JP6223230B2 - Radar apparatus and target detection method - Google Patents

Description

  The present invention relates to a radar apparatus and a target detection method for detecting a target by suppressing unnecessary interference waves.

In radar devices that detect targets, phased array antennas that can electronically control antenna radiation patterns are widely used.
The phased array antenna includes, for example, a plurality of element antennas, a plurality of phase shifters connected to the element antennas, and a phase shifter control device that controls the phase shifters.
In a phased array antenna, since it is not easy to freely control the excitation amplitude, usually only the excitation phase is controlled. In order to suppress unnecessary interference waves, it is necessary to reduce the side lobe level, but it has been difficult to sufficiently reduce the side lobe level only by controlling the excitation phase.

Non-Patent Document 1 and Patent Document 1 below disclose a time modulation array antenna that uses the concept of time weight as a technique for controlling the excitation amplitude of a phased array antenna.
This technique obtains the same effect (radiation characteristics) as a state where a predetermined amplitude distribution is equivalently given by time averaging (time integration) of signals received or transmitted in a plurality of excitation states.
In Non-Patent Document 1, the ON / OFF state of the switch is controlled to switch the excitation state in a time division manner. In Patent Literature 1, the phase shift amount of the phase shifter is controlled in a time division manner. The excitation state is switched.

JP 2013-219742 A (FIG. 1)

W. Kummer et al., Ultra-Low Sidelobes from Time-Modulated Arrays, IEEE Transactions on Antennas and Propagation, vol.11, iss.6, pp.633-639, 1963.

  Since the conventional radar apparatus is configured as described above, the excitation amplitude of the phased array antenna is controlled by switching the excitation state by controlling the ON / OFF of the switch and the phase shift amount of the phase shifter. be able to. However, in order to reduce the side lobe level in order to suppress unnecessary interference waves, the switch is turned ON / OFF or the phase shifter is shifted at short time intervals corresponding to the repetitive transmission cycle of the pulse signal (transmission signal). It is necessary to control the phase amount. However, since ON / OFF of the switch and control of the phase shift amount of the phase shifter are controlled by hardware, it is necessary to implement hardware capable of high-speed control. There was a problem that received restrictions on the implementation of.

  The present invention has been made to solve the above-described problems, and controls the excitation amplitude of the phased array antenna without implementing hardware capable of high-speed control of the phase shift amount of the phase shifter. An object of the present invention is to obtain a radar apparatus and a target detection method that can suppress unnecessary interference waves.

  The radar apparatus according to the present invention generates a first signal as a transmission signal, and generates a second signal having a complex conjugate relationship with the first signal, and the signal generation unit generates the second signal. Signal switching means for alternately outputting the first signal and the second signal, signal distribution means for distributing the first and second signals alternately output from the signal switching means to a plurality of signals, and signal distribution means A plurality of phase shifters that adjust the phase of the first and second signals distributed by the plurality of element antennas that radiate the first and second signals whose phases are adjusted by the phase shifter to the space; After the first signal is radiated from the element antenna, the first signal is incident on the first reflected signal reflected from the target, and after the second signal is radiated from the element antenna, the second signal is A receiver that receives the second reflected signal reflected by the target. A tenor, and a time averaging means for calculating a time average of a first conjugate signal incident from the receiving antenna and a complex conjugate signal of the second reflected signal incident from the receiving antenna are provided. The target is detected from the calculation result of the averaging means.

  According to the present invention, the first signal is generated as the transmission signal, the signal generating unit generates the second signal having a complex conjugate relationship with the first signal, and the first signal generated by the signal generating unit. Switching means for alternately outputting the first signal and the second signal, signal distribution means for distributing the first and second signals alternately output from the signal switching means to a plurality of signals, and distribution by the signal distribution means A plurality of phase shifters for adjusting the phases of the first and second signals generated; a plurality of element antennas for radiating the first and second signals whose phases are adjusted by the phase shifters; After the first signal is radiated from the first antenna, the first signal reflected by the target is incident on the first reflected signal. After the second signal is radiated from the element antenna, the second signal becomes the target. A receiving antenna that receives the reflected second reflected signal; A time averaging means for calculating a time average of the first reflected signal incident from the transmission antenna and the complex conjugate signal of the second reflected signal incident from the reception antenna is provided, and the target detection means Since the target is detected from the calculation result, the excitation amplitudes of the multiple element antennas constituting the phased array antenna can be obtained without implementing hardware capable of high-speed control such as the phase shift amount of the phase shifter. This has the effect of controlling and suppressing unnecessary interference waves.

It is a block diagram which shows the radar apparatus by Embodiment 1 of this invention. It is a flowchart which shows the processing content (target detection method) of the radar apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the signal waveform processed with the radar apparatus by Embodiment 1 of this invention. It is a block diagram which shows the radar apparatus by Embodiment 2 of this invention. It is a block diagram which shows the radar apparatus by Embodiment 3 of this invention. It is explanatory drawing which shows the example which arrangement | positioning of several element antenna has comprised the symmetrical form of the conjugate center.

Embodiment 1 FIG.
1 is a block diagram showing a radar apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a transmitter 1 includes a signal generation unit 2, a conjugate waveform conversion unit 3, a signal switching unit 4, and a frequency conversion unit 5, and generates a high frequency signal as a transmission signal (for example, a pulse signal). A high frequency signal is output to the phased array antenna 6.
The signal generation unit 2 generates a complex signal s ₁ (first signal) that is a radar wave used for target detection, and outputs the complex signal s ₁ to the conjugate waveform conversion unit 3 and the signal switching unit 4.
Conjugated waveform converting unit 3 by complex signal s ₁ conjugated waveform conversion outputted from the signal generator 2, generates a complex signal s _{2 (second} signal) in the complex signal s ₁ and the complex conjugate relationship Then, the complex signal s2 is output to the signal switching unit 4.
The signal generating unit 2 and the conjugate waveform converting unit 3 constitute a signal generating unit.

