Low cost synthesised sources for VSAT frequency converter applications

Discusses the production of low-cost downconverters for very small aperture (VSAT) receivers. It is tempting to use a proprietary low-noise block downconverter (LNB) used for the SHF to UHF conversion stage. The LNB employs a dielectric resonator oscillator (DRO) as the SHF local oscillator (LO). As an alternative the DRO can be substituted by an externally synthesised LO using a digital divider and phase detector. A wide tuning range VCO is used as a UHF reference oscillator which employs a low Q resonator, such that its phase noise is reduced by phase locking to a UHF reference. Close to carrier phase noise then becomes dominated by the crystal resonator of the UHF reference. In the critical region around the edge of the carrier recovery loop bandwidth, the phase detector/divider chain phase jitter is also important. A diagram of the phase-frequency detector is shown and was chosen because of its self acquisition properties