JP2009139321A - Radar signal processing apparatus and method - Google Patents

Abstract

【the purpose】
Provided is a signal processing method for a frequency modulation (FM-CW) radar that eliminates an interference signal in a radar reception signal and a discontinuity in a beat signal. In addition, an interpolation method that does not affect the subsequent signal processing after interference removal is proposed.
【Constitution】
An interference determination unit that determines whether a sample value at each sampling time of a beat signal is an interference signal or a regular reception signal, and the interference determination unit determines that the sample value is an interference signal A radar signal processing apparatus having an interference removal unit including a beat signal interpolation unit that interpolates the interference signal into a correct value by using a sampled beat signal.
[Selection] Figure 2

Description

The present invention relates to a radar apparatus and a method used in the radar system, and more particularly, to a radar system for removing an interference signal found in a reflected signal of a radar and a method for the same. The present invention also relates to a radar signal processing apparatus that interpolates signals so as not to affect signal processing results after performing interference removal.

As already known, FM-CW radar is a radar that continuously transmits a frequency-modulated wave. By observing the difference between the frequency of the transmitted signal and the received signal, the presence or absence of a target within the radar measurement range and the presence of the target can be identified. it can. The difference in frequency between the transmission signal and the reception signal can be observed by acquiring a beat signal.

A beat signal is a signal having a frequency difference as a frequency component between a transmission signal and a reception signal. By observing the spectrum of the beat signal by Fourier transform, it is possible to specify a frequency having a large spectrum amplitude as a beat frequency that is a difference between the frequency of the transmission signal and the reception signal.

The difference between the frequency of the transmitted signal and the received signal is proportional to the time until the signal transmitted from the radar is reflected and received by the target, so the distance to the target is specified by observing the beat frequency. can do.

In the FM-CW radar, a frequency-modulated wave is output from a voltage-controlled oscillator VCO 101 as shown in FIG. The frequency-modulated wave output from the VCO is branched into a direction toward the transmission antenna 105 and a direction of the frequency mixer 111 of the reception system by the distributor PD103. When the signal branched to the transmission antenna 105 is transmitted from the transmission antenna 105, it is reflected by the target and received by the reception antenna 107.

On the other hand, the signal branched from the distributor PD 103 toward the receiving frequency mixer 111 is frequency-mixed by the frequency mixer 111 with the received signal received by the receiving antenna 107. The output of the frequency mixer is input to the amplifier 109, and the output of the amplifier 109 is input to the low-pass filter 113. The output of the low-pass filter 113 is a beat signal whose frequency component is the difference between the transmission frequency and the reception frequency. The beat signal is input to the AD converter 115 and converted into a digital value by sampling the analog signal. The sampled beat signal is input to a radar signal processing device 117 having a beat signal interpolation unit, and signal processing is performed according to the data flow shown in FIG.

After being sampled by the AD converter 201 and converted to a digital value, the beat signal input to the signal processing device is subjected to interference removal 203 in the interference removal unit, and then converted to the frequency domain by the Fourier transform 205. The signal converted into the frequency domain is output as a frequency spectrum through absolute value calculation 207 and logarithmization 209. In the FM-CW radar, the frequency axis of the frequency spectrum corresponds to the distance to the target. By observing the frequency spectrum, it can be determined that there is a reflective target at a frequency (distance) having a large amplitude, and further, the distance to the reflective target can be specified. In general, the observation result of the frequency spectrum is displayed on the display device 211 after being imaged corresponding to the direction and distance in the observation range and observed.

The reflected signal includes unnecessary components such as noise and interference signals. Unnecessary components include noise due to electrical properties in the radar apparatus and external factors such as interference signals in which transmission / reception signals are affected outside the radar apparatus. Since these unnecessary components adversely affect the target detection performance of the radar, it is necessary to remove them as much as possible.
System noise in the radar apparatus can be improved by modifying the radar apparatus itself (see Non-Patent Document 1). However, since the components due to external factors such as interference signals, where the transmitted and received waves are affected outside the system, are irregular and undefined, the means to remove them is to prevent any sudden external factors. A method should be selected that can automatically detect and remove this.