Implementation and the signal switching unit 4 complex signal s ₁ which is generated by the signal generation unit 2, a signal switching process of outputting a complex signal s ₂ generated by conjugation waveform converting unit 3 selects alternately the frequency converter 5 To do. The signal switching unit 4 constitutes a signal switching unit.
The frequency converter 5 converts the frequencies of the complex signals s ₁ and s ₂ that are alternately output from the signal switching unit 4 to generate a high-frequency signal s (n), and the high-frequency signal s (n) is converted to the phased array antenna 6. Output to.
s (n) = s ₁ , s ₂ , s ₁ , s ₂ ,..., s ₁ , s ₂

The phased array antenna 6 is composed of a combiner / distributor 7, phase shifters 8-1 to 8-K, and element antennas 9-1 to 9-K, and receives a high-frequency signal s (n) output from the transmitter 1. Radiates into space.
The synthesizer / distributor 7 equally distributes the power of the high-frequency signal s (n) output from the transmitter 1 to K pieces, and the distributed high-frequency signal s (n) is phase shifters 8-1 to 8-K. Output to. The synthesizer / distributor 7 constitutes a signal distributor.

The phase shifters 8-1 to 8-K adjust the phase of the high-frequency signal s (n) distributed by the combiner / distributor 7 under the control of the phase shifter control unit 11, and the high-frequency signal s after the phase adjustment. (N) is output to the element antennas 9-1 to 9-K.
The element antennas 9-1 to 9-K radiate the phase-adjusted high-frequency signal s (n) output from the phase shifters 8-1 to 8-K to the space.

The excitation phase setting unit 10 is a setting unit that sets the excitation phase β _k (k = 1, 2,..., K) of the element antennas 9-1 to 9-K necessary for realizing a desired radiation pattern.
The phase shifter control unit 11 is a control device that controls the amount of phase shift of the phase shifters 8-1 to 8 -K according to the excitation phase β _k set by the excitation phase setting unit 10.
In the first embodiment, since the amount of phase shift of the phase shifters 8-1 to 8-K is not controlled for the purpose of controlling the excitation amplitude of the phased array antenna 6, the signal switching unit 4 of the transmitter 1 is used. Even when the complex signal s is switched, the phase shift amounts of the phase shifters 8-1 to 8-K are fixed to the same phase shift amount, which is short corresponding to the repeated transmission cycle of the pulse signal (transmission signal). It is not necessary to control the amount of phase shift of the phase shifters 8-1 to 8-K at time intervals.
Therefore, it is not necessary to mount hardware capable of controlling the phase shift amount of the phase shifters 8-1 to 8-K at high speed.

The receiving antenna 21 is arranged at a position different from the phased array antenna 6. After the high frequency signal s (n) is radiated from the phased array antenna 6, the reflected signal x is reflected from the high frequency signal s (n) to the target. (N) is incident. That is, the high-frequency signal reflection signal (first reflection signal) generated from the complex signal s ₁ and the high-frequency signal reflection signal (second reflection signal) generated from the complex signal s ₂ are alternately incident.
The reception antenna 21 may be a phased array antenna or a single antenna.
The receiver 22 detects the reflected signal x (n) incident from the receiving antenna 21 and converts the reflected signal x (n) into a signal (for example, a baseband digital signal (complex signal)) used for subsequent signal processing. To do.
In the first embodiment, it is assumed that the complex signal x ₁ corresponding to the complex signal s ₁ and the complex signal x ₂ corresponding to the complex signal s ₂ are alternately output from the receiver 22.
x (n) = x ₁ , x ₂ , x ₁ , x ₂ ,..., x ₁ , x ₂

The time average processing unit 23 is constituted by, for example, a semiconductor integrated circuit on which a CPU is mounted or a one-chip microcomputer. When the complex signal x ₁ and the complex signal x ₂ are alternately received from the receiver 22, the complex is obtained. by the signal x ₂ conjugated waveform conversion, generates a complex signal x ₂ ^* in the complex signal x ₂ and the complex conjugate relationship, and calculates the time average of its complex signal x ₁ and the complex signal x ₂ ^* Implement the process. The time average processing unit 23 constitutes a time average means.
The signal processing unit 24 is composed of, for example, a semiconductor integrated circuit on which a CPU is mounted, a one-chip microcomputer, or the like. Processing for detecting a target from a calculation result of the time average processing unit 23, processing for tracking a target, or the like To implement. The signal processing unit 24 constitutes a target detection unit.
FIG. 2 is a flowchart showing the processing contents (target detection method) of the radar apparatus according to Embodiment 1 of the present invention.
FIG. 3 is an explanatory diagram showing signal waveforms processed by the radar apparatus according to Embodiment 1 of the present invention.

Next, the operation will be described.
First, the excitation phase setting unit 10 sets the excitation phases β _k (k = 1, 2,..., K) of the element antennas 9-1 to 9-K necessary for realizing a desired radiation pattern. (Step ST1).
When the excitation phase setting unit 10 sets the excitation phase β _k , the phase shifter control unit 11 sets the phase shift amount of the phase shifters 8-1 to 8-K according to the excitation phase β _k .
In the first embodiment, since it is assumed that the excitation phase β _k is a fixed value that does not change in time division, it is necessary to control the phase shift amount of the phase shifters 8-1 to 8-K at high speed. There is no.
In the first embodiment, as described above, it is assumed that the excitation phase β _k is a fixed value. However, there are M (2 × M) sets of two complex signals having a complex conjugate relationship. It is assumed that the interference wave is suppressed by accumulating and taking the time average of 2 × M complex signals, so that M excitation phases β _k may be set.
When setting the M excitation phase beta _k, it is necessary to control in a time division amount of phase shift of the phase shifter 8-1 to 8-K, the period for switching the complex signal s ₁ and the complex signal s ₂ Since switching may be performed at twice the cycle, the control speed is slower than the conventional example.

