Phase Shift Network Research Articles

Converged OAM vortex wave generation using EBG‐loaded patch array antenna

In this article, an orbital angular momentum (OAM) patch array antenna with converged beam is proposed. The electromagnetic band gap (EBG) structure is applied to a patch array antenna with 2 × 2 elements. The array antenna is excited by a carefully designed feeding phase shift network with equal output energy for four output ports. Thus, the OAM vortex wave with topological charge l = 1 is generated. By using EBG structure around the radiating patches, the surface wave of the array antenna is suppressed. As a result, the radiation pattern is improved significantly, including the enhanced gain and reduced divergence angle. A prototype was fabricated and measured. The measurement results agree well with the simulations. Compared with the other approaches, the proposed antenna is much more compact in structure and ease of fabrication.

THz 2-D Frequency Scanning Planar Integrated Array Antenna With Improved Efficiency

A THz 2-D frequency scanning planar integrated array antenna is developed in this letter. Eight THz leaky-wave antennas are combined with a true-time-delay (TTD) phase-shifting feeding network to steer the beam in two directions by sweeping the frequency. Several H-plane 90° bends with linearly increased length are adopted to achieve the scalable TTD phase shift. The feeding lines are closely spaced to reduce the phase-shifting network occupied area in this progressive phase-shifting scheme. Besides, the E-plane 180° bend is used to construct the double-layer phase-shifting network, maintain the number of multiple scanning sweeps and improve the aperture efficiency. Moreover, in the used microelectromechanical systems (MEMS) fabrication technique, the minimum height of the radiation slot is 0.2 mm, which is too thick and deteriorates the radiating performance. When the double-layer step-profiled radiating slot is used instead of the thick slot, a THz leaky-wave antenna with higher radiation efficiency and better gain flatness can be achieved. Finally, a prototype antenna is fabricated and experimentally validated. The operating frequency range is 325-400 GHz and the beam scanning range is 22.7° × 60° with a maximum radiation gain of 25.28 dBi.

Adaptive Cross Entropy-Based Kalman Filter Hybrid Precoding For Frequency Selective mmWave MIMO Channel: Time Domain approach

In Millimetre Wave (mmWave) Multiple-Inputs Multiple-Output (MIMO) systems, hybrid precoders are introduced the reduced number of Radio Frequency (RF) chains. In the existing hybrid precoder using Phase Shifter (PS) network consume high energy, the cost of hardware and the performance loss in the system is high. In this paper, Adaptive Cross-Entropy (ACE) based Kalman Hybrid Precoder for the frequency selective mmWave MIMO channel in time domain approach is proposed. ACE based kalman hybrid precoder is designed and develops for Switch and Inverter (SI) based architecture. In addition, Kalman based digital precoder is develop and compare with MMSE digital precoder. Simulation results show the ACE based kalman hybrid precoding for SI architecture is provide the low energy consumption, and higher Spectral Efficiency (SE) compares to the existing Two-Stage (TS) hybrid precoder, Antenna Selection (AS) and Cross-Entropy (CE) based hybrid precoders.

Joint Symbol Level Precoding and Combining for MIMO-OFDM Transceiver Architectures Based on One-Bit DACs and ADCs

Herein, a precoding scheme is developed for orthogonal frequency division multiplexing (OFDM) transmission in multiple-input multiple-output (MIMO) systems that use one-bit digital-to-analog converters (DACs) and analog-to-digital converters (ADCs) at the transmitter and receiver, respectively, as a means to reduce the power consumption. Two different one-bit architectures are presented. In the first, a single user MIMO system is considered where the DACs and ADCs of the transmitter and the receiver are assumed to be one-bit and in the second, a network of analog phase shifters is added at the receiver as an additional analog-only processing step with the view to mitigate some of the effects of coarse quantization. The precoding design problem is formulated and then split into two NP-hard optimization problems, which are solved by an algorithmic solution based on the Cyclic Coordinate Descent (CCD) framework. The design of the analog post-coding matrix for the second architecture is decoupled from the precoding design and is solved by an algorithm based on the alternating direction method of multipliers (ADMM). Numerical results show that the proposed precoding scheme successfully mitigates the effects of coarse quantization and the proposed systems achieve a performance close to that of systems equipped with full resolution DACs/ADCs.

