CN103579729B - A kind of spaceborne high-frequency microstrip is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss - Google Patents

Abstract

A space-borne high-frequency microstrip to waveguide broadband low insertion loss vertical conversion circuit belongs to microwave and millimeter wave transition conversion technology between waveguide microstrips. The conversion circuit includes sequentially connected microstrip lines, open-circuit matching stub ends, interconnected gold strips between the ends of the microstrip coaxial line, coaxial glass insulators with flat ends and sintered in the cavity, welded on the insulator end The stepped probe of the head. The invention realizes the mode transition conversion of the electromagnetic field between the main modes of the rectangular waveguide and the microstrip line, completes the transmission of electromagnetic signals between the rectangular waveguide and the microstrip line, and has the advantages of ingenious design, compact structure, sealability, and the ability to switch transmission directions. Co-directional design, small insertion loss, wide frequency band, and good standing wave characteristics.

Description

A Spaceborne High Frequency Microstrip to Waveguide Broadband Low Insertion Loss Vertical Conversion Circuit

technical field

The invention relates to a vertical conversion circuit for a microstrip rectangular waveguide, specifically a circuit for converting a microstrip to a rectangular waveguide through a vertical coaxial structure, and is mainly used in high-frequency receivers, transmitters, antennas, etc. The field of signal transmission form conversion.

Background technique

Microwave-to-waveguide conversion is a commonly used microwave circuit conversion structure, and many types have been developed. From the perspective of architecture type, it includes the direct transition from microstrip to waveguide, and the transition from microstrip to waveguide after coaxial transformation; from the perspective of transmission direction, it includes microstrip and waveguide transmission direction perpendicular to it, and microstrip and waveguide transmission direction parallel to each other. From the perspective of sealing direction, it includes transitions that can achieve full airtightness and non-airtight transitions, but the general form of micro-to-waveguide conversion is difficult to simultaneously take into account airtightness, transmission isotropy, and Broadband low insertion loss characteristics.

Contents of the invention

The technical problem of the present invention is to overcome the deficiencies of the prior art, and provide a vertical conversion circuit with low insertion loss from the space-borne high-frequency microstrip to the waveguide broadband, which has the same direction transmission, airtightness, wide frequency band, low insertion loss, and reliability Advantages of high sex.

Technical solution of the present invention: a space-borne high-frequency microstrip to waveguide broadband low insertion loss vertical conversion circuit, which is characterized in that it includes: microstrip line (1), open-circuit matching stub (2), interconnection gold strip (3) , coaxial glass insulator (4), silver-plated aluminum stepped probe (5), dielectric substrate (6), cylindrical through cavity (7), waveguide cavity (8) and microstrip cavity (9) ; Wherein the microstrip line (1) and the open-circuit matching branch (2) are both located on the dielectric substrate (6) and connected to each other, and the dielectric substrate (6) is bonded to the inner surface of the microstrip cavity (9) , the coaxial glass insulator (4) is sintered in the microstrip cavity (9), the upper end and the lower end of the lead of the glass insulator (4) are exposed outside the cavity, and the distance between the upper end of the insulator (4) and the dielectric substrate (6) must be ensured There is a gap between them, the upper end of the insulator (4) is crimped with the open-circuit matching stub (2) through the interconnection gold strip (3), and the silver-plated aluminum stepped probe (5) is welded on the lower end of the glass insulator (4). There must be a gap between the lower end surfaces of the insulator (4), and the center of the probe (5) is located at half of the narrow side of the waveguide cavity (8), as indicated by a/2 in Figure 2, and the cylindrical through cavity (7) It is opened on the waveguide cavity (8) to extend into the silver-plated aluminum probe (5). The distance between the center of the through cavity (7) and the bottom surface of the waveguide is a certain value, as indicated by e in Figure 2, and the dimension is approximately corresponding to 1/4 of the transmitted signal wavelength.

The height of the dielectric substrate (6) after bonding should be consistent with the height of the upper end of the glass insulator (4), so as to ensure that the two crimping points of the interconnected gold strip (3) (the upper end of the glass insulator (4) matches the open circuit Branches (2)) are at the same height to achieve the shortest length of the crimped interconnection gold strip (3) and reduce the discontinuity of electromagnetic field transmission. The interconnection gold strip should be arched to improve the anti-vibration reliability of the interconnection.

The microstrip line (1) and the open-circuit matching stub end (2) are both located on the same dielectric substrate, and the open-circuit matching stub (2) is mainly used to synthesize the inductance characteristics introduced by the interconnection gold strip (3), thereby realizing coaxial to the impedance matching between the microstrip.

