High-precision frequency mixing circuit based on variable capacitance characteristic

Abstract

The invention discloses a variable capacitance characteristic-based high-precision frequency mixing circuit, which comprises an input matching module, a choke filtering module, a power divider and n frequency mixing branches which are connected in sequence, and is characterized in that each frequency mixing branch has the same structure and comprises a frequency selection network, a field effect transistor MOSi, an inductor Li, a high-pass filtering module and an output matching module. Impedance matching and phase modulation are carried out on an input signal through the input matching module, then the input signal enters the choke filtering module to be filtered, then the input signal is equally divided into n input signals through the power divider, the n input signals enter the frequency mixing branch to be subjected to frequency mixing output, n output signals with higher frequency are obtained, and weighted output is carried out according to the selection frequency of the frequency selection network part. And a final more accurate result is obtained. According to the invention, a more accurate signal frequency mixing effect can be realized, and the device has the characteristics of simple structure, low noise coefficient, low cost and low power consumption, and has a wide application prospect in the transmitting, receiving and processing directions of electric wave signals.

Description

Technical Field

[0001] This invention belongs to the field of mixing circuit technology, specifically relating to the design of a high-precision mixing circuit based on varactor characteristics. Background Technology

[0002] Currently, in the field of electronic engineering, a sensor is a device that can sense external physical, chemical, or biological quantities and convert them into electrical signals or other processable signals. They are indispensable tools in modern technology and are widely used in industries such as manufacturing, medicine, automotive, and smart homes. Their core function is to convert non-electrical signals (such as temperature, pressure, light intensity, and sound) into electrical signals (such as voltage, current, and resistance) for subsequent processing, transmission, or storage.

[0003] Currently commonly used sensors include temperature sensors, pressure sensors, and gas sensors. They are mainly powered by an external power supply to the sensing circuit, and then the non-electrical signals collected are converted into electrical signals through ADC conversion and other methods. Then, they are processed by digital circuits and common signal processing to extract useful information, and finally the required digital quantity is obtained through calculation.

[0004] However, most sensors currently on the market are active and wired, requiring an external power supply to power the sensing circuitry. This results in high costs, is not environmentally friendly or energy-efficient, and many circuit components perform poorly at high frequencies, exhibiting distortion. Furthermore, most sensors rely on wired transmission for data transfer and communication between the sensor and the host, which is inconvenient and has a short transmission distance, making it unsuitable for long-distance transmission scenarios and limiting its application prospects. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of high cost, short transmission distance and easy distortion at high frequencies of existing active wired sensors, and to propose a high-precision mixing circuit based on the characteristics of variable capacitance.

[0006] The technical solution of this invention is as follows: a high-precision mixer circuit based on varactor characteristics, comprising an input matching module, a choke filter module, a power divider, and n mixer branches connected in sequence. Each mixer branch has the same structure, including a frequency selection network, a field-effect transistor (MOSFET) MOSi, an inductor Li, a high-pass filter module, and an output matching module. The gate of the MOSFET MOSi is connected to the output terminal of the power divider, the frequency selection network, and one end of the inductor Li, respectively. The source of the MOSFET MOSi and the other end of the inductor Li are both grounded. The drain of the MOSFET MOSi is connected to the input terminal of the high-pass filter module. The output terminal of the high-pass filter module is connected to the input terminal of the output matching module. The input terminal of the input matching module is the input terminal of the high-precision mixer circuit. The output terminal of the output matching module in the i-th mixer branch is the i-th output of the high-precision mixer circuit, i=1,2,…,n, where n is a natural number and n≥2.

[0007] Furthermore, the frequency selection network includes an inductor Ti and a variable capacitor TCi. One end of the primary coil of the inductor Ti is connected to the gate of the field-effect transistor MOSi, and one end of the secondary coil of the inductor Ti is connected to one end of the variable capacitor TCi. The other ends of the primary coil of the inductor Ti, the other end of the secondary coil, and the other end of the variable capacitor TCi are all grounded.

[0008] Furthermore, the formula for calculating the capacitive reactance of the variable capacitor TCi is: in This represents the capacitive reactance value of the variable capacitor TCi. Indicates the frequency of the input signal. This represents the signal frequency output by the i-th mixer branch. This represents the inductive reactance of the inductor coil Ti.

[0009] Furthermore, the high-pass filter module includes a resistor Ri and a capacitor Ci. One end of the resistor Ri and one end of the capacitor Ci are connected and serve as the input terminal of the high-pass filter module. The other end of the capacitor Ci serves as the output terminal of the high-pass filter module, and the other end of the resistor Ri is grounded.