Signal generating unit 2 of the transmitter 1 generates a complex signal s ₁ is a radar wave used for target detection, and outputs the complex signal s ₁ to conjugate the waveform converting unit 3 and the signal switching unit 4 (step ST2).
Conjugated waveform converting unit 3 receives the complex signal s ₁ from the signal generating unit 2, by the complex signal s ₁ conjugate waveform converting the complex signal s ₂ in the complex signal s ₁ and the complex conjugate relationship generated, and outputs the complex signal _{s 2} to the signal switching unit 4 (step ST3).
s ₂ = s ₁ ^* (1)
In the formula (1), * is a symbol indicating a complex conjugate.
If the phase component of the complex signal s ₁ is φ, the phase component of the complex signal s ₂ is −φ.

Signal switching unit 4, the complex signal s ₁ which is generated by the signal generation unit 2, a signal switching process of outputting a complex signal s ₂ generated by conjugation waveform converting unit 3 selects alternately the frequency converter 5 Implement (step ST4).
Therefore, complex signals are output from the signal switching unit 4 to the frequency conversion unit 5 in the order of s ₁ → s ₂ → s ₁ → s ₂ → s ₁ → s ₂ →.
When the frequency conversion unit 5 receives the complex signals s ₁ and s ₂ from the signal switching unit 4, for example, the frequency conversion unit 5 performs D / A conversion on the complex signals s ₁ and s ₂ , and then up-converts the frequency so A signal s (n) is generated, and the high-frequency signal s (n) is output to the phased array antenna 6.
s (n) = s ₁ , s ₂ , s ₁ , s ₂ ,..., s ₁ , s ₂ (2)
S ₁ and s _{2 on} the right side of Expression (2) are complex signals (high-frequency signals) after frequency conversion.

When the combiner / distributor 7 of the phased array antenna 6 receives the high-frequency signal s (n) from the transmitter 1, the power of the high-frequency signal s (n) is evenly distributed to K pieces, and the distributed high-frequency signal s is distributed. (N) is output to the phase shifters 8-1 to 8-K.
The phase shifters 8-1 to 8-K adjust the phase of the high-frequency signal s (n) distributed by the synthesis distributor 7 under the control of the phase shifter control unit 11, and the high-frequency signal after the phase adjustment. s (n) is output to the element antennas 9-1 to 9-K.
Thereby, as shown in FIG. 3A, the high-frequency signal s (n) after phase adjustment is radiated into the space from the element antennas 9-1 to 9-K (step ST5).

As shown in FIG. 3B, the receiving antenna 21 radiates a high-frequency signal s (n) from the phased array antenna 6, and then reflects the high-frequency signal s (n) reflected to the target. ) Is incident (step ST6).
That is, the receiving antenna 21 receives the reflected signal (first reflected signal) of the high frequency signal generated from the complex signal s ₁ and the reflected signal (second reflected signal) of the high frequency signal generated from the complex signal s _2. Incident alternately.
The receiver 22 detects the reflected signal x (n) incident from the receiving antenna 21 and, for example, down-converts the frequency of the reflected signal x (n), and then performs A / D conversion to thereby convert the baseband signal. The digital signal (complex signal) is output to the time average processing unit 23.
In the first embodiment, a complex signal x ₁ corresponding to the complex signal s ₁ and a complex signal x ₂ corresponding to the complex signal s ₂ are alternately output from the receiver 22.
x (n) = x ₁ , x ₂ , x ₁ , x ₂ ,..., x ₁ , x ₂ (3)
X ₁ and x _{2 on} the right side of Equation (3) are complex signals (reflected signals) after frequency conversion.

When receiving the complex signal x ₁ corresponding to the complex signal s ₁ from the receiver 22, the time average processing unit 23 stores the complex signal x ₁ in a memory (not shown) (step ST7).
The time average processing unit 23, the receiver 22 receives a complex signal x ₂ that corresponds to the complex signal s _2, the complex signal x ₂ by conjugation waveform conversion, the complex signal x ₂ and the complex conjugate The related complex signal x ₂ ^* is generated, and the complex signal x ₂ ^* is stored in a memory (not shown) (step ST7).

The processes of steps ST4 to ST7 are repeatedly performed until M sets of complex signals x ₁ and x ₂ ^* (2 × M complex signals x) are accumulated, and M sets of complex signals x ₁ and x ₂ ^* are accumulated. Then, the process proceeds to step ST9 (step ST8).
The time average processing unit 23 calculates a time average (time integration) of the M sets of complex signals x ₁ and x ₂ ^* stored in a memory (not shown) (step ST9).
Time average = ((x ₁ + x ₂ ^* ) + (x ₁ + x ₂ ^* ) +... + (X ₁ + x ₂ ^* )) / 2M (4)
The signal processing unit 24 performs processing for detecting a target from the calculation result of the time average processing unit 23, processing for tracking the target, and the like.
Since the target detection process and the tracking process itself are known techniques, a detailed description thereof will be omitted.

As is apparent from the above, according to the first embodiment, on the transmission side, the signal switching unit 4 performs the complex signal s ₁ generated by the signal generation unit 2 and the complex signal s ₁ generated by the conjugate waveform conversion unit 3. By alternately selecting the signal s ₂ and outputting it to the frequency converter 5, two high-frequency signals having a complex conjugate relationship are alternately radiated to the space, while the reception side has a complex corresponding to the complex signal s _1. the signal _{x 1,} the complex signals _x ^{2 *} in a relationship of complex signals _{x 2} and the complex conjugate corresponding to the complex signal _{s 2} and M sets accumulate, M sets of complex signals _{x 1, x} ^{2 *} time average Therefore, the element antenna 9-1 constituting the phased array antenna 6 can be implemented without mounting hardware capable of high-speed control of the phase shift amount of the phase shifters 8-1 to 8-K. By controlling the excitation amplitude of ~ 9-K, unwanted interference wave An effect that can be pressed.

