DE102007049998A1 - Radar device for e.g. detecting externally existing target, has integration circuit integrating Fourier transformed received signals, which are computed in several time intervals, in each of same frequencies - Google Patents

Abstract

The device has a transmitting antenna (3) radiating waves in an area, and a receiving antenna (4), which receives the waves, which are reflected and scattered by an object, from the area. A receiving circuit (5) measures the receiving waves taken up by the antenna to produces a received signal. A Fourier transformation circuit (6) extracts the received signal within a given time interval and computes Fourier transformed received signals. An integration circuit (13) integrates the Fourier transformed received signals, which are computed in several time intervals, in each of same frequencies.

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

The The present invention relates to a radar apparatus, and in particular to a radar device which is an externally existing Destination and receives information related to the recorded destination.

2. Description of the state of the technique

in the Generally, the radar apparatus radiates electromagnetic waves into a room, receives one reflected signal reflected by a target (object), and subject the received signal to signal processing to get information related to the destination.

In the case of measuring a distance between the radar and the target becomes a transmitted wave frequently subjected to modulation to obtain target distance information. For example, a radar system is known in which case a frequency modulated continuous wave radar (FMCW) system or a Frequency Modulated Intermittent Continuous Wave Radar (FMCW) system the transmitted wave is subjected to a frequency modulation, the causes the transmit frequency to change linearly with time thus a distance to the target and a relative speed (for example M.I. Skolnik, "Introduction to Radar Systems", third edition, Pages 195 to 197, McGraw-Hill, 2001).

at The FMCW radar gives way to a receiver wave reflected from the target in the frequency modulation pattern by a propagation delay amount the electric wave between the radar and the target. and goes off, from the transmitted wave. As a result the transmitted wave and the receiver wave mixed together to form a receiver signal (beat signal) with a frequency (beat frequency) to get the difference between the transmitted wave and the receiver wave. Because the beat frequency according to the distance is intended to the target, if a frequency analysis in the Beating signal performed is used to calculate the beat frequency, the distance to that Goal to be obtained. Indeed that depends Beating signal from both the distance and a speed (Doppler speed) along the line of sight of the target. Accordingly, a Observation caused by frequency modulation (up-modulated modulation), which allows that the deferring frequency increases with time, and an observation obtained by frequency modulation (down-modulo modulation), which allows that the transmission frequency decreases with time, is performed performed. Then those by the respective observations obtained beating frequencies combined, whereby allows is calculated that the distance to the target and the Doppler frequency become.

When a frequency analysis method for the beat signal becomes frequent uses a Fourier transform. The Fourier transformation has a function of calculating the beat frequency as well as a Effect of improving a signal-to-noise ratio (S / N ratio) with Help more coherent Integration. If an N point in the time sequence of the beat signal is sampled and a discrete N-point Fourier transform is performed, takes the S / N ratio over N times to.

SUMMARY OF THE INVENTION

at the radar, which is a distance measurement by the aid of a frequency modulation like an FMCW radar or an FMICW radar, is a duration of a signal that corresponds to a frequency analysis process, d. h., is subjected to a Fourier transform, essentially equal to a duration of a frequency modulation, for example one Duration until the transmission frequency from a lowest value to a highest value when the frequency modulation is up-shift modulation.

It There occurs a problem such that, even if a unit of time frequency modulation for holding an S / N ratio, that is sufficient to a shorter one Watching distance is set, the sufficient S / N ratio is not at a greater distance can be obtained, and therefore there is a possibility that the acquisition capacity, the is defined by a probability of detection or a False alarm probability, can not be satisfied.

On the other hand, when the unit time of the frequency modulation is based on the larger one Distance is set, the frequency modulation performed at the shorter distance in the excessive period of time. For example, in the case of a radar monitoring an obstacle, it is desired that the obstacle at the shorter distance be measured by a high time resolution, but if priority is given to the detection capability at the larger distance, such a problem occurs the time resolution at the shorter distance can not be sufficiently ensured.

The The present invention has been made to solve the aforementioned problems to solve, and it is therefore an object of the present invention to provide a radar apparatus which is capable of both the target acquisition capacity at the shorter Distance as well as the longer Improve distance.

