JP7270835B2 - radar equipment - Google Patents

Description

The present disclosure relates to radar equipment. The present disclosure particularly relates to radar equipment with high range resolution.

By transmitting a chirp signal and receiving the reflected wave from the target (target object), the received signal is converted into a beat signal, and the peak is detected from the Fourier transform to detect the target with high range resolution. FMCW (Frequency-Modulated Continuous Wave) radar is known. In FMCW radar, if the bandwidth of the chirp signal is widened, the range resolution can be increased. Therefore, it is being studied to use a plurality of adjacent frequency bands to achieve high range resolution.

For example, Non-Patent Document 1 discloses a fusion method of measurement data of two frequency bands. In the technique of Non-Patent Document 1, the reflected waves are simultaneously measured by transmitters and receivers with frequency bands of 100 GHz and 150 GHz with bandwidths of 40 GHz and 60 GHz, respectively. are aligned, and if there is a frequency gap between two frequency bands, the missing frequency points are linearly interpolated.

F. Friederich, K.; May, B. Baccouche, C.; Matheis, M.; Bauer,J. Jonuscheit, M.; Moor, D. Denman, J.; Bramble, andN. Savage, "Terahertz Radome Inspection," Photonics, vol. 5, no. 1, p. 1, Jan. 2018.

When a moving target is detected by the technique of Non-Patent Document 1, it is not possible to ensure phase continuity between the data of the two frequency bands, distortion, splitting, etc. may not be able to measure.

The present disclosure utilizes multiple adjacent frequency bands to obtain a radar apparatus capable of measuring distance with high resolution without distortion, splitting, etc. in the Fourier transform peak even when the target is moving. With the goal.

The radar device according to the present disclosure is
Synchronizing the first to Mth chirp signals of the mutually adjacent first to Mth (M is an integer of 2 or more) transmission frequency bands having the same bandwidth and having continuous frequency changes every chirp cycle a signal generator that repeatedly generates to
a signal transmission device for transmitting first to Mth transmission waves corresponding to first to Mth chirp signals repeatedly generated by the signal generation device;
first to Mth reception waves corresponding to the first to Mth transmission frequency bands, respectively a signal receiving device that receives signals in a frequency band and generates first to Mth received signals;
frequency components according to the distance to the target from the first to Mth chirp signals generated by the signal generation device and the first to Mth reception signals generated by the signal reception device; a signal conversion device for generating first to Mth beat signals having
a signal synthesizing unit that couples the first to Mth beat signals generated by the signal conversion device with each other at boundaries between the chirp periods to generate one synthesized signal for each chirp period;
a target detection unit that calculates a distance to a target and a speed of the target from a plurality of synthesized signals sequentially generated by the signal synthesis unit;

According to the radar device of the present disclosure, even if the target is moving, it is possible to measure the distance with high resolution without generating distortion, splitting, etc. in the Fourier transform peak.

1 is a block diagram showing an outline of a radar device according to an embodiment; FIG. 2 is a block diagram showing a specific configuration example of the radar device of FIG. 1; FIG. 2 is a block diagram showing a configuration example of the signal processing device of FIG. 1; FIG. (a) is a waveform diagram showing the transmission signal and the reception signal of the radar device of the embodiment, (b) to (d) are diagrams showing the beat signal obtained from the above transmission signal and the reception signal, (e) (g) is a diagram showing a composite signal obtained by concatenating the above beat signals. (a) is an enlarged view of a part of FIG. 4 (a), and a diagram in which the transmission signal, the reception signal, and the frequency difference are denoted by symbols representing periods; (b) is a beat due to the frequency difference in (a) FIG. 11C is a diagram showing one method of concatenating signals according to a comparative example, and (c) is a diagram showing a method of concatenating beat signals based on the frequency difference in (a) according to an embodiment. (a) is an enlarged view of a part of FIG. 4 (a), in which symbols indicating periods are added to the transmission signal, the reception signal, and the frequency difference, and the part of the reception signal that arrives after a delay (b) is a diagram showing a method of synthesizing beat signals based on the frequency difference in (a). FIG. 4 is a diagram showing an example of a result of Fourier transform for one composite signal; FIG. (a) is a diagram showing the results of Fourier transform for a plurality of synthesized signals, and (b) is an example of peak phase change in (a). FIG. 9 is a diagram showing an example of a further Fourier transform result for the Fourier transform result shown in FIG. 8(a); 7 is a flow chart showing an example of a procedure of processing after receiving a reflected wave of the radar device according to the embodiment; 3 is a diagram showing the hardware configuration of a computer that realizes functions of parts other than the antenna of the radar device of the first embodiment; FIG.

FIG. 1 shows an outline of a radar device RD according to an embodiment.
The illustrated radar device RD repeatedly generates chirp signals in first to M-th (M is an integer equal to or greater than 2) frequency bands which are equal in bandwidth and adjacent to each other in synchronization with each other, and transmits them to the target TG. A received signal is generated by receiving a reflected wave due to the reflection of , and the distance to the target TG and the speed of the target TG are calculated based on the beat signal due to the frequency difference between the transmitted chirp signal (transmission signal) and the received signal.
In the following, a case will be described in which the above M is 3 and the chirp signal is an up-chirp signal.

