Semiconductor device, communication device, imaging system, and radar device

Abstract

To provide a technique capable of maintaining an RTD oscillator in a stable oscillation state even when an oscillation condition for the RTD oscillator is changed, while performing injection locking of the RTD oscillator.SOLUTION: A semiconductor device has an RTD oscillator, a reference oscillator that synchronizes with the RTD oscillator, an oscillation adjustment unit that adjusts the oscillation signal of the RTD oscillator, and a control unit that controls the reference oscillator and the oscillation adjustment unit. The oscillation adjustment unit controls the operation of the oscillation adjustment unit in accordance with the operation of the reference oscillator on the basis of signals from the control unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device, a communication device, an imaging system, and a radar device. [Background technology]

[0002] As a current injection type light source that generates terahertz waves, an oscillator that integrates an element having electromagnetic wave gain for terahertz waves and a resonator is known. Among these, an oscillator that integrates a resonant tunneling diode (RTD) and an antenna is expected to be an element that operates at room temperature in a frequency range around 1 THz. Patent Document 1 discloses an antenna device that is configured to function as an injection-locked oscillator by supplying a master signal to an oscillator using an RTD, and that reduces the phase noise of the RTD oscillator by controlling the phase of the RTD oscillator from the master signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-157737 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a technique that can bring an RTD oscillator into a stable oscillation state even when the oscillation state of the RTD oscillator is changed while injection locking is being performed on the RTD oscillator. [Means for solving the problem]

[0005] A semiconductor device according to one aspect of the present invention comprises an RTD oscillator, a reference oscillator that synchronizes the RTD oscillator, an oscillation adjustment unit that adjusts the oscillation signal of the RTD oscillator, and a control unit that controls the reference oscillator and the oscillation adjustment unit, and is characterized in that the oscillation adjustment unit is controlled in accordance with the operation of the reference oscillator by a control signal from the control unit. [Effects of the Invention]

[0006] According to the present invention, even if the oscillation state of the RTD oscillator is changed while injection locking is being performed on the RTD oscillator, the RTD oscillator can be brought into a stable oscillation state. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram according to a first embodiment. [Figure 2] 1 is a graph showing the characteristics of injection locking in an RTD oscillator. [Figure 3] FIG. 10 is a schematic diagram showing a configuration example of bias adjustment by an oscillation adjustment unit. [Figure 4] FIG. 10 is a schematic diagram showing a configuration example of feedback control by an oscillation adjuster. [Figure 5] 10 is a schematic diagram showing a configuration example of an impedance adjustment circuit using an oscillation adjustment unit. FIG. [Figure 6] FIG. 1 is a diagram showing an example of an equivalent circuit of an RTD oscillator and its peripheral components. [Figure 7] FIG. 10 is a block diagram according to a second embodiment. [Figure 8] 10 is a schematic diagram showing a configuration example of phase adjustment in an injection locking unit. FIG. [Figure 9] FIG. 10 is a block diagram according to a third embodiment. [Figure 10] FIG. 10 is a block diagram according to a fourth embodiment. [Figure 11] FIG. 10 is a block diagram according to a fifth embodiment. [Figure 12] FIG. 10 is a schematic diagram showing a configuration example according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Each embodiment will be described with reference to the drawings. The drawings are intended to embody the technical concept and are not intended to limit the present invention. Although multiple features are described in the embodiments, not all of these features are necessarily essential to the invention, and multiple features can be combined as desired. In the description of each embodiment, descriptions of configurations that are identical to those of other embodiments may be omitted. The embodiments can be modified or combined with other embodiments as appropriate. The sizes and positional relationships of components shown in each drawing may be exaggerated for clarity.

[0009] (First embodiment) 1 is a block diagram showing an example of the configuration of an apparatus 10 relating to a semiconductor device of this embodiment. In the following description, for convenience, the semiconductor device 100 and the apparatus 10 will be distinguished from each other, but the concept of a semiconductor device in this specification includes not only the semiconductor device 100 but also the apparatus 10. In addition, although the following description will be given of a case where the apparatus 10 is used as a transmitter, the apparatus 10 can also be used as a receiver.

[0010] The apparatus 10 is configured to radiate a signal generated inside the semiconductor device 100 into space as a terahertz wave 103. Here, the terahertz wave refers to an electromagnetic wave within a frequency range of 10 GHz or more and 100 THz or less, more preferably 30 GHz or more and 30 THz or less.

[0011] The RTD oscillator 104 is composed of an RTD 108, which is an oscillation source, and a resonant conductor 109 with a resonant structure. The RTD oscillator can generate or detect terahertz waves 103 by combining a resonant tunneling diode (RTD) having a semiconductor structure with a resonant structure. The oscillation signal generated by the RTD oscillator can include signals with frequencies between 0.3 THz and 0.6 THz. A reference signal generated by a reference oscillator 102 external to the semiconductor device 100 is input to the RTD oscillator 104. The RTD oscillator 104 can self-oscillate at a self-oscillation frequency even when used alone, but phase noise can be reduced by using the reference oscillator 102 as a master oscillator and operating the RTD oscillator 104 as a slave. The reference oscillator 102 is a wave source for synchronizing the timing of the terahertz waves, and generates an oscillation frequency f THz The reference oscillator 102 outputs a subharmonic frequency that is 1 / N (N is a natural number) times the reference frequency. This subharmonic frequency is injection locked to the RTD oscillator. In this embodiment, the subharmonic frequency is explained as 1 / 2. Furthermore, while the reference oscillator is changing the frequency, the oscillation adjustment unit can apply a bias to the RTD oscillator by adjusting the bias potential that is synchronized with the harmonic component of the reference frequency output from the reference oscillator. The signal output of the reference oscillator 102 is larger than the output of the slave RTD oscillator 104.

[0012] The power injected by the input from the reference oscillator 102 to the RTD oscillator 104 is equal to the output P RTD ((3 / 16)cosωτ×ΔIΔV) or more is desirable. Here, P RTD is the output of the RTD, ω is the angular frequency of the terahertz wave, and τ is the carrier transit time in the semiconductor layer. ΔI and ΔV are the current difference and voltage difference, respectively, between the current peak and current valley in the negative resistance region of the RTD. There is no limit to the number of RTDs that can be mounted inside the RTD oscillator 104, and it is preferable that the power summed up for the number of RTDs mounted be input from the reference oscillator 102 to the RTD oscillator 104. The output of the reference oscillator 102 is (number of RTDs in the RTD oscillator 104)×P RTDIn addition to ((3 / 16)cosωτ×ΔIΔV), an output greater than the transmission loss from the reference oscillator 102 to each RTD of the RTD oscillator 104 is desired. On the other hand, the output from the reference oscillator 102 is P RTD Specifically, it has been confirmed that the RTD oscillator 104 can synchronize with the signal of the reference oscillator 102 even with a signal as small as 1 / 10,000 of the output of one RTD. RTD Even when a reference oscillator 102 having an output smaller than ((3 / 16)cosωτ×ΔIΔV) is used, the frequency output by the reference oscillator 102 It is possible to synchronize the RTD oscillator 104 while maintaining accuracy. That is, the signal strength output by the reference oscillator 102 is P RTD It can be set without being heavily dependent on the value of

[0013] The oscillation adjustment unit 106 adjusts the oscillation of the RTD oscillator 104 in accordance with the operation of the reference oscillator 102 using a control signal input from a control unit 101 disposed outside the semiconductor device 100 .

[0014] The oscillation adjustment unit 106 is electrically connected to the RTD oscillator 104, and can include an impedance adjustment means that adjusts the voltage and current when the RTD oscillator 104 oscillates, as well as controls the impedance of the resonant conductor 109. The oscillation adjustment unit 106 adjusts physical parameters such as the frequency, phase, and intensity of the terahertz wave signal generated by the RTD oscillator 104.

[0015] The resonant conductor of the RTD oscillator 104, which has a resonant structure, is a microstrip line resonator, and is composed of a wide lower conductor GND, a line-shaped upper conductor, and a dielectric between them. The line length of the upper conductor is set to be a multiple of λ / 2, where λ is the wavelength λ of the signal oscillating within the RTD oscillator 104. Specifically, the wavelength λ of 0.5 THz is 0.6 mm, and since the relative dielectric constant on the resonator is about 2, the electrical length of λ / 2 is 0.15 mm. It is preferable to use this line length as a reference for design. The thickness of the dielectric is preferably between λ / 10 and λ / 3.

[0016] The semiconductor device 100 can include a bias unit 105 that applies a bias. When the bias is used to control the oscillation adjustment unit 106, the bias can be supplied to the RTD oscillator 104 via the oscillation adjustment unit 106, but it can also be supplied directly to the RTD oscillator 104. The connection configuration of the bias unit to which the present invention can be applied is not limited to this embodiment.

[0017] The bias unit 105 supplies the power required to drive the RTD 108 and adjusts the bias potential applied to the RTD 108. In the case of an RTD, a bias signal is selected from a voltage that falls within the negative differential resistance region of the RTD and applied. The bias potential that drives the RTD and is applied from the bias unit 105 to the RTD 108 is approximately DC, so it is preferable to connect it directly or input it via a low-pass filter or the like.

