| 摘要 |
A microwave oscillator circuit, suitable for use as the local oscillator in beam transmitters, radar systems and satellite TV receivers, comprises an active element (IMPATT, Gunn diode) at one end of a coaxial transmission line which is terminated at its other end by a matched load. At a suitable distance from the diode a high Q transmission cavity resonator is coupled to the transmission line via a first coupling hole. A drawback of such a circuit is that a portion of the oscillator power at the required oscillator frequency fo is dissipated in the terminal impedance Zo. This is obviated by coupling the transmission resonant cavity to the transmission line via a second coupling hole (12, FIG. 1 and FIG. 2). The distance between the first and the second coupling hole is 1/4 lambda . As a result the terminal impedance, which has been transformed very frequency-selective to a very high value in situ of the second coupling hole, is transformed to a very low value at the first coupling hole and very little power is dissipated in this low impedance, so that a considerable improvement of the circuit efficiency has been achieved. |
