JPS62112086A - Fmcw radar - Google Patents

Abstract

PURPOSE:To decrease the number of components while maintaining an automatic level function by feeding the output signal of a receiving mixer to a controller and adjusting the output level of a transmitted wave with a level control signal outputted by the controller. CONSTITUTION:The level of an FM transmitted wave outputted from an FM oscillator 1 is adjusted by a level adjusting means 3. Its adjustment output is branched by a directional coupler 5 and transmitted from an antenna 11 through a circulator 10. The reflected wave of this transmitted wave is received by the same antenna 11 and the received wave and the other branch output of the directional coupler 5 are frequency-mixed by the receiving mixer 6. The output of this receiving mixer 6 is inputted to a signal processing part 9 and also fed back to the driver controller 8, thereby controlling the level adjusting means 3 with the level control signal outputted by the controller 8. Thus, neither a directional coupler for level adjustment nor a level detector is required.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to FM (frequency modulation), CW (Consta
The present invention relates to an ntWave (continuous wave) type radar, and particularly to one in which an automatic level adjustment section of a transmitted wave is simplified.

[Conventional technology]

FIG. 2 shows a block diagram of the configuration of a conventional FMCW radar. In FIG. 2, an FM-modulated transmission wave is output from an oscillator 1, and is input to an attenuator (hereinafter referred to as an attenuator) 3 via an isolator 2 for electrical insulation. This attenuator 3, the directional coupler 4 provided at the next stage, the level detector 7, and the driver controller 8 form an automatic level adjustment circuit for the output of the transmitted wave.

That is, a part of the transmission wave output from the attenuator 3 is branched by the directional coupler 4, and a feedback signal is fed back to the attenuator 3 via the level detector 7 and the driver controller 8, whereby the transmission wave output signal The level is automatically adjusted to remain constant.

The transmitted wave thus adjusted to a constant level is sent to the next directional coupler 5 via the directional coupler 4. This directional coupler 5 is for branching a part of the transmitted wave and using the part of the transmitted wave as a local oscillation signal. The transmission wave output from the directional coupler 5 is sent to the circulator 1o. The circulator 10 determines the flow direction of the transmitted wave when the transmitted wave is transmitted from the antenna 11 for distance measurement,
This is for receiving the reflected wave of the transmitted wave from the ground surface, etc., and switching the flow direction of the received wave and the received wave for extracting the beat wave caused by the local signal. That is,
During reception, the received wave received from the antenna 11 (
The reflected wave) is inputted to the receiving mixer 6 via the circulator 10, and the local oscillation signal (part of the transmitted wave) from the directional coupler 5 is inputted. Note that if the transmitting antenna and the receiving antenna are used separately, the circulator 10 is not necessary and the receiving antenna can be directly connected to the receiving mixer 6.

The reception mixer 6 performs frequency mixing of the local oscillator signal and the received wave. A beat signal (beat frequency signal) fb is generated by this frequency mixing. This beat signal fb changes depending on the round trip time from when the transmission wave is emitted until it is reflected by the ground surface or the like. Therefore, this beat signal fb
By measuring the frequency of the FMCW radar, it is possible to measure the distance, such as the altitude, from the installation position of the FMCW radar to the target object (ground surface, etc.). The signal processing unit 9 performs signal processing to measure the frequency of the beat signal fb.

[Problem that the invention seeks to solve]

In the above FMCW radar, the automatic level adjustment circuit is constituted by a loop of attenuator 3, directional coupler 4, level detector 7, and driver controller 8.

As a result, there are two directional couplers (4 and 5) in the transmit loop.
A level detector 7 is provided in series to detect the signal level of the transmitted wave. The presence of these directional couplers causes deterioration of frequency band characteristics, and the presence of level detectors also causes deterioration of characteristics. This leads to an overall deterioration of the characteristics of the entire radar, and since the number of parts increases, it is inevitable that the device will become larger.

Further, when the time interval between the transmitted wave and the received wave is short (the distance is short), the influence of the above characteristic deterioration is large, leading to deterioration of resolution.

Therefore, the present invention provides an FMCW radar that can omit the directional coupler and level detector for the automatic level adjustment circuit, still enable automatic level adjustment, and can be made smaller and lighter by reducing the number of parts. The purpose is to

[Means for solving problems]

In order to achieve the above object, an FMCW radar according to the present invention includes an FM oscillator that outputs a frequency modulated transmission wave, a level adjustment means that adjusts the output level of the transmission wave, and a transmission wave that is output from the level adjustment means. a directional coupler that branches and outputs a part of the directional coupler, an antenna that transmits the output of the transmitted wave from the directional coupler, and a circulator that outputs the received wave from the antenna that receives the reflected wave of the transmitted wave and the direction a receiving mixer that performs frequency mixing by mixing a part of the transmitted wave branched from the frequency coupler; and a controller that outputs a level control signal to the level adjusting means using the output signal of the receiving mixer as a feedback input. It is characterized by the fact that it is equipped with