The The present invention relates to a radar apparatus which Waves radiating into a room, the waves passing through an inside reflected and scattered object existing space receives and The received waves undergo a signal processing to the Object to measure which contains radar device: a transmitting antenna, the the waves radiate into the room; a receiving antenna that the Waves reflected and scattered by the object takes up the room; a receiving circuit, that of the receiving antenna recorded received waves to a received signal to create; a Fourier transform circuit that received the Receives signal within a given time range, and the received signal of the Fourier transform undergoes a Fourier transform the received signal; and an integrator circuit that performs the Fourier transforms of the received signals calculated in several time domains, integrated in each of the same frequencies.

According to the present Invention, the radar device is provided, the waves in one Space radiates, the waves that exist through an existing in the space Object reflected and scattered, receives and the received waves the signal processing to measure the object which Radar device contains: the transmitting antenna, which radiates the waves into space; the receiving antenna, the waves that were reflected and scattered by the object from the room; the receiving circuit, that of the receiving antenna recorded received waves to a received signal to create; the Fourier transform circuit that received the Receives signal within a given time range and the received signal is Fourier transformed to calculate the Fourier transform of the received signal; and the integration circuit, which comprises the Fourier transforms of the received signal, which have been calculated in several time ranges, in each of them Integrated frequencies. Through the above configuration is the acquisition process in a shorter Period in a shorter one Distance which is sufficient in the S / N ratio of the received signal is higher, and the integration process can even at a greater distance in a longer time range carried out that will be insufficient higher in the S / N ratio of the received signal. Ale a consequence it is possible that Target detection performance both at the shorter one Distance as well as the longer one Improve distance.

BRIEF DESCRIPTION OF THE DRAWINGS

1 Fig. 10 is a block diagram illustrating a configuration of a radar apparatus according to a first embodiment of the present invention;

2 Fig. 10 is a block diagram illustrating a configuration of a radar apparatus according to a second embodiment of the present invention;

3 Fig. 10 is a block diagram illustrating a configuration of a radar apparatus according to a third embodiment of the present invention;

4 Fig. 12 is a diagram for explaining a variation of a wobble start frequency;

5 FIG. 10 is a block diagram illustrating a configuration of a radar apparatus according to a fourth embodiment of the present invention; FIG. and

6 FIG. 10 is a block diagram illustrating a configuration of a radar apparatus according to a fifth embodiment of the present invention. FIG.

DETAILED DESCRIPTION THE PREFERRED EMBODIMENTS

It A description will now be given of preferred embodiments of the present invention Invention given with reference to the accompanying drawings.

First embodiment

1 FIG. 10 is a block diagram illustrating the configuration of a radar apparatus according to a first embodiment of the present invention. FIG. In 1 denotes the reference number 001 an oscillator that generates transmitted waves, the reference number 002 denotes a distributor that shares the transmitted waves, the reference number 003 denotes a transmitting antenna that radiates the transmitted waves into a room, the reference numeral 004 denotes a receiving antenna that receives the received waves from the room, and the reference numeral 005 denotes a mixer which mixes the transmitted waves and the received waves to produce a beat signal. The reference number 006 denotes a Fourier transform circuit that applies a beat signal of the Fourier transform, the reference number 007 denotes an energy calculating circuit that calculates an energy of the Fourier-transformed beat signal to obtain an energy spectrum, the reference numeral 008 denotes a first detection circuit that detects a spectrum peak from the energy spectrum, the reference number 009 denotes a first detection signal accumulation circuit which receives the signals received from the first detection circuit 008 were recorded, accumulated, and the reference number 010 denotes a first detection distance and speed measuring circuit having a distance and a speed in accordance with the signals included in the first detection signal storage circuit 009 are stored. The reference number 011 denotes a phase compensation amount calculating circuit which calculates a compensation amount of the phase shift between deflections, the reference number 012 denotes a phase compensation circuit which detects the phases of the signals in the first detection signal storage circuit 009 are accumulated according to the phase compensation amount calculating circuit 011 corrected calculated phase compensation amount, the reference number 013 denotes an inter-sample integration circuit which performs coherent integration between the samples and the reference numeral 014 denotes a second detecting circuit which performs a detecting operation on the signals subjected to the inter-sampling integration. The mixer 005 forms a receiving circuit.

following the operation of the radar device according to the first embodiment of the present invention.

