Phased Array Transmitter Research Articles

K/Ka-Band Hybrid-Packaged Four-Element Four-Beam Phased-Array Transmitter and Receiver Front-Ends With Optimized Beamforming Passive Networks

K/Ka-Band Hybrid-Packaged Four-Element Four-Beam Phased-Array Transmitter and Receiver Front-Ends With Optimized Beamforming Passive Networks

A Phase-Modulation Phase-Shifting Phased-Array Transmitter With Phase Self-Calibration and Deep PBOs Efficiency Enhancement

A Phase-Modulation Phase-Shifting Phased-Array Transmitter With Phase Self-Calibration and Deep PBOs Efficiency Enhancement

A 2D Ultrasound Phased-Array Transmitter ASIC for High-Frequency US Stimulation and Powering.

Ultrasound (US) neuromodulation and ultrasonic power transfer to implanted devices demand novel ultrasound transmitters capable of steering focused ultrasound waves in 3D with high spatial resolution and US pressure, while having a miniaturized form factor. Meeting these requirements needs a 2D array of ultrasound transducers directly integrated with a high-frequency 2D phased-array ASIC. However, this imposes severe challenges on the design of the ASIC. In order to avoid the generation of grating lobes, the elements in the 2D phased-array should have a pitch of half of the ultrasound wavelength, which, as frequency increases, highly reduces the area available for the design of high-voltage beamforming channels. This article addresses these challenges by presenting the system-level optimization and implementation of a high-frequency 2D phased-array ASIC. The system-level study focuses on the optimization of the US transmitter toward high-frequency operation while minimizing power consumption. This study resulted in the implementation of two ASICs in TSMC 180 nm BCD technology: firstly, an individual beamforming channel was designed to demonstrate the tradeoffs between frequency, driving voltage, and beamforming capabilities. Finally, a 12-MHz pitch matched 12 × 12 phased-array ASIC working at 20-V amplitude and 3-bit phasing was designed and experimentally validated, to demonstrate high-frequency phased-array operation. The measurement results verify the phasing functionality of the ASIC with a maximum DNL of 0.35 LSB. The CMOS chip consumes 130 mW and 26.6 mW average power during the continuous pulsing and delivering 200-pulse bursts with a PRF of 1 kHz, respectively.

300-GHz-Band Four-Element CMOS-InP Hybrid Phased-Array Transmitter With 36circ Steering Range

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> , 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.

A Ka-Band 64-Element Deployable Active Phased-Array TX on a Flexible Hetero Segmented Liquid Crystal Polymer for Small Satellites

A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Ka$</tex-math> </inline-formula> -band 64-element deployable active phased-array transmitter (TX) on a hetero segment liquid crystal polymer (LCP) substrate for small satellites is proposed. The proposed phased-array TX achieved a large array size implementation and a small form factor with integrated six-layer and two-layer LCP substrates. Antenna and transmission line designs considering hetero layer structure are presented in detail. Achieving 46.7 dBm electronically isotropically radiated power (EIRP), the proposed phased-array TX can support 256-APSK DVB-S2X. As a result, the proposed deployable active phased-array TX successfully realizes low-launch cost with a 9.65 g lightweight and large antenna aperture size with superior EVM performance.

An integrated photonic-assisted phased array transmitter for direct fiber to mm-wave links

Millimeter-wave (mm-wave) phased arrays can realize multi-Gb/s communication links but face challenges such as signal distribution and higher power consumption hindering their widespread deployment. Hybrid photonic mm-wave solutions combined with fiber-optics can address some of these bottlenecks. Here, we report an integrated photonic-assisted phased array transmitter applicable for low-power, compact radio heads in fiber to mm-wave fronthaul links. The transmitter utilizes optical heterodyning within an electronically controlled photonic network for mm-wave generation, beamforming, and steering. A photonic matrix phase adjustment architecture reduces the number of phase-shift elements from M × N to M + N lowering area and power requirements. A proof-of-concept 2 × 8 phased array transmitter is implemented that can operate from 24–29 GHz, has a steering range of 40°, and achieves 5 dBm EIRP at an optical power of 55 mW without using active mm-wave electronics. Data streams at 2.5 Gb/s are transmitted over 3.6 km of optical fiber and wirelessly transmitted attaining bit-error rates better than 10−11.