Noise components (including interference signals) have a serious effect on target detection. FIG. 3 shows the result of Fourier transform of a beat signal having a beat frequency component proportional to the distance to the target. 301 represents the signal spectrum of the beat frequency, and the beat frequency and further the distance to the target can be known by reading the frequency of this spectrum. 303 is a result of Fourier transform of a signal including a pulsed interference signal in the beat signal, and 305 is a result of Fourier transform of a signal not including the interference signal.

When a pulse-like interference signal is included, as shown by 303 and 305, the noise floor is high over a wide range on the frequency axis as compared with a signal not including the interference signal. When the level of the reflected signal by the target is small, the noise floor is high, which causes the signal spectrum of the target to be buried in the noise floor. Further, an interference signal having a specific frequency component may cause erroneous information in determination of the presence or absence of a target or distance measurement.

In the conventional interference cancellation technique, when the beat frequency is high and the shape of the interference signal is similar, it is difficult to determine the interference signal (see Patent Document 1). The present invention relates to a radar signal processing apparatus that detects an interference signal regardless of the shape and beat frequency of the interference signal and performs interpolation so as not to affect subsequent signal processing.

JP 2006-171001 A "Revised radar technology", The Institute of Electronics, Information and Communication Engineers

Provided is a signal processing method for a frequency modulation (FM-CW) radar that eliminates an interference signal in a radar reception signal and a discontinuity in a beat signal. In addition, an interpolation method that does not affect the subsequent signal processing after interference removal is proposed.

In order to solve the above problems, the present invention relates to an FM-CW radar signal processing apparatus and method capable of simultaneously measuring the distance and velocity of a moving object by transmitting and receiving a frequency-modulated continuous wave signal.
An interference determination unit that determines whether a sample value at each sampling time of the beat signal is an interference signal or a regular reception signal;
A beat signal interpolation unit that interpolates the interference signal to a correct value by using a sampled beat signal when the interference determination unit determines that the sample value is an interference signal;
A radar signal processing apparatus having an interference removing unit consisting of

Further, in the present invention, the interference determination unit determines the presence or absence of an interference signal based on a differential sequence of the sampled beat signal and a value obtained by differentiating the differential sequence,
When the distance between two points for obtaining a difference string is a difference distance, a difference string is changed to a predetermined value with respect to the sampled beat signal, and a first-order difference string is calculated. A first floor difference calculation unit;
A time differentiation calculation unit for differentiating in time the sequence of the first order difference calculated by the first order difference calculation unit;
A first-order difference amplitude average calculation unit that obtains an average amplitude value of the first-order difference by calculating an average value of absolute values over all times with respect to the first-order difference column calculated by the first-order difference calculation unit;
When the difference distance that minimizes the first-order difference amplitude average value is the in-phase difference distance, the first-order difference amplitude average calculation unit calculates the amplitude average value of the first-order difference while changing the difference distance by a certain amount. A common-mode difference distance search unit for searching for a common-mode difference distance;
At the in-phase difference distance, the absolute value of the first-order difference calculated in all discrete time ranges is greater than a preset threshold value, or the time differential of the first-order difference calculated in all discrete time ranges A first determination unit that determines that there is an interference signal when the absolute value is greater than a preset threshold;
When the absolute value of the first-order difference calculated in all discrete time ranges is greater than a preset threshold value or calculated in all discrete time ranges at a difference distance twice the specified in-phase difference distance A second determination unit that determines that there is an interference signal when the absolute value of the time differential of the first-order difference is greater than a preset threshold;
Regarding the determination results of the first determination unit and the second determination unit, there is an interference signal only at the time when there is an interference signal in both determination units, and a normal received signal without the interference signal at a time when it is not. A radar signal processing apparatus and method characterized by having a comprehensive judgment unit for judging that there is a radar signal.