[0018] The behavior of the synchronization process performed by the reference oscillator 102 on the RTD oscillator 104 will be described using FIG. 2. FIG. 2(a) shows an image of a graph plotted with the bias potential applied to the RTD 108 on the horizontal axis and the frequency oscillated by the RTD oscillator 104 on the vertical axis. The process of inputting a reference signal from the reference oscillator 102 to the RTD oscillator 104 to stabilize the frequency of the RTD oscillator 104 is called injection locking. In this embodiment, the RTD oscillator 104 uses the harmonic components of the signal output by the reference oscillator 102. The solid line in the graph is an image of a graph (injection locking plot 201) plotting the oscillation frequency and bias potential observed in the RTD oscillator 104 when there is input from the reference oscillator 102, i.e., when injection locking is performed. A subharmonic frequency of 0.25 [THz], which is half of 0.5 [THz], is input from the reference oscillator 102. The dashed line in the graph is an image (non-injection locked plot 202) plotting the oscillation frequency and bias potential seen in the RTD oscillator 104 when injection locking is not performed. This frequency is an example, and the frequency of the signal output by the reference oscillator 102 is not limited to this embodiment as long as it is the same as that of the RTD oscillator 104 or has a harmonic component.

[0019] First, let us check the self-oscillation frequency of the RTD 108. When the non-injection locked plot 202 in FIG. 2(a) is checked, it is found that the RTD 108 oscillates at 0.5 THz when the bias voltage is 0.7 V. As can be seen, the self-oscillation frequency shifts downward when the bias potential is lowered, and shifts upward when the bias potential is increased. Next, let's examine the injection locking plot 201. At a bias potential of 0.7 V, the frequency reaches 0.5 THz, but it remains at 0.5 THz even when the bias potential is lowered to 0.69 V. Similarly, it remains at 0.5 THz even when the bias potential is increased to 0.71 V. This is the phenomenon in which the oscillation frequency of the RTD oscillator 104 is locked by injection locking from the reference oscillator 102. Locking the frequency in this way is called locking, and changing the frequency from a locked state to an unlocked state is called unlocking.

[0020] 2(a), it can be seen that the locking region is the region where the bias potential is from 0.69 [V] to 0.71 [V], and this region is called the locking range. Within the locking range, the RTD oscillator 104, which is the injection-locked oscillator, is fixed depending on the frequency of the reference oscillator 102. It is also known that the range of this locking range widens when the signal from the reference oscillator 102 input to the RTD oscillator 104 is strong, and conversely, when it is weak, the voltage range becomes narrow.

[0021] Figure 2(b) shows the phase difference between the injected signal of the reference oscillator 102 and the signal of the RTD oscillator 104 when injection locking is present, with the bias potential of the RTD 108 on the horizontal axis. At 0.7 [V], the phase difference is 0°, which means that the injection locking frequency and the self-oscillation frequency match, and therefore the frequency and phase match. As the bias potential is lowered, the phase changes towards -90°, and as the bias potential is raised, the phase changes towards +90°. This means that the self-oscillation frequencies of the reference oscillator 102 and RTD oscillator 104 differ, and when they are locked, the frequency difference appears as a phase difference. This phase difference can be calculated using the theoretical formula φ=sin -1 (Q√((P o / P i)×(f1-f0) / (f1))). φ is the oscillation phase of the RTD oscillator 104, and Pi is the oscillation power. Po is the oscillation power of the harmonic components of the reference signal input from the reference oscillator and synchronized, and Q is the Q factor of the RTD oscillator 104. The sharper the frequency spectrum, the higher the Q factor, and it is used as an output index of the oscillator circuit. f1 is the self-oscillation frequency, and f0 is the frequency oscillated by injection locking, i.e., the oscillation frequency of the reference oscillator 102. As can be seen from the equation, this phase difference varies within a range of -90° to +90°. In other words, the phase difference within the locking range varies within a range of -90° to +90°, and the width of the locking range varies depending on the ratio of the oscillation power of the injection-locked oscillator to the injection power.

[0022] 3 is a diagram illustrating the oscillation adjustment unit 106 of this embodiment. The oscillation adjustment unit 106 is a circuit for adjusting the oscillation state of the RTD oscillator 104, and will be described as an example in this embodiment. The oscillation adjustment unit 106 is controlled based on a control signal output from the control unit 101, and adjustments are made to the RTD oscillator 104. At that time, control can be performed in accordance with the operation of the reference oscillator 102.

[0023] FIG. 3(a) includes a circuit that adjusts the bias potential of the bias unit 105 using the oscillation adjustment unit 106. The oscillation adjustment unit 106 inputs the power line supplied from the bias unit 105 to the RTD oscillator 104. The input power is connected to the output port 302 through a resistor R1 (301), and is finally connected to the RTD oscillator 104. A variable resistor Rv (303) is connected between the resistor R1 (301) and the output port 302 and the GND potential. The potential output from the output port 302 is the bias potential of the bias unit 105 divided by the resistor R1 (301) and the variable resistor Rv (303). A control signal from the control unit 101 is input to the input port 304 of the variable resistor Rv (303), and the resistance value of the variable resistor Rv (303) is adjusted based on this signal. By adjusting the resistance of the variable resistor Rv (303), This makes it possible to control the bias potential applied to the RTD oscillator 104. By changing the bias potential, the RTD oscillator 104 can change the phase of the signal it oscillates.

[0024] FIG. 3(b) shows an example of dynamic adjustment of the RTD oscillator 104 by the oscillation adjustment unit 106b. The wiring from the bias unit 105 is connected to the output port 302 via an inductor L1 (305) within the oscillation adjustment unit 106b. A branch is made between the inductor L1 and the output port 302, and a capacitor C1 (306) is connected to the branch. The inductor L1 (305) and the capacitor C1 (306) function as a bias tee, and can output a signal to the output port 302, in which a DC component from the bias unit 105 and an AC component from the capacitor C1 (306) are superimposed. The terminal of the capacitor C1 (306) opposite the output port 302 is connected in parallel between a variable resistor Rv (303) and a control signal source 307, both connected to GND. A control signal from the control unit 101 is input via two input ports (304, 308). The signal from the input port 308 controls the oscillation frequency of the control signal source 307. The signal from the control signal source is continuous, such as a sine wave, but may also be a pulse with discrete values. The signal from the input port 304 controls the amplitude of the oscillating AC signal by varying the resistance of the variable resistor Rv (303). The output port 302 adjusts the DC component potential to the negative resistance region required to oscillate the RTD oscillator 104, as well as the AC component by varying the DC component potential over time. This allows for phase control when scanning a beam that changes over time. Furthermore, the adjustment of the AC component by the oscillation adjuster 106b can be used for phase modulation control, such as phase shift keying (PSK), by varying the discrete voltage value of the RTD oscillator 104 in accordance with the data sequence to be transmitted. Regarding the bias potential adjustment means described above, other circuit configurations for changing the bias potential of the RTD oscillator 104 or methods for changing the potential on the GND side of the RTD oscillator 104 can be substituted with other means. The means for changing the bias potential applied to the RTD 108 of the RTD oscillator 104 is not limited to this embodiment.

[0025] 3(a) and 3(b), the control signal from the control unit 101 can be adjusted according to the operation of the reference oscillator 102 in FIG. 1. Specifically, the setting value of the variable resistor Rv (303) input to the input port 304 can be adjusted according to the frequency of the synchronization signal output from the reference oscillator 102. The frequency output from the reference oscillator 102 is the frequency at which the RTD oscillator 104 is injection-locked. However, the bias potential at this time must be adjusted according to the frequency because the self-oscillation frequency changes as shown in FIG. 2(a). The control unit 101 controls the reference oscillator 102 and can detect the frequency output by the reference oscillator 102. Alternatively, the reference oscillator 102 can be controlled by another control unit (not shown), and the control unit 101 can receive the control information as a signal. However, the means for obtaining setting information such as the signal strength, phase, and frequency of the reference oscillator are not limited to this. Furthermore, specific examples of control by the control unit 101 include setting the strength and changing the phase of the signal output by the reference oscillator 102. When the signal strength output by the reference oscillator 102 changes, the signal strength input to the RTD oscillator 104 also changes, causing a change in the locking range. Because voltage adjustment by the oscillation adjustment unit must be performed within the locking range, a control instruction with a changed adjustment amount must be sent from the control unit 101 to the oscillation adjustment unit 106. Phase changes can also be adjusted in a similar manner based on the relationship between the frequency, locking range, and bias voltage described above.

