A Digital Integrator for an S-band High-speed Frequency-hopping Phase-locked Loop

Phase-locked loop (PLL) frequency synthesizers used for high-speed data transmission must rapidly hop and lock to new frequencies. The fundamental problem is that the settling time depends inversely on the loop bandwidth, and increasing the bandwidth causes unwanted noise interference and stability problems for the circuit. We demonstrate the feasibility of replacing the analog integrator in the PLL with a digital integrator. This circuit has advantages of increased hopping speed, ability to compensate for temperature drift and system stability. PLL lock-in was demonstrated in a prototype circuit designed and built with both discrete components and with a programmable logic device.