Extended Range Frequency Synthesis
Original Publication Date: 1979-Mar-01
Included in the Prior Art Database: 2005-Feb-20
Stations for communicating over cable in a frequency division multiplex system employ local frequency synthesis to generate carrier frequencies used for transmission and reception. For a small frequency range the synthesized frequencies may be derived from a voltage controlled oscillator (VCO) in a phase-locked loop (PLL) which is locked to a reference frequency, the latter derived by division of a precise reference frequency supplied to all stations from a common source. The frequency range of a VCO is limited by design constraints to an upper frequency limit fH roughly three times the low frequency limit fL. The number of phase-locked loops required to span a range of several hundred megacycles with complete coverage (i.e., no large frequency voids) represents a not insignificant cost factor.