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

Abstract

A semiconductor device comprising an RTD oscillator, a reference oscillator for synchronizing the RTD oscillator, an oscillation adjustment unit for adjusting an oscillation signal of the RTD oscillator, and a control unit for controlling the reference oscillator and the oscillation adjustment unit, and characterized in that the oscillation adjustment unit is controlled in accordance with an operation of the reference oscillator by a signal from the control unit.

Description

Semiconductor devices, communication devices, imaging systems and radar devices

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

[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.

[0003] JP 2023-157737 A

[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.

[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.

[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.

[0007] FIG. 1 is a block diagram according to a first embodiment. FIGS. 2(a) and 2(b) are graphs showing the characteristics of injection locking in an RTD oscillator. FIGS. 3(a) and 3(b) are schematic diagrams showing a configuration example of bias adjustment by an oscillation adjustment unit. FIG. 4 is a schematic diagram showing a configuration example of feedback control by an oscillation adjustment unit. FIG. 5 is a schematic diagram showing a configuration example of an impedance adjustment circuit by an oscillation adjustment unit. FIG. 6 is a diagram showing an example of an equivalent circuit of an RTD oscillator and its peripheral components. FIG. 7 is a block diagram according to a second embodiment. FIGS. 8(a) and 8(b) are schematic diagrams showing a configuration example of phase adjustment in an injection locking unit. FIG. 9 is a block diagram according to a third embodiment. FIG. 10 is a block diagram according to a fourth embodiment. FIGS. 11(a) and 11(b) are block diagrams according to a fifth embodiment. FIGS. 12(a) and 12(b) are schematic diagrams showing configuration examples according to other embodiments.

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

[0009] 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 in a frequency range of 10 GHz to 100 THz, more preferably 30 GHz to 30 THz.

[0011] The RTD oscillator 104 is composed of an RTD 108, which is an oscillation source, and a resonant conductor 109 having 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 the resonant structure. The oscillation signal generated by the RTD oscillator can include a signal with a frequency 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 the oscillation frequency f of the terahertz waves. 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 frequency is changed by the reference oscillator, 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 greater 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 the output P ＲＴＤ It is desirable that the value is equal to or greater than ((3 / 16)cosωτ×ΔIΔV). Here, P ＲＴＤis 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 mounted inside the RTD oscillator 104, and it is preferable that the power summed up for the number of mounted RTDs is 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 ＲＴＤ In 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 one ten-thousandth of the output of one RTD. ＲＴＤ Even when using a reference oscillator 102 having an output smaller than ((3 / 16)cosωτ×ΔIΔV), it is possible to synchronize the RTD oscillator 104 while maintaining the frequency accuracy output by the reference oscillator 102. 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 for adjusting the voltage and current when the RTD oscillator 104 oscillates, as well as controlling 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, since the wavelength λ of 0.5 THz is 0.6 mm, and 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 that of 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 is in 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 and stabilizing the frequency of the RTD oscillator 104 is called injection locking. In this embodiment, the RTD oscillator 104 utilizes 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 examine the self-oscillation frequency of the RTD 108. The non-injection locked plot 202 in FIG. 2( a) shows that oscillation occurs at 0.5 THz when the bias potential is 0.7 V. It can be seen that the self-oscillation frequency shifts downward when the bias potential is lowered, and shifts upward when the bias potential is increased. Next, let us examine the injection locked plot 201. At a bias potential of 0.7 V, the frequency is 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 a 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 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 of the reference oscillator 102 input to the RTD oscillator 104 is strong, and conversely, when it is weak, the voltage range becomes narrow.

[0021] FIG. 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 in the -90° direction, and as the bias potential is raised, the phase changes in the +90° direction. This means that the self-oscillation frequencies of the reference oscillator 102 and the 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 ) × (f １ -f ０ ) / (f １ ))). φ is the oscillation phase of the RTD oscillator 104, and Pi is the oscillation power. Po is the oscillation power of the harmonic component of the reference signal input from the reference oscillator and synchronized, and Q is the Q value of the RTD oscillator 104. The sharper the frequency spectrum, the higher the Q value, and it is used as an output index of the oscillation circuit. f １ is the self-oscillation frequency, and f ０is the frequency oscillated by injection locking, i.e., the oscillation frequency of the reference oscillator 102. As can be seen from the formula, this phase difference varies within the range of -90° to +90°. In other words, it can be said that the phase difference within the locking range varies within the range of -90° to +90°, and the width of the locking range varies depending on the ratio of the oscillation power and injection power of the injection-locked oscillator.

