An implementation device and method of a controllable non-reciprocal microwave circuit

Abstract

The application discloses an implementation device and method of a controllable nonreciprocal circuit, and the device comprises a vector network analyzer, a left coupling capacitor, a right coupling capacitor and a nonlinear LC resonant cavity, wherein the resonant frequency of the nonlinear LC resonant cavity is jointly regulated by a direct current bias voltage loaded on a varactor diode and a microwave signal. The application utilizes the difference in coupling efficiency of microwave energy coupled into the nonlinear LC resonant cavity when the microwave signal is transmitted forward and reversely, and utilizes the regulation of the direct current bias voltage on the nonlinear interaction between the microwave signal and the LC resonant cavity mode in the nonlinear LC resonant cavity, so that the nonlinear LC resonant cavity can be in different bistable states when the microwave signal is transmitted forward and reversely, and thus the controllable nonreciprocal transmission with high contrast can be realized for the microwave signal in a larger working bandwidth.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave circuits, and in particular to an implementation device and method of a controllable nonreciprocal microwave circuit. BACKGROUND

[0002] Nonreciprocal microwave circuits are important microwave functional devices, whose purpose is to realize nonreciprocal transmission of microwaves, i.e. to allow microwave transmission only in one direction, while microwave transmission in the opposite direction is suppressed. This is very similar to the unidirectional transmission effect of an electronic diode with a p-n junction, and thus has broad application prospects in the field of integrated circuits.

[0003] Breaking the time-reversal symmetry of microwave transmission is the key to realizing nonreciprocal microwave circuits. At present, a variety of mechanisms and methods for realizing nonreciprocal microwave transmission have been proposed. For example, in active devices, a conventional nonreciprocal structure composed of P-type and N-type semiconductor materials has typical geometric asymmetry, and direct current signals can only flow along the direction of the built-in electric field in the PN junction and cannot flow in the opposite direction, thereby exhibiting nonreciprocal characteristics for the amplitude of the direct current signal. For passive devices, nonreciprocal devices made of non-metallic magnetic materials such as ferrite achieve the isolation and nonreciprocal transmission of electromagnetic signals based on the Faraday rotation effect. However, the preparation process of ferromagnetic materials is difficult to be compatible with the traditional silicon-based integrated circuit process, and an external magnetic field bias is needed to achieve nonreciprocity. At present, most nonreciprocal devices appear in the system as discrete components, making it still very difficult to realize integrated and miniaturized nonreciprocal devices in engineering applications, and the external magnetic field can easily affect other modules around the system.

[0004] Therefore, people have begun to explore how to realize nonreciprocal circuits without a magnetic field. The methods used can be roughly divided into the following categories. One of the methods for producing unidirectional devices is to modulate the time and space of a closed structure, such as a ring resonator. The signal in the ring resonator can effectively carry angular momentum, and only needs to transfer the angular momentum to the resonator to improve the degeneracy of the mode rotating in the opposite direction, resulting in nonreciprocity. The second method for generating nonreciprocity through time modulation is based on a unique mixing characteristic, which has a relatively weak nonreciprocal response. Specifically, a signal obtains a phase through an up-conversion mixer, which is opposite to the phase obtained through a down-conversion mixer. Based on this property, by combining two mixers and a transmission line (or other elements that can realize delay function) together, and modulating the mixers with signals of the same frequency and opposite phase in time, a phase shifter with nonreciprocity can be realized, so that waves propagating in opposite directions can obtain different phase shifts. This phase shifter with unidirectionality can be used to construct other more advanced devices, such as isolators and circulators.