Further, according to the present invention, the beat signal interpolation unit, when it is determined that an interference signal exists, an interference point number calculation unit that counts the number of sampling of the interference signal;
When it is determined that an interference signal is included at a specific time of the beat signal, and the in-phase difference distance obtained by the in-phase difference distance search unit is not 1, the beat signal at the time is determined as the in-phase difference. A first beat signal replacement unit that replaces the average value of two points on the beat signal separated by a minute distance;
When the in-phase difference distance is smaller than the sampling number obtained by the interference point number calculation unit, a new in-phase difference distance is searched for a range not including an interference signal in the beat signal, and the in-phase difference distance from the time is calculated. A second beat signal replacement unit that calculates and replaces the average value by two points separated in the forward and backward directions,
A third beat signal replacement unit that calculates the slope of a curve from two points before and after the interference signal when the in-phase difference distance is 1, and calculates and replaces a replacement value using a first-order approximation;
And a radar signal processing apparatus and method for replacing a beat signal at a location including interference without affecting the beat frequency with a signal not including interference.

In beat signals, discontinuities of beat signals due to external factors such as interference signals that adversely affect the results of signal processing are removed, and interpolation is performed so that beat frequency components are not affected. The detection probability of the mark is improved.

The interference signal removal according to the present invention is performed in the interference removal unit shown in FIG. In the interference removal processing according to the present invention, the presence or absence of an interference signal is determined by the interference determination unit 401 shown in FIG. Interpolate the part determined by the interpolator as having an interference signal.

FIG. 5 shows a flow of processing for determining the interference signal. Subject to the signal x _j of the processing is a time-series signal of length N which is sampled. The time series is expressed in discrete time (j = 1, 2, 3,..., N). As indicated by reference numeral 501 in FIG. 5, the signal x _j to be processed is subtracted from the signal x _{j + 1 which} is a difference distance of 1 on the time axis. The subtraction is repeated in the range of discrete time (j = 1, 2, 3,..., N−1).

The following is a x _j, and so take a subtraction of the two only the signal x _{j + 2} took the difference metric in the time axis, will shift the differential distance d from 1 to the specified value D (e.g. N / 4), Calculate the first floor difference.

The specified value D can be up to N−1, but as the difference distance d increases, the range of data for which the first-order difference can be calculated decreases, and there is a possibility that appropriate processing cannot be performed. Therefore, the specified value D may be determined from the sampling number N, for example, N / 4.

Next, as indicated by reference numeral 503 in FIG. 5, with respect to the first-order difference array Δ _{d, j} at each difference distance d, the average value of absolute values over all times (j = 1, 2, 3,..., N−d). to calculate the a _d.

As indicated by reference numeral 505 in FIG. 5, the difference distance d when _Ad is minimized is set as the in-phase difference distance δ.

Further, in the differential distance d = [delta] delta _[delta], in order to know the slope of the _j, the delta _[delta] as shown in 507 of FIG. _5, first order differential delta _[delta] of _j, calculates the _j '.

Next, as shown by 509 in FIG. 5, the first-order differential array Δ _{d, j} ′ at the in-phase difference distance δ is absolute over all times (j = 1, 2, 3,..., N-δ-1). An average value A _δ ′ of values is calculated.

When d = δ, x _{j + δ} and x _j have the same beat signal phase, or x _{j + d} and x _j are in the closest phase among all difference distances d. However, when the frequency of the beat signal is low, the phase of x _{j + d} becomes farther from x _{j as} d is increased. In that case, when d = 1, it is considered that the state is closest to the same phase, and δ = 1. The value of the in-phase difference distance δ depends on the frequency component of the beat signal to be processed.

A method for determining the presence or absence of interference will be described.
(1) At the in-phase difference distance δ, the point where the interference signal exists is the amplitude of the first-order difference Δ _{δ, j} calculated in the range of discrete time (j = 1, 2, 3,..., N−δ). Increases and the amplitude decreases at points other than the interference signal. Therefore, as indicated by reference numeral 511 in FIG. 5, a point where | Δ _{δ, j} | / A _δ normalized by the average value A _δ at d = δ is larger than a prescribed threshold value θ (for example, 3) indicates that there is an interference signal. judge. Further, as shown by 701 in FIG. 7A, in the case where the interference signal is a signal that maintains a constant level, | Δ _{δ, j} | = 0 as shown by 703 in FIG. 7B. . Also in this case, it is determined that there is an interference signal.

