JPH02201286A - Measuring apparatus of distance - Google Patents

Abstract

PURPOSE:To improve resolution by a method wherein the times of generations of long and short code series having auto-correlativity and orthogonal relations are controlled so that the front edge parts thereof be delayed sequentially and that the rear end parts be aligned before transmission, reflected waves are filtered and a plurality of series are added up. CONSTITUTION:In a transmitting section 10, codes C1 to Cn are generated from code generators 24, 26... numbering (n) and generating long and short code series by a timing control circuit 30. Then, the front edge parts of the codes are delayed sequentially while the rear edge parts thereof are aligned, and the codes are added up 32 and 34, so as to form a code C120. A PSK modulator 36 is modulated by the code C120 and a transmission wave W1 is emitted from a transmitter 22 and an antenna 16. A reflected wave W2 from an airplane Cb is received by a receiver 42 in a receiving element 12, and signals S21, S22... S2n filtered by 1st to (n)th matched filters 46, 48... are added up by an adder 52, subjected to signal processing 56 and outputted. By this method, the maximum and minimum limits of detection are expanded and the resolution of distance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a distance measuring device, and more particularly, the round-trip time and the antenna during which an emitted transmission pulse is sensed after being reflected by a target object. Primary radar obtains two-dimensional or three-dimensional position information of an aircraft, etc., from radiation characteristics, that is, directional characteristics.
ance Radar (hereinafter referred to as PSR) and secondary radar (Secondary Surveillan).
ce Radar (hereinafter referred to as SSR), etc., the signals of multiple code sequences having autocorrelation characteristics and having an orthogonal relationship of different lengths are sequentially processed from the leading edge of the signal of the code sequence of the maximum length. It forms a composite code signal in which the leading edge is delayed and the trailing edge is close, and transmits a transmission pulse modulated by the composite code signal, which is then reflected from the target and is felt. The peak transmission power of the transmission pulse ( The present invention relates to a distance measuring device that can reduce transmission power (hereinafter simply referred to as transmission power as needed), expand minimum and maximum detection ranges, and improve distance resolution.

[Background of the Invention] Conventionally, in distance measuring devices such as PSR and SSR, it has been necessary to improve the accuracy of position measurement of a target object, such as an aircraft, and to increase the measurement distance.In other words, to increase the minimum and maximum range and distance resolution. In order to improve the transmission power, a method has been adopted in which the transmission power is further increased and the transmission pulse width is formed to be narrower.

Further, in order to reduce the size of equipment such as a transmitter and to reduce the transmission power from the viewpoint of utilization efficiency of limited radio waves, means using codes having autocorrelation characteristics is adopted. This means transmits a transmitted pulse by modulating it with a code signal having autocorrelation characteristics, and then derives a correlation output signal corresponding to the code from the received pulse that is reflected from the target and felt. This method calculates the round trip time of the signal with the corresponding code and calculates the distance or position of the target object, which makes it possible to obtain the same accuracy as the above method with a smaller peak power. I can do it.

However, in this method, in order to further reduce the transmission power and obtain position measurement accuracy equivalent to the above method, a transmission pulse modulated using a relatively long code sequence is transmitted. This is necessary. Therefore, in such a distance measuring device, since the same antenna is used to perform transmission and reception operations alternately, a portion of the received pulse reflected from a relatively short-distance target becomes unreceivable. Such conditions are shown in FIGS. 1(a) to (C).

FIG. 1(a) shows the waveform of the transmission pulse P1 sent out from the transmitter, and FIG. 1(5) shows the waveform of the transmission pulse P1 in FIG. That is, for a short time 1. Fig. 1(C) shows a received pulse P2 reflected from a target at a relatively long distance, that is, a received pulse P2 reflected from a long time t2 and made to enter the receiver. The received pulse P is shown below. In such a state, as can be easily understood from the figure, the received pulse P2 reflected from the target object at a relatively short distance cannot be received. That is, the distance measuring device is in the process of sending out the transmission pulse P+, and it is extremely difficult to perform a reception operation during transmission because it is affected by the transmission wave. Therefore, even with such means, in order to expand the detection range, the code must be made shorter and the transmission power must be increased.
This exposes the disadvantage that the signal processing system becomes more complicated and the number of devices increases, for example, the scale of the power amplifier circuit and the power supply section increases.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and the transmitting section transmits signals of a plurality of code sequences having an autocorrelation characteristic and having an orthogonal relationship to a maximum length code sequence. Forming a composite code signal in which the leading edge of the signal is sequentially delayed from the leading edge and the trailing edge is close to each other, and transmitting a transmission pulse modulated with the composite code signal, and then,
The reception unit uses a matched filter to extract correlation output signals corresponding to the plurality of code sequences from the received pulses that are reflected from the target object, and calculates the round trip time corresponding to the signal of each code sequence. The purpose of the present invention is to provide a distance measuring device that can reduce the transmission power of transmitted pulses, expand the minimum and maximum detection ranges, and improve the distance resolution when calculating the distance between targets by performing detection. do.