[0005] In the above described method, the non-reciprocity is derived from the control of the signal phase, which results in the limitation of the bandwidth of the signal and the generation of a large number of intermodulation components and harmonics. There is also a method of switching the signal path to obtain a one-way element with ultra-wideband. However, in practical applications, the phase noise of the switch limits the bandwidth and isolation that can be achieved by this structure. Therefore, it is very important to find a non-reciprocal microwave transmission method without magnetism and without relying on phase modulation with larger operating bandwidth and transmission contrast. SUMMARY

[0006] The main purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, and to provide an implementation device and method of controllable non-reciprocal microwave circuit. The present application can simultaneously realize higher transmission contrast and larger operating bandwidth through a nonlinear LC resonant cavity.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] In the first aspect, the present application provides an implementation device of controllable non-reciprocal microwave circuit, which comprises a vector network analyzer, a left coupling capacitor C1, a right coupling capacitor C2 and a nonlinear LC resonant cavity, wherein the nonlinear LC resonant cavity is connected between the left coupling capacitor C1 and the right coupling capacitor C2; the left coupling capacitor C1 and the right coupling capacitor C2 are not equal in size.

[0009] The nonlinear LC resonant cavity comprises a first varactor, a second varactor, a first DC bias power supply, a second DC bias power supply, a first high-value resistor, a second high-value resistor, a first fixed-value capacitor, a second fixed-value capacitor and an inductor; the first varactor and the second varactor are connected in antiparallel, the first fixed-value capacitor is connected in series with the second varactor, and the second fixed-value capacitor is connected in series with the first varactor; the first high-value resistor is connected between the first fixed-value capacitor and the second varactor, and the second high-value resistor is connected between the second fixed-value capacitor and the first varactor; the first DC bias power supply is connected in series with the second high-value resistor, and the second DC bias power supply is connected in series with the first high-value resistor; one end of the inductor is connected between the first fixed-value capacitor and the first varactor, and the other end of the inductor is connected between the second fixed-value capacitor and the second varactor.

[0010] As a preferred technical scheme, the output port of the vector network analyzer is used to emit a radio frequency signal source for providing a wavelength and power adjustable microwave signal; and the input port of the vector network analyzer is used to receive the output signal of the non-reciprocal microwave circuit system.

[0011] As a preferred technical scheme, when the microwave signal is transmitted forwardly, the left coupling capacitor C1 and the right coupling capacitor C2 control the coupling strength between the microwave signal input end and the nonlinear LC resonant cavity and the coupling strength between the microwave signal output end and the nonlinear LC resonant cavity respectively; when the microwave signal is transmitted reversely, the right coupling capacitor C2 and the left coupling capacitor C1 control the coupling strength between the microwave signal input end and the nonlinear LC resonant cavity and the coupling strength between the microwave signal output end and the nonlinear LC resonant cavity respectively.

[0012] As a preferred technical scheme, the first varactor diode and the second varactor diode are the same; the capacitance size of the first varactor diode is controlled by the first direct current bias power supply, and the capacitance size of the second varactor diode is controlled by the second direct current bias power supply.

[0013] As a preferred technical scheme, the first high-value resistor and the second high-value resistor are used to prevent the microwave signal from flowing into the ground through the first direct current bias power supply and the second direct current bias power supply, thereby causing loss.

[0014] In a second aspect, the application provides a control method of an implementation device of a controllable non-reciprocal microwave circuit, comprising the following steps:

[0015] Step one: set the output voltage of the first direct current bias power supply and the second direct current bias power supply to 0, and use a vector network analyzer to detect the transmission spectrum of the LC resonant cavity in a linear case at very low microwave signal power; adjust the frequency f of the continuous wave microwave signal emitted by the output port of the vector network analyzer, so that the frequency f is slightly lower than the resonant frequency f0 of the LC resonant cavity in the linear case, and satisfies (f0-f) / γ>3, wherein γ is half of the full width at half maximum of the transmission spectrum of the LC resonant cavity in the linear case;

[0016] Step two: set the values of the left coupling capacitor C1 and the right coupling capacitor C2 to be unequal;

[0017] Step three: when the continuous wave microwave signal with the frequency satisfying the condition of step one is incident from the left or the right photonic crystal waveguide, adjust the power of the continuous wave microwave signal, so that the power is equal to any value between 0.1 W and 0.5 W; when the input microwave signal power is constant, start from 0 to synchronously increase the voltages of the two direct current bias power supplies, and detect the direct current bias voltage values required for the nonlinear LC resonant cavity to reach the high transmission state of bistability when the microwave signal is transmitted forwardly and reversely respectively.