Radar device RD shown in FIG.
The signal transmitter 120 has first to third transmitters 121-123. The signal receiver 130 has first to third receivers 131 to 133 . The signal conversion device 140 has first to third conversion units 141 to 143 .
The first transmitting section 121, the first receiving section 131, and the first converting section 141 are provided in correspondence with each other. The second transmitting section 122, the second receiving section 132, and the second converting section 142 are provided in correspondence with each other. The third transmitting section 123, the third receiving section 133, and the third converting section 143 are provided in correspondence with each other.

FIG. 2 shows a specific configuration example of the radar device RD of FIG.
Radar device RD shown in FIG. 23, transmission/reception switches 31-33, antennas 41-43, amplifiers 51-53, mixers 61-63, amplifiers 71-73, and A/D converters 81-83.
DDS stands for Direct Digital Synthesizer.

A signal generator 110 is composed of the DDS 3, the high-frequency signal generator 4, and the mixers 11-13.

Amplifier 21 , transmission/reception switch 31 , and antenna 41 constitute first transmission section 121 . The amplifier 22 , the transmission/reception switch 32 , and the antenna 42 constitute a second transmission section 122 . The amplifier 23 , the transmission/reception switch 33 , and the antenna 43 constitute a third transmission section 123 .

The antenna 41 , the transmission/reception switch 31 and the amplifier 51 constitute a first receiving section 131 . The antenna 42 , the transmission/reception switch 32 and the amplifier 52 constitute a second receiving section 132 . The antenna 43 , the transmission/reception switch 33 and the amplifier 53 constitute a third receiving section 133 .

Mixer 61 , amplifier 71 , and A/D converter 81 constitute first conversion section 141 . The mixer 62 , the amplifier 72 and the A/D converter 82 constitute a second conversion section 142 . The mixer 63 , the amplifier 73 and the A/D converter 83 constitute the third conversion section 143 .

Since the control device 100 controls the DDS 3 of the signal generation device 110 , it can be regarded as forming a part of the signal generation device 110 .
Similarly, since the control device 100 controls the A/D converters 81 to 83 of the signal conversion device 140 , it can be regarded as forming a part of the signal conversion device 140 .

The signal processing device 150 has a signal synthesizing section 151 and a target detecting section 152, as shown in FIG.

The control device 100, DDS 3, high frequency signal generator 4, A/D converters 81-83, and signal processing device 150 are connected to a common reference signal generator 102 (FIG. 1) and operate synchronously.
It is assumed that each of the mixers 11-13 and 61-63 has a function of filtering out signals other than the desired signal after mixing the signals.

The signal generator 110 generates the first to third chirp signals S ₁ to S ₃ repeatedly and synchronously with each other.
Examples of chirp signals S ₁ -S ₃ are shown in FIG. 4(a).
As shown, each of the chirp signals S ₁ -S ₃ is an up-chirp signal and has the same modulation width, ie, bandwidth. B denotes this modulation width. The frequencies (start frequencies) of the chirp signals S ₁ to S ₃ at the start of chirp are represented by f ₁ to f ₃ , respectively.
The band from f ₁ to f ₁ +B is called the first frequency band and denoted by the symbol FC ₁ . The band from f ₂ to f ₂ +B is called the second frequency band and denoted by the symbol FC ₂ . A band from f ₃ to f ₃ +B is called a third frequency band and denoted by the symbol FC ₃ .

The chirp signals S ₁ to S ₃ have the same cycle length (chirp cycle), and when one cycle ends, the next cycle starts immediately. In FIG. 4A, i, i+1, i+2, . . . are assigned as the period number k.

A chirp signal S _m emitted in a certain frequency band FC _m (where m is 1 or 2 here) in one period and a frequency band FC adjacent to said frequency band FC _m on the higher frequency side in the next period. The frequency change is continuous with the chirp signal S _m+1 emitted at _m+1 . That is, the frequency _fm +B at the end of chirp of the m-th chirp signal _Sm is equal to the frequency fm+1 at the start of chirp of the _m+1-th chirp signal _Sm+1 . Namely
fm ₊₁ = _fm +B
There is a relationship

Also, the phase of the m-th chirp signal _Sm at the end of chirp is equal to the phase of the m+1-th chirp signal _Sm+1 at the start of chirp.

Furthermore, the product of the center frequency h _m (where m is 1, 2 or 3 here) of each of the first to third frequency bands FC ₁ to FC ₃ and the chirp period length T is an integer, The phases (initial phases) φ _1,k to φ _3,k at the start of chirp of the M-th chirp signals S ₁ to S ₃ are equal to each other and are identical to each other in all chirp periods.
Between the center frequency _hm and the frequency _fm at the start of the chirp, there is a relationship represented by the following equation (1).

_The control device 100 controls the modulation width B, the period length T, the start frequencies f ₁ to f ₃ of the chirp signals S _{1 to} S ₃ , the initial phases φ _1, Control is performed so that _k to φ _3,k are values satisfying the above conditions.

