amplitude level by the phase adjuster 400b and the amplitude adjuster 400c, respectively. On the other hand, on the receiving side as well, the received signal including the wraparound signal is coupled and branched by the directional coupler 400e and input to the power synthesizer 400d.

In the power synthesizer 400d, the coupling signal from the transmission and the coupling signal from the reception are power-combined. At this time, in the phase adjuster 400b and the amplitude adjuster 400c, the transmission coupling signal has the same amplitude and the phase is opposite to the phase and amplitude of the wraparound signal included in the reception coupling signal. Adjust the phase and amplitude. As a result, it is possible to suppress the transmission wraparound signal included in the reception coupling signal.

In the first embodiment, the received signal is power-amplified (200a, 300a) with low noise, frequency conversion (200b, 300b), conversion from analog signal to digital signal (200c, 300c), pulse compression (200d, Two receiving circuits for obtaining a received output signal by performing 300d) are arranged (first receiving circuit 200, second receiving circuit 300).

The first receiving circuit 200 and the second receiving circuit 300 have the same circuit configuration, but the first receiving circuit 200 is connected to the output terminal of the power synthesizer 400d, and the second receiving circuit 300 is directional. It is connected to the output terminal of the coupler 400e.
The first reception circuit 200 outputs the reception output signal 1 in which the wraparound suppression circuit 400 suppresses the transmission wraparound in order to cover a short-distance observation region that was conventionally blind during transmission.

On the other hand, in the reception circuit 300, reception observation cannot be performed during pulse transmission because it is connected via the directional coupler 400e with low loss, but the operation of the high output power amplifier 100d of the transmission circuit 100 is turned off after pulse transmission. The observable reception output signal 2 can be output when is set to.

Assuming that the length of the pulse to be transmitted is T [s] and the speed of light is c [m / s], the observation area ~ R _b [m] that is blinded by the conventional radar at the time of transmission is the following equation (1). Become.

したがって、第１受信回路２００の受信出力信号１を使って観測する領域１は、レーダの設置場所からR_bまでの近い領域、第２受信回路３００の受信出力信号２を使って観測する領域２はR_bより遠い領域とする。これにより、第２受信回路３００の受信出力信号２では送信の周り込みの影響を受けずに観測することができ、第１受信回路２００の受信出力信号１では、送信中に周り込みを抑圧して観測することができる。

Therefore, the region 1 observed using the received output signal 1 of the first receiving circuit 200 is a region _{close to R b} from the radar installation location, and the region 2 observed using the received output signal 2 of the second receiving circuit 300. Is a region farther than _{R b.} As a result, the reception output signal 2 of the second reception circuit 300 can be observed without being affected by the wraparound of transmission, and the reception output signal 1 of the first reception circuit 200 suppresses wraparound during transmission. Can be observed.

In the first embodiment, if the coupling degree of the directional _{coupler 400e on the receiving side is C cpl} [dB] and the loss of the power combiner 400d is L _comb [dB], it is input to the first receiving circuit 200. As for the received signal level, the signal level is lowered by _{C cpl} + L _{comb [dB].} However, in radar, even if the target is the same, the shorter the observation distance, the higher the reception level. Therefore, if the decrease in the signal level can be offset by the level improvement due to the shorter observation distance, there is no problem in observation.

_{The received power (Pr} ) reflected from the target and returned depends on the type of target to be observed, and is described by the radar equation below.
(i) Radar equations for discrete distribution targets

(ii)孤立型標的の場合のレーダ方程式

(ii) Radar equation for isolated targets

上記より、観測対象が雨雲のような離散分布型標的の場合は、受信電力が観測距離の２乗に反比例し、航空機のような孤立型標的の場合は、受信電力が観測距離の４乗に反比例する。

From the above, when the observation target is a discrete distribution type target such as a rain cloud, the received power is inversely proportional to the square of the observation distance, and when the observation target is an isolated target such as an aircraft, the received power is the fourth power of the observation distance. Inversely proportional.