[0010] Furthermore, the MOSFET incorporates a varactor diode for noise reduction and mixing of the input signal.

[0011] Furthermore, the output frequency of the high-precision mixer circuit for: in This represents the resonant frequency of the frequency selection network in the i-th mixing branch. This represents the signal frequency output by the i-th mixer branch.

[0012] The beneficial effects of this invention are: (1) The present invention uses the varactor characteristics of the varactor diode built into the field-effect transistor to denoise the input signal and perform frequency mixing. The resulting difference frequency signal has a lower frequency and less path loss. Therefore, the longer the propagation distance, the better it can be applied to signal transmission.

[0013] (2) When the present invention is used for sensor signals, multiple output signal frequencies can be obtained by designing multiple mixing branches, thereby obtaining the capacitive reactance value of the variable capacitor in each frequency selection network. By processing and analyzing the data (e.g., taking the average value), a more accurate capacitive reactance value can be obtained, thereby making the calculation accuracy of the sensor signal higher and it can be well applied to sensor networks.

[0014] (3) Based on the principle of the varactor characteristics of the varactor diode built into the field-effect transistor, the present invention performs noise reduction and frequency mixing on the input signal. The whole process is in a wireless and passive environment, which is more convenient and can also save a lot of cost and energy. At the same time, the circuit designed in this invention is easy to implement and has a low cost.

[0015] (4) The self-selected high-precision mixer circuit of the present invention can be composed of simple passive circuit elements (inductors, capacitors, etc.). It has made a breakthrough in circuit elements by selecting a large number of passive circuit devices, which have the characteristics of not needing additional power supply and good linearity, thus improving the performance in scenarios with higher power consumption requirements and greatly improving the performance of the mixer.

[0016] (5) The linearity of the present invention is generally good, which can reduce the influence of nonlinear distortion to a certain extent, improve the performance and stability of the mixer, and the passive wireless mixer also has a wide operating frequency range, can process signals of multiple frequency bands, and is suitable for applications such as broadband communication and spectrum monitoring. Attached Figure Description

[0017] Figure 1 The diagram shown is a schematic diagram of a high-precision mixer circuit structure based on the variable capacitance characteristic provided in an embodiment of the present invention. Detailed Implementation

[0018] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the invention, and are not intended to limit the scope of the invention.

[0019] This invention provides a high-precision mixer circuit based on varactor characteristics, comprising an input matching module, a choke filter module, a power divider, and n mixer branches connected in sequence. Each mixer branch has the same structure, including a frequency selection network, a field-effect transistor (MOSFET), an inductor (Li), a high-pass filter module, and an output matching module. The gate of the MOSFET is connected to the output terminal of the power divider, the frequency selection network, and one end of the inductor (Li). The source of the MOSFET and the other end of the inductor (Li) are both grounded. The drain of the MOSFET is connected to the input terminal of the high-pass filter module. The output terminal of the high-pass filter module is connected to the input terminal of the output matching module. The input terminal of the input matching module is the input terminal of the high-precision mixer circuit. The output terminal of the output matching module in the i-th mixer branch is the i-th output of the high-precision mixer circuit, where i = 1, 2, ..., n, and n is a natural number and n ≥ 2. This invention uses n = 2 as an example. Figure 1 As shown.

[0020] In embodiments of the present invention, such as Figure 1 As shown, the frequency selection network includes an inductor Ti and a variable capacitor TCi. One end of the primary coil of the inductor Ti is connected to the gate of the field-effect transistor MOSi, and one end of the secondary coil of the inductor Ti is connected to one end of the variable capacitor TCi. The other ends of the primary coil of the inductor Ti, the other end of the secondary coil, and the other end of the variable capacitor TCi are all grounded.

[0021] In this embodiment of the invention, for the n mixing branches, all circuit component parameters are the same except for the capacitive reactance value of the variable capacitor TCi. The variable capacitor TCi can be a varistor, a temperature-sensitive capacitor, etc., and its capacitive reactance value is calculated using the following formula: in This represents the capacitive reactance value of the variable capacitor TCi. Indicates the frequency of the input signal. This represents the signal frequency output by the i-th mixer branch. This represents the inductive reactance of the inductor coil Ti.