It is assumed below that the modulation width B of the chirp signals S ₁ to S ₃ is predetermined. In that case, the control device 100 sets the period length T, the starting frequency f ₁ of the chirp signal S ₁ , and the initial phases φ _1,k to φ _3,k of the periods of the chirp signals S ₁ to S ₃ . specify.

DDS 3 generates chirp signal S ₀ based on predetermined modulation width B, period length T, start frequency f ₁ , and phase φ _1,k specified by controller 100 .
The generated chirp signal S ₀ has a starting frequency of f ₁ −B, an ending frequency of f ₁ , and a period length of T.

A high-frequency signal generator 4 generates a high-frequency signal HF of a predetermined frequency B. FIG.

Chirp signal S ₀ output from DDS 3 is input to mixer 11 .
The mixers 11 to 13 generate chirp signals S ₁ to S ₃ based on the chirp signal S ₀ and the high frequency signal HF generated by the high frequency signal generator 4 .

The DDS 3 and the high frequency signal generator 4 cause the mixers 11 to 13 to generate chirp signals S ₁ to S ₃ whose first phase of each period is a specified value φ _1,k to φ _3,k respectively. , outputs a chirp signal _S0 and a high frequency signal HF. Specifically, the _phase of the chirp signal S ₀ and _the high _{- frequency} signal HF are controlled.

The mixer 11 is supplied with the chirp signal S ₀ from the DDS 3 and the high frequency signal HF from the high frequency signal generator 4 .
_The mixer 11 internally generates a chirp signal S 1 with a start frequency of f ₁ and an end frequency of f ₁ +B, and a chirp signal S _{1 ′} with a start frequency of f ₁ −2B and an end frequency of f ₁ −B. of which the chirp signal S ₁ ′ is filtered out to output the chirp signal S ₁ . This chirp signal S ₁ is supplied to amplifier 21 and mixer 12 .

The mixer 12 is supplied with the chirp signal S ₁ from the mixer 11 and the high frequency signal HF from the high frequency signal generator 4 .
The mixer 12 internally generates a chirp signal S ₂ with a start frequency of f ₁ +B and an end frequency of f ₁ +2B and a chirp signal S ₂ ′ with a start frequency of f ₁ −B and an end frequency of f ₁ . , of which the chirp signal S ₂ ′ is filtered out to output the chirp signal S ₂ . This chirp signal S ₂ is supplied to amplifier 22 and mixer 13 .

The mixer 13 is supplied with the chirp signal S ₂ from the mixer 12 and the high frequency signal HF from the high frequency signal generator 4 .
The mixer 13 internally generates a chirp signal S 3 with a start frequency of f ₁ +2B and an end frequency of f ₁ +3B and a chirp signal S _{3 ′} with a start frequency of f ₁ and an end frequency of f ₁ +B, Among them, the chirp signal S ₃ ′ is filtered out and the chirp signal S ₃ is output. This chirp signal S ₃ is supplied to amplifier 23 .

Thus, the starting frequency _f2 of chirp signal _S2 is equal to the ending frequency _f1 +B of chirp signal _S1 , and the starting frequency _{f3 of} chirp signal _S3 is equal to the ending frequency _f2 +B of chirp signal S2.
Therefore, it can be said that the chirp signals S ₁ to S ₃ have continuous frequency changes.
The chirp signals S ₁ to S ₃ have the same phases φ _1,k to φ _3,k at the start of chirp in each period, and are the same in different periods.

The signal transmitter 120 transmits the chirp signals S ₁ to S ₃ generated by the signal generator 110 as transmission waves.

Chirp signals S ₁ to S ₃ are amplified by amplifiers 21 to 23, respectively, and supplied to antennas 41 to 43 through transmission/reception switches 31 to 33. From antennas 41 to 43, transmission waves corresponding to chirp signals S ₁ to S ₃ are transmitted. is sent.
A transmitted chirp signal is also called a transmitted signal.

The signal reception device 130 receives a reflected wave generated by the reflection of the transmission wave transmitted by the signal transmission device 120 from the target TG and generates a reception signal. A reception signal generated by receiving a reflected wave generated by reflection of a transmission wave corresponding to the transmission signal by the target TG is referred to as a reception signal corresponding to the transmission signal.

The receivers 131 to 133 of the signal receiver 130 are provided corresponding to the frequency bands FC ₁ to FC ₃ respectively. Similarly, conversion units 141 to 143 of signal conversion device 140 are provided corresponding to frequency bands FC ₁ to FC ₃ , respectively.

The reflected waves generated by the reflection of the transmission waves transmitted from the antennas 41 to 43 in each frequency band by the target TG are received by the antennas 41 to 43, and the received signals R ₁ to R ₃ generated as a result are transmitted and received. The signals are amplified by amplifiers 51-53 through switches 31-33.
The amplified received signals R ₁ to R ₃ are provided to signal converter 140 as outputs of signal receiver 130 .