The shortest distance between the dielectric substrate (6) and the upper end of the glass insulator (4) should be controlled to 0.1mm, as marked by d in Figure 2, which can ensure that the crimping span of the interconnection gold strip (3) is small and the path is short, and the insulator (4) The upper end is not short-circuited with the ground on the bottom surface of the dielectric substrate (6).

The glass insulator (4) is sintered in the microstrip cavity by using solder, which can realize gas isolation between the microstrip cavity (9) and the waveguide cavity (8). The lower end of the glass insulator (4) is located in the waveguide cavity (8) cylindrical through hole (7), and the diameter of the cylindrical through hole (7) is larger than the diameter of the probe (5), ensuring that the welded probe can penetrate into the waveguide cavity body. An equivalent capacitance is formed between the cylindrical through hole (7) and the probe (5), which participates in the matching. Adjusting its size can further broaden the bandwidth used. The distance between the cylindrical through hole (7) and the waveguide cavity (8) The distance between the bottom surface of the rectangular waveguide is λ/4 (λ is the wavelength corresponding to the transmission signal frequency), as indicated by e in Figure 2 .

The aluminum silver-plated probe (5) has a stepped shape, which realizes the step change in impedance between the waveguide and the coaxial. Compared with the straight type probe, it can expand the bandwidth of use. After welding, the upper end of the probe (5) is separated from the glass insulator ( 4) The lower end surface should be 0.1mm, as indicated by h in Figure 2. On the one hand, it can prevent the center of gravity of the probe from moving down and the vibration radius is too large. On the other hand, a shorter distance can also reduce the discontinuity introduced by the end lead wire . The inside of the probe (5) contains welding holes A and through holes B as shown in Figure 2, which enhance the silver plating quality and soldering reliability of the probe.

Due to the coaxial interconnection, the TEM mode of coaxial transmission determines that the transmission direction of the microstrip cavity and the waveguide cavity can be set arbitrarily. This design adopts the same direction design, which is the mainstream idea of microwave modular products at present, as shown in the figure 1, the transmission direction of the signal along the microstrip line (1) is consistent with the transmission direction of the signal in the rectangular waveguide in the waveguide cavity (8).

Realization principle of the present invention:

The realization goal of the present invention is to convert and transmit signals from a microstrip line to a waveguide. The specific implementation principle is, as shown in Figure 1, first introduce the signal into the coaxial insulator (4) through the microstrip line (1) and the open circuit matching stub (2) and the interconnection crimping gold strip (3), and then through the coaxial glass The insulator (4) is introduced into the stepped probe (5) welded on the lower end, and the probe (5) is placed in the waveguide cavity (8) where the magnetic field of the main mode TE10 mode of the rectangular waveguide is the strongest, generally the narrow side of the waveguide half of , as indicated by a/2 in Figure 2, and λ/4 from the bottom of the waveguide (corresponding to the wavelength of the transmission frequency), as indicated by e in Figure 2, at this time the reflection coefficient is about 1, that is, the signal passes through the bottom of the waveguide completely Reflected back to the position of the end face of the probe (5), the reflected wave and the incident wave are superimposed in the same phase at the probe, and the energy transmitted to the conversion point is strengthened, so as much as possible signal coupling into the waveguide cavity can be ensured, thereby obtaining a lower Insertion loss and better standing wave. The open-circuit matching stub is mainly to suppress the transmission discontinuity introduced by the interconnection gold strip (3) during transmission, so as to ensure that the signal can be completely imported from the microstrip line (1) to the coaxial insulator (4). The stepped probe The spatial coupling with the rectangular waveguide cavity completes the broadband matching of the coaxial 50Ω impedance to the rectangular waveguide wave impedance, realizing broadband conversion transmission.

The advantage of the present invention compared with prior art is:

(1) Compared with the conversion of microstrip to waveguide, and the vertical conversion transmission direction of the conversion of microstrip-horizontal coaxial-waveguide, the present invention adopts the vertical coaxial structure to realize the conversion of microstrip to waveguide, which can realize the same direction Transmission, can be more compact in the whole star layout.

(2) Compared with the conversion circuit described in the patent No.: CN101752631A, "Rectangular waveguide and microstrip transition conversion circuit based on magnetic coupling principle", this design can realize the same direction transmission and good air tightness , which is more reliable for on-board products built with bare chips.

(3) Compared with the existing conversion circuit built by soldering, the gold-belt interconnection soft lapping technology is adopted, which has higher anti-vibration performance and is more suitable for spaceborne use.

