Influence of step recovery diode DC bias on AM/P conversion in sampling phase detectors

Sampling phase detectors (SPD) are often used in PLL-based ultra-low phase noise microwave synthesizers. In most cases sampling pulses are obtained through use of a step recovery diode (SRD). However, due to principle of their operation such diodes exhibit significant AM/PM conversion. We found out that this effect can be one of the important limiting factors to achievable phase noise performance. In this paper we propose method of applying additional DC bias to the SRD which should provide some limited control over AM/PM conversion effects. We present experimental results obtained by locking 1.3 GHz dielectric-resonator oscillator (DRO) to a 100 MHz reference.