JPS6340883A - Disturbing wave suppressing system - Google Patents

Abstract

PURPOSE:To suppress disturbing waves in a linear/nonlinear FM system pulse compression radar by changing over the sweep polarities of transmitted and received pulses. CONSTITUTION:The output of a modulated pulse generator 1 in an intermediate frequency (IF) band is transmitted via a local oscillator 3a or 3b and a frequency converter 2. Received signals are mixed with the output of the oscillator 3a or 3b to be converted to IF signals by a frequency converter 4 and inputted to a pulse compression filter 5. The frequency of the pulse generator 1 increases from f1 to f2 with time and the frequency band of transmitted pulses are assumed to range from fTL to fTH. The frequencies fL and fH of the oscillators 3a and 3b are selected so as to satisfy expressions fL=fTL-f1 and fH=fTH+f2, respectively. Thus, when a pulse-like FM disturbing frequency sweep polarity agrees with that of transmitted and received signals, the oscillators 3a and 3b are changed over to each other to invert frequency sweep polarities whereby the disturbance can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to an interference wave suppression method for a linear or non-linear E'M type pulse compression radar.

[Prior art] Conventional linear or non-linear FM type pulse compression radars are
tion t.

Radar Systems “(5econd Edi
tion) McGraw-Hllllnternat
ional Company P493-497.

Figure 3 is a system diagram of this method, and in the figure (υ
is a linear or non-linear FM modulation pulse generator, (2) is a transmission system frequency converter, (3) is a local oscillator, (4) is a communication system frequency converter, and (5) is a pulse compression It's a filter.

Next, the operation will be explained with reference to the operation explanatory diagram of FIG. 4. The modulated pulse generator (1) generates modulated pulses in the IP band, and its output has a frequency that changes over time as shown in FIG. 4(a).
The change is shown in FIG. 4(b). Here, we will consider the case where the frequency -i increases with time (hereinafter referred to as "amp chirp").
However, the same operation occurs when the frequency decreases over time (hereinafter referred to as "down chirp"). Further, here, a case of linear FM where the frequency changes linearly with respect to time is illustrated, but the same operation will be performed below for non-linear FM where the frequency increases or decreases non-linearly with respect to time. Now,
The output of the modulated pulse generator (1) is converted into an RF band by the frequency converter (2) using the output of the local oscillator (3), and then transmitted. The received signal Ji3 in the RF band is mixed by the frequency converter (4) on the output of the local oscillator (3), converted into the industrial signal J8, and pulse-compressed by a pulse compression filter (5). This puffless fickle look (
5) has a frequency dispersion characteristic opposite to that of the transmitted pulse, as shown in Figure 4(c), so the received pulse rises in the amplitude direction on the time axis, and as shown in Figure 4(d). A pulse compression rectangle as shown is output.

[Problem that the invention seeks to solve]

Since the conventional pulse compression radar is configured as described above, for pulse-shaped FM interference, if the frequency sweep polarity matches that of the transmitted and received pulses,
There was a problem in that the pulses were compressed in the same way as in the case of reception and reception, and interference was emphasized.

This invention was made to solve the above problems, and the frequency sweep polarity of pulsed FM interference is
The purpose of this is to invert the frequency sweep polarity of the transmitted and received pulses when it matches that of the transmitted and received pulses, thereby suppressing interference.

[Means for solving problems]

The interference wave suppression method according to the present invention switches the frequency sweep polarity of the transmitted and received pulses in a pulse compression radar that uses linear or non-linear FM transmitted and received pulses.

[Effect J As described above, by switching the frequency sweep polarity of the transmitted and received pulses, it is possible to reverse the relationship between the frequency sweep polarity of the pulsed FM disturbance and that of the transmitted and received pulses,
Only interference can be suppressed.

[Embodiment J] Hereinafter, an embodiment of the present invention will be described with reference to the figures. FIG. 1 is an example in which the frequency sweep polarity of the transmitted and received pulses is reversed by switching the frequency of the local oscillator.

In Fig. 1, (1) is the frequency pulse generator for the F band, (2) is the frequency converter for the transmission system, (3a), (3
b) is two types of local oscillators, (4) is a receiving system frequency converter, (5) is a pulse compression filter, and (6) is a changeover switch for the two types of local oscillators.

Hereinafter, the operation of the embodiment will be explained using the operation explanatory diagram shown in FIG.

Figure 2 (a) shows the Ji'M characteristic of the output of the modulated pulse generator (1) in the F band. Here, we will consider the case of an amplifier chirp whose frequency increases from fl to f2 with time. Figure 2(b) shows the smoothness of this output.Now, the 8 wave number bands of the transmitted and received pulses are fr
b to fTH, and if the frequency 1°L of one of the 8-part oscillators (3a) is chosen as fL=f7L-fl, the frequency of the transmitted pulse is as shown in Figure 2 (0) and (dJ). As time passes, fTL increases to fTH, resulting in an up-chirp.If the frequency &f■ of the other local oscillator (3b) is chosen to have the relationship fH=f'TH+fl, the relationship shown in Figure 2 (e8(f)) The frequency of the transmitted pulse decreases from fTH to fTL with time, resulting in a dank chirp. Therefore, by switching the local oscillators (:la) and (3b) with the switch (6), the frequency of the transmitted pulse is It is possible to switch the sweep polarity.

In the above embodiment, the output of the modulation pulse generator is an amplifier chirp, but the same applies to the case of a dakun chirp.

In addition, in the above embodiment 4, an example was shown in which the frequency sweep polarity of the transmitted pulse was changed by switching the local oscillator, but as another method, the variable U and T pulse generators and the pulse compression filter could be upgraded. It is also possible to prepare two sets, one for chirp and one for main chirp, or to operate in two ways and to switch between them.

〔Effect of the invention〕

As described above, according to the present invention, since the j-modification sweep polarity of the transmitted pulse can be switched, the effect of suppressing the pulsed ElAfn writing without compressing it can be obtained. .

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an interference wave suppression system according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of its operation. FIG. 3 is a system diagram of a conventional pulse compression radar, and FIG. 4 is an explanatory diagram of its predecessor. In addition, in the figure, (1) is a modulated pulse generator, (2)
are transmission system frequency converters, (3), (3&), (3b)
is the local yΔ receiver, (4) is the same-wavelength converter in the receiving system, and (5
) is the pulse compression 7 □ (ruter), and (6) is the local oscillator selector switch. In Figure 7!1-21, the same reference numerals indicate the same or equivalent parts. Agent: Masuo Oiwa (JqJ A Q too

Claims (1)

[Claims] An interference wave suppression method characterized by suppressing frequency sweep interference waves in a linear or non-linear FM type pulse compression radar by switching the polarity of the frequency sweep within the transmitted and received pulses.