[0018] As a preferred technical scheme, in step one, the very low microwave signal power refers to a power less than 0.002 W.

[0019] As a preferred technical scheme, in step two, the ratio of the left coupling capacitor C1 to the right coupling capacitor C2 is greater than 1.2 and less than 1.5.

[0020] As a preferred technical solution, in step three, when the forward transmission and reverse cut-off of the microwave signal needs to be realized, the following steps are further included:

[0021] The direct current bias voltage value required for achieving the high transmission state when the microwave signal is transmitted forward is detected, and it is ensured that when the direct current bias voltage takes these values, the reverse transmission of the microwave signal is in the low transmission state;

[0022] By setting the direct current bias voltage to any one of these voltage values, the nonlinear interaction between the microwave signal in the nonlinear LC resonant cavity and the resonant mode of the nonlinear LC resonant cavity is regulated by the direct current bias voltage, so that under the nonlinear effect, when the microwave signal is transmitted forward, the resonant mode wavelength of the nonlinear LC resonant cavity is red-shifted and exactly equal to the wavelength of the incident microwave signal, thereby matching the resonance and realizing the high transmission of the microwave signal, i.e., the forward transmission.

[0023] When the microwave signal is transmitted reversely, the energy in the nonlinear LC resonant cavity becomes very weak under the regulation of the direct current bias voltage, so that the red-shift amount of the resonant wavelength of the nonlinear LC resonant cavity is very small, and it cannot match the resonance with the wavelength of the incident microwave signal, thereby realizing the low transmission of the microwave signal, i.e., the reverse transmission is cut off.

[0024] As a preferred technical solution, in step three, when the forward transmission and reverse cut-off of the microwave signal needs to be realized, the following steps are further included:

[0025] The direct current bias voltage value required for achieving the high transmission state when the microwave signal is transmitted forward is detected, and it is ensured that when the direct current bias voltage takes these values, the reverse transmission of the microwave signal is in the low transmission state;

[0026] By setting the direct current bias voltage to any one of these voltage values, the nonlinear interaction between the microwave signal in the nonlinear LC resonant cavity and the resonant mode of the nonlinear LC resonant cavity is regulated by the direct current bias voltage, so that under the nonlinear effect, when the microwave signal is transmitted forward, the resonant mode wavelength of the nonlinear LC resonant cavity is red-shifted and exactly equal to the wavelength of the incident microwave signal, thereby matching the resonance and realizing the high transmission of the microwave signal, i.e., the forward transmission.

[0027] When the microwave signal is transmitted reversely, the energy in the nonlinear LC resonant cavity becomes very weak under the regulation of the direct current bias voltage, so that the red-shift amount of the resonant wavelength of the nonlinear LC resonant cavity is very small, and it cannot match the resonance with the wavelength of the incident microwave signal, thereby realizing the low transmission of the microwave signal, i.e., the reverse transmission is cut off.

