JP4937782B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar apparatus, and more particularly to a radar apparatus for detecting a target existing outside and obtaining information related thereto.

  In general, a radar apparatus radiates electromagnetic waves into space, receives a reflected signal reflected by a target (object), and performs signal processing to obtain information on the target.

  When measuring the distance between the radar and the target, the target distance information is often obtained by performing some modulation on the transmitted wave. For example, in the case of a radar of the FMCW (Frequency Modulation Continuous Wave) method or the FMICW (Frequency Modulation Interrupted Continuous Wave) method, the target distance is obtained by applying frequency modulation to the transmission wave so that the transmission frequency changes linearly with time. A radar system that measures relative speed is known (for example, see Non-Patent Document 1).

  In the FMCW radar, the frequency modulation pattern of the reception wave obtained by reflection from the target is shifted from the transmission wave by the amount of propagation delay while the radio wave reciprocates between the radar and the target. Therefore, by mixing the transmission wave and the reception wave, a reception signal (beat signal) having a frequency (beat frequency) between the transmission wave and the reception wave is obtained. Since the beat frequency is determined by the target distance, if the beat frequency is calculated by frequency analysis of the beat signal, the target distance can be known. Actually, the beat signal depends not only on the distance but also on the target line-of-sight speed (Doppler speed). Therefore, observation by frequency modulation (up-chirp modulation) in which the transmission frequency increases with time and observation by frequency modulation (down-chirp modulation) in which the transmission frequency decreases with time are combined, and the beat frequencies obtained from each observation are combined. Thus, the target distance and the Doppler frequency can be calculated.

  As a frequency analysis method for beat signals, a Fourier transform method is often used. In addition to the function of calculating the beat frequency, the Fourier transform has an effect of improving the signal-to-noise ratio (SN ratio) by coherent integration. When N points are sampled from the time series of beat signals and N-point discrete Fourier transform is performed, the SN ratio becomes N times.

M.I.Skolnik, “Introduction to Radar Systems”, Third Edition, p.195-p.197, McGraw-Hill, 2001

  In a radar that performs distance measurement by frequency modulation, such as FMCW radar and FMICW radar, the time length of a signal subjected to frequency analysis processing, that is, Fourier transform, is the time length of one frequency modulation, for example, up-chirp modulation. If there is, the time length from the lowest value to the highest value is almost equal to the time length.

  Even if a time unit of frequency modulation sufficient to obtain a sufficient S / N ratio for observing a target at a short distance is set, a sufficient S / N ratio cannot be obtained at a long distance. There was a problem that the defined detection performance could not be satisfied.

  On the contrary, when the time unit of frequency modulation is set according to the long distance, the frequency modulation is performed at a short time and at a time period more than necessary. For example, in the case of a radar that monitors obstacles, it is desirable to measure obstacles at short distances with high time resolution. However, if priority is given to detection performance at long distances, sufficient time resolution at short distances can be secured. There was a problem that it was not possible.

  The present invention has been made to solve such a problem, and an object of the present invention is to obtain a radar apparatus capable of improving both short-distance and long-distance target detection performance.

The present invention is a radar device that radiates a wave in space, receives a wave reflected and scattered by an object existing in the space, and measures the object by performing signal processing on the received wave. A transmitting antenna that radiates the wave in space, a receiving antenna that inputs the wave reflected and scattered by the object from space, and a receiving unit that generates a received signal by detecting the received wave input from the receiving antenna And taking out a received signal in a predetermined time range, and applying a Fourier transform to the received signal, a Fourier transform unit for calculating a received signal Fourier transform, and the received signal Fourier transform calculated in a plurality of time ranges, and a integration processing unit that performs integration for each identical frequency, the wave that is radiated into space from the transmission antenna is within a predetermined time interval The predetermined time range in which the Fourier transform unit extracts a received signal to be subjected to Fourier transform is linearly frequency-modulated, and is substantially equal to a time interval of frequency modulation. This is a radar apparatus that integrates the received signal Fourier transform after correcting the phase in an amount proportional to the relative speed of the signal and the difference in frequency modulation start time .