The signal conversion device 140 generates beat signals Q 1 to Q 3 from the reception signals R ₁ to R ₃ output from the signal reception device 130 and the transmission signals _{S 1 to} S ₃ output from the signal generation device ₁₁₀ . .

Specifically, received signals R ₁ to R ₃ output from signal receiver 130 are input to mixers 61 to 63 and mixed with corresponding transmitted signals S ₁ to S ₃ .
A mixer 61 mixes the received signal _R1 and the transmitted signal _S1 and filters out signals other than the desired signal to generate the beat signal _Q1 shown in FIG. 4(b).

A mixer 62 mixes the received signal _R2 and the transmitted signal _S2 and filters out signals other than the desired signal to generate the beat signal _Q2 shown in FIG. 4(c).
A mixer 63 mixes the received signal _R3 and the transmitted signal _S3 and filters out signals other than the desired signal to generate the beat signal _Q3 shown in FIG. 4(d).
In the figure, arrows indicate the start and end of each of the beat signals Q ₁ to Q ₃ .

The frequency of the beat signal _Q1 is equal to the difference between the frequencies of the transmitted signal _S1 and the received signal _R1 . The frequency of the beat signal _Q2 is equal to the difference between the frequencies of the transmitted signal _S2 and the received signal _R2 . The frequency of the beat signal _Q3 is equal to the difference between the frequencies of the transmitted signal _S3 and the received signal _R3 .
In FIG. 4(a), the above frequency differences are given the same symbols as the corresponding beat signals Q ₁ to Q ₃ .

Note that the mixers 61 to 63 have a function of removing signals other than the desired signal. It is desirable that the mixer has a function of filtering out frequency components other than those required to generate the desired beat signals Q ₁ -Q ₃ .

Beat signals Q ₁ -Q ₃ generated by mixers 61-63 are amplified by amplifiers 71-73 and converted into digital signals by A/D converters 81-83. This digital signal is also represented by the same code as the analog beat signals Q ₁ to Q ₃ .

Beat signals Q ₁ to Q ₃ are generated _from transmission signals S ₁ to S ₃ in frequency bands FC ₁ to FC ₃ , _respectively . It is said to be a beat signal in the bands FC ₁ to FC ₃

The signal synthesizing unit 151 of the signal processing device 150 connects the beat signals Q ₁ to Q ₃ as shown in FIGS. 4(e), (f), and (g) to generate a synthesized signal CS for each cycle.

Each synthesized signal CS includes a beat signal _Q1 generated using a transmission signal S1 of a first frequency band _FC1 in a certain cycle (eg, cycle i) and a beat signal _Q1 in the next cycle (eg, cycle i+1). generated using the beat signal _Q2 generated using the transmission signal _S2 of the _second frequency band FC2 and the transmission signal _S3 of the third frequency band FC3 of the next cycle (eg, cycle i+2) _. obtained by concatenating with the beat signal _Q3 .

In connection, the end of the beat signal _Q1 (the portion at the end of the cycle) and the beginning of the beat signal _Q2 (the portion at the start of the cycle) are connected, and the end of the beat signal _Q2 and the beginning of the beat signal _Q3 are connected. connect with
Such concatenation can be said to be a process of switching the beat signal at the boundary point between one cycle and the next cycle, or a process of concatenating the beat signals of each frequency band in ascending order of the frequency of the corresponding frequency band. It can be said that there is.

The target detection unit 152 Fourier-transforms each synthesized signal generated by the signal synthesizing unit 151, arranges the Fourier transforms of the plurality of synthesized signals, performs the Fourier transform in the direction in which they are arranged, and detects the peak to detect the target TG. and the speed of the target TG are calculated.

Conditions for appropriately connecting beat signals in the above radar device RD will be described below.

FIG. 5(a) is an enlarged view of part of FIG. 4(a), with symbols indicating frequency bands and periods for the transmission signal, the reception signal, and the frequency difference. That is, the transmitted signal of period k (k-th period) of frequency band FC _m is indicated by symbol S(m, k), and the received signal of period k of frequency band FC _m is indicated by R(m, k). , a beat signal of period k in frequency band FC _m is denoted by Q(m,k).

The instantaneous value s ^{(m, k)} of the transmission signal of frequency band FC _m with period k is expressed by the following equation (2).

In formula (2),
t is time,
α is the amplitude of the transmitted signal,
f _m is the chirp start frequency of the m-th frequency band FC _m ;
T is the length of the chirp period,
B is the modulation width of the transmission signal, that is, the bandwidth of each frequency band;
Φ _m,k represents the initial phase of chirp period k in the m-th frequency band FC _m .

Assuming that the target TG is in uniform motion at a speed v in the line-of-sight direction of the radar device RD, the instantaneous value r ^{(m, k)} of the received signal obtained by receiving the reflected wave at the target TG is given below. (3).

In equation (3), β is the amplitude of the received signal.
Also, δ is given by the following equation (4).

In equation (4), c is the speed of light.
Also, v is the speed of the target TG, and the direction away from the radar device RD is the positive direction.

In equation (3), _τ0 is the delay time of the received signal at time t=0, and is expressed by equation (5) below.