Reconfigurable-Intelligent-Surface-Aided Wireless Power Transfer Systems: Analysis and Implementation

Reconfigurable intelligent surface (RIS) is a promising technology for RF wireless power transfer (WPT) as it is capable of beamforming and beam focusing without using active and power-hungry components. In this paper, we propose a multi-tile RIS beam scanning (MTBS) algorithm for powering up internet-of-things (IoT) devices. Considering the hardware limitations of the IoT devices, the proposed algorithm requires only power information to enable the beam focusing capability of the RIS. Specifically, we first divide the RIS into smaller RIS tiles. Then, all RIS tiles and the phased array transmitter are iteratively scanned and optimized to maximize the receive power. We elaborately analyze the proposed algorithm and build a simulator to verify it. Furthermore, we have built a real-life testbed of RIS-aided WPT systems to validate the algorithm. The experimental results show that the proposed MTBS algorithm can properly control the transmission phase of the transmitter and the reflection phase of the RIS to focus the power at the receiver. Consequently, after executing the algorithm, about 20 dB improvement of the receive power is achieved compared to the case that all unit cells of the RIS are in OFF state. By experiments, we confirm that the RIS with the MTBS algorithm can greatly enhance the power transfer efficiency.

Multifocus Techniques for Reconfigurable Intelligent Surface-Aided Wireless Power Transfer: Theory to Experiment

Recently, reconfigurable intelligent surface (RIS) with passive beamforming capability is emerging as a potential technology for wireless power transfer (WPT) applications thanks to its cost-effective and energy-efficient features. This work studies multifocus techniques for RIS-aided WPT systems to simultaneously and adaptively charge multiple Internet of Things (IoT) devices in the Fresnel zone. In particular, we propose three multifocus methods, which are pattern addition (PA), random unit cell interleaving (RUI), and RIS tile division (RTD), for enabling multifocus RIS-aided WPT applications. We elaborate the algorithms for computing the RIS reflection phases for all methods. The proposed methods can balance the power levels of beams focused on multiple receivers by controlling weight factors. Furthermore, we have implemented a real-life RIS-aided WPT testbed to verify these proposed methods. The system consists of a phased antenna array transmitter, two receivers, and a 1-bit RIS with 512 unit cells. The WPT experiments have been performed in several test scenarios to show the effectiveness of the proposed techniques. The experiment results demonstrate that the proposed schemes effectively generate multiple focusing beams with adjustable power levels toward the desired receivers.

Statistical Digital Predistortion of 5G Millimeter-Wave RF Beamforming Transmitter Under Random Amplitude Variations

The nonlinearity of the fifth-generation (5G) millimeter-wave (mmWave) phased array transmitter (TX) depends on the variations in the beamforming coefficients, e.g., due to unwanted amplitude errors of the phase shifters or purposely introduced amplitude variations to shape the beam, as well as other analog component variations. Therefore, also the digital predistortion (DPD) coefficients depend on the beamforming coefficients and require a continuous update for different beamsteering directions in a conventional DPD. We propose a robust DPD approach that uses the average array response for DPD training. The average array response is estimated using the known experimental histogram of power amplifier (PA) input power variation resulting from the amplitude variations due to beamforming. The DPD training based on the average array response makes the DPD coefficients insensitive to beamforming variations. The proposed DPD strategy requires a shared feedback path for training and only a single set of DPD coefficients to linearize the array response in all beamsteering directions. The performance of the proposed DPD strategy is validated by over-the-air (OTA) measurements of a 28-GHz phased array TX over different steering angles. Experimental results show that the proposed DPD method using one set of DPD coefficients provides similar linearization performance across the steering angles compared with the DPD trained to all steering angles through the OTA reference antenna.

