Lin Lu

A 60-GHz waveform-sharing joint radar-communication (JRC) transceiver with phase-locked loop (PLL)-based chirp spread spectrum (CSS) modulator is presented for seamless integrated sensing and communication (ISAC). Unlike existing communication-centric JRC transceivers that prioritize high throughput, the proposed sensing-centric transceiver employs unified CSS waveforms to perform uncompromised sensing performance while enabling robust long-range communication. To this end, a PLL-based CSS modulator is implemented, simplifying the transceiver architecture while generating wideband CSS signals with high chirp slope, superior linearity, and low phase noise. Within this modulator, a multi-bank capacitor array is integrated into a two-point modulation (TPM)-based sub-sampling (SS) PLL, enabling fast wideband chirp generation and rapid frequency hopping while achieving excellent phase noise. Moreover, an adaptive binary-search (BS) overlap compensation scheme is proposed to mitigate the discontinuity issues in the multi-bank capacitor array while ensuring robust and orderly convergence. Furthermore, building on the TPM-based sub-sampling PLL (SSPLL), a digital CSS modulation engine is developed to enable wideband CSS signal generation without compromising the chirp linearity. Fabricated in a 65-nm CMOS process, the CSS transceiver core occupies 6.11 mm² and consumes 568 mW. For the over-the-air (OTA) test, broadband high-gain horn antennas with a gap waveguide (GW)-based transition are integrated with the chip through a low-loss wire-bonding matching scheme, achieving a low-cost, compact, and reliable assembly. OTA measurements demonstrate that the measured range resolution is approximately 5.5 cm, while achieving a communication range exceeding 500 m at a 4.138 Mbps data rate with a bit error rate (BER) below $10^{-5}$ .

This brief presents a 57–71-GHz transmit/receive (T/R) front-end (FE) module for large-scale phased-array transceivers. The FE consists of a T/R switch (TRSW), power amplifier (PA), low-noise amplifier (LNA), phase shifter (PS), variable gain amplifiers (VGAs), and power combiner/divider (PC/PD). To alleviate the RX signal leakage to the TX branch in the traditional asymmetric TRSW structures, a novel switchable triple-coil transformer (STCT) is proposed at the PA output, achieving a broadband high off-impedance for the RX while introducing a low loss to the TX power. In addition, to facilitate large-scale phased-array calibration, both VGA and PS feature the orthogonal amplitude and phase control, leading to low phase and gain errors. Fabricated in a 65-nm CMOS, the proposed FE achieves a peak gain of 28.4/17.3 dB with BW3 dB from 54 to 70/55 to 70 GHz in TX/RX modes. Benefiting from the proposed STCT, the TX achieves an OP$_{\mathrm {1 ~dB}}$/$P_{\mathrm {sat}}$ of 13.9/15.4 dBm with PAE$_{\mathrm {1~ dB}}$/PAE_max of 10.7%/13.7%, respectively. The RX achieves a minimum in-band noise figure (NF) of 6.6 dB at 66 GHz. During the gain tuning, the FE achieves an rms gain/phase error of 0.13 dB/1° and 0.1 dB/1.3° in the TX and RX modes, respectively. The 6-bit phase shifting performs an rms phase/gain error of 0.85°/1.3 dB and 0.8°/1.1 dB in the TX and RX modes, respectively.

This letter proposes an antenna transmit/receive (T/R) switch embedded in the power combiner of the two-way power amplifier (PA) and realizes a 60-GHz fully differential T/R front end (FE). Compared with the traditional standalone single-pole-double-throw (SPDT) switch, only one switch transistor is needed in the PA power combiner and reused for both transmit (TX) and receive (RX) modes, thereby significantly reducing the chip area and the insertion loss. With careful codesign of the switch with the PA and low-noise amplifier (LNA) matching networks, the insertion loss introduced by the switch and the loading effect could be reduced to 0.5 and 1 dB in the TX and RX modes, respectively. Fabricated in a 65-nm CMOS process, the PA achieves a power gain, OP $_{\mathrm{1\, dB}}$ , P $_{\mathrm{sat}}$ , and PAE $_{\mathrm{max}}$ of 25 dB, 11 dBm, 16 dBm, and 16%, respectively. Benefitting from the low loss of the switch, the LNA attains a peak gain and noise figure (NF) of 25 and 6.4 dB, respectively.

