Active Phase Shifter Research Articles

A Novel Switch-Less Active Bi-Directional Phase Shifter With In–Out Impedance Equalization via Staggered Structure for $Ku$-Band Applications

A Novel Switch-Less Active Bi-Directional Phase Shifter With In–Out Impedance Equalization via Staggered Structure for $Ku$-Band Applications

Bidirectional 6-Bit Active Phase Shifter in W-Band

Bidirectional 6-Bit Active Phase Shifter in W-Band

Effects of second-stage active phase shifter on the inter-stage refrigeration capacity of a Stirling/pulse tube cryocooler

The Stirling/pulse tube cryocooler (SPC) is one of the most promising cryocoolers for space applications due to its advantages like high efficiency and long lifetime. The second pulse tube stage is coaxial pneumatically coupled in series with the first Stirling stage. The SPC possesses a distinctive capability to dynamically adjust the inter-stage refrigeration capacity by actively controlling the Stirling displacer in the first stage. This enables the SPC to effectively cater to varying heat loads over time. Nevertheless, the investigation into the regulation mechanism of the second-stage phase shifter on inter-stage refrigeration capacity shift is hindered by the presence of the second-stage passive phase shifter. This manuscript proposes an SPC with a second-stage active phase shifter (APS), which can actively control the phase difference between the pressure wave and mass flow at the second-stage hot end of the pulse tube in real time. The effect of the APS phase and amplitude on the inter-stage refrigeration capacity shift is analyzed using the theoretical and numerical model proven by the experiment. The first experimentally reported SPC with a second-stage APS demonstrates a refrigeration capacity of 0.22 W at 20 K plus 3.11 W at 70 K, requiring a compressor electrical power of 220 W. The SPC achieves a no-load minimum temperature of 13.5 K.

A 2.4 GHz low-power and compact 3-bit active phase shifter utilizing miller capacitance

A low-power and compact 3-bit active phase shifter is designed and implemented in a 22 nm FDSOI CMOS process. A modified inverter-based topology, which takes advantage of miller capacitance, is used to create a compact and low-power solution, resulting in ∼10× and ∼90× reduction in the power and chip area, respectively, for a given phase shift, compared to the standard inverter-based topology. At the same time, the proposed phase shifter exhibits less sensitivity to device mismatch. The proposed design measures ∼0.004 mm2, consumes 1.8 mW, and delivers up to 65°of phase shift with RMS phase and amplitude error of 3.85°and ±0.34 dB, respectively. The measured die-to-die variation is also confined to ±6.2°, which is <10% of the full range.

Compact and Low Power-Consumption Solid-State Two-Dimensional Beam Scanner Integrating a Passive Optical Phased Array and Hybrid Wavelength-Tunable Laser Diode

Large-scale optical phased arrays have attracted attention as devices for solid-state beam scanning employing light detection and ranging. However, conventional optical phased arrays using electro-optic phase shifters require active phase control for each antenna. Because the power consumption of the active phase shifters is proportional to the number of antennas, the total power consumption increases in a large-scale optical phased array with a narrow beam divergence. In this study, we propose a passive beam scanner that realizes two-dimensional beam scanning through the wavelength sweep of a laser light. Additionally, most studies on optical phased arrays use external laser diodes as light sources. This increases the size of the beam-scanning system. Therefore, there is a demand for integrating an optical phased array and a laser light source in a combined chip. In this study, we integrated a 64-channel passive optical phased array and a hybrid wavelength-tunable laser diode into a combined chip. The size of the device was 5 mm × 1.5 mm, and the power consumption for beam scanning was 49.3 mW. The field of view was 44.2° × 13.7°, and the full width at half maximum of the beam divergence was 0.517° × 3.67°. Compared with the device used in a previous study, our device was nine times smaller, and the total power consumption was only tens of milliwatts. This device consumes less power and achieves a fully integrated light detection and ranging.

