JPH04318483A - Radar receiver - Google Patents

Abstract

PURPOSE:To enable an optimum sea level reflection suppression state to be retained constantly by multiplying an amplitude control signal by a proportion component of a gain which is set by a gain-setting circuit and then adding it to a radar video signal amplitude of a voltage-controlled amplifier as an input bias. CONSTITUTION:A voltage-controlled amplifier 1 amplifies a radar video signal which is input from an antenna portion 100 according to the control voltage and an STC (sea-level reflection suppression) voltage generation circuit 2 generates an STC voltage which changes according to a time lapse from a transmission trigger generation timing. A gain-setting circuit 3 adds a bias to a control voltage which is given to the amplifier 1 through an adder 4 and controls an entire amplification rate. With this configuration, an STC voltage signal where a proportional component of a gain which is set by the circuit 3 is multiplied is generated, a bias of the set gain is added to the signal by the adder 4 and then is given to the amplifier 1. In this manner, as the set gain is higher (lower), the amplitude becomes higher (lower), thus enabling an optimum sea-level reflection suppression to be performed constantly.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device that detects a target object by transmitting pulsed radio waves and receiving reflected waves from the target object, and particularly relates to a radar receiving device having a sea surface reflection suppressing function.

0002

[Prior Art] A radar device (pulse radar) detects a target by changing the pointing direction of the antenna, emitting pulsed radio waves, and receiving reflected waves from the target. The reflected signal appears on the CRT, and the area near the center shines, causing a phenomenon in which targets near the ship become invisible. This is due to sea surface reflection, which is stronger the closer you are, and gradually weakens as you get farther away. It also varies depending on sea conditions, and when waves are high, sea surface reflections can affect up to 6 to 7 nautical miles from the center.

Conventionally, an STC circuit (sea surface reflection suppression circuit) has been provided in a receiving section as a device for suppressing the influence of sea surface reflection. FIG. 6 shows a block diagram of a conventional radar device.

In FIG. 6, the radar device includes an antenna section 100.
, receiving section 101, image processing section 102, and display device 10
Consists of 3. In the receiving section 101, the voltage control amplifier 1 amplifies the radar video signal from the antenna section 100 with an amplification factor corresponding to the applied control voltage as shown in FIG. The STC voltage generation circuit 2 generates an STC voltage signal that changes with the passage of time after the transmission trigger is generated. This STC voltage generation circuit 2 is comprised of a waveform converting circuit such as an integrating circuit or a differentiating circuit, and as shown in FIG. 7, generates an STC voltage signal as shown in FIG. 8 upon input of a transmission trigger. In the figure, t is the elapsed time from the transmission trigger generation timing. In Figure 6, gain setting circuit 3
is used to set the overall amplification factor in the receiving section 101, and the adder 4 adds a bias voltage to the STC voltage signal to provide a control voltage to the voltage control amplifier 1. Therefore, depending on the output voltage of the gain setting circuit 3, the amplification degree of the voltage control amplifier 1 changes as shown in FIG.

As described above, an STC voltage waveform as shown in FIG. 11 is provided to the voltage control amplifier 1 every time a transmission trigger occurs.

[0006]

[Problems to be Solved by the Invention] As described above, in conventional radar equipment, the S applied to the voltage control amplifier of the receiving section is
Since the circuit that generates the TC voltage signal is composed of an integrating circuit or a differentiating circuit, the STC voltage waveform is determined by circuit constants.

However, it has been empirically determined that the optimum amplification change characteristic (hereinafter referred to as STC characteristic) of the amplifier, which should change over time from the transmission trigger generation timing, differs depending on the amplification degree of the entire receiving device. This is known and can be considered theoretically. That is, the center (
When the influence of sea surface reflection appears in a relatively short range from the antenna position, the amplification of the entire receiving device is increased to prevent the target from disappearing from medium to long distances. Sea surface reflections at distance must be suppressed. On the other hand, if the influence of sea surface reflection appears at a relatively far distance from the center, the amplification of the entire receiving device must be lowered, but it is necessary to ensure that targets at short distances do not disappear.

[0008] In the conventional radar receiving device, suppression of sea surface reflection is optimized by shifting the entire STC voltage curve as shown in FIG. 10 using the gain setting circuit 3 shown in FIG. . Therefore, if the overall amplification degree is increased in order to prevent the disappearance of targets from medium to long distances, the amplification degree at short distances becomes too high, and the influence of sea surface reflection appears. Furthermore, if the overall amplification degree is lowered in order to prevent the influence of sea surface reflections that appear at relatively far distances, the amplification degree at short distances will be reduced too much, resulting in the problem of target objects disappearing at short distances.

