Frequency tunable nonreciprocal transmission system based on PT symmetry principle and detection method thereof

Abstract

The application discloses a frequency-adjustable non-reciprocal transmission system based on a PT symmetry principle and a detection method thereof, and the circuit system comprises a loss resonance module of inductance-capacitance-positive resistance parallel resonance, an adjustable coupling module and a gain resonance module of inductance-capacitance-negative resistance parallel connection; wherein the loss resonance module and the gain resonance module are connected through the adjustable capacitance coupling module to form a PT symmetric system; signal transmission from the loss resonance module to the gain resonance module is forward transmission, and vice versa is reverse transmission. By changing the adjustable capacitance coupling module, the coupling coefficient between the loss module and the gain module is changed, so that the transmission frequency of the system is changed. The amplitude of the transmission signal is adjusted, the saturation property of the negative resistance in the gain resonance module is utilized to realize the difference between the forward transmission coefficient and the reverse transmission coefficient, and non-reciprocal transmission is realized. The system has the advantages of high non-reciprocal ratio, low insertion loss and the like.

Description

Technical Field

[0001] This invention belongs to the field of two-port transmission systems, and particularly relates to a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle and its detection method. Background Technology

[0002] Two-port transmission circuits are divided into reciprocal transmission circuits and non-reciprocal transmission circuits. A reciprocal transmission circuit is defined as one where the signal propagates identically between the two ports; therefore, it is non-directional and typically constructed using passive components. Conversely, a non-reciprocal transmission circuit is defined as one where the signal propagates differently between the two ports; changing the input signal port will result in different output signal amplitudes at the other port. It is directional and typically constructed using magnetic or non-linear active components. Non-reciprocal transmission circuits can be used to construct non-reciprocal transmission of acoustic and electrical signals, and are commonly used in circulators and isolators. Current non-reciprocal transmission systems can only achieve non-reciprocal transmission of single-frequency signals. If the signal frequency changes, a new non-reciprocal transmission system needs to be built, which significantly increases cost and inconvenience in applications, making it unsuitable for variable-frequency environments. Therefore, it is essential to invent a frequency-tunable non-reciprocal transmission system. Summary of the Invention

[0003] The purpose of this invention is to provide a frequency-tunable non-reciprocal transmission system and its detection method based on the PT symmetry principle. A coupling module for the PT symmetry system is constructed using adjustable capacitors, enabling frequency adjustment of the transmitted signal in the broken region of the PT symmetry system. By utilizing the nonlinearity of the transimpedance amplifier, non-reciprocal transmission of the signal between two ports is achieved. This addresses the technical problem that current non-reciprocal transmission systems can only achieve non-reciprocal transmission of a single frequency signal. If the signal frequency changes, a new non-reciprocal transmission system needs to be fabricated, which greatly increases cost and inconvenience in applications and is unsuitable for variable frequency applications.

[0004] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0005] A frequency-tunable non-reciprocal transmission system based on the PT symmetry principle is disclosed, comprising a loss resonant circuit, a gain resonant circuit, and an adjustable coupling module. The gain resonant circuit consists of a second inductor, a positive resistor, and a negative resistor connected in parallel, wherein the negative resistor is formed by a transimpedance amplifier. When the transimpedance amplifier operates in the linear region, the negative resistor is a fixed negative resistor that does not change with the input voltage. When the transimpedance amplifier operates in the negative saturation region, the resistance of the negative resistor is controlled by the input voltage. The loss resonant circuit and the gain resonant circuit are coupled together through the adjustable coupling module. By changing the coupling capacitance of the adjustable coupling module, the coupling coefficient between the loss resonant circuit and the gain resonant circuit is changed, thereby changing the transmission frequency of the system.

[0006] Furthermore, the loss resonant circuit is composed of a first inductor, a first capacitor, and a positive resistor connected in parallel.

