Transmission circuit

Abstract

To miniaturize backscatter type wireless communication devices. [Solution] The transmission circuit includes at least two backscatter circuits and a control circuit that controls the reflection coefficients of the backscatter circuits at different rotational frequencies.

Description

Technical Field

[0001] The present disclosure relates to a transmission circuit.

Background Art

[0002] As a data communication method of a wireless communication device, a backscatter method is known. For example, Patent Document 1 discloses a technique for realizing a single sideband by suppressing either a USB (Upper Side Band) signal or an LSB (Lower Side Band) signal using a diplexer / combiner.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an RFID (Radio Frequency Identification) system that performs data communication using the backscatter method, miniaturization of a wireless communication device is required. However, since Patent Document 1 uses a diplexer / combiner to realize a single sideband, it has a configuration that is disadvantageous for miniaturization.

[0005] An object of the present disclosure is to provide a transmission circuit capable of miniaturizing a wireless communication device using the backscatter method.

Means for Solving the Problems

[0006] The transmission circuit of the present disclosure includes at least two backscatter circuits and a control circuit that controls the reflection coefficients of the backscatter circuits at different rotation frequencies.

Effects of the Invention

[0007] This disclosure enables miniaturization of backscatter type wireless communication devices. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the configuration of a communication system according to the first embodiment. [Figure 2] Figure 2 is a block diagram showing an example configuration of a slave unit according to the first embodiment. [Figure 3] Figure 3 shows an example of the configuration of an impedance rotation circuit according to the first embodiment. [Figure 4] Figure 4 shows an example of the configuration of a backscatter circuit according to the first embodiment. [Figure 5] Figure 5 is a diagram illustrating the signal level of the reflected signal according to the first embodiment. [Figure 6] Figure 6 is a diagram illustrating the signal level of the reflected signal according to the first embodiment. [Figure 7] Figure 7 shows an example of the antenna configuration according to the second embodiment. [Figure 8] Figure 8 is a diagram illustrating the signal level of the reflected signal according to the second embodiment. [Figure 9] Figure 9 shows an example of the configuration of an impedance rotation circuit according to the third embodiment. [Figure 10] Figure 10 shows an example of the configuration of a synthesis circuit according to the third embodiment. [Figure 11] Figure 11 is a diagram illustrating the signal level of the reflected signal according to the third embodiment. [Figure 12] Figure 12 shows an example of the configuration of an impedance rotation circuit according to the fourth embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present disclosure is not limited by this embodiment, and in the following embodiments, the same parts are denoted by the same reference numerals to omit redundant explanations.

[0010] [Communication System] Using FIG. 1, a configuration example of the communication system according to the first embodiment will be described. FIG. 1 is a diagram showing a configuration example of the communication system according to the first embodiment.

[0011] As shown in FIG. 1, the communication system 1 includes a master unit 10, slave units 12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12I, and 12J. When there is no need to distinguish between slave units 12A to 12J, they are collectively referred to as slave unit 12. The communication system 1 is a system that performs data communication using the backscatter method. The master unit 10 and the slave unit 12 are wireless communication devices that perform backscatter communication. In the communication system 1, the slave unit 12 is configured to transmit a reflected signal 22 obtained by reflecting a transmission signal 21 transmitted by the master unit to the master unit 10.

[0012] [Slave Unit] Using FIG. 2, a configuration example of the slave unit according to the first embodiment will be described. FIG. 2 is a block diagram showing a configuration example of the slave unit according to the first embodiment.

[0013] As shown in FIG. 2, the slave unit 12 includes an antenna 40, a switch (SW) 41, a reception circuit 42, a transmission circuit 43, a control unit 44, and a sensor 45.

[0014] The antenna 40 is configured to receive a transmission signal transmitted by the master unit 10. The antenna 40 is configured to transmit a reflected signal obtained by reflecting the transmission signal to the master unit 10.

[0015] Switch 41 is configured to be able to switch the path between antenna 40, receiving circuit 42, and transmitting circuit 43. When antenna 40 receives the transmission signal from master unit 10, switch 41 electrically connects antenna 40 and receiving circuit 42. When antenna 40 transmits a reflected signal to master unit 10, switch 41 electrically connects antenna 40 and transmitting circuit 43.

[0016] Receiving circuit 42 receives the transmission signal from master unit 10 received by antenna 40. Receiving circuit 42 is configured to perform various receiving processes on the transmission signal.

[0017] Transmitting circuit 43 is a circuit that generates a reflected signal (also called a backscatter signal) transmitted by antenna 40. Transmitting circuit 43 includes a CPU interface (I / F) 60, a control circuit 61, an impedance rotation circuit 62, and a PLL (Phase Looked Loop) circuit 63.

