Noise in sampling phase detectors for RF PLL

Although the sampling phase detector (SPD) is very effective in phase locking of low phase noise microwave oscillators, an improvement of its noise is needed in order to fit future requirements of complex modulation schemes. This work clarifies the role of the various active devices within the SPD on noise generation. Either the transistors, used in the reference signal amplifier, or the reverse recovery diode, which generates the comb lines used in the circuit, or the mixing diodes, which deliver the error voltage, can impact the overall SPD noise, depending on the baseband frequency value.