JPH06186315A - Passive reception circuit - Google Patents

Abstract

PURPOSE:To provide a passive reception circuit that allows simultaneous use with an active sonar device, without requiring scale-up of the circuit. CONSTITUTION:A passive reception circuit, that comprises a band pass filter 41 that removes unwanted frequency included in input signal, an analogue-digital converter 42 that converts the output signal from the band pass filter into digital signal and a digital band pass filter 43 that removes unwanted frequency included in digital signal, are provided with a time change gain amplifier 11 that allows gain control, and when it is used together with, simultaneously, an active sonar device, input signal level is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passive receiver circuit used in a passive sonar device.

[0002]

2. Description of the Related Art Sonar devices include passive sonar devices,
There are active sonar devices and the like, and passive sonar devices and active sonar devices are often operated simultaneously.

As shown in FIG. 4, a passive receiving circuit of a conventional passive sonar device has a band pass filter (BP).
F) 41, analog / digital (A / D) converter 42,
And a digital band pass filter (BPF) 43. The same applies to the active reception circuit of the active sonar device.

In this passive receiving circuit, the BPF 41 removes the unnecessary frequency of the input passive received signal.
However, when the passive sonar device and the active sonar device are simultaneously operated, the reception band of the passive sonar device and the reception band of the active sonar device may be close to each other. In this case, the BPF 42 of the passive receiving circuit and the BPF of the active receiving circuit are forced to have the band characteristics as shown in FIG. 5A, and the active signal leaks to the passive receiving circuit side. So B
The passive reception signal output from the PF 41 is converted into a digital signal by using the A / D converter 42, and the unnecessary frequency including the active signal is converted by using the digital BPF 43 having the band characteristic as shown in FIG. 5B. I am trying to remove it further.

[0005]

When the conventional active receiver circuit is used at the same time as the active sonar device, the active signal is input to the BPF 41, but the level of this active signal is higher than that of the passive signal. Very expensive. Therefore, a signal in which a passive signal and an active signal are mixed as shown in FIG.
When input to the BPF 41, its output saturates and becomes as shown in FIG. That is, low level passive signals are masked and lost.

As described above, in the conventional passive receiving circuit,
When used at the same time as the active sonar device, the passive signal is masked, which makes it impossible to detect it.

In order to solve this problem, BP
Although it is possible to improve the band characteristic of F41, this method has a problem that the BPF becomes large.

An object of the present invention is to provide a passive receiving circuit which can be used simultaneously with an active sonar device without increasing the size of the BPF.

[0009]

According to the present invention, a bandpass filter for removing unnecessary frequencies contained in an input signal, an analog / digital converter for converting an output signal of the bandpass filter into a digital signal, In a passive receiving circuit having a digital bandpass filter for removing unnecessary frequencies included in the digital signal, a time-varying gain amplifier capable of reducing a gain according to a control signal is provided in a preceding stage of the bandpass filter. A characteristic passive receiver circuit is obtained.

[0010]

The present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. Here, the same components as those of the conventional one are given the same numbers. The passive receiving circuit of the present embodiment has a time-varying gain (TVG) amplifier 11 in a stage preceding the conventional passive receiving circuit.

The TVG amplifier 11 amplifies the input passive reception signal with a predetermined gain. Normally, the gain of the TVG amplifier 11 is set high in order to amplify a low level passive signal. In this state, a signal in which an active signal is mixed with a passive signal (see FIG. 6 (a))
However, when it is input to the TVG amplifier 11, the passive signal is masked and lost as in the conventional case. Therefore, when an active signal is transmitted (when used at the same time as the active sonar device), the gain of the TVG amplifier 11 is lowered so that the signal in which the passive signal and the active signal are mixed is not saturated in the BPF 51. At this time, TV
The signal output from the G amplifier 11 is as shown in FIG.

The signal output from the TVG amplifier 11 is
The digital signal is converted by the A / D converter 52. Digital BPF43 is a digital signal processor (DS
P), which is easy to miniaturize. This BP
F43 removes unnecessary frequencies (including active signals) included in the digital signal. In this way, the passive receiving circuit of this embodiment can detect the passive signal shown in FIG.

If a BPF having a steep cutoff characteristic similar to that of the digital BPF 43 is to be formed by an LC circuit, it will become a very large circuit.

Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the passive receiver circuit of this embodiment, the time-varying gain (TVG) correction unit 31 is provided after the digital DPF 43.
have. In the first embodiment, the gain of the TVG amplifier 11 is lowered when the passive receiving circuit is used simultaneously with the active sonar device. Therefore, the level of the signal output from the digital BPF 43 of the first embodiment is smaller than that in the case of the single operation. So TVG
The correction unit 31 amplifies the output signal of the digital DPF 43 to a level at which the gain of the TVG amplifier 11 is normally obtained. When the gain of the TVG amplifier 11 is normally high, the gain of the TVG correction unit 31 is lowered. That is, the TVG correction unit 31 includes the TVG amplifier 1
A gain characteristic having a characteristic opposite to the gain characteristic of 1 is provided.

[0016]

According to the present invention, a TVG amplifier with adjustable gain is provided in the passive receiving circuit so that the level of the passive receiving signal input to the band pass filter can be lowered, whereby the active sonar is performed. The passive signal can be detected even when used simultaneously with the device.

Since the TVG correction unit is provided so that the output signal can be amplified as needed, the level of the detected passive signal is constant regardless of whether or not the active sonar device is used at the same time. Can be kept at

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

2A and 2B are diagrams for explaining the passive receiving circuit of FIG. 1, wherein FIG. 2A is a waveform diagram of an output signal of a bandpass filter, and FIG. 2B is a waveform diagram of an output signal of a digital bandpass filter. .

FIG. 3 is a block diagram of a second embodiment of the present invention.

FIG. 4 is a block diagram of a conventional passive receiver circuit.

5A and 5B are diagrams for explaining a relationship between reception frequency bands of a passive reception circuit and an active reception circuit, FIG. 5A is a frequency characteristic diagram of a bandpass filter, and FIG. 5B is a frequency characteristic of a digital bandpass filter. It is a figure.

6A and 6B are diagrams for explaining the passive receiving circuit of FIG. 4, in which FIG. 6A is a waveform diagram of an input signal to the bandpass filter, and FIG. 6B is a waveform diagram of an output signal of the bandpass filter. .

[Explanation of symbols]

 11 Time Varying Gain (TVG) Amplifier 31 Time Varying Gain (TVG) Corrector 41 Bandpass Filter (BPF) 42 Analog / Digital (A / D) Converter 43 Digital Bandpass Filter (BPF)

Claims (2)

[Claims] 1. A bandpass filter for removing an unnecessary frequency contained in an input signal, an analog / digital converter for converting an output signal of the bandpass filter into a digital signal, and an unnecessary frequency contained in the digital signal. A passive receiving circuit having a digital bandpass filter for controlling the gain, wherein a time-varying gain amplifier capable of gain control is provided in the preceding stage of the bandpass filter. 2. The passive receiving circuit according to claim 1, further comprising a gain correction unit that corrects a level of a signal input after the digital band pass filter.