DE2616987A1 - Microwave stripline junction for waveguides - uses short coaxial intermediate line arranged between stripline and square, round or ridged waveguide - Google Patents

Abstract

Microwave stripline junction onto other waveguides, such as for example, coaxial lines, square, round and ridged waveguides aims at high mechanical stability of the frame mounting, together with improvements to the strip line junction itself. To these ends a short coaxial intermediate line is arranged between the microwave strip line and the waveguide. The inner conductor of the intermediate line has a flat contack tongue lying symmetrical or asymmetrical to the intermediate lines axis, on the side adjacent to the microwave stripline. More specif. the contact tongue is made of a very flexible electrically conductive material and a conductive connection to the microwave stripline is made as a contact spring.

Description

Microstrip line transition to other waveguides

The invention relates to a microstrip line junction other waveguides, e.g. Coaxial conductors, rectangular, round or ridge waveguides.

Need planar integrated microwave circuits in the so-called microstrip technology for applications in microwave systems very often inputs and outputs for HF signals in conventional line types such as coaxial line or waveguide to different Connect components such as oscillators, antennas and entire subsystems with one another to be able to. The between resulting from the different types of cables The interface must be bridged by a low-reflection line transition.

Microstrip coaxial line transitions where the circuit is substrate is installed in a closed metallic frame, which is also used for Used to accommodate screw-in coaxial connectors are known. The ground contact between Micro strip circuit and the outer conductor of the coaxial line runs here from the metallized underside of the circuit substrate over the metallic frame to Coaxial connector, the end of the coaxial inner conductor protruding into the frame represents the contact can be improved by soldering or conductive bonding.

Transitions with a special gas-tight screw-in coaxial connector, in which the inner conductor is fixed by a melted glass ring and also is centered by the usual Teflon bushings are known. The closed one Frame then allows a relatively simple hermetic sealing of the substrate to the Outside space. In the contact area between the inner conductor and the microstrip conductor, the The permanent contact mentioned above is produced by soldering or gluing.

A disadvantage of these transitions is that mechanical loads of the inner conductor when screwing a coaxial cable directly to the connector Contact point.

Similar loads on the contact point can be caused by thermal expansion arise at the plug. There is therefore a risk of the soldering tearing open or gluing at the contact point.

At signal frequencies above 10 GHz, the standing wave ratio increases a junction with a round coaxial inner conductor located directly on the microstripple ter strong too. A well-known method is the standing wave ratio at high frequencies to improve is that the coaxial inner conductor in the overlap area with the microstrip line is arranged symmetrically or asymmetrically to its axis Has flat contact tongue.

With the screw-in coaxial connectors, which have the advantage of a provide good ground contact and a hermetic seal, but the improvement of the standing wave ratio through a flat contact tongue at the transition possible if the circuit substrate is only inserted after the plug has been screwed into the Holding frame can be mounted. In addition, there is an inherently undesirable separation of the substrate holding frame required. Around a multi-part substrate holding frame To avoid this, screw-on coaxial plugs with contact tabs are usually used used, which however has the disadvantage of a lower RF shielding due to the am Show the edge of the substrate holding frame located ground contact and where a hermetic seal is more difficult to achieve.

The object of the invention is to improve the microstrip transition and the disadvantages mentioned while maintaining the mechanically very stable closed Avoid frame mounts as much as possible. This problem is solved in that a short coaxial intermediate line between the microstrip line and the corrugated conductor is arranged, the inner conductor of which is symmetrical or asymmetrical to the microstrip side lying on its axis Has flat contact tongue. Through this a significantly low standing wave ratio can be achieved even at very high frequencies achieve, and the contact point to the microstrip line is mechanically relieved.

The drawing shows exemplary embodiments. FIG. 1a shows schematically a longitudinal section and FIG. 1b schematically shows a cross section through a microstrip transition 2 shows a microstrip junction schematically in longitudinal section with a sealed one FIG. 3 schematically shows a microstrip waveguide transition, FIG. 4 shows a coaxial connector schematic section according to FIG. 3.

