Radar system

Abstract

To provide a radar system that places minimal weight on the aircraft. [Solution] The radar system includes a first optical / electrical conversion unit that generates an incident signal based on an optical signal, an electromagnetic wave transmitting / receiving unit that transmits and receives electromagnetic waves, the electromagnetic wave transmitting / receiving unit which transmits electromagnetic waves based on the incident signal and outputs a reflected signal based on the received electromagnetic waves and the incident signal, and a signal mixing unit which mixes the incident signal and reflected signal output from the electromagnetic wave transmitting / receiving unit and outputs the mixed signal, and the first optical / electrical conversion unit generates an optical signal based on the mixed signal output by the signal mixing unit.

Description

Technical Field

[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 having different frequencies, and an optical / electrical converter that converts the two optical signals into an electrical signal having 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 improve 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 equipment mounted on the drone. As a result, in this radar system, it is possible to suppress the airflow generated by the drone during flight of the drone, 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: a first optical / electrical conversion unit that generates an incident signal based on an optical signal; an electromagnetic wave transmitting and receiving unit that transmits and receives electromagnetic waves, the electromagnetic wave transmitting and receiving unit that transmits electromagnetic waves based on the incident signal and outputs a reflected signal based on the received electromagnetic wave and the incident signal; and a signal mixing unit that mixes the incident signal and the reflected signal output from the electromagnetic wave transmitting and receiving unit and outputs the mixed signal, wherein the first optical / electrical conversion unit generates an optical signal based on the mixed signal output by the signal mixing unit.

[0008] The electromagnetic wave transmitting and receiving unit includes a transmitting antenna that transmits electromagnetic waves, a receiving antenna that receives electromagnetic waves, and a branch having an input port, a first output port, and a second output port. The incident signal generated by the first optical / electrical conversion unit is input to the input port of the branch, the first output port of the branch is connected to the transmitting antenna, and the signal mixing unit may mix the incident signal output from the second output port of the branch with a reflected signal based on the electromagnetic waves received by the receiving antenna.

[0009] The electromagnetic wave transmitting and receiving unit includes a transmitting and receiving antenna for transmitting and receiving electromagnetic waves, a branch having an input port, a first output port, and a second output port, and a circulator having a first port, a second port, and a third port. The incident signal generated by the first optical / electrical conversion unit is input to the input port of the branch, the first output port of the branch is connected to the first port of the circulator, and the second port of the circulator is connected to the transmitting and receiving antenna. The signal mixing unit may mix the incident signal output from the second output port of the branch with the reflected signal output from the third port of the circulator.

[0010] The electromagnetic wave transmitting and receiving unit includes a transmitting and receiving antenna for transmitting and receiving electromagnetic waves, a branch having an input port, a first output port, and a second output port, and a unidirectional coupler having an input port, an output port, and a coupling port. The incident signal generated by the first optical / electrical conversion unit is input to the input port of the branch, the first output port of the branch is connected to the coupling port of the unidirectional coupler, the input port of the unidirectional coupler is connected to the transmitting and receiving antenna, and the signal mixing unit may mix the incident signal output from the second output port of the branch with the reflected signal output from the output port of the unidirectional coupler.

[0011] The electromagnetic wave transmitting and receiving unit includes a transmitting and receiving antenna for transmitting and receiving electromagnetic waves, a brancher having an input port, a first output port, and a second output port, and a bidirectional coupler having an input port, an output port, a coupling port, and an isolation port. The signal mixing unit includes a detector having an input port and an output port. The incident signal generated by the first optical / electrical conversion unit is input to the input port of the brancher, the first output port of the brancher is connected to the coupling port of the bidirectional coupler, the second output port of the brancher is connected to the isolation port of the bidirectional coupler, the input port of the bidirectional coupler is connected to the transmitting and receiving antenna, and the output port of the bidirectional coupler may be connected to the input port of the detector.

[0012] The radar system further comprises an optical signal generator that outputs an optical signal of a first frequency and an optical signal of a second frequency, a first optical fiber that transmits the optical signal output by the optical signal generator, and a second optical fiber that transmits the optical signal output from the first optical / electrical conversion unit, wherein the first optical / electrical conversion unit may include an optical / electrical converter that generates the incident signal based on the optical signal transmitted by the first optical fiber, and an electrical / optical converter that generates an optical signal based on the mixed signal output by the signal mixing unit.

