JPS6345574A - Signal detecting circuit of receiver - Google Patents

Abstract

PURPOSE:To prevent a signal other than signal components and noise from being received after a received signal is detected by locking a frequency signal inputted to a frequency converter so as to obtain an intermediate frequency signal according to whether or not the received signal is detected. CONSTITUTION:A D/A converter 17 generates a saw-tooth wave on the basis of a signal supplied from a microcomputer 16 and supplies it to a VCO 6. The VCO 6, on the other hand, supplies a frequency signal based upon the saw-tooth wave to a frequency mixer 5 and this signal is mixed with the output signal of a 1st intermediate frequency amplifier 4. Consequently, a 2nd intermediate frequency signal which is obtained is detected by a detector 8, whose output is detected synchronously by a synchronous detector 14 and then supplied to the microcomputer 16 through an A/D converter 15. When the output of the A/D converter 15 exceeds a prescribed value, a signal outputted to a D/A converter 17 is locked and the D/A converter 17 continues to receive only the same signal so as to apply a constant voltage to the VCO 6.

Description

[Detailed Description of the Invention] [Industrial Usage ¥P] This invention relates to a signal detection circuit for a receiver, and specifically relates to a signal detection circuit for a receiver. Regarding the red detection circuit.

[Prior Art] FIG. 4 is a schematic block diagram of a receiver in a conventional microwave radar, and FIG. 5 is a sweep waveform diagram of the Iζ receiver shown in FIG. 4.

First, with reference to FIGS. 4 and 5, the different types of reception in a conventional microwave radar will be explained. antenna 1
The microwaves received at the 1st frequency mixer 2 are given to the first frequency mixer 2. The first frequency mixer 2 mixes the received microwave and a local oscillation signal given from the local oscillator 3, and outputs a first intermediate frequency signal. This first intermediate frequency signal is amplified by a second intermediate frequency amplifier 4 and is applied to a -second frequency mixer 5. Sweep oscillator 11
is repeatedly swept with a sawtooth wave as shown in FIG. VCO
6 oscillates a signal according to the sawtooth voltage and supplies it to the second frequency mixer 5. The second frequency mixer 5 mixes the first intermediate frequency signal and the signal from the VCO 6 and provides the second intermediate frequency signal to the second intermediate frequency amplifier 7. An intermediate frequency amplifier 7 amplifies the second intermediate frequency signal and a detector 8
give to The detector 8 detects the second intermediate frequency signal,
The signal component is provided to an amplifier 9. Amplifier 9 amplifies the signal and displays it on display 10.

Detector 8 emits a sweep signal! ! The i-device 11 repeatedly sweeps a sawtooth wave as shown in FIG. 5, and transversely waves the signal component only at the moment of the sawtooth wave.

[Problems to be Solved by the Invention] As mentioned above, in conventional receivers, signal components are detected only during a moment when the sawtooth wave is swept, so it is difficult to receive the signal. After that, the signal continues to sweep, and there is a risk that other signals may be received afterwards, resulting in interference. Further, even if a noise component is received, the detector 8 directly detects the noise component, which has the disadvantage of poor sensitivity and poor S/N ratio.

Moreover, since the detected signal is simply amplified directly by the amplifier 9 and displayed on the display 10, there is a problem in that it is impossible to determine whether the signal component is increasing or decreasing.

Therefore, the main purpose of this invention is to be able to remove signals and noise caused by interference, and to improve S/N at high degrees.
It is an object of the present invention to provide a signal detection circuit for a receiver that can easily judge the tendency of increase and decrease of the signal. .

[Means for Solving the Problems] The present invention is a signal detection circuit for a receiver, and includes a voltage control circuit that generates a frequency signal according to a repetitively sweeping sawtooth wave.
An oscillator, a frequency converter that outputs an intermediate frequency signal based on the oscillation output of the voltage controlled oscillator and a received signal, an intermediate frequency amplifier that amplifies the intermediate frequency signal, and a detector that detects the output signal of the intermediate frequency amplifier. and a control means that repeatedly sweeps the sawtooth wave and stops the sweep of the sawtooth wave in response to the detector outputting the signal component to fix the oscillation frequency of the voltage controlled oscillator, and the detector outputs the signal component. and notifying means for notifying the detection of a signal in response to the control means determining that a signal has been detected.