The present invention is a radar device that radiates a wave in space, receives a wave reflected and scattered by an object existing in the space, and measures the object by performing signal processing on the received wave. A transmitting antenna that radiates the wave in space, a receiving antenna that inputs the wave reflected and scattered by the object from space, and a receiving unit that generates a received signal by detecting the received wave input from the receiving antenna And taking out a received signal in a predetermined time range, and applying a Fourier transform to the received signal, a Fourier transform unit for calculating a received signal Fourier transform, and the received signal Fourier transform calculated in a plurality of time ranges, and a integration processing unit that performs integration for each identical frequency, the wave that is radiated into space from the transmission antenna is within a predetermined time interval The predetermined time range in which the Fourier transform unit extracts a received signal to be subjected to Fourier transform is linearly frequency-modulated, and is substantially equal to a time interval of frequency modulation. Since the radar apparatus integrates the received signal Fourier transform after correcting the phase proportional to the difference between the relative speed and the frequency modulation start time , the detection process is performed in a short period at a short distance where the SN ratio of the received signal is sufficiently high. Repeatedly, integration processing can be performed in a long time range even at a long distance where the S / N ratio of the received signal is not sufficiently high, so that it is possible to improve target detection performance at both short distance and long distance.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the configuration of a radar apparatus according to Embodiment 1 of the present invention. In FIG. 1, 001 is an oscillator that generates a transmission wave, 002 is a distributor that divides the transmission wave, 003 is a transmission antenna that radiates the transmission wave to space, 004 is a reception antenna that takes a reception wave from space, and 005 is a transmission wave. And 006 is a Fourier transform unit that performs a Fourier transform on the beat signal, and 007 is a power calculation unit that obtains a power spectrum by calculating the power of the beat signal Fourier transform. 008 is a first detection unit for detecting a spectrum peak from the power spectrum, 009 is a first detection signal storage unit for storing the signal detected by the first detection unit 008, and 010 is stored in the first detection signal storage unit 009. A first detection distance measurement speed measurement unit that performs distance measurement speed measurement from the signal, 011 a phase compensation amount calculation unit that calculates a compensation amount of a phase shift between sweeps, 12 is a phase compensation unit that corrects the phase of the signal stored in the first detection signal storage unit 009 using the phase compensation amount calculated by the phase compensation amount calculation unit 011. 013 is a coherent integration between sweeps. An inter-sweep integration unit 014 is a second detection unit that performs detection processing on the signal after the sweep integration. The mixer 005 constitutes a receiving unit.

Next, the operation of the radar apparatus according to Embodiment 1 of the present invention will be described.
The oscillator 001 generates a transmission wave. In the case of the FMCW method or the FMICW method, the oscillation frequency is controlled to change linearly with time. The transmission wave is input to the transmission antenna 003 via the distributor 002. The transmission antenna 003 emits a transmission wave to space. The transmitted transmission wave is reflected by an object (target object) existing in the space. Hereinafter, this object that reflects the transmission wave will be referred to as a reflecting object. The reception antenna 004 inputs a reflected wave from the reflecting object from the space and inputs it as a received wave to the mixer 005. A part of the transmission wave generated by the oscillator 001 is also input to the mixer 005 via the distributor 002.

  The mixer 005 mixes the reception wave input to the reception antenna 004 and the transmission wave from the distributor 002, and generates a beat signal having a frequency difference between the two. The beat signal is a signal having a frequency (beat frequency) determined by the relative distance and relative speed of the reflecting object. A Fourier transform unit 006 performs a Fourier transform on this beat signal. The amplitude spectrum obtained by taking the amplitude of the signal after Fourier transform has a peak at the beat frequency.

  Here, the beat signal will be described using mathematical expressions. Note that the transmission antenna 003 transmits a transmission wave having a transmission frequency f (t) expressed by the following equation (1).

  At this time, the angular frequency of the transmission wave is expressed by the following equation (2).

  The phase of the transmission wave is expressed by the following equation (3).

Here, C is an integral constant, which is a term representing the initial phase of the transmission wave. The transmission wave s _T (t) is expressed by the following equation (4).

Assuming that the target relative distance is r and the speed of light is c, the received wave s _R (t) is proportional to the transmission wave s _T (t) delayed by the time 2r / c. Therefore, the received wave s _R (t) is expressed by the following equation (5).

Where γ is the target complex reflectance multiplied by the distance attenuation factor. The mixer 005 mixes the transmission wave s _T (t) with the reception wave s _R (t) to obtain a reception signal represented by the following equation (6).

When the phase of the exponent part on the right side is set as Φ _m (t), the phase rotation number of the received signal is expressed by the following equation (7).