[0022] The capacitive reactance value of the variable capacitor TCi in each mixer branch Taking the average, we get: In this embodiment of the invention, a capacitive pressure sensor is used as an example, assuming the pressure Q The relationship between capacitance and capacitive reactance is expressed as follows: When n=2, the pressure change value is... It can be represented as: Therefore, for capacitive pressure sensors, based on the change in capacitance reactance... It can calculate the pressure magnitude and pressure change, thereby enabling real-time pressure monitoring.

[0023] In embodiments of the present invention, such as Figure 1 As shown, the high-pass filter module includes a resistor Ri and a capacitor Ci. One end of the resistor Ri and one end of the capacitor Ci are connected and serve as the input terminal of the high-pass filter module. The other end of the capacitor Ci serves as the output terminal of the high-pass filter module, and the other end of the resistor Ri is grounded.

[0024] In this embodiment of the invention, the field-effect transistor (MOSFET) MOSi incorporates a varactor diode for denoising and mixing the input signal. Specifically, the varactor diode between the gate and source of the MOSFET MOSi generates resonant signals of different frequencies based on the filtered input signal, which are then fed into a frequency selection network to select the desired resonant frequency, thus achieving signal denoising. The varactor diode between the gate and drain of the MOSFET MOSi performs mixing on the filtered input signal to obtain a higher frequency signal.

[0025] In this embodiment of the invention, the varactor diode built into the MOSFET can be replaced by other nonlinear components, including but not limited to parametric amplifiers, transistors, etc.

[0026] In embodiments of the present invention, such as Figure 1 As shown, the input signal undergoes impedance matching and phase modulation by the input matching module, then enters the choke filter module for filtering. It is then divided into n equal input signals by the power divider, which in turn enter the mixing branch for mixing and output, resulting in n higher-frequency output signals. These signals are then weighted according to the selected frequency by the frequency selection network to obtain a more accurate final result, i.e., the output frequency of the high-precision mixer circuit. : in This represents the resonant frequency of the frequency selection network in the i-th mixing branch. This represents the signal frequency output by the i-th mixer branch.

[0027] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A high-precision mixer circuit based on varactor characteristics, characterized in that, The system includes an input matching module, a choke filter module, a power divider, and n mixing branches connected in sequence. Each mixing branch has the same structure, including a frequency selection network, a field-effect transistor (MOSFET), an inductor (Li), a high-pass filter module, and an output matching module. The gate of the MOSFET is connected to the output terminal of the power divider, the frequency selection network, and one end of the inductor (Li). The source of the MOSFET and the other end of the inductor (Li) are both grounded. The drain of the MOSFET is connected to the input terminal of the high-pass filter module. The output terminal of the high-pass filter module is connected to the input terminal of the output matching module. The input terminal of the input matching module is the input terminal of the high-precision mixing circuit. The output terminal of the output matching module in the i-th mixing branch is the i-th output of the high-precision mixing circuit, where i = 1, 2, ..., n, and n is a natural number with n ≥ 2.

2. The high-precision mixer circuit based on varactor characteristics according to claim 1, characterized in that, The frequency selection network includes an inductor Ti and a variable capacitor TCi. One end of the primary coil of the inductor Ti is connected to the gate of the field-effect transistor MOSi, and one end of the secondary coil of the inductor Ti is connected to one end of the variable capacitor TCi. The other ends of the primary coil, the secondary coil, and the variable capacitor TCi are all grounded.

3. The high-precision mixer circuit based on varactor characteristics according to claim 2, characterized in that, The formula for calculating the capacitive reactance of the variable capacitor TCi is as follows: in This represents the capacitive reactance value of the variable capacitor TCi. Indicates the frequency of the input signal. This represents the signal frequency output by the i-th mixer branch. This represents the inductive reactance of the inductor coil Ti.

4. The high-precision mixer circuit based on varactor characteristics according to claim 1, characterized in that, The high-pass filter module includes a resistor Ri and a capacitor Ci. One end of the resistor Ri and one end of the capacitor Ci are connected and serve as the input terminal of the high-pass filter module. The other end of the capacitor Ci serves as the output terminal of the high-pass filter module. The other end of the resistor Ri is grounded.

5. The high-precision mixer circuit based on varactor characteristics according to claim 1, characterized in that, The field-effect transistor MOSi has a built-in varactor diode for noise reduction and mixing of the input signal.

6. The high-precision mixer circuit based on varactor characteristics according to claim 1, characterized in that, The output frequency of the high-precision mixer circuit for: in This represents the resonant frequency of the frequency selection network in the i-th mixing branch. This represents the signal frequency output by the i-th mixer branch.

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