Radar system

Abstract

To provide a radar system that places minimal weight on the aircraft. [Solution] The radar system includes: an electrical signal generator that outputs an electrical signal; an optical signal generator that generates an optical signal of a first frequency and an optical signal of a second frequency based on the electrical signal output by the electrical signal generator and outputs the generated optical signals; an electromagnetic wave transmitting / receiving unit that transmits electromagnetic waves based on the optical signal output by the optical signal generator and outputs an optical signal based on the received electromagnetic waves; a first optical / electrical converter that generates an electrical signal based on the optical signal output from the electromagnetic wave transmitting / receiving unit; and a signal mixing unit that mixes the electrical signal output by the electrical signal generator and the electrical signal generated by the optical / electrical converter.

Description

Technical Field

[0005]

[0001] The present invention relates to a radar system.

Background Art

[0002] Non-Patent Document 1 discloses a radar system using a drone. In this radar system, an optical signal generator that generates two optical signals with different frequencies, and an optical / electrical converter that converts the two optical signals into an electrical signal with a frequency equal to the difference between the frequencies of the two optical signals are provided. Therefore, in this radar system, by controlling the difference between the frequencies of the two optical signals, it is possible to transmit electromagnetic waves in an arbitrary band in the range of approximately 1 GHz to 1000 GHz, and it is possible to increase the range resolution.

[0003] Also, in this radar system, large devices such as an optical signal generator and a signal processing system that performs signal processing are installed on the ground, and only small devices such as an optical / electrical converter and an antenna are mounted on the drone. Therefore, it is possible to suppress the size of the drone and the weight of the devices mounted on the drone. As a result, in this radar system, it is possible to suppress the airflow generated by the drone during flight, and it is possible to fly the drone in a narrow space such as inside a chimney.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the radar system disclosed in Non-Patent Document 1, the detector is mounted on a drone and connected to a signal processing system installed on the ground via an electrical cable. If the sweep speed of the frequency of the emitted electromagnetic wave is increased to shorten the measurement time, the frequency of the signal output from the detector increases. In such cases, if the detector and the signal processing system are connected with a thin metal cable, the loss will be large. Therefore, in order to increase the sweep speed of the frequency of the emitted electromagnetic wave, the electrical cable connecting the detector (equipment mounted on the drone) and the signal processing system (equipment installed on the ground) must be a metal coaxial cable capable of transmitting high-frequency signals, rather than a thin metal cable, which increases the weight on the drone.

[0006] Therefore, the present invention aims to provide a radar system that reduces the weight on the aircraft. [Means for solving the problem]

[0007] To solve the above problems, a radar system according to one embodiment of the present invention includes: an electrical signal generator that outputs an electrical signal; an optical signal generator that generates an optical signal of a first frequency and an optical signal of a second frequency based on the electrical signal output by the electrical signal generator and outputs the generated optical signals; an electromagnetic wave transmitting and receiving unit that transmits electromagnetic waves based on the optical signal output by the optical signal generator and outputs an optical signal based on the received electromagnetic waves; a first optical / electrical converter that generates an electrical signal based on the optical signal output from the electromagnetic wave transmitting and receiving unit; and a signal mixing unit that mixes the electrical signal output by the electrical signal generator and the electrical signal generated by the optical / electrical converter.

[0008] The electromagnetic wave transmitting and receiving unit includes an optical / electrical conversion unit that converts optical signals into electrical signals and electrical signals into optical signals, a transmitting antenna that transmits electromagnetic waves, and a receiving antenna that receives electromagnetic waves. The optical / electrical conversion unit generates an electrical signal based on the optical signal output by the optical signal generator, the transmitting antenna transmits electromagnetic waves based on the incident signal generated by the optical / electrical conversion unit, and the optical / electrical conversion unit may generate an optical signal based on the electrical signal based on the electromagnetic waves received by the receiving antenna.