Assuming that the maximum observation distance observed by the second receiving circuit 300 is R _max [m] and _{the difference in received power between the observation distances R max} and R _b is G [dB], the directional coupler on the receiving side By setting the coupling degree C _cpl [dB] of 400e so as to satisfy the following conditions, even in the observation region (r ≦ R _b ) in the first reception circuit 200, when the maximum observation distance R _max of the second reception circuit 300 is reached. It is possible to secure an S / N equal to or higher than the obtained S / N.

上記条件を満足することで、第１受信回路２００における観測が成立すると共に、送信の周り込み量の観点で受信側の方向性結合器４００ｅの結合度分（C_cpl）のレベルを低減することが可能となる。ちなみに最大観測距離R_maxで得られるS/Nがシステムとして必要なS/Nに対してマージンがある場合は、そのマージンの範囲で（４）式の条件よりも結合度C_cplをかさ上げすることは可能である。

By satisfying the above conditions, the observation in the first receiving circuit 200 is established, and the level of _{the coupling degree (C cpl} ) of the directional coupler 400e on the receiving side is reduced from the viewpoint of the wraparound amount of the transmission. Is possible. By the way, if the _{S / N obtained at the maximum observation distance R max} has a margin with respect to the S / N required for the system, the coupling degree C _cpl is raised in the range of the margin compared to the condition of Eq. (4). It is possible.

In the above description, the case where the transmission / reception shared antenna 600 and the circulator 500 are used is taken as an example, but in the present embodiment, whether the antennas are shared transmission / reception, separate transmission / reception, or whether a circulator is used is used. Either configuration can be applied (the same applies to the following embodiments).

FIG. 2 shows the relationship between the observation area and the acquired data in the first embodiment. _{Here, the region corresponding to R b} [m] obtained by converting the pulse transmission time (T [s]) by the speed of light is defined as the region to be observed by the reception output signal 1 of the first reception circuit 200, and R _b <. The region corresponding to r ≦ R _max is defined as the region to be observed by the received output signal 2 of the second receiving circuit 300.

In the pulse radar, even if it is an isolated target, an echo is returned with the length of the transmitted pulse length, so the echo from the target in the observation area 1 of the received output signal 1 is also 0 on the time axis. It will be observed in the range of <t ≤ 2 × T [s].
On the other hand, in the pulse compression radar, the observed echo signal is integrated by correlation processing on the time axis to accumulate the gain. Therefore, in order to obtain sufficient pulse compression gain by correlation processing, data is acquired in a form in which the observation echo from the target includes the pulse length.

The output signals of the A / D converter 200 and the A / D converter 300 before pulse compression are the received signal R1 and the received signal R2, and the data acquisition times of the received signals R1 and R2 are as follows.
Data acquisition time of received signal R1: 0 ≤ t ≤ 2 x T
Data acquisition time of received signal R2: T ≤ t ≤ R _max / c x 2 + T
By setting the data acquisition time of the received signals R1 and R2 before pulse compression as described above, a sufficient pulse compression gain can be obtained even for received signals such as echoes 1, 2, ..., N shown in FIG. It becomes possible to obtain.

(Second Embodiment)
FIG. 3 is a block diagram showing a configuration of the pulse compression radar device according to the second embodiment. In FIG. 3, the same parts as those in FIG. 1 are designated by the same reference numerals, and different parts will be described here.
In the second embodiment, the transmission circuit 100, the wraparound suppression circuit 400, and the reception circuit 200 are the same as those in the first embodiment, but the reception is one system and the reception circuit 300 is eliminated.

Further, the receiving circuit 200 is connected to the power synthesizer 400d during the transmission of the pulse, and the changeover switch 300 is arranged so that the receiving circuit 200 can be connected to the directional coupler 400e after the transmission of the pulse. In addition, termination devices 801, 802 are also connected to the switch 300 so that terminals to which the receiving circuit 200 is not connected can be terminated.