[0018] CPU interface 60 is configured to receive various control signals and data from control unit 44.

[0019] Control circuit 61 is configured to control impedance rotation circuit 62. Control circuit 61 controls impedance rotation circuit 62 based on control signals input from control unit 44 via CPU interface 60, oscillation signals input from PLL circuit 63, etc. Control circuit 61 is configured to change the impedance of impedance rotation circuit 62. By changing the impedance of impedance rotation circuit 62, the reflection coefficient of the output terminal on the antenna 40 side rotates in the complex plane. That is, control circuit 61 changes the impedance of impedance rotation circuit 62 to control the reflection coefficient of the output terminal on the antenna 40 side to rotate in the complex plane. Control circuit 61, for example, reduces the USB (Upper Side Band) signal or LSB signal (Lower Side Band) with respect to the carrier signal of the backscatter signal to achieve single sideband.

[0020] The impedance rotation circuit 62 is located at the front end of the slave unit 12. The impedance rotation circuit 62 is configured to perform backscatter communication by reflecting the transmission signal sent by the master unit 10 as a backscatter signal. Specifically, as will be described later, the impedance rotation circuit 62 includes multiple impedance circuits, each with a different impedance.

[0021] The control circuit 61 and the impedance rotation circuit 62 are types of transmission circuits according to this disclosure.

[0022] The PLL circuit 63 is configured to generate an oscillation signal of a predetermined frequency. The PLL circuit 63 generates the oscillation signal according to the control signal from the control unit 44. The PLL circuit 63 is configured to output the generated oscillation signal to the control circuit 61.

[0023] The control unit 44 is configured to control each part of the slave unit 12. The control unit 44 may be implemented, for example, by an information processing device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) and a storage device such as RAM (Random Access Memory) or ROM (Read Only Memory). The control unit 44 may be implemented, for example, by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The control unit 44 may be implemented by a combination of hardware and software.

[0024] Sensor 45 includes various types of sensors. Sensor 45 may include, for example, speed sensors, vibration sensors, acceleration sensors, gyro sensors, rotation angle sensors, angular velocity sensors, geomagnetic sensors, magnet sensors, temperature sensors, humidity sensors, pressure sensors, light sensors, illuminance sensors, UV sensors, gas sensors, gas concentration sensors, atmosphere sensors, level sensors, odor sensors, pressure sensors, air pressure sensors, contact sensors, wind sensors, infrared sensors, motion sensors, displacement sensors, image sensors, weight sensors, smoke sensors, leak sensors, vital sensors, battery level sensors, and ultrasonic sensors. Sensor 45 may also include a GNSS (Global Navigation Satellite System) sensor to acquire the current location information of the slave unit 12.

[0025] (Impedance rotation circuit) An example of the configuration of the impedance rotation circuit according to the first embodiment will be explained using Figure 3. Figure 3 is a diagram showing an example of the configuration of the impedance rotation circuit according to the first embodiment.

[0026] As shown in Figure 3, the impedance rotation circuit 62 includes a first backscatter circuit 101 and a second backscatter circuit 102.

[0027] The input terminal of the first backscatter circuit 101 is electrically connected to the first output terminal of the control circuit 61. The output terminal of the first backscatter circuit 101 is electrically connected to the antenna 40a. The first backscatter circuit 101 outputs a first backscatter signal to the antenna 40a.

[0028] The input terminal of the second backscatter circuit 102 is electrically connected to the second output terminal of the control circuit 61. The output terminal of the second backscatter circuit 102 is electrically connected to the antenna 40b. The second backscatter circuit 102 outputs a second backscatter signal to the antenna 40b.

[0029] The first backscatter signal and the second backscatter signal are reflected signals of different frequencies.

[0030] The control circuit 61 controls the reflection coefficients of the first backscatter circuit 101 and the second backscatter circuit 102 at different rotational frequencies. In the example shown in Figure 3, the impedance rotation circuit 62 includes two backscatter circuits, but the disclosure is not limited to this; the impedance rotation circuit 62 only needs to include at least two backscatter circuits.

[0031] (Backscatter circuit) An example of the configuration of a backscatter circuit according to the first embodiment will be explained using Figure 4. Figure 4 is a diagram showing an example of the configuration of a backscatter circuit according to the first embodiment.

[0032] As shown in Figure 4, the first backscatter circuit 101 includes an inductor circuit 1101, an inductor circuit 1102, an inductor circuit 1103, a capacitor circuit 1201, a capacitor circuit 1202, a capacitor circuit 1203, and a resistor circuit 130. The configuration of the second backscatter circuit 102 is the same as that of the first backscatter circuit 101, so its description is omitted. Inductor circuits 1101 to 1103, capacitor circuits 1201 to 1203, and resistor circuit 130 are all types of impedance circuits. When there is no need to distinguish between inductor circuits 1101 to 1103, they may be collectively referred to as inductor circuit 110. When there is no need to distinguish between capacitor circuits 1201 to 1203, they may be collectively referred to as capacitor circuit 120. In Figure 4, components that are not particularly relevant to this disclosure are omitted.

