Four-element Antenna Array Research Articles

A Near-Zero Refractive Index Meta-Surface Structure for Antenna Performance Improvement

A new meta-surface structure (MSS) with a near-zero refractive index (NZRI) is proposed to enhance the performance of a square loop antenna array. The main challenge to improve the antenna performance is increment of the overall antenna volume that is mitigated by assimilating the planar NZRI MSS at the back of the antenna structure. The proposed NZRI MSS-loaded CPW-fed (Co-Planar Waveguide) four-element array antenna is designed on ceramic-bioplastic-ceramic sandwich substrate using high-frequency structure simulator (HFSS), a finite-element-method-based simulation tool. The gain and directivity of the antenna are significantly enhanced by incorporating the NZRI MSS with a 7 × 6 set of elements at the back of the antenna structure. Measurement results show that the maximum gains of the antenna increased from 6.21 dBi to 8.25 dBi, from 6.52 dBi to 9.05 dBi and from 10.54 dBi to 12.15 dBi in the first, second and third bands, respectively. The effect of the slot configuration in the ground plane on the reflection coefficient of the antenna was analyzed and optimized. The overall performance makes the proposed antenna appropriate for UHFFM (Ultra High Frequency Frequency Modulation) telemetry-based space applications as well as mobile satellite, microwave radiometry and radio astronomy applications.

A multiple antenna wireless testbed for the validation of DoA estimation algorithms

In this paper, a wireless testbed with a multiple antenna receiver is described. It comprises a rotating four-element antenna array connected to a quad radio frequency (RF) front-end, and a channel acquisition board equipped with a field programmable gate array (FPGA). The algorithms can be implemented directly on the FPGA, but they can also be tested via simulation, e.g., with Matlab, since the acquired data can be transferred from the board memory to a personal computer (PC). Moreover, the algorithm implementation on the FPGA can be done by exploiting the System Generator for DSP Xilinx tool that allows the algorithm synthesis from a Simulink block diagram. These features make the testbed useful for rapid prototyping. In particular, the presence of the rotating antenna array enables the analysis of direction of arrival (DoA) estimation techniques. We report the main results from the experimental measures conducted to characterize the hardware non idealities. We then describe a DoA estimation algorithm that has been used to compare real and simulated results. It is shown that the results are in good agreement with the simulations, also when the effect of non isotropic antenna gains and/or phase noise originated from non co-phased RF front-ends becomes considerable.

Four-element microstrip array with polarization diversity

A four-element microstrip antenna array excited with a tunable feeding network is described.The feeding network is composed of three quasi-lumped couplers and a 90° phase delay line. By controlling one dc bias, the network can provide the same amplitude and two different phase combinations, including (0°, 0°, 180°, 180°) and (0°, 90°, 180, 270°), for the four array elements. With the tunable feeding network, the excitation method of the array can be switched between sequentially rotated feed mechanism and differential-feed mechanism. A reconfigurable array prototype is constructed. Experimental results show that the array has a broadside radiation and it can provide good linear and circular polarization performances at one frequency. Simulated results are also provided to validate the designs of the microstrip antenna array with switchable polarization. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1653–1657, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27660

HIGH GAIN AND BROADBAND CIRCULARLY POLARIZED SQUARE SLOT ANTENNA ARRAY

A high-gain and low-cost circularly polarized antenna array is proposed, which consists of four sequentially rotated circularly polarized square slot antennas (CPSSA). A novel feeding network is applied to the four-element array antenna, which results in increasing the axial ratio (AR) bandwidth. The measured impedance bandwidth for VSWR < 2 is around 3.48GHz (3.75GHz»7.23GHz) exhibiting a 2.8GHz (3.8GHz»6.6GHz) 3dB axial-ratio bandwidth (ARBW) and 9.05dBic peak gain. The simulated and measured results are in good agreement with each other to verify the design.

