A High Gain Pattern Reconfigurable Micro-strip Dipole Antenna with a Gain Enhancing Partially Reflecting Surface

A beam reconfigurable antenna with high gain is presented with low complexity switching capability. The design consists of a printed dipole antenna with reconfigurable parasitic elements that are combined with a partially reflecting surface (PRS) to provide main lobe radiation pattern switching between boresight and close to end-fire at an operating frequency of 1.81GHz. The reconfigurability is achieved using only two PIN diodes and the measured gain of the antenna is 8.5dBi gain at boresight and 14.3dBi towards the end-fire direction

A Pattern Reconfigurable Microstrip Dipole Antenna with PRS Gain Enhancement

This paper investigates a low complexity high gain structure that can switch the radiation pattern from boresight to almost endfire direction. The principles of Fabry Perot, reconfigurable parasitic reflectors and partially reflective surfaces are combined to achieve the pattern reconfigurability. Two different Fabry-Perot cavity spacings are assessed and a maximum gain of 18.8 dBi is achieved at boresight which can be reduced by over 12dB with the use of PIN diode switches. Radiation towards the endfire directions has a maximum gain of 7.1dBi which can be reduced by almost 17dB with the use of the PIN diode switches. The paper presents numerical simulations of the proposed antennas

A low-loss reconfigurable frequency selective surface based antenna for direct antenna modulation

A directly modulating antenna incorporating a reconfigurable Frequency Selective Surface (FSS) for arbitrary phase modulation is designed and simulated. A 4-layer FSS is used to minimise constellation distortion, with only 1.5dB variation in transmitted magnitude for 360° phase change. Low loss substrates and Barium Strontium Titante (BST) variable capacitors are simulated to reduce the antenna loss to 1.3dB in the filter pass band and achieve an average total efficiency of 65% when producing an 8-PSK constellation

Switchable Electromagnetic Bandgap Surface Wave Antenna

This paper presents a novel switchable electromagnetic bandgap surface wave antenna that can support both a surface wave and normal mode radiation for communications at 2.45 GHz. In the surface wave mode, the antenna has a monopole-like radiation pattern with a measured gain of 4.4 dBi at ±49° and a null on boresight. In the normal mode, the antenna operates like a back-fed microstrip patch antenna

Frequency Selective Surface Loaded Antenna for Direct Antenna Modulation

A reconfigurable antenna loaded with Frequency Selective Surfaces (FSS) to achieve direct antenna phase modulation is presented and simulated. Placing FSS with integrated varactor diodes into a monopole-fed cavity allows control of the transmitted phase of a carrier signal with a bias voltage. As such, Direct Antenna Modulation (DAM) can be achieved, producing a phase modulator that can be included in a low complexity transmitter. Simulation shows such an antenna can achieve QPSK modulation with between 3.5dB and 4.5dB magnitude variation between constellation points with acceptable phase stability with radiation angle in the antenna 3dB beamwidth

Bit Error Rate Performance of Quadrature Modulation Transmission Using Reconfigurable Frequency Selective Surfaces

A low-complexity radio transmitter is implemented and evaluated using a novel direct antenna modulation (DAM) technique incorporating a reconfigurable antenna. The antenna uses reconfigurable frequency selective surfaces (FSS) to directly phase modulate a radio frequency carrier wave with a quadrature phase shift keying (QPSK) modulation. A hardware-in-the-loop demonstration of the transmitter in a single in single out (SISO) communications system has been developed. To achieve a BER of 10−4 the proposed system required only 4dBm extra transmit power compared with instrument grade transmission

Evaluation of High Impedance Surfaces for MRI RF Coil Applications ­ Simulations of RF Field and Specific Absorption Rate

This paper investigates the use of High Impedance Surfaces (HIS) to enhance the magnetic near-field within a dielectric phantom stimulated by a surface coil antenna resonating at 63.8 MHz for use in Magnetic Resonance Imaging (MRI) systems. Specifically, the optimization of the space between the surface of the coil and the HIS is presented here. The HIS incorporates interdigitated capacitive elements that produce an electrically small unit cell size. The magnetic field strength is shown to be improved by 42% as compared to a system which uses only an RF shield The associated Specific Absorption Rate (SAR) for the optimum design is simulated and compared to international standards. The work is aimed at 1.5T MRI applications

An Independently Tunable Tri-band Antenna Design for Concurrent Multi-band Single Chain Radio Receivers

In this paper, a novel tunable tri-band antenna is presented for concurrent, multi-band, single chain radio receivers. The antenna is manufactured on a 50×100 mm FR4 printed circuit board (PCB), and is able to provide three concurrent, independently tunable operating bands covering a frequency range from 600 MHz to 2.7 GHz. The antenna performance is investigated for both numerical and experimental methods when using, first, varactor diodes and, second, digitally tunable capacitors (DTCs) to tune frequencies, which shows the antenna gain can be improved by up to 2.6 dBi by using DTCs. A hardware-in-the-loop test-bed provides a system level evaluation of the proposed antenna in a direct RF digitized, concurrent, tri-band radio receiver. By measuring the receiver’s error vector magnitude, we demonstrate sufficient isolation between concurrent bands achieving 30 MHz of aggregated bandwidth as well as strong resilience to adjacent blockers next to each band. The data reported in this article are available from the ORDA digital repository (https://doi.org/10.15131/shef.data.5346295)

Concurrent, Multi-band, Single-Chain Radio Receiver for High Data-Rate HetNets

A concurrent, tunable, triple-band, single chain radio receiver for 5G radio access networks is presented and its performance is evaluated in a hardware-in-the-loop test-bed. The test-bed emulates a 5G heterogeneous network supporting three independently tunable, wideband, simultaneous connections over a frequency range from 600 MHz to 2.7 GHz. The single chain receiver is able to achieve an aggregate bandwidth of 93.75 MHz, 31.25 MHz per band, and a net data rate of 187.5 Mbit/s through the use of single-carrier QPSK transmissions. The receiver demonstrate sufficient isolation between the concurrent transmissions as well as strong resilience to adjacent blockers through the use of a small guard band

Low-profile independently- and concurrently-tunable quad-band antenna for single chain sub-6GHz 5G new radio applications

This paper presents a quad-band frequency agile antenna, with independent and concurrent frequency tunability in each band, for a tunable, concurrent, quad-band single chain radio receiver for 5G New Radio (NR). More specifically, the antenna comprises of four planar slots etched in a ground plane and fed through a single microstrip feedline, without any impedance matching network. The structure is optimized to maximize isolation between the individual slots and their respective resonant frequencies. Furthermore, a novel high order harmonic suppression method is demonstrated, which controls the current distribution via creating a fictitious short circuit in the slot antenna-enabling the antenna to achieve a much wider tuning range. Numerical simulations are verified using experimental implementation and measurements, with good agreement observed. The four slots resonate around the 830 MHz, 1.8 GHz, 2.4 GHz and 3.4 GHz frequency bands, which are independently tuned (using a varactor diode in each slot) to achieve tuning ranges of approximately 64%, 66%, 27% and 33%, respectively. More importantly, the contiguous four bands covers a total frequency tuning from 0.6 to 3.6 GHz i.e. a tuning range of approximately 143%. Finally, far-field measurements are performed and the antenna is evaluated in over-the-air testbed (quad-band radio receiver), which measures the Error Vector Magnitude performance for the individual channels. Good performance is observed, confirming acceptable isolation performance between the four bands. The data reported in this paper is available, from ORDA-The University of Sheffield Research Data Catalogue and Repository, at https://doi.org/10.15131/shef.data.11219000.v1