The vast available spectrum at Mm-Wave/Terahertz (THz) frequencies is envisioned as a key enabler to solve the everincreasing data rate needs in crowded urban environments and lead the next wireless technology revolution. To overcome the high path loss present at mm-Wave/THz, highly directional antenna arrays have become ubiquitous. Their future large-scale deployment will naturally create dense wireless sensor networks, which in-turn enable joint communication and sensing. However, beamforming of high-directivity antenna arrays relies on real-time precise localization between transmitters (TXs) and receivers (RXs), to ensure robustness in dynamic mobile applications. Moreover, traditional digital encryption and decryption at multi-Gbps data rate cause large power and latency overhead, and thus wireless physical layer security has become a promising solution. In this paper, we propose and demonstrate a reconfigurable Phase-Time Array (PTA) TX with prism-like spectral-to-spatial mapping of wideband transmitted signals, which achieves keyless physically secured wireless communication and fast multi-RX localization to enable low-latency joint communication and sensing within the same wireless electronics frontend. The PTA realizes reconfigurable spectral-to-spatial mapping by applying both a phase shift and true time delay at each array element. This intentionally creates and exploits the array beam squinting effect, such that different frequency components of a wideband signal are transmitted in different directions, analogous to an optical prism. Therefore, multiple RX nodes can simultaneously determine their angular positions relative to the TX array using their received signals for fast multi-RX localization. Judiciously engineering the prism-like beam squinting in PTA TX can also selectively distort signal transmission to unwanted directions for secured communication without cryptography. Furthermore, the PTA scheme can reconfigure its element-level phase-time delay combinations to attain variable levels of communication security and localization/sensing performance depending on the needs.

This article presents a fully integrated bidirectional class-G digital Doherty switched capacitor transmitter (TX) and N-path Quadrature receiver (RX) in CMOS. Through sharing on-chip capacitor banks, typically occupying a major portion of the digital TX or RX chip area, as well as the RF passive matching networks, the overall size can be radically reduced. Moreover, the overall performance could be further improved by eliminating the need for an integrated T/RX switch and its corresponding loss and area overhead. The class-G operation is used within the Doherty TX to increase the output power and backoff efficiency, while the capacitive stacking technique is used in the RX to increase the voltage gain. A transformer network is used to present the optimum impedance for both the parallel Doherty TX and RX mode of operation, as well as the class-G Doherty active load modulation. As a proof-of-concept, the joint bidirectional class-G digital Doherty switched-capacitor TX and N-path Quadrature RX through capacitor bank sharing is implemented in a 45-nm CMOS SOI process. The TX demonstrates a Pout 1dB bandwidth (BW) of 1.6-3.1 GHz, a fractional BW >63%, and peak output power (Pout) of 22.5dBm at 2.4GHz. The peak drain efficiency (DE) of the TX is 49.5% at 1.8GHz and 41.5%/38.7%/31.6%/18.1% for the peak/2.5/6/12dB power back off (PBO) at 2.4GHz. The DE improvement compared to class-B PA is 1.24×/1.51×/1.72× at 2.5/6/12dB PBO. The TX is measured using 64-QAM/20MHz modulation without the use of AM-PM pre-distortion or pattern based DPD. It achieves an excellent -27.1dB EVM, -31.31dBc ACLR, 14.6dBm average Pout and 25.8% average DE at 1.6GHz. The RX achieves a noise figure (NF) of 7.6dB at 2.2GHz and a conversion gain of 17dB with a 12 MHz bandwidth. In addition, the proposed RX front-end achieves < -60 dBm LO leakage over the operating frequency range INDEX TERMS capacitor stacking, class-G DPA, CMOS, digital front-end, Doherty, linearity, N-path filter, polar modulation, power back off, transformer.

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This paper presents a digital power amplifier (DPA) with a built-in AM-PM compensation technique and a compact single-transformer footprint. The AM-PM distortion behavior of the current mode/voltage mode PAs are detailed and an AM-PM compensation technique for both modes is introduced. The proposed design utilizes one current-mode digital power amplifier as the main path PA and a class-G PA voltage mode digital PA as the auxiliary path PA, combined through a single transformer footprint. It provides enhanced linearity through built-in adaptive biasing and hybrid current/voltage mode Doherty-based power combing. As a proof-of-concept, a 1.2-2.4 GHz wideband DPA is implemented in the Globalfoundries 45nm CMOS SOI process. The measurements show a 37.6% peak drain efficiency (DE) at 1.4GHz, and 21.8dBm saturated output power (Psat) and 1.2×/1.4× PBO efficiency enhancement, compared to the ideal class-B at 3dB/6dB PBO at 1.2GHz. This proposed digital PA supports 20MSym/s 64-QAM modulation at 14.8dBm average output power and 22.8% average PA DE while maintaining error vector magnitude (EVM) lower than -23dB without any phase predistortion. To the best of our knowledge, this is the first demonstration of hybrid current-voltage mode Doherty power combining on a single footprint transformer over a broad bandwidth (BW).