CN113325412A

CN113325412A - Microstrip mixer and Doppler microwave detection module

Info

Publication number: CN113325412A
Application number: CN202110687999.1A
Authority: CN
Inventors: 邹高迪; 邹新
Original assignee: Shenzhen Merrytek Technology Co Ltd
Current assignee: Shenzhen Merrytek Technology Co Ltd
Priority date: 2021-06-21
Filing date: 2021-06-21
Publication date: 2021-08-31

Abstract

The invention provides a microstrip mixer and a Doppler microwave detection module with the microstrip mixer, wherein the microstrip mixer comprises an electric bridge, the impedance matching design of the microstrip mixer is guaranteed and the frequency selection characteristic of the microstrip mixer is improved at the same time by inhibiting the transient mode of an electric signal in the electric bridge in the state of maintaining the impedance characteristic of the electric bridge, the microstrip mixer only presents lower loss and narrowed frequency bandwidth in the working frequency band, the frequency selection characteristic of the microstrip mixer is excellent correspondingly, the output power and the anti-interference performance of Doppler intermediate frequency signals can be guaranteed, and the detection precision of the Doppler microwave detection module on the motion of an object in a corresponding detection space is further improved.

Description

Microstrip mixer and Doppler microwave detection module

Technical Field

The invention relates to the field of Doppler microwave detection, in particular to a microstrip mixer and a Doppler microwave detection module with the microstrip mixer.

Background

With the development of the internet of things technology, the requirements of artificial intelligence, smart home and intelligent security technology on environment detection, particularly on detection accuracy of human existence, movement and micro motion are higher and higher, and accurate judgment basis can be provided for intelligent terminal equipment only by acquiring a stable enough detection result. Among them, the radio technology, including the microwave detection technology based on the doppler effect principle, is used as a person and an object, and the important junction between the objects has unique advantages in the behavior detection and the existence detection technology, and can detect the action characteristics, the movement characteristics and the micromotion characteristics of a moving object, such as a person, even the heartbeat and the respiration characteristic information of the person without invading the privacy of the person, thereby having wide application prospect.

Specifically, the doppler microwave detection module in the prior art transmits a probe beam corresponding to the frequency of a local oscillator signal in a corresponding detection space through a mixer, and receives an echo formed by the probe beam being reflected by at least one object in the detection space to receive a feedback signal, wherein the mixer receives the feedback signal and outputs a doppler intermediate frequency signal corresponding to the frequency difference between the local oscillator signal and the feedback signal in a frequency mixing detection manner, and then the fluctuation of the doppler intermediate frequency signal in amplitude theoretically corresponds to the motion of the object in the detection space based on the doppler effect principle. Wherein, in order to ensure the feedback precision of the doppler intermediate frequency signal to the motion of the object in the detection space, based on the advantages of small noise and high sensitivity of the existing balanced mixer, the mixer of the doppler microwave detection module in the prior art mainly adopts a balanced mixer. Referring specifically to fig. 1 and 2 of the drawings accompanying the present specification, the equivalent circuit principle of the conventional balanced mixer and a microstrip balanced mixer using a two-branch 3dB bridge based on the equivalent circuit principle are respectively illustrated, wherein the balanced mixer includes a ring bridge 10P, two mixing pipes 20P and an intermediate frequency output port 30P, wherein the ring bridge 10P has a local oscillator signal input port 101P, a feedback signal input port 102P, a first mixing port 103P, a second mixing port 104P, a first microstrip arm 11P connected between the local oscillator signal input port 101P and the feedback signal input port 102P, a second microstrip arm 12P connected between the feedback signal input port 102P and the first mixing port 103P, a third microstrip arm 13P connected between the first mixing port 103P and the second mixing port 104P, and a fourth microstrip arm 14P connected between the second mixing port 104P and the local oscillation signal input port 101P, wherein the local oscillation signal input port 101P, the feedback signal input port 102P, the first mixing port 103P and the second mixing port 104P are sequentially arranged in a circular direction to form a microstrip frame structure in which the first microstrip arm 11P, the second microstrip arm 12P, the third microstrip arm 13P and the fourth microstrip arm 14P are connected end to end, wherein two ends of the two mixing pipes 20P having different polarities and belonging to different mixing pipes 20P are respectively connected to the first mixing port 103P and the second mixing port 104P, and the other two ends of the two mixing pipes 20P having different polarities and belonging to different mixing pipes 20P are connected to the same ground to ensure that the two ends are short-circuited to-ground at a high frequency, correspondingly, the two grounded ends of the two mixing tubes 20P are electrically connected to the intermediate frequency output port 30P, so as to form a high frequency filter for the intermediate frequency output port 30P, so that the powers of the local oscillation signal and the feedback signal respectively input from the local oscillation signal input port 101P and the feedback signal input port 102P can be all loaded on the two mixing tubes 30P without leaking to the intermediate frequency output port 30P, wherein the two grounded ends of the two mixing tubes 20P are electrically connected to the intermediate frequency output port 30P through two microstrip connection lines 31P having equal electrical length, thereby facilitating cancellation of noise current in the doppler intermediate frequency signal, and thus the balanced mixer presents advantages of low noise and high sensitivity.

In particular, the structural form of the balanced mixer has a plurality of variations based on the equivalent circuit principle of the balanced mixer, the main difference of which lies in the structural variation of the annular bridge 10P, in particular, referring to fig. 3 to 10 of the drawings of the present specification, different structures of the annular bridge 10P are illustrated, wherein fig. 3 to 9 illustrate typical two-branch bridges, three-branch bridges, variable resistance bridges, annular two-branch variable resistance bridges, annular bridges, broadband annular bridges, 180 ° hybrid annular bridges, respectively, which are conventional in the industry, wherein the specific embodiment of the annular bridge 10P is flexible based on the variation or combination variation of the different embodiments of the annular bridge 10P illustrated in fig. 3 to 9, the variant or combination variation of the different embodiments of the annular bridge 10P illustrated in fig. 3 to 9, corresponding to fig. 10, a structure of a balanced mixer applied to the conventional doppler microwave detection module is illustrated, although the specific implementation of the ring bridge 10P is flexible and variable, the corresponding equivalent circuit structure does not depart from the equivalent circuit principle illustrated in fig. 1, and the interference rejection capability of the balanced mixer under the condition of satisfying impedance matching still needs to be improved. Referring to fig. 11 and 12 of the drawings of the specification of the present invention specifically, based on the structural configuration of the balanced mixer illustrated in fig. 10, an impedance matching design example is performed on the balanced mixer at the operating frequency of the ISM band of 5.8GHz, and a frequency selection characteristic diagram and an interference rejection test diagram of the balanced mixer under the condition that impedance matching is satisfied are illustrated respectively. Corresponding to fig. 11, based on the characterization of the reflection coefficients of the local oscillator signal input port 101P and the feedback signal input port 102P by the S11 curve and the S22 curve, the loss of the balanced mixer at the 5.8GHz frequency point is significantly reduced to exhibit frequency selection characteristics, but on one hand, the loss of the balanced mixer at the 5.8GHz frequency point is only lower than-10 dB, and therefore is not ideal (generally required to be lower than-20 dB) and is difficult to ensure the doppler intermediate frequency signal output signal strength, and on the other hand, the loss of the balanced mixer in the frequency range lower than 3GHz is still lower than-5 dB and is difficult to resist the electromagnetic radiation interference in the frequency range lower than 3GHz, so that it is difficult to ensure the feedback accuracy of the doppler intermediate frequency signal on the movement of the object in the detection space in the now increasingly complex electromagnetic environment. Specifically, corresponding to fig. 12, an interference test is performed on the doppler intermediate frequency signal output by the balanced mixer based on a dynamic simulation of transmitting an interference signal in a frequency range from 80MHz to 6GHz (corresponding to a frequency range specified by the radiation immunity test of the IEC61000-4-3/GB T17626.3 latest standard), where the doppler intermediate frequency signal under the interference signal of a section of frequency is illustrated by a screenshot, and an amplitude change generated by the doppler intermediate frequency signal due to the interference of the interference signal of the section of frequency on the balanced mixer exceeds even 54.4 mV.

