JPS6360347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION For example, a received signal in a radar device includes, in addition to a target signal, unnecessary signals such as interference waves, rain, and reflections from the sea surface. Among these, non-periodic interference waves can be solved by taking continuous correlation, while periodic (on the display) signals such as rain and sea surface reflections can be removed by applying differentiation (so-called FTC). . However, even in the above-mentioned rain and sea surface reflection signals, it is difficult to remove signals with fast rises or signals with long pulse widths, and by performing differentiation, the target signal is represented on the display only by the rise part. I couldn't get accurate information.

The present invention provides a device which eliminates the above-mentioned drawbacks and will be explained in detail below on the basis of an embodiment of the drawing.

FIG. 1 is a circuit diagram according to the present invention, in which numeral 1 is an antenna that transmits detection radio wave pulses at a constant repetition period, and numeral 2 is a transmission/reception switching circuit that switches the signal path during wave transmission and wave reception. 3 shows a DC component removal circuit that removes DC components from the received signal and extracts only AC components. 4 and 5 are delay circuits that delay the signal by Δt, and the output terminal of the delay circuit 4 is connected to the input terminal of the delay circuit 5. Reference numerals 6 and 7 are analog correlation circuits such as, for example, AND gates composed of two diodes and a resistor, each having input terminals A, B, C, and D. Reference numeral 8 denotes an adder circuit that performs an OR gate on the outputs of the analog correlation circuits 6 and 7.

Figure 2 shows the waveform diagram of each circuit.
b' is a partially enlarged version of b.

In the above circuit configuration, the operation thereof will be explained next. Signal a (Fig. 2) containing various information received from the antenna passes through the transmission/reception switching circuit 2, and then is converted to AC signal b in the DC component removal circuit. Only the components are extracted. Signals R ₁ and R ₂ are representative signals from actual rain and sea surface reflection, and S ₁ is a reflection signal from a target object. Generally, unnecessary reflected waves are
As shown in waveforms R ₁ and R ₂ , triangular waves appear,
The target reflected wave appears as a rectangular waveform, as shown in waveform _S1 .

Now, the signals R ₁ , S ₁ and R ₂ included in the output signal b' (that is, signal b) of the DC component removal circuit 3 are sent to the input terminal A of the analog correlation circuit 6 and are also sent to the delay circuit 4. and is delayed by Δt time. This output signal C is sent to the input terminal RO of the analog correlation circuit 6, and a signal e is obtained as an output. As is clear from the waveform diagram e, the analog correlation circuit 6 compares the DC component removed output b' and the delayed output c and selects the one with the lower level of both signals.
On the other hand, the signal C is sent to the input terminal C of the analog correlation circuit 7, and is also sent to the delay circuit 5.
The signal d is further delayed by Δt time and sent to the output side. The signal d is sent to the input terminal 2 of the analog correlation circuit 7, and the signal f is obtained as an output. As is clear from the waveform diagram f, the analog correlation circuit 7 compares the delayed outputs c and b and selects the one with the lower level of both signals. As a result, the outputs e and f of the analog correlation circuits 6 and 7 are limited in pulse height and width based on the delay time Δt set in the delay circuits 4 and 5. Furthermore, the above signals e and f obtain a result signal g which is fed to the adder circuit 8 of the OR gate. As is clear from the waveform g, the adder circuit 8 selects the higher level signal from the two signals e and f. This is Figure 2 e, f, g
As is clear from the above, the rain and sea surface reflection signals R ₁ ,
R ₂ is converted into signals R' ₁ and R' ₂ with each pulse height being limited.

On the other hand, the target signal S ₁ is the output signal S′ ₁ of the adder circuit 8
It is delayed by Δt time as shown in FIG.

As described above, according to the present invention, it is possible to suppress the level of unnecessary signals such as rain and sea surface reflection without changing the pulse width, and therefore, as a result of brightness modulation, it is possible to suppress the level of unnecessary signals such as rain and sea surface reflection. Identification becomes extremely easy.

Further, even if the delay amount Δt is varied in order to set the optimum discrimination state on the cathode ray tube, the pulse width and pulse height of the target signal do not change. That is, the target signal can always be displayed on the cathode ray tube as the received signal without waveform modification.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a waveform diagram of each circuit. 3 is a DC removal circuit, 4 and 5 are delay circuits, 6 and 7 are analog correlation circuits, 8 is an addition circuit, R ₁ and R ₂ are rain and sea surface reflection signals, and S ₁ is a target signal.

Claims (1)

[Scope of Claims] 1. A transmitting/receiving device that repeatedly transmits detection pulses and receives reflected waves from detected targets, and which removes the DC component from the received signal output from the transmitting/receiving device and extracts only the AC component. an AC component extraction circuit; a first delay circuit that delays the output signal of the AC component extraction circuit; a second delay circuit that further delays the delayed output of the first delay circuit; a first analog correlation circuit that compares the delayed output and the AC component extraction output and selects a signal with a lower level among both signals; A second analog correlation circuit selects a signal with a lower level among the signals, and compares each selected output of the first and second analog correlation circuits to select a signal with a higher level among both output signals. an amplitude suppression circuit that suppresses the amplitude of an unnecessary signal whose rising and falling parts are relatively slow compared to the target signal; and an output signal of the amplitude suppression circuit. A radar device comprising a display device.