JPS62204177A - Pulse compressing radar transmitter and receiver - Google Patents

Abstract

PURPOSE:To easily realize various pulse compression and modulation characteristics by generating a transmit signal and compressing pulses digitally and principally, in a read-only memory with clock signals generated by a common generation source. CONSTITUTION:The digitized signal which is generated by the read-only memory 5 under sequence control 4 is D/A-converted 6, passed through a filter 7 and a mixer 8, and amplified 9 to a specific electric power level, and the signal is led to an antenna through a duplexer 10 and radiated in the air. Then, a radio wave reflected by a target is passed through the antenna and duplexer 10 and amplified 11, and the amplified signal is A/D-converted 13 through a mixer 12 and stored 14. The received signal which is stored 14 is read out with a readout address specifying signal from a readout address specifying circuit while a signal corresponding to the transmit pulse width is shifted by each time corresponding to distance resolution. A correlation signal, on the other hand, is stored in a correlator 15, which multiplies the input received signal by the correlation signal to perform pulse compression.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pulse compressor transmitter/receiver, and more particularly to digitization of a transmission signal generation means and a reception signal pulse compression means.

(Prior art) In order to increase the detection distance of a normal pulse radar, it is necessary to increase the average transmission power, but since there is a technical limit to increasing the peak power, other means of transmitting A possible method is to widen the pulse width.

However, there is a problem in that increasing the transmission pulse width reduces distance resolution, and as a result, increasing the detection distance and improving distance resolution are conflicting performance requirements.

A pulse compression radar system using pulse compression technology is considered as a solution to this problem. This pulse compression technology widens the transmission pulse width in order to increase the average transmission power, and at the same time applies frequency modulation at a predetermined time-to-frequency change rate within the pulse width. The signal is passed through a delay filter that has a frequency delay time characteristic that is exactly opposite to the time-to-frequency change rate in the transmitted pulse, so that the frequency components that were sequentially dispersed in the pulse are concentrated at one point, resulting in a sharp signal. It takes advantage of the fact that it becomes an impulse. This means that it becomes easier to separate and identify two nearby targets.

That is, pulse compression technology is a technology that can increase the detection distance and obtain high resolution by widening the transmission pulse width.

FIG. 2 is a block diagram showing the general configuration of a pulse radar. This configuration includes a transmitting device 61, a duplexer 62, an antenna 63, and a receiving device 64.
The output is emitted from an antenna 63 to a target object through a duplexer 62, and the radio waves reflected from the target object are received and inputted to a receiving device 64 through the duplexer 62 again. In the pulse compression radar device, the transmitting device 61 is provided with a means for frequency modulating within the transmission pulse width, and the receiving device 64 has a frequency versus delay time characteristic that is exactly opposite to the frequency modulation within the transmitted pulse. Details of zero-order frequency modulation in which a delay filter having a delay filter is provided will be explained with reference to FIGS. 3 and 4.

One of them is a PLL (Phase Locked Loop
: Phase-locked loop) is a transmitting device using a frequency modulator.

The output of the frequency generator 70 is applied to the synchronization signal generator 71, and the stabilized frequency signal is sent to the PLL modulation circuit 7.
3 and simultaneously add a slope signal necessary for linear frequency modulation through the sweep voltage generation circuit 72, and the linear frequency modulated signal output from the PLL modulation circuit 73 is controlled by the output of the synchronization signal generator 71. The rising and falling parts of the output signal are shaped by the circuit 74 and the frequency converter 7
5 is input. The signal inputted here is converted to a transmission frequency, becomes a transmission output signal with the necessary power by a power amplifier 76, and is radiated from an antenna 78 via a duplexer 77.

A reflected signal (received signal) from the target is received by an antenna 78, inputted to a receiving device 79 via a duplexer 77, pulse-compressed, and outputted as a received signal 313.

The other one is the SAW (Acousti
This is a device using a delay dispersion element that utilizes 5 surface acoustic waves (surface acoustic waves).

The output of the frequency generator 80 is applied to the synchronization signal generator 81, and the stabilized frequency signal is sent to the pulse modulation circuit 8.
2 to form a short pulse wave with a rectangular envelope, and input it to the SAW delay dispersion element 83.

A frequency modulated signal is output from the SAW delay dispersion probe 83 and input to a switch circuit 84 controlled by the output of the synchronizing signal generator 81, where its rising and falling parts are shaped and sent to a frequency converter 85. The signal input to the zero frequency converter 85 is converted to a transmission frequency, amplified by a power amplifier 86 to a transmission output signal with the required power, and transmitted to the air via a duplexer 87! It is radiated from 88.

The reflected signal from the target is received by the antenna 88, and is inputted to eight receiving devices via the duplexer 87 to receive the received signal 4.
13 and is output.