In the first embodiment, the high frequency signal s (n) radiated from the phased array antenna 6 is a pulse signal. However, the high frequency signal s (n) radiated from the phased array antenna 6 is a pulse signal. It is not limited to such an intermittent signal, but may be a continuous signal.
When a continuous signal is radiated from the phased array antenna 6, a part of the continuous signal reflected by the target may be received on the receiving side. Further, an average time shorter than the signal period may be calculated by processing delay or the like.

  In the first embodiment, an example in which there is one phased array antenna 6 is shown, but a plurality of phased array antennas 6 arranged at different locations are synchronized to generate a high-frequency signal s (n) as a space. A multi-static radar that emits light may be configured.

Embodiment 2. FIG.
FIG. 4 is a block diagram showing a radar apparatus according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG.
The transmission antenna 31 radiates the high-frequency signal s (n) output from the transmitter 1 to the space. The transmission antenna 31 may be a phased array antenna or a single antenna. .

The phased array antenna 32 includes element antennas 33-1 to 33-K, phase shifters 34-1 to 34-K, and a combiner / distributor 35, and is disposed at a position different from the transmission antenna 31.
The element antennas 33-1 to 33-K of the phased array antenna 32 receive the high-frequency signal s (n) from the transmission antenna 31, and then reflect the high-frequency signal s (n) to the target. Is incident. That is, the high-frequency signal reflection signal (first reflection signal) generated from the complex signal s ₁ and the high-frequency signal reflection signal (second reflection signal) generated from the complex signal s ₂ are alternately incident.

The phase shifters 34-1 to 34-K adjust the phase of the reflected signal x (n) incident from the element antennas 33-1 to 33-K under the control of the phase shifter control unit 11, and adjust the phase. The subsequent reflected signal x (n) is output to the combiner / distributor 35.
The combiner / distributor 35 combines the reflected signals x (n) after the phase adjustment by the phase shifters 34-1 to 34-K, and outputs the combined signal to the receiver 22. That is, a plurality of first reflected signals whose phases are adjusted by the phase shifters 34-1 to 34-K are combined and the first combined signal is output to the receiver 22, and the phase shifters 34-1 to 34 are output. A plurality of second reflected signals whose phases are adjusted by −K are combined, and the second combined signal is output to the receiver 22. The combiner / distributor 35 constitutes a signal combiner.
The flowchart showing the processing contents of the radar apparatus of the second embodiment is the same as the flowchart of FIG. 2 in the first embodiment.

Next, the operation will be described.
First, the excitation phase setting unit 10 sets the excitation phase β _k (k = 1, 2,..., K) of the element antennas 33-1 to 33-K necessary for realizing a desired radiation pattern. (Step ST1).
When the excitation phase setting unit 10 sets the excitation phase β _k , the phase shifter control unit 11 sets the phase shift amount of the phase shifters 34-1 to 34-K according to the excitation phase β _k .
In the second embodiment, since it is assumed that the excitation phase β _k is a fixed value that does not change in a time division manner, it is necessary to control the phase shift amount of the phase shifters 34-1 to 34-K at high speed. There is no.
In the second embodiment, M excitation phases _βk may be set as in the first embodiment.

Similar to the first embodiment, the signal generator 2 of the transmitter 1 generates a complex signal s ₁ that is a radar wave used for target detection, and the complex signal s ₁ is converted into a conjugate waveform converter 3 and a signal switching unit. 4 (step ST2).
Conjugated waveform converting unit 3, when the signal generating unit 2 receives the complex signal s _1, as in the first embodiment, by the complex signal s ₁ conjugate waveform conversion, the complex signal s ₁ and the complex conjugate The complex signal s ₂ having the relationship is generated, and the complex signal s ₂ is output to the signal switching unit 4 (step ST3).

Signal switching unit 4, as in the first embodiment, the complex signal s ₁ which is generated by the signal generator 2, selects and frequency-converts the complex signal s ₂ generated by conjugation waveform converting unit 3 alternately A signal switching process for outputting to the unit 5 is performed (step ST4).
Therefore, complex signals are output from the signal switching unit 4 to the frequency conversion unit 5 in the order of s ₁ → s ₂ → s ₁ → s ₂ → s ₁ → s ₂ →.
When the frequency conversion unit 5 receives the complex signals s ₁ and s ₂ from the signal switching unit 4, for example, the frequency conversion unit 5 performs D / A conversion on the complex signals s ₁ and s ₂ , and then up-converts the frequency to thereby generate a high frequency signal. A signal s (n) is generated, and the high-frequency signal s (n) is output to the transmission antenna 31.
Thereby, as shown to Fig.3 (a), the high frequency signal s (n) is radiated | emitted to space from the transmission antenna 31 (step ST5).

As shown in FIG. 3B, the element antennas 33-1 to 33-K of the phased array antenna 32 receive the high-frequency signal s (n) from the transmission antenna 31 and then the high-frequency signal s (n) The reflected signal x (n) reflected by the target is incident (step ST6).
That is, the antenna elements 33-1 to 33-K includes a reflection signal of the high frequency signal generated from the complex signal s ₁ (first reflected signal), the reflected signal of the high frequency signal generated from the complex signal s ₂ (second 2 reflected signals) are incident alternately.
The phase shifters 34-1 to 34-K adjust the phase of the reflected signal x (n) incident from the element antennas 33-1 to 33-K under the control of the phase shifter control unit 11, and The adjusted reflection signal x (n) is output to the combiner / distributor 35.

When the combiner / distributor 35 receives the phase-adjusted reflection signal x (n) from the phase shifters 34-1 to 34-K, the combiner / distributor 35 combines the phase-adjusted reflection signal x (n). Output to the receiver 22.
That is, when the combiner / distributor 35 receives the first reflected signal from the phase shifters 34-1 to 34-K, the combiner / distributor 35 combines the plurality of first reflected signals and outputs the first combined signal to the receiver 22. Then, when the second reflected signal is received from the phase shifters 34-1 to 34-K, the plurality of second reflected signals are combined and the second combined signal is output to the receiver 22.

