UHF down converter

I would like to know about "down converters " especially "UHF down converters".
Also about ,loop filters,local oscillators,VCO,various crystal oscillators like VCXO,TCXO,OCXO ,double balanced mixers,frequency synthesizer,clock oscilator-10 MHz,PLL,passive filters and active filters and their design techniques,QPSK modulation technique used in down conversion.

If possible please suggest some related scientific websites.
Thanking You
Gayathri

Americal Radio Relay League or Radio Society of Great Britain have excellent publications and websites. This is common subject matter for amateur radio operators. Good luck.