Design and Implementation of Real-Time Software Radio for Anti-Interference GPS/WAAS Sensors

Adaptive antenna array processing is widely known to provide significant anti-interference capabilities within a Global Navigation Satellite Systems (GNSS) receiver. A main challenge in the quest for such receiver architecture has always been the computational/processing requirements. Even more demanding would be to try and incorporate the flexibility of the Software-Defined Radio (SDR) design philosophy in such an implementation. This paper documents a feasible approach to a real-time SDR implementation of a beam-steered GNSS receiver and validates its performance. This research implements a real-time software receiver on a widely-available x86-based multi-core microprocessor to process four-element antenna array data streams sampled with 16-bit resolution. The software receiver is capable of 12 channels all-in-view Controlled Reception Pattern Antenna (CRPA) array processing capable of rejecting multiple interferers. Single Instruction Multiple Data (SIMD) instructions assembly coding and multithreaded programming, the key to such an implementation to reduce computational complexity, are fully documented within the paper. In conventional antenna array systems, receivers use the geometry of antennas and cable lengths known in advance. The documented CRPA implementation is architected to operate without extensive set-up and pre-calibration and leverages Space-Time Adaptive Processing (STAP) to provide adaptation in both the frequency and space domains. The validation component of the paper demonstrates that the developed software receiver operates in real time with live Global Positioning System (GPS) and Wide Area Augmentation System (WAAS) L1 C/A code signal. Further, interference rejection capabilities of the implementation are also demonstrated using multiple synthetic interferers which are added to the live data stream.

A high-performance source of high-power nanosecond ultrawideband radiation pulses

A source of high-power nanosecond ultrawideband electromagnetic pulses is described. The 3-ns-long bipolar voltage pulse with a 90-kV amplitude is applied to the input of four-element antenna array. The effective radiation potential values EpR = 560 kV were obtained at a 100-Hz pulse repetition rate.

A Real-Time Capable Software-Defined Receiver Using GPU for Adaptive Anti-Jam GPS Sensors

Due to their weak received signal power, Global Positioning System (GPS) signals are vulnerable to radio frequency interference. Adaptive beam and null steering of the gain pattern of a GPS antenna array can significantly increase the resistance of GPS sensors to signal interference and jamming. Since adaptive array processing requires intensive computational power, beamsteering GPS receivers were usually implemented using hardware such as field-programmable gate arrays (FPGAs). However, a software implementation using general-purpose processors is much more desirable because of its flexibility and cost effectiveness. This paper presents a GPS software-defined radio (SDR) with adaptive beamsteering capability for anti-jam applications. The GPS SDR design is based on an optimized desktop parallel processing architecture using a quad-core Central Processing Unit (CPU) coupled with a new generation Graphics Processing Unit (GPU) having massively parallel processors. This GPS SDR demonstrates sufficient computational capability to support a four-element antenna array and future GPS L5 signal processing in real time. After providing the details of our design and optimization schemes for future GPU-based GPS SDR developments, the jamming resistance of our GPS SDR under synthetic wideband jamming is presented. Since the GPS SDR uses commercial-off-the-shelf hardware and processors, it can be easily adopted in civil GPS applications requiring anti-jam capabilities.

Improved IC Production Yield by Taking Into Account the Electromagnetic Interference Level During Testing

This paper presents a novel method for detecting test errors in radio frequency integrated circuit (RFIC) autotest-equipment (ATE) caused by electromagnetic interferences. A sensor for measuring ambient electromagnetic (EM) signals was used to determine whether interference was the cause of the reported testing error. Upon detecting a testing error, a retest procedure was actuated to recover the testing error and to improve yield loss. For theoretical validation, Monte Carlo procedure was applied in a “source-path-victim” model to simulate the effect of electromagnetic interference (EMI) on RFIC measurement. Finally, a four-element dual-band antenna array design printed onto an ATE load board is proposed. Both the numerical and measurement results validate the effectiveness of the proposed method in reducing testing errors caused by interference.

Multi-antenna mobile terminal diversity performance in proximity to human hands under different propagation environment conditions

The effective diversity gain (EDG) of a four-element planar inverted-F antenna array, which operates at 3500 MHz in the proximity to one hand in data-mode grip and two hands in browsing-mode grip, is predicted using a recently developed hybrid stochastic-electromagnetic methodology. The dependency of the EDG results on the distorted radiation patterns due to the hands and on the cross-polarisation power ratio and incident wave parameters of the propagation environment is demonstrated. The results indicate that the generalised selection combining technique, i.e. by using only the best two out of four antenna elements at every channel realisation, achieves 2 dB higher EDG than the selection combining and only 1 dB less than the maximal ratio combining techniques.