(Problems to be Solved by the Invention) As described above, as the frequency modulation means within the transmission pulse of the conventional pulse compression radar device, the PLL modulation circuit or the SAW
A delay dispersion element is used. For example, the frequency temperature coefficient of crystal often used as a SAW delay dispersion element is -24X10-'/'C, and the frequency temperature coefficient of bismuth germanate is -122X10-6/'C. It is.

When such a SAW delay dispersion element is used, its output frequency naturally changes as the environmental temperature changes.

This causes a change in the rate of change in frequency with respect to time within the transmission pulse width (chirp rate), resulting in a mismatch with the characteristics of the correlation filter provided in the receiving device.

As a result, there is a problem in that even if pulse compression processing is performed on the received signal, sufficient pulse compression is not achieved and the distance resolution becomes sharp. The requirements for the frequency temperature coefficient become stricter as the signal bandwidth (maximum small frequency difference within the transmission pulse width) and delay dispersion time become larger4.For example, assume that the chirp rate fluctuation tolerance is ±0.1%, When bismuth germanate is used as the SAW delay dispersion element, the allowable temperature change range is about 8.2°C from the above-mentioned temperature coefficient (-122 x 10-6/''C), and even in the case of quartz, it is about 42°C.

Therefore, in the case of bismuth germanate, even if the transmitting device is installed on the ground, it is necessary to add a complicated temperature compensation circuit or put it in a constant temperature oven, and even in the case of crystal, it is necessary to install it on an aircraft or satellite. However, it becomes unusable without a temperature compensation circuit or thermostat. However, in the case of on-board equipment, there are significant restrictions on weight and occupied space, which poses a problem.The purpose of the present invention is to generate and receive frequency-modulated pulse signals in consideration of the problems in the prior art described above. This method attempts to solve problems caused by environmental temperature changes by digitally performing pulse compression processing of the generated signals using an interlocking clock signal.

(Means for Solving the Problems) The present invention has the following means configuration to achieve the above object. That is, the pulse compression radar transmitting/receiving device of the present invention serves as a transmission signal generating means for the pulse compression radar, and receives a sequence control signal and receives an analog signal which is frequency-modulated according to a predetermined rate of frequency change within a predetermined time width. A transmission read-only memory that outputs a digital signal to be converted into a signal; A sequence that receives a radar transmission pulse repetition frequency signal and outputs a sequence control signal for specifying a read address for each pulse repetition and sends it to the read-only memory. a controller; a D/A converter that converts the digital signal read from the read-only memory into an analog signal; and an A/D converter that converts the received signal into a digital signal as pulse compression means for the received signal. a converter; a received signal memory that stores the received signal from the A/D converter; moves a signal equivalent to the transmission pulse width from the received signal stored in the received signal memory by a time width corresponding to a set distance resolution; a read addressing circuit that outputs a read addressing signal for readout to the received signal memory; a correlated signal read only memory that stores a correlation signal that is cross-correlated with the transmitted signal in time versus frequency characteristics; a controller that sends a correlation signal read control signal to the correlation signal read-only memory to output the correlation signal from the correlation signal read-only memory in correspondence with a read reception signal corresponding to a transmission pulse width from the received signal memory; a correlator that receives the received signal from the signal memory and the correlation signal from the correlation signal read-only memory, compresses the pulse by multiplying it for each division corresponding to the transmission pulse width, adds the results, and outputs the result; The pulse compression radar transmitting/receiving apparatus is characterized in that it has a synchronizing signal generating circuit that supplies clock pulses having a common source to the transmitting signal generating means and the pulse compressing means.

(for production) The effects of the present invention will be described below.

As described in the above means configuration, the pulse compression radar transmitting/receiving device of the present invention generates a transmission signal by frequency modulation (Frequency Modulation: F) according to a predetermined frequency change rate within a predetermined time width.
A digitized FM signal is read out by controlling a transmission read-only memory storing a digital signal to be converted into an analog signal subjected to M) by a sequence control signal from a sequence controller.

The sequence control signal designates a read address for reading the digitized FM signal from the transmit read-only memory for each repetition of the radar transmit pulse. The signal read from the transmission read-only memory is converted into an analog signal by a D/A converter, then frequency-converted by a frequency converter to a predetermined transmission frequency, similar to conventional radar equipment, and then converted to a predetermined transmission frequency by a power amplifier. It is amplified to a power level, guided to an antenna via a duplexer, and radiated into space. The radio waves reflected from the target object go through an antenna and a duplexer, and are amplified by an amplifier, similar to conventional radar equipment.
Next, a frequency converter converts the signal to a frequency that is easier to perform subsequent processing. The pulse compression of the pulse compression radar of the present invention is as follows:
The frequency-converted received signal is converted into a digital signal by an A/D converter and stored in a received signal memory. The stored reception signal is read out by moving a signal corresponding to the transmission pulse width by a time interval corresponding to the distance resolution using a read address designation signal from a read address designation circuit. The read signal is applied to a correlator. 'On the other hand, the correlation signal from the correlation signal read-only memory is applied to the correlator. The correlation signal read-only memory stores a correlation signal whose slope is exactly opposite to the signal stored in the transmission signal read-only memory in terms of time versus frequency characteristics, and the correlation signal read control signal from the controller is stored in the correlation signal read-only memory. In response, a correlation signal is output in response to the read reception signal corresponding to the transmission pulse width from the reception signal memory.

