JPH054353Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a microwave receiver that receives microwaves, and particularly relates to a local oscillation circuit.

[Conventional technology]

Conventional microwave receivers are highly sensitive, wideband receivers that receive microwaves emitted from a microwave transmission source, and can be roughly divided into two types of circuit configurations as shown below.

First Conventional Example This is a superheterodyne reception system having a wide intermediate frequency band, and the high frequency circuit is composed of an antenna section, a chopped microwave local oscillator, a microwave frequency mixer, and a wide band intermediate frequency amplifier. The microwave local oscillator is chopped at its cycle by a clock oscillator so that the microwave receiver can easily distinguish between signal waves and unnecessary waves. A circuit is required to cancel the .

The reason for chopping the microwave local oscillator is
When a small portion of the local oscillation force of other superheterodyne microwave receivers leaks outside and is received by this microwave receiver, the continuously emitted target wave and other super This is to facilitate identification from part of the local oscillation force from a heterodyne microwave receiver.

Next, this first conventional example will be explained in more detail. In Fig. 2, the chip clock generator 1
The waveform 3 generated at step 4 is used as a reference waveform for comparison of the phase detector 20 and also chops the period of the microwave local oscillator 13. The microwave captured by the electromagnetic horn type antenna 11 becomes an intermediate frequency by inputting it to the microwave mixer 12 together with the local oscillation output from the microwave local oscillator 13. The intermediate frequency is amplified by a wideband intermediate frequency amplifier 16 and amplitude detected by an amplitude detector 17.

Incidentally, the noise figure and conversion loss of the microwave diode used in the microwave mixer 12 are largely dependent on the local oscillation power as a high frequency bias. In the conventional method, however, the microwave local oscillation is chopped, so that each parameter of the microwave diode changes significantly, and as a result, a low amplitude waveform 5 appears when there is no signal.

At this time, when there is no signal, a low amplitude waveform 5 appears, so this is canceled out by the clock component cancellation circuit 18 using the waveform inversion circuit 15 and the clock component cancellation amount adjustment circuit 19. When the target reception signal wave is received, a waveform with a larger amplitude than the low-amplitude waveform when there is no signal appears, so the increased amplitude than the waveform when there is no signal is sent to the phase detector 20. If the phase of the waveform at this time matches the phase of waveform 3, it is assumed that the reception is correct, and the sound generating circuit 21 in the next stage is activated to output the sound from the sounding body 22.

Although the sensitivity is slightly inferior to the swept oscillator method described below, it is not expensive.

Second conventional example A double superheterodyne reception system is normally used using a swept oscillator system, and in order to improve sensitivity, the second intermediate frequency amplifier is set to a narrow band, but by constantly sweeping the second local oscillator, It is possible to achieve an apparent wide band with high sensitivity. However, it has to be expensive.

[Problem that the invention attempts to solve]

In the above conventional method of chopping local oscillation, the local oscillation output that enters the frequency mixer is interrupted by the clock, so the noise figure of the frequency mixer changes and noise from the frequency mixer is generated even when there is no signal wave from the antenna. In this case, modulated noise synchronized with the intermittent local oscillation appears, and a clock component also appears in the output after detection. In order to cancel this clock component, a clock whose phase has been changed by 180 degrees is added before the phase detector. Since the clock component appearing in the detection output is highly dependent on the environment such as the surrounding temperature, it is necessary to add an inverted clock larger than the clock component appearing in the detection output to provide a margin. Therefore, there was a problem in that the sensitivity was reduced by this margin.

The purpose of this invention is to provide higher sensitivity than conventional methods.
It is an object of the present invention to provide a microwave receiver with improved environmental dependence such as changes in ambient temperature.

[Means for solving the problem] The above problem is solved by using an antenna that captures microwaves,
A binary square wave generation circuit that generates and outputs a binary square wave, and a local oscillation circuit that inputs the binary square wave and makes the intermediate frequency fall within the band of the intermediate frequency amplifier at each predetermined period. a local oscillator that continuously outputs a binary local oscillation frequency such that the frequency and the intermediate frequency are out of the band of the intermediate frequency amplifier;
a frequency mixer that inputs a microwave signal from the antenna and an output from the local oscillator and outputs the intermediate frequency; an intermediate frequency amplifier that amplifies the intermediate frequency; and an amplitude detector for the amplified intermediate frequency. an amplitude detector; a phase detector that inputs the output from the amplitude detector and the binary square wave from the binary square wave generation circuit, performs phase detection, and outputs a phase detection output; The present invention is solved by providing a microwave receiver having a sound generating circuit which inputs the phase detection output from the 1000 and outputs an acoustic signal, and a sounding body which inputs the acoustic signal and generates a sound.

[Effect]

In the above configuration, the output of the local oscillator remains at a constant level without interruption, so the noise figure of the frequency mixer does not change, and when there is no microwave signal from the antenna, the noise from the frequency mixer does not change and after detection No clock component appears in the output.
The frequency of the local oscillator is shifted at each predetermined period so that one intermediate frequency falls within the band of the intermediate frequency amplifier, and the other shifts so that the intermediate frequency goes outside the band of the intermediate frequency amplifier, so that the When a microwave signal is present, an amplitude detection output that is chopped at a constant cycle is obtained for performing phase detection to distinguish between signal waves and unnecessary waves.

