| 摘要 |
811,807. Waveguide impedance matching. WESTERN ELECTRIC CO. Inc. Jan. 25, 1957 [Jan. 26, 1956], No. 2784/57. Class 40 (8). A waveguide transformer for matching two guides 11, 12 of different dimensions and characteristic impedances K1, K2 comprises an intermediate quarter-wave section with a characteristic impedance KO lying between K1 and K2 whose narrow dimension is larger or smaller than the narrow dimension of the guide 11 to produce a capacitive shunt susceptance and whose wide dimension is smaller or larger than the wide dimension of the guide 11 to produce an inductive shunt susceptance equal in magnitude to the capacitive shunt susceptance. The impedance of the intermediate section is chosen according to the relation K0=#K1K2 and, using known equations, a range of ratios of a0/a1 and b0/b1 (see Fig. 1), which will give the desired value of KO is determined. A further equation of an empirical nature (given in the Specification) sets forth the relation between the above dimensional ratios necessary to produce a non-susceptive junction between guides 11 and 13. This equation is combined, using a graphical method, with the known equations connecting the dimensional ratios with the characteristic impedance ratios to give unique values for a0/a1 and b0/b1 whereby a transition section having the desired impedance and forming anon-susceptive junction with the guide 11 may be constructed. These proportions also determine the dimensions of the discontinuities between the transition section 13 and the guide 12. If these are not negligible they may be compensated by known methods or by a second quarter-wave section having the same characteristic impedance as the guide 12 inserted between the section 13 and the guide 12. It is shown in-the Specification that the dimensions of the second quarter-wave section may be chosen such that it forms non-susceptive junctions at either end. Alternatively, one or more quarter-wave sections designed in a similar manner to the section 13 to have an intermediate impedance may be inserted between the section 13 and the guide 12. The impedance steps between the successive soctions may follow a linear, exponential, binomial or other desired distribution. The transformer may be used to couple rectangular guides to circular or oval guides. |