An object of the present invention is to optimize the amplification control signal (thereby optimizing the STC characteristics) in accordance with the gain setting that sets the amplification degree of the entire receiving device, so as to optimize the amplification control signal according to the conditions and situations at the time of observation. It is an object of the present invention to provide a radar receiving device that enables observation in a state where reflections from the sea surface are appropriately suppressed.

0010

[Means for Solving the Problems] The radar receiving device of the present invention includes a voltage control amplifier that amplifies a radar video signal with an amplification factor that corresponds to an amplification control signal, and a voltage control amplifier that amplifies a radar video signal with an amplification factor that corresponds to an amplification factor control signal, and a voltage control amplifier that amplifies a radar video signal with an amplification factor that corresponds to an amplification factor control signal, and a voltage control amplifier that amplifies a radar video signal with an amplification factor that corresponds to an amplification factor control signal. an amplification control signal generation circuit that generates an amplification control signal to control the voltage control amplifier; a gain setting circuit that adds a bias to the signal to be applied to the voltage control amplifier to set the amplification of the entire receiving device; and amplification correction means for multiplying the amplification control signal.

[0011]

[Operation] In the radar receiver of the present invention, the amplification control signal generation circuit generates an amplification control signal that changes with time from the transmission trigger generation timing, and the gain setting circuit generates a signal that is applied to the voltage control amplifier. The amplification degree of the entire receiving apparatus is set by adding a bias to the gain, and the amplification degree modifying means multiplies the amplification degree control signal by a proportional component of the set gain. Since the voltage control amplifier amplifies the radar video signal according to the given amplification control signal, the higher the gain set by the gain setting circuit, the more the amplification control signal changes (slope) with the passage of time from the transmission trigger generation timing. becomes steeper, and conversely, the lower the set gain, the slower the change (slope) of the amplification control signal given to the voltage control amplifier. Therefore, the amplification change characteristic (STC characteristic) can be made more suitable for the set gain, and the influence of sea surface reflection can be removed from short distances to long distances, and observation can be performed without target disappearance. .

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a block diagram of a radar apparatus according to an embodiment of the present invention is shown in FIG. In FIG. 1, the radar device includes an antenna section 100, a receiving section 101, an image processing section 102, and a display device 103. In the receiving section 101, the voltage control amplifier 1 amplifies the intermediate frequency signal of the radar image sent from the antenna section 100 with an amplification factor corresponding to the applied control voltage. The STC voltage generation circuit 2 has an STC voltage that changes with the passage of time from the transmission trigger generation timing.
Generates TC voltage. The gain setting circuit 3 adds a bias to the control voltage to be applied to the voltage control amplifier 1 via the adder 4 to control the amplification factor of the entire receiving section. The STC characteristic selection switch 6 selects the ST to be generated by the STC voltage generation circuit 2.
Select C voltage signal. The detection circuit 5 detects the intermediate frequency signal of the radar video signal amplified with an appropriate amplification factor and outputs it to the image processing section 102. In the image processing unit 102, A
-D converter 7 converts the radar video signal into digital data. The image memory 8 sequentially stores digital data of radar images. The image processing circuit 9 performs predetermined image processing based on the relationship between the data already written in the image memory 8 and the new image data, and writes the results to the image memory 8. The display device 103 is the image memory 8
is read out at a predetermined timing, a video signal is created, and the radar video is displayed on a CRT.

Next, the STC voltage generation circuit 2 shown in FIG.
FIG. 2 shows a specific configuration of the system as a block diagram. In FIG. 2, a clock generation circuit 20 generates a clock signal of a constant frequency. The counter 22 counts the clock signal and switches the frequency division ratio of the frequency dividing circuit 21 every time the clock signal reaches a predetermined value. The frequency dividing circuit 21 divides the clock signal at a frequency division ratio determined by the state of the counter 22. The address counter 23 counts the output signal of the frequency dividing circuit 21 and provides the count value as a lower address (A0 to A5) of the amplification degree data memory 24. The address selector 25 provides the upper address (A6 to A15) of the amplification data memory 24 in accordance with the selection of the STC characteristic selection switch 6. The amplification data memory 24 outputs the contents of the designated address. That is, in this example, multiple STCs
Characteristic data is written in the amplification degree data memory 24 in advance, and the target ST can be selected by operating the STC characteristic selection switch 6.
C characteristics can be selected. D-A converter 26
converts the output data of the amplification data memory 24 into an analog signal, and the low-pass filter 27 removes sampling noise. The multiplier 28 multiplies the signal by a voltage proportional to the gain set by the gain setting circuit and outputs the result as an STC voltage signal.

