| 摘要 |
The apparatus is particularly for measuring the refractive index of the air in which the microwave cavity is immersed; it comprises a voltage-controlled microwave oscillator 16 coupled to the cavity, a feedback circuit to sample a signal in the cavity and to control the oscillator frequency so as to bring it to the resonant frequency of the cavity, and means 22 for measuring the oscillator frequency. The feedback circuit comprises a phase comparator 26 which compares the phase of the driving signal with the phase of the sampled signal and provides an output signal, and a circuit 26 for amplifying the output signal and applying it to a control input of the oscillator 16. <IMAGE>
|
