In some embodiments, waveform generator circuitry 1320 may be fabricated at least in part on a semiconductor die. For example, as shown in FIG. 13B, oscillator 1322, signal splitter 1324, programmable digital divider 1326, and frequency mixer 1328, and summation block 1330 may be realized as integrated circuitry fabricated on a semiconductor die part of the interrogator. On the other hand, loop filter 1332, step/impulse generator 1334, and fixed-frequency reference oscillator 1336 may be implemented off the semiconductor die, for example, as discrete components on a substrate. However, in other embodiments, all, none or a different subset of the components of waveform circuitry 1320 may be realized as integrated circuitry fabricated on a semiconductor die part of the interrogator.
FIG. 13C is a block diagram illustrating waveform generator circuitry 1340 configured to generate frequency-modulated waveforms using a phase locked loop, in accordance with some embodiments of the technology described herein. Waveform generator circuitry 1340 may be part of any waveform generator described herein including, by way of example and not limitation, waveform generators 110, 110b, 110c, and 110d described above with reference to FIGS. 8A-D.