[0007] Furthermore, the transimpedance amplifier includes a first resistor, an operational amplifier, a second resistor, and a third resistor; the first resistor is connected between the non-inverting input terminal and the output terminal of the operational amplifier, the second negative resistor is connected between the inverting input terminal and the output terminal of the operational amplifier, and one end of the third resistor is grounded and the other end is connected to the second resistor.

[0008] Furthermore, the adjustable coupling module is composed of adjustable capacitors.

[0009] Furthermore, the first inductor and positive resistor in the loss resonant circuit are equal to the second inductor and negative resistor in the gain resonant circuit, respectively.

[0010] Furthermore, the absolute value of the positive resistor in the loss resonant circuit is equal to the absolute value of the negative resistor in the gain resonant circuit when it operates in the linear region.

[0011] A detection method for a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle includes the following steps:

[0012] Step 1: Adjust the resistance value of the transimpedance amplifier so that the absolute value of the equivalent negative resistance in the linear region of the transimpedance amplifier is equal to the absolute value of the positive resistance of the loss resonant circuit, so that the system is in a PT symmetrical state.

[0013] Step 2: Adjust the capacitance value of the adjustable coupling module so that its value is within...

[0014] Between these points, the system is in the PT-symmetric broken region; where C L It is the capacitor of the loss resonant circuit, R L It is the positive resistance of the loss resonant circuit, L L It is the inductor of a lossy resonant circuit;

[0015] Step 3: Adjust the amplitude of the input signal. Define the transmission of the signal from the loss resonant circuit to the gain resonant circuit as positive transmission. At this time, the negative resistor works in the linear region. Define the transmission of the signal from the gain resonant circuit to the loss resonant circuit as reverse transmission. At this time, the negative resistor works in the negative saturation region. Since the equivalent negative resistance of the transimpedance amplifier is different during positive and reverse transmission, the system forms non-reciprocal transmission.

[0016] Step 4: Adjust the adjustable capacitance value of the adjustable coupling module to make it... The frequency of signal transmission changes between these parameters, thus creating a non-reciprocal transmission system with tunable transmission frequency.

[0017] The frequency-tunable non-reciprocal transmission system and its detection method based on the PT symmetry principle of the present invention have the following advantages:

[0018] This invention alters the coupling coefficient between the loss and gain modules by changing the adjustable capacitive coupling module, thereby changing the system's transmission frequency. By adjusting the amplitude of the transmitted signal and utilizing the saturation property of the negative resistor in the gain resonant module, the difference between the forward and reverse transmission coefficients is achieved, enabling non-reciprocal transmission. This system offers advantages such as high non-reciprocity ratio, low insertion loss, and adjustable frequency. Attached Figure Description

[0019] Figure 1 This is an equivalent circuit diagram of a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle of the present invention.

[0020] The markings in the diagram are as follows: 1. Loss resonant circuit; 2. Gain resonant circuit; 3. Adjustable coupling module; 11. First capacitor; 12. Positive resistor; 13. First inductor; 21. Second capacitor; 22. Negative resistor; 23. Second inductor; 221. First resistor; 222. Operational amplifier; 223. Second resistor; 224. Third resistor. Detailed Implementation

[0021] To better understand the purpose, structure, and function of this invention, the following detailed description, in conjunction with the accompanying drawings, provides a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle and its detection method.

[0022] Based on the relationship between coupling coefficient and loss factor, PT-symmetric systems can be divided into three operating regions: the PT-symmetric region, the PT-symmetric critical point, and the PT-symmetric broken region. When the coupling coefficient is greater than the critical coupling coefficient, the system is in the PT symmetry region. The system resonant frequencies in the PT symmetry region are two unequal real numbers. The signal amplitudes of the loss resonant circuit and the gain resonant circuit are the same, which can be applied to the equal amplitude transmission of signals. When the coupling coefficient is equal to the critical coupling coefficient, the system is in the PT symmetry critical point. The system resonant frequencies at the PT symmetry critical point will merge into a single real frequency. When there is a perturbation in the system, the real frequency will split. The frequency difference of the split is very sensitive to the perturbation and is often used in the design of high-sensitivity sensors. When the coupling coefficient is less than the critical coupling coefficient, the system is in the PT symmetry broken region. The system resonant frequencies in the PT symmetry broken region are two complex numbers with the same real part but opposite imaginary parts. The signal amplitude of the loss resonant circuit decreases exponentially with time, while the signal amplitude of the gain resonant circuit increases exponentially with time. Due to the nonlinearity of the negative resistance device, the signal amplitude of the gain resonant circuit will be nonlinearly amplified after the transimpedance amplifier enters the negative saturation region, resulting in unequal transmission coefficients in the two transmission directions. This can be used to construct non-reciprocal transmission systems.