Energy conversion efficiency improvement of a Stirling type PTR for dual temperature cooling by adopting two active work-recovery phase shifters

Deep space exploration is required to solve the problem of energy acquisition and efficient utilization. Improving energy conversion efficiency is vital to this issue. The Stirling type pulse tube refrigerators (PTR) that work in dual temperature zones play a pivotal role in the field of space detection, and the phase shifter of PTR profoundly affects the conversion efficiency of the exergy to cooling capacity. However, the typical phase shifter causes the acoustic power at the hot end of the cold finger to be dissipated into the form of heat, limiting energy efficiency. With the intention of improving the energy conversion efficiency in the PTR, a novel type of active phase shifter with work recovery on a dual temperature zone PTR is proposed and investigated in this article. Based on the pulse tube refrigerator with two separated cold fingers, inertance tubes with reservoirs, active piston phase shifters, and active work-recovery piston phase shifters have been comparatively investigated. While the refrigerator adopts active work-recovery piston phase shifters, a relative Carnot efficiency of 15.5% is obtained in the 35 K and 85 K temperature zones, which is the highest efficiency ever achieved in these temperature areas.

Dispersive silicon–nitride optical phased array incorporating arrayed waveguide delay lines for passive line beam scanning

As optical phased arrays (OPAs), used as solid-state beam scanning elements, swiftly stride towards higher efficiency and faster scanning speed, the line beam scanner is emerging as a viable substitute for its counterpart relying on point-beam-incorporated raster scanning. However, line-beam scanners require active phase shifters for beam scanning; thus, they consume more power and have complex device designs. This study proposes and demonstrates a dispersive silicon–nitride OPA that allows for passive wavelength-tuned steering of a line beam with an elongated vertical beamwidth. To steer the line beam passively covering the two-dimensional field of view, we deployed an array of delay lines with progressive delay lengths across adjacent channels. Furthermore, adiabatic tapers that allow precise effective array aperture adjustment are used as emitter elements to flexibly realize different vertical beamwidths. Combinations of different delay-length differences and taper tip-widths resulted in beam coverage (lateral × vertical) ranging from 6.3° × 19° to 23.8° × 40° by tuning the wavelength from 1530 to 1600 nm. The main lobe emission throughput was as small as − 2.8 dB. To the best of our knowledge, the embodied OPA is the first demonstration of a passive line beam scanner facilitating an adjustable beam coverage with quick operation and enhanced efficiency.

Design of a phased array antenna with scan loss reduction and gain enhancement by using reconfigurable subarrays

In order to reduce the scan loss and also obtain higher scanning gain for a phased array, a subarray design is proposed in this study. Different from the prior works, the number of active phase shifters utilised in this topology is identical to its counterpart without subarrays, which makes it more cost-effective. To achieve this valuable characteristic, a reconfigurable beam-former is proposed to enable the radiation pattern of a subarray to be switchable to different modes for different scanning regions. The proposed beam-former is based on substrate-integrated waveguide (SIW) and featured by extremely low-loss, due to its unique working mechanism. For validation, a fully integrated subarray module consisting of a beam-former and two Yagi-Uda antennas is designed and analysed. Furthermore, in order to show the effectiveness, five subarray modules with uniform spacing are utilised to construct a complete prototype operating at 15 GHz. Measurement results of the entire array indicate that the achieved gain is 2∼3 dB higher than its counterpart without the subarray, from −45° to +45° in the beam-scanning plane. Meanwhile, the scan loss is decreased from ±1.45 dB to smaller than ±0.9 dB. Meanwhile, sidelobe levels are also improved for scanning angles between ±45°. It should be pointed out that the proposed approach is also applicable to broaden the scanning angle of phased arrays with properly selected antenna elements. Since there is no need to increase the number of active phase shifters, this subarray-based approach can be considered more economic, and is very attractive for a variety of phased array systems.

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.

