JPH0458177A - Fm radar - Google Patents

Abstract

PURPOSE:To give transmitted electric power to be a constant frequency response characteristic by receiving only the electric power of a side lobe as to electric power radiated from a transmitting antenna by using a monitor antenna having the same frequency characteristics with a receiving antenna, feeding the received signal of the monitoring antenna back negatively and controlling the transmitted electric power. CONSTITUTION:The electric power ratio of the main lobe and side lobe and the sent and received electric power ratio of the transmitting antenna ANTS and monitoring antenna ANTM are constant values which are determined corresponding to various elements and structure of a device in operation once they are determined, and the transmitted electric power is received at a constant ratio by the monitoring antenna ANTM having the same frequency characteristics with the receiving antenna ANTR. Therefore, a negative feedback loop wherein both the antennas ANTS and ANTR operate complementarily to flatten the frequency characteristics of the signal obtained with the output of the monitoring antenna ANTM is constituted to obtain a constant electric power control loop whose feedback constant is constant. Consequently, the transmitted electric power can be improved so as to have constant response characteristics.

Description

[Detailed Description of the Invention] [Field of Application in Industry A] The present invention is an FM radar that monitors the sidelobe power of the transmission output and provides negative feedback to the received power and the reference signal for beat detection. This relates to technology for flattening the frequency characteristics of.

[Prior art] In an FM radar, a part of the transmitted signal is used as a reference signal, and distance information to the target is obtained based on a beat signal obtained from the signal reflected from the target and the reference signal. ing.

In this case, if the hardware of each part constituting the radar equipment has unique frequency characteristics, the amplitude of the transmission power will vary due to FM modulation. Furthermore, the fact that the hardware has frequency characteristics similarly affects the amplitude fluctuations on the received signal returned from the target.

These amplitude fluctuations cause the generation of a signal having a frequency component other than the desired beat frequency, which includes distance information to the target, due to interference with the desired beat signal.

Further, the interference between the unnecessary signal generated in this way and the desired beat signal also generates a signal with a new frequency component. Signals having frequency components other than these required beat frequencies are unnecessary and disturbing.

The frequency characteristics of the hardware, which causes amplitude fluctuations, do not vary depending on circumstances such as changes in ambient temperature and power supply voltage.

For these reasons, the situation in which a signal with a frequency component other than the required beat frequency is generated due to the frequency characteristics of the hardware becomes extremely complicated.

In the end, the influence of signals with frequency components other than the required beat frequency causes problems such as deterioration of the accuracy of the detection ratio S, decrease in receiving sensitivity, and increase in processing time.

[Problem to be solved by the invention] Regarding the frequency characteristics of hardware, it is of course possible to take measures to improve each part, but it is also important to take measures to improve the frequency characteristics of each part. It has been difficult to achieve flat frequency characteristics for each part and the device as a whole due to irregularities in the frequency characteristics of the individual parts constituting each part.

The present invention has been made in view of these problems, and by improving the frequency characteristics of the device as a whole, it is possible to improve the frequency characteristics of the device as a whole.
The purpose is to suppress the occurrence of problems.

[Means for Solving the Problems] The present invention uses a monitoring antenna having the same frequency characteristics as the receiving antenna, receives only sidelobe power of the power radiated from the transmitting antenna, and receives the received signal of the monitoring antenna. By controlling the transmission power through negative feedback, the transmission power is configured to have a constant frequency response characteristic, and the reference signal for obtaining the beat signal, which is the basis of distance information, is transmitted through the negative feedback circuit. The frequency characteristics present in the signal are extracted from a portion of the flattened transmission power.

[Operation] In this invention, since the frequency characteristics of both the monitoring antenna and the receiving antenna are the same, the signal amplitude characteristics at the frequency of the received signal reflected from the target and the reference signal can be made the same. .

In addition, the power ratio between the main lobe and the side lobe and the power ratio between the transmitting antenna and the monitoring antenna are fixed values that are determined according to the specifications and structure of the implementation device, and are the same as those of the receiving antenna. Since the transmission power is taken in at a fixed ratio by the monitoring antenna with frequency characteristics, a negative feedback loop is created in which both antennas act complementary to each other and flatten the frequency characteristics of the signal obtained from the output of the monitoring antenna. By configuring this, it operates as a constant power control loop with a constant feedback constant.