In equation (5), _x0 represents the position of the target TG at time t=0, that is, the distance from the radar device RD.

Before explaining the method of processing beat signals in a plurality of frequency bands according to the present embodiment, there is generally a phase difference between beat signals generated using received signals simultaneously received in a plurality of frequency bands. Explain that continuity cannot be ensured.

Received signal R( _mr , kr) of period _kr of _{mr- th} frequency band FC mr ( _mr is any one of 1 to _M ) and ms- _th ( _ms is any one of 1 to M) The phase difference between the frequency band FC _ms and the transmission signal S ( _ms , _ks ) with the period ks, that is, the instantaneous _value of the phase of the beat signal Q ( _mr , _kr , _ms , _ks ) is given by the following: It represents with Formula (6).

In equation (6), the values when m _r =m _s =m and k _r = _ks =k, that is, the transmission signal S(m,k) and the reception signal R of period k in the m-th frequency band The instantaneous value of the phase of the beat signal Q(m, k) generated from (m, k) is expressed by the following equation (7).

As a comparative example, as shown in FIGS. 5A and 5B, a beat signal generated from a transmission signal S(m, k) and a reception signal R(m, k) of the m-th frequency band with period k The end of Q(m, k) and the beginning of the beat signal Q(m+1, k) generated from the transmission signal S(m+1, k) and the reception signal R(m+1, k) of period k in the m+1-th frequency band. Think about connecting with
The end of beat signal Q(m,k) is at the end of period k, and the beginning of beat signal Q(m+1,k) is at the start of period k.
The phase difference between the two beat signals at the connecting portion is expressed by Equation (8) below.

When the target TG is stationary, δ=1, so the phase difference expressed by Equation (8) is 0, and phase continuity between beat signals can be ensured.
When the target TG is moving, the phase difference represented by Equation (8) is not necessarily 0 because Equation (8) includes the delay time _τ0 . That is, phase continuity between beat signals cannot be ensured.

On the other hand, in this embodiment, connection is performed as follows. That is, as shown in FIGS. 5A and 5C, a beat signal Q(m , k) and the beginning of the beat signal Q(m+1, k+1) generated from the transmission signal S(m+1, k+1) and the reception signal R(m+1, k+1) with period k+1 of the m-th frequency band. .

The end of beat signal Q(m,k) is at the end of period k and the beginning of beat signal Q(m+1,k+1) is at the start of period k+1.
The phase difference between the two beat signals at the connecting portion is 0 as expressed by the following equation (9).

In this way, since the phase difference between the two beat signals is 0, phase continuity between the beat signals can be ensured even if the target TG is moving. As a result, high range resolution can be achieved without causing distortion, splitting, etc. in the Fourier transform peak of the combined signal.

Next, the portion of the received signal that arrives after being delayed in the next chirp period will be described with reference to FIG. 6(a). A received signal that arrives with a delay means a received signal that corresponds to a reflected wave that arrives with a delay.
FIG. 6(a) is similar to FIG. 5(a), but shows the part of the received signal that arrives with a delay in the next chirp period.
"The portion of the received signal that arrives after being delayed in the next chirp period" means the portion of the received signal that corresponds to the transmitted signal that was transmitted in a certain period and that is received in the period following the above period. do.

For example, as shown in FIG. 6(a), a part R( m,k)d is received in the next period k+1. A part _R (m , k)d is included.

This received signal part R(m,k)d is received and processed by the receiving unit for frequency band FC _m+1 , and in the transforming unit for frequency band FC _{m+ 1, the next cycle k+} 1 transmission signal of frequency band FC m+1 It is mixed with S(m+1, k+1) to generate the beginning portion of the beat signal Q(m+1, k+1) of the cycle k+1. The above "receiving unit for frequency band FC _m+1 " refers to receiving unit 132 if m=1, refers to receiving unit 133 if m=2, and refers to "transforming unit for frequency band FC _m+1". "Unit" refers to the transforming unit 142 when m=1, and refers to the transforming unit 143 when m=2.
In FIG. 6(b), such a starting end portion is indicated by the code Q(m, k)d, and the portion other than the starting end portion is indicated by the code Q(m+1, k+1)u.

In the case of a radar with a long maximum ranging distance, the maximum value of the delay time Td is long, and phase continuity between beat signals in the delay portion (period Td portion in FIG. 6A) is also important.

Phase Δθ (m, k) at the end of the cycle of the beat signal Q(m, k)u generated from the transmission signal S(m, k) and the reception signal R(m, k) of ^{the m-th frequency band in cycle k , m,k)} (kT) and the received signal R(m,k) corresponding to the transmitted signal S(m,k), received during period k+1, R(m,k)d , the phase Δθ ^{(m, k, m+1, k+1)} (kT ) is expressed by the following equation (10).

f _m +B/2 in equation (10) is equal to the center frequency h _m of the frequency band FC _m .
To ensure phase continuity between the two beat signals, the phase difference given by equation (10) must be an integral multiple of 2π.