[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. 3A shows 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 resistor R1 (301) and finally 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 resistor R1 (301) and variable resistor Rv (303). A control signal from the control unit 101 is input to an input port 304 of the variable resistor Rv (303), and the resistance value of the variable resistor Rv (303) is adjusted based on the signal. The bias potential applied to the RTD oscillator 104 can be controlled by adjusting the resistance of the variable resistor Rv (303). The RTD oscillator 104 can change the phase of the oscillating signal by changing the bias potential.

[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 formed between the inductor L1 and the output port 302, and a capacitor C1 (306) is connected to the branch. The inductor L1 (305) and capacitor C1 (306) function as a bias tee, and can output a signal to the output port 302 that is a superposition of a DC component from the bias unit 105 and an AC component from the capacitor C1 (306). 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 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 can adjust 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 performing time-varying beam scanning. 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 changing 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, since the self-oscillation frequency changes as shown in FIG. 2(a), the bias potential at this time requires voltage adjustment according to the frequency. 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 this 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. Since 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] FIG. 4 shows a block diagram illustrating another adjustment method for the oscillation adjustment unit 106c. The oscillation adjustment unit 106c is connected from the bias unit 105 to the output port 302 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 circuit becomes the same as that shown in FIG. 3(a). An adjustment circuit 314 is connected to the other terminal of the switch 317. 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 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. For this purpose, a configuration in which the output signal of the reference oscillator 102 is input for control is conceivable. 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. A switch 321 is connected to the terminal of Z2 opposite Z1. A control signal input from the control unit 101 to the oscillation adjustment unit 106d is connected to the switch 321 via the input port 318, and controls the ON / OFF of the switch. 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 having a variable capacitance Cv are connected between GND. To adjust the capacitance of the variable capacitance Cv, a signal input from the control unit 101 via an input port 319 is connected between Z1 and the control unit 101 through an inductor L2. By turning on a switch 321, the oscillation adjustment unit 106d is connected to the RTD oscillator 104 and can adjust the impedance of the resonant conductor 109. Furthermore, by using a variable capacitance such as a varactor diode for Cv or a variable impedance circuit using a transistor as shown in FIG. 5, it is possible to improve the controllability from the control unit 101.

[0030] In addition to the illustrated configuration example, an impedance adjustment circuit can be provided that changes the influence of reflected waves by switching the microstrip line. Also, circuits that can change the impedance or phase of the connected line, such as a reflective phase adjustment circuit using a 90° hybrid circuit and variable capacitance, can be provided. These circuits can reduce loss during oscillation of the RTD oscillator 104 and increase oscillation efficiency by adjusting the impedance of the resonant conductor 109 to match the frequency of the synchronization signal from the reference oscillator 102. Furthermore, a circuit can be configured that adjusts the oscillation signal of the RTD oscillator 104 using the oscillation adjustment unit 106d, such as by adjusting the oscillation intensity or changing the radiation direction by increasing loss. Furthermore, information such as frequency and phase changes and transmission delays of the signal output from the reference oscillator 102 can be added to the signal at the input port 319. Adjustments can also be made, such as feedback to the control parameters of the variable impedance circuit 320, in response to changes in the synchronization signal that synchronizes the RTD oscillator 104.