The correlator performs pulse compression by multiplying the input received signal and the correlation signal.

The transmission signal generation and pulse compression described above are performed digitally using a clock signal that has a common source.

Therefore, compared to PLL modulation circuits and SAW delay dispersion elements of conventional devices, they are less affected by environmental temperature changes. Since this is common to both the pulse compression means and the pulse compression means, the effect that would occur if only one of them were changed does not appear, and the resolution is not affected.

Further, in the device of the present invention, various pulse compression modulation characteristics can be easily realized by simply changing the storage contents of the transmission read-only memory and the correlation signal read-only memory.

(Embodiments) Next, the present invention will be described in detail with reference to drawings showing embodiments. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

The present invention digitizes a frequency-modulated transmission signal in advance and stores it in a ROM (read-only memory), reads it every time it is transmitted, performs D/A conversion, and converts the received signal into an A/D signal. The clock pulse signal is converted and compressed by passing it through a correlator that has a cross-correlation with the transmitted signal.If the clock pulse signal is stabilized, stable transmitted signals and compressed pulses that hardly change even if the environmental conditions change can be obtained. It will be done. The modulation characteristic (the relationship between time and frequency within one transmitted pulse) is typically represented by a linear FM modulated wave, but by replacing the memory, not only this but also a non-linear FM modulated wave can be easily obtained.

Here, the configuration and operation of an embodiment of the present invention will be explained. Stabilized frequency signal 10 output from stabilized oscillator 1
8 is input to the synchronization signal generator 2. The synchronization signal generator 2 outputs a control signal to the repetition frequency generator 3, which outputs a transmission repetition frequency signal 102 that determines the transmission interval and transmission time.

Further, the synchronization signal generator 2 supplies a stabilizing signal to the sequence controller 4 that specifies the read number of the transmission read-only memory 5, and the transmission read-only memory 5 and the D/A converter 6 each receive a read tarock signal. The transmission read-only memory 5 which outputs the clock pulse signal 105 and the clock pulse signal 106 receives the read address designation signal 103 from the sequence controller 4, and when the read address is designated according to the transmission repetition frequency,
A pre-stored digital signal is output according to the read clock signal 105, converted into an analog signal by the D/A converter 6, and frequency-modulated as a transmission signal 10.
7 and is input to the filter 7. The filter 7 is composed of a low-pass or bandpass filter, and removes unnecessary components from the analog signal and inputs it to the mixer 8 . In the mixer 8, the stabilized frequency signal f1 from the stabilized oscillator 1 is converted into a transmission frequency. Power amplifier 9 amplifies the transmission signal to a required level and outputs it from transmitter 100 as a transmission output signal.

The transmitted output signal is radiated from the antenna to the target via the duplexer 10. The reflected signal from the target object is received by an antenna and sent to the receiving device 101 via the duplexer 10. Amplifier 11 amplifies the received signal and outputs it to mixer 12 .

The mixer 12 converts the frequency of the stabilized frequency signal f2 inputted from the stabilized oscillator 1 to a low frequency that can be A/D converted, and converts it into an A/D converter 13. The A/D converter 13 performs A/D conversion according to the clock pulse signal output from the synchronization signal generator 2. The A/D converted received signal is stored in the received signal memory 14.

The controller 16 sends a signal to the received signal memory 14 and the correlator 15 based on the controller clock signal 110 from the synchronization signal generator 2. Controller 16 as well as received signal memory 14
The read address designation signal 111 sent to reads the received data stored in the memory. Here, the controller 16 has the function of a read address designation circuit for the received signal and the function of a controller for sending out a correlation signal read control signal. The correlation signal read-only memory is included in the correlator 15. The received data is transferred from the repetition frequency generator 3 to the controller 16.
It is reset every transmission pulse repetition period by a signal sent to .

Now, FIG. 5 shows a transmission pulse with a constant amplitude in which the transmission pulse width is τ, the minimum frequency is fl, and the maximum frequency is f2, and the linear frequency modulation is steep.