〔Example〕

An embodiment in which the present invention is applied to a wideband intermediate frequency system will be described below with reference to FIG.

First Embodiment The microwave captured by the electromagnetic horn type antenna 1 is sent to the microwave mixer 2, and the oscillation frequency of the quasi-microwave local oscillator 3 is changed by the signal shown by the waveform 1 from the binary square wave generation circuit 4. By controlling, binary oscillation frequencies are obtained alternately, which are multiplied by the frequency multiplier circuit 5 and inputted together with the local oscillation output to become an intermediate frequency. A binary intermediate frequency is obtained by alternately inputting binary local oscillation frequencies to the microwave mixer 2, and one of the binary intermediate frequencies is within the band of the wideband intermediate frequency amplifier 6, The other wave is outside the band of the broadband intermediate frequency amplifier 6, disappears, and does not appear as a detected output.

The intermediate frequency is amplified by a wideband intermediate frequency amplifier 6, amplitude detected by an amplitude detector 7, and the amplitude detection output is inputted to the next stage phase detector 8 together with the square wave from the binary square wave generating circuit 4. In the phase detector 8, if the phases of the amplitude detection output and the square wave match, it is regarded as a target wave and outputs the phase detection output to the sound generation circuit 9. The sound generating circuit 9 converts the phase detection output into an acoustic signal, and the sounding body 10 outputs it as sound.

The microwave local oscillation output always exists even if its oscillation frequency changes, so the operating conditions of the microwave mixer 2 do not change significantly, and the change in the noise figure of the microwave mixer 2 is also small, so the antenna The clock components that appear in the detection output when there is no input to the detector are also significantly reduced.

This eliminates the need for a clock component cancellation circuit used in the conventional system, improving sensitivity and simplifying the circuit configuration. Furthermore, environmental dependence such as changes in ambient temperature is also improved.

Furthermore, by using the quasi-microwave local oscillator 3 and the frequency multiplier circuit 5, it is possible to oscillate at a frequency extremely lower than the target reception frequency range, so an inexpensive transistor can be used as the oscillation element, which is unsuitable due to large dielectric loss. Oscillation can be easily achieved using a glass epoxy substrate called . Note that Teflon materials, sapphire materials, ceramic materials, etc. that can be used in the target reception frequency range are several to ten times more expensive than glass or epoxy materials.

Second Embodiment When the present invention is applied to a swept oscillator system, the binary square wave generation circuit 4 is replaced with a sawtooth wave generation circuit (see waveform 5 in FIG. 1), and the wideband intermediate frequency amplifier 6 is replaced with a narrow waveform. By using a band intermediate frequency amplifier and using a phase detector as the amplitude detector 7, a single superheterodyne system having equivalent sensitivity can be achieved at a low cost.

[Effect of idea]

According to the present invention, since the frequency of the local oscillator is shifted at predetermined intervals, the output of the local oscillator remains at a constant level without interruption, and therefore the change in the noise figure of the frequency mixer is minute, so the detected output does not change. There is no clock component that appears, and a circuit for canceling the clock component is not required, which improves sensitivity and simplifies the overall circuit configuration. Furthermore, environmental dependence such as changes in ambient temperature is also improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a wideband intermediate frequency microwave receiver type according to an embodiment of the present invention, Fig. 2 is a block diagram of a conventional wideband intermediate frequency microwave receiver type, and Fig. 3 is a block diagram of a conventional wideband intermediate frequency microwave receiver type. FIG. 3 is a waveform diagram of each part of the embodiment of the present invention. 1... Electromagnetic horn type antenna, 2... Microwave mixer, 3... Quasi-microwave local oscillator, 4...
Binary square wave generation circuit, 5... Frequency multiplier circuit, 6
... wideband intermediate frequency amplifier, 7 ... amplitude detector,
8... Phase detector, 9... Sound generation circuit, 10...
...pronunciation body.

Claims (1)

[Scope of utility model registration request] an antenna that captures microwaves; a binary square wave generation circuit that generates and outputs a binary square wave;
A square wave of a value is input, and at every predetermined period, one is a local oscillation frequency such that the intermediate frequency falls within the band of the intermediate frequency amplifier, and the other is a binary value such that the intermediate frequency goes outside the band of the intermediate frequency amplifier. a local oscillator that continuously outputs a local oscillation frequency of , a frequency mixer that inputs the microwave signal from the antenna and the output from the local oscillator and outputs the intermediate frequency, and the intermediate frequency that amplifies the intermediate frequency. a frequency amplifier, an amplitude detector that detects the amplitude of the amplified intermediate frequency, and inputs the output from the amplitude detector and the binary square wave from the binary square wave generating circuit, performs phase detection, and detects the phase. A microwave comprising a phase detector that outputs a detection output, a sound generation circuit that inputs the phase detection output from the phase detector and outputs an acoustic signal, and a sounding body that inputs the acoustic signal and generates sound. Receiving machine.