[0026] 4 shows a block diagram for explaining another adjustment method of the oscillation adjuster 106c. The oscillation adjuster 106c is connected to the output port 302 from the bias unit 105 via a resistor R1 (301). A switch 311 and a switch 317 are connected between the resistor R1 (301) and the output port 302, and the switches can be switched ON / OFF by a control signal input from the control unit 101 to the input port 309. A variable resistor Rv (303) is connected to the other terminal of the switch 311, and when the switch 311 is ON, the voltage Vout shown in FIG. 3(a) is changed to the ON voltage Vout shown in FIG. The other terminal of the switch 317 is connected to the adjustment circuit 314. When the switch 317 is ON, the output of the adjustment circuit 314 is connected to the output port 302. The switches 311 and 317 are configured to be turned ON / OFF exclusively.

[0027] Adjustment circuit 314 receives a portion of the reference signal output from reference oscillator 102 via input port 310, divides the signal by N through divider 313, and inputs the N-divided signal to mixer 316. Mixer 316 receives the N-divided signal as well as the output signal from adjustment oscillator 315, compares their phases, and outputs a differential voltage corresponding to the phase difference. The voltage value output from mixer 316 is output as the output of the adjustment circuit, and is smoothed by filter 312 to a desired frequency band.

[0028] The oscillation adjustment unit 106c receives a control signal from the control unit 101 and controls the operation of the reference oscillator 102 accordingly. The oscillation adjustment unit 106c can perform feedback control of the adjustment by receiving a signal output by the reference oscillator 102 to synchronize the RTD oscillator 104 or a signal equivalent thereto (such as a reflected signal from the RTD oscillator). Furthermore, signal changes, such as reducing the influence of return signals and reflected waves (reflected signals) when the phases of the reference oscillator 102 and the RTD oscillator 104 are aligned, can also be effectively utilized for feedback control. Confirming that the phases are aligned reveals that the bias of the RTD oscillator 104 at that point is the reference center point, which can be used for adjustments such as changing the bias by ±0.01 V based on that point. To achieve this, a configuration is conceivable in which the output signal of the reference oscillator 102 is input for control. Alternatively, the reference signal output by the reference oscillator 102 can be used instead of the adjustment oscillator 315. The circuit configuration in FIG. 4 is an example, and the circuit configuration of the oscillation adjustment unit to which this embodiment is applied is not limited to this.

[0029] FIG. 5 shows a configuration example for adjusting the impedance of the RTD oscillator 104 in the oscillation adjustment unit 106d. The resonant conductor 109 of the RTD oscillator 104 is necessary to resonate the oscillation signal of the RTD oscillator 104, and impedance adjustment is possible by connecting the resonant conductor 109 to a circuit such as that shown in FIG. 5. The oscillation adjustment unit 106d has λ / 2 lines Z1 and Z2 connected in series. The terminal of Z1 opposite Z2 is open and functions as an open stub. The terminal of Z2 opposite Z1 is connected to a switch 321. A control signal input from the control unit 101 to the oscillation adjustment unit 106d is connected to the switch 321 via an input port 318, and controls the switch's ON / OFF state. A variable impedance circuit 320 is connected to the connection between Z1 and Z2. In the variable impedance circuit 320, a capacitor C2, an impedance Z1, and a varactor diode with variable capacitance Cv are connected between GND. To adjust the capacitance of variable capacitance Cv, a signal input from control unit 101 via input port 319 is connected between Z1 and the RTD oscillator 104 by turning on switch 321. Oscillation adjuster 106d is connected to RTD oscillator 104 and can adjust the impedance of resonant conductor 109. Furthermore, by using a variable impedance circuit using a variable capacitance such as a varactor diode or a transistor for Cv, as shown in Figure 5, it is possible to improve controllability from control unit 101.

[0030] In addition to the configuration example shown in the figure, an impedance adjustment circuit can be provided that changes the influence of reflected waves by switching the microstrip line with a switch. Also, a circuit that can change the impedance or the phase of the connected line, such as a reflective phase adjustment circuit that uses a 90° hybrid circuit and variable capacitance, can be provided. These circuits can reduce loss during oscillation of the RTD oscillator 104 and increase the efficiency of oscillation by adjusting the impedance of the resonant conductor 109 to match the frequency of the synchronization signal coming from the reference oscillator 102. Also, by adopting a configuration that increases loss, it is possible to adjust the oscillation intensity or change the radiation direction. A circuit can be configured in which the oscillation adjuster 106d adjusts the oscillation signal of the RTD oscillator 104, for example by changing the direction of the oscillation signal. Furthermore, information such as changes in frequency and phase of the signal output from the reference oscillator 102 and transmission delay can be added to the signal at the input port 319. Also, adjustments can be made such as feeding back to the control parameters of the variable impedance circuit 320 in accordance with changes in the synchronization signal that synchronizes the RTD oscillator 104.

[0031] Next, the control performed by the control unit 101 will be described. The control unit 101 performs control by transmitting control signals necessary for the oscillation adjustment unit 106 to perform adjustments. In this embodiment, the control unit 101 controls the reference oscillator 102 and the oscillation adjustment unit 106. When driving the device 10, the control unit 101 controls the reference oscillator 102 to set parameters such as frequency, phase, and output intensity. The reference oscillator uses a typical PLL (Phase Locked Loop) circuit to oscillate at the desired frequency using an oscillation signal input from a lower frequency source, such as a high-precision oscillation source using a crystal oscillator. The control unit 101 sends a control signal to the oscillation adjustment unit after the reference oscillator 102 is set and its oscillation has stabilized. At this time, the control unit 101 can determine the adjustment value of the oscillation adjustment unit 106, which is provided as a control signal, based on the frequency output by the reference oscillator 102. As a specific setting example, the reference oscillator 102 oscillates at half the frequency of the RTD oscillator 104. Therefore, when oscillating at 0.24 [THz], the RTD oscillator 104 is at 0.48 [THz], so the bias voltage is controlled to be set to 0.69 [V]. Also, when the oscillation frequency is 0.25 [THz], the RTD oscillator 104 is at 0.50 [THz], so the bias voltage is controlled to be set to 0.7 [V]. In this way, the control unit 101 can control the oscillation adjustment unit 106 based on the setting of the reference signal output by the reference oscillator 102 to synchronize the RTD oscillator 104.

[0032] Furthermore, there are cases where it is known in advance that the phase will change due to a delay, such as a delay until the signal output from the reference oscillator 102 reaches the RTD oscillator 104. In such cases, when the control unit 101 adjusts the phase of the RTD oscillator 104, it can correct the phase delay from the reference oscillator 102 to the RTD oscillator 104 by providing a phase adjustment that subtracts the phase change. Alternatively, the signal output from the reference oscillator 102 for synchronizing the RTD oscillator 104 can be branched and input to the control unit 101. In such cases, even if the control unit 101 does not set the reference oscillator 102, it can recognize the frequency, phase, intensity, etc. of the signal provided to the RTD oscillator 104 and feed it back to the oscillation adjustment unit 106. Furthermore, even if the output of the reference oscillator 102 changes depending on the operation of the device, for example, even if the phase or intensity changes due to the influence of a reflected wave or a return signal caused by the oscillation of the RTD oscillator 104, precise feedback control can be performed in response to the fluctuations. Furthermore, although the locking range increases depending on the signal strength of the injection locking, the phase also varies within a range of -90° to +90°. For this reason, it may be possible to change the speed and amount of bias adjustment depending on the signal strength from the reference oscillator 102.

[0033] Alternatively, when the oscillation adjuster 106c described in FIG. 4 is used, a circuit can be configured in which the oscillation adjuster 106c receives a control signal from the control unit 101 and performs control by receiving the output signal of the reference oscillator 102. The control unit 101 can change the ON / OFF control, adjustment amount, adjustment timing, etc., of the oscillation adjuster 106c. This allows the oscillation adjuster 106c to be controlled in accordance with the operation of the reference oscillator 102. In either case, the oscillation adjuster 106c can adjust the oscillation signal for the RTD oscillator 104 in accordance with the operation of the reference oscillator 102, in response to an instruction by a signal from the control unit 101. The control details and feedback signal of the control unit 101, the configuration and frequency of the reference oscillator 102, the frequency division ratio, the bias voltage value, etc. are examples for the purpose of explanation and are not limited to these.

[0034] The equivalent circuit of the device 10 in this embodiment will be described with reference to FIG. 6. The RTD oscillator 104 connects the output potential V1 (330), obtained by dividing the potential of the bias unit 105 using a voltage divider circuit in the oscillation adjustment unit 106, to GND via equivalent circuit elements. The RTD oscillator 104 is a combination of the RTD 108 and the resonant conductor 109, represented by impedance Z2, and the parasitic impedance of the RTD. The reference oscillator 102 is located on the left side of the figure. Between the reference oscillator 102 and the RTD oscillator 104, there is shown a transmission path 331 for the reference signal, which is output by the reference oscillator 102 and synchronizes the RTD oscillator 104. The transmission path 331 includes parasitic inductances L3 and L4, parasitic capacitances C5 and C6, parasitic resistances R3 and R4, and a transmission path impedance Z3. The reference oscillator 102 and the transmission line 331 are electrically connected by AC coupling via a capacitance C4 to pass the signal of the reference oscillator 102. The RTD oscillator 104 and the transmission line 331 are also electrically connected by a capacitance C3 to pass the reference signal.