The oscillator 001 generates the transmitted waves. In the case of the FMCW system or the FMICW system, an oscillation frequency under the control is changed linearly with time. The transmitted waves are transmitted to the transmitting antenna 003 over the distributor 002 entered. The transmitting antenna 003 emits the transmitted wave into the room. The emitted transmitted waves are reflected by an object (target) existing in the space. The object by which the transmitted waves are reflected is hereinafter referred to as "reflection object". The receiving antenna 004 receives the reflected waves from the reflection object out of the space and outputs the reflected waves as received waves to the mixer 005 one. Part of the waves sent by the oscillator 001 are generated via the distributor 002 in the mixer 005 entered.

The mixer 005 mixes the received waves into the receiving antenna 004 entered, and the transmitted waves from the distributor 002 with each other to generate a beat signal having a frequency with the difference between these waves. The beat signal is a signal having a frequency (beat frequency) determined according to a relative distance and a relative speed with respect to the reflection object. The Fourier transform circuit 006 subjects the beat signal to the Fourier transform. An amplitude spectrum obtained from the amplitude of the signal subjected to the Fourier transform has a peak at the beat frequency.

Next, the beat signal will be described by expressions. The transmitting antenna 003 sends the transmitted waves at a transmission frequency f (t) represented by the following expression (1). f (t) = α + βt (1)

In this situation, an angular frequency of the transmitted wave is represented by the following expression (2). ω (t) = 2π (α + βt) (2)

Also becomes the phase of the transmitted waves by the following expression (3).

In this example, C is an integration constant, which is a term representative of the initial phase of the transmitted wave. A transmitted wave s _T (t) is represented by the following expression (4).

Assuming that the relative distance to the target is r and the speed of light is c, the received wave s _R (t) is delayed relative to the transmitted wave s _T (t) by a time 2r / c. Accordingly, the received wave s _R (t) is represented by the following expression (5).

In this example, γ is obtained by multiplying a distance attenuation rate by a complex reflection rate of the target. The mixer 005 the transmitted wave s _T (t) mixes with the received wave s _R (t) to obtain the received wave represented by the following expression (6).

When Φ _m (t) is substituted for the phase of the right-side exponential, the phase rotation number of the received signal is represented by the following expression (7).

Also, the distance to the target moving at a relative velocity v is represented by the following expression (8). r = r 0 - vt (8)

In in this case the relative velocity is positive in the case where the target is approaching. If the expression (8) is put into the expression (7), the following becomes Expression (9).

It is now assumed that a time at which an I-th frequency sweep starts is t _{0, 1} . It is assumed that the sampling start transmission frequency in the respective frequency samples is equal to α _l . In this situation, the transmission frequency f _l (t) at the l-th frequency scanning becomes the following Off pressure (10) shown. f l (t) = α l + β (t - t 0 ) = (α l - βt 0, L ) + βt (10)

It is assumed that a gate of a certain range is sampled at the respective frequency samples when the time t _{s has} elapsed since the sampling was started. When t = t _{0, l} + t _s and α = α ₁ -βt _{0, l are} substituted into the expression (9), the following expression (11) is obtained.

The coefficient of expression for t _s on the right side of expression (11) represents the frequency of the beat signal. Also, the constant expression is obtained by dividing the initial phase by 2π. Assuming that the initial phase is equal to Φ _{m0, l} , the following expressions (12) and (13) are satisfied.

The first term of the expression (13) is a term representing a difference in the sampling start time. The second term represents a change in the initial phase due to the sample start frequency. It is assumed that the start time of the first sample is a reference time and that t _{0, l} = 0. Assuming that Δα _l = α _l - α ₁ , the phase based on the initial phase of the first scan is represented by the following expression (14).

In In this example, it is assumed that the absolute value of the second Term of the expression (14) is sufficiently small. That is, it will the following expression (15) is sufficient.

Of the Expression (15) is modified into the following expression (16).

If the condition of expression (15) is satisfied, the above Expression (14) is shown as follows.

