| 摘要 |
1,178,488. Phase-shifters. COMPAGNIE FRANCAISE THOMSON HOUSTONHOTCHKISS BRANDT. 31 March, 1967 [31 March, 1966], No. 14966/67. Heading H1W. A phase-shift of 0 or # in a microwave signal is obtained by variation in the impedance of a semi-conductor device (or devices) connected in series with the central conductor of a transmission line in the vicinity of a short-circuit. As shown, two such devices 341, 342, e.g. varactor diodes, are connected as shown in series with the central conductor 31, 312, 311 of a coaxial line which is short-circuited at 33. A bias signal, which alternates between the two extreme bias voltages of the diodes, is applied through leads 361, 362. Where the bias signal has a relatively high frequency, it is applied through appropriate matching quarterwave stubs. The inductance L of the sections 311, 312 is such that L = CZ 0 where C is the capacitance of the diodes in the back-biased condition and Z 0 is the characteristic impedance of the line. If, in addition, 1/#C # Z 0 and #L ½ Z 0 , the microwave signal in line 31, 32 suffers, upon reflection, phase-shifts of 0 and # respectively in the two opposite conductive states of the diode. A tri-plate line may be used. The diode or diodes may be directly connected to the short-circuit without interposition of the stub 311 if C is small enough. The phase-shift device may be connected to one of the ports of a three-port circulator, the other two ports furnishing input and output respectively. Alternatively, a phaseshifter may be connected to each of the conjugate ports of a 3db. directional coupler of which the other two port form the input and output respectively. A ring hybrid coupler -may be substituted for the 3db. coupler but, in this case, the diodes in the two phaseshifters must be controlled in phase opposition. To avoid this condition, the electrical lengths between the phase-shifters and the corresponding ports of the ring hybrid may be arranged to differ by one quarter-wavelength at the microwave frequency. |