Energy-Efficient Hybrid Symbol-Level Precoding for Large-Scale mmWave Multiuser MIMO Systems

We address the symbol-level precoding design problem for the downlink of a multiuser millimeter wave (mmWave) multiple-input multiple-output (MIMO) wireless system where the transmitter is equipped with a large-scale antenna array. The high cost and power consumption associated with the massive use of radio frequency (RF) chains prohibit fully-digital implementation of the precoder, and therefore, we consider a hybrid analog-digital architecture where a small-sized baseband precoder is followed by two successive networks of analog on-off switches and variable phase shifters according to a fully-connected structure. We jointly optimize the digital baseband precoder and the states of the switching network on a symbol-level basis, i.e., by exploiting both the channel state information (CSI) and the instantaneous data symbols, whereas the phase-shifting network is designed only based on the CSI due to practical considerations. Our approach to this joint optimization is to minimize the Euclidean distance between the optimal fully-digital and the hybrid symbol-level precoders. Remarkably, the use of a switching network allows for power-savings in the analog precoder by switching some of the phase shifters off according to the instantaneously optimized states of the switches. Our numerical results indicate that, on average, up to 50 percent of the phase shifters can be switched off. We provide an analysis of energy efficiency by adopting appropriate power dissipation models for the analog precoder, where it is shown that the energy efficiency of precoding can substantially be improved thanks to the phase shifter selection approach, compared to the fully-digital and the state-of-the-art hybrid symbol-level schemes.

Circularly Polarized Dual Band Dual Slot Antenna for WLAN, Wi-MAX and Wi-Fi Applications

In the last 15 years, the growth in the modern wireless communication systems has motivated enlarged exploration on inexpensive circularly polarized dual band slot antennas. A simple circularly polarized dual band dual slot antenna for WLAN, Wi-MAX and Wi-Fi applications is designed and analyzed. The proposed CP dual band antenna contains a radiating rectangular patch with two slots on low cost FR4-substrate having thickness of 1.6 mm. The CP dual band antenna is capable of resonating between 3.35 to 3.9 GHz and 4.8 to 6 GHz with S11 below −11 dB value. The proposed antenna exhibits the axial ratio value less than 3 dB in the two bands. This antenna utilizes single offset microstrip line feed and does not require any complicated phase shift network to provide 90° excitation phase difference. Hence this antenna can be used to form larger arrays to achieve higher gain. The antenna performance is significantly affected by the dimensions of the slots. The projected antenna is optimized using the ansoft HFSS. The antenna is fabricated to test the performance. The antenna exhibits adequate gain at the two bands. There is reasonable agreement between the simulated results and measured values.

Broadband Dual-Polarized Endfire Array With Compact Magneto-Electric Planar Yagi Antenna for mm-Wave Terminals

Based on a newly proposed planar Yagi antenna with magnetic and electric dipoles, a compact 1×4 broadband dual-polarized (DP) array with endfire radiation is designed in this paper. The magnetic Yagi antenna operates on the vertical polarization while the electric one operates on the horizontal one. The compact configuration of 0.5 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.63 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.09 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> benefits from the novel half-mode magnetic Yagi antenna and the arrangement with the electric Yagi antenna. The broadband characteristic comes from the directors of the magnetic and electric Yagi antennas and the reflector of magnetic Yagi antenna. The simulation and the measurement verify this design. The measured common bandwidth of |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB for both polarization ports is 23.8-30.1 GHz (23.7%), and the gains vary between 3 dBi and 4 dBi within 24.2-30 GHz band range. The 1×4 DP array with 0.5 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> element space has the beam scanning range of ±43 ° at the endfire direction and the gain of higher than 7.1 dBi. The scanning performances are experimentally validated by two phase-shift feed networks for 0 ° and 30 ° main beam directions. The proposed endfire DP array has the good features of compact structure, a low profile and no clearance requirement, which is easy to integrate in 5G terminals.

An Energy-Efficient Hybrid Precoding Design in mmWave Massive MIMO Systems

The hybrid precoding (HP) technique has been widely considered as a promising approach for millimeter wave communication systems. In general, the existing HP structure with a complicated high-resolution phase shifter network can achieve near-optimal spectral efficiency, however, it involves high energy consumption. The HP architecture with an energy-efficient switch network can significantly reduce the energy consumption. To achieve maximum energy efficiency, this paper focuses on the HP architecture with switch network and considers a novel adaptive analog network HP structure for such mmWave MIMO systems, which can provide potential array gains. Moreover, a multiuser adaptive coordinate update algorithm is proposed for the HP design problem of this new structure. Simulation results verify that our proposed design can achieve better energy efficiency than other recently proposed HP schemes when the number of users is small.