[0033] The inductor circuit 1101 to inductor circuit 1103, the capacitor circuit 1201 to capacitor circuit 1203, and the resistor circuit 130 are each electrically connected by a signal line 160. The signal line 160 is electrically connected to the input / output terminal 161. The input / output terminal 161 is electrically connected to the peripheral circuits on the antenna 40a side.

[0034] The inductor circuit 1101 includes a signal source 1401, a switch element 1501, and an inductor L1. The signal source 1401 is a signal source to which a control signal from the control circuit 61 is supplied. The signal source 1401 is configured to output a control signal to the switch element 1501 to control the opening and closing operation of the switch element 1501. The switch element 1501 has the signal source 1401 connected to one input terminal and a reference potential connected to the other input terminal. The reference potential will be described as ground, but this disclosure is not limited thereto. The switch element 1501 is configured to switch between a closed state and an open state according to the control signal from the signal source 1401.

[0035] One end of the switch element 1501 is electrically connected to the signal line 160, and the other end is electrically connected to one end of the inductor L1. The other end of the inductor L1 is connected to a reference potential. In this case, the switch element 1501 is configured to electrically connect the signal line 160 and the inductor L1 when in the closed state. The switch element 1501 is configured to electrically separate the signal line 160 and the inductor L1 when in the open state. When the signal line 160 and the inductor L1 are electrically connected, the inductance of the inductor L1 is added to the impedance of the first backscatter circuit 101. That is, the reactance component of the impedance of the first backscatter circuit 101 changes as the inductance of the inductor L1 is added.

[0036] The inductor circuit 1102 includes a signal source 1402, a switch element 1502, and an inductor L2. The signal source 1402 is a signal source to which control signals from the control circuit 61 are supplied. The signal source 1402 is configured to output control signals to the switch element 1502 to control the opening and closing operation of the switch element 1502. The switch element 1502 has the signal source 1402 connected to one input terminal and a reference potential connected to the other input terminal. The reference potential will be described as ground, but this disclosure is not limited thereto. The switch element 1502 is configured to switch between a closed state and an open state according to the control signals from the signal source 1402.

[0037] One end of the switch element 1502 is electrically connected to the signal line 160, and the other end is electrically connected to one end of the inductor L2. The other end of the inductor L2 is connected to a reference potential. In this case, the switch element 1502 is configured to electrically connect the signal line 160 and the inductor L2 when in the closed state. The switch element 1502 is configured to electrically separate the signal line 160 and the inductor L2 when in the open state. When the signal line 160 and the inductor L2 are electrically connected, the inductance of the inductor L2 is added to the impedance of the first backscatter circuit 101. That is, the reactance component of the impedance of the first backscatter circuit 101 changes as the inductance of the inductor L2 is added.

[0038] The inductor circuit 1103 includes a signal source 1403, a switch element 1503, and an inductor L3. The signal source 1403 is a signal source to which control signals from the control circuit 61 are supplied. The signal source 1403 is configured to output control signals to the switch element 1503 to control the opening and closing operation of the switch element 1503. The switch element 1503 has the signal source 1403 connected to one input terminal and a reference potential connected to the other input terminal. The reference potential is described as ground, but this disclosure is not limited thereto. The switch element 1503 is configured to switch between a closed state and an open state according to the control signals from the signal source 1403. Note that one or more switch circuits from inductor circuits 1101 to 1103 may include one or more electrical elements from a plurality of capacitor elements and a plurality of resistor elements.

[0039] One end of the switch element 1503 is electrically connected to the signal line 160, and the other end is electrically connected to one end of the inductor L3. The other end of the inductor L3 is connected to a reference potential. In this case, the switch element 1503 is configured to electrically connect the signal line 160 and the inductor L3 when in the closed state. The switch element 1503 is configured to electrically separate the signal line 160 and the inductor L3 when in the open state. When the signal line 160 and the inductor L3 are electrically connected, the inductance of the inductor L3 is added to the impedance of the first backscatter circuit 101. That is, the reactance component of the impedance of the first backscatter circuit 101 changes as the inductance of the inductor L3 is added.

[0040] The capacitor circuit 1201 includes a signal source 1404, a switch element 1504, and a capacitor C1. The signal source 1404 is a signal source to which a control signal from the control circuit 61 is supplied. The signal source 1404 is configured to output a control signal to the switch element 1504 to control the opening and closing operation of the switch element 1504. The switch element 1504 has the signal source 1404 connected to one input terminal and a reference potential connected to the other input terminal. The reference potential will be described as ground, but this disclosure is not limited thereto. The switch element 1504 is configured to switch between a closed state and an open state according to the control signal from the signal source 1404.

