JPH08313618A - Receiver for radar - Google Patents

Abstract

PURPOSE: To enhance accuracy in the setting of gain of a receiving system by shielding undesired signals from an antenna effectively at the time of operation of an automatic noise level control circuit. CONSTITUTION: The receiver for radar comprises an RF low noise amplifier 4 for amplifying an RF (Radio Frequency) signal in an active transmitter/ receiver module Mn having function for amplifying and phase regulating each transmitting/receiving signal, and an RF low noise amplifier 8 for amplifying an RF signal from the active transmitter/receiver module Mn in an RF front end 1 for amplifying and converting an RF signal from the active transmitter/ receiver module Mn into an IF (Intermediate Frequency) signal. The receiver for radar further comprises an automatic noise level control circuit 12 for controlling the gain of receiving system circuit at a constant level while preventing fluctuation of S/N level, a power supply 13 for the RF low noise amplifier 8 constituting the RF front end, a switch S1 for turning the RF signal on/off in the active transmitter/receiver module Mn, and a switch S2 for turning the power supply 13 on/off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic noise level control circuit (Automatic Noise Leveli).
ng, hereinafter referred to as an ANL circuit), the present invention relates to a radar transceiver configured to effectively block an unnecessary signal input from an antenna.

[0002]

2. Description of the Related Art A conventional device of this type is shown in FIG. In the figure, the active transceiver module M _n from M ₁ having the amplification and phase adjusting function of the transmitting and receiving each signal, 1 is amplified and IF (Intermediate Fr signals from the active transceiver module M _n
RF (Radio F) that converts to an "equency" signal
front end, 2 an antenna for transmitting and receiving radio waves, 3 a circulator for switching transmission / reception, 4 an RF low noise amplifier for amplifying an RF signal from the circulator 4, 5 a circulator for switching transmission / reception, 6 a circulator 5 RF high-power amplifier for amplifying the RF signal of the RF signal, 7 is a phase shifter for changing the phase of the RF signal from the circulator 5 and the RF front end 2, and 8 is the RF from the active transceiver module M _n in the RF front end 1. R to amplify the signal
F low noise amplifier, 9 is a mixer that constitutes the RF front end 1, 10 is a local signal generator that gives a local signal to the mixer 9, 11 is an IF amplifier that amplifies the signal from the RF front end 1, and 12 is An ANL circuit (Automatic Noise) that plays a role of preventing fluctuations in signal noise level by keeping the gain of the receiving system circuit constant
Leveling).

Next, the operation will be described. The RF reception signals input to the active transmission / reception module M _n are amplified and phase adjusted, and the output signals from the respective active transmission / reception modules are combined and input to the RF front end 1.
Here, it is amplified and IF-converted, and again amplified by the IF amplifier 11 connected to the output side thereof. By the ANL circuit 12 connected to the output side of the IF amplifier 11, it is possible to prevent the reception system gain from varying and the signal noise level to vary because the performance of the electric components and the like changes with temperature.

[0004]

The conventional radar transceiver as described above has the following problems. That is, in order to prevent the ANL noise from fluctuating due to the AGC / STC voltage, the AGC noise is detected during the ANL noise detection time.
The voltage is kept at 0V. Therefore, when a strong jamming is received at the time of this detection, the ANL circuit cannot detect only the normal reception noise, resulting in an incorrect reception system gain setting. The AGC voltage is set to ST because the tracking sensitivity changes or the tracking error is reduced due to the change in the signal level.
The C voltage is applied to each in order to prevent saturation of the receiver in the search mode.

The present invention has been made to solve the above problems, and provides a transceiver for radar that effectively blocks unnecessary signals received by an antenna when the ANL circuit is operating.

[0006]

In the transceiver for a radar according to the first embodiment, an ANL circuit is used as a power source for applying a voltage to an RF signal in an active transceiver module and an RF low noise amplifier forming an RF front end. By occasionally shutting off, the influence of unwanted signals such as jamming signals and clutter signals is minimized.

In the radar transceiver according to the second embodiment, the RF signal and the RF signal in the active transceiver module are used.
By shutting off the input signal to the front end when the ANL circuit is activated, the influence of unnecessary signals such as jamming signals and clutter signals is minimized.