Unlike the first embodiment, in the receiving circuit 200, by switching the switch 300, observation is performed using the received output signal of the receiving circuit 200 both during and after the transmission of the pulse. Assuming that the pulse length is T [s] and the maximum observation distance is R _max [m], the equations (1) and (4) are established as in the first embodiment, and the directional coupler 400e on the receiving side is established. By setting the degree of coupling C _cpl of to satisfy the equation (4), it is possible to obtain the same effect as that of the first embodiment.

FIG. 4 shows the relationship between the observation area and the acquired data in the second embodiment.
In the present embodiment, the observation area 1 and the observation area 2 are observed by switching with the switch 700 using one system of the reception circuit 200. The receiving circuit 200 is connected to the power synthesizer 400d during the transmission of the pulse, and the receiving circuit 200 is connected to the directional coupler 400e after the pulse is transmitted.

At that time, as the data for the observation region 1, the data of the signal S1 in FIG. 4 plus the partial data (signal A) of the signal S2 with T ≦ t ≦ 2 × T is used. In the signal S1 and the signal S2, the amplitude and the phase are different due to the difference in the circuit through which the signal passes. The difference is acquired as calibration data in advance, and the signal A that reflects the calibration data is used.

FIG. 5 shows a specific example of the wraparound suppression circuit 400 according to the first and second embodiments.
The wraparound from the transmitting circuit 100 to the receiving circuits 200 and 300 may be caused by a plurality of factors such as leakage to the isolation port in the circulator 500, reflection due to a mismatch with the antenna 600, and reflection from the radome. Even if the amplitude value, phase, and delay amount of each wraparound component are different, the wraparound to the receiving circuit is performed by adding up the sum of the amplitude value, phase, and delay amount for each component and synthesizing the power. Can be canceled.

In FIG. 5, in order to deal with the case where there are a plurality of wraparound elements, a power distributor is provided on the transmission side directional coupler 400a side so that the amplitude value, phase, and delay amount of each wraparound component can be adjusted. The 400f is arranged and distributed to the N system, and the delay lines 411 to 41N, the amplitude adjusters 421 to 42N, and the phase adjusters 431 to 43N are connected in series to be connected to the power synthesizer 400d on the receiving side.

FIG. 6 shows an example of control of the amplitude adjuster and the phase adjuster in the first embodiment. In FIG. 6, the same parts as those in FIG. 1 are designated by the same reference numerals.
In the absence of echoes from the target to be observed, for example, when the antenna is terminated or the radar is facing the zenith in fine weather, the received output signal 1 of the first receiving circuit 200 in FIG. 6 is extremely low. It is desirable to be buried in the level or noise flow. If there is a signal detected during transmission, it is considered to be a wraparound signal from the transmission circuit 100 to the reception circuit 200, and this output is detected by the detection circuit 901 and the amplitude adjuster based on the detection result by the control circuit 902. By controlling the amplitude of 400c and the phase adjustment of the phase adjuster 400b, the amount of wraparound of transmission to the receiving circuit 200 can be minimized.

In the detection of the wraparound amount, by detecting the signal after pulse compression, the pulse width is narrowed even in the wraparound component, and the S / N improvement effect due to the pulse compression gain is obtained, so that the detection accuracy is improved.
In FIG. 6, a detection circuit 901 for detecting the output level and a control circuit 902 for controlling the amplitude adjuster 400c and the phase adjuster 400b in response to the result are added. FIG. 6 illustrates an example of application to the first embodiment, but the same applies to the second embodiment by connecting the detection circuit 901 and the control circuit 902 to the output of the reception circuit 200 in FIG. Can be controlled.

FIG. 7 shows another example of control of the amplitude adjuster 400c and the phase adjuster 400b in the first and second embodiments, and FIG. 7A shows the amplitude adjuster 400c and the phase adjuster 400b and the phase adjuster as in FIG. A block diagram showing a configuration including a detection circuit A01 for controlling 400b and a control circuit A02, FIG. 7B shows the input / output of the 4-terminal power combiner used in the power combiner 400d.

When a 4-terminal power synthesizer as shown in FIG. 7B is used as the power synthesizer 400d in the wraparound suppression circuit 400, the two input signals (0 ° signal A and -90 ° signal B) are in-phase combined output. By detecting the output C of the terminal, it is possible to control the amplitude adjuster 400c and the phase adjuster 400b so that the wraparound amount of the transmission is minimized.

