DE1065026B - Waveguide bridge circuit for microwaves - Google Patents

Description

GERMAN

The invention relates to a waveguide bridge circuit as a mixer or frequency converter for microwaves, in which for decoupling the microwaves are _supplied on the one hand as H i0 waves and on the other hand as Lech waves to two mixing diodes located in a waveguide.

Bridge circuits are used in a wide variety of ways in electrical engineering. They serve either in the Measurement technology for the comparative measurement of electrical quantities or they are used where two Circuits to be decoupled from one another work on the same line. These include hybrid circuits as well as arrangements for frequency mixing or multiplication.

Such bridge circuits are also known for the field of microwaves. These are no more built up from concentrated switching elements, but from corresponding line elements and under known as "magic ring", "magic T" or "magic Y". The application of the known It is well known that circuits for frequency mixing or conversion have the disadvantage that that these arrangements working with / l / 4-line elements are very bulky. Given the considerable space required by such a bridge circuit as a mixer, the diodes or the necessary connections are inevitably relatively far apart. This has the consequence that unfavorably long intermediate frequency lines result. aside from that prepares the adjustment to a different operating frequency or the implementation in the known circuits When changing diodes, there are considerable difficulties with regard to the lines to be adapted.

In a known arrangement, these disadvantages are avoided. The oscillator frequency in Form of Lecherwellen via a coaxial cable and the input frequency in the form of waveguide waves via A rectangular waveguide is fed to a mixing chamber which has two diodes connected in push-pull.

The resulting intermediate frequency is brought out symmetrically through a wall of the waveguide. With This arrangement allows a good decoupling of the receiving frequency from the neighboring oscillator frequency reach in compact form.

Furthermore, arrangements are known in which the input frequency via a waveguide and the oscillator frequency via a coaxial line to a common mixing room in different waveforms are fed. A special cavity resonator is provided as the mixing space. So much for these known arrangements, the diodes to achieve the highest possible output level in push-pull are switched, however, only a symmetrical intermediate frequency voltage can be obtained.

Waveguide bridge circuit
for microwaves

Applicant:

Standard electrical system Lorenz

Corporation,

Stuttgart-Zuffenhausen,

Hellmuth-Hirth-Str. 42

Dr.-Ing. Martin Müller, Pforzheim,
has been named as the inventor

In many cases, however, a symmetrical intermediate frequency voltage is neither desirable nor with Circuit difficulties connected. Therefore, with the invention, an arrangement with asymmetrical Intermediate frequency output created, which is also suitable for maximum frequencies, since it is used of coaxial lines is completely avoided. ; ■

The invention is characterized in that the waveguide extends partially in its longitudinal direction extending inner conductor and one perpendicular to this and to the transmission direction of the waveguide lying conductive transverse web, which has at least one side wall capacitive high frequency and is galvanically connected to the inner conductor and out of the waveguide through an opening in the side wall is led out, and that the outward via the. Crossbar connected connection point of the Diodes are used to connect an IF voltage asymmetrically to ground.

While the inserted inner conductor represents _{only a very low capacitive load for the H 10} waves occurring in the waveguide, on the other hand, transmission of the L waves beyond the end of the inner conductor is not possible because their fields cancel each other out there. It has been found that an attenuation of about 30 to 50 db is achieved without difficulty. In order to couple in and out the L waves propagating along the inner conductor between the adjacent waveguide walls like a coaxial line, is

909 627/287

proposed according to the invention that the other end of the introduced inner conductor by a coaxial Line transition is coupled to a second waveguide. ■ ■. · · ■

Such a coaxial line transition can be made, for example, in the continuation of the inner conductor through a central opening in an end wall of the first waveguide, through which the H ₁₀ waves, as is known, cannot pass. This end wall is expediently dimensioned for optimal adaptation of the H ₁₀ waves to the diodes. The inner conductor guided through this then penetrates in a known manner the interior space of the coupled second waveguide, which extends perpendicular to the waveguide of the bridge circuit and can thereby be excited by the L waves.

In order to optimally dimension the output of the bridge circuit for the L waves, it is suggested that that the inner conductor has an interruption that acts as a series capacitance for the purpose of adaptation, whose length can preferably be changed in that the at the coaxial line transition through the Interior of the second waveguide protruding part of the inner conductor, for example adjustable with a screw is.

The actual mixture of the two high frequencies or the implementation of a waveguide frequency with Using an oscillator frequency is made that in a known manner at the connection point of the two mixing diodes perpendicular to the transmission direction of the waveguide, a conductive transverse web is arranged. This establishes the connection of the common connection of the diodes with ground or with an intermediate frequency connection.