Disclosure of Invention

An object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein an S11 curve and an S22 curve of the microstrip mixer exhibit distinct narrow troughs in an operating frequency band corresponding to a frequency of a local oscillator signal, and the microstrip mixer has a low loss and a narrowed bandwidth in the operating frequency band, so that the microstrip mixer has an excellent frequency selection characteristic in the operating frequency band and can ensure an output signal strength of a corresponding doppler intermediate frequency signal.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the S11 curve and the S22 curve of the microstrip mixer tend to be flat and have high loss in a non-operating frequency band, that is, the S11 curve and the S22 curve of the microstrip mixer only present obvious narrow troughs in the operating frequency band, and have low loss and narrowed bandwidth only in the operating frequency band, and accordingly, the frequency selection characteristic of the microstrip mixer is excellent, so that the output signal strength and the anti-interference performance of the doppler intermediate frequency signal can be ensured, and further, the feedback accuracy of the doppler intermediate frequency signal to the motion of an object in a corresponding detection space can be improved.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the feedback accuracy of the doppler intermediate frequency signal to the motion of the object in the corresponding detection space is improved, and then the corresponding doppler microwave detection module is suitable for the combined detection of the motion characteristics including the movement, the micromotion, the respiration, and the heartbeat of the human body.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the microstrip mixer has low loss and a narrowed bandwidth only in the operating frequency band, so that the radiation immunity test based on IEC61000-4-3/GB T17626.3 standard does not generate an amplitude change exceeding the standard limit in the doppler intermediate frequency signal, and accordingly, the doppler microwave detection module can pass the radiation immunity test of IEC61000-4-3/GB T17626.3 standard, which is beneficial to the popularization of the doppler microwave detection module and the promotion of commercial competitiveness in the doppler microwave detection field.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the microstrip mixer includes a bridge, and the impedance characteristic of the bridge is maintained, so that the impedance matching design of the microstrip mixer is ensured and the frequency selection characteristic of the microstrip mixer is improved by suppressing the transient of the electrical signal in the bridge, and the microstrip mixer exhibits low loss and a narrowed bandwidth only in the operating frequency band.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the transient of the electrical signal in the electrical bridge is suppressed, the requirement of the electrical bridge for the high-frequency low-loss characteristic of its carrier is reduced, and accordingly, the electrical bridge is adapted to be carried by a common circuit board substrate, so as to facilitate the reduction of the cost of the doppler microwave detection module and the simplification of the production process of the doppler microwave detection module by avoiding the use of a microwave-dedicated circuit board substrate having the high-frequency low-loss characteristic.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the bridge includes a current suppressing element provided in the form of a device and a microstrip mixing line provided in the form of a microstrip line and connected between both ends of the current suppressing element, wherein the current suppressing element is provided in the form of a resistive element or a high-frequency inductive element to have transient suppression characteristics for an electrical signal, and is capable of maintaining a state in which impedance characteristics of the bridge are matched with impedance characteristics of the microstrip mixing line under the action of the local oscillator signal of a high frequency, differently from resistance or inductance characteristics of the microstrip mixing line under the action of the high-frequency electrical signal, so that suppression of the transient electrical signal in the bridge is formed in a state in which the impedance characteristics of the bridge are maintained by connecting the current suppressing element between both ends of the microstrip mixing line, the frequency selection characteristic of the microstrip mixer is improved while the impedance matching design of the microstrip mixer is ensured.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein in a state where the current suppressing element is set as the resistive element, the resistive element preferably adopts a zero-ohm resistive element to suppress a transient electric signal in the bridge while avoiding a change in impedance characteristics of the bridge, thereby further facilitating to maintain impedance characteristics of the bridge to match impedance characteristics of the microstrip mixing line under the action of the local oscillator signal of high frequency.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave probe module having the microstrip mixer, wherein the microstrip mixer further includes two mixing pipes and an intermediate frequency output port located at the microstrip mixing line, wherein the microstrip mixing line has a first mixing port, a local oscillation signal input port adapted for local oscillation signal input, a feedback signal input port adapted for local oscillation signal output and feedback signal input, and a second mixing port, a first microstrip mixing arm defined between the first mixing port and the local oscillation signal input port corresponding to the microstrip mixing line, a second microstrip mixing arm defined between the first mixing port and the local oscillation signal input port, and a third microstrip mixing arm defined between the local oscillation signal input port and the feedback signal input port, a fourth microstrip mixing arm defined between the feedback signal input port and the second mixing port, and a fifth microstrip mixing arm defined between the second mixing port and the other end, such that a state in which both ends of the current suppressing element are connected to the first mixing port via the first microstrip mixing arm and to the second mixing port via the fifth microstrip mixing arm, respectively, is formed in a state in which the current suppressing element is connected between both ends of the microstrip mixing line, wherein the second microstrip mixing arm and the fourth microstrip mixing arm have equal-length electrical lengths, and the third microstrip mixing arm has equal-length electrical lengths or more and equal-half-length electrical lengths, wherein two ends having different polarities belonging to different ones of the mixing pipes are connected to the first mixing port and the second mixing port, respectively, the other two ends of the two mixing tubes with different polarities are grounded so as to ensure that high frequencies of the two ends are short-circuited to the ground to form a high-frequency filter circuit between the first mixing port and the second mixing port, wherein the high-frequency filter circuit is formed by a line which is grounded by the first mixing port through one of the mixing tubes and a line which is grounded by the second mixing port through the other mixing tube, so that the powers of the local oscillation signal and the feedback signal which are respectively input from the local oscillation signal input port and the feedback signal input port can be all loaded on the two mixing tubes without leaking to the intermediate frequency output port.

Another objective of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the first microstrip mixing arm and the fifth microstrip mixing arm have equal electrical lengths, and have equal electrical lengths corresponding to connections between the first mixing port and the second mixing port and the current suppression element, so as to facilitate cancellation of noise current in the doppler intermediate frequency signal and to remove position limitation of the intermediate frequency output port on the microstrip mixing line, and accordingly, the microstrip mixer has various wiring modes to be adapted to different circuit layout requirements, and simultaneously, to improve feedback accuracy of the doppler intermediate frequency signal to motion of an object in a corresponding detection space.

Another objective of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein two ends of the two mixing tubes with different polarities, which are respectively connected to the first mixing port and the second mixing port, are electrically equal in length, so that when the two ends are respectively connected to the first mixing port and the second mixing port, the connections between the first mixing port and the second mixing port and the current suppressing element have equal electrical lengths, which is favorable for guaranteeing the feedback accuracy of the doppler intermediate frequency signal to the motion of the object in the corresponding detection space.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein two ends of the two mixer tubes with different polarities, which are respectively connected to the first microstrip mixer arm and the second microstrip mixer arm, are respectively connected to the first mixer port and the second mixer port, respectively, so as to simplify the structural design of the microstrip mixer.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the intermediate frequency output port is preferably located at a middle position of the third microstrip mixing arm, and two sections of the third microstrip mixing arm, which are bounded by the intermediate frequency output port, have equal electrical lengths, so as to avoid an influence of non-equal electrical length connections between the first mixing port and the second mixing port and the current suppressing element on the doppler intermediate frequency signal, which is caused by errors generated in a production process of the microstrip mixing line and an assembly process of the current suppressing element and the mixing tube, and reduce accuracy requirements on a production process of the microstrip mixing line and an assembly process of the current suppressing element and the mixing tube while ensuring feedback accuracy of the doppler intermediate frequency signal on motion of an object in a corresponding detection space, therefore, the method is simple and easy to implement and has low cost.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein a connection line between two mixing tubes and the first and second mixing ports is located in an area defined by sequential connection lines of the local oscillation signal input port, the first mixing port, the second mixing port, and the feedback signal input port, so as to reduce a size of a space occupied by the microstrip mixer, and to increase an amount of angular deviation in an extending direction of the connection line between the two mixing tubes and the first and second mixing ports with respect to the second and fourth microstrip mixing arms, thereby facilitating to further suppress transient electric signals in the bridge in parallel with the current suppressing element in a state of maintaining impedance characteristics of the microstrip mixing lines, and correspondingly ensuring the feedback precision of the Doppler intermediate frequency signal to the motion of the object in the corresponding detection space.