  Further, it is assumed that the distance of the target moving at the relative speed v is expressed by the following equation (8).

  However, relative speed is positive for approach. Here, when Expression (8) is substituted into Expression (7), the following Expression (9) is obtained.

Now, let t _{0, l be the} time at which the l-th frequency sweep starts. In each frequency sweep, it is assumed that the sweep start transmission frequency is α _l . At this time, the transmission frequency f _l (t) in the l-th frequency sweep is expressed by the following equation (10).

In each frequency sweep, and it performs a sample of a particular range gate after t _s the sweep start. Substituting _{t = t 0, l + t} s and α = α _l -βt _{0, l} in the equation (9), the following equation (11) is obtained.

Of the right-hand side of equation (11), the coefficient of the term of t _s is representative of the frequency of the beat signal. The constant term is the initial phase divided by 2π. When the initial phase is Φ _{m0, l} , the following equations (12) and (13) are established.

The first term of equation (13) is a term representing the difference in sweep start time. The second term represents the change in the initial phase depending on the sweep start transmission frequency. The start time of the first sweep is regarded as the reference time, and t _0,1 = 0. When Δα ₁ = α ₁ −α ₁ , the phase based on the initial phase of the first sweep is expressed by the following equation (14).

  Here, it is assumed that the absolute value of the second term of Expression (14) is sufficiently small. That is, it is assumed that the following formula (15) holds.

  When this is modified, the following equation (16) is obtained.

  When the condition of Expression (16) is satisfied, the above Expression (14) becomes as follows.

  Therefore, if the phase calculated from the equation (17) is compensated for the signal detected at each sweep, the phase of the signal detected at each sweep is aligned, so that coherent integration is possible. However, in order to calculate the phase of Expression (17), the target relative speed v needs to be known.

  The power calculation unit 007 obtains the power spectrum of the beat signal by calculating the power of the Fourier transform of the beat signal obtained by the Fourier transform unit 006. The first detection unit 008 performs peak detection processing on the power spectrum. The detection process here is performed as a provisional detection process, and as described later, the detection process is performed again at a later stage of the signal processing. The first detection unit 008 considers that a signal is detected when the power value exceeds a preset threshold value among the peaks existing in the power spectrum, and the beat frequency value (peak frequency) at which the peak exists. ).

  Note that the peak detection process in the first detection unit 008 is a detection process for a signal before the integration between sweeps. Therefore, there is a possibility that the SN ratio of the signal to be detected is not sufficiently high. Therefore, in the peak detection process of the first detection unit 008, a low threshold value is used so that a signal with a low SN ratio can be detected. As a result, the false alarm probability increases, but such a false alarm is removed by the detection process in the subsequent stage. The peak frequency extracted by the detection process is input to the first detection signal storage unit 009.

  The first detection signal storage unit 009 also inputs a beat signal Fourier transform. The first detection signal accumulation unit 009 extracts a component (complex amplitude value) corresponding to the peak frequency input from the first detection unit 008 in the beat signal Fourier transform. In the first detection and ranging unit 010, the extracted complex amplitude value is combined with the peak frequency value and stored as a first detection signal.

  The first detection signal is accumulated by observation with a plurality of up-chirps and observation with a plurality of down-chirps.

  By combining the peak frequency obtained by up-chirp observation and the peak frequency obtained by down-chirp observation, the relative distance and relative speed of the target reflecting object are calculated. As this calculation method, a conventionally known method may be used.

  Note that the first detection signal is obtained by a plurality of sweeps. Therefore, it is conceivable to perform ranging and speed measurement processing using only the peak frequency first detected in up-chirp observations more than a predetermined number of times and the peak frequency first detected in down-chirp observations more than a predetermined number of times. . Such processing has an effect of reducing false alarms caused by setting the threshold value of the first detection unit 008 low. Alternatively, it is possible to integrate the results detected at the same peak frequency for each up-chirp observation or down-chirp observation. In this case, since the phase of the first detection signal varies for each sweep, coherent integration processing is impossible at this time. Therefore, amplitude or power integration, that is, incoherent integration is performed, and only when the power after integration is equal to or greater than a set threshold value, it is used for the distance measurement speed measurement processing.

