Phase-hit Immunity Methods for High Speed Communication Systems

Phase-hits can cause burst error and synchronization problems in high speed communication systems. The root cause of phase-hits results from the material´s thermal expansion mismatch. The coefficient of thermal expansion (CTE) is an important material characteristic to consider. To reduce the CTE effect, an oven-controlled synthesizer is presented in this paper. By adding a proportionally controlled heater onto the synthesizer module, the temperature variation of the synthesizer module is reduced by warming up the module only at cold temperatures. Since phase-hits usually happen during the temperature transition from room to cold, this method is especially attractive when the available DC power supply is limited. It is also emphasized in this paper that a clean PCB assembly process, high quality capacitors and other techniques, such as a PCB cut-out under the VCO, are also essential for phase-hit immunity. Test results show that by applying the methods presented in this paper, the phase-hit problem can be well controlled.