Another objective of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein at least one metal patch is connected to the high frequency filter circuit to improve the high frequency filter characteristic of the high frequency filter circuit by forming a distributed capacitor with the ground, and accordingly, the frequency selection characteristic of the microstrip mixer is improved, which is beneficial to improve the feedback accuracy of the doppler intermediate frequency signal to the motion of the object in the corresponding detection space.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the third microstrip mixing arm is bent, so as to further reduce the size of the space occupied by the microstrip mixer under the limitation that the third microstrip mixing arm has an electrical length greater than or equal to one eighth wavelength and less than or equal to one half wavelength.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave probe module having the same, in which the microstrip mixing lines are disposed symmetrically with respect to a center line of a line connecting the first mixing port and the second mixing port, so as to simultaneously satisfy an electrical length relationship between the microstrip mixing arms based on a simple configuration design of the microstrip mixing lines, thereby being easily implemented.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the doppler microwave detection module further includes a local oscillator circuit and an antenna, wherein the local oscillator circuit is configured to be powered to output the local oscillator signal, and is fed to the local oscillator signal input port of the microstrip mixer, and wherein the antenna is fed to the feedback signal input port of the microstrip mixer, such that the antenna can be fed by the local oscillator signal and input the feedback signal to the microstrip mixer via the microstrip mixer, and accordingly, the detection accuracy of the doppler microwave detection module for the motion of the object in the corresponding detection space is improved based on the above structural principle of the microstrip mixer.

Another object of the present invention is to provide a microstrip mixer and a doppler microwave detection module having the microstrip mixer, wherein the detection accuracy of the doppler microwave detection module is improved to be suitable for the combined detection of motion characteristics including movement, micromotion, respiration and heartbeat of a human body.

According to an aspect of the present invention, there is provided a microstrip mixer adapted to access a local oscillator signal and a feedback signal and output a doppler intermediate frequency signal corresponding to a frequency/phase difference between the local oscillator signal and the feedback signal by means of frequency mixing detection, wherein the microstrip mixer comprises:

a bridge, wherein the bridge comprises a current suppressing element and a microstrip mixing line, wherein the current suppressing element is provided as a resistive element or a high-frequency inductive element in the form of a component and is connected between both ends of the microstrip mixing line, wherein the microstrip mixing line has, in order from one end thereof, a first mixing port, a local oscillation signal input port adapted to the local oscillation signal input, a feedback signal input port adapted to the local oscillation signal output and the feedback signal input, and a second mixing port, having, in correspondence with the microstrip mixing line, a first microstrip mixing arm defined between the one end and the first mixing port, a second microstrip mixing arm defined between the first mixing port and the local oscillation signal input port, a third microstrip mixing arm defined between the local oscillation signal input port and the feedback signal input port, a fourth microstrip mixing arm defined between the feedback signal input port and the second mixing port, and a fifth microstrip mixing arm defined between the second mixing port and another end, wherein the second microstrip mixing arm and the fourth microstrip mixing arm have equal electrical lengths, and the third microstrip mixing arm has an electrical length greater than or equal to one-eighth wavelength and less than or equal to one-half wavelength;

two mixing tubes, wherein two ends of the two mixing tubes with different polarities are respectively connected to the first mixing port and the second mixing port, and the other two ends of the two mixing tubes with different polarities are grounded;

and the intermediate frequency output port is positioned on the microstrip mixing line so as to output the Doppler intermediate frequency signal at the intermediate frequency output port in a state that the local oscillation signal is input at the local oscillation signal input port and the feedback signal is input at the feedback signal input port.

In an embodiment, wherein the first microstrip mixing arm and the fifth microstrip mixing arm are arranged with equal electrical lengths.

In an embodiment, the connections between the two ends of the two mixing pipes connected to the first mixing port and the second mixing port and the corresponding first mixing port and the second mixing port have equal electrical lengths.

In one embodiment, the intermediate frequency output port is located at a middle position of the third microstrip mixing arm.

In an embodiment, a circuit between the first mixing port and the second mixing port, which is formed by a line where the first mixing port is grounded via one of the mixing tubes, and a line where the second mixing port is grounded via the other mixing tube, is defined as a high frequency filter circuit, wherein the microstrip mixer further includes at least one metal patch, wherein the metal patch is connected to the high frequency filter circuit to form a distributed capacitance with ground, so as to form a connection of the distributed capacitance with ground to the high frequency filter circuit, thereby improving a high frequency filtering characteristic of the high frequency filter circuit.

In an embodiment, in the high-frequency filter circuit, at least one of the metal patches is connected to the first mixing port via a line to which one of the mixing tubes is grounded and to the second mixing port via a line to which the other mixing tube is grounded, respectively.

In one embodiment, the microstrip mixer further comprises a ground patch, wherein the ground patch is grounded, and wherein the two grounded ends of the two mixing tubes are grounded in a state of being connected to the ground patch.

In an embodiment, the microstrip mixing lines are arranged symmetrically to a midline of a connection of the first and second mixing ports.

In an embodiment, the third microstrip mixing arm is folded.

In an embodiment, in a state in which the current suppressing element is set to the resistance element, the resistance element adopts a zero-ohm resistance element.

In an embodiment, a connection line between two of the mixing pipes and the first and second mixing ports is located in a ring region defined by a connection line between the first and second mixing ports and the second, third and fourth microstrip mixing arms.

In one embodiment, the first mixing port is connected to the respective mixing tubes by separate microstrip lines extending integrally from the first mixing port from the first microstrip arm and the second microstrip arm, and the second mixing port is connected to the respective mixing tubes by separate microstrip lines extending integrally from the second mixing port from the fourth microstrip arm and the fifth microstrip arm.

In an embodiment, of two ends of the two mixing pipes connected to the first mixing port and the second mixing port, one end connected to the first mixing port is connected to the first mixing port in a state of being connected to the first microstrip arm, and one end connected to the second mixing port is connected to the second mixing port in a state of being connected to the fifth microstrip arm.

In one embodiment, two of the mixer tubes are in a ring-shaped area defined by the microstrip mixer line and the bridge formed by the current suppressing element connected between the two ends of the microstrip mixer line.

In one embodiment, two of the mixer tubes are outside a loop area defined by the microstrip mixer line and the bridge formed by the current suppressing elements connected between the two ends of the microstrip mixer line.

