JPH0250658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to a microwave detector that detects microwaves.

[Conventional technology]

Conventionally, microwaves have been used for various wireless communications, radars, etc., taking advantage of their characteristics. In line with this, various types of microwave detectors have been proposed that are simple devices that detect the arrival of microwaves at a certain point. For example, in a system in which moving objects are guided by microwaves, a microwave detector is required for each moving object, and the development of inexpensive and highly accurate microwave detectors is progressing. . Among these, in cases where a tuner that converts received microwaves to an intermediate frequency is operated intermittently and the output of the tuner is amplified by AC, a simple circuit consisting of only a tuner and an AC amplifier can reliably detect the arrival of microwaves. It was widely used because it can detect

[Problem that the invention seeks to solve]

However, even the microwave detectors described above are still not sufficient and have the following problems.

In conventional microwave detectors with a simple configuration, the tuner operates intermittently, so the connecting wave (hereinafter referred to as
When a CW signal (referred to as CW) is received, an AC signal corresponding to the operating cycle of the tuner is obtained. Therefore, the arrival of microwaves can be detected by amplifying this AC signal with an AC amplifier. However, with the advancement of communication technology and radar technology, methods of radiating microwaves intermittently or sporadically have been put into practical use, and if this type of microwave is to be received by the conventional models mentioned above, it is necessary to use a tuner. The output contains complex frequency components different from the operating period of the tuner, and may be impossible to detect using a simple AC amplifier.

The present invention has been made to solve the above problems, and has a simple and inexpensive configuration, and has a CW,
The purpose of the present invention is to provide a microwave detector that can accurately and reliably detect both intermittent waves and single waves.

Structure of the Invention [Means for Solving the Problems] The means configured by the present invention to solve the above-mentioned problems is provided in a microwave detector that receives microwaves and notifies the reception results of the microwaves. , a microwave receiving means for receiving the microwave; a frequency converting means for inputting the received signal of the microwave receiving means and operating intermittently to convert the received signal to an intermediate frequency; a detection means for enveloping detection of the output; a DC amplification means for DC amplifying the output of the detection means; superimposing means for feeding back to the input of the DC amplification means and superimposing it on the output of the detection means; sampling means for sampling the received output of the DC amplification means at a predetermined period while the frequency conversion means is operating; A microwave detection device comprising: a comparison device that compares the reception output with a reference voltage determined based on the reception output sampled by the sampling device; and a notification device that notifies the comparison result of the comparison device. Its gist is the machine.

[Effect]

The microwave detector of the present invention intermittently converts microwaves to an intermediate frequency and performs envelope detection as in the conventional method. However, the detected signal is amplified by the DC amplification means, and it does not matter what average value or frequency the signal has. Moreover, the input of this DC amplification means is not just a detection signal, but the amplification result of the difference between the output of the DC amplification means and the reference voltage during the period when the frequency conversion means is not operating is fed back and superimposed.

Further, the received output of the DC amplifying means is sampled by the sampling means at predetermined intervals, and the reference voltage determined based on the sampling value and the received output are compared by the comparing means. The results are notified by the notification means.

EXAMPLES Hereinafter, in order to explain the present invention more specifically, examples will be given and explained.

〔Example〕

FIG. 1 is a schematic block diagram of a microwave detector according to an embodiment, and FIGS. 2 and 3 show timing charts of voltage signals at various locations in the block diagram.

As shown in FIG. 1, the microwave detector of this embodiment first amplifies the microwave received by an antenna 10 with an RF amplifier 12, and then mixes it with the oscillation signal of a local oscillator 16 in a mixer 14 to generate an intermediate frequency signal. It uses the normal superheterodyne method to obtain the signal. However, the local oscillator 16 does not always operate in oscillation, but is configured to operate intermittently in response to a clock signal from a clock oscillator 18. Then, the signal from the mixer 14 is amplified by an intermediate frequency amplifier 20 and used for subsequent signal processing.

Figures 2A to 2D show the signals of each circuit related to the microwave reception mentioned above, and the voltage signals of the lines labeled A to D in Figure 1 are shown on the same time axis. There is. As is clear from the figure,
Even if the output A of the RF amplifier 12 is continuous to some extent, the output C of the local oscillator 16 is input to the mixer 14 only intermittently in accordance with the clock signal B of the clock oscillator 18, so that the intermediate frequency The output D of the amplifier 20 appears only when microwave reception and the output of the local oscillator 16 coexist.

The output of the intermediate frequency amplifier 20 is subjected to negative polarity envelope detection using a high-pass capacitor C1 and a grounded diode D1, and then is passed through a grounded charging/discharging capacitor C2 to an operational amplifier which is a direct current amplification.
Input to OP1. In this example, in order to obtain a sufficient amplification factor, the DC amplifier is configured with two stages, and after the first stage amplification value by the operational amplifier OP1 is drifted by a predetermined value via the Zener diode DZ, the second stage is further amplified. It is amplified using amplifier OP2. This amplified signal is input to the superimposition circuit and fed back to the operational amplifier OP1, and is also input to the operational amplifier OP3, which is a comparison circuit, and is guided to the next stage notification circuit.