[0009] The electromagnetic wave transmitting and receiving unit may include an optical / electrical conversion unit that converts optical signals into electrical signals and electrical signals into optical signals, a transmitting and receiving antenna that transmits and receives electromagnetic waves, and a circulator having a first port, a second port, and a third port. The optical / electrical conversion unit generates an electrical signal based on the optical signal output by the optical signal generator, the first port of the circulator receives the electrical signal generated by the optical / electrical conversion unit, the second port of the circulator is connected to the transmitting and receiving antenna, and the optical / electrical conversion unit may generate an optical signal based on the electrical signal output from the third port of the circulator.

[0010] The electromagnetic wave transmitting and receiving unit further comprises an optical / electrical conversion unit that converts optical signals into electrical signals and electrical signals into optical signals, a transmitting and receiving antenna that transmits and receives electromagnetic waves, and a unidirectional coupler having an input port, an output port, and a coupling port. The optical / electrical conversion unit generates an electrical signal based on the optical signal output by the optical signal generator, the coupling port of the directional coupler receives the electrical signal generated from the optical / electrical conversion unit, the input port of the directional coupler is connected to the transmitting and receiving antenna, and the optical / electrical conversion unit may generate an optical signal based on the electrical signal output from the output port of the directional coupler.

[0011] The radar system further comprises a first optical fiber for transmitting an optical signal output by the optical signal generator and a second optical fiber for transmitting an optical signal output from the optical / electrical conversion unit, and the optical / electrical conversion unit may include a second optical / electrical converter for generating an electrical signal based on the optical signal transmitted by the first optical fiber and an electrical / optical converter for generating an optical signal based on an electrical signal based on electromagnetic waves received by the receiving antenna.

[0012] The radar system further comprises an optical fiber for transmitting an optical signal output by the optical signal generator and an optical signal output from the optical / electrical conversion unit, wherein the optical / electrical conversion unit may include a second optical / electrical converter that generates an electrical signal based on the optical signal output by the optical signal generator, an electrical / optical converter that generates an optical signal based on an electrical signal based on electromagnetic waves received by the receiving antenna, and a WDM optical coupler connected between the optical fiber, the optical / electrical converter and the electrical / optical converter. [Effects of the Invention]

[0013] This invention makes it possible to provide a radar system that reduces the weight on the aircraft. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows a radar system 100 according to one embodiment of the present invention. [Figure 2] This diagram illustrates the signal flow in radar system 100. [Figure 3] This figure shows an example of an electromagnetic wave transmitting / receiving unit 140. [Figure 4] This diagram illustrates the signal flow in the electromagnetic wave transmitting / receiving unit 140. [Figure 5] This figure shows an example of an electromagnetic wave transmitting / receiving unit 140. [Figure 6] This diagram illustrates the signal flow in the electromagnetic wave transmitting / receiving unit 140. [Figure 7]It is a diagram showing an example of the electromagnetic wave transmitting and receiving unit 140. [Figure 8] It is a diagram for explaining the signal flow in the electromagnetic wave transmitting and receiving unit 140. [Figure 9] It is a diagram showing another example of the optical / electrical conversion unit. [Figure 10] It is a diagram showing an example of the signal mixing unit 170. [Figure 11] It is a diagram for explaining the signal flow in the signal mixing unit 170. [Figure 12] It is a diagram showing an example of the signal mixing unit 170.

Embodiments for Carrying Out the Invention

[0015] <Radar System 100> FIG. 1 is a diagram showing a radar system 100 according to an embodiment of the present invention. The radar system 100 includes an electrical signal generator 110, an optical signal generator 120, a first optical fiber 130, an electromagnetic wave transmitting and receiving unit 140, a second optical fiber 150, a first optical / electrical converter 160, and a signal mixing unit 170. The radar system 100 is a radar system using a frequency sweep homodyne detection method.

[0016] The electrical signal generator 110 generates an electrical signal (incident signal). The electrical signal generator 110 outputs the generated incident signal to the optical signal generator 120 and the signal mixing unit 170.

