JP2000338226A - Radar equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar equipment which is simplified in constitution while the receiving ability of the equipment is improved in such a way that the equipment is enabled to process received signals by band-pass sampling. SOLUTION: Radar equipment is constituted in such a way that the local frequency signal of the same local oscillator 3 is led to a reception-side A/D converter 2 and a transmission-side frequency converter 5 so that a coherent relation may be established between received signals processed in a receiving section and transmitting signals generated in a transmitting section. In addition, the radar equipment is enabled to perform band-pass sampling by setting the passing band width of a band-pass filter 1 which limits the band of input signals at the 1/2 (fs/2) of the sampling frequency fs of the converter 2 and, at the same time, the local frequency of the oscillator 3 at 17.14 MHz (30 MHz×4/7) and 18.46 MHz (60 MHz×4/13), and the sampling frequency fs of the converter 2 at 4/7 or 4/13 of the frequency of the input signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radar device such as a pulse radar.

[0002]

2. Description of the Related Art Nyquist sampling and oversampling are known as methods for sampling an analog signal. This is a method of performing sampling at a sampling frequency twice or higher than the highest frequency among the frequency components of a given signal.

[0003] In a recent radar apparatus or the like, an IF that performs a sampling process on an intermediate frequency signal (IF signal) without dropping a received radio frequency signal to a baseband.
Direct sampling is used. According to IF direct sampling, signals can be received with extremely high accuracy and high fidelity.

However, conventionally, there are various problems in sampling the IF signal by the Nyquist sampling or the oversampling. That is, since the current sampling device can only sample a signal up to about 2 MHz at most, it is necessary to down-convert the IF signal to this frequency. Speaking of 2 MHz is a very low frequency that is not usually used in the field, and requires a multi-stage frequency converter to drop from the radio frequency to this level. For this reason, there have been problems such as an enlargement of the configuration and an increase in processing errors resulting in impaired signal reproduction fidelity.

[0005] Bandpass sampling is known as a technique for sampling an analog signal. In this method, an alias is generated in an output by intentionally lowering a sampling frequency with respect to an input signal frequency, and a frequency drop is simultaneously performed at the time of sampling by actively using the alias. By appropriately limiting the band of the input signal using a band filter, such a sampling process can be performed.

However, when bandpass sampling is performed, downconversion of the received signal is inevitably performed in the process. For this reason, in order to apply bandpass sampling to a radar apparatus, it is necessary to maintain a coherency between a transmission signal and a reception signal, so that a transmission signal having a high frequency must be generated while maintaining the coherency between the reception signal and the reception signal. For this reason, there is a problem that generation of a transmission signal involves great difficulty.

[0007]

As described above, the conventional radar apparatus using IF direct sampling has problems that the configuration is enlarged and the fidelity of signal reproduction is impaired. On the other hand, there is a problem that it is difficult to generate a transmission signal when performing band-pass sampling in a radar device.

[0008] The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a radar apparatus which enables reception processing by band-pass sampling, thereby improving the reception performance and simplifying the configuration.

[0009]

In order to achieve the above object, the present invention comprises a local oscillator, a receiving unit, and a transmitting unit, wherein the receiving unit receives a radio frequency signal from an incoming radio frequency signal. A frequency-converted reception intermediate frequency signal is provided, a band limiting filter that limits the bandwidth of the reception intermediate frequency signal, and a sampling clock generated from a local oscillation signal generated by the local oscillator. And an analog / digital converter for sampling and digitally converting the band-limited reception intermediate frequency signal.
Digital-to-digital conversion means; and signal processing means for performing reception signal processing on digital data sent from the analog / digital conversion means, wherein the transmission section generates a local oscillation signal based on the local oscillation signal generated by the local oscillator. Transmission signal generating means for generating a transmission signal, wherein the band-limiting filter limits the bandwidth of the reception intermediate frequency signal to の or less of the frequency of the sampling clock, and sets the frequency of the sampling clock to , Wherein the frequency is not more than twice the highest frequency of the received intermediate frequency signal.

In this case, the analog-to-digital converter performs so-called band-pass sampling on the received intermediate frequency signal. That is, the received intermediate frequency signal is digitally converted and downconverted in an equalized manner by folding the signal. This makes it possible to reduce the number of stages of the downconverter for lowering the frequency of the received signal, thereby simplifying the configuration and improving the fidelity of signal reproduction.

Further, in the transmission signal generating means,
Since the transmission signal is generated based on the local oscillation signal generated by the local oscillator, a coherent signal is generated between the reception signal processed by the reception unit and the transmission signal generated by the transmission unit. Relationship can be provided. Also, a transmission signal having a high frequency can be easily generated while maintaining coherency.