A single fed wideband mode‐reconfigurable OAM metasurface CP antenna array with simple feeding scheme

In this paper, a low-profile mode reconfigurable orbital angular momentum (OAM) circular polarization (CP) array antenna is presented, which consists of 2 × 2 elements and a single feed network. Each element is a metasurface subarray composed of 4 × 4 square patchs. The vias in the subarray produces 90° phase difference between x- and y- polarizations, and CP is realized. Both the 90° phase-shifting reconfigurable feed network and broadband 180° phase shift by the mirror images are used to generate the OAM helical phase. The OAM modes l can be dynamically switched between l = +1 and l = −1 by controlling operation states of p-i-n diodes in the feed network. The CP and OAM impedance bandwidths are 13.3% (from 5.8 to 6.6 GHz). The peak gains for the two modes are 9.4 dBi. The developed array antenna has the following advantages of the least pin diode number, high gain, small size, lowest divergence angle, wideband CP, low cross-polarization and low fabrication cost. Therefore, the proposed antenna is very promising for modern high-speed and large capacity wireless communication systems.

Dynamic Hybrid Precoding Relying on Twin- Resolution Phase Shifters in Millimeter- Wave Communication Systems

Hybrid analog/digital precoding in millimeter-wave (mmWave) multi-input multi-ouput (MIMO) systems is capable of achieving the near-optimal full-digital performance at reduced hardware cost and power consumption compared to its full-RF digital counterpart. However, having numerous phase shifters is still costly, especially when the phase shifters are of high resolution. In this paper, we propose a novel twin-resolution phase-shifter network for mmWave MIMO systems, which reduces the power consumption of an entirely high-resolution network, whilst mitigating the severe array gain reduction of an entirely low-resolution network. The connections between the twin phase shifters having different resolutions and the antennas are either fixed or dynamically configured. In the latter, we jointly design the phase-shifter network and the hybrid precoding matrix, where the phase of each entry in the analog precoding matrix can be dynamically designed according to the required resolution. This method is slightly modified for the fixed network's hybrid precoding matrix. Furthermore, we extend the proposed method to multi-user MIMO systems and provide its performance analysis. Our simulation results show that the proposed dynamic hybrid precoding method strikes an attractive performance vs. power consumption trade-off.

Generation and Beam Steering of Arbitrary-Order OAM With Time-Modulated Circular Arrays

In contrast to the popular multimode orbital angular momentum (OAM) generation method that uses uniform circular array combined with phase shifter network, time-modulated circular array (TMCA) does not require multiple radio frequency chains and costly analog devices and it requires only switches. In this article, an arbitrary-order OAM generation and beam steering method for TMCA is proposed, which incorporates the existing integer-order OAM generation and beam steering method as a special case. Furthermore, we analyze the effect of elements <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> – <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> ordering on the generation of OAM beams, and prove that sequential ordering has the lowest power consumption. Finally, the effectiveness of the proposed methods is validated through electromagnetic simulations.

A Square-Shaped Microstrip Antenna With Frequency and Circular-Polarization Reconfigurability: An Approach [Antenna Applications Corner

In this article, the design of a frequencyswitchable, square-shaped microstrip patch antenna with simultaneous circular-polarization (CP) reconfigurability is presented and experimentally verified. From the measurement of a fully functional prototype, it is confirmed that the resonant frequency of the proposed antenna can be continuously altered between 1.97 and 2.42 GHz by electronically varying its effective length. A wideband 90° phase-shifting and switching network is also designed to excite the antenna for generating CP radiation at all the tunable frequencies and altering the sense of rotation [both left-hand CP (LHCP) and right-hand CP (RHCP)]. More importantly, the antenna shows an axial ratio (AR) value that is less than 3 dB within a wide beamwidth (130-150°) at all the tuning states, and it has a maximum realized gain of 5.8 dB isotropic circular (dBic) at 2.42 GHz. The frequency with CP-reconfiguring characteristics makes the proposed antenna suitable for advanced wireless communication systems operating in the S-band, which can withstand both frequency-based challenges and signal-quality issues arising due to climatic changes.