INVESTIGATION OF THE CHARACTERISTICS OF BARIUM STRONTIUM TITANATE (BST) DIELECTRIC RESONATOR CERAMIC LOADED ON ARRAY ANTENNAS

We investigated a dielectric resonator ceramic microstrip patch antenna. The antenna was formed using barium strontium titanate (BST), which had a dielectric constant of 15. A new approach, i.e., the use of a high temperature dielectric probe kit, was used to determine the dielectric constant of BST. A computer simulation technology (CST) microwave studio was used to simulate the BST array antennas, taking into consideration the dielectric constant. We also measured the gain of the antennas loaded with two-, four- , and six-element arrays of the BST antenna and found that the gain of a six-element BST array antenna was enhanced by a gain of about 1.6dB over the four-element BST array antenna at 2.3GHz. The impedance bandwidths of these BST array antennas for voltage standing wave ratio (VSWR) < 2 were in the application ranges,

Performance Evaluation of a Four-Element Antenna Array with Selection Circuits for Adaptive MIMO Systems

Reconfigurable antenna arrays increase the flexibility of adaptive MIMO systems. At present, most designs have adopted antenna arrays with reconfigurable elements. However, antenna selection is also an effective method, which has not been fully investigated. In this paper, the potential benefits of a four-element antenna array with selection circuits in the UMTS band (1920–2170 MHz) are explored. The array has eight pin-diodes embedded in the feeding network to select any sub-set of elements. For evaluation, an adaptive MIMO system was set up and a measurement campaign was taken in an indoor multi-path environment. The measurements were performed over a 300 MHz bandwidth centered at 2.05 GHz, covering the UMTS band. The results show that different channel conditions prefer different antenna array configurations. Therefore, in varying channel conditions the antenna array can support antenna selection algorithms to select the best sub-set of elements to increase channel capacity.

Analysis of Phase-Conjugating Arrays in Multipath Environments

The ability of a phase-conjugating array (PCA) to reduce fading in single-reflector, dual-reflector, and blocked-line-of-sight multipath environments is presented. Compared to a reference four-element antenna array, the PCA improves worst case signal fading by as much as 39 dB. Agreement between the experimental results and a ray-tracing model is observed, verifying the model as a viable method for characterizing array performance in multipath environments.

Compact Switched-Beam Antenna Employing a Four-Element Slot Antenna Array for Digital Home Applications

In this paper a compact switched-beam antenna is proposed. The antenna is composed of a four-element antenna array based on L-shaped quarter-wavelength slot antenna elements. Such an antenna element is a planar structure and presents a directional radiation pattern in the azimuth plane. Its maximum radiation direction is toward near the direction of the open end of the slot. As a result, the open ends of the four slot antennas are arranged toward 0, pi/2, pi, and 3pi/2 , respectively. The statuses of these antennas are controlled by some diodes. Consequently, by carefully controlling the diodes, an antenna with several switchable patterns can be achieved. To prove the concept, a 2.4-2.5 GHz switched-beam antenna for WLAN applications is designed and implemented. Its size is 52 mm in square. The antenna possesses eight directional patterns and many nearly omnidirectional patterns in the azimuth plane. The experiment results fully demonstrate the performance of the proposed design. The envelope correlations and the characteristics of the designed antenna are also discussed. Due to the compact size and low manufacture cost, such a design can be a promising solution for digital home applications to overcome multipath problems and increase the transmission data rate.

Compact Corporate Power DividerUsing Metamaterial NRI-TLCoupled-Line Couplers

A low-loss, planar and compact metamaterial 1:4 corporate power divider design is presented. The power divider uses a cascade of three microstrip/negative-refractive-index transmission-line coupled-line couplers allowing it to be compact in the longitudinal direction. The fabricated prototype operates at 2.10 GHz and is 11.6 cm wide-designed for feeding a four-element patch antenna array. The 3 dB transmission bandwidth ranges from 0.73 GHz to 0.46 GHz for the various ports with a total insertion loss of 1.1 dB, good phase balance and better than 20 dB isolation among the output ports.