[Operation 1] The signal detection circuit of the receiver according to the present invention is configured to stop the sweep in response to detecting a signal, so there is no risk of receiving signals or noise other than signal components, and the sensitivity can be increased. At the same time, it is possible to improve the S/N ratio.

Further, by taking a moving average of the detection signals, it is possible to grasp the tendency of increase/decrease in the signal and the rate of increase.

[Embodiments of the invention] FIG. 1 is a schematic block diagram of an embodiment of the present invention.

First, the configuration of an embodiment of the present invention will be described with reference to FIG. The antenna 1, the first frequency mixer 2, the local oscillator 3, the intermediate frequency amplifier 4, the frequency mixer 5, the VCO 6, and the intermediate frequency amplifier 7 are constructed in the same manner as in FIG. 4 described above. The second intermediate frequency signal amplified by the intermediate frequency amplifier 7 is given to the detector 8 via a band pass filter 12 having a bandwidth of 4 MH2.

The bandpass filter 12 removes noise components exceeding 4MH2. Detector 8 detects the received signal from which noise components have been removed, and provides the detected output to amplifier 13 .

Amplifier 13 amplifies the signal component and provides its output to synchronous detector 14 . The synchronous detector 14 synchronously detects a signal component based on the output of a D/A converter 17, which will be described later, and provides the output to the A/D converter 15. The A/D converter 15 detects the output of the synchronous detector 14, converts the signal component into a digital signal, and provides the digital signal to the microcomputer 16. When the output of the A/D converter 15 is not given, the microcomputer 16 repeatedly generates a digital signal for outputting a sawtooth wave and supplies it to the D/A converter 17.
The signal components converted into digital signals by the converter 15 are monitored to determine the tendency of increase or decrease in the received signal, and if there is an increase, the indicator 10 is turned on. The D/A converter 17 generates a sawtooth wave based on the digital signal given from the microcomputer 16, and supplies it to the VCO 6 and the above-mentioned synchronous detector 14.

FIG. 2 is a reception sweep waveform diagram shown in FIG. 1, and FIG. 3 is a flowchart for explaining the specific operation of an embodiment of the present invention.

Next, with reference to FIGS. 1 to 3, a specific operation of an embodiment of the present invention will be described.

Similarly to FIG. 4 described above, when the antenna 1 receives a microwave signal, the frequency mixer 2 mixes the local oscillation signal from the local oscillator 3 and the received signal to generate a first intermediate frequency signal. is output and applied to the intermediate frequency amplifier 4. At this time, the microcomputer 16 supplies the D/A converter 17 with a digital signal for generating a sawtooth wave a as shown in FIG. The D/A converter 17 converts the digital signal into an analog signal and provides a sawtooth wave to the VCO 6. The VCO 6 provides a frequency signal to the frequency mixer 5 based on the sawtooth wave. The frequency mixer 5 mixes the intermediate frequency signal given from the first intermediate frequency amplifier 4 and the output of the VCO 6,
A second intermediate frequency signal is provided to a second intermediate frequency amplifier 7.

The second intermediate frequency amplifier 7 amplifies the second intermediate frequency signal and supplies it to the detector 8 via the bandpass filter 12. By passing through the bandpass filter 12, noise components included in the signal components of the intermediate frequency signal are removed. Detector 8 detects the received signal and provides the detected output to amplifier 13 . The amplifier 13 amplifies the received signal and supplies it to the synchronous detector 14. Accordingly, the detector 14 synchronously detects the received signal and provides its output to the A/D converter 15. The microcomputer 16 determines whether or not there is sensitivity depending on whether the level based on the digital signal output from the A/D converter 15 is equal to or higher than a predetermined value.

