CN101442148B - Impedance matching method of microstrip-waveguide conversion probe - Google Patents

Abstract

The invention discloses an impedance matching method of a microstrip-waveguide conversion probe, and belongs to the technical field of electromagnetic fields and microwave circuits. The method comprises the following steps: designing to obtain the size of a conversion probe according to the back-to-back microstrip-waveguide conversion probe structure; placing a section of microstrip line in the middle of the back-to-back microstrip-waveguide conversion probe structure; transforming the width of the microstrip line to perform computer simulation to obtain the input impedance of the conversion probe; the input impedance is matched to 50 ohms using an 1/4 wavelength impedance transformation line. The invention combines the design of the size of the conversion probe with the impedance calculation, namely, the impedance matching design is completed while the microstrip-waveguide conversion probe is designed, the input impedance of the conversion probe is very conveniently obtained, and the matching circuit design is further realized; the method has simple operation and simple process, simplifies the matching circuit and improves the accuracy of impedance matching.

Description

A Method of Impedance Matching for Microstrip-Waveguide Conversion Probe

technical field

The invention relates to the technical field of electromagnetic fields and microwave circuits, in particular to an impedance matching method of a microstrip-waveguide conversion probe.

Background technique

With the rapid development of microwave and millimeter wave transceiver systems, a more compact microstrip-waveguide transition is required. At present, the commonly used microstrip-waveguide transition forms mainly include: ridge waveguide transition, antipolar fin line transition and microstrip probe transition and so on. Among them, the microstrip probe transition is the most widely used microstrip-waveguide transition form at present. Its advantages are: low insertion loss, small return loss, wide frequency band, compact structure, convenient processing, easy assembly and disassembly, especially suitable for mm wave application.

In the design process of the microstrip probe, it is necessary to match its input impedance to 50 ohms, so as to facilitate connection with the subsequent circuit (its input and output impedance is generally 50 ohms), thereby reducing standing waves, improving power gain and system stability. stability. The traditional impedance matching method of converting a microstrip probe is: design the size of the microstrip probe by software, obtain the input impedance of the microstrip probe by computer simulation; substitute the input impedance into other impedance matching software to design a matching circuit, and then Impedance matched to 50 ohms. However, this method is relatively complicated to operate, and the process is cumbersome, and the impedance matching circuit is complicated, and the impedance matching accuracy is not high.

Contents of the invention

In order to simplify the design process of the microstrip-waveguide conversion probe and improve the precision of impedance matching, the invention provides a method for impedance matching of the microstrip-waveguide conversion probe, the method comprising:

Step A: According to the back-to-back microstrip-waveguide conversion probe structure, design the conversion probe size;

Step B: placing a section of microstrip line in the middle of the back-to-back microstrip-waveguide conversion probe structure;

Step C: change the width of the microstrip line and carry out computer simulation, and compare the simulation results with the simulation results of the conversion probe structure without the microstrip line; when the microstrip line is at a certain width, its characteristic The impedance is the same as the center point impedance of the back-to-back microstrip-waveguide conversion probe structure, and the simulation result is consistent with the simulation result of the conversion probe structure without the microstrip line, and obtained according to the width of the microstrip line at this time the input impedance of the conversion probe;

Step D: Match the input impedance to 50 ohms by using a 1/4 wavelength impedance transformation line.

The back-to-back microstrip-waveguide conversion probe structure is composed of two completely symmetrical conversion probe structures, and the central point impedance of the back-to-back microstrip-waveguide conversion probe structure is pure real part impedance.

The input impedance is a pure real part impedance.

The impedance transformation line is used to transform the pure real part impedance into the impedance required by the subsequent stage circuit.

Beneficial effects: the present invention combines the design of the size of the conversion probe itself with the impedance calculation, that is, while designing the microstrip-waveguide conversion probe, the impedance matching design is completed, and the input impedance of the conversion probe is obtained very conveniently. Then the matching circuit design is realized; this method is simple in operation and process, simplifies the matching circuit, and improves the accuracy of impedance matching.

Description of drawings

1 is a three-dimensional schematic diagram of a back-to-back microstrip-waveguide conversion probe structure according to an embodiment of the present invention;

Fig. 2 is a schematic cross-sectional view of a back-to-back microstrip-waveguide conversion probe structure according to an embodiment of the present invention;

3 is a three-dimensional schematic diagram of a back-to-back microstrip-waveguide conversion probe structure with microstrip lines placed in an embodiment of the present invention;

Fig. 4 is a schematic cross-sectional view of a conversion probe and a matching circuit that realizes impedance matching by using a 1/4 wavelength impedance conversion line according to an embodiment of the present invention;

Fig. 5 is a flow chart of the impedance matching method of the microstrip-waveguide conversion probe provided by the embodiment of the present invention;

Fig. 6 is a microstrip-waveguide conversion probe structure provided by an embodiment of the present invention applied to a small signal insertion loss test diagram in the Ka band;

Fig. 7 is a reflection test diagram of the input and output ports of the Ka band applied to the microstrip-waveguide conversion probe structure provided by the embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The impedance matching method of the microstrip-waveguide conversion probe provided by the embodiment of the present invention mainly includes the following process: first, according to the structure of the back-to-back microstrip-waveguide conversion probe (as shown in Figure 1), the size of the conversion probe is designed, so that Ensure that the impedance of the center point of the structure is the pure real part impedance, and the profile of the designed probe is shown in Figure 2; secondly, a section of microstrip line is placed in the middle of the back-to-back microstrip-waveguide conversion probe structure, and by transforming the section of microstrip The width of the line is simulated by computer to obtain the value of the pure real part impedance. The three-dimensional schematic diagram of this part is shown in Figure 3; finally, the obtained pure real part impedance is matched to 50 ohms through the 1/4 wavelength impedance transformation line, and through the The cross-sectional view of the probe and the matching circuit that has realized the impedance matching of the impedance transformation line is shown in Figure 4. The technical solutions provided by the embodiments of the present invention are described in detail below.