[0031] Next, the control in the control unit 101 will be described. The control unit 101 performs control by transmitting a control signal required for the oscillation adjustment unit 106 to perform adjustment. 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 is configured to oscillate at a desired frequency using a common PLL (Phase Locked Loop) circuit based on an oscillation signal input from a lower frequency source, such as a high-precision oscillation source using a crystal oscillator. Upon setting the reference oscillator 102 and upon stabilizing the oscillation of the reference oscillator 102, the control unit 101 sends a control signal to the oscillation adjustment unit. At this time, the control unit 101 can determine the adjustment value of the oscillation adjustment unit 106 to be provided as a control signal based on the frequency oscillated and 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 that the reference oscillator 102 outputs 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, the control unit 101 adjusts the phase by subtracting the phase change, thereby correcting the phase delay from the reference oscillator 102 to the RTD oscillator 104. 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 is possible to 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 according to the fluctuations is possible. Furthermore, although the locking range increases depending on the signal strength of injection locking, a phenomenon is observed in which the phase varies within a range of −90° to +90°. For this reason, it is conceivable to change the speed and amount of bias adjustment according to the signal strength from the reference oscillator 102.

[0033] Alternatively, when the oscillation adjustment unit 106c described in FIG. 4 is used, a circuit can be configured in which the oscillation adjustment unit 106c receives a control signal from the control unit 101 and performs control based on 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 adjustment unit 106c. This allows the oscillation adjustment unit 106c to be controlled in accordance with the operation of the reference oscillator 102. In either case, the oscillation adjustment unit 106c can adjust the oscillation signal for the RTD oscillator 104 in accordance with the operation of the reference oscillator 102, based on instructions from the signal from the control unit 101. The control content 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 illustrative purposes only 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, a transmission path 331 for the reference signal, which is output by the reference oscillator 102 and synchronizes the RTD oscillator 104, is shown. 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 antenna 107 is connected to the RTD oscillator 104 via a 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 achieve impedance matching 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 clamped to GND. On the other hand, at the output end of the RTD oscillator 104, which is connected to the antenna, the frequency is λ / 4. 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 can be appropriately arranged by adjusting the scale to match the frequency of the terahertz band, 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 signal of the RTD oscillator 104 can be adjusted using the oscillation adjustment units (106, 106b, 106c, 106d) described in this embodiment. As a result, the frequency, phase, radiation intensity, beam shape, and other parameters 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, and 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 for emitting 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 modulated terahertz waves 113 from an antenna 107. In addition to the block connections of this embodiment, a power amplifier (PA) for amplifying the radiated terahertz waves, a filter for removing unwanted waves, and the like may also be appropriately arranged.

[0040] The injection locking unit 110 will now be described. The injection locking unit 110 generates an injection locking signal (second locking signal) to be injected to synchronize the RTD oscillator 104 based on a reference signal (first locking signal) output from the reference oscillator 102. The injection locking unit in this embodiment has a phase shifter that changes the phase of the reference signal (first locking signal). FIG. 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 an input 341 and an output 342. Variable capacitances are disposed at the connection between the λ / 4 line B (343) and the λ / 4 line C (344) and the connection between the λ / 4 line C (344) and the λ / 4 line D (345), making this a reflective phase shifter.

[0041] 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-type 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 achieved by switching to a high-pass filter (HPF) can also be appropriately selected.

[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 allows adjustments to be made to each individual RTD oscillator 104, taking into account factors such as delay time 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, reflected waves can be suppressed, helping to ensure stable oscillation of the RTD oscillator 104. Furthermore, the injection locking unit can perform feedback by adjusting the bias of the oscillation adjustment unit 106 by injecting the adjusted synchronization signal (second synchronization signal) into the oscillation adjustment unit 106. This enables the oscillation adjustment unit 106 to control itself in accordance with the operation of the reference oscillator 102 and the operation of the injection locking signal (second locking signal) generated based on the reference signal (first locking 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 control signal provided to the oscillation adjustment unit 106 is adjusted based on control information held by the control unit 101 that controls the injection locking unit 110, so that the oscillation adjustment unit 106 can perform control in accordance with the operation of the injection locking signal. 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 between the RTD oscillator 104 and the oscillation adjustment unit 106. The branch circuit can be a T-branch circuit typically used in microwave and other high-frequency circuits, a power divider, a hybrid coupler, or a rat-race circuit. 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 locking 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 locking 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 locking 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 locking 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 party (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 upconverted before input, and the frequency, band, and modulation method are appropriately selected depending on the communication system. The frequency output by the RTD oscillator 104 also varies depending on the channel secured for communication by this device. While this embodiment is described based on modulation of the RTD oscillator, it is also possible to modulate the baseband signal by inputting it from the high-frequency signal side using a bias tee or the like as a bias voltage from the bias unit. A 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 the present invention is not limited to the above description.