Between the one according to FIGS. 1a and b mounted on a substrate 1 Microstrip line 5 and the screw-in coaxial connector in which the inner conductor 4 is centered by a standard Teflon bushing 7, becomes a short additional one coaxial line piece 4 'inserted, which has a contact tongue 10 and the before screwing the coaxial connector into the substrate holder 2. The contact tongue 10 can be produced by milling off the inner conductor 4 as well as by soldering in a specially shaped contact spring made of a very elastic one Material, such as spring bronze, in a slot provided for this purpose in the inner conductor. In this way, a pressure contact can be generated in area 8, so that here soldering or conductive bonding can be dispensed with. The reference plane of the Kontalstzunge 10 can be symmetrical or asymmetrical about the center line 9 of the coaxial line 4, the S * ehwelleverhEltnis can thereby with different thicknesses of the substrate 1 of the transition can be minimized and a standard frame for different substrate thicknesses be used.

Fig. 2 shows an embodiment with a soldered contact spring 10 '. The contact of the intermediate coaxial line 11 with the coaxial plug 3 'can thereby in the same way as between two coaxial connectors with a single or multiple slotted hole 12, which when screwing in the coaxial connector 3 'resiliently receives the inner conductor 13. The inner conductor 13 is melted down by a Glass ring 6 fixed and also centered by a Teflon bush 7.

Experimental studies have shown that the line transition up to the cutoff frequency of the first Holle conductor mode in the coaxial system with a standing wave ratio S <1.2 can be realized. This value closes the usual for coaxial connectors Standing wave ratio S = 1.02 + 0.005f, where f is the frequency in GHz. With the standardized 3.5 mm coaxial plugs (SItA), this cut-off frequency is 25.5 GHz.

Miniaturized coaxial connector with a cutoff frequency of the first Waveguide modes at e.g. 40 GHz show an increased scatter with increasing frequency the increasing standing wave ratio; therefore it is often convenient for Signal frequencies above 25 GHz a waveguide feed to the Use microstrip circuit. The task often arises after a microstrip waveguide transition even at lower frequencies. This can generally be done in a similar way to described microstrip coaxial transition can be solved. The coaxial one is used here Intermediate piece 11 as a transition line between microstrip line and waveguide. The coaxial intermediate line is dimensioned so that the cutoff frequency the first coaxial waveguide mode above the unique transmission band of the connecting waveguide lies. The open end of the intermediate coaxial line is immersed into the waveguide and acts there as an antenna.

Another embodiment of a microstrip waveguide transition is shown in perspective in FIG. 3 and as a sectional drawing in FIG. The waveguide section 14 is integrated into the substrate holding frame 2 '. With an experimental too defining, specially shaped cylindrical or spherical or conical Antenna attachment 15, which is soldered onto the open end of the coaxial intermediate line can be, the standing wave ratio S of the line transition according to Fig. 3 and 4 with the relatively low value S <1.15 over an entire waveguide band realize. With a symmetrical arrangement of the coaxial intermediate line 11 the waveguide gate can be moved to the direction of propagation Z of the waveguide 14 the short circuit plate 16 either to the top or bottom of the substrate holding frame 2 'showing the thickness of the Substrate holding frame with integrated Waveguide section equal to twice the length of the optimal distance L between Coaxial conductor center line and waveguide short-circuit plane. With the tuning screw 17, the frequency dependence of the standing wave ratio can be reduced in the usual way will.

According to the same principle, microstrip junctions can also be used for round and ridge waveguides.

Patent claims:

Claims (6)

Claims: t14 microstrip line transition to other waveguides, e.g. coaxial conductors, rectangular, round or ridge waveguides, characterized that between the microstrip line and the waveguide a short coaxial intermediate line is arranged, the inner conductor of which is symmetrical or asymmetrical to the microstrip side has flat contact tongue lying on its axis. 2. microstrip line junction according to claim 1, characterized in that that the contact tongue consists of a very elastic, electrically conductive material and creates a conductive connection to the microstrip line as a contact spring. 3. microstrip line transition according to claim 1 and 2, characterized in that that the coaxial intermediate line has a jump in diameter, the diameter of the coaxial inner conductor on the microstrip side is about the same as the width of the Microstrip strips). 4. microstrip line transition according to claim 1 to 3, characterized in that that the inner conductor of the coaxial intermediate line at its open end one axially has directed bore with several slots, which are used for resilient reception of the Inner conductor of a coaxial plug or a coaxial line is used. 5. microstrip line transition according to claim 1 to 3, characterized in that that the coaxial intermediate line is immersed in a hollow line and there an antenna forms. 6. microstrip line transition according to claim 1 to 3 and 5, characterized characterized in that a waveguide piece is integrated into the microstrip substrate holding frame and the thickness of the substrate holding frame is equal to twice the length of the optimum Distance between the axis of the antenna and the waveguide short-circuit plane selected and a short-circuit plate is attached to one of the two open waveguide outputs is.