[0035] The frequency of the reference signal from the reference oscillator 102 is set to half the frequency of the oscillation signal from the RTD oscillator 104, and the capacitance C3 is preferably configured to pass the frequency of the reference signal and block the frequency of the oscillation signal. The control unit 101 is configured to control the oscillation state of the reference oscillator 102 and the variable resistor Rv of the oscillation adjustment unit 106. The RTD oscillator 104 is connected to the antenna 107 via the capacitance C7. The capacitance C7 is preferably connected using a filter such as a capacitance or a fan-shaped radial stub, configured to pass the terahertz band frequency oscillated by the RTD oscillator 104 and block the frequency of the reference signal. Furthermore, the antenna 107 forms a planar antenna such as a patch antenna and is connected at a position slightly offset from the end of the patch antenna to match the impedance with the line. The output of the RTD oscillator 104 forms a standing wave on the antenna 107 and is radiated into space.

[0036] In addition to AC coupling, a filter circuit may be used near the capacitance C7. inj The wavelength of the oscillation signal generated by the RTD oscillator 104 is λ. inj A short stub with a frequency of λ / 4 can be considered. By appropriately placing a short stub at the input end to the RTD oscillator 104, the reference signal frequency is allowed to pass, while the oscillation signal of the RTD oscillator 104 has twice the frequency and is therefore clamped to GND. On the other hand, at the output end of the RTD oscillator 104, which is connected to the antenna, inj An open stub of 1 / 4 is placed in the filter. Because it is an open stub, it is possible to configure a filter that does not pass the frequency of the reference signal but passes the frequency of the oscillation signal, which is twice the frequency. The configuration of the stub filter can be adapted to microwave or millimeter wave circuits, and the scale can be adjusted to match the frequency of the terahertz band, and the filter can be appropriately placed, and is not limited to the description of this embodiment.

[0037] The control unit 101 disposed in the apparatus 10 is implemented not on the semiconductor device 100 but as a separate integrated circuit (IC) on the printed circuit board on which the semiconductor device 100 is mounted. The output of the integrated circuit IC is input to the semiconductor device 100 via wiring on the printed circuit board to control the oscillation adjustment unit 106. However, the arrangement of the control unit 101 to which the present invention can be applied is not limited to this embodiment. It may be implemented as an IC integrated on the same semiconductor chip, or it may be arranged separately on multiple substrates within a semiconductor chip in which multiple semiconductor substrates are stacked. Furthermore, multiple semiconductor chips may be electrically connected using bonding techniques such as flip-chip bonding. In either case, the oscillation signal of the RTD oscillator 104 can be controlled by controlling the oscillation adjustment unit 106 in accordance with the operation of the reference oscillator 102, making it possible to configure a semiconductor device to which the present invention is applied.

[0038] The oscillation adjustment units (106, 106b, 106c, 106d) described in this embodiment This allows for the adjustment of the oscillation signal of the RTD oscillator 104. As a result, the frequency, phase, radiation intensity, beam shape, and other aspects of the terahertz waves 103 output by the device 10 can be selectively or complementarily controlled. Changing the frequency enables digital modulation such as frequency shift keying (FSK) and FM modulation, which can be used for applications such as communications and radar. Changing the phase enables phase shift keying (PSK) and QPSK modulation, while changing the intensity enables AM and intensity shift keying (ASK) modulation. Freely varying the phase and intensity also enables quadrature amplitude modulation and other modulations, depending on the combination. Changing the beam shape allows for beamforming, enabling efficient transmission of the terahertz waves 103 toward the desired receiver. This embodiment not only improves frequency accuracy through injection locking in the RTD oscillator 104, but also adds additional functions such as modulation and beamforming.

[0039] (Second embodiment) In the second embodiment, a device 11 that radiates terahertz waves will be described. FIG. 7 is a block diagram of the second embodiment. In a semiconductor device 100, a reference signal (first synchronization signal) output from a reference oscillator 102 is input to an injection locking unit 110. The injection locking unit 110 outputs signals to an oscillation adjustment unit 106 and an RTD oscillator 104. The RTD oscillator 104 is configured to perform modulation. The modulation is performed by combining a baseband signal 112 with the signal from the RTD oscillator 104, and radiating a modulated terahertz wave 113 from an antenna 107. In addition to the block connections of this embodiment, a power amplifier (PA) that amplifies the radiated terahertz waves, a filter that removes unwanted waves, and the like can also be arranged as appropriate.

[0040] The injection locking unit 110 will now be described. Based on the reference signal (first synchronization signal) output from the reference oscillator 102, the injection locking unit 110 generates an injection locking signal (second synchronization signal) to be injected to synchronize the RTD oscillator 104. The injection locking unit in this embodiment has a phase shifter that changes the phase of the reference signal (first synchronization signal). Figure 8(a) shows the phase shifter disposed in the injection locking unit 110 of this embodiment. Four λ / 4 lines are connected in a loop, and both ends of one λ / 4 line A (340) serve as input 341 and output 342. In addition, variable capacitances are disposed at the connection between λ / 4 line B (343) and λ / 4 line C (344) and at the connection between λ / 4 line C (344) and λ / 4 line D (345), making this a reflective phase shifter.

[0041] FIG. 8(b) shows another example of the injection locking unit 110. For example, a path-switching phase shifter can be used, which switches between two lines (346, 347) with different propagation times using a switch 348 at the input end and a switch 349 at the output end. Other possible phase shifters include loaded line phase shifters and vector sum phase shifters used in millimeter waves and microwaves. Furthermore, an LC low-pass filter (LPF) can be selected by combining multiple lumped constant L·C and FET switches depending on the placement location, the desired phase shift amount, and the corresponding bandwidth. Furthermore, an LP / HP switching type that utilizes the phase difference caused by switching to a high-pass filter (HPF) can also be selected as appropriate.

[0042] The injection locking unit 110 receives a control signal from the control unit 101 and can perform adjustments such as shifting the phase of the injection locking signal (second synchronization signal) from the phase of the reference signal (first synchronization signal) of the reference oscillator. Furthermore, the injection locking unit 110 can perform control closer to the RTD oscillator 104 than the reference oscillator 102. This makes it possible to perform adjustments according to the individual RTD oscillator 104 while taking into account delay times due to the transmission path of the reference signal output from the reference oscillator 102. Furthermore, by appropriately placing a filter or an impedance adjustment circuit between the RTD oscillator 104 and the RTD oscillator 104, it is possible to suppress reflected waves and help the RTD oscillator 104 oscillate stably. Furthermore, the injection locking unit can also be connected to the oscillation adjustment unit 106. By injecting the adjusted synchronization signal (second synchronization signal) and the reference oscillator 102, it is possible to perform feedback by adjusting the bias of the oscillation adjustment unit 106. This allows the oscillation adjustment unit 106 to control itself in accordance with the operation of the reference oscillator 102 and the operation of the injection locked signal (second synchronization signal) generated based on the reference signal (first synchronization signal) output by the operation of the reference oscillator 102.

[0043] In addition to the configuration example of this embodiment, the injection locking unit 110 can also be controlled by a separate control unit. Also, a configuration can be adopted in which a signal is not transmitted directly from the injection locking unit 110 to the oscillation adjustment unit 106. In that case, it is sufficient that the oscillation adjustment unit 106 can perform control in accordance with the operation of the injection locking signal by adjusting the control signal provided to the oscillation adjustment unit 106 based on control information held by the control unit 101 that controls the injection locking unit 110. For example, the control unit may transmit a control signal that does not correspond to the setting value of a synchronization signal that synchronizes the reference oscillator or the RTD oscillator output from the injection locking unit to the oscillation adjustment unit, and the oscillation adjustment unit may perform control in accordance with the synchronization signal. The connection configuration of this embodiment is not particularly limited.

[0044] In addition to the phase shifter, the injection locking unit 110 may also include a branch circuit that branches the signal to the RTD oscillator 104 and the oscillation adjustment unit 106. The branch circuit can be a T-branch circuit, a power divider, a hybrid coupler, or a rat-race circuit, which are typically used in microwave and other high-frequency circuits. Since the output signal strength is halved by equally branching the signal, an amplifier circuit can be provided to compensate for the strength of the injection-locked signal. The injection locking unit 110 can also be provided with a phase-difference detection means that checks the phase of the reference signal output from the reference oscillator 102 and the phase of the injection-locked signal output to the RTD oscillator 104. This allows only a feedback signal corresponding to the phase difference to be sent to the oscillation adjustment unit 106. In either case, the injection locking unit 110 has two main roles. First, it generates an injection-locked signal (second locking signal) that is injection-locked to the RTD oscillator 104 based on the reference signal from the reference oscillator 102. The other is to output to the oscillation adjustment unit 106 information on an injection locked signal (second locking signal) that is injection locked to the RTD oscillator 104. In addition to realizing the above two functions, an amplifier circuit or filter circuit that assists signal transmission, an impedance adjustment circuit that reduces reflected waves, and the like may also be appropriately arranged.