According to another aspect of the present invention, there is also provided a doppler microwave detection module, comprising:

a local oscillator circuit, wherein the local oscillator circuit is configured to be enabled to be powered on and output a local oscillator signal;

an antenna, wherein the antenna comprises a reference ground and a radiation source spaced from the reference ground to equivalently form an open capacitor capable of receiving a feedback signal in an electromagnetic environment; and

a microstrip mixer, wherein said microstrip mixer comprises:

a microstrip mixer line having, in order from one end thereof, a first mixing port, a local oscillator signal input port adapted to the local oscillator signal input, a feedback signal input port adapted to the local oscillator signal output and the feedback signal input, and a second mixing port, corresponding to the microstrip mixer line, a first microstrip mixing arm defined between the one end and the first mixing port, a second microstrip mixing arm defined between the first mixing port and the local oscillator signal input port, a third microstrip mixing arm defined between the local oscillator signal input port and the feedback signal input port, a fourth microstrip mixing arm defined between the feedback signal input port and the second mixing port, and a fifth microstrip mixing arm defined between the second mixing port and the other end, wherein the microstrip mixing line is connected end to form an annular microstrip line state in which the first microstrip arm and the fifth microstrip arm are integrally connected, wherein the second microstrip mixing arm and the fourth microstrip mixing arm have equal electrical lengths, and the third microstrip mixing arm has an electrical length greater than or equal to one eighth and less than or equal to one half, wherein the local oscillator signal input port is fed and connected to the local oscillator circuit and the local oscillator signal is accessed in a state in which the local oscillator circuit is powered, wherein the radiation source is fed and connected to the feedback signal input port and fed by the local oscillator signal and inputs the feedback signal to the microstrip mixer;

two mixing tubes, wherein two ends of the two mixing tubes with different polarities are respectively connected to the first mixing port and the second mixing port, and the other two ends of the two mixing tubes with different polarities are grounded, wherein a connection line between the two mixing tubes and the first mixing port and the second mixing port is located in a ring region defined by a connection line of the first mixing port and the second microstrip mixing arm, and the third microstrip mixing arm and the fourth microstrip mixing arm together;

In one embodiment, the feed connection between the radiation source and the feedback signal input port is an open circuit connection coupled through a corresponding capacitor.

In one embodiment, the feed connection between the local oscillator circuit and the feedback signal input port is an open circuit connection coupled through a corresponding capacitor.

In one embodiment, two of the mixer tubes are within a ring region defined by the microstrip mixer lines.

In one embodiment, two of the mixer tubes are outside a ring area defined by the microstrip mixer lines.

In one embodiment, the microstrip mixer further comprises a ground patch, wherein the ground patch is grounded in a state of being connected to the reference ground, and wherein two ends of the two mixer tubes that are grounded in a state of being connected to the ground patch.

In an embodiment, the third microstrip mixing arm is folded.

In an embodiment, a circuit between the first mixing port and the second mixing port, which is formed by a line where the first mixing port is grounded via one of the mixing tubes, and a line where the second mixing port is grounded via the other mixing tube, is defined as a high frequency filter circuit, wherein the microstrip mixer further includes at least one metal patch, wherein the metal patch is connected to the high frequency filter circuit to form a distributed capacitance connected to the ground to the high frequency filter circuit, so as to form a distributed capacitance connected to the ground with respect to the ground reference, thereby improving the high frequency filtering characteristics of the high frequency filter circuit.

Further objects and advantages of the invention will be fully apparent from the ensuing description and drawings.

These and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description, the accompanying drawings and the claims.

Drawings

Fig. 1 is a schematic diagram of an equivalent circuit of a conventional balanced mixer.

Fig. 2 is a schematic diagram of a microstrip structure of a conventional microstrip balanced mixer using a two-branch 3dB bridge based on the equivalent circuit principle of the conventional balanced mixer.

Fig. 3 is a schematic diagram of a microstrip structure of a conventional two-branch bridge based on the equivalent circuit principle of a conventional balanced mixer.

Fig. 4 is a schematic diagram of a microstrip structure of a three-branch bridge based on the equivalent circuit principle of the prior balanced mixer.

Fig. 5 is a schematic diagram of a microstrip structure of a variable resistance bridge based on the equivalent circuit principle of a conventional balanced mixer.

Fig. 6 is a schematic diagram of a microstrip structure of a circular two-branch variable resistance bridge based on the equivalent circuit principle of the prior balanced mixer.

Fig. 7 is a schematic diagram of a microstrip structure of a ring bridge based on the equivalent circuit principle of a conventional balanced mixer.

Fig. 8 is a schematic diagram of a microstrip structure of a broadband ring bridge based on the equivalent circuit principle of a conventional balanced mixer.

Fig. 9 is a schematic diagram of a microstrip structure of a 180 ° hybrid ring bridge based on the equivalent circuit principle of a conventional balanced mixer.

Fig. 10 is a schematic diagram of another balanced mixer based on the equivalent circuit principle of the prior balanced mixer.

Fig. 11 is a frequency selection characteristic diagram of the balanced mixer under the condition of satisfying impedance matching.

Fig. 12 is an anti-interference test chart of the balanced mixer under the condition of satisfying impedance matching.

FIG. 13 is a schematic diagram illustrating an equivalent circuit of a microstrip mixer according to an embodiment of the invention.

Fig. 14A is a schematic diagram of a microstrip structure of the microstrip mixer according to the equivalent circuit principle of the above embodiment.

Fig. 14B is a schematic diagram of a microstrip structure variation of the microstrip mixer according to the equivalent circuit principle of the above embodiment.

Fig. 15A is a schematic diagram of another microstrip structure of the microstrip mixer according to the present invention based on the equivalent circuit principle of the above embodiment.

Fig. 15B is a schematic diagram of a microstrip structure variation of the microstrip mixer according to the equivalent circuit principle of the above embodiment.

Fig. 16A is a schematic diagram of another microstrip structure of the microstrip mixer according to the present invention based on the equivalent circuit principle of the above embodiment.

Fig. 16B is a schematic diagram of a microstrip structure variation of the microstrip mixer according to the equivalent circuit principle of the above embodiment.

Fig. 16C is a schematic diagram of a microstrip structure variation of the microstrip mixer according to the equivalent circuit principle of the above embodiment.

Fig. 17 is a frequency selection characteristic diagram of the microstrip mixer based on the equivalent circuit principle of the above embodiment according to the present invention, under the condition of satisfying impedance matching.

Fig. 18 is a graph of the anti-interference test of the microstrip mixer based on the equivalent circuit principle of the above embodiment under the condition of satisfying impedance matching according to the present invention.

FIG. 19 is an equivalent circuit schematic diagram of a Doppler microwave detection module with the microstrip mixer according to the present invention.

Detailed Description

The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.

It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for ease of description and simplicity of description, and do not indicate or imply that the referenced devices or components must be in a particular orientation, constructed and operated in a particular orientation, and thus the above terms are not to be construed as limiting the present invention.

It is understood that the terms "a" and "an" should be interpreted as meaning that a number of one element or element is one in one embodiment, while a number of other elements is one in another embodiment, and the terms "a" and "an" should not be interpreted as limiting the number.

The invention provides a microstrip mixer and a Doppler microwave detection module with the microstrip mixer, wherein the Doppler microwave detection module is suitable for transmitting a detection beam corresponding to the frequency of a local oscillator signal in a corresponding detection space through the microstrip mixer by feeding the detection beam by the local oscillator signal, receiving an echo formed by the reflection of the detection beam by at least one object in the detection space, and receiving a feedback signal, the mixer receives the feedback signal and outputs a Doppler intermediate frequency signal corresponding to the frequency difference between the local oscillator signal and the feedback signal in a frequency mixing detection mode, and the fluctuation of the Doppler intermediate frequency signal in amplitude theoretically corresponds to the movement of the object in the detection space based on the Doppler effect principle.

Referring to fig. 13 to 16C of the drawings of the present specification, the equivalent circuit principle of the microstrip mixer of the present invention and the structure of the microstrip mixer based on different embodiments of the equivalent circuit principle are respectively illustrated, wherein the balanced mixer includes a bridge 10, two mixer tubes 20 and an intermediate frequency output port 30, wherein the bridge 10 includes a current suppressing element 11 provided in the form of a component and a microstrip mixing line 12 provided in the form of a microstrip line and connected between two ends of the current suppressing element 11, wherein the current suppressing element 11 is provided in the form of a resistive element or a high frequency inductive element to have transient suppression characteristics for an electrical signal, and the impedance characteristics of the bridge 10 and the impedance characteristics of the microstrip mixing line 12 can be maintained under the action of the local oscillator signal of a high frequency unlike the resistance or inductance characteristics of the microstrip mixing line 12 under the action of the high frequency electrical signal In the matched state, the current suppressing element 11 is connected between the two ends of the microstrip mixer line 12, so that the transient electric signal in the bridge 10 is suppressed while the impedance characteristic of the bridge 10 is maintained, and the frequency selection characteristic of the microstrip mixer is improved while the impedance matching design of the microstrip mixer is ensured.