[0028] The principle of the present application is as follows: when the microwave signal is transmitted forwardly, the microwave signal is coupled into the nonlinear LC resonant cavity via the left coupling capacitor C1. When the microwave signal is transmitted reversely, the microwave signal is coupled into the nonlinear LC resonant cavity via the right coupling capacitor C2. In the nonreciprocal microwave circuit involved in the present application, the left coupling capacitor C1 and the right coupling capacitor C2 are set to be unequal, so that the coupling structure of the nonreciprocal microwave circuit has asymmetry. The greater the value of the capacitor, the smaller the hindering attenuation of the signal, and the better the effect of coupling the signal into the nonlinear LC resonant cavity. The difference between the left coupling capacitor C1 and the right coupling capacitor C2 will result in that the strength of the nonlinear interaction in the nonlinear LC resonant cavity is related to the incident direction of the microwave signal, that is, the required nonlinear bistable jump power will be different when the incident direction of the microwave signal is different. The bistable jump power refers to the power of the incident microwave signal required for the transmission rate of the system to jump from the low transmission state to the high transmission state. This is because the left coupling capacitor C1 is greater than the right coupling capacitor C2, so the efficiency of coupling the microwave signal into the nonlinear LC resonant cavity when the microwave signal is transmitted forwardly is greater than the efficiency of coupling the microwave signal into the nonlinear LC resonant cavity when the microwave signal is transmitted reversely. This will result in that the required nonlinear bistable jump power when the microwave signal is transmitted forwardly is less than the required nonlinear bistable jump power when the microwave signal is transmitted reversely, so that the bistable states in the two opposite transmission directions are staggered with each other. In the staggered bistable region, the bistable state when the microwave signal is transmitted forwardly and the bistable state when the microwave signal is transmitted reversely can be located in the high transmission state or the low transmission state, which depends on the size of the direct current bias voltage loaded on the varactor diode. If a suitable direct current bias voltage is selected, so that the bistable state when the microwave signal is transmitted forwardly is located in the high transmission state, and the bistable state when the microwave signal is transmitted reversely is located in the low transmission state, the forward conduction and the reverse cut-off of the microwave signal can be realized; on the contrary, if a suitable direct current bias voltage is selected, so that the bistable state when the microwave signal is transmitted reversely is located in the high transmission state, and the bistable state when the microwave signal is transmitted forwardly is located in the low transmission state, the reverse conduction and the forward cut-off of the microwave signal can be realized. In this way, controllable nonreciprocal transmission of the microwave circuit can be realized.

[0029] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0030] (1) The existing non-reciprocal transmission of microwave signals based on Faraday rotation effect needs to use non-metallic magnetic materials such as ferrite to construct non-reciprocal devices. However, the preparation process of ferromagnetic materials is difficult to be compatible with the silicon-based CMOS integrated circuit process, and an external magnetic field bias is needed to realize non-reciprocity, which makes it difficult to realize integrated and miniaturized non-reciprocal devices in engineering applications, and the external magnetic field is easy to affect other modules around the system. The present application does not need to use external magnetic field and Faraday rotation effect, but through the regulation of direct current bias voltage on the nonlinear LC resonant cavity to realize controllable non-reciprocal microwave circuit transmission, and it is fully compatible with the current silicon-based CMOS circuit process, and easy to realize the integration of the device.

[0031] (2) The existing non-magnetic non-reciprocal microwave circuit, whether based on time and space modulation of ring resonator or based on one-way phase shift of signal mixing frequency phase modulation mixer, its non-reciprocity comes from the control of microwave signal phase, which may produce a large number of intermodulation components and harmonics, and lead to the limitation of microwave signal bandwidth. The method used in the present application does not need to control the phase of microwave signal, but uses bias voltage to regulate the bistability of nonlinear LC resonant cavity, so that wideband and low-noise non-reciprocal microwave transmission can be realized.

[0032] (3) The existing microwave circuit non-reciprocal transmission with reversible conduction direction can only realize the reverse of conduction direction for different wave bands of microwave signals, but cannot realize the controllable reverse of conduction direction for the same wavelength of microwave signals. The present application realizes the controllable reverse of conduction direction for the same wavelength of microwave signals by the design of asymmetric coupling structure of nonlinear LC resonant cavity and the regulation of direct current bias voltage loaded on varactor diode to the bistability (high transmission state or low transmission state) of nonlinear LC resonant cavity, so that the bistability in the microcavity is significantly different when the microwave signal is transmitted forward and backward, which is very important for integrated circuit signal processing. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating labor.

[0034] Figure 1 It is a schematic diagram of the composition of a non-reciprocal microwave circuit controllable one-way transmission device for the present application's embodiment of microwave signal forward incidence (from left to right).

[0035] Figure 2Schematic diagram of a non-reciprocal microwave circuit controllable unidirectional transmission device when a microwave signal is incident in the reverse direction (from right to left) according to an embodiment of the present invention.

