hello! Gunn/ Gunnplexer

[labille]

gunnplexer

hello everybody,
first, i would like to say:"sorry!" for the mistakes because i don't speak very well english.
I work on Gunplexer i notice that the gunnplexer emits another frequencies (MHz) than the main frequency( Ghz). I don't understand why.
1) Do theses frequencies radiate from the cavitie or by an other place (components, wire etc..)
2) How can i know all of theses many frequencies? is there theory about it?

thanks a lot.

 

[mr_ghz]

Hi labille

A gunnplexer is a transmit/receive device in the GHz range. The transmit-frequency is created by a Gunn-Diode which is mounted in a cavity. The Gunn-Diode creates a negative resistance and the cavity is the resonance element and gives the oscillator (=transmitter) frequency. This frequency can be tuned by screws which are placed in the cavity or by varactordiodes. With these diodes the frequency of the transmitter can also be FM-modulated (several MHz).

The receiver consists of a schottky-diode which is also mounted in the cavity. It 'sees' the oscillator frequency and the received signal (normally by a horn mounted on the cavity). This diode demodulated the incoming RF signal. So across this diode you see the IF signal, which is in the range of several MHz.

If you want to use such gunnplexers for a RF link, you have to adjust their frequencies to match each other (only some MHz of difference is allowed). The RF signal from the other station can be seen as a FM modulated signal over you Schottky-diode.

Regards