In the radar apparatus, it is essential to maintain coherency between the transmission system and the reception system, and the function as the radar apparatus can be satisfied only by adopting the above means.

Further, in the present invention, a waveform memory in which waveform data of a transmission signal is stored in the transmission unit, and a waveform data stored in the waveform memory are read out, and a local oscillation signal generated by the local oscillator is converted into a conversion clock. Digital / analog conversion means for converting the waveform data into analog to obtain a transmission signal waveform, wherein the transmission signal generation means converts the transmission signal based on the transmission signal waveform obtained by the digital / analog conversion means. It is characterized by being generated.

By employing such means, the waveform of the transmission signal can be set arbitrarily, and can be applied, for example, as an intra-pulse modulation radar.

Further, a frequency divider for dividing the local oscillation signal generated by the local oscillator is provided, and the analog / digital conversion means is operated using an output of the frequency divider as a sampling clock, and the transmission is performed. The signal generation means may generate the transmission signal by frequency-converting the transmission signal waveform obtained by the digital / analog conversion means based on the output of the frequency divider.

With this configuration, a local oscillator having a high oscillation frequency can be used, and the conversion clock of the digital / analog conversion means can be increased. This facilitates generation of a transmission waveform.

In particular, the frequency of the sampling clock may be set so that the center frequency of the band-limited received intermediate frequency signal is (odd / 4) times the frequency of the sampling clock.

In particular, the frequency of the transmission signal waveform transmitted from the digital / analog conversion means may be equal to or more than １ ／ of the frequency of the sampling clock.

In this way, the load on the received signal processing in the signal processing means can be reduced, which can also simplify the configuration.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a main configuration of a transmitting / receiving apparatus according to the present embodiment. FIG. 1 shows only a portion that performs processing related to an intermediate frequency (IF) signal. Actually, an RF receiving unit that receives a radio frequency signal and converts it into an IF signal and an RF transmitting unit that converts the generated IF signal into a radio frequency signal are connected to the outside of the illustrated portion.

30 transmitted from an RF receiver (not shown)
The IF signal of MHz to 60 MHz is applied to an analog / digital (A / D) converter 2 via a bandpass filter 1 and is converted into digital data. This digital data is applied to a digital filter 4, and the I / Q
Various signal processing such as signal generation is performed.

The A / D converter 2 has a built-in sampling function, and operates using a local frequency signal generated by the local oscillator 3 as a sampling clock. This local frequency signal is also provided to a frequency converter 5, where it is converted into an intermediate frequency signal for transmission. The IF signal of 30 MHz to 60 MHz generated in this way is supplied to an RF transmitter (not shown) via the band pass filter 6.

In FIG. 1, the sampling function is denoted by A.
It may be provided outside the / D converter 2. As the digital filter 4, in addition to the one that performs high-speed convolution operation processing using DFT (Discrete Fourier Transform), the one described in, for example, Japanese Patent No. 2659963 can also be applied. The digital filter described in the above publication discloses the A / A
A receiver for performing I / Q detection of this A / D converted signal using a digital filter having filters for calculating the in-phase component and the quadrature component by performing a single system up to the D conversion process The DC offset generated by the A / D conversion is removed by providing a filter for removing the zero frequency component in the filter constituting the digital filter.

In the digital filter 4, I / Q
Signal generation is not essential, and data is thinned out or resampled (interpolation processing is performed so that the output data rate is not limited to 1 / natural number of the input data rate)
Depending on the application, it is also possible to perform only. FIG.
Although 30 MHz and 60 MHz were set as the intermediate frequencies,
It is not necessarily limited to this numerical value.

Next, the operation of the above configuration will be described.
First, the principle of bandpass sampling will be described with reference to FIG. In normal sampling, FIG.
As shown in (a), the bandwidth of the input signal after passing through the band-pass filter is limited to １ ／ or less of the sampling frequency fs, and the maximum frequency of the input signal is reduced to fs / 2 or less by down-conversion. Therefore, the center frequency f0 of the input signal is fs / 2 or less.

On the other hand, in band pass sampling,
Restricting the bandwidth of the input signal to fs / 2 or less is the same as described above, but the maximum frequency is not limited to fs / 2 or less, and the input signal is given in the area where the alias in FIG. As a result of sampling in this way,
The output of the A / D converter 2 is folded as shown in FIG. 2 (c), and the same result as that obtained by down-conversion can be obtained. Moreover, since the bandwidth t of the input signal is fs / 2 or less, the alias components shown in FIG. 2B are not added at the output, and only one component is extracted. Therefore, no noise component is generated in the sampling output.