In this circuit, the signal D, which is the reverse-phase combined output of the 4-terminal power synthesizer 400d, is connected to the receiving circuit 200, and the signal C, which is the in-phase combined output, is connected to the detection circuit A01. The more the transmission wraparound is suppressed by the power synthesizer 400d, the higher the detection level of the signal C. Therefore, by controlling the amplitude adjuster 400c and the phase adjuster 400b from the control circuit A02 so that the detection level of the detection circuit A01 becomes as high as possible, the amount of transmission wraparound input to the reception circuit 200 is minimized. can do.

FIG. 8 shows an example of digital signal processing performed in the subsequent stage of the first and second embodiments.
In radar, MTI (Moving Target Indicator) is generally used in order to suppress unnecessary waves (ground clutter) from the ground or buildings. This utilizes the fact that the velocity component of the ground clutter is close to 0, and removes the component whose velocity is near 0 to separate it from the observation target having the velocity component.

The MTI process is also effective for removing the wraparound of the transmission, and the wraparound of the transmission left after being suppressed in the first or second embodiment can be effectively removed.
As shown in FIG. 8, for the received output signal 1 (hits 1, 2, ..., N) output from the receiving circuit 200, a window function for reducing the occurrence of side lobes is set by the preprocessing unit B01. The Fourier transform unit (FFT) B02 performs Fourier transform to calculate the velocity spectrum, the velocity component near 0 [m / s] is removed or the filter is removed by the removal section B03, and the inverse Fourier transform section B04 reverses. By performing the Fourier transform, the wraparound component of the transmission can be removed. In the weather radar, the necessary weather echo is also removed by this process, so the removed part is compensated.
The details of the removal process of the ground clutter are shown in the following documents.
Appendix A-8 (2) Ground clutter removal treatment in the following documents
http://www.nilim.go.jp/lab/bcg/siryou/tnn/tnn0909pdf/ks090915.pdf

FIG. 9 shows a protection circuit of the low noise power amplifier 300a of the second receiving circuit 300 in the first embodiment.

In the first embodiment, transmission wraparound is mixed in the first receiving circuit 200 and the second receiving circuit 300 during transmission. Since the wraparound of transmission is sufficiently suppressed by the power synthesizer 400d, the received RF signal input to the first receiving circuit 200 does not reach a level that damages the low noise power amplifier 200a, but the second receiving circuit 300 There is a risk of input wraparound at a level that damages the low noise power amplifier 300a. In FIG. 9, by arranging the power limiter circuit C01 between the directional coupler 400e and the low noise power amplifier 300a, damage due to excessive input of the low noise power amplifier 300a can be prevented.

Even if the same power limiter circuit as C01 is arranged between the power synthesizer 400d and the low noise power amplifier 200a in order to maintain the symmetry of the circuits in the circuit systems of the first receiving circuit 200 and the second receiving circuit 300. good.
FIG. 10 shows the protection circuit of the low noise power amplifier 200a in the second embodiment. By arranging the power limiter circuit C02 between the low noise power amplifier 200a and the switch 700 in FIG. 10, it is possible to prevent the low noise power amplifier 200a from being damaged by excessive input.

As described above, in the pulse compression radar device according to the first embodiment, the transmission circuit that transmits the frequency-modulated pulse signal after digital / analog conversion, frequency conversion, and power amplification, and the received signal are low. It has two or more receiving circuits that perform pulse compression on the time axis after noise amplification, frequency conversion, and analog / digital conversion, and a directional coupler is placed at the input stage of the low noise amplifier of one receiving circuit, and the transmission circuit. A directional coupler is also arranged in the output stage of, and the transmission coupling signal coupled by the directional coupler on the transmission circuit side is adjusted in phase and amplitude, and then the reception is coupled by the directional coupler on the reception circuit side. It has a wraparound suppression circuit in which a power synthesizer for power synthesis with a coupling signal is arranged, and the output of the power synthesizer of this wraparound suppression circuit is connected to the input stage of the low noise amplifier of another receiving circuit. It is characterized by being done.