DESIGN OF CHANNEL FEED-BACK CODEBOOK AND ADDRESSING POWER LEAKAGE PROBLEM IN MM- WAVE MASSIVE MIMO SYSTEM WITH LENS ANTENNA ARRAYS

Objective The modernistic theory of beamspace MIMO, which involves millimeter wave (mm-Wave) and massive MIMO system depending on lens antenna array (LAA) can efficiently decrease the count of power consuming radio frequency (RF) chains. Hence, it is perceived as an optimistic approach for the 5G technology and its successors. Research in beamspace (BmSp) MIMO has yet to be taken into debate the issues of power leakage in channels, therefore resulting in remarkable deterioration in SNR and the sum-rate (SR). A precoding technique for beam aligning and to tackle power leakage issue has been proposed. Initially a network using phase shifters has been designed, which helps RF chains choose beams and collect leaked power in beamspace MIMO. An algorithm based on rotation for precoding, for the available phase shift networks is proposed to align the gains of the channels in the same direction to maximize SNR received by the users. In systems that employ frequency division duplexing (FDD), it is necessary that the channel is fed back to the base station (BS) via feedback based on codebook. There is no devoted codebook for the LAA dependent mm-Wave systems. The codebook design is proposed to address the gap for these systems. In this codebook, initially a large dimension vectors based on recent idea involving angle coherence time are generated. Then relying on obtained vectors in channel subspace, codebook is created by considering lens and beam selection. After that the channel is quantized and given as feedback to the BS. Results Simulation results conveys that the overhead in feedback is proportional to dominant paths for each user which are few and the proposed approach with uniform linear array (ULA) attains the near optimal performance in SR comparing to ideal case of zero power leakage and also obtains superior Energy efficiency (EE) than existing single beam precoding and Multiple beam via multiple RF (MBMRF) structure precoding methods.

Generating the dual‐band and multimode OAM by irregular pentagonal patch antenna array

This Letter presents an irregular pentagonal patch array antenna with a multilayer structure for dual-band and multimode orbital angular momentum (OAM) generation. An irregular pentagonal patch antenna with U-shaped slots resonating at different frequencies is designed as the array's element. The proposed antenna array consists of two uniform circular microstrip antenna arrays and two phase-shifting feeding networks. It can be used to generate OAM mode l = − 1, 1 at 3 GHz and OAM mode l = −2, 2 at 6 GHz. The simulated near-field phase distributions images of different OAM modes are obtained, which have verified the OAM generation. This proposed array antenna has the possibility to generate a total of six different OAMs in three frequency bands, by changing the number of array elements and optimising the irregular pentagonal patch antenna. This design may provide a new idea for the generation multimode vortex electromagnetic wave.

Ultrawideband Reflection-Type Metasurface for Generating Integer and Fractional Orbital Angular Momentum

Vortex beams carrying orbital angular momentum are extensively studied owing to its potential to expand channel capacity of microwave and optical communication. By utilizing the Pancharatnam-Berry phase concept, an ultra-wideband single layer metasurface is proposed to realize the conversion from incident plane waves to reflected vortex beams covering a considerable bandwidth from 6.75 to 21.85 GHz . An equivalent circuit model combined with broadband phase shift network is developed to effectively design the meta-atoms in metasurface. It is the first time to design wideband metasurfaces with the phase-based characteristics. To verify the proposed model, some deformed square loop meta-atoms are proposed to construct the metasurfaces with broadband OAM characteristic. Moreover, the vortex beams with the integer (l = -3), fractional (l = -1.5), and high-order (l = -10) OAM mode are generated respectively. Based on an OAM spectral analysis, the mode purity of the generated vortex waves is discussed in detail. The experimental results achieve a good agreement with those obtained from the simulation, thus proving the effectiveness and practicability of the proposed method.

Miniaturized array antenna with reduced beam squinting

In this paper, we propose a novel multi-band series-fed array of patch antennas, a three-element linear resonant array operating at five distinct frequencies. A wide-band phase-shifting network compensates for the inter-element phase differences of radiating elements, which results in the reduction of beam squinting over the operating frequency range. Compared to a resonant series-fed array with conventional phase-shifters, beam squinting is reduced by 70%. Also, the length of the suggested phase shifters is less than quarter wave-length (at f = 6.78 GHz). Size reduction of the radiating elements also contributes to the miniaturization, and compared to a conventional array of printed dipoles, directive radiation is obtainable with fewer radiating elements. Based on the two-port network model for radiating patches, a practical computational method—which results in the usage reduction of computational resources—is presented to calculate the final realized gain of the series-fed arrays. The proposed array operates within 5.4–7.45 GHz frequency range, which makes it suitable for current and future Wi-Fi, or mobile network applications. Besides, the design principles apply to any series-fed array antenna operating at dominant (TM010) resonant mode. The performance of the proposed array is validated via experimental measurements, and the results indicate a good agreement with the simulations.