Specifically, the if output port 30 is located on the microstrip mixing line 12, wherein the microstrip mixing line 12 has a first mixing port 1201, a local oscillator input port 1202 adapted to the local oscillator input signal, a feedback signal input port 1203 adapted to the local oscillator output signal and the feedback signal input port, and a second mixing port 1204 sequentially from one end thereof, a first microstrip mixing arm 121 defined between the one end and the first mixing port 1201 corresponding to the microstrip mixing line 12, a second microstrip mixing arm 122 defined between the first mixing port 1201 and the local oscillator input port 1202, a third microstrip mixing arm 123 defined between the local oscillator input port 1202 and the feedback signal input port 1203, a fourth microstrip mixing arm 124 defined between the feedback signal input port 1203 and the second mixing port 1204, and a fifth microstrip mixing arm 125 defined between the second mixing port 1204 and the other end, such that a state in which both ends of the current suppressing element 11 are connected to the first mixing port 1201 via the first microstrip mixing arm 121 and the second mixing port 1204 via the fifth microstrip mixing arm 125, respectively, is formed in a state in which the current suppressing element 11 is connected between both ends of the microstrip mixing line 12, corresponding to a connection relationship with a bridge function between the current suppressing element 11 and the microstrip mixing line 12, wherein the second microstrip mixing arm 122 and the fourth microstrip mixing arm 124 have equal length of electricity, and the third microstrip mixing arm 123 has equal or more than one eighth wavelength of electricity and equal or less than one half wavelength of electricity, wherein both ends of the two mixing tubes 20 having different polarities are connected to the first mixing port 20, respectively And the second mixing port 1204, the other two ends of the two mixing tubes 20 with different polarities are grounded to ensure that the high frequencies of the two ends are short-circuited to ground, so as to form a high-frequency filter circuit between the first mixing port 1201 and the second mixing port 1204, the high-frequency filter circuit being formed by a line connected to ground through one of the mixing tubes 20 at the first mixing port 1201 and a line connected to ground through the other mixing tube 20 at the second mixing port 1204, so that the powers of the local oscillation signal and the feedback signal respectively input from the local oscillation signal input port 1202 and the feedback signal input port 1203 can be all applied to the two mixing tubes 20 without leaking to the intermediate frequency output port 30.

Preferably, in these embodiments of the present invention, the two mixing transistors 20 are disposed in a diode form, and the connection structure of the two diodes, which are respectively connected to the first mixing port 1201 and the second mixing port 1204 and have two ends with different polarities and belong to different diodes, specifically corresponds to: the anode of one of the diodes is connected to the second mixing port 1204, and the cathode of the other diode is connected to the first mixing port 1201, so as to improve the mixing efficiency of the microstrip mixer.

It is worth mentioning that in the state where the current suppressing element 11 is set as the resistive element, the resistive element preferably adopts a zero-ohm resistive element to suppress the transient electrical signal in the bridge 10 while avoiding the change of the impedance characteristic of the bridge 10, thereby further facilitating to maintain the impedance characteristic of the bridge 10 to match the impedance characteristic of the microstrip mixing line 12 under the action of the local oscillator signal of high frequency.

In particular, the first microstrip mixing arm 121 and the fifth microstrip mixing arm 125 are preferably configured to have equal electrical lengths, and the first mixing port 1201 and the second mixing port 1204 are electrically connected to the current suppressing element 11 by equal electrical lengths, so as to facilitate cancellation of noise current in the doppler intermediate frequency signal and to release the position limitation of the intermediate frequency output port 30 on the microstrip mixing line 12, and accordingly, the microstrip mixer is diversified in wiring manner to be adaptable to different circuit layout requirements, and at the same time, to facilitate improvement of the feedback accuracy of the doppler intermediate frequency signal to the motion of the object in the corresponding detection space.

Further, two ends of the two mixing tubes 20, which belong to different mixing tubes 20 and have different polarities, are preferably connected to the first mixing port 1201 and the second mixing port 1204 by equal electrical lengths, so that in a state where the two ends are connected to the first mixing port 1201 and the second mixing port 1204, respectively, it is ensured that the connections between the first mixing port 1201 and the second mixing port 1204 and the current suppressing element 11 have equal electrical lengths, and thus, it is favorable for ensuring the feedback accuracy of the doppler intermediate frequency signal on the motion of the object in the corresponding detection space.

In particular, the if output port 30 is preferably located at the middle position of the third microstrip mixing arm 123, and two sections of the third microstrip mixing arm 123 bounded by the if output port 30 have equal electrical lengths, so as to avoid the influence of the non-equal electrical length connection between the first mixing port 1201 and the second mixing port 1204 and the current suppressing element 11 caused by the error generated in the production process of the microstrip mixing line 12 and the assembly process of the current suppressing element 11 and the mixing tube 20 on the doppler if signal, and reduce the accuracy requirements on the production process of the microstrip mixing line 12 and the assembly process of the current suppressing element 11 and the mixing tube 20 while ensuring the feedback accuracy of the doppler if signal on the motion of the object in the corresponding detection space, and thus is simple and easy, the cost is low.

Optionally, the microstrip mixer further includes at least one metal patch 40, where the metal patch 40 is connected to the high-frequency filter circuit to be suitable for forming an enhancement to the high-frequency filter characteristic of the high-frequency filter circuit by forming a distributed capacitance with the ground, and correspondingly enhancing the frequency selection characteristic of the microstrip mixer to facilitate improving the feedback accuracy of the doppler intermediate frequency signal to the motion of the object in the corresponding detection space.

Preferably, in the high frequency filter circuit configured by a line in which the first mixing port 1201 is grounded via one of the mixing tubes 20 and a line in which the second mixing port 1204 is grounded via the other mixing tube 20, at least one of the metal patches 40 is connected to the line in which the first mixing port 1201 is grounded via one of the mixing tubes 20 and the line in which the second mixing port 1204 is grounded via the other mixing tube 20, respectively, thereby further facilitating cancellation of noise current in the doppler intermediate frequency signal.

Further, in these embodiments of the present invention, the connection line between the two mixing pipes 20 and the first mixing port 1201 and the second mixing port 1204 is located in the ring-shaped region defined by the connection line between the first mixing port 1201 and the second mixing port 1204 and the second microstrip mixing arm 122, the third microstrip mixing arm 123 and the fourth microstrip mixing arm 124, so as to reduce the size of the space occupied by the microstrip mixer, and to form and intensify the abrupt change of the angle of the connection line between the two mixing pipes 20 and the first mixing port 1201 and the second mixing port 1204 with respect to the second microstrip mixing arm 122 and the fourth microstrip mixing arm 124 in the extending direction, thereby facilitating to further suppress the transient electric signal in the bridge 10 in parallel with the current suppressing element 11 in a state of maintaining the impedance characteristic of the microstrip mixing line 12, and correspondingly ensuring the feedback precision of the Doppler intermediate frequency signal to the motion of the object in the corresponding detection space.

That is, in some embodiments of the present invention, in a state where a connection line between the two mixing pipes 20 and the first mixing port 1201 and the second mixing port 1204 is located in a ring region defined by a connection line between the first mixing port 1201 and the second mixing port 1204 and the second microstrip mixing arm 122, the third microstrip mixing arm 123, and the fourth microstrip mixing arm 124, the current suppressing element 11 may not be disposed, and the first microstrip arm 121 and the fifth microstrip arm 125 are integrally connected corresponding to a ring microstrip line state formed by connecting the microstrip mixing lines 12 end to end, which is not limited by the present invention.