According to this configuration, by adding a directional coupler to the receiving side to make two paths of the receiving circuit, the path of receiving while canceling the wraparound of the transmitted wave during transmission (first receiving circuit). And, it can be divided into a path (second receiving circuit) for receiving the signal after transmission.
The first receiving circuit makes observations that cover a range close to the radar, and the second receiving circuit makes observations that cover a range far from the radar. It is possible to reduce the deterioration of NF in the observation of the circuit (in the conventional circuit, the deterioration of NF by the synthesizer (hybrid) occurs regardless of the observation distance).

In the first receiving circuit, the degree of coupling of the directional coupler and the loss of the power combiner (3 dB) cause a decrease in the received signal level (= deterioration of NF), but the closer the observation distance is in radar observation, the lower the reception level. By utilizing the fact that the height is increased, the S / N equivalent to that of the second receiving circuit can be maintained by appropriately selecting the coupling degree and the observation distance of the directional coupler.

Further, considering the level of the transmission signal (or noise) wrapping around the receiving circuit, the directional coupler added to the receiving circuit has an effect that the wraparound level can be reduced by the degree of coupling as compared with the conventional circuit.
In the above configuration, the first receiving circuit connected to the power synthesizer is used to observe the region shown in the observation region 1, and the second receiving circuit connected to the other directional coupler is used for observation. Observation of region 2 is performed. That is, when the observation distance (distance from the radar device) is R [m], the observation area 1 is R ≤ R _{b and the} observation area 2 is R _b <R ≤ R _max . Here, R _max [m] is the maximum observation distance of the radar device, and R _b is c × T / 2 [m] (c: speed of light [m / s], T: pulse length [s]). By performing such signal processing, it is possible to enjoy a sufficient effect of reducing wraparound of the transmitted signal without causing extra NF deterioration.

The data used for pulse compression performed by the first receiving circuit is a signal received with a time width twice or longer than the transmission pulse from the start of the transmission pulse, and the data used for pulse compression performed by the second receiving circuit is transmitted. The received signal acquired after the end of pulse transmission is used.
In this way, by setting the data length used in the first receiving circuit to be twice or more the time width of the transmission pulse, it is possible to sufficiently secure the pulse compression gain for observing the observation region 1.

Further, the pulse compression radar device according to the second embodiment includes a transmission circuit that transmits a frequency-modulated pulse signal after digital / analog conversion, frequency conversion, and power amplification, and low-noise amplification and frequency of the received signal. It has a receiving circuit that performs pulse compression on the time axis after conversion and analog / digital conversion, a directional coupler for coupling and branching the received RF signal is arranged, and directional coupling is also performed on the output stage of the transmission circuit. To synthesize the power of the transmit coupling signal coupled by the directional coupler on the transmitter circuit side with the receive coupling signal coupled by the directional coupler on the receiver circuit side after adjusting the phase and amplitude. It has a wraparound suppression circuit in which the power synthesizer of It is characterized by having a switch that can be selected and connected to either one.

According to this configuration, the effect is the same as that of the first embodiment, but since a switch is added and the receiving circuit is shared by one, it is possible to realize miniaturization and weight reduction.
Here, the switch is controlled so that the receiving circuit is connected to the output of the power synthesizer during the transmission of the pulse, and the receiving circuit is connected to the output of the directional coupler after the transmission of the pulse. With this configuration, the switch switching operation can be performed during and after the pulse transmission.

However, the data (signal) acquired during pulse transmission is obtained by correcting the amplitude level and phase of the time-series data of the transmission pulse time width or longer from the beginning of the data (signal S2) acquired after pulse transmission. It is added after S1), and this data is used as the data before pulse compression in the observation region 1. By doing so, the problem of the switch switching method, that is, the observation of the observation area 1, requires data twice the pulse transmission width, but in the switching method using the switch, the pulse after transmission in the signal S1. By generating the missing data from the signal S2 in consideration of the loss of the width data, it is possible to sufficiently secure the pulse compression gain for observing the observation region 1 even in the switch switching method.