(2) Depending on the shape of the interference signal, for example, in the case of the signal as shown in FIG. 8A, the first-order difference Δδ _{, j} is different at the point where the interference signal exists as indicated by reference numeral 801 in FIG. The amplitude may repeat high and low. Therefore, in order to determine that there is interference even when the amplitude of the first-order difference Δ _{δ, j} fluctuates drastically, as shown by 803 in FIG. 8C, the discrete time (j = 1) at the in-phase difference distance δ. , 2,3, ..., N-δ ) Δ δ calculated in a range _of, first order differential value of the _j delta _[delta], is also noted _j '. | Judged observing the | '/ A _[delta]', with interference signal points greater than the threshold and delta _{[delta], j} | | normalized by 'average value A _[delta] of' delta _{[delta], j.}

As shown by reference numeral 701 in FIG. 7A, in the case where the interference signal is a signal that maintains a constant level, as shown by reference numeral 705 in FIG. 7C, | Δδ _{, j} ′ | = 0. . Also in this case, it is determined that there is an interference signal as indicated by 513 in FIG.

As indicated by 515 in FIG. 5, from the results of (1) and (2), the absolute value | Δ _{δ, j} | / A _δ of the first-order difference at the in-phase difference distance _δ is | Δ _{δ, j} | / A _δ > θ or | Δ _{δ, j} | / A _δ = 0, or absolute value of time differential of first-order difference | Δ _{d, j} ′ | / A _δ ′> θ ′ or | Δ _{δ, j} ′ When | / A _δ ′ = 0, it is determined that there is an interference signal, and the digital value R _j ⁽¹⁾ = 1.

Or, when both | Δ _{δ, j} | / A _δ > θ and | Δ _{δ, j} ′ | / A _δ ′> θ ′ hold, | Δ _{δ, j} | / A _δ = 0 and | Δ _{δ, j} R _j ⁽¹⁾ = 1 is set even when both of | ′ / _Aδ ′ = 0 hold. If none of the above applies, R _j ⁽¹⁾ = 0.

FIG. 9A shows a beat signal including an interference signal. 901 in FIG. 9A is an interference signal. FIG. 9B shows an enlarged view of 901. In the first-order difference at d = δ shown in FIG. 9C and the time difference of the first-order difference shown in FIG. 9D, | Δ _{δ, j} | and | Δ _{δ, j} ′ | Not only the point but also the point away from 2δ increases in amplitude. Further, in the time differentiation of the first-order difference at d = 2δ shown in FIG. 9 (e) and the first-order difference shown in FIG. 9 (f), the points separated by 4δ are also | Δδ _{, j} | and | Δδ _{, j} ′. The amplitude of | increases. This is like a mirror image, and since there is actually no interference signal, it must be removed.

Therefore, in addition to d = δ, | Δ _{δ, j} | and | Δ _{δ, j} ′ | are also calculated for d = 2δ, which is twice the in-phase difference distance, and the above (1) and (2) The determination is similarly made in the procedures (3) and (4).

(3) The point where the interference signal exists at d = 2δ, which is twice the in-phase difference distance, is the first-order difference calculated in the range of discrete time (j = 1, 2, 3,..., N-2δ). The amplitude of _{Δ2δ, j} is increased, and the amplitude is reduced for points other than the interference signal. As indicated by reference numeral 517 in FIG. 5, it is determined that there is an interference signal at a point _where | Δ _{2δ, j} | / A _2δ normalized by the average value A _2δ at d = 2δ is larger than a predetermined threshold θ (for example, 3). To do.

Further, as indicated by reference numeral 701 in FIG. 7A, in the case where the interference signal has a constant level, as indicated by reference numeral 703 in FIG. Δ _{2δ, j} | = 0. Also in this case, it is determined that there is an interference signal.