[0045] A baseband signal 112 is input to the RTD oscillator 104 in FIG. 7. The baseband signal is an amplitude-modulated baseband signal with a frequency of 10 [GHz]. The baseband signal 112 is generated by a baseband IC external to the semiconductor device 100 and input. The RTD oscillator 104 generates a 550 [GHz] signal by combining the 10 [GHz] baseband signal with the oscillation signal of the RTD oscillator 104, which has a frequency of 0.5 [THz], i.e., a 500 [GHz] signal. This signal is transmitted to the antenna 107 and radiated into space as terahertz waves 113 to a receiving device (not shown). When the RTD oscillator 104 is used for demodulation, a baseband signal is output based on the oscillation signal of the RTD oscillator 104 and the input signal input from the antenna 107. An appropriate filter or the like may be used in the baseband signal line to select the output signal. Furthermore, it is also possible to provide feedback to the control of the RTD oscillator 104, i.e., the control of the oscillation adjustment unit 106, depending on the baseband signal 112 and the modulation status. It is also possible to switch depending on the information contained in the modulation signal, such as by increasing the power injected by the injection locking unit 110 or adjusting the bias voltage so that the self-oscillation frequency and the frequency of the injection signal approach each other. This makes it possible to eliminate instability, such as the RTD oscillator 104 losing lock, due to a wider modulation bandwidth.

[0046] The baseband signal may be an IF (Intermediate Frequency) signal that has been up-converted before being input, and the frequency, band, and modulation method are appropriately selected depending on the communication system. The number of channels also varies depending on the channels secured for communication by this device. In this embodiment, the explanation is based on modulation to the RTD oscillator, but it is also possible to use a bias tee or the like for the bias voltage from the bias unit to input a baseband signal from the high frequency signal side and modulate it. The modulation / demodulation unit that modulates or demodulates the oscillation signal of the RTD oscillator can be electrically connected to the RTD oscillator. The modulation / demodulation configuration using this invention is not limited to that described above.

[0047] By using the circuit of this embodiment, the RTD oscillator 104 can be used as a local oscillator (LO oscillator) for communications, and terahertz waves can be modulated in response to a modulation signal from a baseband. The oscillation adjustment unit can be adjusted according to the strength and bandwidth of the baseband signal input to the modem. The wider the bandwidth of the baseband signal input to the modem, the more the oscillation adjustment unit can be adjusted to bring the self-oscillation frequency of the RTD oscillator closer to the frequency component contained in the reference signal. By providing the injection locking unit 110, the signal from the reference oscillator 102 can be shaped before injection locking, allowing it to be input to the RTD oscillator 104 in an optimal form. A transmission device can be configured that achieves both improved oscillation accuracy of the RTD oscillator 104 and modulation control.

[0048] (Third embodiment) The terahertz radiation device 12 of the third embodiment shown in FIG. 9 has multiple antennas (107a, 107b, also referred to as array antennas), which differs from the conventional embodiment. Therefore, the RTD oscillators (104a, 104b) connected to the antennas are also arranged in separate sections (two in the figure) equal to the number of antennas. The same applies to the injection locking units (110a, 110b) and oscillation adjustment units (106a, 106b). Meanwhile, the bias unit 105 and GND unit share the same power supply line, but are shown separately for ease of illustration. The two or more antennas (107a, 107b) shown in the figure each emit terahertz waves (113a, 113b), but are arranged in a phased array. The antennas are preferably spaced apart at intervals less than the wavelength of the radiation, preferably λ / 2 or less. This is an embodiment with multiple antennas, and the division of the internal blocks of the semiconductor device 100 is not limited to this.

[0049] The configuration in Figure 9 also has some common parts, even in configurations with multiple antennas. The reference oscillator 102 is common to multiple RTD oscillators (104a, 104b). Because it is a phased array, it is desirable that the reference frequency and phase be generated from the same oscillator, but it is also possible to arrange multiple reference oscillators with adjusted frequencies and phases. The same is true for the baseband input signal 112. To simultaneously radiate the same data from multiple antennas, one baseband input signal 112 is branched and input to two RTD oscillators (104a, 104b). Like the reference oscillator, these may also be input separately, with only synchronization performed. The control unit 101 is connected to control the reference oscillator 102 and two oscillation adjustment units (106a, 106b).

[0050] Although FIG. 9 shows two separate blocks, some parts can be shared. For example, the injection locking units (110a, 110b) are arranged separately for each RTD oscillator (104a, 104b), but they can also be made into a single shared module. By sharing the blocks, the wiring for the reference signal from the reference oscillator 102 can be simplified. In the case of a shared block, a Butler matrix circuit or the like can be used in the injection locking unit, enabling a configuration in which the phase from the reference oscillator 102 is distributed to multiple RTD oscillators 104 with a phase difference. Furthermore, it becomes possible to check the phase shift between multiple RTD oscillators (104a, 104b) and perform individual adjustments in the oscillation adjustment units (106a, 106b). This allows for more accurate phase adjustment between the array antennas. In the oscillation adjustment units (106a, 106b), In addition to the same control as in the conventional embodiment in which the RTD oscillators are individually controlled, the bias voltage coming from the bias unit 105 can be adjusted as a common adjustment according to the mutual operating states of the RTD oscillators (104a, 104b).

[0051] By matching the phase between the array antennas, the oscillation adjusters (106a, 106b) can generate a terahertz wave beam with directivity in the vertically upward direction (right side in Figure 9) of the plane where the array is arranged. This is because the terahertz waves (113a, 113b) emitted from the array antennas oscillate in phase, resulting in signal reinforcement in that direction. On the other hand, by slightly delaying the phase of antenna 107a compared to that of antenna 107b, the emitted beam can be tilted toward antenna 107a (upper right side in Figure 9). Phase control enables beamforming of the phased array antenna. This also allows for separate modulation by the baseband signal 112 and beamforming control performed by the oscillation adjusters (106a, 106b). The relationship between the phase difference between antennas and the scan angle during beamforming is expressed as sinθ = (λφ) / (2πd). Here, θ is the beam radiation angle, λ is the wavelength of the radiated electromagnetic wave, φ is the phase difference, and d is the array antenna pitch. When the antenna pitch d=λ / 2 and the phase difference φ=π / 2, it is possible to radiate a beam with a radiation angle of θ=π / 6, or 30 degrees.

[0052] According to the third embodiment, phase control such as beamforming using an antenna array can be achieved by the oscillation adjustment units (106a, 106b). By adopting this embodiment, injection locking using a signal from the reference oscillator 102 can be achieved, and beamforming with a phase shift between the RTD oscillators can also be performed while stabilizing the oscillation of the RTD oscillators (104a, 104b). This allows for high performance of the terahertz oscillator.

[0053] (Fourth embodiment) FIG. 10 is a block diagram showing an overview of the device 13 of this embodiment. Unlike the conventional embodiment, this device is equipped with four antennas (107a, 107b, 107c, and 107d). The four antennas are arranged vertically and horizontally in a matrix, forming a 2-row, 2-column array. This terahertz transmitter radiates a beam in the vertical direction based on the two-dimensional plane (defined in the same direction as the paper surface) of this antenna array. The number of arrays shown here is just an example, and can be appropriately realized with an array arrangement of N rows and M columns (where N and M are the same or different natural numbers). Two injection locking units (110c and 110d) receive a reference signal output from a common reference oscillator 102. The injection locking unit 110c is configured to perform injection locking on the RTD oscillators (104a and 104c) in a horizontal row, and the injection locking unit 110d is configured to perform injection locking on the RTD oscillators (104b and 104d) in another horizontal row. Furthermore, two systems of oscillation adjusters (106c, 106d) are provided. The oscillation adjuster 106c is configured to adjust one vertical row of RTD oscillators (104a, 104b), and the other oscillation adjuster 106d is configured to adjust another vertical row of RTD oscillators (104c, 104d). When divided into a first group including one or more RTD oscillators and a second group including another one or more RTD oscillators in this way, a common oscillation adjuster and injection locking unit can be used within each group.

[0054] The injection locking units (110c, 110d) input a reference signal from the reference oscillator 102 and convert it into a signal that is injection locked to each RTD oscillator. By shifting the relative phase difference between the injection locking units 110c and 110d, vertical beamforming can be achieved in a 2x2 array. In addition, adjustments by the oscillation tuning units (106c, 106d) can adjust the phase of one or more adjacent RTD oscillators (104a, 104b, 104c, 104d). This allows beamforming in the horizontal direction to be achieved by relatively changing the phase of the oscillation tuning units 106c and 106d. By combining these, the direction of the beam emerging from the plane can be freely set.