Further, if the coupling degree (C _cpl [dB]) of the directional coupler connected to the receiving circuit is set so as to satisfy the following relational expression, the S / N of the received signal in the observation region 1 can be determined in the observation region. It is possible to secure equal or higher than the S / N in 2.
C _cpl ≤ G−L _comb
L _comb : Power synthesizer loss [dB]
G: Gain difference due to distance [dB]
(i) When the observation target is a discrete distribution type target G = 10 × log ₁₀ (R _max / R _b ) ²
(ii) When the observation target is an isolated target G = 10 × log ₁₀ (R _max / R _b ) ⁴
Further, in the above embodiment, the pulse signal subjected to frequency modulation is used as the transmission signal, but the modulation method is not limited to frequency modulation, and other modulation methods for pulse compression such as code modulation may be used.

The present invention is not limited to the above-described embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

100 ... Transmission circuit, 100a ... Modulation signal generator, 100b ... D / A converter, 100c ... Frequency converter, 100d ... High frequency power amplifier, 200 ... First receiving circuit, 200a ... Low noise power amplifier, 200b ... Frequency conversion Instrument, 200c ... A / D converter, 200d ... Pulse compressor, 300 ... Second receiving circuit, 300a ... Low noise power amplifier, 300b ... Frequency converter, 300c ... A / D converter, 300d ... Pulse compressor, 400 ... wraparound suppression circuit, 400a ... directional coupler, 400b ... phase adjuster, 400c ... amplitude adjuster, 400d ... power amplifier, 400e ... directional coupler, 400f ... power distributor, 411-41N ... delay line, 421-42N ... Amplitude adjuster, 431-43N ... Phase adjuster, 500 ... Circulator, 600 ... Transmission / reception shared antenna. 700 ... Switch, 801,802 ... Terminator, 901 ... Detection circuit, 902 ... Control circuit, A01 ... Detection circuit, A02 ... Control circuit, B01 ... Preprocessing unit, B02 ... Fourier transform unit (FFT), B03 ... Speed 0 Peripheral removal unit, B04 ... Inverse Fourier transform unit, C01, C02 ... Power limiter circuit.

Claims (22)