(4) Due to the shape of the interference signal, for example, in the case of a signal as shown in FIG. 8A, as in the case of d = δ, there is an interference signal as shown at 801 in FIG. 8B. There is a case where the amplitude of the first-order difference Δ _{2δ, j} repeatedly increases and _decreases . Therefore, in order to determine that there is interference even when the amplitude of the first-order difference Δ _{2δ, j} fluctuates drastically, as indicated by 803 in FIG. 8C, at d = 2δ, which is twice the in-phase difference distance, _{Note also} the first-order differential value Δ _{2δ, j} ′ for Δ _{2δ, j} calculated in the range of discrete time (j = 1, 2, 3,..., N−2δ). | Δ _{2δ, j} determines to observe | _'/ A 2δ', with interference signal points greater than the threshold value and '| | average value A _2.delta.' In normalized Δ _{2δ, j.}

As shown at 701 in FIG. 7A, in the case of a signal in which the interference signal maintains a constant level, | Δ _{2δ, j} ′ | = 0 as shown at 705 in FIG. 7C. . Also in this case, it is determined that there is an interference signal as indicated by 519 in FIG.

As indicated by 521 in FIG. 5, from the results of (3) and (4), the absolute value of the first-order difference | Δ _{2δ, j} | / A _{2δ at} d = 2δ, which is twice the in-phase difference distance, is | Δ _{2δ, j} | / A _2δ > θ or | Δ _{2δ, j} | / A _2δ = 0, or the absolute value of the time differential of the first-order difference | Δ _{2δ, j} ′ | / A _2δ ′> θ ′ or When | Δ _{2δ, j} ′ | / A _2δ ′ = 0, it is determined that there is an interference signal, and the digital value R _j ⁽²⁾ = 1 is set.

Or, when both | Δ _{2δ, j} | / A _2δ > θ and | Δ _{2δ, j} ′ | / A _2δ ′> θ ′ hold, | Δ _{2δ, j} | / A _2δ = 0 and | Δ _{2δ, j} R _j ⁽²⁾ = 1 is set even when both of | ′ / A _2δ ′ = 0 hold. If none of the above applies, R _j ⁽²⁾ = 0.

Finally, the presence / absence of an interference signal is determined by combining the results when d = 2δ which is twice the in-phase difference distance and when the in-phase difference distance d = δ. A point where only one of R _j ⁽¹⁾ and R _j ⁽²⁾ is 1, that is, a point determined to have an interference signal is a mirror image. Therefore, as shown at 523 in FIG. 5, when the final result is R _j = 1 by the comprehensive judgment means for obtaining the logical product of R _j ⁽¹⁾ and R _j ⁽²⁾ , the signal x _{j at} time _j is is an interference signal, it determines that the received signal x _j is normal otherwise.

When it is determined that there is an interference signal, it is necessary to perform interpolation after setting the signal to 0 once to remove the interference signal.

Next, the interpolation method will be described. It is necessary to interpolate a portion determined to be an interference signal. When interpolating, the previously obtained δ is used.

  When the place to be interpolated is one point, an interpolating means is effective by taking the average of two points before and after. However, this means is not suitable when interference is included at successive sampling times or when the beat frequency is high, and this means is not used in the present invention.

The flow of the interpolation method in the present invention is shown in FIG. First, the beat signal as shown in 601 of FIG. 6, in that scanning a determination result R _j of the presence or absence of interfering signals performed first, it is determined that there is an interference signal, as shown in 605 of FIG. 6 The presence / absence of the interference signal at the next point is also checked to determine whether the interference signal exists continuously. If there are continuous, the number K of consecutive interference signal points is examined as indicated by reference numeral 603 in FIG.

The first time j is substituted into i at successive sampling times where an interference signal exists. That is, there is a continuous interference signal in the range of (i = j, j + 1,..., J + K−1) at x _j . In the case of interpolating a plurality of consecutive points, interpolation is performed by taking an average value of two points having the same phase across the points to be interpolated in the same sweep signal array. If the number of consecutive interference signal points is K, the interpolation operation is repeated K times.

If it is determined at 607 in FIG. 6 that δ = 1 is not true, if the in-phase difference distance δ is larger than the number of points where an interference signal exists, that is, if δ ≧ K, as indicated by 613 in FIG. The value to be interpolated can be calculated using equation (5).