[0041] One end of the switch element 1504 is electrically connected to the signal line 160, and the other end is electrically connected to one end of the capacitor C1. The other end of the capacitor C1 is connected to a reference potential. In this case, the switch element 1504 is configured to electrically connect the signal line 160 and the capacitor C1 when in the closed state. The switch element 1504 is configured to electrically disconnect the signal line 160 and the capacitor C1 when in the open state. When the signal line 160 and the capacitor C1 are electrically connected, the capacitance of the capacitor C1 is added to the impedance of the first backscatter circuit 101. That is, the reactance component of the impedance of the first backscatter circuit 101 changes as the capacitance of the capacitor C1 is added.

[0042] The capacitor circuit 1202 includes a signal source 1405, a switch element 1505, and a capacitor C2. The signal source 1405 is a signal source to which a control signal from the control circuit 61 is supplied. The signal source 1405 is configured to output a control signal to the switch element 1505 to control the opening and closing operation of the switch element 1505. The switch element 1505 has the signal source 1405 connected to one input terminal and a reference potential connected to the other input terminal. The reference potential will be described as ground, but this disclosure is not limited thereto. The switch element 1505 is configured to switch between a closed state and an open state according to the control signal from the signal source 1405.

[0043] One end of the switch element 1505 is electrically connected to the signal line 160, and the other end is electrically connected to one end of the capacitor C2. The other end of the capacitor C2 is connected to a reference potential. In this case, the switch element 1505 is configured to electrically connect the signal line 160 and the capacitor C2 when in the closed state. The switch element 1505 is configured to electrically disconnect the signal line 160 and the capacitor C2 when in the open state. When the signal line 160 and the capacitor C2 are electrically connected, the capacitance of the capacitor C2 is added to the impedance of the first backscatter circuit 101. That is, the reactance component of the impedance of the first backscatter circuit 101 changes as the capacitance of the capacitor C2 is added.

[0044] The capacitor circuit 1203 includes a signal source 1406, a switch element 1506, and a capacitor C3. The signal source 1406 is a signal source to which control signals from the control circuit 61 are supplied. The signal source 1406 is configured to output control signals to the switch element 1506 to control the opening and closing operation of the switch element 1506. The switch element 1506 has the signal source 1406 connected to one input terminal and a reference potential connected to the other input terminal. The reference potential is described as ground, but this disclosure is not limited thereto. The switch element 1506 is configured to switch between a closed state and an open state according to the control signals from the signal source 1406. Note that one or more of the capacitor circuits from capacitor circuits 1201 to capacitor circuits 1203 may include one or more electrical elements from a plurality of inductors and a plurality of resistors.

[0045] One end of the switch element 1506 is electrically connected to the signal line 160, and the other end is electrically connected to one end of the capacitor C3. The other end of the capacitor C3 is connected to a reference potential. In this case, the switch element 1506 is configured to electrically connect the signal line 160 and the capacitor C3 when in the closed state. The switch element 1506 is configured to electrically separate the signal line 160 and the capacitor C3 when in the open state. When the signal line 160 and the capacitor C3 are electrically connected, the capacitance of the capacitor C3 is added to the impedance of the first backscatter circuit 101. That is, the reactance component of the impedance of the first backscatter circuit 101 changes as the capacitance of the capacitor C3 is added.

[0046] The resistor circuit 130 includes a signal source 1407, a switch element 1507, and a resistor element R1. The signal source 1407 is a signal source to which a control signal from the control circuit 61 is supplied. The signal source 1407 is configured to output a control signal to the switch element 1507 to control the opening and closing operation of the switch element 1507. The switch element 1507 has the signal source 1407 connected to one input terminal and a reference potential connected to the other input terminal. The reference potential will be described as ground, but this disclosure is not limited thereto. The switch element 1507 is configured to switch between a closed state and an open state according to the control signal from the signal source 1407.

[0047] One end of the switch element 1507 is electrically connected to the signal line 160, and the other end is electrically connected to one end of the resistor element R1. The other end of the resistor element R1 is connected to a reference potential. In this case, the switch element 1507 is configured to electrically connect the signal line 160 and the resistor element R1 when it is in the closed state. The switch element 1507 is configured to electrically separate the signal line 160 and the resistor element R1 when it is in the open state. When the signal line 160 and the resistor element R1 are electrically connected, the resistance value of the resistor element R1 is added to the impedance of the first backscatter circuit 101. That is, the real part component of the impedance of the first backscatter circuit 101 changes as the resistance value of the resistor element R1 is added.