In the radar transceiver according to the third embodiment, the RF signal and the RF signal in the active transceiver module are used.
The influence of unnecessary signals such as jamming signals and clutter signals is minimized by shutting off the local signals to the mixer forming the front end when the ANL circuit is activated.

In the radar transceiver according to the fourth embodiment, the RF signal in the active transceiver module, the power source for applying a voltage to the RF low noise amplifier constituting the RF front end, and the mixer for constituting the RF front end are provided. By blocking the local signal when the ANL circuit is activated, the influence of unwanted signals such as jamming signals and clutter signals is minimized.

In the radar transceiver according to the fifth embodiment, the RF signal in the active transceiver module, the power supply for applying a voltage to the RF low noise amplifier constituting the RF front end, and the input signal to the RF front end are ANL.
The effect of unwanted signals such as jamming signals and clutter signals is minimized by shutting off the circuit when the circuit is activated.

In the radar transceiver according to the sixth embodiment, the RF signal in the active transceiver module, the input signal to the RF front end and the local signal to the mixer forming the RF front end are cut off when the ANL circuit is activated. As a result, the influence of unwanted signals such as jamming signals and clutter signals is minimized.

In the radar transceiver according to the seventh embodiment, the RF signal in the active transceiver module, the power source for applying a voltage to the RF low noise amplifier forming the RF front end, the input signal to the RF front end and the RF signal. A local signal to the mixer that constitutes the front end
The effect of unnecessary signals such as jamming signals and clutter signals is minimized by cutting off the NL circuit when it is activated.

[0013]

In the transceiver for radar according to the first embodiment,
When the ANL circuit is operating, the power supply for applying the voltage to the RF signal in the active transceiver module and the RF low noise amplifier that constitutes the RF front end is shut off, so unnecessary signals such as jamming signals and clutter signals input to the receiving system are suppressed. As a result, the accuracy of receiving system gain setting is improved.

In the transceiver for radar according to the second embodiment, the RF signal in the active transceiver module and the input signal to the RF front end are shut off when the ANL circuit is activated, so that the jamming signal input to the receiving system is Unnecessary signals such as clutter signals are suppressed, and the accuracy of receiving system gain setting is improved.

In the radar transceiver according to the third embodiment, when the ANL circuit is activated, the RF signal in the active transceiver module and the local signal to the mixer forming the RF front end are cut off, so that they are input to the receiving system. Unwanted signals such as jamming signals and clutter signals are suppressed, and the accuracy of the gain setting of the receiving system is improved.

In the radar transceiver according to the fourth embodiment, when the ANL circuit is activated, the RF signal in the active transceiver module, the power supply for applying a voltage to the RF low noise amplifier constituting the RF front end, and the RF front end are provided. Since it shuts off the local signal to the mixer that you configure,
Unwanted signals such as jamming signals and clutter signals input to the receiving system are suppressed, and the accuracy of the receiving system gain setting is improved.

In the transceiver for radar according to the fifth embodiment, when the ANL circuit is activated, the RF signal in the active transceiver module, the power supply for applying a voltage to the RF low noise amplifier constituting the RF front end, and the RF front end are supplied. Since the input signal is blocked, unnecessary signals such as jamming signals and clutter signals input to the reception system are suppressed, and the accuracy of the reception system gain setting is improved.

In the radar transceiver according to the sixth embodiment, when the ANL circuit is operating, the RF signal in the active transceiver module, the input signal to the RF front end and the R signal.
Since the local signal to the mixer that constitutes the F front end is blocked, the jamming signal input to the receiving system
Unnecessary signals such as clutter signals are suppressed, and the accuracy of receiving system gain setting is improved.

In the transceiver for a radar according to the seventh embodiment, when the ANL circuit is operating, the RF signal in the active transceiver module, the power supply for applying a voltage to the RF low noise amplifier constituting the RF front end, and the RF front end are supplied. Input signal and local signal to the mixer that forms the RF front end are blocked, so unnecessary signals such as jamming signals and clutter signals input to the receiving system are suppressed,
The accuracy of the receiver gain setting is improved.

