Phase locked loops are widely used in radio communication systems. They extract information from the received modulated waveform to align the frequency and phase of local oscillators in the receiver. In particular, carrier acquisition and tracking requires the direct digital synthesizer to be frequency and phase locked to the underlying suppressed carrier of the received modulated wave shape. Similarly, timing acquisition and tracking requires the time sample positions of the sampling clock be aligned with the frequency and phase of the underlying modulation waveform. The goal of this research is to study DSP based phase lock loops in DSP based receivers that perform carrier and timing recovery over a wide range of signal to noise ratio with the emphasis being performance enhancement at low signal to noise ratio.