The basic circuit of this connection is made in a known manner so that the conductive Crossbar connects both side walls of the waveguide with each other so that the two diodes against each other and thus are connected in push-pull with respect to the inner conductor and that the two outer The ends of these diodes form a symmetrical intermediate frequency connection.

In a further development of the invention it is proposed that the conductive transverse web have only one side wall is connected capacitively in terms of high frequency and is continued through an opening to the outside that the now differently polarized diodes are both connected with their external connections to ground and that the connection point of the diodes connected to the outside via the crossbar as a connection of an asymmetrical, IF voltage lying against ground is used. As a result, the diodes appear to be parallel for the IF switched. It is advantageous to dimension the arrangement for the microwaves in the waveguide so that that the high-frequency capacitive connection of the conductive crossbar is dimensioned as a Λ / 4 resonance element is.

In order to combine the known advantages of the high IF resistance of the mixer, which can be achieved by connecting the diodes in series, with the advantages of an asymmetrical intermediate frequency connection, it is further proposed that this crossbar leading to the outside be dimensioned using two diodes connected against one another so that it is The additional capacitance arranged outside the waveguide is balanced with respect to the intermediate frequency and that the intermediate frequency connection is asymmetrically made from the outside via the two oppositely polarized diodes in such a way that the outer end of one diode is used as a connection and the outer end of the other Diode, however, with the waveguide wall at ground potential as a second connection which thus serves as an intermediate frequency which is symmetrical with respect to the mixer.
It is also proposed that the symmetrized transverse web closes galvanically via a choke that blocks the intermediate frequency through the DC voltage circuit provided for the diodes.

In order to achieve certain tolerances of the diodes or the

ίο balance circuit, it is advantageous that the common Direct current connection of the diodes to the tap of a potentiometer blocked for the IF which is used for direct current balancing of the operating points of the diodes.

Furthermore, this bridge circuit is improved by that for the high-frequency symmetry of the waveguide except after the one. Side wall leading crossbar a second crossbar is connected to the opposite side wall and that this is coupled to the junction of the diodes and to compensate for impedance differences of the two diodes is adjustable in its spatial position with the help of an insulated adjusting screw. The proposed according to the invention hollow

■ 25-wire bridge circuit can thus be used at any time upon coordination to a different frequency or when changing a diode for optimal operating behavior be readjusted, whereby the state set for the optimum performance changes only infrequently differs from that for optimal balancing.

The proposed bridge circuit, which is used to generate an intermediate frequency as well a corresponding frequency conversion of a microwave can be used with the help of an intermediate frequency, is also suitable as a frequency multiplier, whereby the waveguide serving as the output is dimensioned in such a way that that its cut-off frequency is greater than the basic frequency or those below the output frequency unwanted harmonics.

The invention is explained in more detail on the basis of exemplary embodiments with reference to the drawing:

1 shows the longitudinal section through a bridge circuit according to the invention;

FIGS. 2 and 3 show a cross section through the arrangement shown in FIG. 1 with an asymmetrical Intermediate frequency output.

In FIG. 1, a waveguide 1 of rectangular cross section is provided with an inner conductor 2. Only the L waves transmitted along this inner conductor are connected to a second waveguide 3 via a coaxial coupling piece 4. This coupling takes place on the one hand directly to the output or input and on the other hand in a known manner via a reflection at the adjustable Λ / 4 length of a short circuit 5 attached to the opposite end of the second waveguide 3. For better adaptation to ^1, the impedance of the diodes is at 6 a capacitive interruption of the inner conductor is provided,

6a their value by means of an adjusting screw on the outside of the waveguide 3 is tunable. At the other end of the inner conductor 2, two diodes 7 and 8 are connected. The resulting intermediate frequency is derived from points 9 and 10.

FIG. 2 shows a cross section through the arrangement shown in FIG. 1. As can be seen from this, lie both diodes for the waveguide shaft equally polarized in series. There is only one conductive crosspiece 15 towards a side wall, and connected to the waveguide in terms of high frequency as an A / 4 barrier.

Claims (10)