When the receiver 22 receives the combined signal from the combiner / distributor 35, the receiver 22 detects the combined signal, for example, down-converts the frequency of the combined signal, and then performs A / D conversion to thereby generate a baseband digital signal. (Complex signal) is output to the time average processing unit 23.
In the second embodiment, the complex signal x ₁ from the receiver 22 is obtained from the first combined signal _(complex signal x ₁ corresponding to the complex signal s _1), the complex signals x ₂ obtained by the second synthesis signal (Complex signal x ₂ corresponding to complex signal s ₂ ) are alternately output.

When the time average processing unit 23 receives the complex signal x ₁ corresponding to the complex signal s ₁ from the receiver 22, the time average processing unit 23 stores the complex signal x ₁ in a memory (not shown) as in the first embodiment (Step S 1). ST7).
When the time average processing unit 23 receives the complex signal x ₂ corresponding to the complex signal s ₂ from the receiver 22, as in the first embodiment, the time average processing unit 23 performs conjugate waveform conversion on the complex signal x ₂ . A complex signal x ₂ ^* having a complex conjugate relationship with the complex signal x ₂ is generated, and the complex signal x ₂ ^* is stored in a memory (not shown) (step ST7).

The processes of steps ST4 to ST7 are repeatedly performed until M sets of complex signals x ₁ and x ₂ ^* (2 × M complex signals x) are accumulated, and M sets of complex signals x ₁ and x ₂ ^* are accumulated. Then, the process proceeds to step ST9 (step ST8).
Similar to the first embodiment, the time average processing unit 23 calculates the time average (time integration) of the M sets of complex signals x ₁ and x ₂ ^* stored in a memory (not shown) (step ST9). .
Time average = ((x ₁ + x ₂ ^* ) + (x ₁ + x ₂ ^* ) +... + (X ₁ + x ₂ ^* )) / 2M (5)
As in the first embodiment, the signal processing unit 24 performs processing for detecting a target from the calculation result of the time average processing unit 23, processing for tracking the target, and the like.

As is apparent from the above, according to the second embodiment, on the transmission side, the signal switching unit 4 performs the complex signal s ₁ generated by the signal generation unit 2 and the complex signal s ₁ generated by the conjugate waveform conversion unit 3. By alternately selecting the signal s ₂ and outputting it to the frequency converter 5, two high-frequency signals having a complex conjugate relationship are alternately radiated to the space, while the reception side has a complex corresponding to the complex signal s _1. the signal _{x 1,} the complex signals _x ^{2 *} in a relationship of complex signals _{x 2} and the complex conjugate corresponding to the complex signal _{s 2} and M sets accumulate, M sets of complex signals _{x 1, x} ^{2 *} time average Therefore, the element antenna 33-1 constituting the phased array antenna 32 can be obtained without mounting hardware capable of high-speed control of the phase shift amount of the phase shifters 34-1 to 34-K. Unnecessary by controlling the excitation amplitude of ~ 33-K An effect that it is possible to suppress interference waves.

Embodiment 3 FIG.
FIG. 5 is a block diagram showing a radar apparatus according to Embodiment 3 of the present invention. In the figure, the same reference numerals as those in FIG.
The phased array antenna 40 is composed of a combiner / distributor 41, phase shifters 42-1 to 42-K and element antennas 43-1 to 43-K. The phased array antenna 40 receives the high frequency signal s (n) output from the transmitter 1. While radiating into the space, the reflected signal x (n) whose high-frequency signal s (n) is reflected by the target is incident.

The synthesizer / distributor 41 distributes the power of the high-frequency signal s (n) output from the transmitter 1 evenly to K pieces, and the distributed high-frequency signal s (n) is phase shifters 42-1 to 42-K. Output to.
The combiner / distributor 41 combines the reflected signals x (n) after the phase adjustment by the phase shifters 42-1 to 42-K, and outputs the combined signal to the receiver 22. That is, a plurality of first reflected signals whose phases are adjusted by the phase shifters 42-1 to 42-K are combined and the first combined signal is output to the receiver 22, and the phase shifters 42-1 to 42 are output. A plurality of second reflected signals whose phases are adjusted by −K are combined, and the second combined signal is output to the receiver 22.
Note that the combiner / distributor 41 constitutes a signal distributor and a signal combiner.

The phase shifters 42-1 to 42-K adjust the phase of the high-frequency signal s (n) distributed by the combiner / distributor 41 under the control of the phase shifter control unit 11, and the high-frequency signal s after phase adjustment. (N) is output to the element antennas 43-1 to 43-K.
The phase shifters 42-1 to 42-K adjust the phase of the reflected signal x (n) incident from the element antennas 43-1 to 43-K under the control of the phase shifter control unit 11, The reflected signal x (n) after phase adjustment is output to the combiner / distributor 41.

The element antennas 43-1 to 43-K radiate the phase-adjusted high-frequency signal s (n) output from the phase shifters 42-1 to 42-K to the space, while the high-frequency signal s (n) is the target. Is reflected by the reflected signal x (n). That is, the high-frequency signal reflection signal (first reflection signal) generated from the complex signal s ₁ and the high-frequency signal reflection signal (second reflection signal) generated from the complex signal s ₂ are alternately incident.
The flowchart showing the processing contents of the radar apparatus according to the third embodiment is the same as the flowchart of FIG. 2 in the first embodiment.

Next, the operation will be described.
First, the excitation phase setting unit 10 sets the excitation phases β _k (k = 1, 2,..., K) of the element antennas 43-1 to 43-K necessary for realizing a desired radiation pattern. (Step ST1).
When the excitation phase setting unit 10 sets the excitation phase β _k , the phase shifter control unit 11 sets the phase shift amount of the phase shifters 42-1 to 42-K according to the excitation phase β _k .
In the third embodiment, since it is assumed that the excitation phase β _k is a fixed value that does not change in time division, it is necessary to control the phase shift amount of the phase shifters 42-1 to 42-K at high speed. There is no.
In the third embodiment, M excitation phases _βk may be set as in the first embodiment.