[0020]

【Example】

Example 1. FIG. 1 is a diagram showing a first embodiment of the present invention. In FIG. 1, M _n and 1 to 12 are shown in FIG. Reference numeral 13 denotes a power source for the RF low noise amplifier 8 constituting the RF front end 1, S1 denotes a first switch for turning on / off the RF signal in the active transmission / reception module M _n , and S
Reference numeral 2 is a second switch for turning on / off the power supply to the RF low noise amplifier 8, and L is an ANL activation signal for informing the switches S1 and S2 that the ANL circuit 12 is operating.

The operation of the first embodiment will be described. A
When the NL circuit 12 operates, unwanted signals such as jamming signals and clutter signals received by the antenna 2 pass through the RF low noise amplifier 4, the RF front end 1 and the IF amplifier 11 and are input to the ANL circuit 12, where they are properly processed. Since it is impossible to detect only the received noise, it is possible to prevent an incorrect gain setting and to enable accurate automatic noise level control. That is, the ANL operation signal L from the ANL circuit 12
This turns off the switch first switch S1 and the second switch S2, thereby cutting off the RF signal in the active transceiver module M _n and the voltage to the RF low noise amplifier 8 forming the RF front end 1. Therefore, the unnecessary signal is significantly suppressed, and the ANL circuit 12 can detect only the noise generated by the receiving system.

Example 2. FIG. 2 is a diagram showing a second embodiment of the present invention. In FIG. 2, M _n and 1 to 12 are shown in FIG. S1 is a first switch for turning on / off an RF signal in the active transceiver module M _n , S2
Is a second switch for turning on / off the RF signal from the active transceiver module M _n to the RF front end 2.
L is an ANL activation signal that informs the switches S1 and S2 that the ANL circuit 13 is operating.

The operation of the second embodiment will be described. A
When the NL circuit 12 operates, unwanted signals such as jamming signals and clutter signals received by the antenna 2 pass through the RF low noise amplifier 4, the RF front end 1 and the IF amplifier 11 and are input to the ANL circuit 12, where they are properly processed. Since it is impossible to detect only the received noise, it is possible to prevent an incorrect gain setting and to enable accurate automatic noise level control. That is, the ANL operation signal L from the ANL circuit 12
R the first switch S1 and the second switch S2 is turned off, whereby the RF signal and active transceiver module M _n in the active transceiver module M _n by
The RF signal to the F front end 2 is cut off. For that reason,
The unnecessary signal is significantly suppressed, and the ANL circuit 12 can sense only the noise generated by the receiving system.

Example 3. FIG. 3 is a diagram showing a third embodiment of the present invention. In FIG. 3, M _n and 1 to 12 are shown in FIG. Reference numeral 13 is a power supply to the RF low noise amplifier constituting the active transmission / reception module M _n , S1 is a first switch for turning on / off the RF signal in the active transmission / reception module M _n , S2 is the local signal generator 10 and the RF front end 1 A second switch for turning on / off a local signal to the mixer 9 that constitutes it, L is the above-mentioned first switch
To the switch S1 and the second switch S2 of the ANL circuit 1
2 is an ANL activation signal indicating that 2 is activated.

The operation of the third embodiment will be described. A
When the NL circuit 12 operates, unwanted signals such as jamming signals and clutter signals received by the antenna 2 pass through the RF low noise amplifier 4, the RF front end 1 and the IF amplifier 11 and are input to the ANL circuit 12, where they are properly processed. Since it is impossible to detect only the received noise, it is possible to prevent an incorrect gain setting and to enable accurate automatic noise level control. That is, the ANL operation signal L from the ANL circuit 12
Turns off the first switch S1 and the second switch S2, thereby cutting off the RF signal in the active transceiver module M _n and the local signal from the local signal generator 10 to the mixer 9 constituting the RF front end 1. . Therefore, the unnecessary signal is significantly suppressed, and the AN
The L circuit 13 can sense only the noise generated by the receiving system.

Example 4. FIG. 4 is a diagram showing a first embodiment of the present invention. In FIG. 4, M _n and 1 to 12 are shown in FIG. Reference numeral 13 is a power source for the RF low noise amplifier 8 constituting the RF front end 1, S1 is a first switch for turning on / off the RF signal in the active transmission / reception module M _n , and S2 is for turning on / off the power source for the RF low noise amplifier 8. The second switch, S3, is the local signal generator 10
From the third switch for turning on / off a local signal from the RF front end 1 to the mixer 9, 14 is a second switch
A switch module constituted by the switch S2 and the third switch S3, and L is an ANL operation signal for informing the first switch S1 and the switch module 15 that the ANL circuit 12 is operating.