W-band Scalable 2×2 Phased-Array Transmitter and Receiver Chipsets in SiGe BiCMOS for High Data-Rate Communication

This article presents a pair of W-band phased-array transmitter (TX) and receiver (RX) chipsets in a 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> SiGe BiCMOS process for high data-rate wireless communication. Both the chips integrate four compact front-end channels in 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 distribution, and the distance between the adjacent RF pads is less than 1.8 mm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.56\lambda $ </tex-math></inline-formula> at 90 GHz) to fit for the tight antenna array and enable array scaling by tiling multiple unit cells. A 6-bit active phase shifter based on the improved phase-inverting variable gain amplifiers is leveraged to achieve high phase-shift precision and bandwidth concurrently. A noise reduction technique using a parallel inductor to resonate with the parasitic capacitors of the cascode transistors is adopted in the low-noise amplifier design. A novel miniature power combiner, which occupies a much more compact area than the Wilkinson power combiner while delivering great RF performance, is proposed and elaborately analyzed. System-level calibration for local oscillator (LO) leakage and dc-offset suppression is enabled by introducing digitally controlled current sources into the up-conversion and down-conversion mixers. On-wafer measurements for the TX chip exhibit a single-channel IF-to-RF conversion gain (CG) of 26 dB, a competitively high output 1-dB compression point (OP <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1\,dB}}$ </tex-math></inline-formula> ) of 11 dBm. The RX chip achieves an RF-to-IF CG of 19.5 dB with 9-/14-GHz IF/RF 3-dB bandwidth, a noise figure of 7.7 dB, and an input 1-dB compression point of −28 dBm. The phase-shift characteristics are verified by the TX/RX front-end measurements, achieving a 6-bit phase resolution with minimum rms phase/gain error smaller than 0.83°/0.45 dB and a large phase-shift bandwidth higher than 20 GHz. Preliminary wireless transmission test using a low-cost die-on-printed circuit board (PCB) prototype demonstrates wireless data rates of 1.6 and 0.8 gigabits per second (Gb/s) at distances of 0.4 and 1 m with 256-quadratic-amplitude modulation (QAM) and 16-QAM modulated signals, respectively.

Optically Synchronized Phased Arrays in CMOS

Optical synchronization of large-span arrays offers significant benefits over electrical methods in terms of the weight, cost, power dissipation, and complexity of the clock distribution network. This work presents the analysis and design of the first phased array transmitter synchronized using a fully monolithic CMOS optical receiver. We demonstrate a bulk CMOS, 8-element, 28-GHz phased array building block with an on-chip photodiode (PD) that receives and processes the optical clock and uses an integrated PLL to generate eight independent phase-programmable RF outputs. The system demonstrates beam steering, data transmission, and remote synchronization of array elements at 28 GHz with fiber lengths up to 25 m, in order to show the scaling benefits of our approach. The provision of small footprint and cost-effective CMOS transceivers with integrated optoelectronic receivers enables exciting opportunities for low-cost and ultralight array systems.

A Ku-Band Eight-Element Phased-Array Transmitter With Built-in Self-Test Capability in 180-nm CMOS Technology

In this article, a CMOS <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band phased-array transmitter with eight elements is demonstrated. To mitigate the measurement time and complexity, a built-in self-test (BIST) circuit is developed in this chip. A fully symmetrical sampling structure is proposed to improve the testing accuracy of the BIST system. To decrease the phase and amplitude errors, two compensation methods based on inductors and capacitors are, respectively, used in the phase shifters and attenuators to minimize severe parasitic effects of transistors in high-frequency bands. In addition, a scalable power divider is developed to save chip area and reduce insertion loss. According to the measurement results, the 5-bit passive phase shifter in each transmitting channel achieves less than 3.6° root-mean-square phase error (RMSPE) and 0.8-dB root-mean-square amplitude error (RMSAE). The transmitter’s attenuators are formed by four bridge- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T/\pi $ </tex-math></inline-formula> -type units and achieve less than 0.94-dB RMSAE and RMSPE of 3.2°. Each channel of the transmitter is capable of delivering about 13-dBm linear power at 16 GHz. The BIST system is also employed to detect the phase and amplitude performances of the eight-element transmitter, and the BIST testing errors are less than 10.3% compared to the microwave equipment measurement.

