Driving device and transmitting / receiving device

Abstract

To improve the output stability of a transmitting element against changes in the surrounding environment and to ensure that the transmitting element transmits.SOLUTION: A driving device (10) includes a current source (CS11) configured to generate an output current. The current source is configured to periodically perform the following operations: to increase a current value of the output current from a first current value in a non-transmission region where the transmitting element (11A) does not transmit to a second current value greater than a current value in a transmission possible region where the transmitting element can transmit, within 1 nanosecond; to drive the transmitting element with the output current of the second current value; to decrease the current value of the output current from the second current value, to a third current value in the transmission possible region; to drive the transmitting element with the output current of the third current value; and to decrease the current value of the output current from the third current value to the first current value.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a driving device and a transmitting / receiving device. [Background technology]

[0002] Conventionally, attempts have been made to perform high-capacity communication, information processing, imaging, measurement, etc., by utilizing electromagnetic waves in a frequency region called the terahertz band, which has a frequency of 0.1 THz to 10 THz, as shown in Patent Document 1, for example. This frequency region combines the properties of both light and radio waves, and if devices operating in this frequency band were realized, they could be used for many applications, including the aforementioned imaging, high-capacity communication, and information processing, as well as measurements in various fields such as physical properties, astronomy, and biology. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-115500

[0004] [overview] In a terahertz element that emits terahertz waves, which are electromagnetic waves in the terahertz band, the output of the terahertz element changes significantly in response to changes in the drive voltage applied to the element. For this reason, when a terahertz element that emits terahertz waves is driven by a voltage drive method (a drive method that controls the value of the drive voltage), the output of the terahertz element is likely to change in response to changes in the ambient environment, such as temperature, and power supply errors.

[0005] The driving device according to the present disclosure includes a current source configured to generate an output current, and the current source is configured to periodically perform the following operations: increase a current value of the output current from a first current value in a non-transmission region where a transmitter element does not transmit to a second current value greater than a transmission region where the transmitter element can transmit within 1 nanosecond; drive the transmitter element with the output current of the second current value; decrease a current value of the output current from the second current value to a third current value in the transmission region; drive the transmitter element with the output current of the third current value; and decrease a current value of the output current from the third current value to the first current value.

[0006] A transceiver according to the present disclosure includes a drive device having the above-described configuration, a transmitter including the emitting element, and a receiver configured to receive a transmission signal transmitted from the transmitter. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a transmitting / receiving device. [Figure 2] FIG. 2 is a diagram showing the configuration of a bias tee circuit. [Figure 3] FIG. 3 is a diagram showing an example of the current-voltage characteristics of a resonant tunneling diode. [Figure 4] FIG. 4 is a diagram showing a waveform of an output current output from the driving device according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing an example of the configuration of the drive device according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing the states of the switches included in the driving device of the configuration example shown in FIG. [Figure 7] FIG. 7 is a diagram showing a waveform of an output current output from the driving device according to the second embodiment. [Figure 8] FIG. 8 is a diagram showing an example of the configuration of a drive device according to the second embodiment. [Figure 9] FIG. 9 is a diagram for explaining parallel driving of a plurality of terahertz elements. [Figure 10]FIG. 10 is a diagram for explaining serial driving of a plurality of terahertz elements.

[0008] [Detailed explanation] <Transceiver> FIG. 1 is a diagram showing the configuration of a transceiver 1. The transceiver 1 shown in FIG. 1 includes a driver 10 and a transmitter 11 on the transmitting side, and a receiver 12, a bias tee circuit 13, a band pass filter (BPF) 14, an amplifier 15, and a microprocessor (MPU) 16 on the receiving side. The transceiver 1 may be configured as a reflection type in which a transmission signal Wt output from the transmitter 11 is reflected by an object and received by the receiver 12, or as a transmission type in which a transmission signal Wt output from the transmitter 11 passes through the object and is received by the receiver 12. The object is typically a solid. However, the object is not limited to a solid and may be a liquid or a gas.