The operation of the fourth embodiment will be described. A
When the NL circuit 12 operates, unwanted signals such as jamming signals and clutter signals received by the antenna 2 pass through the RF low noise amplifier 4, the RF front end 1 and the IF amplifier 11 and are input to the ANL circuit 12, where they are properly processed. Since it is impossible to detect only the received noise, it is possible to prevent an incorrect gain setting and to enable accurate automatic noise level control. That is, the ANL operation signal L from the ANL circuit 12
Thereby turns off the first switch switch S1, the second switch S2 and the third switch S3 in the switch module 14, and thereby the RF signal in the active transmission / reception module M _n and the RF low noise amplifier configuring the RF front end 1. Voltage to 8 and local signal generator 10 to R
The local signal to the mixer 9 constituting the F front end 1 is cut off. Therefore, the unnecessary signal is significantly suppressed, and the ANL circuit 12 can detect only the noise generated by the receiving system.

Example 5. FIG. 5 is a diagram showing a fifth embodiment of the present invention. In FIG. 5, M _n and 1 to 12 are shown in FIG. Reference numeral 13 is a power source for the RF low noise amplifier 4 constituting the active transceiver module M _n , S1 is a first switch for turning on / off the RF signal in the active transceiver module M _n , and S2 is a power source for the RF low noise amplifier 8 The second switch, S3, is the RF from the active transceiver module M _n to the RF front end 1.
A third switch for turning on / off a signal, 14 is a switch module composed of the second switch S2 and the third switch S3, and L is the switch module 14
This is an ANL activation signal indicating that the NL circuit 12 is operating.

The operation of the fifth embodiment will be described. A
When the NL circuit 12 operates, unwanted signals such as jamming signals and clutter signals received by the antenna 2 pass through the RF low noise amplifier 4, the RF front end 1 and the IF amplifier 11 and are input to the ANL circuit 12, where they are properly processed. Since it is impossible to detect only the received noise, it is possible to prevent an incorrect gain setting and to enable accurate automatic noise level control. That is, the ANL operation signal L from the ANL circuit 12
Causes the first switch S1, the second switch 14-S2 and the third switch S3 in the switch module 14 to be turned off, whereby the active transceiver module M _n
The internal RF signal, the voltage to the RF low noise amplifier 8 constituting the RF front end 1 and the RF signal from the active transceiver module M _n to the RF front end 1 are shut off. Therefore, the unnecessary signal is significantly suppressed, and the ANL circuit 12 can detect only the noise generated by the receiving system.

Example 6. FIG. 6 is a diagram showing a sixth embodiment of the present invention. In FIG. 6, M _n and 1 to 12 are shown in FIG. Reference numeral 13 is a power source for the RF low noise amplifier constituting the active transceiver module M _n , S1 is a first switch for turning on / off an RF signal in the active transceiver module M _n , and S2 is from the active transceiver module M _n to the RF front end 1. Is a second switch for turning on / off the RF signal of the local signal generator 10
From the third switch for turning on / off a local signal from the RF front end 1 to the mixer 9, 14 is a second switch
A switch module constituted by the switch S2 and the third switch S3, and 15 notifies the switch module 14 that the ANL circuit 12 is operating.
This is the NL operation signal.

The operation of the sixth embodiment will be described. A
When the NL circuit 12 operates, unwanted signals such as jamming signals and clutter signals received by the antenna 2 pass through the RF low noise amplifier 4, the RF front end 1 and the IF amplifier 11 and are input to the ANL circuit 12, where they are properly processed. Since it is impossible to detect only the received noise, it is possible to prevent an incorrect gain setting and to enable accurate automatic noise level control. That is, the ANL operation signal L from the ANL circuit 12
Causes the first switch S1, the second switch S2, and the third switch S3 to be turned off, whereby the RF signal in the active transceiver module M _n , the RF signal from the active transceiver module M _n to the RF front end 1 and the local signal. The local signal from the signal generator 10 to the mixer 9 constituting the RF front end 1 is cut off. Therefore, the unnecessary signal is significantly suppressed, and the ANL circuit 12 can detect only the noise generated by the receiving system.