[0013] The radar system further comprises an optical signal generator that outputs an optical signal of a first frequency and an optical signal of a second frequency, and an optical fiber that transmits the optical signal output by the optical signal generator and the optical signal output from the first optical / electrical conversion unit, wherein the first optical / electrical conversion unit comprises an optical / electrical converter that generates the incident signal based on the optical signal output by the optical signal generator, an electrical / optical converter that generates an optical signal based on the mixed signal output by the signal mixing unit, and a WDM optical coupler connected between the optical fiber, the optical / electrical converter and the electrical / optical converter. [Effects of the Invention]

[0014] The present invention makes it possible to provide a radar system with a small weight for an aircraft.

Brief Description of Drawings

[0015] [Figure 1] It is a figure which shows the radar system 100 which concerns on one Embodiment of this invention. [Figure 2] It is a figure explaining the flow of the signal in the radar system 100. [Figure 3] It is a figure which shows an example of the electromagnetic wave transmission / reception part 140. [Figure 4] It is a figure explaining the flow of the signal in the electromagnetic wave transmission / reception part 140. [Figure 5] It is a figure which shows an example of the electromagnetic wave transmission / reception part 140. [Figure 6] It is a figure explaining the flow of the signal in the electromagnetic wave transmission / reception part 140. [Figure 7] It is a figure which shows an example of the electromagnetic wave transmission / reception part 140. [Figure 8] It is a figure explaining the flow of the signal in the electromagnetic wave transmission / reception part 140. [Figure 9] It is a figure which shows an example of the first optical / electrical conversion part 130. [Figure 10] It is a figure which shows an example of the first optical / electrical conversion part 130. [Figure 11] It is a figure which shows an example of the signal mixing part 150. [Figure 12] It is a figure explaining the flow of the signal in the signal mixing part 150. ]> [Figure 13] It is a figure which shows an example of the signal mixing part 150. [Figure 14] It is a figure which shows an example of the electromagnetic wave transmission / reception part 140 and the signal mixing part 150. [Figure 15] It is a figure explaining the flow of the signal in the electromagnetic wave transmission / reception part 140 and the signal mixing part 150.

Embodiments for Carrying Out the Invention

[0016] <Radar System 100> Figure 1 shows a radar system 100 according to one embodiment of the present invention. The radar system 100 includes an optical signal generator 110, a first optical fiber 120, a first optical / electrical conversion unit 130, an electromagnetic wave transmitting and receiving unit 140, a signal mixing unit 150, a second optical fiber 160, and a second optical / electrical conversion unit 170. The radar system 100 is a radar system that uses a frequency-swept homodyne detection method.

[0017] The optical signal generator 110 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 110 can be configured, for example, with a laser light source that outputs single-wavelength laser light, a signal generator that outputs an electrical signal of frequency f0, and an optical intensity modulator driven by the electrical signal output from the signal generator. In this case, 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 performs 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. Therefore, in an optical signal generator 110 with this configuration, it is possible to control the difference in frequencies (|f1-f2|) between the two optical signals output from the optical signal generator 110 by controlling the frequency f0 of the electrical signal output by the signal generator.

[0018] The first optical fiber 120 transmits optical signals. An optical signal generator 110 is connected to one end of the first optical fiber 120, and the two optical signals output by the optical signal generator 110 are transmitted through the first optical fiber 120, as shown in Figure 2.

[0019] The first optical / electrical conversion unit 130 is connected to the other end of the first optical fiber 120, and the two optical signals output by the optical signal generator 110 are transmitted through the first optical fiber 120 and input to the first optical / electrical conversion unit 130. The first optical / electrical conversion unit 130 generates an electrical signal based on the two optical signals output by the optical signal generator 110 and outputs the generated electrical signal (incident signal). The first optical / electrical conversion unit 130 generates an electrical signal with a frequency of the difference between the frequencies of the two input optical signals (|f1-f2|) and outputs this generated electrical signal (incident signal).