Specifically, in these embodiments of the present invention, the microstrip mixer further includes a ground patch 50, wherein the ground patch 50 is grounded, two ends of the two mixing tubes 20 with different polarities respectively belonging to different mixing tubes 20 are connected to the first mixing port 1201 and the second mixing port 1204, and the other two ends of the two mixing tubes 20 with different polarities respectively belonging to different mixing tubes 20 are connected to the ground patch 50 and grounded.

It should be noted that the connection between the first mixing port 1201 and the corresponding mixing tube 20 allows a separate microstrip line, which integrally extends from the first mixing port 1201 to the first microstrip arm 121 and the second microstrip arm 122, to be directly connected to the corresponding mixing tube 20, corresponding to fig. 14A and 14B and fig. 16C, or to be connected to the corresponding mixing tube 20 via the first microstrip arm 121, corresponding to fig. 15A to 16B; similarly, the connection between the second mixing port 1204 and the corresponding mixing tube 20 allows a separate microstrip line integrally extending from the second mixing port 1204 to the fourth microstrip arm 124 and the fifth microstrip arm 125 to be directly connected to the corresponding mixing tube 20, corresponding to fig. 14A and 14B and fig. 16C, or to be connected to the corresponding mixing tube 20 via the fifth microstrip arm 125, corresponding to fig. 15A to 16B, which is not limited by the present invention.

That is, corresponding to fig. 15A to 16B, two ends of the two mixing pipes 20 with different polarities of the two mixing pipes 20 are connected to the first mixing port 1201 and the second mixing port 1204 respectively in a manner of being connected to the first microstrip mixing arm 121 and in a manner of being connected to the fifth microstrip mixing arm 125, so as to facilitate simplification of the structural design of the microstrip mixer, and the connection lines of the first microstrip mixing arm 121 and the fifth microstrip mixing arm 125 respectively to the first mixing port 1201 and the second mixing port 1204 and the second microstrip mixing arm 122, the third microstrip mixing arm 123 and the fourth microstrip mixing arm 124 are integrally extended in a ring region defined by the first microstrip mixing arm 121 and the fifth microstrip mixing arm 125 and the second microstrip mixing arm 122, the third microstrip mixing arm 123 and the fourth microstrip mixing arm 124, so as to form the connection lines between the two mixing pipes 20 and the first mixing port and the second mixing port 1204 A state of a connection line between the first mixing port 1201 and the second mixing port 1204 and a ring region defined by the second microstrip mixing arm 122, the third microstrip mixing arm 123, and the fourth microstrip mixing arm 124, which is not limited in the present invention.

It is worth mentioning that both ends of the current suppressing element 11 are respectively connected to the first mixing port 1201 and the second mixing port 1204 via the first microstrip mixing arm 121 and the fifth microstrip mixing arm 125, and a state in which two ends of the two mixing transistors 20 having different polarities, which belong to different mixing transistors 20, are connected to the first mixing port 1201 and the second mixing port 1204, respectively, and the other two ends of the two mixing transistors 20 having different polarities, which belong to different mixing transistors 20, are connected to ground, the current suppressing element 11 and the two mixing transistors 20 are connected in parallel between the first mixing port 1201 and the second mixing port 1204, wherein the parallel connection sequence between the current suppressing element 11 and the two mixing transistors 20 between the first mixing port 1201 and the second mixing port 1204 does not limit the present invention.

That is, in some embodiments of the present invention, corresponding to fig. 14A to 16C, two of the mixing pipes 20 are within a ring region defined by the microstrip mixing line 12 and the bridge 10 formed by the current suppressing element 11 connected between both ends of the microstrip mixing line 12, while in other embodiments of the present invention, two of the mixing pipes 20 are outside a ring region defined by the microstrip mixing line 12 and the bridge 10 formed by the current suppressing element 11 connected between both ends of the microstrip mixing line 12, and the connection lines between two of the mixing pipes 20 and the first and

second mixing ports

1201 and 1204 can be allowed to be located at the first and

second mixing ports

1201 and 1204 by increasing the amount of angular projection of the first and fifth

microstrip mixing arms

121 and 125 with respect to the second and fourth

microstrip mixing arms

122 and 124 in the extending direction The connection line of the frequency port 1204 is located in a ring-shaped region defined by the second microstrip mixing arm 122, the third microstrip mixing arm 123 and the fourth microstrip mixing arm 124, which is not limited in the present invention.

Further, in the embodiments of the present invention, the third microstrip mixing arm 123 is bent, so as to further reduce the size of the space occupied by the microstrip mixer under the limitation that the third microstrip mixing arm 123 has an electrical length greater than or equal to one eighth wavelength and less than or equal to one half wavelength.

In particular, corresponding to fig. 16A to 16C, in the state where the third microstrip mixing arm 123 is bent, the microstrip mixing line 12 is not designed in a bent form at the position of the local oscillator signal input port 1202 defined between the second microstrip mixing arm 122 and the third microstrip mixing arm 123 and at the position of the feedback signal input port 1203 defined between the third microstrip mixing arm 123 and the fourth microstrip mixing arm 124, that is, the local oscillator signal input port 1202 and the feedback signal input port 1203 are different from those of fig. 14A to 15B and are not located at the inflection point of the microstrip mixing line 12, so that, under the restriction that the third microstrip mixing arm 123 has an electrical length equal to or greater than one eighth wavelength and an electrical length equal to or less than one half wavelength, by the bending of the third microstrip mixing arm 123, while reducing the size of the space occupied by the microstrip mixer, the area of a ring-shaped area defined by the connection line of the first mixing port 1201 and the second mixing port 1204, the second microstrip mixing arm 122, the third microstrip mixing arm 123 and the fourth microstrip mixing arm 124 is ensured, so as to facilitate the circuit layout of the two mixing tubes 20 in the ring-shaped area.

Further, in the embodiments illustrated in fig. 14A to 16C, the microstrip mixing line 12 is arranged symmetrically with respect to the central line of the connecting line of the first mixing port 1201 and the second mixing port 1204, so that the electrical length relationship between the microstrip mixing arms can be simultaneously satisfied based on a simple form design of the microstrip mixing line, and thus it is easy to implement.

It is worth mentioning that, based on the equivalent circuit principle of the microstrip mixer of the present invention, the microstrip mixer has various structural configurations, wherein the second microstrip mixing arm 122 and the fourth microstrip mixing arm 124 have equal electrical lengths, the third microstrip mixing arm 123 has an electrical length greater than or equal to one eighth wavelength and an electrical length less than or equal to one half wavelength, two ends of the two mixing tubes 20 with different polarities are respectively connected to the first mixing port 1201 and the second mixing port 1204, the other ends of the two mixing tubes 20 with different polarities are grounded, and the current suppressing element 11 configured in a component configuration is connected to two ends of the microstrip mixing line 12 and/or a connection line between the two mixing tubes 20 and the first mixing port 1201 and the second mixing port 1204 is located at two ends of the mixing tubes 20 with different polarities The connection line of the first mixing port 1201 and the second mixing port 1204, the second microstrip mixing arm 122, the third microstrip mixing arm 123, and the fourth microstrip mixing arm 124 are designed to have a ring-shaped region defined by them, so that the transient of the electrical signal in the electrical bridge 10 can be suppressed while maintaining the impedance characteristic of the electrical bridge 10, and the frequency-selective characteristic of the microstrip mixer can be improved while ensuring the impedance matching design of the microstrip mixer.

Specifically referring to fig. 17 and 18 of the drawings accompanying the description of the present invention, based on the structural configuration of the balanced mixer illustrated in fig. 16A, an impedance matching design example is performed on the balanced mixer in the operating frequency band of the ISM frequency band of 5.8GHz, and a frequency selection characteristic diagram and an interference resistance test diagram of the balanced mixer under the condition that impedance matching is satisfied are illustrated respectively.