Example 7. FIG. 7 is a diagram showing a seventh embodiment of the present invention. In FIG. 7, M _n and 1 to 12 are shown in FIG. Reference numeral 13 is a power source for the RF low noise amplifier constituting the active transceiver module M _n , S1 is a first switch for turning on / off the RF signal in the active transceiver module M _n , and S2 is for turning on / off the power source for the RF low noise amplifier 8. A second switch, S3 is a third switch for turning on / off an RF signal from the active transceiver module M _n to the RF front end 1, and S4 is a local signal from the local signal generator 10 to the mixer 9 constituting the RF front end 1. A fourth switch that turns the
14 is a first switch S1, a second switch S2, a third switch
Switch module composed of the switch S3 and the fourth switch S4, and L is the switch module 1
An AN that informs the ANL circuit 12 that it is operating.
This is the L actuation signal.

The operation of the seventh embodiment will be described. A
When the NL circuit 12 operates, unwanted signals such as jamming signals and clutter signals received by the antenna 2 pass through the RF low noise amplifier 4, the RF front end 1 and the IF amplifier 11 and are input to the ANL circuit 12, where they are properly processed. Since it is impossible to detect only the received noise, it is possible to prevent an incorrect gain setting and to enable accurate automatic noise level control. That is, the ANL operation signal L from the ANL circuit 12
The first switch S1, the second switch S2, the third switch
Turns off the switch S3 and the fourth switch S4, RF whereby RF signals in the active transceiver module M _n, the voltage to the RF low-noise amplifier 8 which constitutes the RF front end 1, the active transceiver module M _n
The RF signal to the front end 1 and the local signal from the local signal generator 10 to the mixer 9 constituting the RF front end 1 are shut off. Therefore, the unnecessary signal is significantly suppressed, and the ANL circuit 12 can detect only the noise generated by the receiving system.

[0034]

According to the first, second, third, fourth, fifth, sixth and seventh embodiments, as compared with the conventional radar transceiver, the ANL circuit has the configuration as described above. Unwanted signals such as jamming signals during operation can be ignored. Therefore A
There is an effect that the NL circuit is properly operated to improve the setting accuracy of the reception system gain.

[Brief description of drawings]

FIG. 1 is a block diagram of a radar transceiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a radar transceiver according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a radar transceiver according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a radar transceiver according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a radar transceiver according to a fifth embodiment of the present invention.

FIG. 6 is a block diagram of a radar transceiver according to a sixth embodiment of the present invention.

FIG. 7 is a block diagram of a radar transceiver according to a seventh embodiment of the present invention.

FIG. 8 is a block diagram of a conventional radar transceiver.

[Explanation of symbols]

1 RF front end, 2 antennas, 3 circulator, 4 RF low noise amplifier, 5 circulator,
6 RF high power amplifier, 7 phaser, 8 RF low noise amplifier, 9 mixer, 10 local signal generator, 11
IF amplifier, 12 ANL circuit, 13 power supply, 14
Switch module, _Mn active transceiver module, LANL activation signal, S1 first switch, S2
Second switch, S3 Third switch, S4 Fourth
Switch.

Claims (7)