(4) The use of stepped probes and open-circuit matching stubs expands the bandwidth used and reduces insertion loss, and the probes contain soldering holes and through holes (exporting bubbles generated by soldering), as marked by A and B in Figure 2 , can improve the quality of silver plating and soldering, and further improve the reliability of the product.

In short, the present invention adopts a vertical coaxial structure to realize the transition from micro to rectangular waveguide, and has the characteristics of co-directional transmission, air tightness, wide frequency band, low insertion loss and high reliability.

Description of drawings

Fig. 1 is a schematic circuit diagram of the present invention;

Fig. 2 is a partial detail diagram of the circuit of the present invention;

FIG. 3 is a schematic diagram of a three-dimensional structure of a waveguide cavity in an embodiment of the present invention;

4 is a schematic diagram of a dielectric substrate containing a pair of back-to-back transition conversion circuits in an embodiment of the present invention;

Fig. 5 is a top view after the dielectric substrate and the microstrip cavity are assembled in one embodiment of the present invention;

6 is a schematic side view of the assembly of the microstrip cavity and the waveguide cavity in an embodiment of the present invention;

Fig. 7 is a schematic front view of the assembly of the microstrip cavity and the waveguide cavity in an embodiment of the present invention;

Fig. 8 is the S21 simulation result figure in Ka frequency band in one embodiment of the present invention;

Fig. 9 is the S11 simulation result figure in Ka frequency band in one embodiment of the present invention;

Fig. 10 is the S21 measured result figure of sample in Ka frequency band in one embodiment of the present invention;

Fig. 11 is a schematic diagram of the S11 measured results of samples in the Ka frequency band in an embodiment of the present invention;

detailed description

As shown in Figure 1, a spaceborne high-frequency microstrip to waveguide broadband low insertion loss vertical conversion circuit includes: microstrip line 1, open circuit matching stub 2, interconnection gold strip 3, coaxial glass insulator 4, silver-plated aluminum Stepped probe 5, dielectric substrate 6, cylindrical through cavity 7, waveguide cavity 8 and microstrip cavity 9; wherein the microstrip line 1 and the open-circuit matching stub 2 are both located on the dielectric substrate 6, and mutually connection, the dielectric substrate 6 is bonded on the inner surface of the microstrip cavity 9, the coaxial glass insulator 4 is sintered in the microstrip cavity 9, the upper end and the lower end of the lead of the coaxial insulator 4 are exposed outside the cavity, through the interconnection gold Tape 3 crimps the upper end of the insulator 4 with the open-circuit matching stub 2, the silver-plated aluminum stepped probe 5 is welded on the lower end of the insulator 4, and the cylindrical through cavity 7 is opened on the waveguide cavity 8 to extend into the Silver plated aluminum probe 5.

The height of the dielectric substrate 6 after bonding should be consistent with the height of the upper end of the glass insulator 4, as shown in FIG. are at the same height for the shortest crimp length possible.

The crimping shape of the interconnected gold belt 3 should be an arc, as shown in Figure 2. The arch height should be controlled between 0.05 and 0.1 mm, and the span between the two crimping points should be kept within 0.3 mm, which is relatively short. The crimping length is about 0.4-0.5 mm, and the interconnection gold ribbon 3 is divided into two types: rectangle and sector, as indicated by C and D in FIG. 2 .

The shortest distance between the dielectric substrate 6 and the end of the glass insulator 4 should be controlled to be 0.1 mm, specifically as indicated by d in FIG. The transmission discontinuity introduced by the gold strip 3 can also ensure that the upper end of the insulator 4 is not short-circuited with a large area on the back of the dielectric substrate 6, causing a mismatch.

The diameter of the cylindrical through cavity 7 should be greater than the diameter of the probe 5 to ensure that the probe 5 welded on the end of the insulator can penetrate into the waveguide cavity 8, and the distance between the center of the cylindrical through cavity 7 and the bottom surface of the rectangular waveguide λ/4 corresponds to the wavelength of the transmission frequency, as indicated by e in Figure 2.

The distance between the welded probe 5 and the lower end surface of the insulator 4 is 0.1 mm, as indicated by h in Figure 2, to ensure that the upper end surface of the probe 5 is as close as possible to the lower end surface of the insulator 4, reducing the discontinuity of electrical transmission and preventing the probe from 5 is short-circuited with the end face of the microstrip cavity 9, resulting in a mismatch. The center of the probe 5 is located at half of the narrow side of the rectangular waveguide of the waveguide cavity 8, as indicated by a/2 in FIG. 2 .

The probe 5 is in the shape of a ladder and contains welding holes for terminal leads and through holes, as indicated by A and B in Figure 2, to ensure that the silver layer can smoothly flow through the inner wall of the hole when the probe 5 is silver-plated, and Bubbles can be effectively removed during welding, thereby improving welding quality.