[0048] The control circuit 61 is configured to selectively change the impedance of the first backscatter circuit 101 and rotate the reflection coefficient on the polar chart by selectively controlling the open / closed state of each of the switch elements 1501 to 1507. The control circuit 61 is configured to rotate the impedance of the first backscatter circuit 101 in the complex plane by closing any one of the switch elements 1501 to 1507 or by opening all of the switch elements. Alternatively, the control circuit 61 may be controlled to rotate the reflection coefficient by selecting the impedance of the first backscatter circuit 101 by closing multiple switch elements from 1501 to 1507.

[0049] Specifically, when all switch elements from switch element 1501 to switch element 1507 are in the open state, the first backscatter circuit 101 is configured such that the reflection coefficient is located at 0° in the complex plane. When only switch element 1503 is in the closed state, the first backscatter circuit 101 is configured such that the impedance is located at 45° in the complex plane. When only switch element 1502 is in the closed state, the first backscatter circuit 101 is configured such that the impedance is located at 90° in the complex plane. When only switch element 1501 is in the closed state, the first backscatter circuit 101 is configured such that the impedance is located at 135° in the complex plane. When only switch element 1504 is in the closed state, the first backscatter circuit 101 is configured such that the impedance is located at -45° in the complex plane. When only switch element 1505 is in the closed state, the first backscatter circuit 101 is configured such that the impedance is located at -90° in the complex plane. When only switch element 1506 is closed, the first backscatter circuit 101 is configured such that its impedance is located at -135° in the complex plane. When only switch element 1507 is closed, the first backscatter circuit 101 is configured such that its impedance is located at 180° in the complex plane.

[0050] The control circuit 61 may be configured to control the open / closed state of predetermined switch elements among switch elements 1501 to 1507 when reflecting a transmission signal from the master unit 10. The control circuit 61 may be configured to control switch elements 1501 to 1507 so that the impedance is located at the rotational position in the complex plane, in accordance with the output from the control unit 44. The control circuit 61 may be configured to control switch elements 1501 to 1507 so that the impedance is located at the rotational position in the complex plane, based on a control signal transmitted from outside the slave unit 12.

[0051] Refer to Figure 3 again. The control circuit 61 controls the reflection coefficients of the first backscatter circuit 101 and the second backscatter circuit 102 in the complex plane at different rotation frequencies.

[0052] The control circuit 61 controls the rotation direction of the reflection coefficient in the complex plane of at least one of the multiple backscatter circuits included in the impedance rotation circuit 62 in the opposite direction to the rotation direction of the reflection coefficients in the complex plane of the other backscatter circuits. In the example shown in Figure 3, the control circuit 61 controls the rotation direction of the reflection coefficients in the complex plane of the first backscatter circuit 101 and the second backscatter circuit 102 in opposite directions. Specifically, the control circuit 61 controls the reflection coefficient in the complex plane of the first backscatter circuit 101 to rotate to 0°, 45°, 90°, 135°, 180°, -135°, -90°, -45°, and 0°. The control circuit 61 controls the reflection coefficient of the second backscatter circuit 102 in the complex plane to rotate to 0°, -45°, -90°, -135°, 180°, 135°, 90°, 45°, and 0°. By controlling the rotation direction of the reflection coefficients in the complex plane of the first backscatter circuit 101 and the second backscatter circuit 102 in opposite directions, the control circuit 61 achieves single-sideband reflection of each reflected signal.

[0053] (Signal level of reflected signal) The signal level of the reflected signal according to the first embodiment will be explained using Figures 5 and 6. Figures 5 and 6 are diagrams that illustrate the signal level of the reflected signal according to the first embodiment.

[0054] Figure 5 shows frequency [GHz (gigahertz)] on the horizontal axis and signal level [dB (decibels)] on the vertical axis. Figure 5 shows the USB signal 201. The USB signal 201 is the first backscatter signal output by the first backscatter circuit 101. The control circuit 61 can suppress the signal level of the LSB signal by controlling the rotation direction of the reflection coefficient in the complex plane of the first backscatter circuit 101 to rotate to 0°, 45°, 90°, 135°, 180°, -135°, -90°, -45°, and 0°. As a result, as shown in Figure 5, the control circuit 61 can realize a single sideband containing only the USB signal 201 with the first backscatter signal.

[0055] Figure 6 shows frequency [GHz] on the horizontal axis and signal level [dB] on the vertical axis. Figure 6 shows the LSB signal 202. The LSB signal 202 is the second backscatter signal output by the second backscatter circuit 102. The control circuit 61 can suppress the signal level of the USB signal by controlling the rotation direction of the reflection coefficient in the complex plane of the second backscatter circuit 102 to rotate to 0°, -45°, -90°, -135°, 180°, 135°, 90°, 45°, and 0°. As a result, as shown in Figure 6, the control circuit 61 can realize a single sideband containing only the LSB signal 202 with the second backscatter signal.