Similar to the first embodiment, the signal generator 2 of the transmitter 1 generates a complex signal s ₁ that is a radar wave used for target detection, and the complex signal s ₁ is converted into a conjugate waveform converter 3 and a signal switching unit. 4 (step ST2).
Conjugated waveform converting unit 3, when the signal generating unit 2 receives the complex signal s _1, as in the first embodiment, by the complex signal s ₁ conjugate waveform conversion, the complex signal s ₁ and the complex conjugate The complex signal s ₂ having the relationship is generated, and the complex signal s ₂ is output to the signal switching unit 4 (step ST3).

Signal switching unit 4, as in the first embodiment, the complex signal s ₁ which is generated by the signal generator 2, selects and frequency-converts the complex signal s ₂ generated by conjugation waveform converting unit 3 alternately A signal switching process for outputting to the unit 5 is performed (step ST4).
Therefore, complex signals are output from the signal switching unit 4 to the frequency conversion unit 5 in the order of s ₁ → s ₂ → s ₁ → s ₂ → s ₁ → s ₂ →.
When the frequency conversion unit 5 receives the complex signals s ₁ and s ₂ from the signal switching unit 4, for example, the frequency conversion unit 5 performs D / A conversion on the complex signals s ₁ and s ₂ , and then up-converts the frequency to thereby generate a high frequency signal. A signal s (n) is generated, and the high-frequency signal s (n) is output to the phased array antenna 40.

When the combiner / distributor 41 of the phased array antenna 40 receives the high-frequency signal s (n) from the transmitter 1, the power of the high-frequency signal s (n) is evenly distributed to K pieces, and the distributed high-frequency signal s (N) is output to the phase shifters 42-1 to 42-K.
The phase shifters 42-1 to 42-K adjust the phase of the high-frequency signal s (n) distributed by the combiner / distributor 41 under the control of the phase shifter control unit 11, and the high-frequency signal after the phase adjustment. s (n) is output to the element antennas 43-1 to 43-K.
As a result, as shown in FIG. 3A, the phase-adjusted high-frequency signal s (n) is radiated into the space from the element antennas 43-1 to 43-K (step ST5).

As shown in FIG. 3B, the element antennas 43-1 to 43-K radiate the phase-adjusted high-frequency signal s (n) to the space, and then the high-frequency signal s (n) is reflected to the target. The reflected signal x (n) is incident (step ST6).
That is, the antenna elements 43-1 to 43-K includes a reflection signal of the high frequency signal generated from the complex signal s ₁ (first reflected signal), the reflected signal of the high frequency signal generated from the complex signal s ₂ (second 2 reflected signals) are incident alternately.
The phase shifters 42-1 to 42-K adjust the phase of the reflected signal x (n) incident from the element antennas 43-1 to 43-K under the control of the phase shifter control unit 11, and The adjusted reflection signal x (n) is output to the combiner / distributor 41.

When the combiner / distributor 41 receives the phase-adjusted reflection signal x (n) from the phase shifters 42-1 to 42-K, the combiner / distributor 41 synthesizes the phase-adjusted reflection signal x (n). Output to the receiver 22.
That is, when the combiner / distributor 41 receives the first reflected signal from the phase shifters 42-1 to 42-K, the combiner / distributor 41 combines the plurality of first reflected signals and outputs the first combined signal to the receiver 22. When the second reflected signals are received from the phase shifters 42-1 to 42-K, the plurality of second reflected signals are combined and the second combined signal is output to the receiver 22.

When receiving the combined signal from the combiner / distributor 41, the receiver 22 detects the combined signal, down-converts the frequency of the combined signal, and performs A / D conversion, as in the second embodiment. Then, the baseband digital signal (complex signal) is output to the time average processing unit 23.
In the third embodiment, a complex signal x ₁ from the receiver 22 is obtained from the first combined signal _(complex signal x ₁ corresponding to the complex signal s _1), the complex signals x ₂ obtained by the second synthesis signal (Complex signal x ₂ corresponding to complex signal s ₂ ) are alternately output.

When the time average processing unit 23 receives the complex signal x ₁ corresponding to the complex signal s ₁ from the receiver 22, the time average processing unit 23 stores the complex signal x ₁ in a memory (not shown) as in the first embodiment (Step S 1). ST7).
When the time average processing unit 23 receives the complex signal x ₂ corresponding to the complex signal s ₂ from the receiver 22, as in the first embodiment, the time average processing unit 23 performs conjugate waveform conversion on the complex signal x ₂ . A complex signal x ₂ ^* having a complex conjugate relationship with the complex signal x ₂ is generated, and the complex signal x ₂ ^* is stored in a memory (not shown) (step ST7).

The processes of steps ST4 to ST7 are repeatedly performed until M sets of complex signals x ₁ and x ₂ ^* (2 × M complex signals x) are accumulated, and M sets of complex signals x ₁ and x ₂ ^* are accumulated. Then, the process proceeds to step ST9 (step ST8).
Similar to the first embodiment, the time average processing unit 23 calculates the time average (time integration) of the M sets of complex signals x ₁ and x ₂ ^* stored in a memory (not shown) (step ST9). .
As in the first embodiment, the signal processing unit 24 performs processing for detecting a target from the calculation result of the time average processing unit 23, processing for tracking the target, and the like.

As is apparent from the above, according to the third embodiment, on the transmission side, the signal switching unit 4 performs the complex signal s ₁ generated by the signal generation unit 2 and the complex signal s ₁ generated by the conjugate waveform conversion unit 3. By alternately selecting the signal s ₂ and outputting it to the frequency converter 5, two high-frequency signals having a complex conjugate relationship are alternately radiated to the space, while the reception side has a complex corresponding to the complex signal s _1. the signal _{x 1,} the complex signals _x ^{2 *} in a relationship of complex signals _{x 2} and the complex conjugate corresponding to the complex signal _{s 2} and M sets accumulate, M sets of complex signals _{x 1, x} ^{2 *} time average Therefore, the element antenna 43-1 constituting the phased array antenna 40 can be obtained without mounting hardware capable of high-speed control of the phase shift amount of the phase shifters 42-1 to 42-K. Unnecessary by controlling the excitation amplitude of ~ 43-K An effect that it is possible to suppress interference waves.