First, the superimposition circuit will be explained. Arithmetic circuit
Among the outputs from OP2, the signals outputted after being switched by the switch circuit 22 are only the signals during the period when the local oscillator 16 is not operating. That is, a signal obtained by inverting the clock signal of the clock oscillator 18 by the inverter 24 is input to the switch circuit 22, and the internal circuit is turned on and off. Therefore, if the voltage at this time is smoothed by the smoothing capacitor C5, the voltage value input to the buffer OR4 will be such that no intermediate frequency signal is input to the input side of the two-stage DC amplifiers OP1 and OP2. This is the voltage when there is no signal. This voltage is
It is input to a comparator OP5 together with a predetermined reference voltage Vb set by dividing the power supply voltage Vcc, and the comparison result is fed back to the input of the operational amplifier OP1 and superimposed on the output of the intermediate frequency amplifier 20. This is to stabilize the output as a DC amplifier, and due to the configuration of the superimposition circuit as described above, the output of the DC amplifier is always at a certain predetermined voltage VD.
will be output based on the standard. This reference voltage VD is pulled in the negative direction only when the intermediate frequency amplifier 20 is producing an output, and has a value corresponding to the amplitude of the output signal from the intermediate frequency amplifier 20 at that time. only decreases.

With the above circuit configuration, the output as a DC amplifier is as shown in FIG. 2F.

Next, a description will be given of a circuit configuration at a later stage that accurately reports the presence of microwaves from an output as shown in FIG. 2F.

The switch circuit 26 is the switch circuit 22 described above.
However, the timing for turning on and off the internal circuit is determined by directly inputting the clock signal from the clock oscillator 18. Therefore, the signal transmitted to the operational amplifier OP3 by the switch circuit 26 becomes an intermittent signal synchronized with the operation of the local oscillator 16 (FIG. 2G).

On the other hand, a reference signal with which this signal is compared is a reference voltage Va obtained from a sampling circuit sampling the signal G similar to the above.
The sampling circuit is a peak hold circuit centered around the capacitor Ca, and the transistor Tra, which is supplied with base current from the buffer OP6 to which the signal G is input, outputs the capacitor Ca connected between its emitter and ground. Charge to the voltage of signal G. In addition, in order to execute this sampling timing only at predetermined synchronization, a switch circuit 28 is disposed between the emitter of the transistor Tra and the capacitor Ca, and a pulse oscillator
The switch circuit 2 is activated only under the AND condition in which outputs from both OP7 and the clock oscillator 18 are obtained.
The internal circuit of 8 is made conductive. That is, peak hold is performed on the capacitor Ca only at the timing when the signal G indicates the output during the microwave reception period and when the pulse output of the pulse oscillator OP7 is obtained.
As is clear from the above, the pulse oscillator OP7 determines the peak hold period, but as shown in FIG. Capacitor Co, which determines the oscillation time constant, outputs a high level output for a short period of time.
Ro ₁ and Ro ₂ are designed. In this example, the third
As shown in the figure, the constants of each element are determined so that 3TC=Ton and 10Ton=Toff. Therefore, the peak value of the signal G at that time is held in the capacitor Ca during the period Ton and when the clock is at the high level, and the hold value is held during the period Ton.
It will be updated every Toff.

In this way, the terminal voltage of the capacitor Ca, at which the peak value of the signal G is held, is applied to the voltage divider circuit 29 via the buffer OP8, where the slightly dropped voltage (△Va) is applied to the operational amplifier OP3.
is used as the reference voltage Va.

Since the reference voltage Va of the operational amplifier OP3 is a value dropped by △Va from the output of the signal G during the microwave reception period as described above, the comparison result between this reference voltage and the signal G is as shown in Figure 2 H. become. In other words, when the microwave is not being received, the output is always in the same oscillation state as the signal G, and when the microwave is being received and the output of the signal G is lower than the potential Va, it changes to a low potential state. (Second
Figure H).

As described above, the signal H whose voltage waveform reflects the presence of microwaves is then input to the base of the switching transistor Tr1, and controls the charging/discharging timing of the charging/discharging circuit consisting of the resistor R and the capacitor C10. It detects microwaves, and no signal is output to the base of the transistor.
If Tr1 is OFF, capacitor C10 is resistor R
Charging is started at a speed determined by the time constant CR, and when no microwave is detected, the transistor Tr1 is turned on and the capacitor C10 is instantly discharged (Fig. 2 I). That is,
If there is no microwave, the charging period of capacitor C10 is the period when the clock signal is not output.
Since it is limited to only TC, the voltage will never exceed VC (see Figure 2 I). Then, when the microwave is detected, the terminal voltage of the capacitor C10 continues to rise in proportion to the detection period and finally reaches the power supply voltage Vcc that suspends the resistor R.