For the phase difference given by equation (10) to be an integer multiple of 2π, the product of the center frequency h _m (=f _m +B/2) and the chirp period length T is an integer and the transmitted signal S The phase φ _{m ,k at the start of chirp of period k of m} and the phase φ _{m+1,k+1 of the transmission signal S m+1} at the start of chirp of period _k+1 should be equal to each other.

In order to continuously ensure phase continuity between the above beat signals, the phase difference given by equation (10) must be an integral multiple of 2π across all frequency bands and in all periods. There is
Therefore, as described above, the control device 100 sets the phases φ _1,k to φ _3,k to be the same in all the cycles, the modulation width B, the cycle length T, and the transmission signals S ₁ to S ₃ . By specifying the start frequencies f ₁ to f ₃ and the initial phases φ _1,k to φ _3,k of each period of the transmission signals S ₁ to S ₃ , the value of equation (10), that is, the beat signal Control is performed so that the phase difference at the start of the cycle is an integral multiple of 2π.

By performing such control, the continuity of the phase between the two beat signals can be continuously ensured, and the peak of the Fourier transform can be obtained even for a distant moving target with a long delay time of the received signal. High range resolution can be realized without causing distortion, splitting, etc.

Also, as described with reference to FIGS. 6(a) and 6(b), the portion of the received signal of the m-th frequency band FC _m that arrives after being delayed in the next chirp period is transferred to the adjacent (m+1)-th chirp period. Since it is necessary to receive in the frequency band FC _m+1 and convert it into a beat signal, the conversion unit corresponding to the frequency band FC _{m+1 in} the signal conversion device 140, as shown in FIG. In addition, it is necessary to be able to process signals in the frequency range FE _m+1 from the lower end of the frequency band FC _m+1 to the frequency lower by the frequency width Bd. The above-mentioned “conversion unit corresponding to frequency band FC _m+1 ” is a conversion unit that receives transmission signal S _{m+ 1} of frequency band FC m+1 and generates beat signal Q _m+ 1. , m is 2, it refers to the conversion unit 143 .

Furthermore, the receiving unit corresponding to the frequency band FC _m+1 in the signal receiving device 130 is configured so that the frequency range FE _{m+1 is} the receiving frequency band, and reception processing is possible for signals in the frequency range FE _m+1. There is a need. The above "receiving unit corresponding to frequency band FC _m+1 " is a receiving unit corresponding to the converting unit corresponding to frequency band FC _m+1 , and if m is 1, it refers to the receiving unit 132, and if m is 2, Refers to the receiving unit 133 .
In addition, it is sufficient for the receiving unit 131 corresponding to the frequency band FC1 to use the frequency band FC1 itself as the reception frequency band.
A certain frequency range or a certain frequency band "as a reception frequency band" means that signals within the frequency range or frequency band can be subjected to reception processing.
To distinguish from the reception frequency band, the frequency bands FC ₁ to FC ₃ are sometimes referred to as the transmission frequency band.

The frequency width Bd is predetermined to be equal to or higher than the maximum beat frequency Qmax.
The maximum beat frequency Qmax is given by Equation (11) below.

式（１１）で、τ_ｍａｘは、最大測距距離に相当する遅延時間である。

In Equation (11), τ _max is the delay time corresponding to the maximum ranging distance.

Furthermore, the product of the sampling frequency _fS of the beat signal in the A/D converters 81 to 83 and the length T of the chirp period may be an integer. In other words, the A/D converters 81-83 may be configured to perform sampling at a sampling frequency _fS that satisfies such conditions. By doing so, the phase difference at the cycle start time of the received signal in each frequency band obtained from the reflected wave from the target that is stationary or moving at a constant speed is constant in successive cycles.

A method of calculating the distance to the target TG and the speed of the target TG by the target detection unit 152 based on the plurality of synthesized signals CS generated as described above will be described below.

First, a first Fourier transform is performed on each of the synthesized signals CS to generate a power spectrum with respect to distance. An example of Fourier transform results for one composite signal is shown in FIG.
The horizontal axis in FIG. 7 represents the frequency corresponding to the distance, and the distance can be specified from the frequency _fp at which the power peaks.
A result (Fourier transform result) similar to that shown in FIG. 7 is obtained for each composite signal.

Fourier transform results DS(i), DS(i+1), DS(i+3), . Specifically, the result of each Fourier transform is arranged at the point corresponding to the beginning of the beat signal located at the beginning of the corresponding synthesized signal. The result of such an arrangement is shown in FIG. 8(a).
When the target TG is moving, the phase of the peak in the Fourier transform result shown in FIG. 8(a) changes as shown in FIG. 8(b).

Next, Fourier transform is performed for each frequency bin (BIN) of the frequency spectrums DS(i), DS(i+1), . . . shown in FIG. 8(a).

An example of the result of the second Fourier transform is shown in FIG.
As shown, in the result of the second Fourier transform, a peak appears in the frequency bin for the Doppler frequency. The speed of the target TG can be identified from this Doppler frequency.