Design and Performance Investigation of a Temperature Compensated Transmitter With GaN HEMTs for Phased-Array Applications

This article presents a temperature compensated transmitter for phased-array applications. The high-temperature effects on each individual transmitter building block are studied and compensated to mitigate the performance variations. Furthermore, a new active, tunable, and variable gain phase shifter VGPS) architecture is proposed, which features low-performance variation with temperature and high gain without compromising the phase shift range. A temperature sensor is designed to adaptively adjust the critical dc bias voltages to minimize the variation of the active devices. A class- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{F}^{-1}$ </tex-math></inline-formula> power amplifier PA) is designed, as the last stage in the transmitter chain, and its performance variation is compensated through the VGPS stage by adaptively tuning its characteristics. Gallium-nitride (GaN)-on-silicon-carbide (SiC) high-electron-mobility transistors (HEMTs) are adopted as the active devices and a voltage-controlled capacitor (varactor) used in the VGPS stage. The transmitter is prototyped on a piece of Rogers 4003C substrate, and the system performance is measured. The transmitter has the minimum and the maximum small-signal gain of 5.2 and 31.5 dB, respectively, with the maximum variation of < 2.3 dB across the temperature range and the frequency range of 2–2.1 GHz. The insertion phase variation also remains below 6.5° across the phase shift, temperature, and frequency range. The maximum output power and power added efficiency (PAE) are measured to be 33 dBm and 58%, respectively, at the maximum ambient temperature of 220 °C. The measurement results also show that the transmitter is able to transmit 64-QAM signals with the data rate of 120 Mb/s at the maximum ambient temperature of 220 °C.

Development of a 2∼4 K closed-cycle JT cryocooler for space application

Cryogenic system proving cooling capacity at liquid helium temperatures is one of the key technologies for space exploration missions. A closed-cycle Joule-Thomson cryocooler capacity of providing different cooling powers at 2∼4 K is developed in our lab. The cryocooler is precooled by a two-stage thermal coupled pulse-tube cryocooler with active phase shifter and driven by multi-stage valved linear compressors. The lowest temperature about 2.5 K and more than 50 mW at about 4.0 K can be obtained by adapting the suited charging pressures. The two-stage pulse tube cryocooler can provide pre-cooling capacity at 17 K and 76 K, respectively with an input power of about 350 W. A large pressure ratio of about 26 and a mass flow rate of 6.7 mg/s can be provide by the multi-stage valved linear compressors with a charge pressure of 0.6 MPa and a total electrical power of less than 110 W. The cooling-down time for the cryocooler from room temperature to about 4 K is less than 10 hours. The cooling system can provide a required cryogenic environment for future space applications.

Wide-Angle Scanning Antennas for Millimeter-Wave 5G Applications

The fifth generation (5G) network communication systems operate in the millimeter waves and are expected to provide a much higher data rate in the multi-gigabit range, which is impossible to achieve using current wireless services, including the sub-6 GHz band. In this work, we briefly review several existing designs of millimeter-wave phased arrays for 5G applications, beginning with the low-profile antenna array designs that either are fixed beam or scan the beam only in one plane. We then move on to array systems that offer two-dimensional (2D) scan capability, which is highly desirable for a majority of 5G applications. Next, in the main body of the paper, we discuss two different strategies for designing scanning arrays, both of which circumvent the use of conventional phase shifters to achieve beam scanning. We note that it is highly desirable to search for alternatives to conventional phase shifters in the millimeter-wave range because legacy phase shifters are both lossy and costly; furthermore, alternatives such as active phase shifters, which include radio frequency amplifiers, are both expensive and power-hungry. Given this backdrop, we propose two different antenna systems with potential for the desired 2D scan performance in the millimeter-wave range. The first of these is a Luneburg lens, which is excited either by a 2D waveguide array or by a microstrip patch antenna array to realize 2D scan capability. Next, for second design, we turn to phased-array designs in which the conventional phase shifter is replaced by switchable PIN diodes or varactor diodes, inserted between radiating slots in a waveguide to provide the desired phase shifts for scanning. Finally, we discuss several approaches to enhance the gain of the array by modifying the conventional array configurations. We describe novel techniques for realizing both one-dimensional (1D) and 2D scans by using a reconfigurable metasurface type of panels.

