JPH03180791A - Cw radar - Google Patents

Abstract

PURPOSE:To increase the degree of separation between transmission and reception to extend the search distance by adding the signal, which is obtained by amplitude/ phase weighting of a reference signal divided from the transmission power, to a reception signal to suppress the signal of the transmission power. CONSTITUTION:Separated transmission power PTa to be the reference signal is extracted from transmission power PT by a power distributor 42 and is subjected to amplitude weighting and phase weighting in a variable gain amplifier 44 and a phase device 46 to have the same amplitude level as a leak signals Ls inputted to a mixer 32 and have a phase opposite to that of this leak signal, and a weighted signal Ws is sent to a power adder 48. The adder 48 adds the signal, where a reflection signal of a marker M and the leak signal Ls are superposed, inputted from a circuit separator 24 and the signal Ws and sends the result to the mixer 32. In this case, waveforms of the power PT and the signal Ls are observed by a spectrum analyzer 50 and the signal Ls having the waveform similar to that of the power PT is suppressed by the signal Ws, and therefore, a suppressed signal Cs consisting of only the reflection signal of the marker M is sent to the mixer 32 and is supplied to an indicator 38 through a Doppler processor 36. Thus, the degree of separation between transmission and reception is improved, and a continuous radio wave WT dependent upon the larger power PT can be radiated to extend the search distance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a shared transmitting and receiving antenna to continuously transmit and receive radio waves such as non-modulated waves, frequency modulated waves, phase modulated waves, etc.
CW (Contin
(Uous Wave) radar.

[Prior Art] Conventionally, a CW radar, which is superior in measuring the moving speed of a moving target compared to a pulse radar or the like, emits continuous radio waves from an antenna and simultaneously receives reflected radio waves from the target.

Then, the Doppler effect caused by the above-mentioned reflection, that is, the received signal of the desired wave is detected and superimposed on the strong reflected wave from a fixed object, etc., which is a non-target, by detecting only the signal of the desired wave with frequency deviation. It has fundamental characteristics that allow it to be easily separated and detected in the frequency domain.

In practical use, CW radar with such fundamental characteristics adopts a method that uses separate dedicated antennas for transmission and reception (hereinafter referred to as separate antenna method).
There is a method in which one antenna is used for both transmission and reception (hereinafter referred to as a single antenna method).

FIG. 2 shows an example of the configuration of a CW radar using the single antenna method.

In this example, the transmission power from the transmitter 2 is supplied to a terminal a of a circuit separator 4 such as a Magic T or a circulator, and further led to an antenna 6 connected to the terminal A and radiated as a continuous radio wave W. This continuous radio wave W is reflected by a moving object 8, which is a target, and causes a frequency deviation due to the Doppler effect, and a part of this reflected wave WR is transmitted to the antenna 6.
received at The received signal here is input to the mixer 10 via the circuit separator 4.

Further, the mixer 10 is supplied with an oscillation signal having a frequency equal to the difference between the IF multiplied signals with respect to the received signal from the local oscillator 12, and performs frequency conversion. The IF multiplied signal obtained here is sent to the Doppler processor 14.

The Doppler processor 14 uses, for example, a comb filter in which narrow band filters are connected in parallel, and separates only the Doppler deviation signal from the IF multiplied signal and sends it to the indicator 16. The indicator 16 displays movement information of the moving object 8 based on the Doppler deviation signal.

[Problems to be Solved by the Invention] However, due to incomplete isolation in the circuit separator 4, a part of the transmission power supplied to the terminal a leaks to the mixer 10 via the terminal C, and furthermore, the antenna 6
Reflected power related to a standing wave (V, S''vVR) due to its own frequency characteristics or mismatch with a feed line or the like is inputted to the mixer 10 via the terminal bSc of the circuit separator 4.

In this way, leakage or spillover signals to the receiving system (mixer 10) that are not radiated into space are not accompanied by Doppler deviation. Therefore, in principle, there is no problem in transmitting the desired wave signal, which is a Doppler signal, but the leakage signal is particularly high level.

In this case, the leakage signal may cause burnout of the mixer 10 or saturation in signal processing, making it difficult to obtain a predetermined receiving sensitivity.

Therefore, since the power of the leakage signal is proportional to the transmission power of the transmitter 2, it is necessary to reduce the output power of the transmitter 2 so that the power of the leakage signal becomes a sufficiently low level.

Therefore, the conventional single antenna type CW radar is
Compared to a separate antenna type CW radar that requires two antennas, the size of the antenna equipment is reduced and work to make the beam axes of each antenna parallel is not required, but the transmission power is limited. This has the disadvantage that the detection distance is reduced.

The present invention was made in view of the above problems, and its purpose is to provide a CW radar that suppresses leakage signals to the receiving system or reflected power of the transmission line, improves the degree of separation between transmitting and receiving, and has an excellent detection distance. It's about doing.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the CW radar of the present invention has the following features: One antenna is connected, the supplied transmission power is sent to the antenna, and the received signal from the antenna is sent to the antenna. a power divider that derives a reference signal by dividing the transmission power; an amplitude phase weighting unit that transmits a weighted signal obtained by subjecting the reference signal to predetermined amplitude weighting and phase weighting; and the received signal. and an addition means for adding the weighted signal and suppressing the signal of the transmission power superimposed on the received signal.

[Operation] In the above configuration, the reference signal derived by dividing the transmission power is subjected to amplitude weighting and phase weighting so as to have the opposite phase and the same amplitude as the leakage signal and reflected power generated in the receiving system to soften the addition.

As a result, leakage signals and reflected power are suppressed, and the degree of separation between transmission and reception in the single antenna system is improved.

[Embodiment] Next, an embodiment of the CW radar according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of the embodiment.