In particular, if f0 is an odd multiple of fs / 4, that is, if fs is (4 / odd) times f0, FIG.
To get an array like In this embodiment, the local frequency of the local oscillator 3 is set to 17.14 MHz (30
MHz × 4/7) and 18.46 MHz (60 MHz)
× 4/13). Therefore, the sampling frequency fs of the A / D converter 2 is also 4/7 or 4/13 of the frequency of the input signal.

By setting the pass band of the band-pass filter 1 and the sampling frequency of the A / D converter 2 as described above, band-pass sampling can be performed on the input signal, and the same result as down-conversion is equivalently obtained. can get. Therefore, the signal given to A / D converter 1 can be given as the intermediate frequency (IF), and the number of down-converting stages after reception can be reduced. Thereby, the configuration of the RF receiving stage and the digital filter can be particularly simplified, which can contribute to the simplification of the configuration of the entire radar apparatus. Further, the fidelity of signal reproduction can be improved.

On the other hand, in the above configuration, the local frequency signal generated by the local oscillator 3 is provided to the frequency converter 5, and the frequency converter 5 generates a transmission intermediate frequency signal. That is, since the frequency signal generated by the same oscillation source is guided to both the reception side and the transmission side, the reception signal processed by the reception unit and the transmission signal generated by the transmission unit It is possible to have a coherent relationship between them.

As described above, in this embodiment, the local frequency signal of the same local oscillator 3 is converted to the A / D converter 2 on the receiving side.
And a frequency converter 5 on the transmission side, thereby providing a coherent relationship between the reception signal processed by the reception unit and the transmission signal generated by the transmission unit. . Further, the pass band width of the band-pass filter 1 for limiting the band of the input signal is set to fs / 2 of the sampling frequency of the A / D converter, and the local frequency of the local oscillator 3 is set to 17.14 MHz (30 MHz × 4 /
7) and 18.46 MHz (60 MHz x 4/13)
The bandpass sampling can be performed by setting the sampling frequency fs of the A / D converter 2 to 4/7 or 4/13 of the frequency of the input signal.

By doing so, it is possible to provide a radar apparatus that can perform band-pass sampling while maintaining coherency between the transmission system and the reception system.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. In FIG.
The same reference numerals are given to the same parts as those described above, and only different parts will be described here.

In FIG. 2, the local frequency signal from the local oscillator 3 is branched into two, one of which is supplied to a digital / analog (D / A converter) 8, and the other is supplied via a frequency divider 7 to an A / D converter. It is provided to the converter 2 and the frequency converter 5. The output of the frequency converter 5 is a mixer 11
And is mixed with the output of the D / A converter 8 via the band pass filter 10 and output as a transmission IF signal via the band pass filter 6.

The D / A converter 8 reads out the waveform data stored in the waveform memory 9 in accordance with a given clock and converts it into analog. In the present embodiment, a waveform subjected to intra-pulse modulation is stored in the waveform memory 9, thereby realizing a chirp radar.

In the above configuration, the local frequency of the local oscillator 3 is set to 34.29 MHz (30 MHz × 8/7).
And 36.92 MHz (60 MHz × 8/13), which is used as the conversion clock of the D / A converter 8.
Also, this local frequency is divided by half, and this is divided by A /
This is used as the conversion clock of the D converter. Therefore, the clock speed of the D / A converter is twice the clock speed of the A / D converter, and the waveform can be read at high speed. Generally, D / A
It is easy to provide a high-speed read clock to the converter, and it is not limited to twice the clock speed of the A / D converter.

Thus, the center frequency of the output from the D / A converter 8 is 3/4 times the sampling frequency (3/8 times the local frequency of the local oscillator 3). this is,
Since the frequency is three times the frequency after sampling at the time of reception, the fractional band can be reduced to １ ／. This signal
After mixing with the difference frequency signal generated by the local oscillator 5, a transmission signal is extracted via the band-pass filter 6. Note that the local oscillator 5 may generate a sum frequency signal depending on the band setting of the band-pass filter 6.

Since the fractional band is reduced to 1/3, it is extremely easy to realize the bandpass filter 6 as compared with the related art. That is, in the conventional IF direct sampling method, since the output signal of the D / A converter 8 is set to 1/4 of the sampling frequency, the fractional band is 100% or more, and it is difficult to realize the bandpass filter 6. On the other hand, in the present embodiment, a higher frequency signal is generated by giving a high frequency clock to the D / A converter 8, so that the fractional band can be reduced.
As a result, a transmission filter can be easily realized.