[0023] like Figure 1 As shown, a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle consists of three parts: a loss resonant circuit 1, a gain resonant circuit 2, and an adjustable coupling module 3. The gain resonant circuit 2 is composed of a second inductor 23, a positive resistor 12, and a negative resistor 22 connected in parallel. The negative resistor 22 is formed by a transimpedance amplifier. When the transimpedance amplifier operates in the linear region, the negative resistor 22 is a fixed negative resistor that does not change with the input voltage. When the transimpedance amplifier operates in the negative saturation region, the resistance of the negative resistor 22 is a negative resistor controlled by the input voltage. The loss resonant circuit 1 and the gain resonant circuit 2 are coupled together through the adjustable coupling module 3. By changing the coupling capacitance of the adjustable coupling module 3, the coupling coefficient between the loss resonant circuit 1 and the gain resonant circuit 2 is changed, thereby changing the transmission frequency of the system.

[0024] The loss resonant circuit 1 is composed of a first inductor 13, a first capacitor 11 and a positive resistor 12 connected in parallel.

[0025] The transimpedance amplifier includes a first resistor 221, an operational amplifier 222, a second resistor 223, and a third resistor 224. The first resistor 221 is connected between the non-inverting input terminal and the output terminal of the operational amplifier 222, the second negative resistor 223 is connected between the inverting input terminal and the output terminal of the operational amplifier 222, and one end of the third resistor 224 is grounded and the other end is connected to the second resistor 223.

[0026] The adjustable coupling module 3 is composed of an adjustable capacitor.

[0027] The first inductor 13 and the positive resistor 12 in the loss resonant circuit 1 are equal to the second inductor 23 and the negative resistor 22 in the gain resonant circuit 2, respectively.

[0028] The absolute value of the positive resistor 11 in the loss resonant circuit 1 is equal to the absolute value of the negative resistor 21 in the gain resonant circuit when it is operating in the linear region.

[0029] Adjust the first resistor 221, the second resistor 223, and the third resistor 224 to satisfy the formula.

[0030] Where R1 is the first resistor 221, R2 is the second resistor 223, and R3 is the third resistor 224.

[0031] The loss factor is defined by the symbol γ, and the loss factor satisfies the formula... Where C L It is a lossy resonant circuit with capacitor 11 and R. L It is a lossy resonant circuit with a positive resistor of 12 L. L It is the inductor 13 in the loss resonant circuit.

[0032] The capacitive coupling coefficient is defined by the symbol c, and the capacitive coupling coefficient satisfies the formula... The capacitance variation range of the adjustable coupling module is set to satisfy the formula. Ensure the system operates in the PT symmetry broken region. Adjust the capacitance value of the adjustable coupling module (3), and then measure the forward and reverse transmission coefficients of the transimpedance amplifier (22) under the condition of negative saturation. This will enable a frequency-tunable non-reciprocal transmission system.

[0033] Its specific working process is as follows:

[0034] like Figure 1 Operational amplifier 222, along with first resistor 221, second resistor 223, and third resistor 224, constitute a transimpedance amplifier. Initially, adjusting its linear region resistance satisfies the formula... As the signal amplitude increases, the transimpedance amplifier will enter the saturation region;

[0035] The range of values ​​for the adjustable coupling module capacitor must satisfy...

