Abstract
Near-field mapping has proven to be a powerful technique for characterizing and diagnosing antennas in the microwave frequency range. However, conventional measurement methods based on a network analyzer cannot be applied to on-chip antenna devices extensively studied for future wireless communication in the millimeter wave (mm-wave) (30–300 GHz) and terahertz (THz) wave (0.1–10 THz) frequency regions. Here, we present a new asynchronous mapping technique to investigate the spatial distribution of not only the amplitude but also the phase of the electric field generated by free-running, self-oscillating generators including CMOS oscillators, Gunn oscillators, resonant tunneling diodes, and quantum cascaded lasers. Using a photonic-electronic hybrid measurement system, a wide frequency coverage, minimal invasiveness of the field to be measured, and phase distribution measurements with a theoretically-limited sensitivity are simultaneously achieved. As a proof-of-concept experiment, we demonstrate the mapping of a mm-wave (77 GHz) generated by a free-running Gunn oscillator and antenna characterization based on near-to-far field transformation.
Highlights
Of late, millimeter and terahertz (THz) waves have attracted significant attention owing to their applications in radar systems[1, 5] G networks[2], THz wireless communication[3], etc
In our measurement setup (Fig. 1(b)), the spatial distributions of the amplitude and phase of the far-field, as well those of the near-field, are measured using two electro-optic (EO) probes: the measurement probe is for mapping and the reference probe for phase noise cancellation
The frequency of the intermediate frequency (IF) signal is, fIF = f2 − f1 − fRF = mfCS − fRF, where m is the mode separation index, fcs is the comb-mode separation, and fRF is the frequency of the RF signal
Summary
Millimeter (mm) and terahertz (THz) waves have attracted significant attention owing to their applications in radar systems[1, 5] G networks[2], THz wireless communication[3], etc In these higher frequency regions, on-chip antenna devices, in which the antennas are integrated with peripheral circuits such as oscillators, mixers, and amplifiers, have been extensively studied[4]. The frequency converted IF signal[1] and signal[2] have the same frequency fluctuations This common mode frequency fluctuation, more generally the common mode phase noise, is cancelled-out in the second part of the system to extract the relative phase difference of the field measured at two different points[15]
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