[0055] In addition, since there is no need to arrange individual circuits corresponding to all the RTD oscillators (104a, 104b, 104c, 104d), common wiring can be achieved, and the circuit layout can be performed efficiently. When the wavelength of the terahertz wave is 0.5 GHz, the wavelength λ is 0.6 mm. Therefore, when arranging the antennas (107a, 107b, 107c, 107d) at a pitch of λ / 2 or less, the layout constraints and the increase in loss due to the circuit structure around the antenna are likely to lead to a decrease in efficiency. Therefore, by dividing the antennas into a plurality of groups and performing common control within the groups, simplification of the circuit and wiring can be realized. It is also possible to take measures such as wiring by dividing the groups into vertical and horizontal rows as shown in FIG. 9, or providing a common injection synchronization unit and oscillation adjustment unit in the horizontal row. Furthermore, it is also possible to control an N-row N-column array antenna as an M-row M-column (M < N, M, N are natural numbers) array antenna group. As a result, the number of each of the oscillation adjustment unit and the injection synchronization unit can be made N×N or less. In a specific example, for a 4×4 array antenna, it is possible to take measures such as providing four 2-row 2-column groups and controlling them individually.

[0056] By using the circuit of this embodiment, appropriate injection synchronization can be performed for the RTD oscillators (104a, 104b, 104c, 104d) even for a two-dimensional array antenna, and control by the oscillation adjustment unit can be realized. As a result, the loss due to deterioration of the layout property can be suppressed.

[0057] (Fifth Embodiment) FIG. 11(a) is a block diagram showing the apparatus 14 of this embodiment. The RTD oscillator 114 includes a patch antenna 115 that also serves as a resonator and a radiator in addition to the RTD 108. The patch antenna 115 has a resonance structure that resonates the oscillation signal of the RTD oscillator 114, and further functions as an antenna that radiates the in-plane resonated electromagnetic wave into space. The terahertz wave 103 radiated into space is received by a receiving device (not shown) on the opposite side. In this embodiment, a single RTD oscillator 114 is used, but it is also possible to configure a one-dimensional array antenna in which a plurality of them are arranged in a row or a two-dimensional array antenna arranged on a plane.

[0058] FIG. 11(b) is a schematic diagram showing the structure of the RTD oscillator 114 on a semiconductor substrate. The bias and adjustment value input from the oscillation adjustment unit 106 are transmitted to the vicinity of the patch antenna 115 via a conductor layer 120 and input to the patch antenna 115 via a via 121. The patch antenna 115 is composed of an upper conductor layer 122 for radiation, a lower conductor layer 123 for GND, and a dielectric layer 124 disposed between the upper conductor layer 122 and the lower conductor layer 123. The GND is connected to the lower conductor layer 123 to determine the reference potential. The RTD 108 is disposed between the upper conductor layer 122 and the lower conductor layer 123. The RTD 108 can be disassembled to include an RTD layer 125 that forms the RTD device, a via or conductor layer 126 that connects to the upper conductor layer 122, and a conductor layer 127 that connects to the lower conductor layer 123. The bias and adjustment value input to the patch antenna 115 are connected to the RTD layer 125 via the upper conductor layer 122, and a bias potential due to the potential difference with GND is applied to the RTD 108. Although a signal from the reference oscillator 102 is not shown, it is input via AC connection to the RTD 108 or one of the conductor layers so as to pass the vicinity of the frequency band of the signal oscillated and output by the reference oscillator 102. These elements are formed by stacking and patterning on a semiconductor substrate 128 using semiconductor integration technology. A dielectric layer 129 arranged on the upper side of the upper conductor layer 122 is a protective layer to protect this semiconductor device.

[0059] By integrating the RTD oscillator 114 with the antenna to form an active antenna, the signal oscillated by the RTD 108 can be connected to the radiator (patch antenna 115) via a short line. In this case, the conductor for resonance can also serve as the antenna. In the frequency band of the terahertz wave 103, conductor loss and dielectric loss due to wiring on the board are major causes of output reduction. Therefore, the device of this embodiment not only becomes a compact and small device, but also realizes a configuration that allows efficient radiation with low loss.

[0060] (Other embodiments) Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0061] For example, while the above-described embodiment describes a transmitter in a wireless communication device as an example, the application is not limited thereto and may be, for example, a radar device. For FMCW radar, constant frequency sweeping is required. The output frequency of the reference oscillator 102 may be swept using the circuit of the first embodiment shown in FIG. 1 , and an oscillation signal may be generated and emitted by the RTD oscillator 104. In this case, problems may arise, such as an increase in the frequency sweep width causing injection locking to be lost, or a change in the phase of the oscillation signal of the RTD oscillator 104 due to a frequency difference with the self-oscillation. The oscillation adjustment unit can eliminate frequency and phase instability by appropriately adjusting the bias of the RTD oscillator 104 according to the frequency of the signal output by the reference oscillator 102.

[0062] Although the above-described embodiment uses a square patch antenna as the terahertz wave antenna, the shape of the antenna is not limited to this. For example, a patch conductor having a polygonal shape such as a rectangle or a triangle, a circle, an ellipse, or the like, a planar antenna such as a loop antenna, a log-periodic antenna, or a Vivaldi antenna, or a horn antenna may also be used.

[0063] Furthermore, for example, in the above-described embodiment, an example is described in which one RTD is arranged for one RTD oscillator, but it is also possible to arrange multiple RTDs and oscillate them simultaneously in the resonator using a push-push method or a push-pull method. Also, although the description has been given with one antenna associated with one RTD oscillator, multiple connections such as 1:N, N:1, or N:N (N is a natural number) may be wired.

[0064] Although the structure of the RTD oscillator has been described using a laminated structure, the present invention is not limited to this, and the above discussion can also be applied to oscillator devices that do not use a laminated structure. Furthermore, the following combinations may be used as materials for the RTD. GaAs / AlGaAs, GaAs / AlAs, InGaAs / GaAs / AlAs formed on GaAs substrate InGaAs / InAlAs, InGaAs / AlAs, InGaAs / AlGaAsSb formed on InP substrate InAs / AlAsSb and InAs / AlSb grown on InAs substrates ·SiGe / SiGe formed on a Si substrate The above-mentioned structure and materials can be appropriately selected depending on the desired frequency and the like.

[0065] A case where the semiconductor device according to any of the above-described embodiments is applied to a terahertz camera system (imaging system) will be described. The following description will be made with reference to FIG. 12(a). The terahertz camera system 1100 has a transmitter 1101 that emits terahertz waves TW and a receiver 1102 that detects the terahertz waves TW. The terahertz camera system 1100 further has a controller 1103 that controls the operation of the transmitter 1101 and receiver 1102 based on an external signal, and processes an image based on the detected terahertz waves or outputs the image to the outside. The semiconductor device in each embodiment may be the transmitter 1101 or the receiver 1102. The terahertz waves emitted from the transmitter 1101 are reflected by a subject 1105 and detected by the receiver 1102. A camera system having such a transmitter 1101 and receiver 1102 may also be called an active reflection imaging camera system. The transmitter 1101 A transmission imaging system can also be considered in which the transmitter 101 and the receiver 1102 are opposed to each other and a subject is placed between them, thereby observing the terahertz waves that have passed through the subject. Note that in a passive camera system that does not have the transmitter 1101, the antenna device of each of the above-described embodiments can be used as the receiver 1102. By using the antenna device of each of the embodiments that is capable of beamforming, it is possible to improve the detection sensitivity of the camera system and obtain high-quality images.

[0066] A case where the semiconductor device according to any of the above-described embodiments is applied to a terahertz communication system (communication device) will be described. The following description will be given with reference to Figure 12(b). The device can be used as a component of a communication system. Assumed communication systems include a simple ASK system, a superheterodyne system, a direct conversion system, and the like. A superheterodyne communication system includes, for example, an antenna 1200, an amplifier 1201, a mixer 1202, a filter 1203, a mixer 1204, a converter 1205, a digital baseband modulator / demodulator 1206, and local oscillators (1207, 1208).

[0067] In the receiver, terahertz waves received via antenna 1200 are converted into an intermediate frequency signal by mixer 1202. Then, the terahertz waves are converted into a baseband signal by mixer 1204, and the analog waveform is converted into a digital waveform by converter 1205. The digital waveform is then demodulated at baseband to obtain a communication signal.

[0068] In the transmitter, a communication signal is modulated and then converted from a digital waveform to an analog waveform by converter 1205, then frequency converted via mixer 1204 and mixer 1202, and output as a terahertz wave from antenna 1200. A direct conversion communication system includes antenna 1200, amplifier 1211, mixer 1212, modulator / demodulator 1213, and local oscillator 1214. In the direct conversion system, upon reception, terahertz waves received by mixer 1212 are directly converted into a baseband signal, and upon transmission, mixer 1212 converts the baseband signal to be transmitted into a terahertz band signal. The other configurations are the same as those of the superheterodyne system.