[Means for Achieving the Object] In order to achieve the above object, the present invention provides at least a transmitter that sends out a transmission pulse and a receiver that derives a signal indicating the position of the target from the received pulse reflected from the target. The transmitting section includes a code signal generating means for generating signals of a plurality of code sequences having an autocorrelation characteristic and having an orthogonal relationship and having different code lengths, and a transmitting section that generates signals derived from the code signal generating means. timing control means for controlling generation timings of signals of a plurality of code sequences to be generated; Adding means for forming and deriving a composite code signal in which the leading edge is sequentially delayed from the leading edge of the series signal and the trailing edge is close to each other, and modulation is performed using the composite code signal derived from the adding means. and a transmitting means including an antenna device for transmitting a transmission pulse, the receiving unit includes:
a filter section that includes an antenna device and uses a matched filter to derive correlation output signals corresponding to the signals of the plurality of code sequences from the reception pulses that are felt when the transmission pulses are reflected by a target object; and the correlation outputs. The present invention is characterized by comprising a signal processing section that adds the signals and derives a detection signal indicating the position of the target.

[Embodiments] Next, preferred embodiments of the distance measuring device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 schematically shows a PSR to which the distance measuring device of the present invention is applied.

The PSR has a transmitting section 10 and a receiving section 12, and further receives a control signal CS supplied from an external operating function section (not shown), etc.
a control unit 14 that sends out a transmission operation instruction signal Crx and a reception operation instruction signal CIX for causing the transmission unit 10 and the reception unit 12 to operate alternately based on O;
For example, a parabolic antenna 16 that rotates and has a single radiation characteristic, and a TR tube that connects the antenna 16 to the transmitter 10 and the receiver 12 for transmitting and receiving operations are used. It is roughly composed of a transmission/reception switching section 18.

Based on this configuration, the transmitted radio wave W+ transmitted from the antenna 16 is reflected from a target object, for example, the aircraft O5, and is made to enter the antenna 16 again as a received radio wave W.

The transmitting unit 10 operates based on a transmitting operation instruction signal Ctx inputted from the control unit 14, and includes a frequency conversion circuit (not shown),
A transmitter 22 including a front-stage amplifier circuit, a power amplifier circuit, etc., and code sequence signals C1, C2, etc. whose lengths take on values of decreasing length as shown in FIGS. 3(a) to (C). It has a first code generator 24 that generates Cn, a second code generator 26 to an n-th code generator 28. The code sequence signal CI %C2...C, uses an orthogonal relationship or a code that approximates an orthogonal relationship, and has excellent autocorrelation and minimal mutual partial correlation, such as an orthogonal sequence, a Gold sequence, Also, a PN sequence or the like selected to satisfy such properties is preferable.

Then, the code sequence signal C11C2 generated here...
・co is configured to sequentially drive the first and second code generators 24 and 26...the n-th code generator 28 with drive signals T1, Ts2...T□ derived from the timing control circuit 30. will be sent.

Furthermore, the code sequence signals C+ and C2 are supplied to an adder 32, and the code sequence signal CI added by the adder 32
2 and the code sequence signal C1 are supplied to the adder 34, and as shown in FIG.
A composite code signal C12n shown in (Company) is derived. Note that the composite code signal C32° is the code sequence signals C2 and C
1 have sequential delays with respect to the code sequence signal CI, i.e., times t4 and tl, and the trailing edges are close so that they coincide in the illustrated example. is formed. Then, the composite code signal C12 derived here is supplied to the PSK modulator 36. The PS
The K modulator 36 performs phase angle modulation, for example, binary phase angle modulation (B-PSK), on the high frequency signal spontaneously generated by the oscillation circuit, and inputs it to, for example, a frequency conversion circuit of the transmitter 22.
After being formed into a predetermined frequency and pulse width and a predetermined peak power, the signal is supplied to the antenna 16 via the transmission/reception switching unit 18 . It is radiated from the antenna 16 as a transmission radio wave W1. Then, the transmitted radio wave W1 is reflected by a target object, for example, an aircraft O5, and is again transmitted to the receiving unit 12 from the antenna 16 as a received radio wave W2.