[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 differ 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 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. While this is an embodiment with multiple antennas, the division of the internal blocks of the semiconductor device 100 is not limited to this.

[0049] The configuration in Figure 9 also includes some common parts, even in configurations consisting of 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 are generated from the same oscillator, but it is also possible to arrange multiple reference oscillators with their frequencies and phases adjusted to be aligned. The baseband signal 112 is also common. To simultaneously radiate the same data from multiple antennas, one baseband 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 provided separately for each RTD oscillator (104a, 104b), but they can also be integrated into a single shared module. Sharing these blocks simplifies the wiring of the reference signal from the reference oscillator 102. In the case of a shared block, a Butler matrix circuit or the like can be used in the injection locking unit to distribute the phase from the reference oscillator 102 to multiple RTD oscillators 104 with a phase difference. Furthermore, it becomes possible to check the phase shift between the 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 addition to the same control as in the conventional embodiment in which the oscillation adjustment units (106a, 106b) individually control each other, the bias voltage coming from the bias unit 105 can be adjusted as a common adjustment in accordance with the mutual operating states of the RTD oscillators (104a, 104b).

[0051] By matching the phase between the array antennas, the oscillation adjustment units (106a, 106b) can generate a terahertz wave beam with directivity in the vertically upward direction (right side of 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 the phase of antenna 107b, the emitted beam can be tilted toward antenna 107a (upper right side of 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 adjustment units (106a, 106b). The relationship between the phase difference between the antennas and the scan angle during beamforming is expressed as sin θ = (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 pitch of the array antenna. 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 embodiments, this embodiment includes four antennas (107a, 107b, 107c, and 107d). The four antennas are arranged in a matrix, vertically and horizontally, forming a 2-row, 2-column array. The terahertz transmitter radiates a beam in the vertical direction based on the two-dimensional plane of this antenna array (defined in the same direction as the paper surface). The number of arrays shown here is merely 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 adjustment units (106c, 106d) are provided. The oscillation adjustment unit 106c is configured to adjust one vertical row of RTD oscillators (104a, 104b), and the other oscillation adjustment unit 106d is configured to adjust another vertical row of RTD oscillators (104c, 104d). When the RTD oscillators are 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 adjustment unit 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. Furthermore, 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 phases of the oscillation adjustment units 106c and 106d. By combining these, the direction of the beam emerging from the plane can be freely set.

[0055] Furthermore, since there is no need to arrange individual circuits corresponding to all the RTD oscillators (104a, 104b, 104c, and 104d), wiring can be shared, allowing for more efficient circuit layout. When the wavelength of terahertz waves is 0.5 GHz, the wavelength λ is 0.6 mm. Therefore, the layout constraints imposed when arranging the antennas (107a, 107b, 107c, and 107d) at a pitch of λ / 2 or less, as well as increased loss due to the circuit structure around the antennas, can easily lead to reduced efficiency. Therefore, by dividing the antennas into multiple groups and performing common control within each group, it is possible to simplify the circuit and wiring. It is also possible to divide the groups into vertical and horizontal rows and wire them as shown in Figure 9, or to provide a common injection locking unit and oscillation adjustment unit for each horizontal row. Furthermore, an array antenna with N rows and N columns can be controlled as an array antenna group with M rows and M columns (M < N, M and N are natural numbers). This allows the number of oscillation adjustment units and injection locking units to be N × N or less. As a specific example, for a 4x4 array antenna, four groups of two rows and two columns can be provided, and these can be controlled individually.

[0056] By using the circuit of this embodiment, it is possible to realize control by the oscillation adjustment unit while appropriately performing injection locking on the RTD oscillators (104a, 104b, 104c, 104d) even for a two-dimensional array antenna, thereby suppressing losses due to poor layout.