[0056] As described above, the first embodiment can achieve single-sideband reflection of the reflected signal by controlling the rotation direction of the reflection coefficients in the complex plane of the first backscatter circuit 101 and the second backscatter circuit 102 in opposite directions. Furthermore, in the first embodiment, achieving single-sideband reflection improves frequency utilization efficiency and enables higher communication rates.

[0057] [Second Embodiment] An antenna according to the second embodiment will be described using Figure 7. Figure 7 is a diagram showing an example of the configuration of an antenna according to the second embodiment.

[0058] As shown in Figure 7, the slave unit 12a differs from the slave unit 12 shown in Figure 3 in that it includes a dipole antenna 40A instead of the antenna 40.

[0059] The output terminal of the first backscatter circuit 101 is electrically connected to the dipole antenna 40A. The first backscatter circuit 101 transmits a first backscatter signal to the dipole antenna 40A.

[0060] The output terminal of the second backscatter circuit 102 is electrically connected to the dipole antenna 40A. The second backscatter circuit 102 transmits a second backscatter signal to the dipole antenna 40A.

[0061] The dipole antenna 40A combines the first backscatter signal output from the first backscatter circuit 101 and the second backscatter signal output from the second backscatter circuit 102.

[0062] In the second embodiment, the control circuit 61 preferably phase-shifts the impedance position when rotating the reflection coefficients in the complex plane of the first backscatter circuit 101 and the second backscatter circuit 102. The amount of phase shift is, for example, 90°±45° or -90°±45°, but is not limited thereto. Specifically, the control circuit 61 controls the reflection coefficient in the complex plane of the first backscatter circuit 101 to rotate as follows: 0°, 45°, 90°, 135°, 180°, -135°, -90°, -45°, 0°. The control circuit 61 also controls the reflection coefficient in the complex plane of the second backscatter circuit 102 to rotate as follows: -90°, -135°, 180°, 135°, 90°, 45°, 0°, -45°, -90°. The control circuit 61 achieves single-sideband reflection of the reflected signal by phase-shifting the impedance position of the reflection coefficient in the complex plane of the first backscatter circuit 101 and the second backscatter circuit 102, and by controlling their rotation directions in opposite directions.

[0063] (Signal level of reflected signal) The signal level of the reflected signal according to the second embodiment will be explained using Figure 8. Figure 8 is a diagram illustrating the signal level of the reflected signal according to the second embodiment.

[0064] Figure 8 shows frequency [GHz] on the horizontal axis and signal level [dB] on the vertical axis. Figure 8 shows the USB signal 211 and the LSB signal 212. The USB signal 211 is the first backscatter signal output by the first backscatter circuit 101. The LSB signal 212 is the second backscatter signal output by the second backscatter circuit 102. In the second embodiment, the control circuit 61 can realize single-sideband operation for the USB signal 211 and the LSB signal 212 by phase-shifting the impedance positions of the reflection coefficients in the complex plane between the first backscatter circuit 101 and the second backscatter circuit 102, and controlling their rotation directions in opposite directions.

[0065] As described above, in the second embodiment, single-sideband operation can be achieved using a dipole antenna configuration. This eliminates the need to prepare an antenna for each backscatter circuit in the second embodiment, thus allowing for miniaturization.

[0066] [Third Embodiment] (Impedance rotation circuit) An example of the configuration of the impedance rotation circuit according to the third embodiment will be explained using Figure 9. Figure 9 is a diagram showing an example of the configuration of the impedance rotation circuit according to the third embodiment.

[0067] As shown in Figure 9, the slave unit 12b includes an impedance rotation circuit 62A. The impedance rotation circuit 62A includes a first backscatter circuit 101, a second backscatter circuit 102, and a combining circuit 170. The impedance rotation circuit 62A differs from the impedance rotation circuit 62 shown in Figure 3 in that it includes the combining circuit 170.

[0068] The output terminal of the first backscatter circuit 101 is electrically connected to the first input terminal of the combining circuit 170. The first backscatter circuit 101 outputs a first backscatter signal to the combining circuit 170.

[0069] The output terminal of the second backscatter circuit 102 is electrically connected to the second input terminal of the combining circuit 170. The second backscatter circuit 102 outputs a second backscatter signal to the combining circuit 170.

[0070] The output terminal of the combining circuit 170 is electrically connected to the antenna 40. The combining circuit 170 combines the first backscatter signal output from the first backscatter circuit 101 and the second backscatter signal output from the second backscatter circuit 102 and outputs the combined signal to the antenna 40.