[0020] As detailed below, the electromagnetic wave transmitting / receiving unit 140 has a transmitting antenna 141T that transmits electromagnetic waves and a receiving antenna 141R (or a transmitting / receiving antenna 141TR that transmits and receives electromagnetic waves), and transmits electromagnetic waves (incident waves) based on the input electrical signal from the transmitting antenna 141T (or transmitting / receiving antenna 141TR) toward the object to be measured. The electromagnetic wave transmitting / receiving unit 140 is connected to the first optical / electrical conversion unit 130. Therefore, as shown in Figure 2, the incident signal output from the first optical / electrical conversion unit 130 is input to the electromagnetic wave transmitting / receiving unit 140, and electromagnetic waves (incident waves) based on this incident signal are transmitted from the transmitting antenna 141T (or transmitting / receiving antenna 141TR). Since the frequency of the incident signal output from the first optical / electrical conversion unit 130 is the difference in frequencies (|f1-f1|) between the two optical signals output from the optical signal generator 110, the electromagnetic wave transmitting / receiving unit 140 emits an electromagnetic wave (incident wave) with a frequency of the difference in frequencies (|f1-f2|) between the two optical signals output from the optical signal generator 110 from the transmitting antenna 141T (or transmitting / receiving antenna 141TR). At this time, an amplifier may be connected between the first optical / electrical conversion unit 130 and the electromagnetic wave transmitting / receiving unit 140 to amplify the incident signal output from the first optical / electrical conversion unit 130 and output the amplified incident signal to the electromagnetic wave transmitting / receiving unit 140.

[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 then outputs the incident signal input from the first optical / electrical conversion unit 130 and a reflected signal (an electrical 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 signal mixing unit 150 mixes the incident signal and the reflected signal output from the electromagnetic wave transmitting / receiving unit 140 and outputs the mixed electrical signal (mixed signal).

[0023] The first optical / electrical conversion unit 130 generates an optical signal based on the mixed signal output by the signal mixing unit 150 and outputs the optical signal.

[0024] The second optical fiber 160 transmits optical signals. The first optical-to-electrical conversion unit 130 is connected to one end of the second optical fiber 160, and the optical signal output from the first optical-to-electrical conversion unit 130 is transmitted through the first optical fiber 120, as shown in Figure 2.

[0025] The second optical / electrical conversion unit 170 is connected to the other end of the second optical fiber 160, and the optical signal output by the first optical / electrical conversion unit 130 is transmitted through the second optical fiber 160 and input to the second optical / electrical conversion unit 170. The second optical / electrical conversion unit 170 generates an electrical signal (mixed signal) based on the optical signal output by the first optical / electrical conversion unit 130 and outputs the generated mixed signal. In other words, the second optical / electrical conversion unit 170 converts the optical signal output by the first optical / electrical conversion unit 130 back into a mixed signal output by the signal mixing unit 150 and outputs this mixed signal. The second optical / electrical conversion unit 170 may be connected to a signal processing system such as a dynamic multimeter, as shown in Figure 1, and the mixed signal may be sent to the signal processing system.

[0026] In this embodiment, by adjusting the first frequency f1 and the second frequency f2 of the optical signal output by the optical signal generator 110, it is possible to inject a wideband electromagnetic wave (for example, an electromagnetic wave in any band within the range of approximately 1 GHz to 1000 GHz) onto the object to be measured. In particular, as described above, when the optical signal generator 110 is configured with a laser light source, a signal generator, and an optical intensity modulator, by rapidly changing the frequency f0 of the electrical signal output by the signal generator, 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 bandwidth. For example, when an arbitrary waveform generator is used as the signal generator, it is possible to sweep a frequency bandwidth of 40 GHz in 0.4 milliseconds.

[0027] 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 150, similar to the frequency-modulated continuous wave ranging method.

[0028] Furthermore, as shown in Figure 1, the equipment mounted on the aircraft F (for example, a drone) may consist of a first optical / electrical conversion unit 130, an electromagnetic wave transmitting / receiving unit 140, and a signal mixing unit 150, while the optical signal generator 110 may not be mounted on the aircraft F but instead placed, for example, on the ground. 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.

[0029] Furthermore, in this embodiment, the equipment mounted on the aircraft F and the equipment installed on the ground are connected by optical fibers 120 and 160. 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.

[0030] <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, and a splitter 142, as shown in Figure 3.

[0031] The transmitting antenna 141T emits electromagnetic waves based on the input electrical signal.