A 60-GHz joint radar–communication (JRC) transceiver is presented in this article. To achieve a compact JRC transceiver architecture with highly reused RF modules, a dedicated reconfigurable dual-mode Gilbert cell is proposed. Specifically, in the communication mode, the dual-mode Gilbert cells operate as conventional upconversion mixers to modulate the baseband (BB) communication data, while it could also be configured as an amplifier to strengthen the LO signal in the radar mode. Compared with the quadrature IF chirp modulation scheme in which the chirp bandwidth is constrained by the narrowband IF devices, in this work, a wideband chirp generated directly from the LO chain could be applied for radar sensing, significantly improving the range resolution in the radar mode. Besides, the direct RF dechirping could also relieve the hardware burden during radar signal processing compared with the digital dechirping utilized in the IF chirp modulation scheme. Fabricated in a 65-nm CMOS process, this JRC transceiver realizes an ultracompact chip size, and a 16-dBm saturated TX output power, an 11-dBm OP $_{\text{1\,dB}}$ , and a 5.8-dB minimum RX noise figure (NF) are also achieved. Experiments demonstrate that the proposed JRC transceiver supports $>$ 4-GHz transmitted chirp bandwidth with $<$ 3.75-cm range resolution in the radar mode, and a mechanical vibration with 1- $\mu$ m displacement is successfully detected. Besides, a $>$ 7-Gb/s data rate in the 16-QAM over-the-air (OTA) communication is also demonstrated.

A 60-GHz joint radar–communication (JRC) transceiver is introduced in this letter. Benefiting from a reconfigurable dual-mode Gilbert cell, which could not only operate as an upconversion mixer for the baseband signal but could also be configured as an amplifier for the LO signal, a highly reused JRC transceiver architecture is realized. In the radar mode, instead of utilizing the narrowband IF chirp modulation scheme, which is widely adopted in previous JRC systems, in this work, a wideband chirp generated directly from the LO chain could be applied for both transmitting and direct RF dechirping, thereby significantly improving the range resolution and relieving the hardware burden in radar signal processing. Fabricated in a 65-nm CMOS process, this work achieves a 16-dBm saturated TX output power, an 11-dBm OP $_{1~\mathrm{dB}}$ , and a 5.8-dB minimum RX noise figure (NF). Experiments demonstrate that the proposed JRC transceiver supports $>$ 7-Gb/s data rate in the 16-QAM over-the-air (OTA) communication as well as $>$ 4-GHz transmitted chirp bandwidth with $<$ 3.75-cm range resolution in the radar mode.

This letter presents a four-stage variable-gain power amplifier (VGPA) for 60-GHz time division duplex (TDD) phased array systems. To reduce the loading effect of the off-state VGPA on the receiver (Rx), a switchable inductor is proposed as an antenna transmit/receive switch (TRSW), which introduces low insertions loss to the VGPA output matching in transmitter (Tx) mode while providing a high off-impedance in Rx mode. To improve the output dynamic range, a Gilbert-based X-type variable-gain stage with low phase variation is designed. With measurements, the VGPA realizes a 25.4-dB peak gain with a BW $_{\text{{3\,dB}}}$ from 49 to 67 GHz, and a $<$ 2.6 $^{\circ}$ rms phase error is achieved over a 15-dB gain tuning range. The measured OP $_{\text{1\,dB}}$ , $P_{\text{sat}}$ , OIP $_{\text{3}}$ , PAE $_{\text{1\,dB}}$ , and PAE $_{\text{max}}$ are 11.3, 12.2, 16.2 dBm, 6.4%, and 8.9%, respectively. When the PA and the switchable inductor are turned off, a $>$ 180 $~\Omega$ output off-impedance is achieved over the interested frequency range.