As in the first embodiment, it is possible to easily generate a high-frequency transmission signal while maintaining coherency between the transmission system and the reception system, and the band-pass sampling is performed. The same is true for In addition, in the present embodiment, since the waveform data subjected to the intra-pulse modulation is stored in the waveform memory 9, realization as a chirp radar can be achieved.

That is, in the present embodiment, the reception processing by band pass sampling can be performed in the chirp radar, whereby the structure can be simplified while improving the reception performance.

The present invention is not limited to the above embodiment. One of the basic ideas of the present invention is to provide a signal generated by the same oscillator to a transmission system and a reception system. According to this, it is possible to consider a further simplified configuration as shown in FIG. In FIG. 4, the transmission IF signal is generated directly by the local oscillator 3 and
It is used as a conversion clock of the D converter 2. Also by this, by setting the local frequency of the local oscillator 3 and the pass band of the band-pass filter 1 as appropriate, the same effect as in the first embodiment can be obtained.

Although the frequency divider 7 is used in the second embodiment, the D / A may be used depending on the setting of the local frequency.
It is also conceivable to connect a multiplier before the converter 8. In short, a signal generated by the same transmission source may be guided to the transmission system and the reception system.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0043]

As described above in detail, according to the present invention, it is possible to perform reception processing by band-pass sampling in a radar apparatus, thereby enabling highly accurate and faithful reception processing. The configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a transmission / reception device according to a first embodiment of the present invention.

FIG. 2 is a diagram used to explain the principle of bandpass sampling.

FIG. 3 is a block diagram illustrating a configuration of a transmission / reception device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing another example of the embodiment of the present invention.

[Explanation of symbols]

 1, 6, 10 band-pass filter 2 analog / digital (A / D) converter 3 local oscillator 4 digital filter 5 frequency converter 7 frequency divider 8 digital / analog (D / A) conversion Unit 9: Waveform memory 11: Mixer

Claims (8)

[Claims] 1. A local oscillator, a receiving unit, and a transmitting unit, wherein the receiving unit is provided with a receiving intermediate frequency signal obtained by frequency-converting an incoming radio frequency signal, and a band of the receiving intermediate frequency signal is provided. A band limiting filter for limiting a width, an analog for generating a sampling clock from a local oscillation signal generated by the local oscillator, sampling the band-limited received intermediate frequency signal based on the sampling clock, and converting the signal to a digital signal. / Digital conversion means; and signal processing means for performing reception signal processing on digital data transmitted from the analog / digital conversion means, wherein the transmission section also receives a local oscillation signal generated by the local oscillator. And a transmission signal generating means for generating a transmission signal, wherein the band-limiting filter includes the reception intermediate frequency. Radar for limiting the bandwidth of several signals to less than half the frequency of the sampling clock, wherein the frequency of the sampling clock is less than twice the highest frequency of the received intermediate frequency signal. apparatus. 2. The transmitting section reads a waveform data stored in a waveform memory storing waveform data of a transmission signal, and reads the waveform data stored in the waveform memory using a local oscillation signal generated by the local oscillator as a conversion clock. Digital / analog conversion means for converting data into analog to obtain a transmission signal waveform, wherein the transmission signal generation means generates the transmission signal based on the transmission signal waveform obtained by the digital / analog conversion means The radar device according to claim 1, wherein: 3. A frequency divider for dividing a local oscillation signal generated by the local oscillator, wherein the analog / digital conversion means operates using an output of the frequency divider as a sampling clock. The transmission signal generation means generates the transmission signal by frequency-converting a transmission signal waveform obtained by the digital / analog conversion means based on an output of the frequency divider. 3. The radar device according to 2. 4. The sampling clock frequency is set so that the center frequency of the band-limited received intermediate frequency signal is (odd / 4) times the frequency of the sampling clock. The radar device according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the signal processing unit generates an alias in an output of the analog / digital conversion unit.
4. The radar apparatus according to claim 1, further comprising a digital filter for removing the alias. 6. The radar apparatus according to claim 1, wherein said signal processing means generates an I signal and a Q signal from digital data transmitted from said analog / digital conversion means. . 7. The radar according to claim 6, wherein the signal processing means performs data thinning processing and / or resampling on digital data sent from the analog / digital conversion means. apparatus. 8. The radar apparatus according to claim 3, wherein a frequency of a transmission signal waveform transmitted from said digital / analog conversion means is set to be not less than half of a frequency of said sampling clock.