According to the configuration of the present invention described above, the automatic adjustment circuit for the signal level of the transmission wave is configured by the level adjustment means, the directional coupler, the reception mixer, and the controller, and the controller converts the output signal of the reception mixer into a feedback signal. The level 5I adjustment means will be controlled as follows. In this case, since the output signal of the reception mixer includes a part of the transmission wave branched from the directional coupler, fluctuations in the signal level of the transmission wave directly become fluctuations in the output signal level of the reception mixer. appears. Therefore, the output signal of the reception mixer can be used as a feedback signal, and no problems occur in level adjustment due to this. On the other hand, with this configuration, there is no need for a dedicated directional coupler for level adjustment as in the past, and the level detector can be omitted, resulting in a reduction in the number of component parts and downsizing of the device. Weight reduction can be achieved.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

Fig. 1 shows an embodiment of the FMCW radar according to the present invention. In FIG. 1, the same parts as in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, the difference from the conventional example in FIG. 2 is that the directional coupler 4 and level detector 7 in FIG. 2 are omitted;
The point is that the feedback signal to the driver controller 8 is branched and extracted from the output end of the reception mixer 6. As a result, the automatic level adjustment circuit in this embodiment is constituted by a feedback loop including the attenuator 3, the directional coupler 5, the receive mixer 6, and the driver controller 8.

The automatic level adjustment operation of the transmitted wave in this case is as follows. That is, a part of the transmission wave output from the attenuator 3 is branched by the directional coupler 5, inputted to the reception mixer 6 as a local oscillation signal, and frequency-mixed with the reception wave from the circulator 10. A beat signal fb is output from the reception mixer 6, but this beat signal fb includes a part of the transmitted wave, so fluctuations in the signal level of the transmitted wave directly appear as fluctuations in the beat signal fb. . A control signal is input to the attenuator 3 to cancel this variation by inputting it to the I-river controller 8 in order to give negative feedback to this variation, so that the signal level of the transmitted wave is always maintained constant.

In the above explanation, the control signal from the driver controller 8 is input to the attenuator 3, but this is an example in which the attenuator 3 is understood as a level adjustment means. In addition, an output adjustment means (for example, an amplifier circuit) is provided at the output stage of the oscillator 1, and a control signal is applied to this adjustment means to adjust its output level (
In the case of an amplifier circuit, the amplification degree) may be adjusted, and the attenuator 3 may be omitted.

Next, an example in which the above configuration is applied to a microwave level meter will be explained as an example of actual application. In Figure 3,
The parts corresponding to each element in FIG. 1 will be described below with the same reference numerals assigned. YIG (yttrium) is used as the oscillator 1.
A wide 4JF range is achieved using an oscillator using an iron-garnet (iron-garnet) crystal, an attenuator using a PIN diode is used as the attenuator 3, and a 10 dB directional coupler 5 is used.
A coupler is used, and an operational amplifier is used as the driver controller 8. C is a capacitor for cutting direct current. The level reference signal V ref is given to one input terminal of the driver controller 1-roller 8, and the beat signal fb from the reception mixer 6 is given to the other input terminal, and the value of the difference between them is sent to the PIN attenuator 3. Given.

[Effects of the Invention] According to the configuration of the present invention described above, the automatic adjustment circuit for the signal level of the transmission wave is constituted by the level adjustment means, the directional coupler, the reception mixer, and the controller, and the controller is configured to control the reception mixer. The level adjustment means is controlled using the output signal as a feedback signal. In this case, since the output signal of the reception mixer includes a part of the transmission wave branched from the directional coupler, fluctuations in the signal level of the transmission wave directly become fluctuations in the output signal level of the reception mixer. I'm cursed. Therefore, the output signal of the reception mixer can be used as a feedback signal, and level adjustment problems will not occur due to this. On the other hand, with this configuration, there is no need for a dedicated directional coupler for level adjustment as in the past, and the level detector can be omitted, reducing the number of component parts and making the device more compact. , achieving weight reduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the FMCW radar according to the invention, FIG. 2 is a block diagram showing an example of a conventional FMCW radar, and FIG. 3 is a circuit diagram showing a specific example of the invention. 1... Oscillator 2... Isolator 3... Attenuator 4... Directional coupler 5... Directional coupler 6... Reception mixer 7... Level detector 8... Driver controller 9... Signal processing Part 10...Circulator 11...Antenna

Claims (1)

[Claims] an FM oscillator that outputs a frequency modulated transmission wave; a level adjustment means that adjusts the output level of the transmission wave; and a directional coupler that branches and outputs a part of the transmission wave output from the level adjustment means; An antenna that transmits the output of the transmitted wave from the directional coupler, and a circulator that mixes the received wave from the antenna that received the reflected wave of the transmitted wave with a part of the transmitted wave branched from the directional coupler. and a controller that outputs a level control signal to the level adjustment means by using the output signal of the reception mixer as a feedback input.
CW radar.