[0017] The optical signal generator 120 outputs two optical signals of different frequencies (an optical signal with a first frequency f1 and an optical signal with a second frequency f2). The optical signal generator 120 may be configured, for example, with a laser light source that outputs single-wavelength laser light and an optical intensity modulator driven by an electrical signal with a frequency f0 that is half the frequency of the incident signal output from the electrical signal generator 110. At this time, the DC bias point of the optical intensity modulator is set to the operating point where the transmittance is minimized, and the optical intensity modulator is used to perform double side-band supported carrier (DSB-SC) modulation (H. Kikuchi; “Photonic Millimeter-Wave Generation and Distribution Technics for Millimeter / Sub-Millimeter Wave Radio Interferometer Telescope,” Advances in Lasers and Electro Optics, (Intech, 2010) p.479) on the single-wavelength laser light, thereby generating two optical signals with a frequency difference of 2·f0 (i.e., the frequency of the incident signal).

[0018] The first optical fiber 130 transmits optical signals. An optical signal generator 120 is connected to one end of the first optical fiber 130, and the two optical signals output by the optical signal generator 120 are transmitted through the first optical fiber 130, as shown in Figure 2.

[0019] The electromagnetic wave transmitting / receiving unit 140 is connected to the other end of the first optical fiber 130, and the two optical signals output by the optical signal generator 120 are transmitted through the first optical fiber 130 and input to the electromagnetic wave transmitting / receiving unit 140. The electromagnetic wave transmitting / receiving unit 140 generates an electrical signal based on the two optical signals output by the optical signal generator 120. The first optical / electrical conversion unit 160 generates an electrical signal (i.e., an incident signal) with a frequency of the difference between the frequencies of the two input optical signals (|f1-f2|).

[0020] As detailed below, the electromagnetic wave transmitting and receiving unit 140 has a transmitting antenna 141T that transmits electromagnetic waves and a receiving antenna 141R (or a transmitting and receiving antenna 141TR that transmits and receives electromagnetic waves), and transmits electromagnetic waves (incident waves) based on the generated electrical signal from the transmitting antenna 141T (or transmitting and receiving antenna 141TR) toward the object to be measured. Since the frequency of the generated electrical signal is the difference in frequencies of the optical signals (|f1-f1|), the electromagnetic wave transmitting and receiving unit 140 transmits electromagnetic waves (incident waves) with a frequency of the difference in frequencies of the two optical signals output from the optical signal generator 120 (|f1-f2|) from the transmitting antenna 141T (or transmitting and receiving antenna 141TR).

[0021] Furthermore, the electromagnetic wave transmitting and receiving unit 140 receives electromagnetic waves (reflected waves) reflected by the object being measured using the receiving antenna 141R (or transmitting and receiving antenna 141TR). The electromagnetic wave transmitting and receiving unit 140 outputs an optical signal (an optical signal with the frequency of the reflected wave) based on the electromagnetic waves (reflected waves) received by the receiving antenna 141R (or transmitting and receiving antenna 141TR).

[0022] The second optical fiber 150 transmits optical signals. The first optical / electrical conversion unit 160 is connected to one end of the second optical fiber 150, and the optical signals output from the electromagnetic wave transmitting / receiving unit 140 are transmitted through the second optical fiber 150, as shown in Figure 2.

[0023] The first optical / electrical converter 160 is connected to the other end of the second optical fiber 150, and receives the optical signal output by the electromagnetic wave transmitting / receiving unit 140 transmitted through the second optical fiber 150. The first optical / electrical converter 160 generates an electrical signal (reflected signal: an electrical signal with the frequency of the reflected wave) based on the optical signal output by the electromagnetic wave transmitting / receiving unit 140, and outputs the generated reflected signal.

[0024] The signal mixing unit 170 mixes the incident signal output from the electrical signal generator 110 with the reflected signal output from the electromagnetic wave transmitting / receiving unit 140, and outputs this mixed electrical signal (mixed signal). The signal mixing unit 170 is preferably connected to a signal processing system such as a dynamic multimeter, as shown in Figure 1, and the mixed signal output from the signal mixing unit 170 is sent to the signal processing system.