  The phase compensation amount calculation unit 011 receives the relative speed from the first detection distance measurement speed measurement unit 010 and calculates the phase compensation amount using Expression (17). The phase compensation unit 012 receives the first detection signal stored in the first detection signal storage unit 009 and performs phase compensation using the phase compensation amount calculated by the phase compensation amount calculation unit 011. The inter-sweep integrating unit 013 coherently integrates the first detection signal after phase compensation. The second detection unit 014 inputs a signal after integration between sweeps and performs detection processing. Specifically, it is determined that a signal has been detected when the power of the input signal exceeds a preset threshold value. Since the signal input to the second detection unit 014 is a signal after integration between sweeps, it can be considered that the SN ratio is sufficiently obtained. Therefore, the threshold value used in the second detection unit 014 may be set so that the false alarm probability is sufficiently small.

  Although the present invention is particularly effective for a radar that performs frequency modulation, such as FMCW radar and FMICW radar, Equation (17) holds true for an ordinary pulse radar that performs only pulse modulation. It is possible to apply the coherent integration process.

  As described above, according to the present embodiment, a wave is radiated into space, a wave reflected and scattered by an object existing outside is received, and the object is measured by performing signal processing on the received wave. A radar apparatus that performs a transmission antenna that radiates a wave in space, a reception antenna that inputs a wave reflected and scattered by an object from space, and generates a reception signal by detecting the reception wave input from the reception antenna A reception unit, a Fourier transform unit that calculates a received signal Fourier transform by taking out a received signal in a predetermined time range and performing a Fourier transform on the received signal, and a received signal Fourier transform calculated in a plurality of time ranges And an integration processing unit that performs integration for each same frequency, so that the detection process is repeated in a short cycle at a short distance where the S / N ratio of the received signal is sufficiently high. Even in the far SN ratio of the signal is not sufficiently high, by performing the integration processing in a long time range, it is possible to improve the target detection performance of both near and far.

Embodiment 2. FIG.
In the first embodiment described above, coherent integration is performed by compensating for the phase shift proportional to the target relative speed and the sweep start time difference. In this case, it is necessary to perform provisional detection (first detection) in order to calculate the target relative speed. Next, an embodiment in which phase correction is performed without performing the first detection process will be described.

  FIG. 2 is a block diagram showing the configuration of the radar apparatus according to the second embodiment. In FIG. 2, 015 is a Fourier transform storage unit, 016 is an inter-sweep Fourier transform unit, and 017 is a detection unit. In addition, about the structure same as FIG. 1, the same code | symbol is attached | subjected and shown, The description is abbreviate | omitted here.

  Next, the operation of the radar apparatus according to the second embodiment will be described. The operations from the generation of the transmission wave by the oscillator 001 to the Fourier transform of the beat signal by the Fourier transform unit 006 are the same as those in the first embodiment. The Fourier transform accumulating unit 015 accumulates the beat signal Fourier transform calculated by the Fourier transform unit 006 for a predetermined number of sweeps. The inter-sweep Fourier transform unit 016 performs a Fourier transform in the sweep direction on the beat signal Fourier transform. The Fourier transform in the sweep direction is as follows. In the beat signal Fourier transform of up-chirp observation, signals with the same beat frequency are extracted and subjected to Fourier transform on the signal sequence arranged in the sweep order. Here, the axis of the signal sequence after the Fourier transform is temporarily called a sweep direction frequency. This process is performed at all beat frequencies. The signal obtained after processing is defined in two dimensions, the beat frequency axis and the sweep direction frequency axis.

  Note that performing Fourier transform on a signal of a plurality of sweeps means performing coherent integration assuming various relative velocities v and obtaining an integration result with a high SN ratio at any relative speed.

  In the detection unit 017, a signal after integration between sweeps is input and detection processing is performed. Specifically, it is determined that a signal has been detected when the power of the input signal exceeds a preset threshold value. Since the signal input to the detection unit 017 is a signal after integration between sweeps, it can be considered that the SN ratio is sufficiently obtained. Therefore, the threshold value used in the detection unit 017 may be set so that the false alarm probability is sufficiently small.

  What is output as the detection result is the beat frequency at which the peak is detected.

  According to the second embodiment, since integration between sweeps can be performed without performing the first detection process, it is possible to improve the long-range detection performance with a simple signal processing configuration.