This letter presents a fully integrated 16-element phased-array transceiver (TRX) supporting dual-polarization multi-input multi-output (DP-MIMO). transmitting/receiving (T/R) switches are embedded for time division duplexing (TDD) operation. High-linearity bidirectional variable gain amplifiers (Bi-VGAs) and passive phase shifters (PSs) are designed for compact area and low power consumption, respectively. Fabricated in a 65-nm CMOS process, this TRX occupies an area of 25.76 mm $^{2}$ . With integrated frequency synthesizer, the TRX can work from 37 to 43.5 GHz, which can fully cover 5G new radio (NR) frequency range 2 (FR2) n259 and n260 bands. In the receiver (RX) mode, a noise figure (NF) of 5.4–6.3 dB and a peak conversion gain (CG) of 27.3 dB are achieved. The transmitter (TX) mode achieves a peak CG of 48.7 dB, a 13.1-dBm OP $_{\mathrm{1\,dB}}$ , and a 15.8-dBm $P_{\mathrm{sat}}$ . By using 64-QAM modulation, measurement results show that the TRX achieves a data rate up to 7.2 Gb/s per independent data stream with 7.65 dBm output power per channel.

Caused by inappropriate allocation of the interstage power mismatches during broadband matching, the boosted dynamic dc current of the frequency doubler (FD) would deteriorate the broadband efficiency. To tackle this issue, an efficiency-optimized broadband matching strategy is proposed by allocating all of the desired low-frequency mismatches ahead of the push-push (PP) pair, which not only keeps a broadband output but also reduces the dynamic dc current and improves the efficiency over the entire operating bandwidth simultaneously. To further enhance the 2nd harmonic (HR2) output power, a fourth-order notch filter is also designed at the PP pair input. Fabricated in a 65-nm CMOS process, the proposed Ka-band FD exhibits $>$ 15% efficiency from 24.6 to 36 GHz, and a 23.5% peak efficiency is achieved. A 42.6% fractional bandwidth (FBW) is also realized with a fundamental rejection ratio (FRR) over 45 dBc.

In the field of non-contact sensing, both the continuous-wave (CW) Doppler radar and the frequency-modulated continuous-wave (FMCW) radar have their own superiorities. A combination of these two radar modes would be a suitable choice to accommodate various application scenarios. This paper presents a 60-GHz hybrid FMCW-Doppler radar transceiver fabricated in a 65-nm CMOS process. An on-chip frequency quadrupler driven by a 15-GHz external signal source is utilized for the 60-GHz hybrid waveform generation. Based on the hybrid operating modes, a robust I/Q imbalance calibration method is also proposed. Specifically, in the Doppler radar mode, the imbalance factors are extracted by evaluating the quadrature beat signals during the FMCW period, and then the interferometry signals are calibrated to improve the detection performance. Unlike the trajectory-based ellipse-fitting method, the accuracy of the estimated imbalance factor is independent of the target displacement. Compared with the test-signal-based imbalance factors extraction ahead of the target detection, the real-time extraction during the target detection is more efficient and can also mitigate the estimation errors caused by environmental variations. With the proposed hybrid radar system and the I/Q calibration method, an 80-mm linear displacement is recovered with a 0.016-mm root mean square error (RMSE), and a periodic vibration with a 1-μm amplitude is detected with a 16.4-dB signal-to-noise ratio (SNR). Multiple-target detection is also performed in the FMCW radar mode, and the vibration trajectories are recovered accurately.

A differential laser trigonometry method is presented for measurement of the oil film thickness on a water surface. The thickness of an oil film can be obtained with two off-plane displacements to a benchmark plane obtained by the imaging spot displacement and the configuration parameter of the imaging system subtracted. The method has been tested in the laboratory via the examination of diesel oil and petroleum films. An experimental system setup has been developed, by which the maximum measurable thickness is 12 mm and the average measurement error is 6.05 µm. The results show that the method presented is feasible, and applicable to dynamic online measurement of oil film thickness of oil spills on the sea surface.