The transmission directions of the microstrip cavity 9 and the waveguide cavity 8 are designed in the same direction. As shown in FIG. 1 , the transmission direction of the signal on the microstrip line 1 is consistent with that of the rectangular waveguide in the cavity cavity 8 .

The working process of the present invention: the present invention is a passive circuit, so it does not distinguish between static and dynamic operating modes. Its signal transmission path is that the signal is first transmitted from the microstrip cavity 9, and passes through the microstrip line positioned on the dielectric substrate 6. After 1 is matched with the branch 2 of the open circuit, the signal is introduced into the upper end of the coaxial glass insulator 4 by the interconnection gold strip 3, and then transmitted to the silver-plated stepped aluminum probe inserted into the cylindrical through hole 7 through the coaxial part of the insulator 4. On the needle 5, it is coupled into the waveguide cavity 8 by the probe 5, and finally output through the waveguide port.

In the process of signal conversion and transmission, the open-circuit matching stub 2 comprehensively removes the discontinuity introduced by the interconnection gold strip 3, and realizes the continuous transmission of 50Ω between the coaxial lines of the microstrip line 1 and the insulator 4, and the stepped probe 5 and the waveguide cavity 8 The coupling of the rectangular waveguide realizes the step transformation from the 50Ω coaxial line of the insulator 4 to the wave impedance, thereby ensuring the matching transmission of the microwave signal.

As shown in Figure 1, the conversion structure includes a microstrip cavity 9 bonded to a dielectric substrate 6, a microstrip line 1 located on the dielectric substrate 6, an open circuit matching stub end 2, and a microstrip coaxial end The interconnected gold strip 3 between the heads, the coaxial glass insulator 4 sintered in the structural part, and the stepped aluminum silver-plated probe that passes through the cylindrical through hole 7 on the waveguide cavity 8 and is welded to the lower end of the insulator 4 pin 5.

Example

For the convenience of testing, at first the two identical conversion circuits of the present invention are symmetrically arranged on the same dielectric substrate 6, and the microstrip lines 1 in the two conversion circuits are connected so that the two conversion circuits are connected as shown in the figure 4, and then prepare the microstrip cavity with two insulators sintered, and the waveguide cavity containing two cylindrical through cavities (for probe penetration) and two rectangular waveguides as shown in Fig. 3 (all surfaces of the cavity are plated silver), bond the dielectric substrate shown in Figure 4 to the microstrip cavity with conductive adhesive, ensure that the distance between the substrate and the two The belt interconnects the open-circuit matching branch and the insulator terminal. The gold belt interconnection path is the shortest, the arch height is between 0.05mm and 0.1mm, and the span is within 0.3mm. Weld the stepped probe at the lower end of the insulator to ensure that the distance between the end face of the probe and the end face of the insulator is kept at 0.1mm. After welding, assemble the microstrip cavity into the waveguide cavity, and fasten the two cavities with screws, as shown in Figure 6 and Figure 7. There are two waveguide interfaces externally, which are easy to test.

Next, according to the above theory, the simulation optimization design is carried out on the computer first, then the physical samples are processed according to the optimization design, and finally the samples are tested.

The simulation calculation software uses HFSS14 microwave simulation software. The dielectric substrate is made of A493 ceramic sheet with a dielectric constant of 9.9 and a thickness of 0.38mm. The thickness of the gold plating is 2-3um. Line port, width ≥ 0.38mm, gold ribbon arch height set between 0.05-0.1mm, span between 0.25-0.3mm, rectangular waveguide adopts BJ260 size.

The above case was simulated in the frequency range of 18-34GHz. The simulation results are shown in Figure 8 and Figure 9. The return loss of 22GHz-31GHz is better than -20dB, and the insertion loss is better than 0.1dB. According to the optimization results, the The corresponding design dimensions were processed for the corresponding samples, and the Agilent E8363C was used to test the samples. The test results are shown in Figure 10. It can be seen that the test results are basically the same as the simulation results. The insertion loss is 1.1dB, and the test wave is deducted. dB loss, the insertion loss of the unilateral conversion circuit is better than 0.3dB, as shown in Figure 11, the return loss is better than -15dB at 21.5-28GHz. This proves that the present invention is not only feasible, but also has achieved or even surpassed the prior art in implementation effect. Therefore, the present invention is not only a brand-new choice in the engineering design of the transition conversion between the rectangular waveguide and the microstrip line in the microwave and millimeter wave bands, but also has compact structure, reliable performance, can be transmitted in the same direction, can be airtight, has wide bandwidth and low insertion loss. Low, with high utilization value.