As mentioned above, the voltage signal of capacitor C10, which changes based on the period of microwave detection, is input to two comparators OP10 and OP11, and is compared in magnitude with reference voltages VH and VL (<VH), respectively. Ru. Here, when the voltage signal of the capacitor C10 exceeds VL, the output of the comparator OP11 becomes a high potential, which further influences the output of the operational amplifier OP12 in the subsequent stage, and sends a predetermined signal to the selection circuit 30 to notify the The device 32 is driven to output a notification sound from the speaker SP1. (Figure 2 J). If the above-mentioned state continues and the voltage signal of the capacitor C10 finally reaches a high potential exceeding VH, the output of the comparator OP10 becomes high potential, turning the transistor Tr2 on and turning the selection circuit 30 on. By changing the input state and driving the annunciator 34 instead of the annunciator 32, a different notification sound is output from the speaker SP2.

That is, when the voltage waveform H reflecting microwave reception information is in a low voltage state, the capacitor C1
0 voltage increases, but if the low voltage state is for an extremely short period of time due to mere noise, the voltage will not exceed the reference voltage VL and no notification will be performed. However, if this continues for a certain period of time, it is determined that some kind of microwave signal is being received, and a notification is executed from the speaker SP1. Moreover, when the microwave detection period is long, the notification automatically switches to the speaker SP2 with a different tone, so whether the microwave arrives in CW or pulse wave mode, However, it is easy to identify.

As we explained the operation of each circuit in detail above,
The microwave detector of this embodiment has the following effects.

First, since the microwave detection result is DC amplified, it is possible to accurately detect whether the microwave is of any type, such as CW, intermittent wave, or pulse wave. Moreover, since the detection is announced with different tones depending on the microwave detection time, it is possible to easily distinguish even the radiation method of the incoming microwave. This makes it possible to select and detect the microwave signal that you really want to detect, even if you are in a location where a wide variety of microwaves coexist.

Second, high precision microwave detection is achieved and false alarms can be avoided. That is, in the embodiment described above, microwave detection is performed by peak-holding the signal G and comparing the signal G with the voltage Va whose value is slightly lowered. Therefore, even if noise occurs during the microwave reception, detection, and amplification process, or output fluctuations due to heat occur, such as changes in Gunn diode output, etc., the reference voltage Va is updated using that value. This ensures stable operation without causing false alarms.

In the above embodiment, envelope detection is of negative polarity, but positive polarity detection may also be used. In this case, normal changes such as designing the DC amplifier to always amplify negative voltage are made. Furthermore, it is not limited to the two types of notifications by speakers, but may be implemented in various ways without departing from the gist of the present invention, such as visual display or display of continuous period segments of multi-stage microwaves. good.

Effects of the Invention As described above in detail with reference to the embodiments, the microwave detector of the present invention amplifies intermittent microwave detection results using DC amplification means. Therefore, it is possible to accurately detect microwaves radiated by CW, intermittent wave, or pulse wave. Moreover, since the superimposing means operates so that the voltage of the DC amplifying means when there is no signal is constant, it is possible to receive extremely weak microwaves, and high sensitivity characteristics can be achieved.

In addition, even if the amplified signal of the DC amplification means changes due to temperature changes, the value is sampled and the reference voltage for comparison is updated, so there is no false alarm, and the microcontroller operates stably and with high precision. Can detect waves.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electric circuit of a microwave detector according to an embodiment, and FIGS. 2 and 3 are timing charts of signal waveforms at various parts of the embodiment. 10...Antenna, 14...Mixer, 16...
Local oscillator, 18...Clock oscillator, OP1,
OP2...Operation amplifier, 30...Selection circuit, SP
1, SP2...Speaker.

Claims (1)

[Scope of Claims] 1. A microwave detector that receives microwaves and notifies the reception result of the microwaves, comprising: a microwave receiving means for receiving the microwaves; and a reception signal of the microwave receiving means is input. and a frequency conversion means that operates intermittently to convert the received signal to an intermediate frequency; a detection means that performs envelope detection on the output of the frequency conversion means; and a DC amplification means that DC amplifies the output of the detection means; superimposing means for feeding back the amplification result of the difference between the output of the DC amplification means and a reference voltage during a period when the frequency conversion means is not operating to the input of the DC amplification means and superimposing it on the output of the detection means; sampling means for sampling the received output of the DC amplification means at a predetermined period during a period in which the conversion means is in operation; and comparing the received output with a reference voltage determined based on the sampled received output of the sampling means. 1. A microwave detector comprising: a comparison means for performing the comparison, and a notification means for notifying the comparison result of the comparison means.