If the relationship with δ is δ <K, an interference signal also exists at a point that is closest to the point to be interpolated and should be in phase, so that it cannot be used to calculate a value for interpolation. Therefore, an in-phase difference distance δ ′ that is in phase as close as possible to the point to be interpolated is calculated as shown at 615 in FIG. 6 at a point that does not include an interference signal in the beat signal array. δ ′ is calculated using a value obtained by rounding down a decimal point in K / δ.

Using this δ ′, as in Equation (5), an average value is obtained across the points including the interference signal, and an interpolated value is calculated as indicated by reference numeral 617 in FIG.

A state of interpolation using this interpolation method is shown in FIG. FIG. 10A shows a beat signal including an interference signal. After the interference is removed, interpolation by 0 results in a discontinuous state as shown in FIG. When this method is used, smooth interpolation is possible as shown in FIG. This difference is significant when Fourier transform is performed. FIG. 10D shows the result of performing the Fourier transform and converting it to the frequency domain. Reference numeral 1007 in FIG. 10D denotes a signal spectrum indicating the beat frequency.

1001 is the result of frequency conversion of the signal in FIG. 10A, 1003 is the result of frequency conversion of the signal in FIG. 10B, and 1005 is the result of FIG. 10C. When this method is used, it can be seen that the noise floor is lower than the others as indicated by 1005, and the influence on the beat signal is small by appropriately interpolating the interference signal portion.

When δ = 1 in 607 of FIG. 6, that is, when the beat frequency is low, the difference distance that is in phase in the beat signal x _j is unknown, so before and after the presence of the interference signal as indicated by 609 in FIG. 6. The slope m of the curve is calculated from the point using the equation (8), and the linear equation is approximated and interpolated approximately using the equation (9) as indicated by 611 in FIG.

FIG. 11 shows a state of interpolation using this interpolation method. FIG. 11A shows a state where an interference signal exists, and FIG. 11B shows a result of interpolation after removing the interference signal.

A system diagram of a general FM-CW radar is shown. The flow of signal processing when implementing the present invention is shown. The difference in noise floor between when there is an interference signal on the beat signal and when there is no interference signal is shown. The flow of the interference removal method provided by this invention is shown. The flow of the signal processing for determining the presence or absence of an interference signal is shown. The flow of signal processing for interpolating beat signals is shown. An example of an interference signal, its first-order difference, and time differentiation is shown. An example of an interference signal, its first-order difference, and time differentiation is shown. An example of an interference signal, its first-order difference, and time differentiation is shown. It is also a diagram illustrating a mirror image when determining the presence or absence of an interference signal. The effect of the interpolation method provided by the present invention will be described. The effect of the interpolation method provided by the present invention will be described.

Explanation of symbols

101 ... Transmitter, 103 ... Distributor,
105 ... transmitting antenna, 107 ... receiving antenna,
109 ... Amplifier, 111 ... Frequency mixer,
113 ... Low-pass filter, 115 ... AD converter,
117 ... Signal processing device,
201 ... AD converter, 203 ... Signal processing for interference removal,
205 ... Fourier transform unit, 207 ... Absolute value unit,
209 ... logarithmization unit, 211 ... display device,
301 ... Signal spectrum, 303 ... Signal spectrum including interference signal,
305 ... Signal spectrum not including interference signal,
401 ... interference determination unit, 403 ... beat signal interpolation unit,
501 ... Subtraction processing at a certain difference distance,
503 ... Calculation process of the average amplitude of the first floor difference,
505 ... In-phase difference distance calculation processing, 507 ... First floor difference inclination calculation processing,
509 ... Time differential amplitude average calculation processing,
511, 513 ... branching processing for determining the presence or absence of interference signals,
515, 521 ... interference signal determination processing,
517, 519 ... branch processing for determining the presence or absence of interference signals,
523 ... Comprehensive determination processing,
601... Branching process based on the determination result of the presence or absence of an interference signal,
603... Counting processing of consecutive interference signals,
605... Branching process based on the determination result of the presence or absence of an interference signal at the next point,
607 ... Branch processing of whether the beat frequency is low,
609: Processing using points before and after the presence point of the interference signal,
611, 613 ... interpolation processing, 615 ... in-phase difference distance calculation processing,
617 ... interpolation processing,
701 ... a state in which the interference signal maintains a certain level,
703, 705...
801 ... A state in which an interference signal exists and the first floor difference is moving up and down,
803... Part where a peak is detected from a point and compared with a threshold value,
901 ... Interference signal,
1001... Signal of FIG. 10 (a), 1003 ... signal of FIG. 10 (b),
1005... Signal of FIG.
1007 ... Signal spectrum indicating the beat frequency.