The example shown in FIG. 1 includes an antenna system A, a transmitting system T, a receiving system R, and an amplitude/phase weighting section Y, which is a main part of the present invention and performs amplitude weighting and phase weighting and sends out a weighted signal W. Furthermore, the schematic configuration includes a measuring device Z for visually checking the suppression state by weighted signals of unnecessary leakage signals to the receiving system and reflected power (hereinafter referred to as leakage signals) generated on the transmission line in the antenna system. has been done.

Antenna system A is a moving object, which includes an antenna 22 such as a parabola that is driven to face the IM, radiate continuous radio waves W, and receive reflected waves W (human sensation), and this antenna 2.
2 and a circuit separator 24 such as a magic T or a circulator connected to the power supply line through a power supply line.

The transmission system T includes a transmitter 28 that transmits transmission power P at a predetermined frequency.

The receiving system R includes a mixer 32 that performs frequency conversion, a local oscillator 34 that supplies a local oscillation frequency signal to the mixer 32, and a Doppler processor 36 that is provided with a comb filter. Display of movement information related to M or target M
For example, PP
I (Plan Po5ition Indicato
r) It has an indicator 38 with a sp:)-p, etc.

The amplitude/phase weighting unit Y is arranged between the antenna 22 and the transmitter 28, and supplies the transmission power PT to the antenna 22 connected to the terminal A via the terminal a, and also extracts a part of the transmission power PT. Power divider 4 to obtain separated transmission power PTa
2, a variable gain amplifier (amplitude weighting means) 44 that performs amplitude weighting on the separated transmission power PTa, and a phase shifter (amplitude weighting means) that performs phase weighting and sends out a weighted signal W.
phase weighting means> 46.

Further, the circuit separator 24 is disposed between the mixer 32 and is supplied with a weighting signal W.
4 to the reflected wave W of the target M.

(desired wave) and the leakage signal Ls superimposed on it,
and a power adder 48 for deriving the suppression signal C5.

The measuring instrument Z is provided with a spectrum analyzer 50 that observes the waveform of the leakage signal and is equipped with a coupler for detection.

The operation in the above configuration will be explained below.

Transmitter 28 generates transmission power FT and sends it to power divider 42 .

The power divider 42 sends the transmission power P to the circuit separator 24 and extracts the separated transmission power PTa, which serves as a reference signal, and sends it to the variable gain amplifier 44. The variable gain amplifier 44 weights the amplitude so that the separated transmission power PTa has the same amplitude level as the leakage signal inputted to the mixer 32 without being radiated into the air.

The amplitude weighted signal is then provided to phase shifter 46 . The phase shifter 46 sends to the power adder 48 a weighted signal W that has been phase-weighted so as to be formed to have an opposite phase to the leakage signal sent from the terminal C of the circuit separator 24 .

The power adder 48 combines a signal manually input from the terminal C of the circuit separator 24, that is, a superimposed signal of the reflected signal from the target M and the leakage signal, and a weighted signal Ws sent from the shifter 46. The power is added and sent to the input terminal of the mixer 32.

In this case, the spectrum analyzer 50 observes the waveforms of the transmission power P and the leakage signal L5, and a leakage signal having a similar waveform to the transmission power P7 is obtained.

is suppressed by weighting signal W5. This adjustment is performed by adjusting the gain of the variable gain amplifier 44 and further adjusting the phase of the phase shifter 46.

In this case, the leakage signal is the weighted signal W.

A suppressed signal Cs, which is only the reflected signal related to the target M, is obtained from the power adder 48 and sent to the input end of the mixer 32 . The signal is further supplied to an indicator 38 via a Doppler processor 36.

Note that in the above embodiment, the variable gain amplifier 44 is used for amplitude weighting, but the present invention is not limited to this. The present invention also includes the use of an attenuator or the like.

As explained above, the leakage signal Ls is removed from the human input signal of the mixer 32, and only the reflected signal related to the target M is formed. As a result, the degree of separation between transmission and reception is improved, and continuous radio waves W can be emitted from the antenna 22 to the target M with a larger value of transmission power PT, and the detection distance is improved.

[Effects of the Invention] As explained above, according to the CW radar of the present invention, one antenna is connected to a separator that sends the supplied transmission power to the antenna and derives a received signal from the antenna. a power divider that derives a reference signal by dividing the transmission power; an amplitude phase weighting means that transmits a weighted signal obtained by applying predetermined amplitude weighting and phase weighting to the reference signal; and the received signal and the weighted signal. and an adding means for suppressing the signal of the transmission power superimposed on the received signal.

This has the advantage of suppressing leakage signals or reflected power to the receiving system, improving the degree of separation between transmission and reception, and improving the detection distance.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a CW radar according to the present invention, and FIG. 2 is an overall configuration diagram of a conventional CW radar. 22... Antenna 24... Circuit separator 28
...Transmitter 32...Mixer 34...Local oscillator 38...Indicator 44...Variable gain amplifier 48...Power adder Cs...Suppression signal PT...Transmission power R・...Receiving system W,...Weighted signal Y...Amplitude/phase weighting unit 36...Doppler processor 42...Power divider 46...Phase shifter A...Antenna system... ...Leakage signal PTa...Separated transmission power T...Transmission system

Claims (1)

[Claims] (1) A separator to which one antenna is connected, which sends the supplied transmission power to the antenna and derives a received signal from the antenna, and a power divider which derives a reference signal by dividing the transmission power. amplitude and phase weighting means for transmitting a weighted signal obtained by subjecting the reference signal to predetermined amplitude weighting and phase weighting; and adding the received signal and the weighted signal to suppress the signal of the transmission power superimposed on the received signal. A CW radar comprising: an addition means;