[0025] In this embodiment, by adjusting the first frequency f1 and second frequency f2 of the optical signal output by the optical signal generator 120 (i.e., the frequency 2·f0 of the incident signal output by the electrical signal generator 110), it is possible to incident a wideband electromagnetic wave (for example, an electromagnetic wave of any band in the range of approximately 1 GHz to 1000 GHz) onto the object to be measured. By rapidly changing the frequency 2·f0 of the incident signal output by the electrical signal generator 110, it is possible to rapidly change the frequency of the electromagnetic wave emitted from the transmitting antenna 141T (or transmitting / receiving antenna 141TR) and rapidly sweep a wide frequency range. For example, if an arbitrary waveform generator is used as the electrical signal generator 110, it is possible to sweep a frequency range of 40 GHz in 0.4 milliseconds.

[0026] Therefore, in this embodiment, similar to the frequency-modulated continuous wave (FMCV) ranging method, it is possible to incident a frequency-modulated continuous wave onto the object to be measured. As a result, in this embodiment, depth information of the object to be measured (distance to the object and thickness) can be obtained by mixing the incident signal and the reflected signal in the signal mixing unit 170, similar to the frequency-modulated continuous wave ranging method.

[0027] Furthermore, as shown in Figure 1, the equipment mounted on the aircraft F (for example, a drone) may be an electromagnetic wave transmitting / receiving unit 140, while the electrical signal generator 110, optical signal generator 120, first optical / electrical converter 160, and signal mixing unit 170 may not be mounted on the aircraft F but instead placed on the ground, for example. This reduces the weight of the equipment mounted on the aircraft F. As a result, it becomes possible to suppress the airflow generated by the aircraft during flight, making it possible to fly the aircraft in narrow spaces such as inside a chimney.

[0028] Furthermore, in this embodiment, the equipment mounted on the aircraft F and the equipment installed on the ground are connected by optical fibers 130 and 150. Therefore, in this embodiment, even when the sweep speed of the frequency of the electromagnetic waves emitted by the transmitting antenna is increased, it is not necessary to connect the equipment mounted on the aircraft F and the equipment installed on the ground with a metal coaxial cable. As a result, this embodiment makes it possible to provide a radar system with a small weight on the aircraft.

[0029] <Electromagnetic wave transmitting / receiving unit 140> The electromagnetic wave transmitting and receiving unit 140 includes, for example, a transmitting antenna 141T, a receiving antenna 141R, a second optical / electrical converter 142, and an electrical / optical converter 143, as shown in Figure 3.

[0030] The transmitting antenna 141T emits electromagnetic waves based on the input electrical signal.

[0031] The receiving antenna 141R outputs an electrical signal based on the received electromagnetic waves.

[0032] The second optical / electrical converter 142 has an input port 1421 and an output port 1422. It converts an optical signal input from the input port 1421 into an electrical signal and outputs the electrical signal from the output port 1422. The second optical / electrical converter 142 is, for example, a photodiode.

[0033] The electrical / optical converter 143 has an input port 1431 and an output port 1432. It converts an electrical signal input from the input port 1431 into an optical signal and outputs the optical signal from the output port 1432. The electrical / optical converter 143 is composed of, for example, a semiconductor laser and an optical modulator.

[0034] In the example shown in Figure 3, the input port 1421 of the second optical / electric converter 142 is connected to the first optical fiber 130, the output port 1422 of the second optical / electric converter 142 is connected to the transmitting antenna 141T, the receiving antenna 141R is connected to the input port 1431 of the electrical / optical converter 143, and the output port 1432 of the electrical / optical converter 143 is connected to the second optical fiber 150.