Experimental Study on MUSIC-Based DOA Estimation by Using Universal Steering Vector

MUSIC-based estimation of direction of arrival (DOA) using universal steering vector (USV) is experimentally studied. A four-element array antenna and a four-channel receiver are employed for the experiment. In order to improve the accuracy of DOA estimation, USV which has already included the effect of mutual coupling between array elements and effect of array elements themselves is compensated to further include the electric delay and loss of four channels in the receiver. The compensated USV (C-USV) approach proposed in this paper does not need the time-consuming measurement of array element pattern because the compensating matrix for USV is obtained by measuring the S parameters between RF input ports of the feeding cables and IF output ports of the receiver. The experimental results of MUSIC-based DOA estimation show that C-USV approach is an accurate, effective and practical method for the MUSIC-based DOA estimation.

2D Beam Scanning Planar Antenna Array Using Composite Right/Left-Handed Leaky Wave Antennas

A novel two-dimensional (2D) beam scanning antenna array using composite right/left-handed (CRLH) leaky-wave antennas (LWAs) is proposed. The antenna array consists of a set of CRLH LWAs and a Butler matrix (BM) feeding network. The direction of the beam can be scanned two-dimensionally in one plane by changing frequency and in the other plane by switching the input ports of the BM. A four-element antenna array in the microstrip line configuration operating at 10.5 GHz is designed with the assistance of full-wave simulations based on the method of moment (MoM) and the finite-element method (FEM). The antenna array is fabricated and radiation characteristics are measured. The wide range 2D beam scanning operation with the angle from -30deg to +25 deg in one plane by sweeping frequency from 10.25 GHz to 10.7 GHz and with four discrete angles of -46 deg, -15 deg, +10 deg, and +35 deg in the other plane by switching the input port is achieved.

Indirect Controlled Phased Source

We propose here a novel phase controllable oscillator to realize phase shift for the phased array. The phase of the oscillator is controlled by the phase of reference frequency of a phase locked loop. Since the reference frequency is usually lower than 100MHz, the phase shifting can be much easier, have a lower cost, and be more accurate than that in microwave phase shifters. A four-element scanning array antenna using this novel phase control technique is demonstrated with a scanning range of plusmn40deg in this letter

A beam-scanning and polarization-agile antenna array using mutually coupled oscillating doublers

In this paper, a two-dimensional mutually coupled oscillator array is studied for the application of a beam-scanning and polarization-agile antenna array. In the design of antenna array, a two-dimensional oscillator array is implemented in x-y plane, the polarization agility is provided by one dimension (or y-direction) and the other dimension (or x-direction) is for beam scanning. By properly tuning the free-running frequencies of these oscillators, the array radiation direction can be scanned at the selected polarization states including linearly polarized, left-hand and right-hand circularly polarized states. The maximal phase difference of /spl plusmn/180/spl deg/ between coupled oscillating signals is acquired by utilizing their second-harmonic signals. This then gives well-defined phase differences among oscillators for beam scanning in addition to the required quadrature phase difference for circular polarization. The performances of polarization agility and beam scanning for a four-element antenna array are verified experimentally and shown to have the potential for adaptive antenna array applications.

Investigation of a simple four-element null steering antenna array

Theoretical and experimental investigations of the radiation patterns of one-null-steering four-element antenna array are presented. This method of nulling based on controlling signal combination in the feeder network, consisting of two ring hybrid couplers with sum and difference outputs, amplifier/attenuator and power dividers, is very simple to analyse and implement and may be very effective for some applications. A null steering range of about 40° has been obtained and some difficulties with the practical realisation of this method are shown and analysed.

Planar array antenna using both‐sided MIC's feeder circuits

AbstractIn this paper, it is proposed that the “both‐sided” circuit technique, which consists of placing several types of transmission lines on both sides of the dielectric substrate, be used for array antenna feed systems. Microstrip lines are used on the front surface of the dielectric substrate, and slot lines are placed on the back side. By means of electromagnetic coupling, a new feed system is constructed. Further, trial fabrication and testing of a four‐element array antenna using this feed system were carried out. The measured radiation patterns indicate complementary effects caused by feeding of the radiating elements with mirror symmetry. Excellent characteristics substantially reducing unwanted cross‐polarization are confirmed. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(7): 23–30, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10179