This paper presents a 300-320 GHz sliding-IF I/Q receiver front-end in 130 nm SiGe BiCMOS technology with ft/fmax of 300 GHz/450 GHz. The architecture, unlike direct conversion receiver at sub-THz/THz frequency range, removes the need of LO frequency same as carrier frequency. Consequently, power consumption of the LO chain is significantly reduced. Signal amplification is performed at IF stage. LO frequency at two-third and one-third of carrier frequency is generated, from external 50 GHz LO signal, using on-chip frequency doublers for RF and I/Q mixers, respectively. The receiver provides 15.2 dB of conversion gain at 310 GHz. The 3-dB RF and BB bandwidths are measured to be 26 GHz and 8 GHz, respectively. Input referred compression point (ICP) and SSB noise figure of the receiver are measured to be -17 dBm and 29.5 dB, respectively. RF and LO chain of the receiver consume 296 mW and 110 mW, respectively.

This paper discusses methods to implement a sub-THz transceiver for 300 GHz band with minimal LO frequency. An existing sub-harmonic mixer, used previously in direct conversion transceiver, is applied in a sliding-IF mixer architecture. Sub-harmonic mixer with sliding IF architecture is envisioned to further reduce the need of higher LO frequency for upconversion. In this aspect, two architectures are studied by spectral analysis and further verified through circuit simulator. The first has a problem with overlapping sidebands, making it unsuitable for non-symmetrical double sideband modulations. On the other hand, the second architecture manages to up-convert signals up to fo, using a single LO frequency of fo/3.

Moving to sub-THz frequencies introduces new challenges for wireless communications systems in terms of design, implementation, and testing. This paper presents a measurement technique for over-the-air (OTA) characterisation of sub-THz antennas at WR3.4 band (220-330 GHz), and a silicon (Si) lens fed by an on-chip antenna is used as a test vehicle. In the proposed measurement technique, the received sub-THz AM-modulated test signal is downconverted to kHz-range using a square-law power detector. Measurements and simulations/calculations are used to compare several key antenna/link parameters. Agreement between the results is good, which shows that the proposed technique provides a good and less hardware-intensive alternative for sub-THz antenna measurements.

At sub-THz frequencies, the local oscillation for transceivers is often generated by an analog frequency multiplier tree. This paper studies the origins and minimization of spurious tones in a local oscillator multiplier consisting of a chain of frequency doublers. It is found that the nearest spurious components depend on the leakage of the input signal in the first multiplier, which can be minimized by active bias tuning, filtering in the first stage or better balance in the driving differential signal. To verify the nonlinearity modeling, 0.13-µm SiGe BiCMOS technology has been utilized.

No abstract