JPH04315978A - Reception device - Google Patents

Abstract

PURPOSE:To realize highly sensitive reception and also to enable measurement of the input frequency of an incoming radio wave. CONSTITUTION:A miner 3 which provides dispersion compensation characteristics to the output of a phase modulator 6 to mix the output with high frequency signals received and convert the output into an intermediate frequency, and a dispersion type delay line 9 which tilts delay time as to the output of the mixer 3 within an intermediate frequency band, are provided. A signal compressor 7 time compresses a phase modulation signal obtained through the dispersion type delay line 9, so that a time compression signal is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving device that detects radar radio waves and the like with high sensitivity.

0002

2. Description of the Related Art FIG. 7 is a block diagram showing a conventional receiving apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 202127/1999 filed by the same applicant as the present application. In the figure, 1 is a receiving antenna, 2 is a receiving A band pass filter (hereinafter referred to as BPF) that determines the frequency, 3 a frequency mixer, 4 a local oscillator that outputs a coherent local oscillation signal, 5 a code generator, and 6 a time-series code for the local oscillation signal. A phase modulator that performs phase modulation, 7 a signal compressor, and 8 a detector that performs envelope detection.

Next, the operation will be explained. Radio waves received by the receiving antenna 1 reach the mixer 3 via the BPF 2. On the other hand, the coherent local signal outputted from the local oscillator 4 is modulated by the time-series code generated from the code generator 5 so as to cause a phase change of 0 or π (180°) in the phase modulator 6. . This time series code is
For example, PN code (Pseudo-Noise Code
It is a code for frequency spreading, such as e) and Barker code, and here it is 1
This is an M series consisting of 5 elements. FIG. 7 is a diagram showing this relationship, and FIG. 8(a) shows the code permutation of 15 elements, and the autocorrelation function of the signal subjected to this phase modulation is shown in FIG. 8(b), (
c) is known to occur. In other words, time width T=1
When modulated by 5τ, the spectrum shown in Fig. 8(c) is spread in terms of frequency, and the waveform obtained by time-compressing this using a matched filter has an amplitude amplified by 15 times as shown in Fig. 8(b). That's what you get. Further, FIG. 9 shows an example of the configuration of this matched filter. This is 1 from the tapped delay line.
This device has three intermediate taps, and after phase-shifting the output signals with a time difference τ between the individual taps by 0 or π, they are combined and summed at the output. As a specific example, devices using surface acoustic waves are well known.

Furthermore, the mixer 3 performs not only frequency conversion to an intermediate frequency, but also phase modulation using the above M sequence. After that, if the signal is detected, a time-compressed signal shown in FIG. 8(b) can be obtained. Usually, the pulse width of a radar signal is often about 1 μsec, and the shortest pulse width is about 0.1 μsec. Therefore 1μsec/15=
If approximately 67 nsec is set as the time of τ, the bandwidth of the device that receives this is generally 30 MHz or more, so
This is a sufficient bandwidth for passing this modulated wave. Therefore, in this case, the sensitivity of the receiving device can be amplified 15 times, but since the noise also increases, it is actually possible to improve the sensitivity by 10log15=approximately 12 dB. In order to improve the detection probability of radio waves, a wideband receiving device has no choice but to use a wider bandwidth than the originally optimal bandwidth for signals with long pulse widths, but as mentioned above, the reverse is true. It is possible to improve reception sensitivity by spreading the signal.

[0005]

[Problems to be Solved by the Invention] Since the conventional receiving device is configured as described above, the phase modulator 6 simply phase-modulates the time-series code, and the intermediate frequency amplification stage performs time compression. The time at which the signal is transmitted is synchronized with the modulation time, and therefore, the compressed signal appears only at this synchronized time, so other times are not very important and can only improve reception sensitivity. Originally, there were problems such as the inability to measure the carrier frequency of incoming radio waves, which is necessary for such a wideband receiving device.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a receiving device that can recognize the reception frequency of incoming radio waves while realizing highly sensitive reception.

[0007]

[Means for Solving the Problems] A receiving device according to the present invention includes a mixer that gives the output of a phase modulator a dispersion compensation characteristic and mixes it with a received high frequency signal to convert it into an intermediate frequency, and an output of the mixer. A distributed delay line is provided to tilt the delay time within the intermediate frequency band, and a signal compressor time-compresses the phase modulated signal obtained through the distributed delay line to obtain a time-compressed signal. It is something.

[0008]

[Operation] The distributed delay line in this invention is a delay line that uses all intermediate frequencies as a passband, and as a result, the time when the phase modulation is applied to spread and the time when the time is compressed is not a constant time difference, and when an incoming signal is received. The delay time is made to vary depending on the frequency so that it changes in proportion to the signal frequency,
This makes it possible to identify signal frequencies while improving reception sensitivity.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 9 is a first distributed delay line (hereinafter referred to as DDL) that changes the frequency at the time of signal compression;
10 is a second DDL that compensates for the frequency characteristics caused by the first DDL 9. Further, other blocks that are the same as those shown in FIG. 7 are given the same reference numerals, and redundant explanation thereof will be omitted. Moreover, FIGS. 2(a) and 2(b) are explanatory diagrams showing the delay time versus frequency characteristics of these first DDL 9 and second DDL 10, and the first DDL 9 is down as shown in FIG. 2(b). It is a wideband distributed delay line with chirp. This dispersion characteristic has a slope of −μ(sec/
HZ ), and the intermediate frequency (lower limit x fIL to upper limit x
fIH) as a passband. On the other hand, the dispersion characteristic of the second DDL 10 has a slope of μ(sec
Although it is a distributed delay line that has an up-chirp characteristic of /HZ), it is a delay line that only needs to pass the spread bandwidth due to phase modulation, and does not have a very wide pass band width. Therefore, compared to the first DDL 9, the delay time is not so long and is simple.

