Hiroshi Hamada

This article presents a 300-GHz band transmitter (TX) and receiver (RX) wireless front end (FE) with a differential architecture based on our in-house InP-based high electron mobility transistor (InP-HEMT) technology. To resolve the issue of the signal-to-noise-and-distortion ratio (SNDR) deterioration caused by the local oscillator (LO) leakage (LOL) in the integrated FE, we quantitatively investigated the effect of the LOL on SNDR by means of link budget calculation and derived the necessary power/phase imbalances in differential architectures to sufficiently reject the LOL. To achieve a sufficiently high LOL rejection, we propose the use of a 300-GHz band LO power amplifier (PA) with a high common-mode rejection ratio (CMRR). The target value of the LO PA’s CMRR (>15 dB) is also derived by the analysis to clarify the relationship between the power/phase imbalances and the CMRR. The unit amplifier in the LO PA achieves the simulated CMRR of more than 15 dB over the full range of the WR3.4 band (220–330 GHz) thanks to utilizing a common-mode rejection circuit (CMRC) based on passive components. By using the integrated circuit of LO PA and a mixer, we experimentally confirmed that the LOL of the TX is less than −33 dBm with the LO frequency range of 224–330 GHz and LO power of 0 dBm. The fabricated 300-GHz band TX and RX achieve a high conversion gain (CG) of above 5 dB over wide bandwidths of 35 and 56 GHz, respectively. We successfully demonstrated 16QAM 160-Gb/s over-the-air (OTA) data transmission using the fabricated FE with the link distance of 43 m. To the extent of the authors’ knowledge, this is the highest reported data rate achieved with a 300-GHz band FE.

This letter presents a 300-GHz-band power amplifier (PA) module implementing a PA integrated circuit (IC) fabricated in 250-nm indium phosphide (InP) double-heterojunction bipolar transistor (DHBT) technology. The PA module achieved a maximum gain of 30 dB, maintaining over 20-dB gain across the 220–310-GHz range, with a saturated output power of 9.1dBm. We applied a spectral digital predistortion (DPD) method to compensate for the distortion of the PA module and achieved a 280-Gb/s (35-GBaud 256QAM) signal generation at 0-dBm output power, which is the highest data rate reported in the 300-GHz band.

We designed and fabricated a 300-GHz-band fundamental mixer in indium phosphide (InP) high electron mobility transistor (HEMT) technology for 6G wireless communications. We devised a widely split frequency matching network to widen the bandwidth of a resistive mixer. The mixer IC achieved a conversion gain of $-$ 15 and $-$ 6-dB RF bandwidth of 100 GHz (220–320 GHz), the widest ever reported. We implemented the mixer IC as a WR3.4 waveguide mixer module and performed a back-to-back data transmission experiment in three different frequency bands. Data rates of 120, 152, and 168 Gbps were achieved in each band. We also developed a dual-band data transmission system with a local oscillator (LO) leakage canceling method. It was capable of transmitting data at 240 Gbps, the highest rate reported to date, and suppressing LO leakage by 60 dB.

2023 International Conference on Solid State Devices and Materials ,Feasibility Study of InP-based Tera-Hertz-ICs Fabrication Process for Beyond 5G / 6G Wireless Network Systems

This letter presents a 300-GHz-band four-element phased-array transmitter (TX) consisting of two types of chips, CMOS and InP HBT, to achieve a high equivalent isotropically radiated power (EIRP) and wide beam coverage. The CMOS chips include mixers and control circuits for the phased-array operation and the InP HBT chips include 300-GHz-band power amplifiers (PAs) and Antipodal Vivaldi on-chip antennas. The two types of chips are connected in a flip-chip-on-chip fashion to reduce losses. A method utilizing grating lobes is devised to overcome the limited main lobe steering range. The fabricated TX achieves a maximum EIRP of 8.4 dBm with a steering range of 36 $^{\circ}$ , which is the widest among the 300-GHz-band TXs that can handle a high modulation order. The TX also demonstrates the first-ever wireless data transmission with beam steering in the 300-GHz band and achieves a maximum data rate of 30 Gb/s over a 50-cm distance.

This article introduces a four-element 300-GHz-band bi-directional phased-array transceiver (TRX). The TRX utilizes the same antenna, signal path, and local oscillator (LO) circuitry to operate either in transmitter (TX) mode or receiver (RX) mode. The TX mode adopts the outphasing technique to increase the average output power for higher order modulation schemes by utilizing the two mixers that are connected directly to the antenna in a mixer-last fashion. The two signal paths also enable the canceling of the LO feed-through (LOFT). The RX mode also benefits from the LOFT cancellation technique to suppress the LO emission, which is a common issue of the mixer-first RXs. The RX has a separate Hartley operation mode to reject the image signal coming from the TX. The TRX chip was implemented using CMOS 65-nm process, and a four-element phased array was implemented by stacking liquid crystal polymer (LCP) flexible printed circuit boards (PCBs). The stacked structure provides the required narrow antenna pitch at the 300-GHz band. The measured beam angle range is from −18° to 18°. The single-element power consumption is 750 mW for both TX mode and RX mode.