Claims (8)

1. a kind of spaceborne high-frequency microstrip is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss, it is characterised in that including：Microstrip line (1), Open circuit matching minor matters (2), interconnection gold ribbon (3), coaxial glass insulator (4), probe (5), dielectric substrate (6), cylindrical cavity (7), wave-guide cavity wave (8) and micro-strip cavity (9), wave-guide cavity wave (8) include wave-guide cavity wave (8) wall, wave-guide cavity wave (8) cavity, micro- Attached cavity (9) includes micro-strip cavity (9) wall, micro-strip cavity (9) cavity, and coaxial glass insulator (4) is by insulated part and insertion Lead to insulated part is constituted；Wherein microstrip line (1) matches minor matters (2) both of which with open circuit on dielectric substrate (6), and It is connected with each other, dielectric substrate (6) is adhered on micro-strip cavity (9) wall inner surface, and coaxial glass insulator (4) is sintered in micro-strip chamber In body (9) wall, realize on the gas barrier between micro-strip cavity (9) and wave-guide cavity wave (8), coaxial glass insulator (4) lead Termination is stretched into micro-strip cavity (9) cavity, and coaxial glass insulator (4) lead lower end is stretched into wave-guide cavity wave (8) cavity, together There are gap, coaxial glass insulator (4) lead upper end between axle glass insulator (4) lead upper end and medium substrate (6) Crimped with open circuit matching minor matters (2) by interconnecting gold ribbon (3), probe (5) is welded on coaxial glass insulator (4) lead lower end On, gap is left between the lower surface of the insulated part of coaxial glass insulator (4), the remote coaxial glass of probe (5) is exhausted The end face of edge (4) insulated part is located at the half position on wave-guide cavity wave (8) narrow side of rectangular waveguide, and the narrow side is and probe (5) the parallel side of bearing of trend, cylindrical cavity (7) is opened on wave-guide cavity wave (8) wall, and to stretch into probe (5), cylinder is logical Equivalent electric capacity is formd between chamber (7) and probe (5)；The dielectric substrate (6) and coaxial glass glass insulator (4) lead The minimum distance of upper end be 0.1mm, it is ensured that interconnection gold ribbon (3) path it is short, coaxial glass insulator (4) lead upper end not with The short circuit in large area at dielectric substrate (6) back side.

2. spaceborne high-frequency microstrip according to claim 1 is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss, it is characterised in that： Height after dielectric substrate (6) bonding should be highly consistent with coaxial glass insulator (4) lead upper end, to ensure (3) two crimping points of interconnection gold ribbon are on sustained height, and this two crimping points are separately positioned on coaxial glass insulator (4) and drawn Line upper end, open circuit matching minor matters (2), realize that the length of crimping interconnection gold ribbon (3) is most short.

3. spaceborne high-frequency microstrip according to claim 1 is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss, it is characterised in that： Interconnection gold ribbon (3) crimping is shaped as camber line, and it is short that the control of sagitta and span should meet path, antivibration.

4. spaceborne high-frequency microstrip according to claim 1 is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss, it is characterised in that： The diameter of the cylindrical cavity (7) should be greater than the diameter of probe (5), it is ensured that probe (5), can deep enough wave-guide cavity wave (8) sky In chamber, cylindrical cavity (7) centre-to-centre spacing guide floor is the wavelength that λ/4, λ is correspondence frequency transmission signal.

5. spaceborne high-frequency microstrip according to claim 1 is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss, it is characterised in that The distance of the insulated part of the probe (5) away from coaxial glass insulator (4) is 0.1mm, it is ensured that probe (5) is close as far as possible The lower surface of the insulated part of coaxial glass insulator (4), reduces electrical transmission discontinuity, while preventing probe (5) and micro-strip Cavity (9) wall end face short circuit.

6. spaceborne high-frequency microstrip is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss according to claim 1, it is characterised in that：Institute State probe (5) stepped for silver-plated aluminum, include termination lead welding hole (A), and through hole (B), it is ensured that probe (5) it is silver-plated And welding quality.

7. spaceborne high-frequency microstrip is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss according to claim 1, it is characterised in that：Institute The transmission direction for stating micro-strip cavity (9) and wave-guide cavity wave (8) is design in the same direction, and signal is along microstrip line (1) transmission direction, with signal The transmission direction of rectangular waveguide in wave-guide cavity wave (8) is consistent.

8. spaceborne high-frequency microstrip is to the vertical change-over circuit of waveguide broad-band filter with low insertion loss according to claim 1, it is characterised in that：Institute It is rectangle or sector to state interconnection gold ribbon (3).