FIG. 10 shows the procedure of processing after the radar device RD shown in FIG. 1 receives a reflected wave.
At step ST1, a beat signal is generated. The processing of step ST1 is performed by the signal conversion device 140 .
In step ST2, a synthesized signal is generated by concatenating the beat signals. The process of step ST2 is performed by the signal synthesizing section 151 .

In step ST3, each combined signal is Fourier transformed.
In step ST4, the results of the Fourier transform are arranged, and the Fourier transform is performed in the arranged direction.
At step ST5, the peak is detected and the distance and speed are obtained.
The processing of steps ST3 to ST5 is performed by the target detection section 152. FIG.

Various modifications can be added to the above embodiment.
For example, in the above embodiment, the number M of frequency bands is 3, but M may be 2 or 4 or more. In short, M should be 2 or more.
Also, in the above configuration, the chirp signal is an up chirp signal, but the chirp signal may be a down chirp signal.

Further, the above signal transmission device has a plurality of transmission units, and each transmission unit is composed of an amplifier, a transmission/reception switch, and an antenna. If a set of amplifiers, duplexers, and antennas can cover all of a plurality of frequency bands, such a set of amplifiers, duplexers, and antennas may constitute a signal transmission device.

Also, the above signal receiving apparatus has a plurality of receiving sections, each of which is composed of an antenna, a transmission/reception switch, and an amplifier. If a set of antennas, a duplexer, and an amplifier can cover all of a plurality of frequency bands, the signal receiver may be configured with such a set of antennas, a duplexer, and an amplifier.

Also, in the above embodiment, the modulation width B of the chirp signal is fixed. The modulation width B may be designated by the control device 100 . In that case, a DDS 3 capable of generating a chirp signal with a specified modulation width B may be used.

In short, radar equipment
Synchronizing the first to Mth chirp signals of the mutually adjacent first to Mth (M is an integer of 2 or more) transmission frequency bands having the same bandwidth and having continuous frequency changes every chirp cycle a signal generator (110) that repeatedly generates to
a signal transmission device (120) for transmitting first to Mth transmission waves corresponding to first to Mth chirp signals repeatedly generated by the signal generation device (110);
Reflected waves generated by reflection of the first to Mth transmission waves transmitted by the signal transmission device (120) at the target are first to first corresponding to the first to Mth transmission frequency bands, respectively. a signal receiving device (130) that receives signals in M reception frequency bands and generates first to M reception signals;
Distance to the target from the first to Mth chirp signals generated by the signal generation device (110) and the first to Mth reception signals generated by the signal reception device (130) a signal conversion device (140) for generating first to Mth beat signals having frequency components corresponding to
A signal synthesizing unit (151) for coupling the first to Mth beat signals generated by the signal conversion device (140) with each other at the boundaries between the chirp periods to generate one synthesized signal for each chirp period. )and,
A target detection unit (152) for calculating the distance to the target and the speed of the target from a plurality of synthesized signals sequentially generated by the signal synthesizing unit (151).

Preferably, the frequency of the mth chirp signal at the end of chirp is equal to the frequency of the m+1th chirp signal at the start of chirp.

Preferably, the phase of the m-th chirp signal at the end of chirp and the phase of the m+1-th chirp signal at the start of chirp are continuous.

The signal synthesizing unit (151) includes a termination of a beat signal generated from an m-th chirp signal (where m is any one from 1 to M−1) among the first to M-th chirp signals, It is preferable that the beat signal is connected by connecting a beat signal generated from the (m+1)th chirp signal.

If the chirp signal is an up-chirp signal, the beat signals in the first to Mth frequency bands FC ₁ to FC _M are preferably concatenated in ascending order of frequency in the corresponding frequency bands.
If the chirp signal is a down-chirp signal, the beat signals in the first to Mth frequency bands FC ₁ to FC _M are preferably concatenated in descending order of frequency in the corresponding frequency bands.

The product of the center frequency (h _m =f _m +B/2) of each of the first to M-th frequency bands and the chirp period length (T) is an integer, and the chirp of the first to M-th chirp signals Preferably, the starting phases (φ _m,k ) are equal to each other and identical to each other between successive chirp periods (k).

The n-th (n is any of 2 to M) reception frequency band among the first to M-th reception frequency bands extends the corresponding transmission frequency band by the beat frequency corresponding to the maximum ranging distance. It is preferable to have the frequency range

If the chirp signal is the up-chirp signal, the above extension is from the lower limit of the corresponding transmission frequency band to a frequency lower by the beat frequency corresponding to the maximum ranging distance, and the chirp signal is the down-chirp signal , the above extension is from the upper limit of the corresponding transmission frequency band to a frequency higher by the beat frequency corresponding to the maximum ranging distance.