[Claims] 1. An active transmission / reception module having a transmission / reception function for use in an active phased array radar, an RF (Radio Frequency) signal which is a combined output of the active transmission / reception module, and an IF (Intermediate Freq).
RF front end for converting to an RF signal, an IF amplifier for amplifying the output signal of the RF front end, and an output side of this amplifier, which prevents fluctuations in the reception gain and fluctuations in the noise level of the signal. An automatic noise level control circuit, a power supply for applying a voltage to an RF low noise amplifier forming the RF front end, a local signal generator for supplying a local signal to a mixer forming the front end, and an RF in the active transceiver module. A first switch for turning a signal on and off, and the RF
A radar transceiver comprising a second switch for turning on / off a power supply to an RF low noise amplifier in a front end. 2. An active transmission / reception module having a transmission / reception function for use in an active phased array radar, an RF (Radio Frequency) signal which is a composite output of the active transmission / reception module, and an IF (Intermediate Freq).
RF front end for converting to an RF signal, an IF amplifier for amplifying the output signal of the RF front end, and an output side of this amplifier, which prevents fluctuations in the reception gain and fluctuations in the noise level of the signal. An automatic noise level control circuit, a local signal generator for giving a local signal to a mixer constituting the front end, a first switch for turning on / off an RF signal in the active transceiver module, and an on / off switch for an RF signal to the front end. A transceiver for radar, comprising a second switch for 3. An active transmission / reception module having a transmission / reception function for use in an active phased array radar, an RF (Radio Frequency) signal which is a composite output of the active transmission / reception module, and an IF (Intermediate Freq).
RF front end for converting to an RF signal, an IF amplifier for amplifying the output signal of the RF front end, and an output side of this amplifier, which prevents fluctuations in the reception gain and fluctuations in the noise level of the signal. An automatic noise level control circuit, a local signal generator for providing a local signal to a mixer constituting the front end, a first switch for turning on / off an RF signal in the active transmission / reception module, and an on / off switch for a local signal to the front end. A transceiver for radar, comprising a second switch for 4. An active transmission / reception module having a transmission / reception function for use in an active phased array radar, an RF (Radio Frequency) signal which is a composite output of the active transmission / reception module, and an IF (Intermediate Freq).
RF front end for converting to an RF signal, an IF amplifier for amplifying the output signal of the RF front end, and an output side of this amplifier, which prevents fluctuations in the reception gain and fluctuations in the noise level of the signal. An automatic noise level control circuit, a power supply for applying a voltage to an RF low noise amplifier in the RF front end, a local signal generator for providing a local signal to a mixer forming the front end, and an R in the active transceiver module.
A first switch for turning on / off the F signal, a second switch for turning on / off the power supply to the RF low noise amplifier in the RF front end, and a third switch for turning on / off the local signal to the RF front end are provided. A transmitter / receiver for radar, characterized in that 5. An active transmission / reception module having a transmission / reception function used in an active phased array radar, an RF (Radio Frequency) signal which is a composite output of the active transmission / reception module, and an IF (Intermediate Freq.
RF front end for converting to an RF signal, an IF amplifier for amplifying the output signal of the RF front end, and an output side of this amplifier, which prevents fluctuations in the reception gain and fluctuations in the noise level of the signal. An automatic noise level control circuit, a power supply for applying a voltage to an RF low noise amplifier in the front end, a local signal generator for providing a local signal to a mixer forming the front end, and an RF signal in the active transceiver module. A first switch for turning on / off the power supply, a second switch for turning on / off the power supply to the RF low noise amplifier in the RF front end, and a third switch for turning on / off the RF signal to the RF front end. Characteristic radar transceiver. 6. An active transmission / reception module having a transmission / reception function for use in an active phased array radar, an RF (Radio Frequency) signal which is a composite output of the active transmission / reception module, and an IF (Intermediate Freq).
RF front end for converting to an RF signal, an IF amplifier for amplifying the output signal of the RF front end, and an output side of this amplifier, which prevents fluctuations in the reception gain and fluctuations in the noise level of the signal. An automatic noise level control circuit, a local signal generator that gives a local signal to a mixer that constitutes the RF front end, a first switch that turns on and off the RF signal in the active transceiver module, and an RF signal to the RF front end. A radar transceiver comprising: a second switch for turning on / off the switch and a third switch for turning on / off a local signal to the RF front end. 7. An active transmission / reception module having a transmission / reception function used in an active phased array radar, an RF (Radio Frequency) signal which is a composite output of the active transmission / reception module is amplified, and an IF (Intermediate Frequency) is used.
RF front end for converting to an RF signal, an IF amplifier for amplifying the output signal of the RF front end, and an output side of this amplifier, which prevents fluctuations in the reception gain and fluctuations in the noise level of the signal. An automatic noise level control circuit, a power supply for applying a voltage to an RF low noise amplifier constituting the active transceiver module, a local signal generator for providing a local signal to a mixer constituting the RF front end, and an active transceiver module in the active transceiver module. A first switch for turning on / off the RF signal, a second switch for turning on / off the power supply to the RF low noise amplifier in the RF front end, a third switch for turning on / off the RF signal to the RF front end, and RF
A radar transceiver, comprising a fourth switch for turning on / off a local signal to the front end.