[0036] Figure 3 1 is a graph showing the relationship between the forward transmittance and the reverse transmittance as a function of the wave signal power according to an embodiment of the present invention.

[0037] Figure 4 FIG. 4 is a graph showing the relationship between the forward transmittance and the reverse transmittance as a function of the bias voltage according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0039] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0040] Example 1

[0041] like Figure 1 As shown, a device for implementing a controllable non-reciprocal microwave circuit in this embodiment includes a vector network analyzer, a left coupling capacitor (C1) 2, a right coupling capacitor (C2) 4, and a nonlinear LC resonant cavity 3. The output port (Port 1) 1 of the vector network analyzer is connected to the left coupling capacitor C1, the input port (Port 2) 5 of the vector network analyzer is connected to the right capacitor C2, and the nonlinear LC resonant cavity 3 is connected between the left coupling capacitor C1 and the right coupling capacitor C2.

[0042] Furthermore, the output port 1 of the vector network analyzer is used to provide a low-power continuous wave microwave signal, whose frequency is continuously adjustable from 200 MHz to 500 MHz with a tuning accuracy of 1 MHz; the input port 5 of the vector network analyzer is used to receive the output signal of the non-reciprocal microwave circuit system.

[0043] Further, the left coupling capacitor C1 and the right coupling capacitor C2 are not equal in size, and the ratio of the left coupling capacitor C1 and the right coupling capacitor C2 is greater than 1.2 and less than 1.5. For example, the capacitance value of the left coupling capacitor 2 is 2.6 pF, and the capacitance value of the right coupling capacitor 4 is 2.0 pF.

[0044] Further, the nonlinear LC resonant cavity 3 of the embodiment includes a first varactor diode (VD1) 6, a second varactor diode (VD2) 7, a first DC bias power supply (V1) 8, a second DC bias power supply (V2) 9, a first high-value resistor (R1) 10, a second high-value resistor (R2) 11, a first fixed-value capacitor (C3) 12, a second fixed-value capacitor (C4) 13, and an inductor (L) 14. The first varactor diode 6 and the second varactor diode 7 are both MV2103, and are connected in anti-parallel, with their capacitances controlled by the first DC bias power supply 8 and the second DC bias power supply 9, respectively. The first high-value resistor 10 and the second high-value resistor 11 both have a resistance value of 400 KΩ, and are connected to the first DC bias power supply 8 and the second DC bias power supply 9, respectively, to prevent microwave signals from flowing into the ground through the DC bias power supply, causing loss. The first high-value resistor 10 is connected between the first fixed-value capacitor 12 and the second varactor diode 7, and the second high-value resistor 11 is connected between the second fixed-value capacitor 13 and the first varactor diode 6. The first fixed-value capacitor 12 and the second fixed-value capacitor 13 both have a capacitance value of 45 pF, and are connected in series with the first varactor diode 6 and the second varactor diode 7, respectively. The inductor 14 is connected between the first fixed-value capacitor 12 and the first varactor diode 6 at one end, and between the second fixed-value capacitor 13 and the second varactor diode 7 at the other end, and has a value of 3.3 nH.

[0045] In another embodiment of the present application, a method for realizing forward high transmission and reverse low transmission of microwave transmission of a controllable non-reciprocal microwave circuit is provided, including the following steps:

[0046] First step: set the bias voltage of the first DC bias power supply 8 and the second DC bias power supply 9 to 0, at which time the resonant frequency of the LC resonant cavity measured by the vector network analyzer is f0=358 MHz, and the half of the full width at half maximum of the cavity mode is γ=1.5 MHz. Then, set the frequency of the continuous wave microwave signal transmitted by the output port 1 of the vector network analyzer to f=352 MHz, so that (f0-f) / γ=4, to satisfy the condition of (f0-f) / γ>3;