By forming a negative feedback loop, the frequency characteristics of the implementation device are improved, and the transmission power is improved to have a constant response characteristic.

Furthermore, since the received power returned from the target has the same frequency characteristics as the transmitted power, the frequency characteristics of the output signal of the receiving antenna are flattened. Furthermore, the reference signal for obtaining the beat signal does not depend on frequency because it uses a part of the signal constituting a negative feedback circuit that flattens the frequency characteristics.

[Implementation example] FIG. 1 is for explaining the invention in detail.

In FIG. 1, an FM modulation oscillator FMMOD generates a carrier wave signal and FM modulates the carrier wave signal in accordance with a sweep signal generated by a sweep signal generator 5PGN. The FM modulated signal passes through a variable attenuator ATTN and is amplified to a suitable amplitude by MP to a power amplifier, and then sent to a transmitting antenna AN.
It is sent from the TS to the space.

NTR the signal reflected from the target to the receiving antenna
The received signal is received by the combiner COMB and combined with the signal from the monitoring antenna 8NTM, which is subjected to mixed detection by the mixed detector DET1 and then passed through the low-pass filter LPF to obtain the required beat signal ω6.

Here, in the vicinity of the transmitting antenna ANTS, a monitoring antenna ANTM having the same frequency characteristics as the frequency characteristic of the receiving antenna NTR is installed at a position where only the sidelobes of the transmit signal are received.
is the provision. The signal from the side lobe of the transmission power received by the monitoring antenna ANTM is branched by the distributor DIST, a part of which is sent to the power detector DET2, and the detected voltage 2 is input to the differential amplifier DEF8. The differential amplifier DEFA has the base! as another input. $! Reference voltage 3 from voltage generator REFV is input. The differential amplifier DEFA amplifies the control voltage V to a voltage proportional to the difference between the reference voltage vR and the detection voltage 1. and input it into the variable attenuator ATTN.

The variable attenuator ATTN determines the magnitude and polarity of the input voltage vc from the differential amplifier DEFA (the voltage V entering the differential amplifier DEFA from the power detector DET2, and the reference voltage generator RE).
The voltage is generated from the FM modulator FMMOD so that the pressure power (0 point) of the monitoring antenna ANTM is constant based on the reference voltage V or I that enters the differential amplifier DEFA from FV (indicating which is larger). act as a variable attenuation function to control the amplitude of the carrier signal.

Transmitting antenna ANTS, monitoring antenna ANTM, distributor Dr
A loop formed by ST, power detector DET 2, differential amplifier DEFA, variable attenuator ATTN, and power amplifier AMP forms a feedback circuit.

Since the divider DIST and the power detector DET2 are composed of passive elements, it is possible to flatten the frequency characteristics and it is independent of temperature fluctuations and power supply fluctuations, and the received power of the monitoring antenna ANTM is V , is proportional to .

Furthermore, in the negative feedback circuit, the absolute values of ■2, v, and l are controlled to be equal, so the received power of the monitoring antenna ANTM is vR.
It is a constant value proportional to .

In addition, the other part of the signal captured by the monitoring antenna ANTM and entered into the distributor DIST is passed through the isolator 15OL to prevent backflow, and then entered into the combiner COMB, and the signal reflected from the target is Used as a reference signal for beat detection.

Also, distributor DIST, isolator 15OL, combiner C
Since the OMB is composed of passive elements, it is possible to flatten the frequency characteristics, and since it does not depend on temperature fluctuations or power supply fluctuations, the reference signal obtained by the combiner COMB is proportional to the output signal of the monitoring antenna ANTM. When this happens and the constant power negative feedback loop operates to keep the power of the output signal of the monitoring antenna NTM constant, the frequency characteristics of the reference signal are also flattened.