Corresponding to fig. 17, based on the characterization of the reflection coefficients of the local oscillator signal input port 1202 and the feedback signal input port 1203 by the curves S11 and S22, the balanced mixer exhibits an obvious narrow trough at the working frequency band of 5.8GHz, and the microstrip mixer has a lower loss and a narrowed bandwidth at the working frequency band, so that the frequency selection characteristic of the microstrip mixer at the working frequency band is excellent, and the output signal strength of the corresponding doppler intermediate frequency signal can be ensured.

Furthermore, the S11 curve and the S22 curve of the microstrip mixer tend to be flat and have high loss in the non-working frequency band, that is, the S11 curve and the S22 curve of the microstrip mixer are only in the working frequency band showing obvious narrow troughs, and the microstrip mixer is only in the working frequency band having low loss and narrowed frequency bandwidth, so that the microstrip mixer has excellent frequency selection characteristics, and can ensure the output signal strength and the anti-interference performance of the doppler intermediate frequency signal, thereby being beneficial to improving the feedback accuracy of the doppler intermediate frequency signal to the motion of the object in the corresponding detection space.

Corresponding to fig. 18, based on a dynamic analog test of transmitting an interference signal in the frequency range of 80MHz to 6GHz (corresponding to the frequency range specified by the radiation immunity test of the latest standard of IEC61000-4-3/GB T17626.3) to the doppler intermediate frequency signal output by the balanced mixer, the doppler intermediate frequency signal under the interference signal of one section of frequency is shown by the screenshot, wherein the interference of the interference signal of the section of frequency to the balanced mixer does not generate obvious amplitude change in the doppler intermediate frequency signal, and the doppler intermediate frequency signal tends to be flat correspondingly, the corresponding Doppler microwave detection module can pass the radiation immunity test of IEC61000-4-3/GB T17626.3 standard, which is beneficial to the popularization of the Doppler microwave detection module and the promotion of commercial competitiveness in the Doppler microwave detection field.

With further reference to fig. 19 of the drawings accompanying the description of the invention, the equivalent circuit principle of the doppler microwave detection module with the microstrip mixer is illustrated, wherein the doppler microwave detection module further comprises a local oscillator circuit 60 and an antenna 70, wherein the local oscillator circuit 60 is arranged to be powered to output the local oscillator signal and is fed to the local oscillator signal input port 1202 of the microstrip mixer, wherein the antenna 70 is fed connected to the feedback signal input port 1203 of the microstrip mixer, such that the antenna 70 can be fed by the local oscillator signal via the microstrip mixer and input the feedback signal to the microstrip mixer, the detection precision of the Doppler microwave detection module on the motion of the object in the corresponding detection space is improved correspondingly based on the structural principle of the microstrip mixer.

It should be noted that the feeding connection between the local oscillator circuit 60 and the feedback signal input port 1203 of the microstrip mixer and the feeding connection between the antenna 70 and the feedback signal input port 1203 of the microstrip mixer are via connections under the action of high-frequency electrical signals, so that the feeding connection between the local oscillator circuit 60 and the feedback signal input port 1203 of the microstrip mixer and the feeding connection between the antenna 70 and the feedback signal input port 1203 of the microstrip mixer are in a via connection form allowing direct connection in a physical circuit or in a disconnection connection form allowing coupling through corresponding capacitors (such as microstrip coupling capacitors, distributed capacitors and capacitive elements), which is not limited in this respect.

Preferably, the feeding connection between the antenna 70 and the feedback signal input port 1203 of the microstrip mixer is an open circuit connection configuration coupled by a corresponding capacitor in a physical circuit, so as to further improve the anti-interference performance of the doppler microwave detection module while ensuring the stability of the doppler microwave detection module by the high impedance characteristic of the capacitor to the low frequency signal and the isolation characteristic to the direct current signal.

Optionally, the feed connection between the local oscillator circuit 60 and the feedback signal input port 1203 of the microstrip mixer is an open circuit connection state in which the physical circuit is coupled by a corresponding capacitor, so that the stability of the doppler microwave detection module is guaranteed and the anti-interference performance of the doppler microwave detection module is further improved through the high impedance characteristic of the capacitor to the low frequency signal and the isolation characteristic to the direct current signal.

Further, the antenna 70 includes a reference ground and a radiation source spaced from the reference ground to equivalently form an open capacitor C₀Capable of generating the feedback signal in an electromagnetic environment, wherein the radiation source is fed to the feedback signal input port 1203 of the microstrip mixer to form a feeding connection relationship between the antenna 70 and the feedback signal input port 1203, wherein the reference ground is grounded and is equivalent to an equivalent capacitor C in fig. 19₀Corresponding to the radiation source equivalent to the open capacitor C in fig. 19₀Wherein the ground patch 50 is connected to the reference groundWhen the high-frequency filter circuit is grounded and the metal patch 40 is connected to the high-frequency filter circuit, a distributed capacitance can be formed between the metal patch 40 and the reference ground, thereby improving the high-frequency filter characteristic of the high-frequency filter circuit.

It is worth mentioning that in the description of the present invention, wherein due to the existence of industrial errors, the description and limitation of the relationship based on the electrical length allows to have an error range of 20% in practical measurement, such as "said second microstrip mixing arm 122 and said fourth microstrip mixing arm 124 have equal electrical lengths, and said third microstrip mixing arm 123 has an electrical length greater than or equal to one eighth wavelength and less than or equal to one half wavelength" should be understood as: the second microstrip mixing arm 122 and the fourth microstrip mixing arm 124 have equal electrical lengths within a tolerance range of 20%, and the third microstrip mixing arm 123 has an electrical length greater than or equal to one eighth wavelength and less than or equal to one half wavelength within a tolerance range of 20%.

It will be appreciated by persons skilled in the art that the above embodiments are only examples, wherein features of different embodiments may be combined with each other to obtain embodiments which are easily imaginable in accordance with the disclosure of the invention, but which are not explicitly indicated in the drawings, to which the invention is not limited.

It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are given by way of example only and are not limiting of the invention. The objects of the invention have been fully and effectively accomplished. The functional and structural principles of the present invention have been shown and described in the examples, and any variations or modifications of the embodiments of the present invention may be made without departing from the principles.

Claims

1. A microstrip mixer adapted to receive a local oscillator signal and a feedback signal and output a doppler intermediate frequency signal corresponding to a frequency/phase difference between the local oscillator signal and the feedback signal by means of frequency-mixing detection, comprising:

a bridge, wherein the bridge comprises a current suppressing element and a microstrip mixing line, wherein the current suppressing element is provided as a resistive element or a high-frequency inductive element in the form of a component and is connected between both ends of the microstrip mixing line, wherein the microstrip mixing line has, in order from one end thereof, a first mixing port, a local oscillation signal input port adapted to the local oscillation signal input, a feedback signal input port adapted to the feedback signal input, and a second mixing port, having, in correspondence with the microstrip mixing line, a first microstrip mixing arm defined between the one end and the first mixing port, a second microstrip mixing arm defined between the first mixing port and the local oscillation signal input port, a third microstrip mixing arm defined between the first mixing port and the local oscillation signal input port, a fourth microstrip mixing arm defined between the feedback signal input port and the second mixing port, and a fifth microstrip mixing arm defined between the second mixing port and another end, wherein the second microstrip mixing arm and the fourth microstrip mixing arm have equal electrical lengths, and the third microstrip mixing arm has an electrical length greater than or equal to one-eighth wavelength and less than or equal to one-half wavelength;

two mixing tubes, wherein two ends of the two mixing tubes with different polarities are respectively connected to the first mixing output port and the second mixing output port, and the other two ends of the two mixing tubes with different polarities are grounded;

2. The microstrip mixer according to claim 1, wherein said first microstrip mixing arm and said fifth microstrip mixing arm are provided with equal electrical lengths.