The signal conversion device (140) has first to Mth A/D conversion units for A/D converting the first to Mth beat signals, respectively, and the first to Mth A/D In the conversion unit, the first to Mth A/D conversion is performed so that the product of the sampling frequency (f _S ) of the first to Mth beat signals and the length (T) of the chirp period is an integer. A part is configured, whereby the phase difference at the cycle start time of the received signal in each frequency band obtained from the reflected wave from the target that is stationary or moving at a constant speed is constant in continuous cycles. It is preferable to

A part or all of the parts other than the antenna of the above radar device may be configured by the processing circuit.
For example, the function of each part of the radar apparatus may be realized by a separate processing circuit, or the functions of a plurality of parts may be collectively realized by one processing circuit.
The processing circuitry may be implemented in hardware or in software, ie a programmed computer.
Some of the functions of each part of the radar apparatus may be realized by hardware, and other parts may be realized by software.

FIG. 11 shows the hardware configuration of a computer 90 that realizes a part or all of the functions of the parts other than the antenna of the radar device.
In the illustrated example, computer 90 has processor 91 and memory 92 .
The memory 92 stores a program for realizing the functions of the parts other than the antenna of the radar apparatus.

The processor 91 uses, for example, a CPU (Central Processing Unit), a microprocessor, a microcontroller, or a DSP (Digital Signal Processor).

The memory 92 is, for example, RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory) or EEPROM (Electrically Erasable Programmable Read On Memory). ly Memory), magnetic disks, optical disks, Alternatively, a magneto-optical disk or the like is used.

The processor 91 and the memory 92 may be realized by an LSI (Large Scale Integration) integrated with each other.

The processor 91 realizes the functions of the radar device by executing programs stored in the memory 92 .
The program may be provided through a network, or may be provided by being recorded on a recording medium, for example, a non-temporary recording medium. That is, the program may be provided as a program product, for example.

Although the computer of FIG. 11 includes a single processor, it may include two or more processors.

As described above, according to the radar apparatus of the embodiment, even for a moving target, phase continuity between beat signals can be ensured, and high range resolution can be achieved without causing distortion, splitting, etc. in the Fourier transform peak. can be realized.

3 DDS (Direct Digital Synthesis Oscillator) 4 High Frequency Signal Generator 11-13 Mixer 21-23 Amplifier 31-33 Transmit/Receive Switch 41-43 Antenna 51-53 Amplifier 61-63 Mixer 71-73 Amplifier 81-83 A/D converter 100 Control device 102 Reference signal generator 110 Signal generator 120 Signal transmitter 121-123 Transmitter 130 Signal receiver 131-133 Receiver 140 Signal Conversion device 141 to 143 conversion unit 150 signal processing unit 151 signal synthesizing unit 152 target detection unit.

Claims (9)

Synchronizing the first to Mth chirp signals of the mutually adjacent first to Mth (M is an integer of 2 or more) transmission frequency bands having the same bandwidth and having continuous frequency changes every chirp cycle a signal generator that repeatedly generates to
a signal transmission device for transmitting first to Mth transmission waves corresponding to first to Mth chirp signals repeatedly generated by the signal generation device;
first to Mth reception waves corresponding to the first to Mth transmission frequency bands, respectively a signal receiving device that receives signals in a frequency band and generates first to Mth received signals;
frequency components according to the distance to the target from the first to Mth chirp signals generated by the signal generation device and the first to Mth reception signals generated by the signal reception device; a signal conversion device for generating first to Mth beat signals having
a signal synthesizing unit that couples the first to Mth beat signals generated by the signal conversion device with each other at boundaries between the chirp periods to generate one synthesized signal for each chirp period;
A radar apparatus comprising: a target detection unit that calculates a distance to a target and a speed of the target from a plurality of synthesized signals sequentially generated by the signal synthesis unit. The signal synthesizing unit includes an end of a beat signal generated from an m-th chirp signal (where m is any one from 1 to M−1) among the first to M-th chirp signals, and an m+1-th chirp signal. 2. The radar apparatus according to claim 1, wherein the beat signal is connected by connecting a beat signal generated from the chirp signal. 3. The radar apparatus according to claim 2, wherein the frequency of the m-th chirp signal at the end of chirp is equal to the frequency of the m+1-th chirp signal at the start of chirp. 4. The radar apparatus according to claim 2, wherein the phase of the m-th chirp signal at the end of chirp and the phase of the m+1-th chirp signal at the start of chirp are continuous. 5. The radar system according to claim 2, wherein said chirp signal is an up-chirp signal. 5. The radar apparatus according to claim 2, wherein said chirp signal is a down chirp signal. the product of the center frequency of each of the first to M-th frequency bands and the length of the chirp period is an integer;
7. The radar apparatus according to any one of claims 1 to 6, wherein phases of the first to Mth chirp signals at the start of chirp are equal to each other and are the same in successive chirp periods. The n-th (n is any one of 2 to M) reception frequency band among the first to M-th reception frequency bands extends the corresponding transmission frequency band by a beat frequency corresponding to the maximum ranging distance. 8. A radar system according to any one of claims 1 to 7, having a frequency range. The signal conversion device is
having first to Mth A/D converters for A/D converting the first to Mth beat signals, respectively;
In the first to Mth A/D converters, the first to Mth A/D converters are arranged such that the product of the sampling frequency of the first to Mth beat signals and the length of the chirp period is an integer. The radar device according to any one of claims 1 to 8, further comprising a D conversion section.

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