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

[0058] 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. Disassembling the RTD 108 reveals that it is composed of 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. A signal from the reference oscillator 102 is not shown, but 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 for protecting this semiconductor device.

[0059] By integrating the RTD oscillator 114 with an 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 substrate are major causes of output reduction. Therefore, the device of this embodiment not only becomes a compact and small device, but also realizes a form that can radiate efficiently 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 has been described using a transmitter in a wireless communication device as an example, the application is not limited thereto and may also be, for example, a radar device. In the case of an 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 as 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] In addition, 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 system or a push-pull system. 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 RTD oscillator structure has been described using a laminated structure, this is not limiting. That is, the above discussion can also be applied to oscillator devices that do not use a laminated structure. Furthermore, the following combinations of RTD materials may be used: GaAs / AlGaAs and GaAs / AlAs, InGaAs / GaAs / AlAs formed on a GaAs substrate; InGaAs / InAlAs, InGaAs / AlAs, InGaAs / AlGaAsSb formed on an InP substrate; InAs / AlAsSb and InAs / AlSb formed on an InAs substrate; and SiGe / SiGe formed on a Si substrate. The above-described structures and materials may be selected appropriately depending on the desired frequency, etc.

[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 below. The following description will be made with reference to FIG. 12( a). The terahertz camera system 1100 includes a transmitter 1101 that emits terahertz waves TW and a receiver 1102 that detects the terahertz waves TW. The terahertz camera system 1100 further includes a controller 1103 that controls the operation of the transmitter 1101 and the receiver 1102 based on an external signal, and processes or externally outputs an image based on the detected terahertz waves. The semiconductor device according to each embodiment may be the transmitter 1101 or the receiver 1102. The terahertz waves emitted from the transmitter 1101 are reflected by an object 1105 and detected by the receiver 1102. A camera system including such a transmitter 1101 and receiver 1102 may also be called an active reflection imaging camera system. Also, a transmission imaging system can be considered in which the transmitter 1101 and receiver 1102 are arranged opposite 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, the detection sensitivity of the camera system can be improved, and high-quality images can be obtained.

[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 below. The description will be made below with reference to FIG. 12(b). The device can be used as a component of the communication system. Possible 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, and 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 baseband signals, 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-capacity data 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, and improves ranging accuracy, all 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 present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0072] This application claims priority based on Japanese Patent Application No. 2024-043186, filed March 19, 2024, the entire contents of which are incorporated herein by reference.

[0073] 100 Semiconductor device 101 Control unit 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. The semiconductor device according to claim 1, wherein the control unit generates the control signal to the oscillation adjustment unit in accordance with the operation of the reference oscillator.

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

4. A semiconductor device according to any one of claims 1 to 3, characterized in that the oscillation adjustment unit is controlled based on a transmission delay or phase change relative to the output of the reference oscillator using a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator.

5. A semiconductor device according to any one of claims 1 to 4, further comprising a bias section for applying 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. A semiconductor device according to any one of claims 1 to 5, wherein the oscillation adjustment section checks a reflected signal reflected from the RTD oscillator against a synchronization signal that synchronizes the RTD oscillator.

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

8. A semiconductor device according to any one of claims 1 to 7, characterized in that the control unit inputs a control signal to the oscillation adjustment unit that corresponds to a set value of a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator.

9. A semiconductor device as described in any one of claims 1 to 8, characterized in that the control unit inputs a control signal to the oscillation adjustment unit that does not correspond to the set value of a synchronization signal that synchronizes the RTD oscillator output from the reference oscillator, and the oscillation adjustment unit performs control in accordance with the synchronization signal.

10. A semiconductor device according to any one of claims 1 to 9, further comprising an injection locking unit, which 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 accordance with the operation of the injection locking unit.

12. A semiconductor device according to claim 10 or 11, characterized in that the injection locking unit adjusts the delay time, phase or intensity of the first synchronization signal, and injects the adjusted second synchronization signal into the RTD oscillator.

13. A semiconductor device according to any one of claims 10 to 12, characterized in that the injection locking unit outputs a signal corresponding to the delay time, phase or intensity of the signal output to the RTD oscillator to the oscillation adjustment unit.