[0035] Therefore, in the example shown in Figure 3, as shown in Figure 4, the two optical signals transmitted through the first optical fiber 130 are input to the second optical / electrical converter 142. The second optical / electrical converter 142 generates an electrical signal based on the two optical signals output by the optical signal generator 120, and outputs the generated electrical signal (incident signal) to the transmitting antenna 141T. The transmitting antenna 141T emits an electromagnetic wave (incident wave) at the frequency of the incident signal. The reflected signal (electrical signal at the frequency of the reflected wave) output from the receiving antenna 141R, which has received the electromagnetic wave (reflected wave), is input to the electrical / optical converter 143. The electrical / optical converter 143 generates an optical signal (optical signal at the frequency of the reflected wave) based on the input reflected signal, and outputs the generated optical signal to the second optical fiber 150.

[0036] As shown in Figure 5, the electromagnetic wave transmitting and receiving unit 140 may have a transmitting and receiving antenna 141TR and a circulator 144 instead of a transmitting antenna 141T and a receiving antenna 141R.

[0037] The circulator 144 has a first port 1441, a second port 1442, and a third port 1443. The circulator 144 outputs an electrical signal input to the first port 1441 from the second port 1442, outputs an electrical signal input from the second port 1442 to the third port 1443, and outputs an electrical signal input from the third port 1443 from the first port 1441.

[0038] In the example shown in Figure 5, the output port 1422 of the second optical / electric converter 142 is connected to the first port 1441 of the circulator 144, the second port 1442 of the circulator 144 is connected to the transmitting / receiving antenna 141TR, and the third port 1443 of the circulator 144 is connected to the input port 1431 of the electric / optical converter 143.

[0039] Therefore, in the example shown in Figure 5, as shown in Figure 6, the incident signal output from the second optical / electrical converter 142 is input to the first port 1441 of the circulator 144, output from the second port 1442 of the circulator 144, input to the transmitting / receiving antenna 141TR, and an electromagnetic wave (incident wave) with the frequency of the incident signal is transmitted from the transmitting / receiving antenna 141TR. The reflected signal (electrical signal with the frequency of the reflected wave) output from the transmitting / receiving antenna 141TR, which has received the electromagnetic wave (reflected wave), is input to the second port 1442 of the circulator 144, output from the third port 1443 of the circulator 144, and input to the electrical / optical converter 143.

[0040] As shown in Figure 7, the electromagnetic wave transmitting and receiving unit 140 may have a transmitting and receiving antenna 141TR and a unidirectional coupler 145 instead of a transmitting antenna 141T and a receiving antenna 141R.

[0041] The unidirectional coupler 145 has an input port 1451, an output port 1452, and a coupling port 1453. The unidirectional coupler 145 may also be a so-called bidirectional coupler, having an isolation port in addition to the input port 1451, output port 1452, and coupling port 1453. If the unidirectional coupler 145 is a bidirectional coupler, the isolation port is terminated.

[0042] The unidirectional coupler 145 outputs a portion of the electrical signal input from input port 1451 through output port 1452, and the remaining electrical signal through coupling port 1453. Furthermore, the unidirectional coupler 145 outputs a portion of the electrical signal input from coupling port 1453 through input port 1451.

[0043] In the example shown in Figure 7, the output port 1422 of the second optical / electric converter 142 is connected to the coupling port 1453 of the unidirectional coupler 145, the input port 1451 of the unidirectional coupler 145 is connected to the transmit / receive antenna 141TR, and the output port 1452 of the unidirectional coupler 145 is connected to the input port 1431 of the electric / optical converter 143.

[0044] Therefore, in the example shown in Figure 7, as shown in Figure 8, the incident signal output from the second optical / electrical converter 142 is input to the coupling port 1453 of the unidirectional coupler 145, output from the input port 1451 of the unidirectional coupler 145, input to the transmitting / receiving antenna 141TR, and an electromagnetic wave (incident wave) with the frequency of the incident signal is emitted from the transmitting / receiving antenna 141TR. The reflected signal (electrical signal with the frequency of the reflected wave) output from the transmitting / receiving antenna 141TR, which has received the electromagnetic wave (reflected wave), is input to the input port 1451 of the unidirectional coupler 145, output from the output port 1452 of the unidirectional coupler 145, and input to the electrical / optical converter 143.