Embodiment 3 FIG.
The above embodiment is an embodiment in which the fluctuation between sweeps of the transmission frequency at the start of sweeping can be ignored. Next, an embodiment will be described in which the phase shift due to this influence is compensated when the fluctuation between sweeps of the transmission frequency at the start of sweep cannot be ignored. FIG. 4 schematically shows how the sweep start transmission frequency varies. Compared with sweep 1, in sweep l, the transmission frequency at the start of the sweep is shifted by Δα _l .

  FIG. 3 is a block diagram showing the configuration of the radar apparatus according to the third embodiment. In FIG. 3, reference numeral 018 denotes a sweep start transmission frequency estimation unit. In addition, about the structure same as FIG. 1, the same code | symbol is attached | subjected and shown, The description is abbreviate | omitted here.

  Next, the operation of the radar apparatus according to the third embodiment will be described. The operation from the generation of the transmission wave by the oscillator 001 to the accumulation of the first detected signal by the first detection signal accumulation unit 009 and the distance measurement and speed measurement by the first detection distance measurement and speed measurement unit 010 is as follows. This is the same as in the first embodiment. The sweep start transmission frequency estimation unit 018 estimates the fluctuation amount of the sweep start transmission frequency by the following method.

  It is assumed that the high S / N ratio target 1 and the high S / N ratio target 2 are detected in the signals accumulated in the first detection signal accumulation unit 009. For these two high S / N ratio targets, Equation (14) is expressed as the following Equations (14-1) and (14-2), respectively. In these equations, the subscript 0 representing the initial phase is omitted.

Here, r ₁ and r ₂ are the distances of the respective high S / N ratio targets, and v ₁ and v ₂ are the speeds of the respective high S / N ratio targets. When this equation (14) is expressed by a matrix and a vector, the following equation is obtained.

By solving the simultaneous linear equations, v ₁ , v ₂ , Δα ₂ , Δα ₃ , Δα ₃ can be obtained. The reason why the speed is unknown is that the observation time of the signal used for integration between sweeps is longer than when the integration between sweeps is not performed, and therefore the phase correction term proportional to the observation time t ₁ (formula (14-1 ) And the accuracy of the coefficient of the first term on the right side of equation (14-2) are necessary for coherent integration.

Δα _l obtained as described above is calculated from the high S / N ratio target. However, these values represent the characteristics of the radar apparatus hardware and do not depend on the target. Therefore, using these Δα _l enables phase compensation for other targets. That is, in the phase compensation amount calculation unit 011, the phase of the second term on the right side of Expression (14) is calculated based on Δα _l calculated by the sweep start transmission frequency estimation unit 018 and the distance estimated by the first detection distance measurement speed measurement unit 010. The amount can be calculated. As for the phase term of the first term on the right side of Equation (14), the phase compensation amount can be calculated using the speed obtained by the first detection distance measuring speed measuring unit 010 as in the first embodiment. .

  The phase compensation unit 012 performs phase compensation on the signal of the first detection signal accumulation unit 009 using the phase compensation amount calculated by the phase compensation amount calculation unit 011. Subsequent processing, that is, processing by the inter-sweep integrating unit 013 and the second detecting unit 014, is the same operation as in the first embodiment.

In the above has been described a method for calculating a [Delta] [alpha] _l from the two high SN ratio target, when a high SN ratio target there are more than two, three or more [Delta] [alpha] _l from the received signal with a high SN ratio target It may be calculated. As one method, there is a method of setting a plurality of combinations of two high S / N ratio targets and averaging Δα _l calculated by each combination to obtain a final estimation result. Alternatively, there is also a method of calculating Δα _l by the least square method by combining the relationships of Expression (14) obtained for three or more high S / N ratio targets. In any case, since the number of reception signals used for estimation increases, the estimation accuracy of Δα _l can be improved.

  As described above, according to the third embodiment, even when the stability of the radar device is not sufficiently high and the fluctuation between sweeps of the transmission frequency at the start of sweep cannot be ignored, the detection performance is improved by the coherent integration between sweeps. Can be realized.

Embodiment 4 FIG.
The above-described third embodiment is an embodiment in which the phase shift due to this influence is compensated when the fluctuation between sweeps of the transmission frequency at the start of sweep cannot be ignored. Similarly, another embodiment for compensating for the phase shift due to the fluctuation between sweeps of the transmission frequency at the start of sweep will be described below.