3. The microstrip mixer according to claim 2, wherein the connections between the two ends of the two mixing pipes connected to said first and second mixing ports and the respective first and second mixing ports have equal electrical lengths.

4. The microstrip mixer according to claim 3, wherein said mid frequency output port is located at a mid position of said third microstrip mixing arm.

5. The microstrip mixer according to claim 4, wherein a circuit between said first mixing port and said second mixing port, which is formed by a line where said first mixing port is grounded via one of said mixing tubes, and a line where said second mixing port is grounded via another of said mixing tubes, is defined as a high frequency filter circuit, wherein said microstrip mixer further comprises at least one metal patch, wherein said metal patch is connected to said high frequency filter circuit to form a connection of said distributed capacitance to ground to said high frequency filter circuit in a manner suitable for forming a distributed capacitance to ground, thereby improving a high frequency filtering characteristic of said high frequency filter circuit.

6. The microstrip mixer according to claim 5, wherein in said high frequency filter circuit, at least one of said metal patches is connected to said first mixing port via a line to which one of said mixing transistors is grounded and to said second mixing port via a line to which the other of said mixing transistors is grounded, respectively.

7. The microstrip mixer according to claim 4, wherein said microstrip mixer further comprises a ground patch, wherein said ground patch is grounded, and wherein both ends of said two mixing tubes that are grounded in a state of being connected to said ground patch.

8. The microstrip mixer according to claim 7, wherein said microstrip mixing lines are arranged symmetrically with respect to a midline of a connection of said first and second mixing ports.

9. The microstrip mixer according to claim 8, wherein said third microstrip mixing arm is meander-arranged.

10. The microstrip mixer according to claim 4, wherein said resistive element adopts a zero ohm resistive element in a state where said current suppressing element is set to said resistive element.

11. The microstrip mixer according to any of claims 1 to 10, wherein a connection between two of said mixing pipes and said first and second mixing ports is located within a ring-shaped region defined by a connection between said first and second mixing ports and said second microstrip mixing arm, said third microstrip mixing arm and said fourth microstrip mixing arm together.

12. The microstrip mixer according to claim 11, wherein said mixing transistors are arranged in diode form, wherein two ends of said diodes having different polarities belonging to different ones of said diodes are connected to said first mixing port and said second mixing port, respectively, wherein an anode of one of said diodes is connected to said second mixing port and a cathode of the other of said diodes is connected to said first mixing port.

13. The microstrip mixer according to claim 11, wherein said first mixing port is connected to a respective said mixing tube by a separate microstrip line extending integrally from said first mixing port from said first microstrip arm and said second microstrip arm, and said second mixing port is connected to a respective said mixing tube by a separate microstrip line extending integrally from said second mixing port from said fourth microstrip arm and said fifth microstrip arm.

14. The microstrip mixer according to claim 11, wherein one of two ends of said mixing tubes connected to said first mixing port and said second mixing port is connected to said first mixing port in a state of being connected to said first microstrip arm, and one of two ends of said mixing tubes connected to said second mixing port is connected to said second mixing port in a state of being connected to said fifth microstrip arm.

15. The microstrip mixer according to claim 11, wherein two of said mixing tubes are within a ring-shaped area defined by said microstrip mixing line and said bridge formed by said current suppressing element connected between the two ends of said microstrip mixing line.

16. The microstrip mixer according to claim 11, wherein both said mixing tubes are outside a ring-shaped area defined by said microstrip mixing line and said bridge formed by said current suppressing element connected between the two ends of said microstrip mixing line.

17. A doppler microwave detection module, comprising:

an antenna, wherein the antenna comprises a reference ground and a radiation source spaced from the reference ground to equivalently form an open capacitor capable of generating a feedback signal in an electromagnetic environment; and

a microstrip mixer, wherein said microstrip mixer comprises:

a microstrip mixing line having, in order from one end thereof, a first mixing port, a local oscillator signal input port adapted to the local oscillator signal input, a feedback signal input port adapted to the feedback signal input, and a second mixing port, a first microstrip mixing arm defined between the one end and the first mixing port, a second microstrip mixing arm defined between the first mixing port and the local oscillator signal input port, a third microstrip mixing arm defined between the local oscillator signal input port and the feedback signal input port, a fourth microstrip mixing arm defined between the feedback signal input port and the second mixing port, and a fifth microstrip mixing arm defined between the second mixing port and the other end, wherein the microstrip mixing lines are connected end to form an annular microstrip arm in which the first microstrip arm and the fifth microstrip arm are integrally connected A strip line configuration, wherein the second microstrip mixing arm and the fourth microstrip mixing arm have equal electrical lengths and the third microstrip mixing arm has an electrical length greater than or equal to one eighth and less than or equal to one half, wherein the local oscillator signal input port is fed to the local oscillator circuit and is switched in the local oscillator circuit in a powered state, wherein the radiation source is fed to the feedback signal input port and is fed by the local oscillator signal and inputs the feedback signal to the microstrip mixer;

an intermediate frequency output port, wherein the intermediate frequency output port is located on the microstrip mixing line, so as to output a doppler intermediate frequency signal corresponding to a frequency/phase difference between the local oscillator signal and the feedback signal at the intermediate frequency output port in a state where the local oscillator signal is input at the local oscillator signal input port and the feedback signal is input at the feedback signal input port.

18. The doppler microwave detection module of claim 17, wherein the feed connection between the radiation source and the feedback signal input port is physically disconnected by a corresponding capacitive coupling.

19. The doppler microwave detection module of claim 18, wherein the feed connection between the local oscillator circuit and the feedback signal input port is physically an open circuit coupled via a corresponding capacitor.

20. The doppler microwave detection module of claim 18, wherein two of the mixing tubes are within a ring-shaped region defined by the microstrip mixing lines.

21. The doppler microwave detection module of claim 18, wherein both of the mixing tubes are outside a toroid region defined by the microstrip mixing lines.

22. A doppler microwave detection module according to any one of claims 17 to 21, wherein the connections between the two ends of the mixing tubes connected to the first and second mixing ports and the respective first and second mixing ports have equal electrical lengths.

23. The doppler microwave detection module according to claim 22, wherein said microstrip mixer further comprises a ground patch, wherein said ground patch is grounded in a state of being connected to said reference ground, and wherein both ends of said two mixer tubes which are grounded in a state of being connected to said ground patch.

24. Doppler microwave detection module according to claim 23, wherein the third microstrip mixing arm is meander-arranged.

25. A doppler microwave detection module according to claim 24, wherein the intermediate frequency output port is located at a mid-position of the third microstrip mixing arm.

26. Doppler microwave detection module according to claim 25, wherein the microstrip mixing lines are arranged symmetrically to a middle line of a connection of the first and second mixing ports.

27. The doppler microwave detection module according to claim 22, wherein a circuit between the first mixing port and the second mixing port, which is formed by a line of the first mixing port grounded via one of the mixing tubes, and a line of the second mixing port grounded via the other mixing tube, is defined as a high frequency filter circuit, wherein the microstrip mixer further comprises at least one metal patch, wherein the metal patch is connected to the high frequency filter circuit to form a connection of the grounded distributed capacitor to the high frequency filter circuit in a manner suitable for forming a distributed capacitor with the ground reference, thereby improving a high frequency filtering characteristic of the high frequency filter circuit.

28. The doppler microwave detection module according to claim 27, wherein at least one of the metal patches is connected to the first mixing port via a line to which one of the mixing tubes is grounded and to the second mixing port via another line to which the other mixing tube is grounded in the high-frequency filter circuit.

29. The doppler microwave detection module according to claim 22, wherein two of the frequency mixing tubes are arranged in a form of diodes, wherein two ends of the two diodes having different polarities, which are respectively assigned to different diodes, are respectively connected to the first frequency mixing port and the second frequency mixing port, wherein an anode of one of the diodes is connected to the second frequency mixing port, and a cathode of the other diode is connected to the first frequency mixing port.