Polarization Agile Antenna for Underwater Communication Using Integrated Power Divider and Phase Shifter

This paper presents a polarization agile antenna design that can be helpful for underwater communication, using the integrated structure of power divider and phase shifter to feed a square patch antenna. The purpose of this research is to discover new ways of communication by developing a polarization agile antenna, integrated feeding structure that can generate two equal-amplitude signals with fast phase switching between $$90^{\circ }$$ and $$270^{\circ }$$ , realizing the agility control for the dual circular polarization of the square patch antenna. Compared with the traditional polarization-agile antennas with the individual power divider and phase shifter networks, the proposed design has the advantages of good amplitude, phase and polarization imbalance performances, a simple control circuit, low insertion loss, and compact design which proves it to be best underwater communication.

Compressive Sensing Based Channel Estimation for Millimeter-Wave Full-Dimensional MIMO With Lens-Array

Channel estimation (CE) for millimeter-wave (mmWave) lens-array suffers from prohibitive training overhead, whereas the state-of-the-art solutions require an extra complicated radio frequency phase shift network. By contrast, lens-array using antenna switching network (ASN) simplifies the hardware, but the associated CE is a challenging task due to the constraint imposed by ASN. This paper proposes a compressive sensing (CS)-based CE solution for full-dimensional (FD) lens-array, where the mmWave channel sparsity is exploited. Specifically, we first propose an approach of pilot training under the more severe haraware constraint imposed by ASN, and formulate the associated CE of lens-array as a CS problem. Then, a redundant dictionary is tailored for FD lens-array to combat the power leakage caused by the continuous angles of multipath components. Further, we design the baseband pilot signals to minimize the total mutual coherence of the measurement matrix based on CS theory for more reliable CE performance. Our solution provides a framework for applying CS techniques to lens-array using simple and practical ASN. Simulation results demonstrate the effectiveness of the proposed scheme.

Hybrid precoding based on adaptive RF-chain-to-antenna connection for millimeter wave MIMO systems

Hybrid precoding has recently received significant attentions as a promising alternative to fully digital precoding. The existing hybrid precoding architectures can be classified into two categories: fully-connected (FC) and partially-connected (PC) phase shifter (PS) network structures (FC-PS and PC-PS structures). However, the FC-PS structure involves a large number of PSs which leads to a prohibitive power consumption, and the PC-PS structure suffers from a severe spectral efficiency loss in spite of low power consumption. This paper considers a novel adaptive RF-chain-to-antenna connection based on switch network (AC-S) hybrid precoding architecture, which consists of a digital precoder, an analog switch network and an analog PS network. The advantage of the proposed architecture lies in achieving a satisfactory spectral efficiency while maintaining a relatively low power consumption due to the adaptive connection from a radio frequency (RF) chain to all antennas via a switch network. Based on the aforementioned architecture, an effective hybrid precoding algorithm is presented. In the proposed algorithm, the analog PS precoding matrix, the analog switch precoding matrix and the digital precoding matrix are optimized via a block coordinate descent method, and a stable solution can be obtained by several iterations. Simulation results demonstrate that the proposed algorithm with the AC-S structure not only obtains considerably better spectral efficiency than the PC-PS structure but also offers a lower power consumption than the FC-PS structure.

Calibration of Phase Shifter Network for Hybrid Beamforming in mmWave Massive MIMO Systems

For the millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems, hybrid beamforming has been proposed to reap a great gain of the large number of antennas with a limited number of radio frequency (RF) chains. The hybrid beamforming relies on a phase shifter network (PSN) in the RF domain to steer the signal power along the desired direction (or subspace). However, the RF circuits connecting the antennas and the RF chains can introduce distinct phase deviations, which need to be calibrated for the effective hybrid beamforming. This paper develops two novel approaches to the estimation and calibration of the PSN in mmWave massive MIMO communication systems under line-of-sight (LOS) and non-LOS channel scenarios. Specifically, we formulate the core phase deviation estimation problem in the calibration task as an optimization program with constant modulus constraints. Efficient algorithms are then developed to estimate the phase deviations that need to be calibrated. To gauge the performance of the proposed schemes, we also derive the Cramer-Rao lower bounds (CRLBs) for the phase estimates. The numerical results validate the effectiveness of our approaches by showing that the proposed algorithms yield estimates whose mean squared errors (MSEs) are close to the CRLBs.