[0032] The receiving antenna 141R outputs an electrical signal based on the received electromagnetic waves.

[0033] The turnout 142 has an input port 1421, a first output port 1422, and a second output port 1423. The turnout 142 splits the electrical signal input from the input port 1421 into two paths, outputs one of the split electrical signals from the first output port 1422, and outputs the other of the split electrical signals from the second output port 1423.

[0034] The turnout 142, for example, divides the electrical signal input from input port 1421 equally. In other words, the turnout 142 divides the electrical signal input from input port 1421 so that the power value of the electrical signal output from the first output port 1422 is the same as the power value of the electrical signal output from the second output port 1423.

[0035] In the example shown in Figure 3, the input port 1421 of the branch switch 142 is connected to the first optical / electrical conversion unit 130, the first output port 1422 of the branch switch 142 is connected to the transmitting antenna 141T, and the second output port 1423 of the branch switch 142 is connected to the signal mixing unit 150. The receiving antenna 141R is connected to the signal mixing unit 150.

[0036] Therefore, in the example shown in Figure 3, as shown in Figure 4, the incident signal output from the first optical / electrical conversion unit 130 is input to the input port 1421 of the branch switch 142. At this time, if an amplifier is connected between the first optical / electrical conversion unit 130 and the electromagnetic wave transmitting / receiving unit 140, the incident signal output from the first optical / electrical conversion unit 130 is amplified and input to the input port 1421 of the branch switch 142. As shown in Figure 4, the incident signal input from the input port 1421 of the branch switch 142 is split into two paths in the branch switch 142. One of the two split incident signals is output from the first output port 1422 of the branch switch 142 and input to the transmitting antenna 141T, and an electromagnetic wave (incident wave) with the frequency of the incident signal is emitted from the transmitting antenna 141T. The other of the two split incident signals is output from the second output port 1423 of the branch switch 142 and input to the signal mixing unit 150. The reflected signal (an electrical signal at the frequency of the reflected wave) output from the receiving antenna 141R, which receives the electromagnetic wave (reflected wave), is input to the signal mixing unit 150.

[0037] As shown in Figure 5, the electromagnetic wave transmitting and receiving unit 140 may have a transmitting and receiving antenna 141TR and a circulator 143 instead of a transmitting antenna 141T and a receiving antenna 141R.

[0038] The circulator 143 has a first port 1431, a second port 1432, and a third port 1433. The circulator 143 outputs an electrical signal input to the first port 1431 from the second port 1432, outputs an electrical signal input from the second port 1432 to the third port 1433, and outputs an electrical signal input from the third port 1433 from the first port 1431.

[0039] In the example shown in Figure 5, the first output port 1422 of the turnout 142 is connected to the first port 1431 of the circulator 143, and the second output port 1423 of the turnout 142 is connected to the signal mixing unit 150. The second port 1432 of the circulator 143 is connected to the transmitting / receiving antenna 141TR, and the third port 1433 of the circulator 143 is connected to the signal mixing unit 150.

[0040] Therefore, in the example shown in Figure 5, as shown in Figure 6, the incident signal output from the first output port 1422 of the branch switch 142 is input to the first port 1431 of the circulator 143, output from the second port 1432 of the circulator 143, and 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 incident signal output from the second output port 1423 of the branch switch 142 is input to the signal mixing unit 150. 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 1432 of the circulator 143, output from the third port 1433 of the circulator 143, and input to the signal mixing unit 150.

[0041] 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 144 instead of a transmitting antenna 141T and a receiving antenna 141R.

[0042] The unidirectional coupler 144 has an input port 1441, an output port 1442, and a coupling port 1443. The unidirectional coupler 144 may also be a so-called bidirectional coupler, having an isolation port in addition to the input port 1441, output port 1442, and coupling port 1443. If the unidirectional coupler 144 is a bidirectional coupler, the isolation port is terminated.

[0043] The unidirectional coupler 144 outputs a portion of the electrical signal input from the input port 1441 from the output port 1442, and outputs the remaining electrical signal from the coupling port 1443. Furthermore, the unidirectional coupler 144 outputs a portion of the electrical signal input from the coupling port 1443 through the input port 1441.