[0069] The devices according to the above-described embodiments can perform terahertz wave beamforming by electrically controlling semiconductor devices. This allows for alignment of radio waves between transmitters and receivers. Therefore, by using the antenna devices according to the embodiments capable of beamforming, wireless quality such as signal-to-noise ratio can be improved in communication systems, enabling large-volume information transmission over a wide coverage area at low cost. Furthermore, if the same local oscillator can be used for transmission and reception to perform frequency sweeps, an FMCW radar device can be used to measure distance based on delay and phase information between the transmitted signal and the reflected wave. For example, distance can be determined by emitting electromagnetic waves from a transmitter, reflecting the radiated electromagnetic waves (radiated waves) off an object, detecting the reflected waves with a receiver, and measuring the distance based on the radiated and reflected waves. Applying the present invention improves wireless quality such as signal-to-noise ratio, improving ranging accuracy, and enabling this to be done at low cost.

[0070] The embodiments described above can be modified as appropriate without departing from the spirit and scope of the present invention. The disclosure of this specification includes not only what is described in this specification, but also all matters that can be understood from this specification and the drawings attached hereto.

[0071] The disclosure of this embodiment includes the following configuration. (Configuration 1) an RTD oscillator, a reference oscillator that synchronizes the RTD oscillator, an oscillation adjustment unit that adjusts the oscillation signal of the RTD oscillator, and a control unit that controls the reference oscillator and the oscillation adjustment unit; and wherein the oscillation adjustment unit is controlled in accordance with the operation of the reference oscillator by a control signal from the control unit. (Configuration 2) 2. The semiconductor device according to configuration 1, wherein the control unit generates the control signal to the oscillation adjustment unit in accordance with the operation of the reference oscillator. (Configuration 3) 3. The semiconductor device according to configuration 1 or 2, wherein the oscillation adjustment unit is controlled using a synchronization signal that is output from the reference oscillator and that synchronizes the RTD oscillator. (Configuration 4) The semiconductor device according to any one of configurations 1 to 3, characterized in that the oscillation adjustment unit is controlled based on a transmission delay or phase change with respect to the output of the reference oscillator using a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator. (Configuration 5) The semiconductor device according to any one of configurations 1 to 4, further comprising a bias unit that applies a bias, wherein the oscillation adjustment unit is electrically connected to the bias unit and the RTD oscillator and adjusts the bias of the RTD oscillator. (Configuration 6) 6. The semiconductor device according to any one of configurations 1 to 5, wherein the oscillation adjustment unit checks a reflected signal reflected from the RTD oscillator against a synchronization signal that synchronizes the RTD oscillator. (Configuration 7) 7. The semiconductor device according to claim 6, wherein the oscillation adjustment unit determines a bias potential that serves as a reference for the RTD oscillator from the reflected signal. (Configuration 8) The semiconductor device according to any one of configurations 1 to 7, wherein the control unit inputs a control signal to the oscillation adjustment unit, the control signal corresponding to a setting value of a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator. (Configuration 9) The semiconductor device according to any one of configurations 1 to 8, wherein the control unit inputs a control signal that does not correspond to a setting value of a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator to the oscillation adjustment unit, and the oscillation adjustment unit performs control according to the synchronization signal. (Configuration 10) The semiconductor device according to any one of configurations 1 to 9, further comprising an injection locking unit, wherein the injection locking unit injects a second synchronization signal into the RTD oscillator to synchronize the RTD oscillator based on a first synchronization signal output from the reference oscillator. (Configuration 11) 11. The semiconductor device according to configuration 10, wherein the control unit controls the injection locking unit and controls the oscillation adjustment unit in accordance with the operation of the injection locking unit. (Configuration 12) 12. The semiconductor device according to configuration 10 or 11, wherein the injection locking unit adjusts a delay time, a phase, or an intensity of the first synchronization signal, and injects the second synchronization signal, which is the adjusted synchronization signal, into the RTD oscillator. (Configuration 13) 13. The semiconductor device according to any one of configurations 10 to 12, wherein the injection locking unit outputs a signal to the oscillation adjustment unit that corresponds to the delay time, phase, or intensity of the signal to be output to the RTD oscillator. (Configuration 14) The control unit provides the oscillation adjustment unit with a control signal that does not correspond to a set value of a synchronization signal that synchronizes the reference oscillator or the RTD oscillator output from the injection locking unit, 14. The semiconductor device according to any one of configurations 10 to 13, wherein the adjustment section performs control in accordance with the synchronization signal. (Configuration 15) 15. The semiconductor device according to any one of configurations 1 to 14, wherein the oscillation adjustment unit includes an impedance adjustment means electrically connected to the RTD oscillator and adjusting the impedance of the RTD oscillator. (Configuration 16) 16. The semiconductor device of claim 15, wherein the impedance adjusting means comprises a circuit including a varactor diode. (Configuration 17) 17. The semiconductor device according to any one of configurations 1 to 16, wherein the RTD oscillator has a configuration in which one or more RTDs and a conductor for resonance are electrically connected. (Configuration 18) 18. The semiconductor device according to any one of configurations 1 to 17, wherein the RTD oscillator is electrically connected to one or more antennas, and the antennas emit or detect electromagnetic waves comprising the oscillation signal. (Configuration 19) 18. The semiconductor device according to configuration 17, wherein the RTD oscillator is an active antenna, and the conductor for resonance also serves as an antenna. (Configuration 20) 20. The semiconductor device according to any one of configurations 1 to 19, further comprising a modulation / demodulation unit that modulates or demodulates an oscillation signal of the RTD oscillator, the modulation / demodulation unit being electrically connected to the RTD oscillator. (Configuration 21) 21. The semiconductor device according to configuration 20, wherein the oscillation adjuster adjusts the oscillation according to the intensity or bandwidth of a baseband signal input to the modem. (Configuration 22) 22. The semiconductor device according to configuration 20 or 21, characterized in that the wider the bandwidth of the baseband signal input to the modem unit, the more the oscillation adjustment unit adjusts the self-oscillation frequency of the RTD oscillator and the frequency component included in the reference signal so as to approach each other. (Configuration 23) 23. The semiconductor device according to any one of configurations 1 to 22, wherein the oscillation adjustment section changes the phase of a signal that resonates in the RTD oscillator by adjusting the bias. (Configuration 24) 24. The semiconductor device according to any one of configurations 1 to 23, wherein the oscillation adjustment unit changes the phase or intensity of a signal that resonates in the RTD oscillator by adjusting the impedance of the RTD oscillator. (Configuration 25) 25. The semiconductor device according to any one of configurations 1 to 24, wherein the RTD oscillator is injection-locked to a subharmonic frequency that oscillates in synchronization with a harmonic component of the reference frequency of the reference oscillator. (Configuration 26) The semiconductor device according to any one of configurations 1 to 25, characterized in that, while the frequency is changed by the reference oscillator, the oscillation adjustment unit adjusts the bias potential to be synchronized with the harmonic component of the frequency output from the reference oscillator and applies a bias to the RTD oscillator. (Configuration 27) 27. The semiconductor device according to any one of configurations 1 to 26, wherein the bias potential of the RTD oscillator is set in a negative resistance region of the RTD. (Configuration 28) 28. The semiconductor device according to any one of configurations 18 to 27, comprising a plurality of combinations of the RTD oscillator and the antenna connected to the RTD oscillator. (Configuration 29) 29. The semiconductor device according to claim 28, wherein the oscillation adjustment unit adjusts the phase difference between the signals radiated from the plurality of antennas. (Configuration 30) 30. The semiconductor device according to any one of configurations 1 to 29, wherein the oscillation signal generated by the RTD oscillator includes a signal having a frequency ranging from 0.3 THz to 0.6 THz. (Configuration 31) 31. The semiconductor device according to any one of configurations 1 to 30, wherein the signal strength output from the reference oscillator is greater than the output from the RTD oscillator. (Configuration 32) A semiconductor device according to any one of configurations 1 to 31, characterized in that it comprises a plurality of the RTD oscillators arranged in N rows and M columns (N and M are natural numbers), and the number of each of the oscillation adjustment units and the injection locking units is N×M or less. (Configuration 33) The semiconductor device according to any one of configurations 10 to 32, characterized in that when the device is divided into a first group including one or more RTD oscillators and a second group including one or more other RTD oscillators, the RTD oscillators in the first group are each connected to the oscillation adjustment unit that is common within the group, and the RTD oscillators in the second group are each connected to the injection locking unit that is common within the group. (Configuration 34) The semiconductor device according to any one of configurations 1 to 33, comprising a plurality of the RTD oscillators arranged in N rows and M columns (N and M are natural numbers), and performing beamforming by changing the phase difference between the oscillation signals of one or more adjacent RTD oscillators. (Configuration 35) 35. The semiconductor device according to any one of configurations 1 to 34, comprising a common reference oscillator for the plurality of RTD oscillators. (Configuration 36) 36. The semiconductor device according to any one of configurations 1 to 35, further comprising a plurality of reference oscillators for the plurality of RTD oscillators, wherein at least two of the reference oscillators have the same frequency and phase. (Configuration 37) 37. The semiconductor device according to any one of configurations 18 to 36, wherein the antenna is a square patch antenna. (Configuration 38) 38. The semiconductor device according to any one of configurations 18 to 37, wherein the electromagnetic wave has a frequency in the terahertz band. (Configuration 39) 39. The semiconductor device according to any one of configurations 1 to 38, wherein the RTD oscillator is a microstrip line resonator. (Configuration 40) The semiconductor device of any one of configurations 1 to 39; a transmitter that emits electromagnetic waves; a receiving unit that detects electromagnetic waves; A communication device comprising: (Configuration 41) The semiconductor device of any one of configurations 1 to 39; a transmitter that emits electromagnetic waves toward a subject; a receiving unit that detects the electromagnetic waves reflected from or transmitted through the subject; An imaging system comprising: (Configuration 42) The semiconductor device of any one of configurations 1 to 39; a transmitter that emits electromagnetic waves; a receiving unit that detects reflected waves of the emitted electromagnetic waves; Measuring distance from emitted and reflected waves A radar device characterized by: [Explanation of symbols]