[0036] Given a suitable input signal amplitude, the transimpedance amplifier module is in the negative saturation region for reverse transmission and in the linear region for forward transmission. Then, the forward and reverse transmission coefficients are measured under the condition of changing the signal frequency while keeping the signal amplitude constant.

[0037] exist By adjusting the capacitance value of the adjustable coupling module within the range and repeating the above steps, frequency-adjustable non-reciprocal transmission measurement results can be obtained.

[0038] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A detection method for a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle, characterized in that, The transmission system consists of three parts: a loss resonant circuit (1), a gain resonant circuit (2), and an adjustable coupling module (3). The gain resonant circuit (2) is composed of a second inductor (23), a positive resistor (12), and a negative resistor (22) connected in parallel. The negative resistor (22) is composed of a transimpedance amplifier. When the transimpedance amplifier is working in the linear region, the negative resistor (22) is a fixed negative resistor that does not change with the input voltage. When the transimpedance amplifier is working in the negative saturation region, the resistance of the negative resistor (22) is a negative resistor controlled by the input voltage. The loss resonant circuit (1) and the gain resonant circuit (2) are coupled together through the adjustable coupling module (3). By changing the coupling capacitance of the adjustable coupling module (3), the coupling coefficient between the loss resonant circuit (1) and the gain resonant circuit (2) is changed, thereby changing the transmission frequency of the system. The loss resonant circuit (1) is composed of a first inductor (13), a first capacitor (11), and a positive resistor (12) connected in parallel; The detection method includes the following steps: Step 1: Adjust the resistance value of the transimpedance amplifier so that the absolute value of the equivalent negative resistance value of the linear region of the transimpedance amplifier is equal to the absolute value of the positive resistance (12) of the loss resonant circuit (1), so that the system is in a PT symmetrical state. Step 2, adjust the capacitance value of the adjustable coupling module (3) so that its value is within the range of... Between these points, the system is in the PT-symmetric broken region; where It is the capacitor (11) of the loss resonant circuit. It is the positive resistor (12) of the loss resonant circuit. It is the inductance of the loss resonant circuit (13); Step 3, adjust the amplitude of the input signal, define the transmission of the signal from the loss resonant circuit (1) to the gain resonant circuit (2) as positive transmission, at this time the negative resistor (22) works in the linear region, define the transmission of the signal from the gain resonant circuit (2) to the loss resonant circuit (1) as reverse transmission, at this time the negative resistor (22) works in the negative saturation region. Since the equivalent negative resistance of the transimpedance amplifier is different during positive and reverse transmission, the system forms non-reciprocal transmission; Step 4: Adjust the adjustable capacitance value of the adjustable coupling module (3) so that it is within the range of the adjustable coupling module (3). The frequency of signal transmission changes between these parameters, thus creating a non-reciprocal transmission system with tunable transmission frequency.

2. The detection method for a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle according to claim 1, characterized in that, The transimpedance amplifier includes a first resistor (221), an operational amplifier (222), a second resistor (223), and a third resistor (224). The first resistor (221) is connected between the non-inverting input terminal and the output terminal of the operational amplifier (222), the second negative resistor (223) is connected between the inverting input terminal and the output terminal of the operational amplifier (222), and one end of the third resistor (224) is grounded and the other end is connected to the second resistor (223).

3. The detection method for a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle according to claim 1, characterized in that, The adjustable coupling module (3) is composed of an adjustable capacitor.

4. The detection method for a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle according to claim 1, characterized in that, The first inductor (13) and positive resistor (12) in the loss resonant circuit (1) are equal to the second inductor (23) and negative resistor (22) in the gain resonant circuit (2), respectively.

5. The detection method for a frequency-tunable non-reciprocal transmission system based on the PT symmetry principle according to claim 1, characterized in that, The resistance value of the positive resistor (11) in the loss resonant circuit (1) is equal to the absolute value of the resistance value of the negative resistor (21) in the gain resonant circuit when it is operating in the linear region.

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