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A CMOS cascode amplifier, biased near the threshold voltage of a MOSFET, for terahertz direct detection is proposed. A CMOS terahertz imaging circuit (size: 250 × 180 ìm) is designed and fabricated on the basis of low-cost 180-nm CMOS process technology. The imaging circuit consists of a microstrip patch antenna, an impedance-matching circuit, and a direct detector. It achieves a responsivity of 51.9 kV/W at 0.915 THz and a noise equivalent power (NEP) of 358 pW/Hz^1/2 at a modulation frequency of 31 Hz. NEP is estimated to be reduced to 42 pW/Hz^1/2 at 100 kHz. These results suggest that cost-efficient terahertz imaging is possible in the near future.

Compact microstrip antennas based on split-ring resonator (SRR) structure are proposed and fabricated in this paper. The resonant frequency of the antennas is discussed upon different geometric structures. The influencing mechanism of the antenna parameters on resonant frequency is analyzed. The analytical and experimental analyses are carried out and proved that the resonant frequency can be controlled from 13.5 GHz to 17.2 GHz by tuning some of the crucial parameters. A good agreement between the simulations and the measurement results suggests that the proposed antenna can be designed at different resonant frequencies while maintaining a small-size, low-profile structure and good performance.

In this work, a novel multiple input multiple output (MIMO) array antenna system with a large bandwidth and high gain has been simulated, analyzed, fabricated, and measured. The proposed antenna is structured in $2\times 4$ patch configuration along with a cross shaped ground plane loaded with four square and one circular shaped defect. The projected antenna occupies a total size of $43.611\times 43.611\times 0.42{\mathrm{\text{mm}}}^3$. Several slots in an elliptic form have been added to the patches to achieve the required results in terms of wide bandwidth and high gain. The MIMO antenna array is fabricated and experimentally tested to confirm the simulation results. The suggested MIMO array antenna offers an impedance bandwidth of 22GHz covering 22–44GHz wide range of frequencies with a high peak gain of 17dBi at 38GHz. The designed MIMO antenna offers superior diversity performance and it supports several 5G NR bands n257/n258/n259/n260/n261 in the mm-wave spectrum. The suggested MIMO antenna supports 5G application bands that are deployed in UK, USA, China, Europe, Canada, India, and Europe.

This paper describes a four-port MIMO antenna array design featuring bow-tie-shaped slot-loaded patches with wideband capabilities that cover the frequency range from 24.2GHz to 30.8GHz. The proposed antenna design is printed on an FR4 substrate and occupies an area of 25×24mm². The MIMO antenna consists of four antenna arrays that are symmetrically placed in an upper-lower configuration. The bow-tie-shaped slots loaded radiators are separated horizontally by 3.48mm and vertically by 5.94mm. Each antenna array contains two elements that are separated by a distance of wavelength/4. The suggested MIMO antenna array delivers a high gain of 19.09dB at 27.8GHz and has a bandwidth of 6.6GHz that covers the frequency band of 24.2–30.8GHz. The research demonstrates the quality of the proposed MIMO antenna through various diversity parameters such as mutual coupling, port correlation, diversity gain, and data rate that can be transmitted over a communication medium. The simulation results are validated and found to be consistent with the experimental results. The presented antenna covers the entire bandwidth allocated to different regions, including Europe (24.25–27.5GHz), Sweden (26.5–27.5GHz), USA (27.5–28.35GHz), China (24.25–27.5GHz), Japan (27.5–28.28GHz), and Korea (26.5–29.5GHz). The proposed MIMO antenna design could be an excellent option for 26/28GHz 5G NR n257, n258, and n260 bands under mm-wave wireless communication systems.

A CMOS cascode amplifier, biased near the threshold voltage of a MOSFET, for terahertz direct detection is proposed. A CMOS terahertz imaging circuit (size: 250 × 180 μm) is designed and fabricated on the basis of low-cost 180-nm CMOS process technology. The imaging circuit consists of a microstrip patch antenna, an impedance-matching circuit, and a direct detector. It achieves a responsivity of 51.9 kV/W at 0.915 THz and a noise equivalent power (NEP) of 358 pW/Hz^½ at a modulation frequency of 31 Hz. NEP is estimated to be reduced to 42 pW/Hz^½ at 100 kHz. These results suggest that cost-efficient terahertz imaging is possible in the near future.