[0045] <Optical / Electric Conversion Unit> The second optical / electrical converter 142 and the electrical / optical converter 143 constitute an optical / electrical conversion unit that converts optical signals into electrical signals and electrical signals into optical signals. This optical / electrical conversion unit may further include a WDM (Wavelength Division Multiplexing) optical coupler 146, as shown in Figure 9. In this case, the radar system 100 has one optical fiber 180 instead of the first optical fiber 130 and the second optical fiber 150.

[0046] The WDM optical coupler 146 is connected between one optical fiber 180 and the second optical / electrical converter 142 and the electrical / optical converter 143, and receives the optical signal output by the optical signal generator 120 and transmitted through the first optical fiber 130, and the optical signal output from the electrical / optical converter 143 as input. The WDM optical coupler 146 outputs the optical signal input from the optical fiber 180 to the second optical / electrical converter 142, and outputs the optical signal input from the electrical / optical converter 143 to the optical fiber 180.

[0047] At this time, a WDM optical coupler 190 is also connected between the optical fiber 180 and the optical signal generator 120 and the first optical / electrical converter 160, as shown in Figure 9. The WDM optical coupler 190 receives the optical signal output from the optical signal generator 120 and the optical signal output from the electrical / optical converter 143 and transmitted through the optical fiber 180 as input. The WDM optical coupler 190 outputs the optical signal input from the optical signal generator 120 to the optical fiber 180 and outputs the optical signal input from the optical fiber 180 to the first optical / electrical converter 160.

[0048] <Signal mixing section 170>

[0049] The signal mixing unit 170 includes, for example, a multiplexer 171 and a detector 172, as shown in Figure 10.

[0050] The multiplexer 171 has two input ports and one output port, and outputs electrical signals input from the two input ports through the single output port. The two input ports of the multiplexer 171 are connected to the electrical signal generator 110 and the first optical / electrical converter 160, respectively.

[0051] The detector 172 has an input port and an output port. It mixes the electrical signals input from the input port and outputs this mixed electrical signal (mixed signal) from the output port. The input port of the detector 172 is connected to the multiplexer 171. The output port of the detector 172 is connected to, for example, a signal processing system.

[0052] As shown in Figure 11, the two input ports of the multiplexer 171 receive the incident signal output from the electrical signal generator 110 and the reflected signal output from the first optical / electrical converter 160, respectively. These input incident and reflected signals are then output from the output port of the multiplexer 171 to the detector 172. The detector 172 receives the incident and reflected signals output from the multiplexer 171, mixes these input incident and reflected signals, and outputs the resulting mixed electrical signal (mixed signal).

[0053] The signal mixing unit 170 may also include a mixer 173, as shown in Figure 12.

[0054] The mixer 173 has two input ports and one output port. As shown in Figure 12, the two input ports of the mixer 173 receive the incident signal output from the electrical signal generator 110 and the reflected signal output from the first optical / electrical converter 160, respectively. The mixer 173 mixes these input incident and reflected signals and outputs the resulting mixed electrical signal (mixed signal).

[0055] The present invention has been described above with reference to preferred embodiments. Although the present invention has been described with reference to specific examples, various modifications and changes can be made to these examples without departing from the spirit and scope of the invention as described in the claims. [Explanation of Symbols]

[0056] 100 Radar Systems 110 Electrical signal generator 120 Optical signal generator 130 The first optical fiber 140 Electromagnetic wave transmitting and receiving unit 141T Transmitting Antenna 141R Receiving Antenna 141TR Transceiver Antenna 142 Second Optical / Electric Converter 1421 Input port of the second optical / electric converter 142 1422 Output port of the second optical / electric converter 142 143 Electric / Optical Converter 1431 Input port of electrical / optical converter 143 1432 Output port of the electrical / optical converter 143 144 Circulator 1441 First port of circulator 144 1442 Second port of circulator 144 1443 Third port of Circulator 144 145 Unidirectional Coupler 1451 Input port of unidirectional coupler 145 1452 Output port of unidirectional coupler 145 1453 Coupling port of unidirectional coupler 145 146 WDM optical coupler 150 Second optical fiber 160 First Optical / Electric Converter 170 Signal mixing section 171 Multiplexer 172 Detector 173 Mixer 180 optical fibers 190 WDM optical connector