A Multiband/Multistandard 15–57 GHz Receive Phased-Array Module Based on 4 × 1 Beamformer IC and Supporting 5G NR FR2 Operation

This work presents a 15&#x2013;57 GHz multiband/ multistandard phased-array architecture for the fifth-generation (5G) new radio (NR) frequency range 2 (FR2) bands. An eight-element phased-array receive module is demonstrated based on two four-channel wideband beamformer chips designed in the SiGe BiCMOS process and flipped on a low-cost printed circuit board. The SiGe Rx chip employs RF beamforming and is designed to interface to a wideband differential Vivaldi antenna array. Each channel consists of a low-noise amplifier (LNA), active phase shifter with 5-bit resolution, variable gain amplifier (VGA), and differential-to-single-ended stage. The four channels are combined using a wideband two-stage on-chip Wilkinson network. The beamformer has a peak electronic gain of 24&#x2013;25 dB and a 4.7&#x2013;6.2 dB noise figure (NF) with a &#x2212;29 to &#x2212;24 dBm input <inline-formula> <tex-math notation="LaTeX">$P_{\boldsymbol {1\,dB}}$ </tex-math></inline-formula> at 20&#x2013;40 GHz. The eight-element phased-array module also achieved ultra-wideband frequency response with flat gain and low-system NF. The phased array scans &#x00B1;55&#x00B0; with <inline-formula> <tex-math notation="LaTeX">$ &lt; -12$ </tex-math></inline-formula>-dB sidelobes demonstrating multiband operation. A 1.2-m over-the-air (OTA) link measurement using the eight-element Rx module supports 400-MHz 256-QAM OFDMA modulation with &#x003C; 2.76&#x0025; error vector magnitude (EVM) at multiple 5G NR FR2 bands. To the author&#x2019;s knowledge, this work achieves the widest bandwidth phased array enabling the construction of multistandard systems.

A Study on Conformal Metasurface Influences on Passive Beam Steering

Beam-steering has drawn significant interest due to the expansion of network capacity. However, a traditional beam steering system involves active phase shifters and controlling networks which can be complex. This work studied the influence of passive conformal metasurface on conventional patch antenna. The phase shifting was achieved by changing the curvature of a conformal metasurface. In addition, three low-cost conformal prototypes were fabricated and tested using different techniques such as 3D printing. The simulations and measurement results indicate up to 20° of beam shifting and reasonable gain increase. Compared with other research in the similar topic, the antenna system is completely passive, and the conformal metasurface is independent of the conventional patch antenna. Therefore, such study will be easy to implement with other antenna research especially for low power consumption beam steering systems.

Novel Passive Vector-Sum Reconfigurable Filtering Phase Shifter With Continuous Phase-Control and Tunable Center Frequency

In this article, a novel reconfigurable filtering vector-sum phase shifter (RFPS) with a continuous phase shift range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\ge 300^{\circ }$ </tex-math></inline-formula> and tunable operating frequency range from 1.05 to 1.3 GHz is proposed. It consists of two identical wideband Wilkinson power dividers (or power combiners) (WPDs) and a reconfigurable filtering quadrature coupler (RFQC) that is connected between the two WPDs. Through the first WPD, the split waves are fed into the RFQC and are then combined at the output ports of the RFQC. The phase of the combined waves can be continuously tuned by adjusting different combinations of coupling types between interstage resonators of the RFQC, and the resulted output waves are then summed up through the second WPD with the desired output phase. Different from the conventional active vector-sum phase shifter, the vector summing is realized by the proposed RFQC and is a pure passive design, resulting in a low-cost, low-noise, easy-design, and highly flexible system. A prototype is designed and fabricated to demonstrate the proposed technique. Detailed theoretical analysis and design procedure have been given. The experimental results show that the proposed RFPS features the continuous phase-control range of more than 300° with a tunable filtering response covering the frequency range from 1.05 to 1.3 GHz.