[0044] In the example shown in Figure 7, the first output port 1422 of the turnout 142 is connected to the coupling port 1443 of the unidirectional coupler 144, and the second output port 1423 of the turnout 142 is connected to the signal mixer 150. The input port 1441 of the unidirectional coupler 144 is connected to the transmit / receive antenna 141TR, and the output port 1442 of the unidirectional coupler 144 is connected to the signal mixer 150.

[0045] Therefore, in the example shown in Figure 7, as shown in Figure 8, the incident signal output from the first output port 1422 of the branch switch 142 is input to the coupling port 1443 of the unidirectional coupler 144, output from the input port 1441 of the unidirectional coupler 144, and 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 incident signal output from the second output port 1423 of the branch switch 142 is input to the signal mixing unit 150. 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 1441 of the unidirectional coupler 144, output from the output port 1442 of the unidirectional coupler 144, and input to the signal mixing unit 150.

[0046] <First optical / electrical conversion unit 130> As shown in Figure 9, the first optical / electrical conversion unit 130 is connected to the first optical fiber 120 and the second optical fiber 160, and includes an optical / electrical converter 131 that converts optical signals to electrical signals, and an electrical / optical converter 132 that converts electrical signals to optical signals. The optical / electrical converter 131 is, for example, a photodiode. The electrical / optical converter 132 is, for example, composed of a semiconductor laser or an optical modulator.

[0047] The optical / electrical converter 131 receives two optical signals transmitted through the first optical fiber 120. The optical / electrical converter 131 generates an electrical signal based on these two input optical signals and outputs the generated electrical signal (incident signal) to the electromagnetic wave transmitting / receiving unit 140.

[0048] The electrical / optical converter 132 receives the mixed signal output by the signal mixing unit 150. The electrical / optical converter 132 generates an optical signal based on this input mixed signal and outputs this optical signal to the second optical fiber 160.

[0049] The first optical / electrical conversion unit 130 may further include a WDM (Wavelength Division Multiplexing) optical coupler 133, as shown in Figure 10. In this case, the radar system 100 has one optical fiber 180 instead of the first optical fiber 120 and the second optical fiber 160.

[0050] The WDM optical coupler 133 is connected between one optical fiber 180 and the optical / electrical converter 131 and the electrical / optical converter 132, and receives the optical signal output by the optical signal generator 110 and transmitted through the first optical fiber 120, and the optical signal output from the electrical / optical converter 132. The WDM optical coupler 133 outputs the optical signal input from the optical fiber 180 to the optical / electrical converter 131, and outputs the optical signal input from the electrical / optical converter 132 to the optical fiber 180.

[0051] At this time, a WDM optical coupler 190 is also connected between the optical fiber 180 and the optical signal generator 110 and the second optical / electrical conversion unit 170, as shown in Figure 10. The WDM optical coupler 190 receives the optical signal output from the optical signal generator 110 and the optical signal output from the electrical / optical converter 132 and transmitted through the optical fiber 180 as input. The WDM optical coupler 190 outputs the optical signal input from the optical signal generator 110 to the optical fiber 180 and outputs the optical signal input from the optical fiber 180 to the second optical / electrical conversion unit 170.

[0052] <Signal mixing section 150>

[0053] The signal mixing unit 150 includes, for example, a multiplexer 151 and a detector 152, as shown in Figure 11.

[0054] The multiplexer 151 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 151 are connected to the electromagnetic wave transmitting and receiving unit 140.

[0055] The detector 152 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 152 is connected to the multiplexer 151, and the output port of the detector 152 is connected to the first optical / electrical conversion unit 130.

[0056] As shown in Figure 12, the incident signal and reflected signal output from the electromagnetic wave transmitting / receiving unit 140 are input to the two input ports of the multiplexer 151. These input incident and reflected signals are then output from the output port of the multiplexer 151 to the detector 152. The detector 152 receives the incident and reflected signals output from the multiplexer 151, mixes these input incident and reflected signals, and outputs this mixed electrical signal (mixed signal) to the first electrical / optical conversion unit 130.

[0057] The signal mixing unit 150 may also include a mixer 153, as shown in Figure 13.