  FIG. 5 is a block diagram showing the configuration of the radar apparatus according to the fourth embodiment. Since the reference numerals in this figure are all the same as those described above, detailed description thereof is omitted here. However, the difference in configuration between FIG. 3 and FIG. 5 is that, in FIG. 5, an inter-sweep Fourier transform unit 016 is provided instead of the inter-sweep integration unit 013 of FIG.

  Next, the operation of the radar apparatus according to the fourth embodiment will be described. After the transmission wave is generated by the oscillator 001, the first detection signal accumulation unit 009 accumulates the first detected signal, the first detection distance measurement / velocity measurement unit 010 performs distance measurement and velocity measurement, and starts sweeping. The operation until the transmission frequency estimation unit 018 calculates the fluctuation amount of the sweep start transmission frequency is the same as that in the third embodiment. Also, the phase compensation amount calculation unit 011 calculates the phase amount of the second term on the right side of the above equation (14) as in the third embodiment. However, the phase amount of the first term on the right side of Equation (14) is not particularly calculated, and the phase compensation of the phase compensation unit 012 is also performed only on the second term of the right side of Equation (14).

  The signal after phase compensation by the phase compensation unit 012 is subjected to Fourier transform processing between sweeps by the Fourier transform unit 016 between sweeps. This process is substantially the same as the operation of the inter-sweep Fourier transform unit 016 in the second embodiment. However, in the second embodiment, the inter-sweep Fourier transform process is performed for all beat frequency components. However, in the present embodiment, the first detection process is performed by the first detection unit 008. The inter-sweep Fourier transform process is performed only on the beat frequency component extracted by the detection process. The second detection unit 014 performs detection processing on a signal defined in two dimensions of the beat frequency axis and the sweep direction frequency axis.

  As described above, according to the fourth embodiment, similarly to the above-described third embodiment, the stability of the radar apparatus is not sufficiently high, and the fluctuation between sweeps of the transmission frequency at the start of sweep cannot be ignored. The detection performance can be improved by coherent integration between sweeps.

Embodiment 5 FIG.
The above-described third and fourth embodiments are embodiments in which the phase shift due to this influence is compensated when the fluctuation between sweeps of the transmission frequency at the start of sweep cannot be ignored. Specifically, the amount of fluctuation between sweeps of the transmission frequency at the start of the sweep is calculated, and the phase compensation amount is estimated. In the estimation, the result calculated by the first detection ranging / velocity measuring unit 010 is used as the high SN ratio target distance. In the fifth embodiment, an example in which the high SN ratio target distance is estimated together with the fluctuation amount between sweeps of the transmission frequency at the start of sweep without using the processing result of the first detection ranging / velocity measuring unit 010. Show.

  FIG. 6 is a block diagram showing the configuration of the radar apparatus according to the fifth embodiment. The symbols in FIG. 6 are all the same as those described above. 6 has almost the same configuration as FIG. 5, except that the output of the first detection ranging / velocity measuring unit 010 is not input to the sweep start transmission frequency estimating unit 018 in FIG. Is different.

  Next, the operation of the radar apparatus according to the fifth embodiment will be described. Assume that three high S / N ratio targets are detected. For these three high S / N ratio targets, equation (14) is expressed as follows.

In these equations, there are nine unknowns v1, v2, v3, r1, r2, r3, Δα ₂ , Δα ₃ , Δα ₃ . On the other hand, there are a total of nine observation values, ΔΦ _{1, l} , ΔΦ _{2, l} , ΔΦ _{3, l} (l = 1, 2, 3). Since the number of unknowns is equal to the number of observations, Δα _l can be estimated by solving the simultaneous equations.

If the high SN ratio target number is N, the unknown number is 2N + 3 and the number of observed values is 3N. If N is 3 or more, the number of observed values exceeds the unknown number, so that the unknown number can be estimated. The simultaneous equations here are non-linear equations because they include the product of distance and Δα _l . Therefore, the unknown is estimated by a nonlinear optimization technique. As the nonlinear optimization method, a generally known method may be used. The processing of other parts is the same as that of the fourth embodiment.

  In the present embodiment, the operation of the sweep start transmission frequency estimation unit 018 of the fourth embodiment is changed. However, in the configuration of the third embodiment, the sweep start transmission frequency estimation unit 018 is replaced with the present embodiment. It can also be set as the structure replaced with a thing.

