Although in the illustrative embodiment of FIG. 8B the waveform generator 110b is configured to generate chirped waveforms having a center frequency of 7.5 GHz, this is not a limitation of aspects of the technology described herein, as the waveform generator 110 may be configured to generate chirped waveforms having any suitable center frequency.
As described herein, in some embodiments, an interrogator device may comprise a transmit antenna configured to transmit RF signals having a first center frequency f0 and receive RF signals having a second frequency that is a harmonic of the first center frequency such as, for example, 2f0. In such embodiments, the waveform generator part in the interrogator device may be configured to generate RF signals having either the first center frequency or the second center frequency. This allows for alternative transmit and receive circuitry designs including the designs shown in FIGS. 8C and 8D.
FIG. 8C is a block diagram of an illustrative interrogator device 850 having waveform generator 110c, transmit and receive circuitry 112c, transmit antenna 114, and receive antenna 116. Waveform generator 110c includes a voltage-controlled oscillator 828 and chirp PLL circuitry 826 configured to drive the voltage-controlled oscillator, via voltage signals on line 827, to generate linear frequency modulated (LFM) RF signals having a center frequency of 60 GHz. The generated chirps are provided to transmit and receive circuitry 112c via line 851.