[0058] The mixer 153 has two input ports and one output port. As shown in Figure 13, the incident signal and reflected signal output from the electromagnetic wave transmitting / receiving unit 140 are input to the two input ports of the mixer 153. The mixer 153 mixes these input incident and reflected signals and outputs this mixed electrical signal (mixed signal) to the first electrical / optical conversion unit 130.

[0059] <Electromagnetic wave transmitting / receiving unit 140 and signal mixing unit 150> The electromagnetic wave transceiver 140 may also include a transmitting / receiving antenna 141TR, a splitter 142, and a bidirectional coupler 145, as shown in Figure 14. In this case, the signal mixing unit 150 may include a detector 152.

[0060] The bidirectional coupler 145 has an input port 1451, an output port 1452, a coupling port 1453, and an isolation port 1454. The bidirectional coupler 145 is a so-called bidirectional coupler with four ports and has a symmetrical structure.

[0061] The bidirectional coupler 145 outputs a portion of the electrical signal input from the input port 1451 from the output port 1452, and the remaining electrical signal from the coupling port 1453. Furthermore, the bidirectional coupler 145 outputs a portion of the electrical signal input from the output port 1452 from the input port 1451, and the remaining electrical signal from the isolation port 1454. Also, the bidirectional coupler 145 outputs a portion of the electrical signal input from the coupling port 1453 from the input port 1451, and the remaining electrical signal from the isolation port 1454. Finally, the bidirectional coupler 145 outputs a portion of the electrical signal input from the isolation port 1454 from the output port 1452, and the remaining electrical signal from the coupling port 1453.

[0062] In the example shown in Figure 14, the input port 1421 of the branch switch 142 is connected to the first optical / electrical converter 130, the first output port 1422 of the branch switch 142 is connected to the coupling port 1453 of the bidirectional coupler 145, and the second output port 1423 of the branch switch 142 is connected to the isolation port 1454 of the bidirectional coupler 145. The input port 1451 of the bidirectional coupler 145 is connected to the transmitting / receiving antenna 141TR, and the output port 1452 of the bidirectional coupler 145 is connected to the detector 152.

[0063] Therefore, in the example shown in Figure 14, as shown in Figure 15, the incident signal output from the first output port 1422 of the brancher 142 is input to the coupling port 1453 of the bidirectional coupler 145, and the incident signal output from the second output port 1423 of the brancher 142 is input to the isolation port 1454 of the bidirectional coupler 145. The incident signal input to the coupling port 1453 of the bidirectional coupler 145 is output from the input port 1451 of the bidirectional coupler 145 and 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 incident signal input to the isolation port 1454 of the bidirectional coupler 145 is output from the output port 1452 of the bidirectional coupler 145 and input to the detector 152. The reflected signal (an electrical signal at the frequency of the reflected wave) output from the transmitting / receiving antenna 141TR, which receives the electromagnetic wave (reflected wave), is input to the input port 1451 of the bidirectional coupler 145, as shown in Figure 14. The reflected signal input to the input port 1451 of the bidirectional coupler 145 is output from the output port 1452 of the bidirectional coupler 145 and input to the detector 152.

[0064] 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]

[0065] 100 Radar Systems 110 Optical signal generator 120 First optical fiber 130 First optical / electrical conversion unit 131 Optical / Electric Converter 132 Electrical / Optical Converter 133 WDM optical coupler 140 Electromagnetic wave transmitting and receiving unit 141T Transmitting Antenna 141R Receiving Antenna 141TR Transceiver Antenna 142 Turnout 1421 Input port of branch switch 142 1422 First output port of turnout 142 1423 Second output port of turnout 142 143 Circulator 1431 First port of circulator 143 1432 Second port of circulator 143 1433 Third port of Circulator 143 144 Unidirectional Coupler 1441 Input port of unidirectional coupler 144 1442 Output port of unidirectional coupler 144 1443 Coupling port of unidirectional coupler 144 145 Bidirectional coupler 1451 Input port of bidirectional coupler 145 1452 Output port of bidirectional coupler 145 1453 Coupler port of bidirectional coupler 145 1454 Isolation port of bidirectional coupler 145 150 Signal mixing section 151 Multiplexer 152 Detector 153 Mixer 160 Second optical fiber 170 Second Optical / Electric Conversion Unit 180 optical fibers 190 WDM optical coupler

Claims

1. A first photoelectric / electrical conversion unit that generates an incident signal based on an optical signal, An electromagnetic wave transmitting and receiving unit that transmits and receives electromagnetic waves, the electromagnetic wave transmitting and receiving unit that transmits electromagnetic waves based on the incident signal and outputs a reflected signal and the incident signal based on the received electromagnetic waves, The system includes a signal mixing unit that mixes the incident signal and the reflected signal output from the electromagnetic wave transmitting / receiving unit and outputs the mixed signal, The first optical / electrical conversion unit generates an optical signal based on the mixed signal output by the signal mixing unit, in a radar system.