[0009] The driving device 10 supplies a modulation signal Tx to the terahertz element included in the transmitter 11 to drive the terahertz element included in the transmitter 11. The terahertz element included in the transmitter 11 emits terahertz waves, which are electromagnetic waves in the terahertz band. The terahertz element included in the transmitter 11 is typically an RTD (resonant tunneling diode). Note that the terahertz element included in the transmitter 11 is not limited to an RTD and may be, for example, a TUNNETT (Tunnel injection Transit Time) diode, an IMPATT (Impact Ionization Avalanche Transit Time) diode, a GaAs-based field effect transistor (FET), a GaN-based FET, a high electron mobility transistor (HEMT), or a heterojunction bipolar transistor (HBT).

[0010] The transmitter 11 is a packaged chip on which a terahertz element and a fine slot antenna are formed on a substrate. When the terahertz element included in the transmitter 11 emits terahertz waves, a transmission signal (transmission wave) Wt in the terahertz band is output from the transmitter 11.

[0011] Similar to the transmitting unit 11, the receiving unit 12 is a packaged chip having a terahertz element and a fine slot antenna formed on a substrate. The terahertz element included in the receiving unit 12 receives terahertz waves. Note that, like the terahertz element included in the transmitting unit 11, the terahertz element included in the receiving unit 12 is not limited to an RTD. The transmitting signal Wt is received by the fine slot antenna included in the receiving unit 12.

[0012] A bias tee circuit 13 is provided between the receiver 12 and the BPF 14. As shown in FIG. 2, the bias tee circuit 13 has an inductor L and a capacitor C. A DC voltage Vcc is supplied to the terahertz element included in the receiver 12 via the inductor L. An AC signal output from the receiver 12 passes through the capacitor C and is output to the BPF 14 as a received signal Rx. The capacitor C cuts off the DC voltage Vcc.

[0013] The BPF 14 is a filter that passes signals in a specific frequency band and removes noise that may be included in the received signal Rx. The specific frequency band is set to include the frequency of the modulated signal Tx.

[0014] The amplifier 15 amplifies the signal that has passed through the BPF 14 and outputs it to the MPU 16. The MPU 16 has an ADC (AD converter) 16A that performs analog-to-digital conversion on the output from the amplifier 15, and a frequency analysis unit 16B that performs frequency analysis such as FFT (fast Fourier transform) on the AD-converted signal. The power spectrum value at the frequency of the modulated signal Tx obtained by the frequency analysis unit 16 is treated as the signal strength on the receiving side (for example, sensor sensitivity if the transceiver 1 is a sensing device that detects a specific substance, or imaging sensitivity if the transceiver 1 is an imaging device that measures the shape of an object made of a specific material).

[0015] The above-described driving device 10 drives the terahertz element by a current driving method (a driving method that controls the value of the driving current, i.e., the output current output from the driving device 10). In the case of a terahertz element, the change in the output of the terahertz element in response to a change in the driving current supplied to the terahertz element is smaller than the change in the output of the terahertz element in response to a change in the driving voltage applied to the terahertz element.

[0016] Therefore, compared to a driving device that employs a voltage driving method, the driving device 10 that employs a current driving method can improve the output stability of the terahertz element against changes in the surrounding environment. Also, compared to a driving device that employs a voltage driving method, the driving device 10 that employs a current driving method can improve the output stability of the terahertz element against power supply errors (output errors of the driving device 10 or output errors of a driving device that employs a voltage driving method).

[0017] However, terahertz devices have current-voltage characteristics in which two voltage values are obtained at the same current value in the transmission region. Figure 3 shows an example of the current-voltage characteristics of an RTD, which is a typical example of a terahertz device.

[0018] The non-transmission region shown in Figure 3 is the region where the RTD does not transmit. The transmission possible region shown in Figure 3 is the region where the RTD can transmit. Note that the RTD does not transmit in regions where the current is greater than the transmission possible region. In the transmission possible region shown in Figure 3, if the voltage value of the voltage applied to the RTD is equal to or greater than the threshold value TH, the RTD will transmit, and if the voltage value of the voltage applied to the RTD is less than the threshold value TH, the RTD will not transmit. The solid arrow shown in Figure 3 indicates the direction of change in the current-voltage characteristics when the current supplied to the RTD is increased. The dotted arrow shown in Figure 3 indicates the direction of change in the current-voltage characteristics when the current supplied to the RTD is decreased.

[0019] Due to such current-voltage characteristics of the RTD, for example, if the driving device 10 drives the RTD with a current of 18 mA, if the current history is not determined, the value of the voltage applied to the RTD will be indefinite, and it will be unclear whether the RTD will transmit or not.