Embodiment 4 FIG.
In the first to third embodiments, the arrangement of the element antennas 9-1 to 9-K, 33-1 to 33-K, and 43-1 to 43-K constituting the phased array antennas 6, 32, and 40 is particularly great. Although not mentioned, in the fourth embodiment, the arrangement of the element antennas 9-1 to 9-K, 33-1 to 33-K, and 43-1 to 43-K forms a symmetrical shape of the conjugate center. It shall be.
As the arrangement of the element antennas 9-1 to 9-K, 33-1 to 33-K, and 43-1 to 43-K that are symmetrical with respect to the conjugate center, those arranged at equal intervals on a straight line, etc. The thing arrange | positioned by the square arrangement | sequence of an interval can be considered.

FIG. 6 is an explanatory view showing an example in which the arrangement of a plurality of element antennas is symmetrical with respect to the conjugate center. In particular, FIG. 6A shows a plurality of element antennas arranged on a straight line at equal intervals. An example is shown, and FIG. 6B shows an example in which a plurality of element antennas are arranged in an equally spaced square array.
For example, the operation of the phased array antenna 6 when the element antennas 9-1 to 9-K in FIG. 1 are arranged on a straight line at equal intervals will be described. It is assumed that the element antennas 9-1 to 9-K have an even number of elements.

Assuming that the number of elements of the element antennas 9-1 to 9-K is K, the element interval is d, the wavelength of the high frequency signal s (n) is λ, and the radiation direction of the high frequency signal s (n) is θ. A direction vector a which is a phase difference vector between elements at −1 to 9-K is expressed as the following Expression (6).

At this time, when the excitation phase β _k is set symmetrically by the excitation phase setting unit 10, the weight vector W that is the excitation phase vector of the phase shifters 8-1 to 8 -K is expressed by the following equation (7). It is expressed as follows.

When a high-frequency signal generated from the complex signal s ₁ generated by the signal generation unit 2 is represented by s, the signal y ₁ radiated from the phased array antenna 6 is represented by the following equation (8). However, effects such as propagation path and noise are ignored.

Further, when a high-frequency signal generated from the complex signal s ₂ having a complex conjugate relationship with the complex signal s ₁ generated by the signal generator ₂ is represented by s ^* , the signal y ₂ radiated from the phased array antenna 6 is Is expressed as the following equation (9). However, effects such as propagation path and noise are ignored.

Next, paying attention to the structure of the direction vector a in the antenna arrangement that is symmetric with respect to the conjugate center, the relationship of the following expression (10) is satisfied.

For this reason, Formula (9) can be transformed into the following Formula (11).

In the receiving side, a signal y ₁ emitted from the phased array antenna 6, taking the average of the conjugate signal y ₂ ^* signal y ₂ emitted from the phased array antenna 6, the signal y ₃ times the average later, It is expressed as the following formula (12).

As is clear from the equation (12), the signal y ₃ radiated from the phased array antenna 6 obtained after time averaging is equivalent to that received with the excitation amplitude distribution that can be expressed by the real part of the weight vector W.
That is, even if the phase shift state is not switched by the phase shifters 8-1 to 8 -K, the angle formed by the real part (0 degree) is the fixed excitation phase β of the phase shifters 8-1 to 8 -K. A low sidelobe characteristic can be obtained just by setting in advance, as in the case of a conventional time-modulated array antenna.
Therefore, according to the fourth embodiment, by making the element antenna arrangement and the excitation phase symmetrical, it is possible to implement hardware for switching the phase shift amount of the phase shifters 8-1 to 8-K at high speed. Therefore, it is possible to realize a radar apparatus that can reduce the side lobe of the antenna radiation pattern.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 transmitter, 2 signal generator (signal generator), 3 conjugate waveform converter (signal generator), 4 signal switcher (signal switcher), 5 frequency converter, 6 phased array antenna, 7 combining distributor ( Signal distribution means), 8-1 to 8-K phase shifter, 9-1 to 9-K element antenna, 10 excitation phase setting unit, 11 phase shifter control unit, 21 receiving antenna, 22 receiver, 23 time average Processing unit (time averaging unit), 24 signal processing unit (target detection unit), 31 transmitting antenna, 32 phased array antenna, 33-1 to 33-K element antenna, 34-1 to 34-K phase shifter, 35 synthesis Distributor (signal combiner), 40 phased array antenna, 41 combiner distributor (signal distributor, signal combiner), 42-1 to 42-K phase shifter, 43-1 to 43-K element antenna

Claims (9)