[0071] (Synthesis circuit) An example of the configuration of the synthesis circuit according to the third embodiment will be explained using Figure 10. Figure 10 is a diagram showing an example of the configuration of the synthesis circuit according to the third embodiment.

[0072] As shown in Figure 10, the composite circuit 170 includes an inductor 181, a capacitor 182, and an impedance conversion circuit 183. The inductor 181 and the capacitor 182 constitute a resonant circuit.

[0073] One end of the inductor 181 is electrically connected to the output terminal of the first backscatter circuit 101. The other end of the inductor 181 is electrically connected to the input terminal of the impedance conversion circuit 183.

[0074] One end of capacitor 182 is electrically connected to the output terminal of the second backscatter circuit 102. The other end of capacitor 182 is electrically connected to the input terminal of the impedance conversion circuit 183.

[0075] The impedance conversion circuit 183 is a circuit that converts impedance. The impedance conversion circuit 183 matches the output impedance of the impedance rotation circuit 62A with the input impedance of the antenna 40. The output impedance of the impedance rotation circuit 62A is, for example, 200[Ω], but is not limited to this. The input impedance of the antenna 40 is, for example, 50[Ω], but is not limited to this. In this case, the impedance conversion circuit 183 converts the output impedance of the impedance rotation circuit 62A from 200[Ω] to 50[Ω].

[0076] In the third embodiment, it is preferable that the control circuit 61 phase-shifts the impedance position when rotating the reflection coefficients in the complex plane of the first backscatter circuit 101 and the second backscatter circuit 102. The amount of phase shift is, for example, 90°±45° or -90°±45°, but is not limited thereto. Specifically, the control circuit 61 controls the reflection coefficient in the complex plane of the first backscatter circuit 101 to rotate as follows: 0°, 45°, 90°, 135°, 180°, -135°, -90°, -45°, 0°. The control circuit 61 also controls the reflection coefficient in the complex plane of the second backscatter circuit 102 to rotate as follows: -90°, -135°, 180°, 135°, 90°, 45°, 0°, -45°, -90°. The control circuit 61 achieves single-sideband reflection of the reflected signal by phase-shifting the impedance position of the reflection coefficient in the complex plane of the first backscatter circuit 101 and the second backscatter circuit 102, and by controlling their rotation directions in opposite directions.

[0077] (Signal level of reflected signal) The signal level of the reflected signal according to the third embodiment will be explained using Figure 11. Figure 11 is a diagram illustrating the signal level of the reflected signal according to the third embodiment.

[0078] Figure 11 shows frequency [GHz] on the horizontal axis and signal level [dB] on the vertical axis. Figure 11 shows the USB signal 221 and the LSB signal 222. The USB signal 221 is the first backscatter signal output by the first backscatter circuit 101. The LSB signal 222 is the second backscatter signal output by the second backscatter circuit 102. In the third embodiment, the control circuit 61 can realize single-sideband operation for the USB signal 221 and the LSB signal 222 by phase-shifting the impedance positions of the reflection coefficients in the complex plane between the first backscatter circuit 101 and the second backscatter circuit 102, and controlling their rotation directions in opposite directions.

[0079] As described above, in the third embodiment, single-sideband operation can be achieved by using a combining circuit 170 in the impedance rotation circuit 62A. As a result, the third embodiment can be miniaturized because it does not require an antenna 40 for each backscatter circuit.

[0080] [Fourth Embodiment] (Impedance rotation circuit) An example of the configuration of the impedance rotation circuit according to the fourth embodiment will be explained using Figure 12. Figure 12 is a diagram showing an example of the configuration of the impedance rotation circuit according to the fourth embodiment.

[0081] As shown in Figure 12, the impedance rotation circuit 62B includes a first backscatter circuit 101, a second backscatter circuit 102, a third backscatter circuit 103, a fourth backscatter circuit 104, a combining circuit 170a, and a combining circuit 170b. The impedance rotation circuit 62B differs from the impedance rotation circuit 62 shown in Figure 3 in that it includes a third backscatter circuit 103, a fourth backscatter circuit 104, a combining circuit 170a, and a combining circuit 170b.

[0082] The input terminal of the first backscatter circuit 101 is electrically connected to the first output terminal of the control circuit 61. The output terminal of the first backscatter circuit 101 is electrically connected to the first input terminal of the combining circuit 170a. The first backscatter circuit 101 outputs a first backscatter signal to the combining circuit 170a.

[0083] The input terminal of the second backscatter circuit 102 is electrically connected to the second output terminal of the control circuit 61. The output terminal of the second backscatter circuit 102 is electrically connected to the second input terminal of the combining circuit 170a. The second backscatter circuit 102 outputs a second backscatter signal to the combining circuit 170a.

