  Precise measurements of the frequency and phase of an electrical or optical
signal play a key role in various branches of science and engineering. Tracking
changing laser frequencies is especially demanding when the lasers themselves
are noisy or if the frequencies rapidly change because they encode highly
dynamic signals in, e.g., Doppler-ranging or dynamic cavity readout. Here, to
address these and other possible applications, we report the development of a
high signal bandwidth (> 2 GHz) and high tracking bandwidth (2 MHz)
multi-channel Phasemeter. The implementation utilizes an all-digital
phase-locked loop realized within the field programmable gate array (FPGA) part
of a Radio Frequency System-on-Chip (RFSoC), the programmable logic (PL). The
new features of the phasemeter are obtained by operating the PL at its timing
limits and introducing a multi-demodulation and phase accumulation scheme. We
present performance measurements, discuss the role of the high tracking
bandwidth for tracking highly dynamic signals, and demonstrate ultra-stable
phase locking of a beat note between two widely tunable external cavity diode
lasers. We achieve a phase-noise floor in the sub-milli radian regime when
comparing two signals, even for GHz frequencies, and demonstrate stable
tracking of signals with a frequency change rate of 240 GHz/s.