Referring to Fig. 5, an embodiment of the present invention provides a method for impedance matching of a microstrip-waveguide conversion probe, the method includes the following steps:

Step 101: According to the working frequency, refer to the international waveguide dimension standard, and select the appropriate standard square waveguide geometric dimension;

In practical applications, the appropriate standard square waveguide geometric dimensions can be selected by checking the international waveguide dimension standard table; the standard square waveguide geometric dimensions include the length and width of the square waveguide;

Step 102: According to the wavelength corresponding to the center point of the working frequency, determine that the probe in the square waveguide is located at 1/4 wavelength away from the short-circuit surface of the waveguide;

Step 103: using three-dimensional electromagnetic field simulation software to establish a back-to-back microstrip-waveguide conversion probe structure;

The back-to-back microstrip-waveguide conversion probe structure includes: two completely symmetrical rectangular square waveguides, two identical conversion probes, substrate and air, etc.; the two conversion probe structures are completely symmetrical, and using this symmetry When changing the size of the probe in structural design, while meeting the requirements of small standing wave and low loss in the working frequency band, it also ensures that the center point impedance of the symmetrical structure is a pure real part impedance;

Step 104: Optimally designing the probe length L and width W in the back-to-back microstrip-waveguide conversion probe structure;

The optimized probe can make it have good standing wave and insertion loss performance in the working frequency band. At this time, the impedance at the center point of the back-to-back microstrip-waveguide conversion probe structure, that is, the input impedance value of the probe has only the real part and There is no imaginary part, assuming that the real part impedance is Zin; the input impedance is pure real part impedance.

Step 105: placing a section of microstrip line in the middle of the back-to-back microstrip-waveguide conversion probe structure, changing the width of the microstrip line for computer simulation, and obtaining the input impedance of the conversion probe;

In practical applications, when the characteristic impedance of the microstrip line placed in the middle is the same as the pure real part input impedance of the above-mentioned conversion probe, the standing wave and the The inserted signal is consistent with the back-to-back microstrip-waveguide conversion probe structure without adding microstrip lines; according to this principle, computer simulation is carried out by changing the width of microstrip lines, and the simulation results are compared with the conversion probe without microstrip lines The simulation results of the structure are compared, and when the width of the microstrip line is Wmid, the two simulation results are consistent; then the characteristic impedance corresponding to the width of the microstrip line at this time is Wmid, which is the input impedance Zin of the conversion probe;

Step 106: Transform the input impedance of the back-to-back microstrip-waveguide conversion probe to 50 ohms by using a 1/4 wavelength impedance transformation line;

得到1/4波长阻抗变换线的特征阻抗Z_λ/4，进而计算出阻抗变换线的宽度WR；阻抗变换线用于将纯实部阻抗转换为后级电路所需要的阻抗。As shown in Figure 4, according to the formula

Obtain the characteristic impedance Z _λ/4 of the 1/4 wavelength impedance transformation line, and then calculate the width WR of the impedance transformation line; the impedance transformation line is used to convert the pure real part impedance into the impedance required by the subsequent stage circuit.

The impedance matching method of the microstrip-waveguide conversion probe provided by the embodiment of the present invention combines the design of the size of the conversion probe itself with the impedance calculation, that is, the impedance matching design is completed while designing the microstrip-waveguide conversion probe , it is very convenient to get the input impedance of the conversion probe, and then realize the matching circuit design. This method is simple in operation, convenient in process, simplifies the matching circuit, and improves the accuracy of impedance matching.

The impedance matching method of the microstrip-waveguide conversion probe provided by the embodiment of the present invention is simple and practical, and the module produced has a small insertion loss (-0.5dB) in the Ka band (as shown in Figure 6), and the standing wave is good (in a fairly wide The frequency band is less than -20dB) (as shown in Figure 7); it is connected with the post-stage power amplifier to achieve a good 50 ohm impedance matching, which fully meets the conversion from micro to waveguide and the requirements of impedance matching. In addition, the technical solutions provided by the embodiments of the present invention can also be applied to input impedance calculation and impedance matching design of any band microstrip-waveguide conversion structure.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (4)

1. the impedance matching methods of little band-waveguide transitions probe is characterized in that, said method comprises:

Steps A: according to little band-waveguide transitions probe structure back-to-back, design obtains the transition probe size;

Step B: in the middle of said little back-to-back band-waveguide transitions probe structure, place one section microstrip line;

Step C: the width of the said microstrip line of conversion carries out Computer Simulation, and with the simulation result contrast of simulation result with the transition probe structure that does not have said microstrip line; When said microstrip line during at a certain width; Its characteristic impedance is the same with said little back-to-back band-waveguide transitions probe structure central point impedance; This moment, simulation result was consistent with the simulation result of the transition probe structure that does not have said microstrip line, obtained the input impedance of said transition probe according to the width of said microstrip line at this moment;

Step D: utilize 1/4 wavelength impedance conversion line with said input impedance matching to 50 ohm.

2. the impedance matching methods of little band as claimed in claim 1-waveguide transitions probe; It is characterized in that; Said little back-to-back band-waveguide transitions probe structure is made up of two symmetrical fully transition probe structures, and said little back-to-back band-waveguide transitions probe structure central point impedance is pure real impedance.

3. the impedance matching methods of little band as claimed in claim 1-waveguide transitions probe is characterized in that said input impedance is pure real impedance.

4. the impedance matching methods of little band as claimed in claim 3-waveguide transitions probe is characterized in that, said impedance conversion line is used for converting said pure real impedance into late-class circuit needed impedance.

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