[0047] Step 2: Set the bias voltages of both the first and second DC bias power supplies 8 and 9 to 3V. Gradually increase the power of the continuous wave microwave signal emitted from the output port 1 of the vector network analyzer from 0.01W to 0.65W. The forward-propagating microwave signal is coupled into the nonlinear LC resonant cavity 3 via the left-hand coupling capacitor 2 and loaded onto the first and second varactor diodes 6 and 7. Under the combined effects of the microwave signal and the first and second DC bias power supplies 8 and 9, the resonant frequency of the nonlinear LC resonant cavity undergoes a redshift. When the redshifted resonant frequency equals the frequency of the microwave signal, the nonlinear LC resonant cavity transitions from its previous low-transmittance state to a high-transmittance state. The transmitted microwave signal passes from the nonlinear LC resonant cavity through the right-hand coupling capacitor 4 and into the input port 5 of the vector network analyzer. The relationship between the forward transmittance and microwave signal power is measured.

[0048] Step 3: To measure the relationship between reverse transmittance and microwave signal power, just swap the output port 1 and input port 5 of the vector network analyzer (such as Figure 2 As shown in the figure, the microwave signal emitted from the output port 1 of the vector network analyzer is transmitted in the reverse direction (from right to left). The remaining methods and steps are the same as the first and second steps above. The relationship between the forward transmittance and reverse transmittance measured by the vector network analyzer and the wave signal power is shown in the figure below. Figure 3 As shown in Figure 2, since the coupling capacitor C1 on the left is larger than the coupling capacitor C2 on the right, the nonlinear bistable jump power required for forward microwave signal transmission is smaller than the nonlinear bistable jump power required for reverse microwave signal transmission, causing the two bistable regions with opposite transmission directions to be staggered, as shown in Figure 2. Figure 3 shown.

[0049] Step 4: Figure 3 The staggered regions of the bistable state shown (corresponding to microwave signal powers ranging from 0.14W to 0.22W) achieve high forward transmittance and low reverse transmittance for microwave signal transmission at any microwave signal power level, creating a forward-conducting nonreciprocal microwave circuit. The maximum forward transmittance reaches -1.84dB, while the minimum reverse transmittance is -16.31dB, resulting in a forward-to-reverse transmission contrast ratio of 14.47dB.

[0050] Step 5: The power of the microwave signal emitted from the output port 1 of the vector network analyzer is set to 0.21W and remains unchanged. The bias voltages of the first DC bias power supply 8 and the second DC bias power supply 9 are gradually increased synchronously. The relationship between the forward transmittance and the reverse transmittance measured by the vector network analyzer and the bias voltage is shown as follows: Figure 4 As shown in parts (a) and (b) of the diagram. Due to the difference in the size of the coupling capacitors on the left and right, the relationship between the forward transmittance and the reverse transmittance as a function of the bias voltage is significantly different.Figure 4 For the marked regions II, IV, and V, for the same DC bias voltage, the forward transmittance is in a high transmittance state, while the reverse transmittance is in a low transmittance state. Therefore, when the DC bias voltage is in regions II, IV, and V, a forward-conducting non-reciprocal microwave circuit can be realized. For example, when the bias voltages of DC bias power supplies 8 and 9 are both set to 5.22V, the forward transmittance of microwave transmission is as high as -1.32dB, while the reverse transmittance is as low as -12.22dB, and the forward-reverse transmission contrast is 10.9dB. Since the adjustment range of the bias voltage that controls the resonant frequency of the nonlinear LC resonant cavity is large, the operating bandwidth of the non-reciprocal microwave circuit is also large (greater than 50MHz).

[0051] Example 2

[0052] This embodiment provides a device for implementing a controllable non-reciprocal microwave circuit. This device is designed to achieve controllable reversal of the conduction direction of the non-reciprocal microwave circuit (i.e., switching from forward conduction to reverse conduction in the non-reciprocal microwave circuit of Embodiment 1) at the same microwave signal wavelength. Except for the following features, all other features are the same as those of Embodiment 1.

