JPH02130491A - Chirp signal generator - Google Patents

Abstract

PURPOSE:To enable measurement of a distance to a target located at a very long distance and to settle the problem of ambiguity by modulating a chirp signal in phase by a predetermined digital signal. CONSTITUTION:In a reception system, a received chirp signal (d) reflected by a target 3 and received by a reception antenna 4 is time-compressed by a pulse compressor 5. A time difference detector 6 detects a time difference between a pulse signal (e) time-compressed thereby and a timing signal (a). The phase of the time-compressed pulse signal (e) is detected by a phase demodulator 8 and the phase demodulated signal (f) is outputted therefrom. A distance converter 7 can determine an equivalent distance to the target 3 from an output of the time difference detector 6 and the phase demodulated signal (f). Since a transmitted chirp signal (c) is phase-modulated by a predetermined digital signal (b) in synchronization with the timing signal (a) in this way, the chirp signal in each period can be discriminated by phase-modulating the received chirp signal (d).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a chirp signal generator necessary for radar ranging devices and the like.

[Conventional technology]

FIG. 3 is a functional block diagram showing a radar ranging device using an example of a conventional chirp signal generator, and FIG. 4 is a schematic diagram of signal waveforms of various parts for explaining the operation of FIG. 3.

In the conventional chirp signal generator 10, the timing signal a
A pulse stretcher 11 synchronized with the pulse stretcher 11 generates a signal (chirp signal) C' whose frequency changes uniformly, and outputs it as it is from the transmitting antenna 2. The chirp signal d' reflected from the target object 3 and received by the receiving antenna 4 is time-compressed by the pulse compressor 5, and is transmitted to the time difference detector 6.
By detecting the time difference between the timing signal a and the time-compressed received pulse signal e, the distance converter 7
is equivalently finding the distance to the target.

[Problem to be solved by the invention]

In the conventional chirp signal generator described above, since the chirp signal in each period has the same waveform, when the distance to the target becomes very large, that is, the time delay of the received signal is larger than the timing signal period. When it happens,
It becomes impossible to identify the received signal pulses whose time differences are to be detected. This is called ambiguity.
y) is known as a problem.

[Means to solve the problem]

The chirp signal generator of the present invention is a chirp signal generator that periodically and repeatedly generates a chirp signal whose frequency changes uniformly, and includes phase modulation means for phase modulating the chirp signal in synchronization with a timing signal. It is characterized by

〔Example〕

Next, the present invention will be explained with reference to FIGS. 1 and 2.

FIG. 1 is a functional block diagram showing a radar ranging device using an embodiment of the chirp signal generator of the present invention, and FIG.
FIG. 3 is a schematic diagram of signal waveforms of each part for explaining the operation shown in the figure.

In FIG. 1, the chirp signal generator 1 of this embodiment includes a pulse stretcher 11. It is equipped with a digital code generator 12 and a phase modulator 13, and the pulse stretcher 11 generates a signal (chirp signal) whose frequency changes uniformly in synchronization with the timing signal a.
This is the same as the conventional example. Digital code generator 12 generates a predetermined digital signal. Further, the phase modulator 13 is a 0-π modulator that modulates the phase of the chirp signal according to this digital signal C, and transmits the transmission chirp signal C to the transmission antenna 2.

On the other hand, in the receiving system, the signal is reflected by the target object 3 and is reflected at the receiving antenna 4.
The received chirp signal d received by the pulse compressor 5
The time is compressed by Further, the time difference detector 6 detects the time difference between the time-compressed pulse signal e and the timing signal a.

In this embodiment, the phase demodulator 8 detects the phase of the time-compressed pulse signal e (the mutual phase difference for each cycle) and outputs the phase demodulated signal f, and the distance converter 7 uses a time difference detector. The isometric distance to the target object 3 can be determined from the output of 6 and the phase demodulated signal f.

As explained above, according to this embodiment, since the transmission chirp signal C has already been phase modulated by a predetermined digital signal in synchronization with the timing signal a, the reception chirp signal d is phase demodulated in the receiving system. By doing so, it is possible to identify the chirb signal for each period. Therefore, the distance converter 7 can accurately detect the timing signal a and the corresponding received pulse.

In this embodiment, the phase modulation function is used to identify chirp signals for each cycle, but it is clear that the phase modulation function can also be used as a means for transmitting digital signals.

〔Effect of the invention〕

As explained above, according to the present invention, by phase modulating the chirp signal with a predetermined digital signal, the chirp signal for each period can be identified. can also be measured, which has the effect of solving the problem of ambiguity.

3 is a functional block diagram showing a radar ranging device using an example of a conventional chirp signal generator, and FIG. 4 is a schematic diagram of signal waveforms of each part to explain the operation of FIG. 3. FIG.

1.10... Chirp signal generator, 2... Transmitting antenna, 3... Target, 4... Receiving antenna, 5...
- Pulse compressor, 6... Time difference detector, 7... Distance converter, 8... Phase demodulator, 11... Pulse expander, 12... Digital code generator, 13... Phase modulator.

Claims (1)

[Claims] 1. A chirp signal generator that periodically and repeatedly generates a chirp signal whose frequency changes uniformly, the chirp signal generator comprising phase modulation means for phase modulating the chirp signal in synchronization with a timing signal.