Accordingly, if the phase calculated from the expression (17) is compensated with respect to the signal detected in each of the samples, the phases of the signals detected in the respective samples are matched. As a result, the coherent integration is enabled. However, in the calculation of the phase in Expression (17), it is necessary to set the relative velocity v of To know the target.

The energy calculation circuit 007 calculates the energy of the Fourier transform of the beat signal generated by the Fourier transform circuit 006 was obtained to thereby obtain the energy spectrum of the beat signal. The first detection circuit 008 performs the peak detection process on the energy spectrum. This detecting operation is performed as a preliminary detecting operation, and another detecting operation is again performed in a post-stage of the signal processing, as will be described later. The first detection circuit 008 takes into account that the signal was detected in the case where an electric energy value exceeds a predetermined threshold among the peaks existing in the energy spectrum, and extracts a value (peak frequency) of the beat frequency in which this peak exists.

The peak detection process in the first detection circuit 008 is a process of detecting the signal that has not yet undergone inter-sampling integration. For this reason, there is a possibility that the S / N ratio of the signal to be detected is insufficiently high. Accordingly, in the peak detection operation of the first detection circuit 008 a lower threshold is used to detect even the signal having a low S / N ratio. As a result, the probability of a false alarm is increased, but such a false alarm is eliminated by the post-step detection process. The peak frequency extracted by the detection process is put into the first detection signal accumulation circuit 009 entered.

The first detection signal accumulation circuit 009 also picks up the Fourier transform of the beat signal. The first detection signal accumulation circuit 009 draws components (complex amplitude value) corresponding to the peak frequency generated by the first detection circuit 008 from the Fourier transform of the beat signal. The first detection distance and speed measuring circuit 010 accumulates the extracted complex amplitude value combined with the peak frequency value as a first detection signal.

The first detection signals are due to multiple observations an upwards chirp and several observations accumulated due to a downslope.

The through the up-gauge monitoring received peak frequency and that obtained by the Abwärtschirpbeobachtung Peak frequency are combined to give the relative Distance and the relative speed of the reflection object, which is a goal to calculate. The known method can as the calculation method will be used.

The first detection signal is obtained by several samples. Therefore, it is suggested that the distance and speed measurement process carried out is recorded using only the peak frequency first will be in at least a predetermined number of up-chop measurements and the peak frequency that is detected first in at least one predetermined number of Abwärtschirpmessungen.

This action has the effect of reducing the false alarm caused by a lower setting of the threshold value of the first detection circuit 008 , Alternatively, it is proposed to integrate the results acquired by the same peak frequency in each of the up-gauge or down-ward observations. In this case, since the phase of the first detection signal is varied in each of the samples, the coherent integration process can not be performed at that time. Under these circumstances, the integration of the amplitude or the electric power, that is, the incoherent integration is performed, and only in the case where the integrated electric power is equal to or higher than the set threshold, the integration in the distance and Speed measurement used.

The phase compensation amount calculating circuit 011 takes the relative speed from the first detection distance and speed measurement circuit 010 and calculates the phase compensation amount using Expression (17). The phase compensation circuit 012 receives the first detection signal that is in the first detection signal accumulation circuit 009 has been accumulated, and performs the phase compensation using the phase compensation amount obtained from the phase compensation amount calculating circuit 011 was calculated by. The inter-sample integration circuit 013 Coherently integrates the first detection signal that has been compensated in phase. The second detection circuit 014 takes the signal that has been subjected to the inter-sampling integration and performs the acquisition process. More specifically, in the case where the electrical energy of the input signal exceeds a predetermined threshold, the second detection circuit determines 014 that the signal was detected. Because the signal is in the second detection circuit 014 is inputted, is a signal that has been subjected to the inter-sampling integration, it can be considered that the S / N ratio has been sufficiently obtained. For this reason, the threshold used in the second detection circuit 014 is set so that the probability of a false alarm is sufficiently small.

The The present invention is sufficiently effective in a radar that performs the frequency modulation, like the FMCW radar or the FMICW radar, but since the expression (17) in the normal pulse radar, which performs only the pulse modulation is sufficient Is it possible, the same coherent one Apply integration process.