[0020] Therefore, the driving device 10 includes a current source that generates an output current Iout for driving the terahertz element by a current driving method, and the current source is configured to perform the following operation.

[0021] The current source increases the value of the output current Iout from a first current value I1 in a non-transmission region to a second current value I2 greater than the transmission region within 1 nanosecond, and drives the terahertz device with the output current Iout at the second current value I2. During this drive, the terahertz device does not transmit. In addition, by increasing the value of the output current Iout from the first current value I1 to the second current value I2 within 1 nanosecond, power consumption during the period in which the value of the output current Iout increases from the first current value I1 to the second current value I2 can be reduced.

[0022] The current source then reduces the output current Iout from the second current value I2 to a third current value I3 within the transmission range, and drives the terahertz device with the output current Iout at the third current value I3. This driving causes the terahertz device to transmit. The third current value I3 may be set to, for example, the current value of the output current Iout at which the output of the terahertz device is maximized.

[0023] Thereafter, the current source decreases the current value of the output current Iout from the third current value I3 to the first current value I1.

[0024] The current source periodically performs the above-described series of operations.

[0025] The first current value I1 may be zero or greater than zero. When the first current value I1 is zero, the power consumption of the driving device 10 can be reduced. On the other hand, when the first current value I1 is greater than zero, the current value of the output current Iout can be easily increased from the first current value I1 to the second current value I2 within 1 nanosecond.

[0026] The frequency of the above operation is preferably between 100 Hz and 10 MHz. This frequency setting makes frequency analysis on the receiving side easier. Also, considering that the intensity reduction of 1 / f noise saturates at roughly 1 MHz, it is even more desirable to set the frequency of the above operation between 1 MHz and 10 MHz.

[0027] <First embodiment of driving device> 4 is a diagram showing the waveform of the output current Iout output from the driving device 10 according to the first embodiment. In the first embodiment, the waveform of the output current Iout is a square wave.

[0028] The first period P1 during which the terahertz element is driven with the output current Iout of the second current value I2 is preferably shorter than the second period P1 during which the terahertz element is driven with the output current Iout of the third current value I3. This makes it possible to reduce power consumption during the first period P1 during which the terahertz element does not emit light. The length of the first period P1 may be set to, for example, about 1% of the cycle of the output current Iout.

[0029] Fig. 5 is a diagram showing an example of the configuration of the driving device 10 according to the first embodiment. The driving device 10 of the example configuration shown in Fig. 5 is configured to include a switch and an operational amplifier, and generates an output current Iout having the waveform shown in Fig. 4, and supplies the output current Iout to the terahertz element 11A included in the transmitting unit 11 (see Fig. 1).

[0030] The driving device 10 of the configuration example shown in FIG. 5 includes resistors R11 to R14, switches SW11 to SW13, a logic circuit LGC11, a shunt regulator SR11, an operational amplifier OP11, and a P-channel MOS (Metal Oxide Semiconductor) field effect transistor Q11.

[0031] Fig. 6 is a diagram showing the states of the switches SW11 to SW13 included in the driving device 10 of the configuration example shown in Fig. 5. The states of the switches SW11 to SW13 are controlled by enable signals E1 to E3 output from the logic circuit LGC11.

[0032] When the switch SW11 is in the on state, the current value of the output current Iout becomes a first current value I1. The first current value I1 is determined by the voltage value of the voltage Vreg output from the shunt regulator SR11 and the resistance value of the resistor R11.

[0033] When the switch SW12 is in the on state, the current value of the output current Iout becomes a second current value I2. The second current value I2 is determined by the voltage value of the voltage Vreg output from the shunt regulator SR11 and the resistance value of the resistor R12.

[0034] When the switch SW13 is in the on state, the current value of the output current Iout becomes a third current value I3. The third current value I2 is determined by the voltage value of the voltage Vreg output from the shunt regulator SR11 and the resistance value of the resistor R13.

[0035] The resistance value of resistor R11 is greater than the resistance value of resistor R13. The resistance value of resistor R13 is greater than the resistance value of resistor R12.

