Carrier Tracking Loop Performance in the Presence of Strong CW Interference

In a coherent data link, narrow-band radio frequency interference (RFI) near the carrier frequency can degrade the link performance by impacting the carrier tracking loop behavior and producing a partial or complete loss of coherence. If the RFI is strong enough, this effect can occur even though the frequency of the interference lies well beyond the carrier tracking loop bandwidth. In 1973, Bruno and Bianchard independently performed similar analyses of the response of a phase-locked loop (PLL) to a continuous wave (CW) interferor, and derived conditions under which the loop drops carrier lock and tracks the interference instead. This paper compares the contributions of these two analysts, and extends Bruno's closed form approximation for the loop phase error to the entire lock region.