JPH0227285A - Sampling receiver - Google Patents

Abstract

PURPOSE:To provide an STC system of a wide dynamic range by mounting an STC signal generator for generating a sensitivity time control STC signal in synchronous relation to a timewise stretched waveform signal to supply the same to a voltage control variable attenuator. CONSTITUTION:The transmission timing from a strobe signal generating circuit 11 is supplied to a pulser 12 and a transmission pulse is supplied to a transmission antenna 14 on the basis of said timing through a balancer 13. The reflected wave of the transmission radiowave pulse is received by an antenna 15 and the receiving signal thereof is supplied to a voltage control variable attenuator 17 through a balancer 16. The output of the attenuator 17 is supplied to a sampler 21 through a limiting amplifier 18 and a high frequency amplifier 19 and sampled on the basis of the strobe signal from the circuit 11 by the sampler 21. The output of the sampler 21 is supplied to a high-pass filter 22. The synchronous signal with a timewise stretched waveform signal is supplied to an STC signal generator 23 from the circuit 11 to form the STC signal synchronous to the timewise stretched waveform signal and said STC signal is supplied to the attenuator 17 as a control signal.

Description

Detailed Description of the Invention "Industrial Application Field" This invention is applied to, for example, an underground radar, in which a repetitive waveform signal is received, and the repetitive waveform signal is converted into a strobe signal whose phase is sequentially shifted in synchronization with the received repetitive waveform signal. The present invention relates to a sampling receiving device that obtains a time-stretched waveform signal by sampling the signal. .

"Prior art" In underground radar, the level of the received wave is attenuated as the reception time for one transmission pulse is delayed, so the sensitivity time control n, so-called S, increases the reception sensitivity as the reception time is delayed.
TC is being conducted. STC in conventional Ikenaka radar
There were two types. One of them is to directly control the gain of the high frequency amplifier for several ns to 100 ns every transmission timing (for example, a period of 5 μs). Another method uses a sampling circuit in ground penetrating radar to extend the measurement time, for example, 200 ns with a transmission frequency of 200 Kpps.
By measuring the time of
Although the 8 ebs waveform signal is multiplied by about 100,000 times, STC is applied to the signal after time expansion.

The former method uses a gain control circuit in the first stage of the receiver, so STC with a large dynamic range is applied.
Since the gain is controlled in a short period of several ns to 100 ns at each transmission timing, the adjustment of the STC signal is delicate, and it also has the disadvantage of requiring a variable gain element with an ultra-high-speed response. In the latter method, STC is applied to the audio frequency signal after sampling, so the period is long, for example, 20 m5, and the STC signal is easy to control, but the range of the audio frequency signal itself is small. Therefore, there is a drawback that accurate STC cannot be applied in the signal saturation region.

"Means for Solving the Problem" In the present invention, a voltage-controlled variable attenuator is inserted in the first stage of the sampling receiver, and the sensitivity time control signal (STC signal) is transmitted to the ST in synchronization with the time-stretched waveform signal.
The sensitivity time control signal generated by the C signal generator is supplied as a control signal to the voltage controlled variable attenuator.

Embodiment FIG. 1 shows an embodiment in which the present invention is applied to an underground radar. The transmission timing from the Stroop signal generation circuit 11 is supplied to the pulser 12, from which the transmission pulse is sent to the transmission antenna 14 through the balun 13. Supplied. The reflected wave of the transmitted radio wave pulse is received by the receiving antenna 15, and the received signal is passed through the voltage-controlled variable attenuator 1 through the balun 16.
7. The output of the voltage-controlled variable attenuator 17 is supplied to a sampler 21 through a limiting amplifier and a high-frequency amplifier 19, and is sampled by the sampler 21 using the strobe signal from the strobe signal generating circuit 11. The output of the sampler 21 is a high-pass filter 2
2.