[0036] <Second embodiment of the driving device> FIG. 7 is a diagram showing the waveform of the output current Iout output from the driving device 10 according to the second embodiment. In the second embodiment, the waveform of the output current Iout is a ramp wave having a first slope and a second slope. The first slope is a slope that changes over time from a first current value I1 (the lower limit of the ramp wave) to a second current value I2 (the upper limit of the ramp wave). The second slope is a slope that changes over time from the second current value I2 (the upper limit of the ramp wave) to the first current value I1 (the lower limit of the ramp wave). The first slope is greater than the absolute value of the second slope. Note that although the ramp wave shown in FIG. 7 is a sawtooth wave, it may also be a triangular wave whose first slope is smaller than that of a sawtooth wave.

[0037] Fig. 8 is a diagram showing an example of the configuration of the driving device 10 according to the second embodiment. The driving device 10 of the example configuration shown in Fig. 8 is configured to include a DA converter and an operational amplifier, and generates an output current Iout having the waveform shown in Fig. 7, and supplies the output current Iout to the terahertz element 11A included in the transmitting unit 11 (see Fig. 1).

[0038] The driving device 10 of the configuration example shown in Figure 8 includes a logic circuit LGC21, a DA converter D21, operational amplifiers OP21 and OP22, resistors R21 to R27, capacitors C21 and C22, an N-channel MOS field effect transistor Q21, and a P-channel MOS field effect transistor Q22.

[0039] The logic circuit LGC21 supplies a digital ramp voltage Vramp1 to a DA converter D21. The DA converter D21 converts the digital ramp voltage Vramp1 into an analog ramp voltage Vramp2. The logic circuit LGC21 stores data related to the digital ramp voltage Vramp1 such that the waveform of the analog ramp voltage Vramp2 and the waveform of the output current Iout are similar to each other.

[0040] Unlike the drive device 10 according to the first embodiment, the drive device 10 according to the second embodiment has the advantage that no switching noise occurs.

[0041] <Driving multiple terahertz devices> In the above explanation, the driving device 10 included in the transmitting unit 11 is a single terahertz element, but by transmitting from multiple terahertz elements, it is possible to increase the output of terahertz waves and improve the S / N ratio.

[0042] The plurality of terahertz elements 11A can be driven in a parallel manner as shown in FIG. 9 or in a series manner as shown in FIG.

[0043] 9 requires the same number of driving devices 10 as the number of terahertz elements 11A. On the other hand, the serial driving shown in Fig. 10 has the advantage that only one driving device 10 is required regardless of the number of terahertz elements 11A. In the serial driving shown in Fig. 10, the driving voltage applied to the plurality of terahertz elements 11A increases depending on the number of terahertz elements 11A. However, since the forward voltage of the terahertz elements 11A (for example, about 0.4 [V] for an RTD) is small, if the number of terahertz elements 11A is less than about 10, the driving device 10 can be a device based on an existing LED (Light Emitting Diode) driver.

[0044] <Other> The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The technical scope of the present disclosure is indicated by the claims, not by the description of the above-described embodiments, and should be understood to include all modifications that fall within the meaning and scope equivalent to the claims.

[0045] For example, the transmitting element driven by the driving device 10 may be an element other than a terahertz element, as long as it has current-voltage characteristics that take two voltage values at the same current value in the transmitting region.

[0046] <Additional Notes> A supplementary note will be provided for the present disclosure, the specific configuration examples of which have been shown in the above-described embodiments.

[0047] The driving device (10) of the present disclosure has a current source (CS11, CS21) configured to generate an output current, and the current source is configured to periodically perform the following operations (first configuration): increase the current value of the output current from a first current value in a non-transmission region where the emitting element (11A) does not emit to a second current value greater than a transmission region where the emitting element can emit within 1 nanosecond; drive the emitting element with the output current of the second current value; decrease the current value of the output current from the second current value to a third current value in the transmission region; drive the emitting element with the output current of the third current value; and decrease the current value of the output current from the third current value to the first current value.

[0048] The driving device of the first configuration drives the terahertz element using a current driving method. The change in the output of a terahertz element in response to a change in the driving current supplied to the terahertz element is smaller than the change in the output of the terahertz element in response to a change in the driving voltage applied to the terahertz element. Therefore, the driving device of the first configuration can improve the output stability of the terahertz element in response to changes in the surrounding environment, compared to a driving device employing a voltage driving method. Furthermore, the driving device of the first configuration can improve the output stability of the terahertz element in response to power supply errors (output errors of the driving device of the first configuration or output errors of a driving device employing a voltage driving method), compared to a driving device employing a voltage driving method. Furthermore, the driving device of the first configuration determines the current history, thereby determining the value of the voltage applied to the terahertz element and enabling the terahertz element to reliably emit light.