As described above is according to this embodiment provided the radar device that emits waves in a room, the waves that keep going through a existing object were reflected and scattered, receives and the received waves undergo a signal processing to the object to measure which radar device contains: the transmitting antenna that the Waves in the room radiates, the receiving antenna, the of receiving reflected and scattered waves from the space; the receiving circuit receiving the input from the receiving antenna, detected waves to generate a received signal; the Fourier transform circuit which receives the received signal within a given time range and the received signal the Fourier transform undergoes the Fourier transform to calculate the received signal; and the integration process circuit, the Fourier transforms of the received signal, which in multiple time ranges, in each of the same frequencies integrated. With the above configuration, the detection process becomes in a shorter time Period in a shorter one Repeat distance sufficiently higher in the S / N ratio of received signal and the integration process is in one longer Time range even with a longer one Distance that is sufficiently higher in the S / N ratio of the received signal is performed. As a result, it is possible, the target acquisition capacity both at the shorter distance as well as the longer one Improve distance.

Second embodiment

at the above-described first embodiment The phase shift is proportional to the relative velocity of the target and the sampling start time difference is compensated to the coherent To perform integration. In this case, it is necessary to perform the preliminary detection (first detection) calculate the relative speed of the target. following becomes an embodiment described in which the phase without performing the first detection process is corrected.

2 FIG. 10 is a block diagram illustrating the configuration of a radar apparatus according to a second embodiment of the present invention. FIG. In 2 denotes the reference number 015 a Fourier transform accumulation circuit, the reference numeral 016 denotes an inter-sample Fourier transform circuit, and the reference numeral 017 denotes a detection circuit. Same configurations as those in 1 are denoted by identical reference numerals and their description is omitted.

Hereinafter, the operation of the radar apparatus according to the second embodiment of the present invention will be described. The process of generating the transmitted waves by the oscillator 001 until the Fourier transform is performed on the beat signal by the Fourier transform circuit 006 is identical to that in the above-described first embodiment. The Fourier transform accumulation circuit 015 It accumulates the Fourier transform of the beat signal produced by the Fourier transform circuit 006 was calculated for a given number of samples. The inter-sample Fourier transform circuit 016 subjects the Fourier transform of the beat signal to the Fourier transform in the scan direction. The Fourier transform in the scanning direction will be described below. In the Fourier transform of the beat signal of the up-chirp observation, the signals having the same beat frequency are extracted, and the signal sequence arranged in the scanning order is subjected to Fourier transformation. The axis of the signal sequences after the Fourier transform is referred to provisionally in this specification as the "frequency in the scan direction". This processing is implemented at all beat frequencies. The signal obtained after processing is defined by two dimensions of the beat frequency axis and the scan line frequency axis.

That the Fourier transform is performed on the plurality of strobe signals, means the execution the coherent one Integration assuming different relative speeds v to obtain the integration results of the S / N ratio, which is at the relative speed higher is.

The detection circuit 017 picks up the signal that has undergone the inter-sample integration, and performs the detection process. More specifically, in the case where the electrical energy of the input signal exceeds a predetermined threshold, the detection circuit determines 017 that the signal was detected. Because the signal is in the detection circuit 017 is input, which is the signal subjected to the inter-sampling integration, it is considered that the S / N ratio has been sufficiently obtained. For this reason, the threshold used in the detection circuit 017 is set so that the probability of a false alarm is sufficiently small.

The Beating frequency detected in the peak is called the Detection result output.

According to the second embodiment Is it possible, because the integration between the samples without performing the the first acquisition process can be performed, the collection capacity at the greater distance to improve with the simple signal processing configuration.

Third embodiment

The above embodiments are embodiments in the case where the inter-sampling change of the transmission frequency at the time of the sampling start can be ignored. Hereinafter, an embodiment will be described in which, in the case where the inter-sampling change of the transmission frequency at the time of the sampling start can not be ignored, the phase shift caused by this influence is compensated. It should be noted that 4 schematically shows the appearance in which the sampling start transmission frequency varies. In comparison with a sample 1, the transmission frequency at the sampling start time is shifted by Δα ₁ at a sampling 1.

3 FIG. 10 is a block diagram illustrating the configuration of a radar apparatus according to a third embodiment of the present invention. FIG. In 3 denotes the reference number 018 a sampling start frequency estimation circuit. It should be noted that the same configurations as those in 1 are denoted by identical reference numerals, and their description is omitted.