The transmission read-only memory 5 stores digitally encoded signals such that when passed through the D/A converter 6, an analog signal as shown in FIG. 5 is obtained. When such a signal is passed through a circuit having the frequency vs. delay time characteristic shown in FIG. 6, that is, a circuit in which the relationship between time and frequency has an inverse slope, the pulse width becomes 1/Δf (however, Δf
= f, -f1 (this is called the signal bandwidth) and the amplitude is J
It is widely known that a pulse of "Tll" can be obtained.

In this embodiment, the correlation signal is read out from the correlation signal read-only memory in the correlator 15 using the correlation signal readout control signal from the controller 16, and multiplied by the received signal, so that the frequency delay time characteristic as shown in FIG. 6 is obtained. The digitized signal is stored in the correlation signal read-only memory in such a manner that it is equivalent to passing through a circuit having the correlation signal.

To multiply the received signal and the correlation signal, the signal corresponding to the transmission pulse width is read out from the received signal memory as one section, moved by a time width ΔT according to the distance resolution determined by the signal bandwidth, and the correlation signal is calculated for each section. Multiplication is performed and pulse compression is performed.

The compressed signals are added at the same timing,
Output. The timing at which compression is performed by moving by a time width ΔT in this manner is determined by the read address designation signal 111 and control signal 112 from the controller 16.

(Effects of the Invention) As explained above, the transmission signal generation and pulse compression of the pulse compression radar transmitting/receiving device of the present invention are digitally performed using a clock signal having a common source, centered on a read-only memory. PL of conventional equipment
Compared to L modulation circuits and SAW delay dispersion elements, it is less affected by temperature changes, and even if the clock frequency changes slightly due to temperature changes, it is common to the transmission signal generation means and pulse compression means. , there is an advantage that the resolution does not deteriorate because there is no effect unlike in the conventional apparatus when only one means or both means are changed independently.

Furthermore, the device of the present invention has the advantage that various pulse compression modulation characteristics can be easily realized by simply changing the storage contents of the transmission read-only memory and the correlation signal read-only memory.

[Brief explanation of drawings]

FIG. 1 is a plot diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a general pulse radar device,
FIG. 3 is a block diagram showing an example of the configuration of a conventional pulse compression radar device, FIG. 4 is a block diagram showing another example of the configuration of a conventional pulse compression radar device, and FIG. 5 is a block diagram showing an example of the configuration of a conventional pulse compression radar device. FIG. 6 is a frequency vs. delay time characteristic diagram of the pulse compression means, and FIG. 7 is a pulse compressed waveform diagram. 1... Stabilizing oscillator, 2... Periodic signal generator, 3... Repetition frequency generator, 4...
... Sequence controller, 5 ... Transmission read-only memory, 6 ... D/A converter, 7 ...
...Filter, 8...Mixer, 9...
...Power amplifier, 10...Duplexer,
11...Amplifier, 12...Mixer, 13...A/D converter, 14...
Received signal memory, 15... Correlator, 16.
...Controller. Agent: Yoshihiro Yahata, Patent Attorney, Pulse Shi-gu-burning-ffs--f# Branch-no-Kimi-min Figure 2, Conventional 0 Nov Rus, 10,000 J Inns, I, Only 4 Sen, Case No. 3
Figure 4's L squad prestige rate of conventional NOV Luss 10,000 J storage device
4 Diagram A (X, Fu Hassis, who is in power with the power of the eastern state, Liang, and power, Figure 5)
Figure C Pulse pressure N11

Claims (1)

[Claims] As a transmission signal generation means for a pulse compression radar, a transmission device receives a sequence control signal and outputs a digital signal to be converted into an analog signal frequency-modulated according to a predetermined frequency change rate within a predetermined time width. a read-only memory; a sequence controller that receives a transmission pulse repetition frequency signal from the radar and outputs a sequence control signal for specifying a read address for each pulse repetition and sends it to the read-only memory; a D/A converter that converts a digital signal into an analog signal; and an A/D converter that converts the received signal into a digital signal as a pulse compression means for the received signal.
a converter; a received signal memory that stores the received signal from the A/D converter; moves a signal equivalent to the transmission pulse width from the received signal stored in the received signal memory by a time width according to the set distance resolution; a read addressing circuit that outputs a read addressing signal for readout to the received signal memory; a correlation signal read only memory that stores a correlation signal that is cross-correlated with the transmitted signal in time versus frequency characteristics; a controller that sends a correlation signal read control signal to the correlation signal read-only memory to output the correlation signal from the correlation signal read-only memory in correspondence with a read reception signal corresponding to a transmission pulse width from the received signal memory; a correlator that receives the received signal from the signal memory and the correlation signal from the correlation signal read-only memory, multiplies it for each transmission pulse width equivalent division, and performs pulse compression by adding the results; A pulse compression radar transmitting/receiving device comprising a synchronizing signal generating circuit that supplies clock pulses having a common source to the transmitting signal generating means and the pulse compressing means.