[0053] The bias voltages of the first DC bias power supply 8 and the second DC bias power supply 9 are set as follows Figure 4 The corresponding DC bias voltage values ​​in Regions I and III represent the DC bias voltages required to achieve a high-transmittance state for reverse microwave transmission and a low-transmittance state for forward microwave transmission. This allows for a reverse-conducting nonreciprocal microwave circuit. For example, when the bias voltages of first and second DC bias power supplies 8 and 9 are both set to 5.08V, the reverse transmittance for microwave transmission reaches a high of -1.32dB, while the forward transmittance is as low as -12.22dB, resulting in a transmission contrast ratio of 10.9dB.

[0054] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A device for realizing a controllable non-reciprocal microwave circuit, characterized in that: The device comprises a vector network analyzer, a left coupling capacitor C1, a right coupling capacitor C2 and a nonlinear LC resonant cavity, wherein the nonlinear LC resonant cavity is connected between the left coupling capacitor C1 and the right coupling capacitor C2; the left coupling capacitor C1 and the right coupling capacitor C2 are unequal in size; The nonlinear LC resonant cavity includes a first varactor diode, a second varactor diode, a first DC bias power supply, a second DC bias power supply, a first high-value resistor, a second high-value resistor, a first fixed-value capacitor, a second fixed-value capacitor and an inductor; the first varactor diode and the second varactor diode are connected in reverse parallel, the first fixed-value capacitor and the second varactor diode are connected in series, and the second fixed-value capacitor and the first varactor diode are connected in series; the first high-value resistor is connected between the first fixed-value capacitor and the second varactor diode, and the second high-value resistor is connected between the second fixed-value capacitor and the first varactor diode; the first DC bias power supply is connected in series with the second high-value resistor, and the second DC bias power supply is connected in series with the first high-value resistor; one end of the inductor is connected between the first fixed-value capacitor and the first varactor diode, and the other end is connected between the second fixed-value capacitor and the second varactor diode.

2. The device for realizing a controllable non-reciprocal microwave circuit according to claim 1, characterized in that: The output port of the vector network analyzer is used to transmit a radio frequency signal source for providing a microwave signal with adjustable wavelength and power; the input port of the vector network analyzer is used to receive the output signal of the non-reciprocal microwave circuit system.

3. The device for realizing a controllable non-reciprocal microwave circuit according to claim 1, characterized in that: When the microwave signal is transmitted in the forward direction, the left coupling capacitor C1 and the right coupling capacitor C2 respectively control the coupling strength between the microwave signal input end and the nonlinear LC resonant cavity, and the coupling strength between the microwave signal output end and the nonlinear LC resonant cavity; when the microwave signal is transmitted in the reverse direction, the right coupling capacitor C2 and the left coupling capacitor C1 respectively control the coupling strength between the microwave signal input end and the nonlinear LC resonant cavity, and the coupling strength between the microwave signal output end and the nonlinear LC resonant cavity.

4. The device for realizing a controllable non-reciprocal microwave circuit according to claim 1, characterized in that: The first varactor diode and the second varactor diode are the same; the capacitance of the first varactor diode is controlled by a first DC bias power supply, and the capacitance of the second varactor diode is controlled by a second DC bias power supply.

5. The device for realizing a controllable non-reciprocal microwave circuit according to claim 1, characterized in that: The first high-value resistor and the second high-value resistor are used to prevent microwave signals from flowing into the ground through the first DC bias power supply and the second DC bias power supply, causing loss.