The operation of the radar apparatus according to the third embodiment will be described below. The mode of operation according to which the oscillator 001 generates the transmitted waves, the first detection signal accumulation circuit 009 accumulates the first detected signal and the first detection distance and speed measuring circuit 010 measures the distance and the speed is identical to that of the above-described first embodiment. The sample start frequency estimation circuit 018 estimates the change in the size of the sampling start frequency by the following method.

It is assumed that many 1 and 2 are detected with higher S / N ratio among the signals included in the first detection signal accumulation circuit 009 be accumulated. for these two targets with higher S / N ratio, expression (14) is represented by the following expressions (14-1) and 14-2), respectively. It should be noted that in these terms, an index 0 indicating the initial phase is omitted.

Expression (14) for the target 1 with higher S / N ratio:

Expression (14) for the target 2 with higher S / N ratio:

It should be noted that r ₁ and r _{2 are} distances of the respective targets with higher S / N ratio, and v ₁ and v ₂ are speeds of the respective targets having the higher S / N ratio. When represented by matrix and vector, expression (14) is represented as follows.

The above simultaneous linear equation is solved to thereby obtain v ₁ , v ₂ , Δα ₂ , Δα ₃ and Δα ₄ . It is to be noted that the reason why the speed is unknown is that the observation time of the signal used in the inter-sampling integration is longer than that in the case where the inter-sampling integration is not performed, and therefore an accuracy of the coefficient of the Phase correcting member (the first term of the right side each in the expression (14-1) and the expression (14-2)), which is in proportion to the observation time t _l , required for the coherent integration.

The above obtained Δα _l is calculated from the target having a higher S / N ratio. However, these values represent the characteristics of the hardware of the radar apparatus and do not depend on the target. Therefore, if Δα _{1 is} used, it is possible to perform the phase compensation on other targets. That is, the phase compensation amount calculating circuit 011 is capable of determining the phase amount of the second term of the right-hand side in the expression (14) in accordance with Δα ₁ determined by the sampling start-end frequency estimating circuit 018 and the distance determined by the first detection distance and speed measurement circuit 010 is estimated to charge. In addition, regarding the phase term of the first term of the right side of the pressure (14), it is possible to calculate the phase compensation amount on the basis of the velocity detected by the first detection distance and speed measuring circuit 010 is obtained in the same manner as in the first embodiment.

The phase compensation circuit 012 subjects the signal to the first detection signal accumulation circuit 009 the phase compensation according to the phase compensation amount generated by the phase compensation amount calculating circuit 011 was calculated. As a result, the same operation as in the first embodiment is performed in the post-process, that is, the process performed by the inter-sample integration circuit 013 and the second detection circuit 014 is carried out.

The method of calculating Δα _l based on the two targets having a higher S / N ratio is described above, but in the case where there are three or more targets having a higher S / N ratio, Δα _{1 may be} based on of the received signals from three or more targets with higher S / N ratio. As a method, there is a method in which a plurality of combinations of the two targets having a higher S / N ratio are set, and the average of Δα _l calculated by the respective combinations is formed as a final estimation result. Alternatively, there is a method in which the relations of the expression (14) obtained for at least three higher S / N ratio targets are combined to calculate Δα ₁ by the least squares method. In any case, the number of received signals used for the estimation is increased, and thus it is possible to improve the estimation accuracy of Δα _l .

As As described above, it is according to the third embodiment possible, even for the case that stability the radar device insufficient high and the inter-sampling change the transmission frequency at the time of the sampling start are not ignored can, an improvement of the detection capability due to the coherent inter-sampling integration to realize.

Fourth embodiment

The above-described third embodiment is an embodiment for the Case, that the interscast change the transmission frequency at the time of the sampling start are not ignored can compensate for the phase shift caused by this influence becomes. In the same way, another embodiment will be described, that by the interabtast change the transmission frequency at the time of the sample start caused phase shift compensated.

5 FIG. 12 is a block diagram illustrating the configuration of a radar apparatus according to this embodiment. FIG. All references in 5 are identical to those in the previous Ausfüh described examples, and therefore their description is omitted. It should be noted that there is a difference between the configurations of the 3 and 5 This is because the in 3 shown interscast integration circuit 013 by the inter-sample Fourier transform circuit 016 in 5 is replaced.