A transmission coupler that acquires a transmission coupling signal by frequency-converting a modulated pulse signal for pulse compression and coupling it with an output transmission signal.
A receiver coupler in which the transmission signal transmitted acquires the reception coupling signals received signal coupled to be received is reflected by the observation target,
A regulator that adjusts the amplitude and phase of the transmission coupling signal according to the wraparound component of the transmission signal included in the reception coupling signal.
A power combiner for power-combining the said reception coupling signal and the transmission coupling the signal subjected to adjustment of the amplitude and phase,
A first receiving circuit that inputs a receiving coupling signal output from the power synthesizer and performs pulse compression processing on the time axis.
It is provided with a second receiving circuit that inputs a receiving coupling signal output from the receiving coupler and performs pulse compression processing on the time axis.
A radar device in which the signal level of the reception coupling signal output from the reception coupler is higher than the signal level of the reception coupling signal output from the power synthesizer . The first reception output signal output by the first reception circuit represents the observation result in the first observation region up to the distance obtained by converting the transmission time of the pulse signal by the speed of light.
The second reception output signal output by the second reception circuit represents the observation result in the second observation region beyond the first observation region to the maximum observation distance.
The radar device according to claim 1. The first reception circuit uses the reception coupling signal acquired from the start of the pulse of the transmission signal to a time width twice the transmission time of the pulse as the data used for the pulse compression processing.
The second receiving circuit has acquired the data used for the pulse compression processing from the end of the transmission of the pulse of the transmission signal to the time obtained by adding the transmission time of the pulse to the time corresponding to the maximum observation distance. The radar device according to claim 2, which uses a signal. Moreover,
The first detection circuit that detects the output level of the first reception circuit and
With a control circuit that controls the amplitude and phase adjustment of the regulator based on the output level.
With
The control circuit controls the amplitude and phase adjustment of the regulator based on the output level in the absence of echo from the observation target.
The radar device according to any one of claims 1 to 3. The radar device according to claim 4, wherein the control circuit controls the adjustment of the amplitude and phase of the regulator so that the output level is minimized in the absence of echo from the observation target. .. Further, the first reception output signal output by the first reception circuit is input to calculate the velocity spectrum, and among the velocity components of the calculated velocity spectrum, a predetermined range is removed or the filter is removed to return to the time domain. The radar device according to any one of claims 1 to 5, further comprising a signal processing circuit . Further, disposed in the input path of at least the second receiving circuit, a radar device according to any one of claims 1 to 6 comprising a power limiter circuit to prevent excessive input of the second receiver circuit. A transmission coupler that acquires a transmission coupling signal by frequency-converting a modulated pulse signal for pulse compression and coupling it with an output transmission signal.
A receiver coupler in which the transmission signal transmitted acquires the reception coupling signals received signal coupled to be received is reflected by the observation target,
A regulator that adjusts the amplitude and phase of the transmission coupling signal according to the wraparound component of the transmission signal included in the reception coupling signal.
A power combiner for power-combining the said reception coupling signal and the transmission coupling the signal subjected to adjustment of the amplitude and phase,
A switching circuit that switches and outputs the reception coupling signal output from the power synthesizer and the reception coupling signal output from the reception coupling device.
The reception coupling signal output from the power combiner and the reception coupling signal output from the reception coupler, which are switched and output by the switching circuit, are input, and pulse compression processing is performed on the time axis, respectively. Equipped with a receiving circuit
A radar device in which the signal level of the reception coupling signal output from the reception coupler is higher than the signal level of the reception coupling signal output from the power synthesizer . The first reception output signal output by the reception circuit that inputs the reception coupling signal output from the power synthesizer is an observation in the first observation region up to a distance obtained by converting the transmission time of the pulse signal by the speed of light. Represents the result
The second reception output signal output by the reception circuit that inputs the reception coupling signal output from the reception coupler represents the observation result in the second observation region beyond the first observation region and up to the maximum observation distance. ,
The radar device according to claim 8. The switching circuit outputs a reception coupling signal output from the power synthesizer from the start of transmission of the pulse of the transmission signal to the end of transmission, and corresponds to the maximum observation distance after the end of transmission of the pulse of the transmission signal. The radar device according to claim 9, which outputs a reception coupling signal output from the reception coupler until time. The receiving circuit corrects the amplitude and phase of the time series data of the reception coupling signal acquired from the end of transmission of the pulse of the transmission signal to the elapse of the transmission time of the pulse of the transmission signal .
The time-series data of the amplitude and the reception coupling signal phase corrected, by adding after the time-series data of the received coupling signal output from the power combiner during transmission of pulses of the transmission signal, when the The series data is targeted for pulse compression processing in the first observation region.