Claims

1. An electrical signal generator that outputs an electrical signal, An optical signal generator that generates an optical signal of a first frequency and an optical signal of a second frequency based on the electrical signal output by the aforementioned electrical signal generator, and outputs the generated optical signals, An electromagnetic wave transmitting and receiving unit that transmits electromagnetic waves based on the optical signal output by the optical signal generator and outputs an optical signal based on the received electromagnetic wave, A first optical / electrical converter that generates an electrical signal based on the optical signal output from the electromagnetic wave transmitting / receiving unit, A radar system comprising a signal mixing unit that mixes an electrical signal output by the electrical signal generator and an electrical signal generated by the optical / electrical converter. The radar system installed on the vehicle.

2. The electromagnetic wave transmitting and receiving unit is An optical / electrical conversion unit that converts optical signals into electrical signals and electrical signals into optical signals, A transmitting antenna that transmits electromagnetic waves, It has a receiving antenna that receives electromagnetic waves, The aforementioned optical / electrical conversion unit generates an electrical signal based on the optical signal output by the optical signal generator, The transmitting antenna transmits electromagnetic waves based on the incident signal generated by the optical / electrical conversion unit. The radar system according to claim 1, wherein the optical / electrical conversion unit generates an optical signal based on an electrical signal based on electromagnetic waves received by the receiving antenna.

3. The electromagnetic wave transmitting and receiving unit is An optical / electrical conversion unit that converts optical signals into electrical signals and electrical signals into optical signals, A transmitting and receiving antenna that sends and receives electromagnetic waves, A circulator having a first port, a second port, and a third port, The aforementioned optical / electrical conversion unit generates an electrical signal based on the optical signal output by the optical signal generator, The first port of the circulator receives an electrical signal generated from the optical / electrical conversion unit. The second port of the circulator is connected to the transmitting and receiving antenna. The radar system according to claim 1, wherein the optical / electrical conversion unit generates an optical signal based on an electrical signal output from the third port of the circulator.

4. The electromagnetic wave transmitting and receiving unit is An optical / electrical conversion unit that converts optical signals into electrical signals and electrical signals into optical signals, A transmitting and receiving antenna that sends and receives electromagnetic waves, The system further comprises a unidirectional coupler having an input port, an output port, and a coupling port, The aforementioned optical / electrical conversion unit generates an electrical signal based on the optical signal output by the optical signal generator, The coupling port of the directional coupler receives an electrical signal generated from the optical / electrical conversion unit. The input port of the directional coupler is connected to the transmitting and receiving antenna, The radar system according to claim 1, wherein the optical / electrical conversion unit generates an optical signal based on an electrical signal output from the output port of the directional coupler.

5. A first optical fiber that transmits the optical signal output by the optical signal generator, The system further includes a second optical fiber that transmits the optical signal output from the aforementioned optical / electrical conversion unit, The aforementioned optical / electrical conversion unit is A second optical / electrical converter that generates an electrical signal based on the optical signal transmitted by the first optical fiber, A radar system according to any one of claims 1 to 4, comprising an electrical / optical converter that generates an optical signal based on an electrical signal based on electromagnetic waves received by the receiving antenna.

6. The system further comprises an optical fiber for transmitting the optical signal output by the optical signal generator and the optical signal output from the optical / electrical conversion unit, The aforementioned optical / electrical conversion unit is A second optical / electrical converter that generates an electrical signal based on the optical signal output by the optical signal generator, An electrical / optical converter that generates an optical signal based on an electrical signal based on electromagnetic waves received by the receiving antenna, A radar system according to any one of claims 1 to 4, comprising the optical fiber, the optical / electrical converter, and a WDM optical coupler connected between the optical / electrical converter.

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