The receiving section 12 operates based on a receiving operation instruction signal Cmx from the control section 14, and includes a receiver 42 equipped with a high frequency amplification circuit, a frequency conversion circuit, an intermediate frequency amplification circuit, a four-phase angle detection circuit, etc. (not shown), and the like. An intermediate frequency signal S, which is converted to a predetermined intermediate frequency at the receiver 42. is input. Furthermore, an intermediate frequency signal S2° is input, for example, 5AW
A first matched filter 46 for deriving impulse correlation output signals SKI, S22, . It has a second matched filter 48 and an nth matched filter 50. Here, FIG. 4 shows impulse correlation output signals S21% 322...S, . . . corresponding to the code sequence signals C1 to Ci. Furthermore, the correlation output signal S 21 derived here
SS 22 . The signal processing unit 56 generates a display signal 3 for displaying the two-dimensional position of aircraft 0 on a display device (not shown), for example, on a CRT.
28 is led out to the output terminal T.

By doing this, from the so-called pulse compression effect, if the length of the composite code signal Cl2h is N, then 1/N
An equivalent effect can be obtained with a transmission output power of . Further, the composite code signal CI2 is formed such that the leading edges of each of the code sequence signals C2 and CI are sequentially delayed with respect to the code sequence signal CI, and the trailing edges are close to each other. The corresponding minimum width code sequence signal C7 has a relatively large signal level of the reflected received radio wave W2. This creates a C/N ratio (received power/noise power density) that is relatively equivalent to the longest code sequence signal CI, expands the minimum and maximum detection range, improves distance resolution, and improves short- and long-distance detection. Observation becomes possible.

[Effects of the Invention] As described above, according to the present invention, the transmitter sequentially transmits signals of a plurality of code sequences having an autocorrelation characteristic and having an orthogonal relationship from the leading edge of the signal of the code sequence with the highest flame. A composite code signal is formed in which the leading edge is delayed and the trailing edge is close, and a transmission pulse modulated with the composite code signal is transmitted, and then the receiving part is reflected from the target object. By extracting correlation output signals corresponding to the plurality of code sequences 1 from the received pulses sensed by using a matched filter, and detecting the round trip time corresponding to the signal of each code sequence, For example, in calculating the distance between targets in PSR, SSR, underground structure search equipment, underwater detection/distance measuring equipment, and various distance measuring equipment, it is necessary to reduce the transmission power of the transmission pulse. Remarkable effects such as a reduction in the scale of the amplifier circuit and the power supply section, an expansion of the minimum and maximum detection ranges, and an improvement in distance resolution can be obtained.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the relationship between transmitted pulses and received pulses to explain the operation related to the prior art, and FIG. 2 is a block diagram showing a schematic configuration of a PSR to which the mobile ranging device of the present invention is applied. 3(a) to 3(d) are waveform diagrams illustrating a plurality of code sequence signals having different lengths and a transmission code signal obtained by adding each of the code sequence signals, which are used to explain the operation of the distance measuring device according to the present invention. , FIG. 4 is a waveform diagram showing impulses generated by the receiving section, which is used to explain the operation of the distance measuring device according to the present invention. 10... Transmitting section 12... Receiving section 1
4...Control unit 16...Antenna 1
8... Transmission/reception switching section 22... Transmitter 24
... first code generator 26 ... second code generator 28 ... nth code generator 30 ... timing control circuit 36 ... PSK modulator 46 ... first Matched filter 48...Second matched filter 50...Nth matched filter 52...Addition circuit Wl...Transmission radio wave 0,...Aircraft CI-C,...Code sequence Signal S 21 ” S n n... Correlation output signal Sss.
... Display signal 32.34 ... Adder 42 ... Receiver 56 ... Signal processing section W2 ... Received radio wave 326 ... Addition signal FIG, 3 FIG, 2 FIG, 4

Claims (1)

[Claims] (1) In a ranging device comprising at least a transmitter that transmits a transmission pulse and a receiver that derives a signal indicating the position of the target from the received pulse reflected from the target, the transmitter includes:
A code signal generating means for generating signals of a plurality of code sequences having an autocorrelation characteristic and having an orthogonal relationship and different code lengths, and controlling generation timing of signals of a plurality of code sequences derived from the code signal generating means. and timing control means for controlling the plurality of code sequence signals derived from the code signal generation means in cooperation with the timing control means, sequentially starting from the leading edge of the signal of the code sequence with the maximum length. A transmitting means including an adding means for forming and deriving a delayed composite code signal whose trailing edge is close to each other, and an antenna device for transmitting a transmission pulse modulated with the composite code signal derived from the adding means. The receiving unit includes an antenna device, and a filter unit that employs a matched filter from the received pulse received when the transmitted pulse is reflected by a target object and derives a correlation output signal corresponding to the signals of the plurality of code sequences. and a signal processing unit that adds the correlation output signals and derives a detection signal indicating the position of the target object.