[0049] In the driving device of the first configuration, the waveform of the output current may be a square wave (second configuration).

[0050] In the driving device of the second configuration described above, the first period during which the emitting element is driven with the output current of the second current value may be shorter than the second period during which the emitting element is driven with the output current of the third current value (third configuration).

[0051] In the driving device of the first configuration described above, the waveform of the output current may be a ramp wave having a first slope and a second slope, the first slope being a slope from the first current value to the second current value over time, the second slope being a slope from the second current value to the first current value over time, and the first slope may be a slope greater than the absolute value of the second slope (fourth configuration).

[0052] In the driving device of any one of the first to fourth configurations, the operating frequency may be 100 Hz or more and 10 MHz or less (fifth configuration).

[0053] In the driving device of any one of the first to fifth configurations, the first current value may be zero (sixth configuration).

[0054] In the driving device of any of the first to fifth configurations, the first current value may be greater than zero (seventh configuration).

[0055] The transmitting / receiving device (1) according to the present disclosure has a configuration (eighth configuration) including a driving device of any one of the first to seventh configurations, a transmitting unit (11) including the transmitting element, and a receiving unit (12) configured to receive a transmission signal transmitted from the transmitting unit.

[0056] In the transmitting / receiving device of the eighth configuration, the transmitting section may be configured to include a plurality of the transmitting elements (ninth configuration).

[0057] In the transmitting / receiving device of the eighth configuration, the transmitting section may be configured to include a plurality of the transmitting elements connected in series (tenth configuration).

[0058] In the driving device of any one of the eighth to tenth configurations, the transmitting element may be a terahertz element configured to transmit terahertz waves, which are electromagnetic waves in the terahertz band (eleventh configuration). [Explanation of symbols]

[0059] 1. Transmitting and receiving device 10 Drive unit 11 Transmitter 11A Terahertz element 12 Receiving section 13 Bias Tee Circuit 14 BPF 15 amps 16 MPU 16A AD converter 16B Frequency analysis section C, C21, C22 capacitors D21 DA Converter L inductor LGC11, LGC21 logic circuit OP11, OP21, OP22 operational amplifiers Q11 P-channel MOS field effect transistor R11~R14, Resistor 21~27 Resistor SR11 Shunt Regulator SW11 to SW13 switches

Claims

1. a current source configured to generate an output current; The current source is increasing the current value of the output current from a first current value in a non-transmission region where the transmitting element does not transmit to a second current value greater than a transmission region where the transmitting element can transmit within 1 nanosecond; driving the transmitting element with the output current of the second current value; Decreasing the current value of the output current from the second current value to a third current value in the transmission possible region; driving the transmitting element with the output current of the third current value; a driving device configured to periodically perform an operation of decreasing the current value of the output current from the third current value to the first current value.

2. 2. The drive device according to claim 1, wherein the waveform of the output current is a square wave.

3. 3. The drive device according to claim 2, wherein a first period during which the transmitting element is driven by the output current of the second current value is shorter than a second period during which the transmitting element is driven by the output current of the third current value.

4. the waveform of the output current is a ramp wave having a first slope and a second slope; the first slope is a slope from the first current value to the second current value over time, the second slope is a slope from the second current value to the first current value over time, The drive device according to claim 1 , wherein the first slope is greater than an absolute value of the second slope.

5. The drive device according to claim 1 , wherein the operating frequency is equal to or greater than 100 Hz and equal to or less than 10 MHz.

6. The drive device according to claim 1 , wherein the first current value is zero.

7. The drive device of claim 1 , wherein the first current value is greater than zero.

8. A drive device according to any one of claims 1 to 7; a transmitting unit including the transmitting element; a receiving unit configured to receive a transmission signal transmitted from the transmitting unit; A transmitting and receiving device comprising:

9. The transmitting / receiving device according to claim 8 , wherein the transmitting section includes a plurality of the transmitting elements.

10. The transmitting / receiving device according to claim 8 , wherein the transmitting section includes a plurality of the transmitting elements connected in series.

11. The transmitting / receiving device according to claim 8 , wherein the transmitting element is a terahertz element configured to transmit terahertz waves, which are electromagnetic waves in the terahertz band.

Images