Next, the operation of the radar apparatus according to the fourth embodiment will be described. The oscillator 001 generates the transmitted waves, the first detection signal accumulation circuit 009 The first detected distance signal, the first detection distance and speed measuring circuit accumulates 010 measures the distance and the speed, and the sampling start frequency estimation circuit 018 calculates the change amount of the sampling start transmission frequency. This operation is identical to that in the above-described third embodiment. In addition, the phase compensation amount calculating circuit calculates 011 the phase amount of the second right-side member in the aforementioned expression (14) in the same manner as in the third embodiment. It should be noted that the phase amount of the first term of the right side of the above expression (14) is not particularly calculated, and the phase compensation of the phase compensation circuit 012 is also performed only on the second term of the right side in expression (14).

The phase compensation circuit 012 subjects the signal which has been compensated in phase to the inter-sample Fourier transform operation by the inter-sample Fourier transform circuit 016 , This process is substantially identical to the operation of the inter-sample Fourier transform circuit 016 in the second embodiment. It should be noted that in the second embodiment, all the beat frequency components are subjected to the inter-sample Fourier transform process. However, in this embodiment, the first detection operation by the first detection circuit 008 is performed so that the inter-sample Fourier transform operation is performed only on the beat frequency component generated by the detection operation of the first detection circuit 008 was pulled out. The second detection circuit 014 performs the detection operation on the signal defined by the two dimensions of the beat frequency axis and the frequency axis in the scanning direction.

As As described above, it is according to the fourth embodiment possible, even for the case that stability the radar device is not high enough and the inter-sampling change the transmission frequency at the time of the sampling start are not ignored can improve the detection capability due to the coherent inter-sample integration much like to realize in the above third embodiment.

Fifth embodiment

The above-described third and fourth embodiments are embodiments in which, in the case where the inter-sampling change of the transmission frequency at the time of the sampling start can not be ignored, the phase shift caused by this influence is compensated. Specifically, the inter-sample change amount of the transmission frequency at the time of the sampling start is calculated, and the phase compensation amount is estimated. In the estimation, the distance of the target with higher S / N ratio is obtained by using the result obtained from the first detection distance and speed measurement circuit 010 was calculated. In this embodiment, the distance of the target with higher S / N ratio is estimated with the interabtast variation amount of the transmission frequency at the time of the sampling start without using the processing results of the first detection distance and speed measuring circuit 010 ,

6 FIG. 15 is a block diagram illustrating the configuration of a radar apparatus according to the fifth embodiment of the present invention. FIG. Alone 6 The reference numerals shown are identical to those described above. 6 is essentially identical in configuration with 5 , However, that is 6 across from 5 only different in that the output of the first detection distance and speed measuring circuit 010 not in the sample start frequency estimation circuit 018 is entered.

When next The operation of the radar apparatus according to the fifth embodiment will be described. It is now assumed that three targets with higher S / N ratio are detected become. For these three goals with higher S / N ratio Expression (14) is represented as follows.

Expression (14) for the target 1 with higher S / N ratio:

Expression (14) for the target 2 with higher S / N ratio:

Expression (14) for target 3 with higher S / N ratio:

In these terms, the unknowns are the nine values v ₁ , v ₂ , v ₃ , r ₁ , r ₂ , r ₃ , Δα ₂ , Δα ₃ and Δα ₄ . On the other hand, the measured values as a whole are the new values ΔΦ _{1, l} , ΔΦ _{2, l} and ΔΦ _{3, l} (l = 1, 2, 3). The number of unknowns is equal to that of the observed values, so that it is possible to estimate Δα _l by solving the simultaneous equation.

Assuming that the number of targets with higher S / N ratio is N, the number of unknowns is 2N + 3, and the number of observed values is 3N. In the case where N is three or more, the number of observed values is that of the unknown, so that the unknowns can be estimated. It should be noted that the simultaneous equation contains the product of the distance and Δα _l , so that the simultaneous equation is a non-linear equation. Therefore, the unknown is estimated by the nonlinear optimizing manner. The normally known method can be used for the non-linear optimizing manner. The other operations are identical to the operations in the fourth embodiment.