final capacity 16 is provided in a known manner. The intermediate frequency or direct current connection of the diodes is denoted by 14. The two diodes are connected in parallel for the intermediate frequency. As a result, the real part of the intermediate frequency impedance is only half as large as that of a single diode. This circuit can therefore be used particularly advantageously in connection with the low capacitance canceled in the IF line because of its low real resistance in those cases where a large bandwidth is desired. It is therefore suitable, for example, for an input mixer whose IF circuit is only attenuated by the diodes. Fig. 3 shows a further development of the invention. The diodes are connected against each other, so they work in push-pull, which is desirable for reasons of symmetry. However, there is only one diode on the intermediate frequency connection, which is blocked in terms of high frequency with a capacitance 19, while the other diode is connected to ground. The intermediate frequency is connected asymmetrically on the outside, but balanced with respect to the mixer arrangement. This is achieved in that a capacitor 21 is provided, the size of which corresponds to the capacitance of the transverse web indicated by dashed lines. Furthermore, the direct voltage is connected via a choke coil 22 which blocks the intermediate frequency. A. Potentiometer 23, which in turn is bridged for the intermediate frequency with the aid of a capacitor 24, allows the two diode operating points to be balanced. The inductance of the intermediate frequency circuit is denoted by 25. 3 also shows a second transverse web 26, similar to the transverse web 15, which is attached to the end of the opposite side wall of the waveguide. This second web is capacitively coupled to the connection point of the diodes in such a way that the arrangement also has a high-frequency effect. In order to also have certain impedance differences in the. To be able to compensate for diodes, an insulated adjusting screw 27 is arranged on this part of the waveguide. This serves to set the spatial position of the second transverse web in relation to the two diodes to an optimal symmetry value. Since the diodes for the intermediate frequency are connected in series in this arrangement, the effective impedance value is twice as large as that of a single diode. This circuit is therefore particularly suitable as an anode load of an IF output tube and as a sensitivity mixer in a grid base input circuit of the corresponding IF amplifier, in which, as is known, a high source resistance has a noise-reducing effect. The described exemplary embodiments of the invention can accordingly also be used for frequency multiplication. The particular advantage here is that in addition to the fundamental wave, the third harmonic can also be effectively suppressed. The suppression of the fundamental wave can be brought to any high value by appropriate selection of the cutoff frequency and the length of the output-related waveguide. P Λ T K N T Λ N S P R 0 C H E: 1. Waveguide bridge circuit as a mixer or frequency converter for microwaves, in which for decoupling the microwaves _{are supplied on the one hand as H 10} waves and on the other hand as Lecherwellen two mixing diodes lying in a waveguide, characterized in that the waveguide has a partially extending in its longitudinal direction Inner conductor and a conductive transverse web lying perpendicular to this and to the transmission direction of the waveguide, which is capacitively high-frequency-wise with at least one side wall and is galvanically connected to the inner conductor and is led out of the waveguide through an opening in the side wall, and that the outwardly via the transverse web The connected connection point of the diodes serves as a connection for an IF voltage which is asymmetrical to ground. 2. Bridge circuit according to claim 1, characterized in that the other end of the inserted inner conductor through a coaxial line transition is coupled to a second waveguide. 3. Bridge circuit according to claim 1, characterized in that the inner conductor for the purpose of adaptation has an interruption acting as a series capacitance, the length of which is preferably thereby it is changeable that the second at the coaxial line transition through the interior Waveguide protruding part of the inner conductor is adjustable for example with a screw. 4. Bridge circuit according to claim 1, characterized in that! That the conductive transverse web only with a side wall capacitively connected in terms of high frequency and through an opening to the outside is continued and connected through both diodes with their external connections to ground and with respect to of the ground connection are polarized differently. 5. Bridge circuit according to claim 1, characterized in that the high-frequency capacitive Connection of the conductive transverse web is dimensioned as a / t / 4 resonance member. 6. Bridge circuit according to claim 1, characterized in that the transverse web by a Additional capacitance arranged outside the waveguide is balanced with respect to the intermediate frequency and that the intermediate frequency connection is unbalanced from the outside across the two with respect to the web in the same direction polarized diodes is made in such a way that the outer end of one diode as a connection, the outer end of the other diode but with the on Ground potential lying waveguide wall as a second connection of the thus with respect to the mixer symmetrical intermediate frequency is used. 7. Bridge circuit according to claim 6, characterized in that the symmetrized transverse web galvanically via a choke that blocks the intermediate frequency to the one provided for the diodes DC circuit closes. 8. Bridge circuit according to claim 7, characterized in that the common direct current connection the diodes on the. Tapping of a potentiometer blocked for the IF, which is used for DC symmetrization of the working points of the diodes is used. 9. Bridge circuit according to claim 1, characterized in that for high frequency Balancing of the waveguide except for the transverse web leading to one side wall second transverse web is connected to the opposite side wall and that this second crossbar is now preferably capacitively coupled to the junction of the diodes and to compensate for impedance differences of the two diodes is adjustable in its spatial position with the help of an insulated adjusting screw. 10. Bridge circuit according to one of the preceding claims, characterized by the Use as a frequency multiplier and in that the waveguide serving as an output so is dimensioned that its cut-off frequency is greater than the base frequency or below the output output frequency lying unwanted harmonics. Considered publications: German Patent Specifications No. 860 504, 887 544, 556; French Patent No. 890 885; U.S. Patent Nos. 2,561,417, 2,576,481. 1 sheet of drawings © 909 '627/287 9.59