6. A control method for implementing a controllable non-reciprocal microwave circuit according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: Set the output voltages of the first and second DC bias power supplies to 0, and use a vector network analyzer to detect the transmission spectrum of the LC resonant cavity under a linear condition at a very low microwave signal power; adjust the frequency f of the continuous wave microwave signal emitted from the output port of the vector network analyzer so that the frequency f is slightly lower than the resonant frequency f0 of the LC resonant cavity under a linear condition, and satisfy (f0-f) / γ>3, where γ is half the full width at half maximum of the transmission spectrum of the LC resonant cavity under a linear condition; Step 2: Set the values ​​of the left coupling capacitor C1 and the right coupling capacitor C2 to be unequal; Step 3: When a continuous wave microwave signal with a frequency that meets the conditions of step 1 is incident from the left or right photonic crystal waveguide, the power of the continuous wave microwave signal is adjusted so that the power is equal to any value between 0.1 watts and 0.5 watts; when the input microwave signal power is constant, the voltages of the two DC bias power supplies are synchronously increased from 0, and the DC bias voltage values ​​required to achieve the high transmission state of the nonlinear LC resonant cavity bistability when the microwave signal is transmitted in the forward and reverse directions are detected respectively.

7. The control method of the device for realizing a controllable non-reciprocal microwave circuit according to claim 6, characterized in that: In step 1, very low microwave signal power refers to power less than 0.002 watts.

8. The control method of a device for realizing a controllable non-reciprocal microwave circuit according to claim 6, characterized in that: In step 2, the ratio of the left coupling capacitor C1 to the right coupling capacitor C2 is greater than 1.2 and less than 1.

5.

9. The control method of a device for realizing a controllable non-reciprocal microwave circuit according to claim 6, characterized in that: In step 3, when it is necessary to achieve forward conduction and reverse cutoff of the microwave signal, the following steps are also included: Detecting the DC bias voltage values ​​required to achieve a high transmission state during forward transmission of the microwave signal, and ensuring that when the DC bias voltage takes these values, the microwave signal is in a low transmission state during reverse transmission; By setting the DC bias voltage to any of these voltage values, the nonlinear interaction between the microwave signal in the nonlinear LC resonant cavity and the resonant mode of the nonlinear LC resonant cavity is regulated by the DC bias voltage. As a result, under the nonlinear effect, when the microwave signal is transmitted in the forward direction, the resonant mode wavelength of the nonlinear LC resonant cavity will be red-shifted and exactly equal to the wavelength of the incident microwave signal, thereby matching the resonance and achieving high transmittance of the microwave signal in the forward direction, that is, conduction; However, when the microwave signal is transmitted in the reverse direction, the energy in the nonlinear LC resonant cavity becomes very weak under the control of the DC bias voltage, which makes the red shift of the resonant wavelength of the nonlinear LC resonant cavity very small and cannot match the resonance of the incident microwave signal wavelength, thereby achieving low transmittance of the reverse transmission of the microwave signal, that is, cutoff.

10. The control method of the device for realizing a controllable non-reciprocal microwave circuit according to claim 6, characterized in that: In step 3, when it is necessary to realize controllable reversal of the conduction direction of the non-reciprocal microwave circuit at the same microwave signal wavelength and switch the forward conduction and reverse cutoff of the non-reciprocal microwave circuit to reverse conduction and forward cutoff, the following operations are performed: Detecting the DC bias voltage values ​​required to achieve a high transmission state when the microwave signal is transmitted in the reverse direction, and ensuring that when the DC bias voltage takes these values, the microwave signal is in a low transmission state when transmitted in the forward direction; By setting the DC bias voltage to any of these voltage values, the nonlinear interaction between the microwave signal in the nonlinear LC resonant cavity and the resonant mode of the nonlinear LC resonant cavity is regulated by the DC bias voltage. As a result, under the nonlinear effect, when the microwave signal is transmitted in the reverse direction, the resonant mode wavelength of the nonlinear LC resonant cavity will be red-shifted and exactly equal to the wavelength of the incident microwave signal, thereby matching the resonance and achieving high transmittance of the microwave signal in the reverse direction, that is, conduction. However, when the microwave signal is transmitted in the forward direction, the energy in the nonlinear LC resonant cavity becomes very weak under the control of the DC bias voltage, which makes the red shift of the resonant wavelength of the nonlinear LC resonant cavity very small and cannot match the resonance with the wavelength of the incident microwave signal, thereby achieving low transmittance of the microwave signal in the forward direction, that is, cutoff.

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