If the output of the A/D converter 15 is below a predetermined level, the microcomputer 16 outputs a signal for generating a sawtooth wave to the D/A converter 17. In this way,
The microcomputer 16 continues sweeping the sawtooth wave until it receives a signal.

When the microcomputer 16 determines that there is sensitivity based on the output of the A/D converter 15, it performs the D/A conversion i.
? The digital signal for generating the sawtooth wave output to 317 is locked. As a result, the sawtooth sweep is stopped, as shown in the waveform shown in FIG. Since the sawtooth sweep is stopped, the D/A converter 17 provides a constant level of DC voltage to the VCO 6. The VCO 6 provides a frequency signal corresponding to the DC voltage to the frequency mixer 5. Therefore, at the time the sweep is locked, the same signal continues to be received. Then, the microcomputer 16 calculates the average amount of change in the output of the A/D converter 15 over a certain period of time.

That is, the microcomputer 16 is the A/D converter 1
The output of No. 5 is sampled, for example, 80 times, and the average value x of the amount of change is taken as a moving average. Then, based on the obtained moving average, it is detected whether the received signal tends to increase or decrease. If the level of the received signal is increasing, the indicator 10 is turned on, and if the level of the received signal is decreasing, the sawtooth sweep is unlocked.

[Effects of the Invention] As described above, according to the present invention, when the received signal is sensitive, the frequency signal generated from the voltage controlled oscillator is locked and the number of times the signal is detected is increased. Therefore, sensitivity can be improved and S/N ratio can be improved. For example, if a signal is input every 50μsec with a bandwidth of 4MH2 and the number of inputs is 8, the S/N improvement will be 1.
0101 o 9 dB. Furthermore, if the oscillation frequency of the voltage controlled oscillator is locked when the received signal is sensitive and the sweep speed is reduced to 1/10, the number of inputs becomes 80, and the S/N improvement is 10fLog80U19 d
B, 10dB11! It can be improved by 2 degrees. moreover,
By integrating the detected signals and taking a moving average, it is possible to accurately understand the increase, decrease, and rate of increase in the signal.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of an embodiment of the present invention. FIG. 2 is a sweep waveform diagram of FIG. 1. FIG. 3 is a flowchart for explaining the specific operation of one embodiment of the present invention. FIG. 4 is a schematic block diagram of a conventional receiver. FIG. 5 is a sweep waveform chart based on CO in FIG. 4. In the figure, 1 is an antenna, 2.5 is a frequency mixer, 3
is the local oscillator, 4.7 is the intermediate frequency amplifier, and 6 is the VCO1.
8 is a detector, 10 is a display, 12 is a bandpass filter, 13 is an amplifier, 14 is a synchronous detector, 15 is a Δ/D converter, 16 is a microcomputer, and 17 is a D/A converter. Figure 3 Figure 1 Figure 3

Claims (2)

[Claims] (1) A voltage controlled oscillator that generates a frequency signal according to a repetitively sweeping sawtooth wave, a frequency converter that outputs an intermediate frequency signal based on the oscillation output of the voltage controlled oscillator and the received signal, and the frequency converter an intermediate frequency amplifier that amplifies an intermediate frequency signal output from the intermediate frequency amplifier; a detector that detects the output signal of the intermediate frequency amplifier; and a detector that repeatedly sweeps the sawtooth wave and responds to the output of the signal component by the detector. , stop the sawtooth sweep,
A control means for fixing the oscillation frequency of the voltage controlled oscillator; and a notification means for notifying detection of a signal in response to the control means determining that the detector outputs a signal component. Receiver signal detection circuit. (2) The control means includes an A/D converter that converts the output signal of the detector into a digital signal.
a D-converting means, which repeatedly generates a digital signal for outputting the sawtooth wave, and generates the sawtooth wave in response to a value of the digital signal output from the A/D converting means being equal to or more than a predetermined value; a microcomputer that fixes the value of a digital signal for outputting the oscillator, and a D/A conversion means that converts the digital signal generated from the microcomputer into an analog signal and provides a sawtooth voltage to the voltage controlled oscillator. A signal detection circuit for a receiver according to claim 1.