A 27–31-GHz 1024-Element Ka-Band SATCOM Phased-Array Transmitter With 49.5-dBW Peak EIRP, 1-dB AR, and ±70° Beam Scanning

This article presents a wideband scalable 27–31-GHz 1024-element <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Ka$ </tex-math></inline-formula> -band SATCOM transmit (TX) phased array with embedded RF drivers and reconfigurable polarization. The phased array uses silicon TX beamformer (BF) chips and printed stacked-patch antennas on an FR-4 based printed circuit board (PCB) to TX either linear, rotated linear, circular clockwise, or anticlockwise polarization. It demonstrates a measured 3.5° half-power beamwidth (HPBW), 35-dB cross-polar discrimination (XPD), sub-1-dB axial ratio (AR), +49.5-dBW peak effective isotropic radiated power (EIRP) on axis, and the ability to scan to ±70° in all planes without grating lobes and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$cos^{1-1.1}(\theta)$ </tex-math></inline-formula> scan loss. The measured error vector magnitude (EVM) of less than 2.3% and the adjacent channel power ratio (ACPR) of less than −32 dBc across all scans at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{1\,\text{dB}}$ </tex-math></inline-formula> make it suitable as a compact high-efficiency SATCOM transmitter. The array aperture measures 14.9 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times14.9$ </tex-math></inline-formula> cm, and it is scalable to larger phased arrays with 4096 and a higher number of elements. To the best of our knowledge, this represents the highest level of integration at millimeter waves and with the highest measured EIRP from a SATCOM phased array.

Comparison of Over-the-Air Efficiency Enhancement Techniques in Linear Phased Arrays

This article reviews the recent advancements in the utilization of over-the-air combining techniques to enhance the efficiency of phased-array transmitters for signals with a high peak-to-average-power ratio. A methodological comparison between three spatial over-the-air combining techniques--Doherty, outphasing, and quadrature combining--is proposed, along with analysis of their spatial properties, such as a beamwidth angle for a given error vector magnitude (EVM) value, directivity, out-of-band emission, and sensitivity to amplitude and phase mismatches between the different streams. The analysis suggests that the Doherty technique has the widest spatial angle range with EVM under -30 dB and the lowest sensitivity to mismatches, while quadrature combining exhibits the lowest adjacent channel power ratio (ACPR). Also, the Doherty technique enables the largest efficiency enhancement and allows to trade off efficiency enhancement for out-of-band emission. The different methods were tested over-the-air at 28 GHz with a four-element integrated phased array fabricated in 65 nm to validate the analysis.

Highly non‐linear and wide‐band mmWave active array OTA linearisation using neural network

This paper proposes a neural network (NN)-based over-the-air (OTA) linearisation technique for a highly non-linear and wide-band mmWave active phased array (APA) transmitter and compares it with the conventional memory polynomial model (MPM)-based technique. The proposed NN effectively learns the distinctive non-linear distortions, which may not easily fit to existing MPM solutions, and can, therefore, successfully cope with the challenges introduced by the high non-linearity and wide bandwidth. The proposed technique has been evaluated using a state-of-the-art 4 × 4 APA operating in highly non-linear regions at 28 GHz with a 100-MHz-wide 3GPP base-station signal as input. Experimental results show the pre-distortion signal generated by the NN exhibits the peak-to-average power ratio (PAPR) much lower than the one generated by MPM and consequently superior linearisation performance in terms of adjacent channel leakage ratio (ACLR) and error vector magnitude (EVM) for high non-linearity cases. Using the proposed NN-based linearisation technique, an improvement of 5-dB ACLR and 7% points in EVM are achieved, which demonstrates the promising potential of this technique for emerging broadband communication systems such as 5G/6G and low Earth orbit (LEO) satellite networks.

A 4-Element Digital Modulated Polar Phased-Array Transmitter With Phase Modulation Phase-Shifting

A novel architecture of a digital modulated polar phased-array transmitter with phase modulation (PM) phase-shifting and feed-forward controlled dynamic matching (FFCDM) is presented in this article. Phase-shifting in a PM signal path is utilized in each element, which shares many components including a phase modulator, baseband, and IF components. The characteristics of the proposed architecture are analyzed. With a constant envelope of PM signals, the implicit nonlinearity of the phase shifter in this architecture has low impact on the linearity performance of a phased-array system. Meanwhile, low phase error can be achieved by high-resolution phase interpolation with the digital predistortion (DPD) technique. Efficiency for both saturated and 6-dB back-off power is enhanced by digital power amplifier (DPA) with FFCDM. As a proof of concept, a 3–7 GHz 4-element phased-array transmitter is designed and fabricated in 40-nm CMOS based on the proposed method. The measured root-mean-square (rms) phase error of 0.3°, effective phase shifting resolution of 9-bit, and peak system efficiency of 38.2% are achieved. For 40 MHz 64-QAM modulation signal, it exhibits EVM of 5.38% and 5.37%, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\text {out}}$ </tex-math></inline-formula> of 14.30 and 14.46 dBm, and PAPR of 7.08 and 6.97 at 3.5 and 5.2 GHz, respectively. The measured peak EIRP is 35.6 dBm with a unit antenna gain of 2.98 dBi at 5 GHz. The radiation patterns with 0°, 15°, 30°, and 45° steering are measured based on monopole antennas. Meanwhile, the array achieves < 4.7% and < 5.9% EVM for 64-QAM signals with bandwidths of 20 and 40 MHz, respectively.