  As described above, according to the fifth embodiment, as in the third embodiment, the stability of the radar apparatus is not sufficiently high, and the fluctuation between sweeps of the transmission frequency at the start of sweep cannot be ignored. The detection performance can be improved by coherent integration between sweeps.

It is a block diagram showing the structure of the radar apparatus which concerns on Embodiment 1 of this invention. It is a block diagram showing the structure of the radar apparatus which concerns on Embodiment 2 of this invention. It is a block diagram showing the structure of the radar apparatus which concerns on Embodiment 3 of this invention. It is a figure explaining the fluctuation | variation of the sweep start transmission frequency. It is a block diagram showing the structure of the radar apparatus based on Embodiment 4 of this invention. It is a block diagram showing the structure of the radar apparatus based on Embodiment 5 of this invention.

Explanation of symbols

  001 oscillator, 002 distributor, 003 transmission antenna, 004 reception antenna, 005 mixer, 006 Fourier transform unit, 007 power calculation unit, 008 first detection unit, 009 first detection signal storage unit, 010 first detection distance measurement speed Unit, 011 phase compensation amount calculation unit, 012 phase compensation unit, 013 integration unit between sweeps, 014 second detection unit, 015 Fourier transform accumulation unit, 016 Fourier transform unit between sweeps, 017 detection unit, 018 sweep start transmission frequency estimation unit .

Claims (6)

A radar device that radiates a wave in space, receives a wave reflected and scattered by an object existing in the space, and measures the object by performing signal processing on the received wave,
A transmitting antenna that radiates the wave in space;
A receiving antenna for inputting the wave reflected and scattered by the object from space;
A reception unit that generates a reception signal by detecting a reception wave input from the reception antenna;
A Fourier transform unit that calculates a received signal Fourier transform by taking out a received signal in a predetermined time range and applying a Fourier transform to the received signal;
An integration processing unit that performs integration for each same frequency with respect to the received signal Fourier transform calculated in a plurality of time ranges, and
The wave radiated to the space from the transmitting antenna is linearly frequency-modulated within a certain time interval, and the Fourier transform unit extracts the received signal to be subjected to Fourier transform. The range is approximately equal to the time interval of frequency modulation,
A radar apparatus , wherein the integration processing unit integrates a received signal Fourier transform after correcting a phase of an amount proportional to a target relative speed and a frequency modulation start time difference . A radar device that radiates a wave in space, receives a wave reflected and scattered by an object existing in the space, and measures the object by performing signal processing on the received wave,
A transmitting antenna that radiates the wave in space;
A receiving antenna for inputting the wave reflected and scattered by the object from space;
A reception unit that generates a reception signal by detecting a reception wave input from the reception antenna;
A Fourier transform unit that calculates a received signal Fourier transform by taking out a received signal in a predetermined time range and applying a Fourier transform to the received signal;
An integration processing unit that performs integration for each same frequency with respect to the received signal Fourier transform calculated in a plurality of time ranges, and
The wave radiated to the space from the transmitting antenna is linearly frequency-modulated within a certain time interval, and the Fourier transform unit extracts the received signal to be subjected to Fourier transform. The range is approximately equal to the time interval of frequency modulation,
A radar apparatus , wherein the integration processing unit integrates a received signal Fourier transform after correcting an amount of phase proportional to a target relative distance and a change amount of a transmission frequency at the start of frequency modulation . The integration processing section, as the integration, the radar apparatus according to claim 1, wherein the adding process while leaving the phase of the signal. The integration processing section, as the integration, the radar apparatus according to claim 1, wherein the adding processing the amplitude or power of the signal. The frequency modulation is performed in two types of sections, a section where the transmission frequency increases linearly with time and a section where the transmission frequency decreases linearly with time.
A frequency modulation speed calculation unit that calculates a relative speed of the object by combining output signals of the Fourier transform unit in each section;
The radar apparatus according to claim 1, wherein the calculating the amount of phase correction using the relative speed of the target calculated by the frequency modulation rate calculating section. The frequency modulation is performed in two types of sections, a section where the transmission frequency increases linearly with time and a section where the transmission frequency decreases linearly with time.
A frequency modulation distance calculation unit that calculates a relative distance of the object by combining output signals of the Fourier transform unit in each section;
The radar apparatus according to claim 2, wherein the phase correction amount is calculated using the relative distance calculated by the frequency modulation distance calculation unit.

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