[0084] The input terminal of the third backscatter circuit 103 is electrically connected to the third output terminal of the control circuit 61. The output terminal of the third backscatter circuit 103 is electrically connected to the first input terminal of the combining circuit 170b. The third backscatter circuit 103 outputs a third backscatter signal to the combining circuit 170b.

[0085] The input terminal of the fourth backscatter circuit 104 is electrically connected to the fourth output terminal of the control circuit 61. The output terminal of the fourth backscatter circuit 104 is electrically connected to the second input terminal of the combining circuit 170b. The fourth backscatter circuit 104 outputs the fourth backscatter signal to the combining circuit 170b.

[0086] The output terminal of the combining circuit 170a is electrically connected to the antenna 40a. The combining circuit 170a combines the first backscatter signal output from the first backscatter circuit 101 and the second backscatter signal output from the second backscatter circuit 102, and outputs the combined signal to the antenna 40a.

[0087] The output terminal of the combining circuit 170b is electrically connected to the antenna 40b. The combining circuit 170b combines the third backscatter signal output from the third backscatter circuit 103 and the fourth backscatter signal output from the fourth backscatter circuit 104 and outputs the combined signal to the antenna 40b.

[0088] The first backscatter signal, the second backscatter signal, the third backscatter signal, and the fourth backscatter signal are all reflected signals of different frequencies.

[0089] The configurations of the combining circuit 170a and the combining circuit 170b are the same as those of the combining circuit 170 shown in Figure 10, so their explanation will be omitted.

[0090] In the fourth embodiment, the control circuit 61 phase-shifts the impedance position of the reflection coefficient in the complex plane between the first backscatter circuit 101 and the second backscatter circuit 102, and controls the rotation direction in the opposite direction. The control circuit 61 also phase-shifts the impedance position of the reflection coefficient in the complex plane between the third backscatter circuit 103 and the fourth backscatter circuit 104, and controls the rotation direction in the opposite direction. As a result, the fourth embodiment can achieve single-sideband at four positions: the first backscatter signal, the second backscatter signal, the third backscatter signal, and the fourth backscatter signal.

[0091] While embodiments of the present disclosure have been described above, the present disclosure is not limited by the content of these embodiments. Furthermore, the aforementioned components include those that are readily conceivable to those skilled in the art, those that are substantially identical, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the embodiments described above. [Explanation of Symbols]

[0092] 1. Communication System 10 Master unit 12 Handset 40, 40a, 40b antennas 40A Dipole Antenna 41 switches 42 Receiving Circuit 43 Transmitter Circuit 44 Control Unit 45 sensors 60 CPU Interfaces 61 Control circuits 62, 62A, 62B Impedance Rotating Circuit 101 First backscatter circuit 102 Second Backscatter Circuit 103 Third Backscatter Circuit 104 Fourth backscatter circuit 110 Inductor Circuit 120 Capacitor Circuit 130 Resistance circuit 140 Signal source 150 Switching elements 160 signal line 161 Input / output terminal 170,170a,170b synthesis circuit 181 Inductor 182 Capacitors 183 Impedance conversion circuit

Claims

1. At least two backscatter circuits, A control circuit for controlling the reflection coefficient of the backscatter circuit at different rotational frequencies, A transmission circuit, including a transmission circuit.

2. The control circuit controls at least one of the backscatter circuits to rotate in the opposite direction to the other backscatter circuits. The transmission circuit according to claim 1.

3. The first backscatter circuit and A second backscatter circuit, which is different from the first backscatter circuit, The system includes the first backscatter circuit and an antenna connected to the second backscatter circuit, The aforementioned control circuit is The first backscatter circuit is controlled to rotate the reflection coefficient in the complex plane, and the second backscatter circuit is controlled to rotate the reflection coefficient in the complex plane in the opposite direction to that of the first backscatter circuit. The transmission circuit according to claim 1.

4. The antenna includes a first antenna connected to the first backscatter circuit and a second antenna connected to the second backscatter circuit. The transmission circuit according to claim 3.

5. The antenna is a dipole antenna connected to the first backscatter circuit and the second backscatter circuit. The transmission circuit according to claim 3.

6. The control circuit controls the phase of the initial position when controlling the reflection coefficient with the first backscatter circuit and the second backscatter circuit to be different. The transmission circuit according to claim 5.

7. A combining circuit is provided between the first backscatter circuit and the second backscatter circuit and the antenna. The transmission circuit according to claim 3.

8. The aforementioned synthesis circuit comprises a resonant circuit equipped with a capacitor and an inductor. The transmission circuit according to claim 7.

9. The combining circuit includes an impedance conversion circuit between the resonant circuit and the antenna. The transmission circuit according to claim 8.

10. The control circuit controls the phase of the initial position when controlling the reflection coefficient with the first backscatter circuit and the second backscatter circuit to be different. The transmission circuit according to claim 9.

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