A signal generating means for generating a first signal as a transmission signal and generating a second signal in a complex conjugate relationship with the first signal;
Signal switching means for alternately outputting the first signal and the second signal generated by the signal generating means;
Signal distribution means for distributing the first and second signals alternately output from the signal switching means to a plurality of signals;
A plurality of phase shifters for adjusting the phases of the first and second signals distributed by the signal distribution means;
A plurality of element antennas that radiate the first and second signals, the phases of which are adjusted by the phase shifter, into space;
After the first signal is radiated from the element antenna, the first reflected signal is reflected by the target, and after the second signal is radiated from the element antenna, the first signal is radiated. A receiving antenna that receives a second reflected signal in which two signals are reflected from the target;
Time averaging means for calculating a time average of the first reflected signal incident from the receiving antenna and the complex conjugate signal of the second reflected signal incident from the receiving antenna;
A radar apparatus comprising: target detection means for detecting the target from the calculation result of the time averaging means. A signal generating means for generating a first signal as a transmission signal and generating a second signal in a complex conjugate relationship with the first signal;
Signal switching means for alternately outputting the first signal and the second signal generated by the signal generating means;
A transmission antenna that radiates the first and second signals alternately output from the signal switching means to the space;
After the first signal is radiated from the transmitting antenna, the first signal is incident on the first reflected signal reflected from the target, and after the second signal is radiated from the transmitting antenna, the first signal is emitted. A plurality of element antennas that receive a second reflected signal in which two signals are reflected by the target;
A plurality of phase shifters for adjusting the phases of the first and second reflected signals incident from the element antenna;
A first reflected signal whose phase is adjusted by the plurality of phase shifters is synthesized to generate a first synthesized signal, and a second reflected signal whose phase is adjusted by the plurality of phase shifters is synthesized. A signal synthesis means for generating a second synthesized signal;
Time averaging means for calculating a time average of the first combined signal generated by the signal combining means and the complex conjugate signal of the second combined signal generated by the signal combining means;
A radar apparatus comprising: target detection means for detecting the target from the calculation result of the time averaging means. A signal generating means for generating a first signal as a transmission signal and generating a second signal in a complex conjugate relationship with the first signal;
Signal switching means for alternately outputting the first signal and the second signal generated by the signal generating means;
A plurality of element antennas forming an antenna aperture;
Signal distribution means for distributing the first and second signals alternately output from the signal switching means to a plurality of signals;
By adjusting the phases of the first and second signals distributed by the signal distribution means and outputting the first and second signals after phase adjustment to the element antenna, the first and second signals after phase adjustment are output. While the second signal is radiated to the space, the first signal is reflected by the target and the first reflected signal and the second signal incident from the element antenna are reflected by the target and the element antenna. A plurality of phase shifters for adjusting the phase of the second reflected signal incident from
A first reflected signal whose phase is adjusted by the plurality of phase shifters is synthesized to generate a first synthesized signal, and a second reflected signal whose phase is adjusted by the plurality of phase shifters is synthesized. A signal synthesis means for generating a second synthesized signal;
Time averaging means for calculating a time average of the first combined signal generated by the signal combining means and the complex conjugate signal of the second combined signal generated by the signal combining means;
A radar apparatus comprising: target detection means for detecting the target from the calculation result of the time averaging means.   The radar apparatus according to any one of claims 1 to 3, wherein the plurality of element antennas are arranged symmetrically with respect to a conjugate center.   The radar apparatus according to claim 4, wherein the plurality of element antennas are arranged at equal intervals on a straight line.   The radar apparatus according to claim 4, wherein the plurality of element antennas are arranged in an equidistant square array. A signal generation step of generating a first signal as a transmission signal and generating a second signal having a complex conjugate relationship with the first signal;
A signal switching processing step in which the signal switching means alternately outputs the first signal and the second signal generated in the signal generation processing step;
A signal distribution unit that distributes the first and second signals alternately output in the signal switching processing step into a plurality of signals;
A phase adjustment processing step in which a plurality of phase shifters adjust the phases of the first and second signals distributed in the signal distribution processing step;
A signal radiation step in which a plurality of element antennas radiate the first and second signals, the phases of which are adjusted in the phase adjustment processing step, into space;
After the first signal is radiated from the element antenna, the receiving antenna enters the first reflected signal reflected from the target, and the second signal is radiated from the element antenna. Thereafter, a signal incident step in which the second signal is incident on a second reflected signal reflected by the target;
A time averaging means for calculating a time average between the first reflected signal incident in the signal incident step and the complex conjugate signal of the second reflected signal incident in the signal incident step;
A target detection method, comprising: a target detection unit that detects a target from a calculation result in the time average processing step. A signal generation step of generating a first signal as a transmission signal and generating a second signal having a complex conjugate relationship with the first signal;
A signal switching processing step in which the signal switching means alternately outputs the first signal and the second signal generated in the signal generation processing step;
A signal radiation step in which a transmission antenna radiates the first and second signals alternately output in the signal switching processing step to space; and
After the first signal is radiated from the transmitting antenna, the plurality of element antennas enter the first reflected signal reflected by the target and the second signal is radiated from the transmitting antenna. A signal incident step in which the second signal is incident on the second reflected signal reflected by the target;
A phase adjustment processing step in which a plurality of phase shifters adjust the phases of the first and second reflected signals incident in the signal incident step;
The signal combining means generates a first combined signal by combining the plurality of first reflected signals whose phases are adjusted in the phase adjustment processing step, and a plurality of the phases whose phases are adjusted in the phase adjustment processing step A signal synthesis processing step of synthesizing the second reflected signal to generate a second synthesized signal;
Time averaging processing step in which time averaging means calculates a time average between the first synthesized signal generated in the signal synthesis processing step and the complex conjugate signal of the second synthesized signal generated in the signal synthesis processing step. When,
A target detection method, comprising: a target detection unit that detects a target from a calculation result in the time average processing step. A signal generation step of generating a first signal as a transmission signal and generating a second signal having a complex conjugate relationship with the first signal;
A signal switching processing step in which the signal switching means alternately outputs the first signal and the second signal generated in the signal generation processing step;
A signal distribution unit that distributes the first and second signals alternately output in the signal switching processing step into a plurality of signals;
A plurality of phase shifters adjust the phases of the first and second signals distributed in the signal distribution processing step, and output the first and second signals after phase adjustment to the element antenna, While the phase-adjusted first and second signals are radiated to the space, the first reflected signal and the second signal reflected from the target antenna and incident from the element antenna are reflected by the target. A phase adjustment processing step of adjusting the phase of the second reflected signal reflected from the element antenna and reflected from the element antenna;
The signal combining means generates a first combined signal by combining the plurality of first reflected signals whose phases are adjusted in the phase adjustment processing step, and a plurality of the phases whose phases are adjusted in the phase adjustment processing step A signal synthesis processing step of synthesizing the second reflected signal to generate a second synthesized signal;
Time averaging processing step in which time averaging means calculates a time average between the first synthesized signal generated in the signal synthesis processing step and the complex conjugate signal of the second synthesized signal generated in the signal synthesis processing step. When,
A target detection method, comprising: a target detection unit that detects a target from a calculation result in the time average processing step.

Images