The transmission pulse is transmitted at a period of, for example, 5 μs as shown in FIG. 2A, and the reflected wave (including the direct wave) is received as shown in FIG. 2B. As shown in Figure 2C, when the strobe signal is time-stretched for 100 ns at 4096 sampling points, the first strobe signal coincides with the rising edge of the transmitted pulse, and the second strobe signal coincides with the rising edge of the transmitted pulse. On the other hand, the third strobe signal is delayed by 24.4 ps with respect to the rising edge of the transmission pulse, and the third strobe signal is delayed by 48.8 μs with respect to the rising edge of the transmitting pulse.The strobe signals are sequentially delayed in phase with respect to the rising edge of the transmitting pulse. In this way, a time-expanded received waveform signal is obtained. In this example, the period of the time-stretched waveform signal is 511s x 4096 = 2
It becomes 0.48ns.

In this invention, a sensitivity time control signal is generated in synchronization with a time-expanded received waveform signal. For this reason, a synchronization signal synchronized with the time-expanded waveform signal is generated from the strobe signal generation circuit 11, and this is supplied to the STC signal generator 23, which generates a sensitivity time control signal (STC signal) synchronized with the time-expanded waveform signal. is generated, and this STC signal is supplied to the voltage controlled variable attenuator 17 as a control n signal.

For example, as shown in FIG. 3, a transmission pulse 31 with a period of 5 μs
In contrast, a received signal 32 is obtained, and 200 minutes from its rise
When time expansion is performed using 4096 sampling points with ns as the measurement area, the STC signal 33 rises as shown in the figure, that is, -20 dB at the first sample point from the synchronization signal, -6 dB at the 1024th sample point, 2048 O at the th sample point
dB, OdB at the 4096th sample point. Then, the first received signal from the synchronization signal is curve 34.
The 1024th received signal is attenuated by 6 dB as shown by curve 35, from which the 1st sample point is sampled, and the 1024th received signal is attenuated by 6 dB as shown by curve 35, and this signal is sampled at the 1024th sample point. , the 2048th received signal is Od as shown by curve 36.
Attenuated by B, this signal is sampled at the 2048th sample point. In this way, each sampled signal becomes a sensitivity time controlled signal 37.

Such an STC signal can be generated by a sawtooth wave generating circuit as in the conventional case. It is also possible to configure as shown in FIG. In other words, the voltage curve characteristic that you want to vary is stored in the 170M41, the counter 42 is reset by the synchronization signal, and the counter 42 generates a clock! S
43, the ROM 41 is read out using this counted value as an address, and the output of the ROM 41 is converted into an analog signal by the D/A converter 44 and supplied as a control signal to the voltage-controlled variable attenuator. . In this way, S with arbitrary characteristics can be set depending on the contents stored in the ROM 41.
TC signals can be easily obtained.

Although there is the problem of saturation of the high frequency amplifier and the accompanying fluctuation of the DC level (zero level), as shown in Fig. saturation problem is solved. Also, fluctuations in the DC level can be detected using the sampler 21.
A high-pass filter (2001 (about z10ct)) is installed after the
By adding 22, the fluctuation can be removed.

"Effects of the Invention" As described above, according to the present invention, since the voltage-controlled variable attenuator is provided at the first stage of the receiving device, STC can be applied over a large dynamic range. 5TCIIJI
Since this is performed at a time-expanded timing, for example, 20.48 ns, its control characteristics can be easily and freely set, and stable operation can be expected. It is also possible to use a voltage controlled variable attenuator with a slow variable speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the invention, FIG. 2 is a diagram for explaining sampling reception, and FIG. 3 is an STC
FIG. 4 is a block diagram showing an example of an STC signal generator. Patent applicant: Koden Seisakusho Co., Ltd.

Claims (1)

[Claims] (1) In a sampling receiving device that receives a repetitive waveform signal and samples the repetitive waveform signal with a strobe signal whose phase is shifted sequentially in synchronization with the received waveform signal to obtain a time-stretched waveform signal, the first stage of the receiving device a voltage-controlled variable attenuator inserted in the STC; and an STC that generates a sensitivity time control signal in synchronization with the time-expanded waveform signal and supplies it to the voltage-controlled variable attenuator.
A sampling receiving device comprising a signal generator.