14. A semiconductor device as described in any one of claims 10 to 13, characterized in that the control unit provides the oscillation adjustment unit with a control signal that does not correspond to the set value of a synchronization signal that synchronizes the reference oscillator or the RTD oscillator output from the injection synchronization unit, and the oscillation adjustment unit performs control in accordance with the synchronization signal.

15. A semiconductor device according to any one of claims 1 to 14, characterized in that the oscillation adjustment section has impedance adjustment means electrically connected to the RTD oscillator for adjusting the impedance of the RTD oscillator.

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

17. The semiconductor device according to any one of claims 1 to 16, wherein the RTD oscillator has a configuration in which one or more RTDs are electrically connected to a conductor for resonance.

18. A semiconductor device according to any one of claims 1 to 17, wherein the RTD oscillator is electrically connected to one or more antennas, the antennas emitting or detecting electromagnetic waves comprising the oscillating signal.

19. 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. A semiconductor device according to any one of claims 1 to 19, further comprising a modulation / demodulation unit that modulates or demodulates the oscillation signal of the RTD oscillator, the modulation / demodulation unit being electrically connected to the RTD oscillator.

21. The semiconductor device according to claim 20, wherein said oscillation adjusting section is adjusted in accordance with the strength or bandwidth of a baseband signal input to said modulation / demodulation section.

22. A semiconductor device as described in claim 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 contained in the reference signal to approach each other.

23. A semiconductor device according to any one of claims 1 to 22, characterized in that the oscillation adjustment section changes the phase of the signal that resonates in the RTD oscillator by adjusting the bias.

24. A semiconductor device according to any one of claims 1 to 23, characterized in that the oscillation adjustment section changes the phase or intensity of the signal resonating in the RTD oscillator by adjusting the impedance of the RTD oscillator.

25. A semiconductor device according to any one of claims 1 to 24, characterized in that 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. A semiconductor device as described in any one of claims 1 to 25, characterized in that, while the frequency is changed by the reference oscillator, the oscillation adjustment unit adjusts the bias potential to synchronize with the harmonic component of the frequency output from the reference oscillator and applies a bias to the RTD oscillator.

27. A semiconductor device according to any one of claims 1 to 26, characterized in that the bias potential of the RTD oscillator is set in the negative resistance region of the RTD.

28. The semiconductor device according to any one of claims 18 to 27, characterized in that it comprises a plurality of combinations of the RTD oscillator and the antenna connected to the RTD oscillator.

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. A semiconductor device according to any one of claims 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.

31. A semiconductor device according to any one of claims 1 to 30, wherein the signal strength output from the reference oscillator is greater than the output from the RTD oscillator.

32. A semiconductor device according to any one of claims 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 x M or less.

33. A semiconductor device according to any one of claims 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.

34. A semiconductor device according to any one of claims 1 to 33, 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 performs beamforming by changing the phase difference between the oscillation signals of one or more adjacent RTD oscillators.

35. A semiconductor device according to any one of claims 1 to 34, characterized in that it comprises a common reference oscillator for a plurality of said RTD oscillators.

36. A semiconductor device according to any one of claims 1 to 35, characterized in that it comprises a plurality of reference oscillators for the plurality of RTD oscillators, and at least two of the reference oscillators have the same frequency and phase.

37. A semiconductor device according to any one of claims 18 to 36, characterized in that the antenna is a square patch antenna.

38. A semiconductor device according to any one of claims 18 to 37, characterized in that the electromagnetic waves are electromagnetic waves having a frequency in the terahertz band.

39. A semiconductor device according to any one of claims 1 to 38, wherein the RTD oscillator is a microstripline resonator.

40. A communication device comprising: a semiconductor device according to any one of claims 1 to 39; a transmitter for emitting electromagnetic waves; and a receiver for detecting electromagnetic waves.

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

42. A radar device comprising: a semiconductor device according to any one of claims 1 to 39; a transmitter for emitting electromagnetic waves; a receiver for detecting reflected waves of the radiated electromagnetic waves; and a radar device for measuring distance from the radiated waves and the reflected waves.

Images