The reception coupling signal output from the reception coupler is pulse-compressed in the second observation region from the end of transmission of the pulse of the transmission signal to the time obtained by adding the transmission time of the pulse to the time corresponding to the maximum observation distance. The radar device according to claim 9 or 10, which is the object of processing . Moreover,
The first detection circuit that detects the output level of the reception circuit and
With a control circuit that controls the amplitude and phase adjustment of the regulator based on the output level.
With
The control circuit controls the amplitude and phase adjustment of the regulator based on the output level in the absence of echo from the observation target.
The radar device according to any one of claims 8 to 11. The control circuit, when the reception circuit is inputting a reception coupling signal output from the power combiner, in the absence echoes from the observation target,
As the output level is minimized, to control the adjustment of the regulator of the amplitude and phase,
The radar device according to claim 12. Further, when the reception coupling signal output from the power synthesizer is input to the reception circuit, the first reception output signal output by the reception circuit is input to calculate the speed spectrum, and the calculated speed is obtained. The radar device according to any one of claims 8 to 13, further comprising a signal processing circuit that removes or filters a predetermined range of the velocity components of the spectrum and returns them to the time domain . The radar device according to any one of claims 8 to 14, further comprising a power limiter circuit that is arranged in the input path of the receiving circuit and prevents excessive input of the receiving circuit . The regulator adjusts the amplitude and phase of the transmission coupling signal so as to have the same amplitude and the opposite phase with respect to the wraparound component of the transmission signal included in the reception coupling signal.
The power synthesizer power-synthesizes the reception coupling signal acquired by the reception coupling device with the transmission coupling signal whose amplitude and phase are adjusted by the regulator.
The radar device according to any one of claims 1 to 15. Claim wherein the receiver coupler, the coupling of the coupling between the received signal to obtain the reception coupling signals to or less difference value of the gain difference due observation distance and said power combiner of the power combiner loss The radar device according to any one of 1 to 16 . Further, a power distributor for distributing the transmission coupling signal output from the transmission coupler to a plurality of systems is provided.
The regulator performs delay correction, amplitude adjustment, and phase adjustment according to a plurality of wraparound components of the transmission signal to each of the transmission coupling signals whose power is distributed to the plurality of systems.
Any of claims 1 to 17, wherein the power synthesizer power-synthesizes and outputs a plurality of transmission coupling signals to which the delay correction, amplitude adjustment, and phase adjustment have been performed together with the reception coupling signal. The radar device according to one item . The power combiner has a first signal input end, a second signal input end, an in-phase composite output end, and a reverse-phase composite output end, and the transmission coupling signal whose amplitude and phase are adjusted by the regulator is the first. The reception coupling signal input from the 1 signal input end and output from the reception coupler is input from the second signal input end, and the signal output from the reverse phase composite output end is output from the power combiner. Including a 4-terminal circuit that serves as a reception coupling signal
Moreover,
A second detection circuit that detects the signal level output from the common mode combined output end of the power synthesizer, and
A control circuit that controls the amplitude and phase adjustment of the regulator based on the signal level output from the common mode composite output end of the power synthesizer.
To prepare
The radar device according to any one of claims 1 to 18. The control circuit controls the amplitude and phase adjustment of the regulator so that the signal level output from the in-phase synthesis output end of the power synthesizer is maximized in the absence of echo from the observation target. The radar device according to claim 19 . The pulse signal modulated for pulse compression is frequency-converted and coupled with the output transmission signal to obtain the transmission coupling signal.
The transmission signal transmitted by the received signal and the coupling of the received Ru signal is reflected by the observation target to obtain received coupling signal,
The amplitude and phase of the transmission coupling signal are adjusted according to the wraparound component of the transmission signal included in the reception coupling signal .
Wherein the amplitude and the receiving coupling signal and the transmission coupling the signal subjected to phase adjustment and power combining,
The power-synthesized reception coupling signal is subjected to pulse compression processing on the time axis to be subjected to pulse compression processing.
The reception coupling signal acquired by the coupling with the reception signal is subjected to pulse compression processing on the time axis .
A radar signal processing method in which the signal level of the reception coupling signal acquired by coupling with the reception signal is higher than the signal level of the power-synthesized reception coupling signal . The pulse signal modulated for pulse compression is frequency-converted and coupled with the output transmission signal to obtain the transmission coupling signal.
Received signal and coupling the transmission signal transmitted is received are reflected by the observation target to obtain received coupling signal,
The amplitude and phase of the transmission coupling signal are adjusted according to the wraparound component of the transmission signal included in the reception coupling signal .
Wherein the amplitude and the receiving coupling signal and the transmission coupling the signal subjected to phase adjustment and power combining,
The reception coupling signal after the power synthesis and the reception coupling signal before the power synthesis are switched and output.
The reception coupling signal after the power synthesis and the reception coupling signal before the power synthesis, which are switched and output, are respectively subjected to pulse compression processing on the time axis .
A radar signal processing method in which the signal level of the reception coupling signal acquired by coupling with the reception signal is higher than the signal level of the power-synthesized reception coupling signal .

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