[0072] 100 Semiconductor Devices 101 Control section 102 Reference Oscillator 104 RTD Oscillator 106 Oscillation adjustment unit

Claims

1. A semiconductor device comprising: an RTD oscillator; a reference oscillator that synchronizes the RTD oscillator; an oscillation adjustment unit that adjusts the oscillation signal of the RTD oscillator; and a control unit that controls the reference oscillator and the oscillation adjustment unit, wherein the oscillation adjustment unit is controlled in accordance with the operation of the reference oscillator by a control signal from the control unit.

2. 2. The semiconductor device according to claim 1, wherein the control unit generates the control signal to the oscillation adjustment unit in response to an operation of the reference oscillator.

3. 2. The semiconductor device according to claim 1, wherein the oscillation adjustment unit is controlled using a synchronization signal that is output from the reference oscillator and synchronizes the RTD oscillator.

4. 2. The semiconductor device according to claim 1, wherein the oscillation adjustment unit is controlled based on a transmission delay or phase change with respect to the output of the reference oscillator using a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator.

5. 2. The semiconductor device according to claim 1, further comprising a bias section that applies a bias, wherein the oscillation adjustment section is electrically connected to the bias section and the RTD oscillator and adjusts the bias of the RTD oscillator.

6. 2. The semiconductor device according to claim 1, wherein the oscillation adjustment unit checks a reflected signal reflected from the RTD oscillator against a synchronization signal that synchronizes the RTD oscillator.

7. 7. The semiconductor device according to claim 6, wherein the oscillation adjustment unit determines a bias potential that serves as a reference for the RTD oscillator from the reflected signal.

8. 2. The semiconductor device according to claim 1, wherein the control unit inputs a control signal to the oscillation adjustment unit, the control signal corresponding to a set value of a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator.

9. 2. The semiconductor device according to claim 1, wherein the control unit inputs a control signal that does not correspond to a set value of a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator to the oscillation adjustment unit, and the oscillation adjustment unit performs control in accordance with the synchronization signal.

10. 2. The semiconductor device according to claim 1, further comprising an injection locking unit, wherein the injection locking unit injects a second synchronization signal into the RTD oscillator to synchronize the RTD oscillator based on a first synchronization signal output from the reference oscillator.

11. The semiconductor device according to claim 10 , wherein the control unit controls the injection locking unit, and controls the oscillation adjustment unit in response to an operation of the injection locking unit.

12. 11. The semiconductor device according to claim 10, wherein the injection locking unit adjusts a delay time, a phase, or an intensity of the first synchronization signal, and injects the second synchronization signal, which is the adjusted synchronization signal, into the RTD oscillator.

13. 11. The semiconductor device according to claim 10, wherein the injection locking unit outputs a signal to the oscillation adjustment unit that corresponds to a delay time, a phase, or an intensity of a signal output to the RTD oscillator.

14. The semiconductor device according to claim 10, wherein the control unit provides the oscillation adjustment unit with a control signal that does not correspond to a set value of a synchronization signal that synchronizes the reference oscillator or the RTD oscillator output from the injection locking unit, and the oscillation adjustment unit performs control in accordance with the synchronization signal.

15. 2. The semiconductor device according to claim 1, wherein the oscillation adjustment section includes an impedance adjustment means electrically connected to the RTD oscillator and adjusting the impedance of the RTD oscillator.

16. 16. The semiconductor device of claim 15, wherein the impedance adjusting means comprises a circuit including a varactor diode.

17. 2. The semiconductor device according to claim 1, wherein the RTD oscillator has a configuration in which one or more RTDs are electrically connected to a conductor for resonance.

18. 2. The semiconductor device of claim 1, wherein the RTD oscillator is electrically connected to one or more antennas, the antennas emitting or detecting electromagnetic waves comprising the oscillating signal.

19. 18. The semiconductor device according to claim 17, wherein the RTD oscillator is an active antenna, and the conductor for resonance also serves as the antenna.

20. 2. The semiconductor device according to claim 1, further comprising a modulation / demodulation unit that modulates or demodulates an oscillation signal of the RTD oscillator, the modulation / demodulation unit being electrically connected to the RTD oscillator.

21. 21. The semiconductor device according to claim 20, wherein the oscillation adjustment unit adjusts the oscillation in accordance with the intensity or bandwidth of a baseband signal input to the modulation / demodulation unit.

22. The semiconductor device according to claim 21, wherein the wider the bandwidth of the baseband signal input to the modulation / demodulation unit, the more the oscillation adjustment unit adjusts the self-oscillation frequency of the RTD oscillator and the frequency component contained in the reference signal so as to approach each other.

23. 6. The semiconductor device according to claim 5, wherein the oscillation adjustment section changes the phase of the signal that resonates in the RTD oscillator by adjusting the bias.

24. 16. The semiconductor device according to claim 15, wherein the oscillation adjustment unit changes the phase or intensity of a signal that resonates in the RTD oscillator by adjusting the impedance of the RTD oscillator.

25. 2. The semiconductor device according to claim 1, wherein the RTD oscillator is injection-locked to a subharmonic frequency that oscillates in synchronization with a harmonic component of the reference frequency of the reference oscillator.

26. 2. The semiconductor device according to claim 1, wherein, while the frequency is changed by the reference oscillator, the oscillation adjustment unit adjusts the bias potential to synchronize with a harmonic component of the frequency output from the reference oscillator and applies a bias to the RTD oscillator.

27. 6. The semiconductor device according to claim 5, wherein the bias potential of the RTD oscillator is set in a negative resistance region of the RTD.

28. 19. The semiconductor device according to claim 18, comprising a plurality of combinations of the RTD oscillator and the antenna connected to the RTD oscillator.

29. 29. The semiconductor device according to claim 28, wherein the oscillation adjustment section adjusts the phase difference between the signals radiated from the plurality of antennas.

30. 2. The semiconductor device according to claim 1, wherein the oscillation signal generated by the RTD oscillator includes a signal having a frequency ranging from 0.3 THz to 0.6 THz.

31. 2. The semiconductor device according to claim 1, wherein the signal strength output from said reference oscillator is greater than the output from said RTD oscillator.

32. 11. The semiconductor device according to claim 10, comprising a plurality of the RTD oscillators arranged in N rows and M columns (N and M are natural numbers), and the number of each of the oscillation adjustment units and the injection locking units is N×M or less.

33. 11. The semiconductor device according to claim 10, wherein when the RTD oscillators are divided into a first group including one or more RTD oscillators and a second group including one or more other RTD oscillators, the RTD oscillators in the first group are each connected to the oscillation adjustment unit that is common within the group, and the RTD oscillators in the second group are each connected to the injection locking unit that is common within the group.

34. 2. The semiconductor device according to claim 1, further comprising a plurality of the RTD oscillators arranged in N rows and M columns (N and M are natural numbers), and performing beamforming by changing the phase difference between the oscillation signals of one or more adjacent RTD oscillators.

35. 2. The semiconductor device according to claim 1, further comprising a common reference oscillator for a plurality of said RTD oscillators.

36. 2. The semiconductor device according to claim 1, further comprising a plurality of reference oscillators for the plurality of RTD oscillators, wherein at least two of the reference oscillators have the same frequency and phase.

37. 20. The semiconductor device of claim 18, wherein the antenna is a square patch antenna.

38. 19. The semiconductor device according to claim 18, wherein the electromagnetic wave has a frequency in the terahertz band.

39. 2. The semiconductor device of claim 1, wherein the RTD oscillator is a microstripline resonator.

40. A semiconductor device according to any one of claims 1 to 39; a transmitter that emits electromagnetic waves; a receiving unit that detects electromagnetic waves; A communication device comprising:

41. A semiconductor device according to any one of claims 1 to 39; a transmitter that emits electromagnetic waves toward a subject; a receiving unit that detects the electromagnetic waves reflected from or transmitted through the subject; An imaging system comprising:

42. A semiconductor device according to any one of claims 1 to 39; a transmitter that emits electromagnetic waves; a receiving unit that detects reflected waves of the emitted electromagnetic waves; Measuring distance from emitted and reflected waves A radar device characterized by:

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