In this embodiment, the operation of the sampling start frequency estimating circuit becomes 018 changed according to the fourth embodiment. In the configuration according to the third embodiment, the sampling start transmission frequency estimation circuit 018 be replaced by the according to this embodiment.

As As described above, it is possible according to the fifth embodiment, even in the case, that stability the radar device is not high enough and the inter-sampling change the transmission frequency at the time of the sampling start are not ignored can improve the detection capability due to the coherent inter-sample integration much like to realize in the above third embodiment.

Claims (13)

A radar apparatus that radiates waves into a space that receives waves reflected and scattered by an object existing within the space and that subjects the received waves to signal processing to measure the object, which radar apparatus comprises: a transmitting antenna (10); 003 ), which radiates the waves into the room; a receiving antenna ( 004 ) which picks up the waves reflected and scattered by the object from the space; a receiving circuit ( 005 ) detecting the reception waves received by the reception antenna to produce a reception signal; a Fourier transform circuit ( 006 - 009 ) extracting the received signal within a given time range and subjecting the received signal to Fourier transform to calculate a Fourier transformed received signal; and an integration circuit ( 013 ) integrating the Fourier-transformed received signals calculated in multiple time domains at each of the same frequencies. Radar device according to claim 1, in which the waves, which were broadcast from the transmitting antenna in the room, inside be linearly frequency modulated in a given time range, and the given time range while that of the Fourier transform by the Fourier transform circuit to be subjected to receive signal is substantially is equal to the time domain of the frequency modulation. Radar device according to Claim 1, in which the integration circuit ( 013 ) an addition process as performs the integration while the phase of the signal remains. Radar device according to Claim 1, in which the integration circuit ( 013 ) performs an addition process with the amplitude or electrical energy of the signal as the integration. A radar apparatus according to claim 1, wherein the integration process performs the integration process by the Fourier transform. Radar device according to Claim 2, in which the integration circuit ( 013 ) integrates the Fourier transformed received signal after correcting the phase with the amount proportional to the relative velocity of the target and a frequency modulation start time difference. Radar device according to claim 6, at the Containing frequency modulation in two types of time periods a period of time in which the transmission frequency is linear with time elevated is, and a period in which the transmission frequency with the Time is reduced linearly, at the Radar device further comprises a frequency modulation speed calculation circuit, the output signals of the Fourier transform circuit in the respective time periods combined to the relative To calculate the speed of the object, and at the amount the phase correction based on the relative speed of a target generated by the frequency modulation speed calculating circuit calculated. Radar device according to Claim 2, in which the integration circuit ( 013 ) integrates the Fourier transformed received signal after correcting the phase with the amount proportional to the relative distance of the target and the amount of change in the transmission frequency at the time of the frequency modulation start. Radar device according to claim 8, at the Containing frequency modulation in two types of time periods a period of time in which the transmission frequency is linear with time elevated is, and a period in which the transmission frequency with the Time is reduced linearly, is performed, at the Radar apparatus further comprising a frequency modulation distance calculating circuit having the output signals of the Fourier transform circuit in the respective Periods combined with each other to the relative distance to calculate the object, and at the amount of phase correction based on the relative distance of a target through the frequency modulation distance calculating circuit was calculated is calculated. A radar apparatus according to claim 8, wherein the frequency modulation start frequency difference based on the received signals corresponding to two or more Aiming and a relational expression based on the relative speeds and the frequency modulation start frequency differences of the respective ones Objectives is calculated. A radar apparatus according to claim 8, wherein the frequency modulation start frequency difference based on the received signals corresponding to three or more Goals and a relationship expression based on the relative distances that relative velocities and the frequency modulation start frequency differences the respective goals is calculated. Radar apparatus according to claim 10 or 11, wherein the received signal for uses the calculation of the frequency modulation start frequency difference becomes, from the received signal, the higher in the reception intensity or the Signal-to-noise ratio (S / N ratio) is, selected becomes. Radar apparatus according to claim 10 or 11, wherein the received signal for uses the calculation of the frequency modulation start frequency difference from the received signal corresponding to a destination at a destination with shorter Distance selected is.