US2925566A - Broad band balun transformer - Google Patents

Description

Feb. 16, 1960 H. JASIK BROAD BAND BALUN TRANSFORMER Filed June 26, 1957 e)T-Q IN V EN TOR.

BY pr/Ja %%z;

Unie dttes Patnt nRoAn BAND BALUN TRANSFORMER Henry Jasik, Flushing, N.Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application June 26, 1957, Serial No. 668,274

1 Claim. (Cl. 333-26) This invention relates to a transformer device in a particular circuit using high frequencies.

The object of this invention relates to a system of impedance matching in a particular circuit for maximum power transfer.

A further object of this invention is a particular design of a balun and transformer which occupies a much reduced space than formerly occupied.

A still further object of this invention is a system of feeding a high impedance line from a low impedance line over a wide frequency range without introducing an appreciable standing wave ratio (SWR).

These and other objects will be readily apparent to those skilled in the art from an examination of the following description and enclosed sheet of drawings wherein,

Figure 1 illustrates the basic balun and transformer,

Figure 2 illustrates the balun and transformer as in Figure 1 but with the input and output on the same side,

Figure 3 illustrates the transformer system together with a shielding box, and

Figure 4 illustrates the transformer system wherein the balun conductors are coiled for high impedance.

Referring to Figure 1, the balun consists of an unbalanced coaxial input comprising an outer conductor 1 and a concentric inner conductor 2; paralleling the conductors is a balanced line comprising a conductor 3 shunted to the outer conductor 1 by a shunt 4.

On the opposite side of the balun, a coaxial conductor having an outer conductor 5 and a concentric inner conductor 6 is paralleled by a similar coaxial line having an outer conductor '7 and an inner conductor 8. The two outer conductors are joined together by a connector 15. The inner conductors 6 and 8 are connected to a load 14. The right hand portion of the circuit forms a high impedance balanced load; the balun structure in the system is of low impedance with the high to low impedance ratio being of the order of 4 to 1.

The cross connections are as follows: a lead 13 from the inner conductor 2 is joined to conductor 3; lead 12 joins the outer conductors 1, 5; lead 9 connects conductors 3, 7; lead 11 connects conductors 1, 8; and lead connects conductors 3 and 6.

By means of the cross connection shown, the high impedance is reduced to a low impedance and, in the instant values used, from 200 ohms to 50 ohms in an ideal 4 to 1 ratio.

Figure 2 shows the same basic structure as Figure 1 except that the output and input originate from the same side. inthis modification however, leads 9 and 12 are eliminated and the conductors abut each other. Thus outer conductors 105 and 101 abut and parallel each other to eliminate lead 12 while conductors 103 and 107 abut and parallel each other to eliminate lead 9.

The impedance values and ratios of Figure 2 are identical with those of Figure 1.

Figure 3 shows a structure similar to Figure 2. Conductors 201 and 205 abut and are parallel to each other; conductors 203 and 207 also abut and are parallel to each other. Cross-connections 210,211 and 213 are identical with 10, 11 and 1.3 of Figure 1 and 110, 111 and 113 of Figure 2.

In this modification, however, the structure centering around the transformer cross-connections is encased in a shielding box 216.

The shunt reactance across the coaxial input is a function of the outer conductor diameters and the size of the shielding box. In order to realize a large impedance band width such that the SWR is kept as close to unity as possible, this shunting reactance is made high. To accomplish this, the characteristic impedance of the transmission line formed by the shield and the balun conductors is made correspondingly high.

Figure 4 shows a modified form of the balun in which the balun conductors have been coiled into an inductance. The circuit connections of this figure correspond to those in Figure 3. This type of structure has been used for high impedance delay lines as it can realize impedances of the order of 500-1000 ohms, as compared to maximum characteristic impedances in Figure 3 of -150 ohms.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed is:

A high impedance delay line circuit wherein a high impedance balanced transmission line is fed from a low impedance unbalanced line and circuit comprising a pair of high impedance coaxial lines coupled tothe balanced line; a low impedance coaxial line coupled to the unbalanced line; a low impedance conductor substantially equal in length to the low impedance coaxial line, the low impedance conductor being disposed adjacent and conductively connected to the outer conductor of one high impedance coaxial line, the outer conductor of the low impedance coaxial line being disposed adjacent and conductively connected to the outer conductor of the other high impedance coaxialline; means connecting the outer conductor of the low impedance coaxial line to the inner conductor of the said one high impedance coaxial line; means connecting the inner conductor of the low impedance coaxial line to the low impedance conductor; and means connecting the inner conductor of the said other high impedance coaxial line to the low impedance conductor, the said one high impedance coaxial line being coiled with the low impedance conductor and the said other high impedance coaxial line being coiled with the low impedance coaxial line to increase the inductive impedance of the circuit.

References Qited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Germany Sept. 17, 1953

Images