A 60-GHz Variable-Gain Phase Shifter With Particular-Sized Digital-RF Cells

A 60-GHz variable-gain active phase shifter using particular-sized digital-RF cells is proposed, which is fabricated using a 65-nm CMOS process. The phase shifter consists of an input buffer, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I/Q$ </tex-math></inline-formula> generator, and vector-summing amplifiers with digital-RF cells. In a vector-sum phase shifter using a conventional tail current steering scheme, the operation regions of vector-summing amplifiers are changed with phase and gain states. Accordingly, their input impedances are altered significantly, which causes gain and phase imbalances of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I/Q$ </tex-math></inline-formula> generator, especially around 0°, 90°, 180°, and 270°. This makes the rms phase and gain errors of the phase shifter increase. In this article, a vector-summing amplifier that always has a constant input impedance in all phases and gain states is proposed. A circular constellation and a dynamic range of more than 15 dB are implemented by using particular-sized digital-RF cells. The proposed phase shifter shows the rms gain and phase errors of < 0.29 dB and <2.01°, respectively, in a 10-GHz bandwidth of 55–65 GHz with 3-bit gain and 4-bit phase resolutions. The chip area and power consumption are 0.38 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 25.2 mW, respectively.

Nanostructured Strontium Titanate Perovskite Hyperbolic Metamaterial Supported Tunable Broadband THz Brewster Modulator

The investigation was made of nanostructured intensity and phase modulators, the designs of which are based on Brewster angle manipulation. The configuration consists of thin indium tin oxide, strontium titanate and quartz layers embedded on silicon substrate. The structure exhibits elliptical and hyperbolic metamaterial kinds, which can be manipulated by varying the ambient temperature. The design yields broadband intensity and phase modulator with 99.8% modulation depth and perfect phase shift (i.e., 180°), respectively, at the room temperature. This would find potentials in active polarization switches, modulators and tunable phase shifters operating in the THz regime.

An 18–50-GHz Δ–Σ Modulated Quasi-Continuous Digital Vector-Modulation Phase Shifter With Variable Gain Control

This letter presents a high precision wideband active vector-modulating phase shifter with high dynamic range gain control ability. Compared with conventional switching-filter phase shifter and vector-modulation phase shifter, this Δ -Σ modulated vector phase shifter can provide quasi-continuous phase and gain control capability. According to the experimental results, the dynamic range of gain control is greater than 35.5 dB. The output reflection is lower than -10 dB through the 18-50-GHz band, and the input reflection is lower than -10 dB from 18 to 45 GHz. The phase shifter occupies 700 μm x 900 μm on 0.13-μm SiGe bipolar complementary metal-oxide-semiconductor (BiCMOS) technology, and the core size is only 400 μm x 500 μm. After digital calibration, the proposed phase shifter has achieved the highest phase and gain control precision compared with the state-of-the-art digital controlled phase shifters.

Design of a Digitally Programmable Phase Shifter for Active Antenna Arrays

This paper presents the design of a new phase shifter using CMOS technology of 65 nm, for its use in arrays of antennas opperating at the millimeter band (24 GHz). It is an active phase shifter digitally programmable using a 4-bit word.

Active Terahertz Modulator and Slow Light Metamaterial Devices with Hybrid Graphene-Superconductor Photonic Integrated Circuits.

Metamaterial photonic integrated circuits with arrays of hybrid graphene–superconductor coupled split-ring resonators (SRR) capable of modulating and slowing down terahertz (THz) light are introduced and proposed. The hybrid device’s optical responses, such as electromagnetic-induced transparency (EIT) and group delay, can be modulated in several ways. First, it is modulated electrically by changing the conductivity and carrier concentrations in graphene. Alternatively, the optical response can be modified by acting on the device temperature sensitivity by switching Nb from a lossy normal phase to a low-loss quantum mechanical phase below the transition temperature (Tc) of Nb. Maximum modulation depths of 57.3% and 97.61% are achieved for EIT and group delay at the THz transmission window, respectively. A comparison is carried out between the Nb-graphene-Nb coupled SRR-based devices with those of Au-graphene-Au SRRs, and significant enhancements of the THz transmission, group delay, and EIT responses are observed when Nb is in the quantum mechanical phase. Such hybrid devices with their reasonably large and tunable slow light bandwidth pave the way for the realization of active optoelectronic modulators, filters, phase shifters, and slow light devices for applications in chip-scale future communication and computation systems.