Combined Sidelobe Reduction and Omnidirectional Linearization of Phased Array by Using Tapered Power Amplifier Biasing and Digital Predistortion

Power amplifier (PA) efficiency and linearity are among the key drivers to reduce energy consumption while enabling high data rates in the fifth-generation (5G) millimeter-wave phased array transmitters. Analog per-branch phase and amplitude control is used to steer the beam, suppress the sidelobes, and form zeros to the desired spatial directions. The amplitude control of individual PA inputs makes nonlinearity vary from antenna to antenna, which challenges the common digital predistortion (DPD) used to linearize the array. In this article, we implement an amplitude control for beamforming by tuning the PA gate bias. Varying the output powers via PA biasing makes the nonlinear characteristics observed at the individual PA outputs similar that helps the array DPD to linearize also individual PAs. The technique is validated by both simulations and measurements. As a measurement platform, we use a 28-GHz phased array transceiver equipped with 64 antenna elements and 16 radio frequency chains. The desired beam shape is synthesized by controlling the per-antenna over-the-air-power with PA gate bias. Then, the system is linearized by training DPD with a reference antenna. The DPD is demonstrated with 100-MHz-wide 5G new radio modulated waveform. The best example case showed −23.5-dB maximum sidelobe level (SLL) with 4.9% error vector magnitude and −40.8-dB total radiated adjacent channel power ratio with DPD. The proposed approach enables simultaneous reduction of beam pattern SLL, achieves good linearity in all directions, and maintains the PA efficiency.

An Integrated 2D Ultrasound Phased Array Transmitter in CMOS With Pixel Pitch-Matched Beamforming.

Emerging non-imaging ultrasound applications, such as ultrasonic wireless power delivery to implantable devices and ultrasound neuromodulation, require wearable form factors, millisecond-range pulse durations and focal spot diameters approaching 100 μm with electronic control of its three-dimensional location. None of these are compatible with typical handheld linear array ultrasound imaging probes. In this work, we present a 4 mm × 5 mm 2D ultrasound phased array transmitter with integrated piezoelectric ultrasound transducers on complementary metal-oxide-semiconductor (CMOS) integrated circuits, featuring pixel-level pitch-matched transmit beamforming circuits which support arbitrary pulse duration. Our direct integration method enabled up to 10 MHz ultrasound arrays in a patch form-factor, leading to focal spot diameter of ∼200 μm, while pixel pitch-matched beamforming allowed for precise three-dimensional positioning of the ultrasound focal spot. Our device has the potential to provide a high-spatial resolution and wearable interface to both powering of highly-miniaturized implantable devices and ultrasound neuromodulation.

Unidirectional large-scale waveguide grating with uniform radiation for optical phased array.

Two novel waveguide gratings for optical phased array transmitters are investigated. By offsetting the grating structures along the waveguide on the upper and lower surfaces of the silicon nitride (Si3N4) waveguide, the dual-level chain and dual-level fishbone structures can achieve 95% of unidirectional radiation with a single Si3N4 layer by design. With apodized perturbation along the gratings, both structures can achieve uniform radiation without compromising the unidirectional radiation performance. In experiment, both demonstrate ∼ 80-90% unidirectionality. With further analysis, it is found that the dual-level fishbone structure is more feasible and robust to process variations in uniform radiation.

Airborne ultrasonic sensor system combined with phased array transmitter and MUSIC method for high resolution environmental recognition

Airborne ultrasonic sensor system combined with phased array transmitter and MUSIC method for high resolution environmental recognition