38 research outputs found
Flexible-Resolution, Arbitrary-Input and Tunable Rotman Lens Spectrum Decomposer (RL-SD)
We present an enhanced design -- in terms of resolution flexibility, input
port position arbitrariness and frequency-range tunability -- of the planar
Rotman lens spectrum decomposer (RL-SD). This enhancement is achieved by
manipulating the output port locations through proper sampling of the
frequency-position law of the RL-SD, inserting a calibration array compensating
for frequency deviation induced by input modification and introducing port
switching, respectively. A complete design procedure is provided and two
enhanced RL-SD prototypes, with uniform port distribution and uniform frequency
resolution, respectively, are numerically and experimentally demonstrated
Design and simulation of an analog beamforming phased array antenna
In this paper, a phased array antenna is designed and simulated. The antenna array consists of four circularly polarized slotted waveguide elements. The antenna array is simulated using CST MWS. The simulation results for the proposed antenna array at different values of progressive phase shift demonstrate that the S‒parameters for all four ports are less than ‒10 dB over at least 2% bandwidth, the simulated maximum gain is 13.95 dB, the simulated beamwidth can be 19˚ or narrower based on the value of the progressive phase shift. , the range of frequencies over which the simulated Axial Ratio (AR) is below 3 dB is not fixed and varied according to the selected progressive phase shift. The proposed four-element RF front-end is simulated using Advanced Design System (ADS) at operating frequency of 9.6 GHz. The obtained simulation results by ADS indicate the feasibility of implementing the proposed RF-front end for feeding the antenna array to realize analog beamforming
Real-Time Spectrum Sniffer for Cognitive Radio Based on Rotman Lens Spectrum Decomposer
We introduce the concept of a Rotman-lens spectrum decomposer (RLSD)
real-time spectrum-sniffer (RTSS) for cognitive radio. Compared to a previously
existing RTSS, the RLSD-RTSS offers the advantages of being 1) based an a
simpler and lower-cost purely passive structure, 2) easier to design and easily
amenable to tunability, 3) of much broader bandwidth, and 4) of accommodating
more channels. The electrical size of the device is electrically larger, but
perfectly acceptable in the millimeter-wave frequency range. The proposed
RLSD-RTSS is demonstrated theoretically and experimentally, and been shown to
support tunability in terms of both bandwidth-resolution and operation band.
Given its unique features, this device may find wide applications in 5G UHD and
3D video systems
Beam Pattern Optimization Method for Subarray-Based Hybrid Beamforming Systems
Massive multiple-input multiple-output (MIMO) systems operating at millimeter-wave (mmWave) frequencies promise to satisfy the demand for higher data rates in mobile communication networks. A practical challenge that arises is the calibration in amplitude and phase of these massive MIMO systems, as the antenna elements are too densely packed to provide a separate calibration branch for measuring them independently. Over-the-air (OTA) calibration methods are viable solutions to this problem. In contrast to previous works, the here presented OTA calibration method is investigated and optimized for subarray-based hybrid beamforming (SBHB) systems. SBHB systems represent an efficient architectural solution to realize massive MIMO systems. Moreover, based on OTA scattering parameter measurements, the ambiguities of the phase shifters are exploited and two criteria to optimize the beam pattern are formulated. Finally, the optimization criteria are examined in measurements utilizing a novel SBHB receiver system operating at 27.8 GHz
Wideband Millimeter-Wave Beam Training with True-Time-Delay Array Architecture
Millimeter-wave communications rely on beamforming gain from both
transmitters and receivers to compensate for severe propagation loss. To
achieve adequate gain, beam training is required to identify propagation
directions. The main challenge in beam training arises from maintaining low
overhead with increased array size. This paper presents a novel one-shot beam
training technique that utilizes the emerging architecture of true-time-delay
(TTD) arrays. We first show that TTD arrays facilitate frequency dependent beam
steering. The proposed training procedure with TTD arrays then exploits this
fact by using a single radio-frequency-chain to multiplex different subcarriers
into different sounding directions. We derive conditions on the parameters of
TTD array configuration and physical layer to achieve scanning of the entire
angular domain with a single orthogonal frequency-division multiplexing (OFDM)
training symbol. The estimation of propagation directions with high resolution
is achieved via low-complexity digital signal processing of spatially coded
subcarriers. Simulation results show that this TTD array based approach
requires an order-of-magnitude fewer training symbols than those of phased
arrays.Comment: 6 pages, 4 figures, paper presented in 2019 IEEE Asilomar Conference
on Signals, Systems, and Computer
Evolutionary Trends in True Time Delay Line Technologies for Timed Array Radars
Timed array technology is rapidly evolving in multiple areas such as high resolution imaging radar, automotive, medical, high data rate communication applications etc. Timed arrays by utilising True Time Delay (TTD) lines in place of phase shifters mitigate beam squint and pulse dispersion issues associated with wide instantaneous bandwidth arrays. This paper presents on review of evolutionary trends in TTD line architectures starting from coaxial cable to photonic integrated circuit. The paper also reports on critical parameters of TTD lines, their importance and implication in design of typical X-band imaging radar. Comparison of different TTD line architectures in terms of configuration, implementation, merits and demerits are discussed in detail for wideband array application. The paper also brings out the integration aspects of TTD lines as part of T/R modules and proposes suitable design schemes towards performance optimization and realisation of timed arrays
Analytical and Numerical Evaluations of Flexible V-Band Rotman Lens Beamforming Network Performance for Conformal Wireless Subsystems
This paper presents the analytical design and numerical performance evaluation of novel V-band millimetre-wave (mm-wave) beamforming networks (BFNs), based on the Rotman lens array feeding concept. The devices are intended for operation in the unlicensed 60-GHz frequency band. The primary objective of this work is to study the feasibility of designing flexible V-band beamformers, based on liquid-crystal polymer (LCP) substrates. The planar Rotman lens device has been initially developed, and the output performances, in terms of the scattering parameters and accuracy, have been analysed. This is further continued with the detailed designs of the Rotman lens BFNs based on the four different proposed flexural cases, namely the concave-axial bending, the convex-axial bending, the concave-circumferential bending, and the convex-circumferential bending. Each of the flexures has been analysed, and the performance in terms of the surface currents and phase distributions, as the primary functionality indicators, has been presented. The presented flexible beamformers exhibit significant characteristics to be potentially employed as low-cost and efficient units of the mm-wave transceivers with the in-built electronic beam steering capabilities for the conformal wireless subsystems