Furthermore, the received signal reflected from the target has a constant frequency response characteristic, but the output signal of the receiving antenna ^NTR has the same frequency characteristic as the output signal of the monitoring antenna ANTM, and a constant power negative feedback loop is activated. Surveillance antenna A
When the power of the NTM output signal (point 0) is constant, the frequency characteristic of the power of the output signal (point b) of the receiving antenna ANTR is also flattened.

For this reason, the reference signal manually input to the combiner COMB and the output signal of the receiving antenna input NTR are combined with their frequency characteristics flattened, and these combined signals are further multiplied by DET 1 of the mixed detector to generate a low pass filter LP
Only the required beat frequency ω is extracted through F.

FIG. 2 conceptually explains the arrangement relationship between the transmitting antenna ANTS and the monitoring antenna NTM.

The frequency characteristics of the surveillance antenna ANTM are similar to that of the receiving antenna ANTM.
Use one with the same frequency characteristics as the TR.

Then, the axis (electrical axis) of the monitoring antenna ANTM is aligned with the axis (electrical axis) of one of the side lobes of the transmitting antenna ANTS, and the position relative to the transmitting antenna input NTS is kept constant. Note that a, b, and c in FIG. 2 correspond to the same symbols in FIG. 1, respectively.

The present invention can also be implemented when the transmitting antenna and the receiving antenna are shared.

In this case, as shown in Figure 3, the relative positions of both are fixed so that the sidelobe power is received by the monitoring antenna type NTM, which has the same frequency characteristics as the NTC with the shared antenna. Circulator CI to NTC
The same function can be obtained by connecting the RL and separating the carrier signal path and the received signal path. Note that the circulator CIRL can also be made by flattening the frequency characteristics.

Further, a, b, and c in FIG. 3 correspond to the same symbols in FIG. 1, and other components can be understood by referring to those in FIG. 1.

[Effects of the Invention] The present invention performs monitoring using sidelobe signals in transmission power that are generally unnecessary or harmful, and does not require special measures in circuit configuration for monitoring. The surveillance antenna is installed to receive only side lobes, so it does not pose any obstacle to the main lobe.

Furthermore, since the monitoring antenna is included in the negative feedback loop, the monitoring action and the flattening of the frequency characteristics of the received power are performed extremely stably.

Furthermore, since the reference signal power in the negative feedback loop is used to obtain the beat signal, the frequency characteristics can be flattened extremely stably. The beat frequency obtained by mixed detection using the flattened received power and the reference signal power has extremely little unnecessary spectrum.

Note that the present invention can be implemented using a continuous wave method, or by using a pulse wave method within the time response range of a constant power negative feedback loop, and the same effect can be achieved in either case. .

As described above, the reduction of unnecessary spectrum results in improved reception sensitivity, extended detection distance, and improved ranging accuracy.
Significant effects can be expected, such as improved ability to identify multiple targets, improved transmission power efficiency, and shortened IA darkening time.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 each provide a detailed explanation of the present invention. Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram showing a part of what is shown in Fig. 1, and Fig. 3 is a block diagram showing a part of what is shown in Fig. 1. FIG. 7 is a partial configuration diagram of another embodiment shown in place of the configuration. (Main symbols) SPGN...Sweep signal generator FMMOD...FM modulation oscillator^TTN...Variable attenuator (:OMB...Synthesizer DIST...Distributor LPF...Low pass filter DET2...Power detector REFV...Reference voltage generator 8NTR...Receiving antenna ω,...Beat signal ^NTC...Antenna for transmitting and receiving 15OL...Isolator AMP...Power amplifier DETI・...Mixed detector DEF^...Differential amplifier^NTS...Transmitting antenna ANTM...Monitoring antenna (:IRL...Circulator Figure 2, Figure 3, and 4 others)

Claims (1)

[Claims] 1. Sidelobe power in the transmitted power is received by a monitoring antenna having the same frequency characteristics as that of the receiving antenna,
F characterized in that a negative feedback circuit is configured to use the received power to obtain received power with flat frequency characteristics.
M radar. 2. A part of the transmitted power received by the monitoring antenna and present in the negative feedback circuit and whose frequency characteristics have been flattened is used as a reference signal when obtaining the beat signal from the received signal from the target. FM according to claim 1
Radar.