An example of the data structure of the amplification data memory 24 shown in FIG. 2 is shown in FIG. The upper addresses A6 to A15 of this amplification degree data memory are the data types (STC characteristics)
is selected, and the lower addresses A0 to A5 determine the read position of each data (position determined as time elapses from the transmission trigger generation timing). That is, data 000,
One of the STC characteristic data of data 001, data 002, . . . is selected by the address selector 25 shown in FIG. 2, and the address counter 23 sequentially reads out the STC characteristic data from the start address.

FIG. 4 shows waveforms of each part shown in FIG. 2. In FIG. 2, the frequency divider circuit 21 gradually increases the frequency division ratio by the action of the counter 22, so the address counter 23 counts up minutely immediately after the transmission trigger occurs, and gradually increases the frequency division ratio as time passes. It will count up slowly. This increases the resolution of the STC voltage curve at short distances and saves the memory capacity of the amplification data memory 24. Further, the clock generation circuit 20, frequency division circuit 21, counter 22, and address counter 23 are reset by the transmission trigger,
Each time a transmission trigger occurs, the address counter 23 sequentially selects addresses in the amplification degree data memory 24 starting from the same start address.

In this way, in synchronization with the transmission trigger,
An STC voltage signal multiplied by a proportional component of the set gain is generated, a bias corresponding to the set gain is added to the STC voltage signal by an adder 4 (see FIG. 1), and the added bias is applied to the voltage control amplifier 1.

FIG. 5 shows an example of the amplification change characteristics of the receiving section shown in FIGS. 1 and 2. In this way, gain setting circuit 3
The higher the gain setting, the higher the overall amplification.
Moreover, the slope of the increase in the amplification degree as time passes from the trigger generation timing becomes steep. Conversely, the lower the set gain, the lower the overall amplification degree, and the slower the slope of the increase in the amplification degree.

[0018]

According to the present invention, when the set gain of the entire receiving device is high, the slope of the amplification factor change of the voltage controlled amplifier becomes steep as time elapses from the transmission trigger generation timing. Sea surface reflections at long distances are effectively suppressed, preventing target objects from disappearing from medium to long distances. In addition, when the overall gain setting of the receiving device is low, the slope of the change in the amplification factor of the voltage control amplifier becomes gentler, so it is possible to eliminate the influence of sea surface reflections over relatively long distances and prevent target objects from disappearing at short distances. can. Therefore, depending on the observation state and conditions, optimal sea surface reflection suppression can be performed at all times to ensure reliable observation.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a radar device according to an embodiment.

FIG. 2 is a block diagram of an STC voltage generation circuit in the radar device of the embodiment.

FIG. 3 is a configuration diagram of an amplification degree data memory.

FIG. 4 is a waveform diagram of each part in FIG. 2;

FIG. 5 is a diagram showing the difference in amplification change characteristics depending on the set gain.

FIG. 6 is a block diagram of a conventional radar device.

FIG. 7 is a circuit diagram of a conventional STC voltage generation circuit.

FIG. 8 is a characteristic diagram of a conventional STC voltage generation circuit.

FIG. 9 is a characteristic diagram of a voltage controlled amplifier.

FIG. 10 is a diagram showing the amplification factor change characteristic of a conventional receiving section that changes depending on the gain setting.

FIG. 11 is a waveform diagram of each part in FIG. 6;

[Explanation of symbols]

100-Antenna section 101-Receiving section 102-Image processing unit

Claims (1)

[Claims] 1. A voltage control amplifier that amplifies a radar video signal with an amplification factor according to an amplification control signal, and an amplification control signal that generates an amplification control signal that changes with time from the transmission trigger generation timing. a generating circuit; a gain setting circuit that applies a bias to the signal applied to the voltage control amplifier to set the amplification degree of the entire receiving device; and an amplification degree correction means that multiplies the amplification degree control signal by a proportional component of the set gain. A radar receiving device equipped with