Next, the operation will be explained. FIG. 3(a) is a diagram showing that incoming radio waves having different frequencies, signal S1 and signal S2, are simultaneously received, and is a simulated representation of the relationship between the frequency and time of the signal at the output of the BPF 2. On the other hand, the local oscillator signal (fLO) is the output of the phase modulator 6 and has the relationship shown in FIG.
When passing through the DDL 10, the delay time has dispersion characteristics and changes to the relationship shown in FIG. 3(c). Therefore, when the local oscillation signal resulting from this result and the output signal of BPF 2 are mixed in the mixer 3, the frequency is converted to an intermediate frequency, and at the same time, the spreading (dispersion delay characteristic) due to phase modulation is superimposed, and the result is shown in FIG. 3(d). It comes to show. Next, when the output of this mixer 3 is passed through the first DDL 9, the delay time shown in FIG. 3 (
A difference as shown in e) arises. In this example, a time difference of 14τ occurs, and at the same time, the dispersion characteristics due to diffusion also change to the first D.
Since the DL9 and the second DDL10 have opposite slopes, they cancel each other out and return to the originally diffused state, that is, the state shown in FIG. 3(b). After passing this through a signal compressor 7, a detector 8
When envelope detection is performed using the above method, the time-compressed waveforms of the signal S1 and the signal S2 can be obtained separately as shown in FIG. 3(f). Therefore, it is possible to separate and detect the signal S1 and the signal S2 that arrived at the same time, and it is possible to understand the relationship in which the frequency of the arriving signal is calculated based on the time of the detected waveform. In this example, when the intermediate frequency changes from fIL to fIH, the output time of the detected waveform is output from 1τ to 15τ. Since it changes proportionally during this time, the incoming signal frequency can be calculated conversely from the output time. Further, the up-chirp and down-chirp characteristics in the first DDL 9 and the second DDL 10 can be considered to have opposite polarities depending on the relationship between the RF high frequency and the local oscillation frequency in the mixer 3, etc.

[0011] In the above embodiment, an example was shown in which the second DDL 10 compensates for the dispersion characteristics of the first DDL 9, but since the second DDL 10 does not have a wide passband width, the dispersion time is also short. . Therefore, as shown in FIG. 4, a BPF 11 is used instead of the second DDL 10,
Limiting the spread of the spectrum due to spreading causes slight waveform distortion when compressing the signal, but if the dispersion characteristics are gentle, it is effective for separating multiple signals.
It is also cheaper in price.

Further, in the above embodiment, the case of two-phase modulation of 0 and π was shown, but when phase modulation is performed with four phases as shown in FIG.
By forming a vector modulator by dividing into two sequences (X, Y axes) with a phase difference of 90°, multiphase modulation is possible as shown in Figure 6, and this allows the frequency spectrum when spread. This is effective for separating multiple signals. That is, by performing phase modulation of 0° or 180° (π) with the phase modulators 6a and 6b and combining the results, four types of 45°, 135° as shown in Equations 1 to 4 are obtained.
It can be used as a phase modulator that can have a phase relationship of 225°, 225°, or 315°.

[0013]

[Math 1]

[0014]

[Math 2]

[0015]

[Math 3]

[0016]

[Math 4]

The present invention is also effective for the same reason when the number of code elements increases and the unit pulse width (τ) needs to be narrowed. Further, in the above example, an example of the characteristic shown in FIG. 2 was explained as a distributed delay line, but it can also be applied to a case having a stepped dispersion characteristic.

[0018]

As described above, according to the present invention, there is provided a mixer that gives a dispersion compensation characteristic to the output of a phase modulator, mixes it with a received high frequency signal, and converts it into an intermediate frequency, and an intermediate A distributed delay line that slopes the delay time within a frequency band is provided, and a signal compressor is configured to time-compress the phase modulated signal obtained through the distributed delay line.
Since the configuration is configured to obtain a time-compressed signal, it is possible not only to compress the received signal and improve reception sensitivity, but also to identify the signal frequency, and also to arbitrarily determine the number of bits of the PN code. Therefore, there is an effect that the compression ratio can be set freely.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a receiving device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing frequency-delay time characteristics of first and second distributed delay lines in FIG. 1;

FIG. 3 is a conceptual diagram showing the delay time relationship of signals in each part of the block in FIG. 1;

FIG. 4 is a block diagram showing a receiving device according to another embodiment of the invention.

FIG. 5 is a block diagram showing a receiving device according to still another embodiment of the present invention.

FIG. 6 is an explanatory diagram showing four phase-related signals created using a phase modulator.

FIG. 7 is a block diagram showing a conventional receiving device.

FIG. 8 is an explanatory diagram showing the relationship between a time series code, a time compression waveform, and a spread spectrum waveform.

FIG. 9 is a connection diagram showing the configuration of a matched filter.

[Explanation of symbols]

3 Mixer 4 Local oscillator 5 Code generator 6 Phase modulator 7 Signal compressor 8 Detector 9 Distributed delay line

Claims (1)

[Claims] Claim 1: A code generator that generates a time-series code, a phase modulator that phase-modulates a local signal from a local oscillator with the code, and an output of the phase modulator that has dispersion compensation characteristics. a mixer that mixes the received high-frequency signal with the received high-frequency signal and converts it to an intermediate frequency; a distributed delay line that tilts the delay time within the intermediate frequency band for the output of the mixer; and a phase modulation obtained through the distributed delay line. A receiving device comprising a signal compressor that time-compresses a signal, and a detector that extracts the time-compressed signal from the output of the signal compressor.