Claims (3)

Regarding an FM-CW radar signal processing apparatus and method capable of simultaneously measuring the distance and velocity of a moving object by transmitting and receiving a frequency-modulated continuous wave signal,
An interference determination unit that determines whether a sample value at each sampling time of the beat signal is an interference signal or a regular reception signal;
A beat signal interpolation unit that interpolates the interference signal to a correct value by using a sampled beat signal when the interference determination unit determines that the sample value is an interference signal;
A radar signal processing apparatus having an interference removal unit comprising: The interference determination unit is configured to determine the presence or absence of an interference signal based on a differential sequence of the sampled beat signal and a value obtained by differentiating the differential sequence,
When the distance between two points for obtaining a difference string is a difference distance, a difference string is changed to a predetermined value with respect to the sampled beat signal, and a first-order difference string is calculated. A first floor difference calculation unit;
A time differentiation calculation unit for differentiating in time the sequence of the first order difference calculated by the first order difference calculation unit;
A first-order difference amplitude average calculation unit that obtains an average amplitude value of the first-order difference by calculating an average value of absolute values over all times with respect to the first-order difference column calculated by the first-order difference calculation unit;
When the difference distance that minimizes the first-order difference amplitude average value is the in-phase difference distance, the first-order difference amplitude average calculation unit calculates the amplitude average value of the first-order difference while changing the difference distance by a certain amount. A common-mode difference distance search unit for searching for a common-mode difference distance;
At the in-phase difference distance, the absolute value of the first-order difference calculated in all discrete time ranges is greater than a preset threshold value, or the time differential of the first-order difference calculated in all discrete time ranges A first determination unit that determines that there is an interference signal when the absolute value is greater than a preset threshold;
When the absolute value of the first-order difference calculated in all discrete time ranges is greater than a preset threshold value or calculated in all discrete time ranges at a difference distance twice the specified in-phase difference distance A second determination unit that determines that there is an interference signal when the absolute value of the time differential of the first-order difference is greater than a preset threshold;
Regarding the determination results of the first determination unit and the second determination unit, there is an interference signal only at the time when there is an interference signal in both determination units, and a normal received signal without the interference signal at a time when it is not. The radar signal processing apparatus and method according to claim 1, further comprising a comprehensive determination unit that determines that there is one. The beat signal interpolation unit, when it is determined that there is an interference signal, an interference point calculation unit that counts the number of sampling of the interference signal;
When it is determined that an interference signal is included at a specific time of the beat signal, and the in-phase difference distance obtained by the in-phase difference distance search unit is not 1, the beat signal at the time is determined as the in-phase difference. A first beat signal replacement unit that replaces the average value of two points on the beat signal separated by a minute distance;
When the in-phase difference distance is smaller than the sampling number obtained by the interference point number calculation unit, a new in-phase difference distance is searched for a range not including an interference signal in the beat signal, and the in-phase difference distance from the time is calculated. A second beat signal replacement unit that calculates and replaces the average value by two points separated in the forward and backward directions,
A third beat signal replacement unit that calculates the slope of a curve from two points before and after the interference signal when the in-phase difference distance is 1, and calculates and replaces a replacement value using a first-order approximation;
The radar signal according to claim 1, wherein a beat signal at a location including interference is replaced with a signal not including interference without affecting the beat frequency. Processing apparatus and method.