2. The electromagnetic wave transmitting and receiving unit is A transmitting antenna that transmits electromagnetic waves, A receiving antenna that receives electromagnetic waves, A branching switch having an input port, a first output port, and a second output port, The incident signal generated by the first optical / electrical conversion unit is input to the input port of the branching switch. The first output port of the aforementioned branch is connected to the transmitting antenna, The radar system according to claim 1, wherein the signal mixing unit mixes an incident signal output from the second output port of the branching unit with a reflected signal based on electromagnetic waves received by the receiving antenna.

3. The electromagnetic wave transmitting and receiving unit is A transmitting and receiving antenna that sends and receives electromagnetic waves, A branching switch having an input port, a first output port, and a second output port, A circulator having a first port, a second port, and a third port, The incident signal generated by the first optical / electrical conversion unit is input to the input port of the branching switch. The first output port of the aforementioned branch is connected to the first port of the aforementioned circulator. The second port of the circulator is connected to the transmitting and receiving antenna. The radar system according to claim 1, wherein the signal mixing unit mixes the incident signal output from the second output port of the branching unit with the reflected signal output from the third port of the circulator.

4. The electromagnetic wave transmitting and receiving unit is A transmitting and receiving antenna that sends and receives electromagnetic waves, A branching switch having an input port, a first output port, and a second output port, A unidirectional coupler having an input port, an output port, and a coupling port, The incident signal generated by the first optical / electrical conversion unit is input to the input port of the branching switch. The first output port of the aforementioned branch is connected to the coupling port of the aforementioned unidirectional coupler. The input port of the unidirectional coupler is connected to the transmitting and receiving antenna. The radar system according to claim 1, wherein the signal mixing unit mixes the incident signal output from the second output port of the branching unit with the reflected signal output from the output port of the unidirectional coupler.

5. The electromagnetic wave transmitting and receiving unit is A transmitting and receiving antenna that sends and receives electromagnetic waves, A branching switch having an input port, a first output port, and a second output port, A bidirectional coupler having an input port, an output port, a coupling port, and an isolation port, The signal mixing unit has a detector having an input port and an output port. The incident signal generated by the first optical / electrical conversion unit is input to the input port of the branching switch. The first output port of the aforementioned branch is connected to the coupling port of the aforementioned bidirectional coupler. The second output port of the aforementioned branch is connected to the isolation port of the aforementioned bidirectional coupler. The input port of the bidirectional coupler is connected to the transmitting and receiving antenna, The radar system according to claim 1, wherein the output port of the bidirectional coupler is connected to the input port of the detector.

6. An optical signal generator that outputs an optical signal of a first frequency and an optical signal of a second frequency, A first optical fiber that transmits the optical signal output by the optical signal generator, The device further comprises a second optical fiber for transmitting the optical signal output from the first optical / electrical conversion unit, The first optical / electrical conversion unit is, An optical / electric converter that generates the incident signal based on the optical signal transmitted by the first optical fiber, A radar system according to any one of claims 1 to 5, comprising: an electrical / optical converter that generates an optical signal based on a mixed signal output by the signal mixing unit.

7. An optical signal generator that outputs an optical signal of a first frequency and an optical signal of a second frequency, The system further includes an optical fiber for transmitting the optical signal output by the optical signal generator and the optical signal output from the first optical / electrical conversion unit, The first optical / electrical conversion unit is, An optical / electrical converter that generates the incident signal based on the optical signal output by the optical signal generator, An electro-optical converter that generates an optical signal based on the mixed signal output by the signal mixing unit, A radar system according to any one of claims 1 to 5, comprising the optical fiber, the optical / electrical converter, and a WDM optical coupler connected between the electrical / optical converter.

Images