Parasitic Antenna Elements Research Articles

Spatial Multiplexing of OFDM Signals With QPSK Modulation Over ESPAR

An electronically steerable parasitic array radiator (ESPAR) transmitter, employing one active and one parasitic antenna element, which can simultaneously transmit two orthogonal frequency division multiplexing (OFDM) signals with quadrature phase shift keying (QPSK) modulation via spatial multiplexing, is developed. In particular, a minimum mean square error (MMSE) scheme for quantizing the parasitic load impedance is developed to reduce the number of distinct load impedance values that should be realized for spatial multiplexing over ESPAR. To this end, the probability density function of the parasitic load impedance is derived, and the realizable region of the load impedance is analyzed. It is observed that the resistance of the active antenna element should be large enough to transmit OFDM signals. The characteristics of two existing ESPAR antennas with different mutual coupling matrices are examined, and it is observed that the one with the larger active antenna resistance is suitable for OFDM transmission. The bit error rate (BER) and the receive error vector magnitude performances of the proposed ESPAR systems with 6/8-bit quantizers and zero-forcing (ZF) receiver are compared with those of the corresponding ideal multiple-input multiple-output (MIMO) system through computer simulation. The results demonstrate that the performances of the proposed ESPAR with the 8-bit quantizer and the ideal MIMO systems can be almost identical, whereas the proposed ESPAR with the 6-bit quantizer exhibits some performance loss.

Analysis of resonance response performance of C-band antenna using parasitic element.

Analysis of the resonance response improvement of a planar C-band (4–8 GHz) antenna is proposed using parasitic element method. This parasitic element based method is validated for change in the active and parasitic antenna elements. A novel dual-band antenna for C-band application covering 5.7 GHz and 7.6 GHz is designed and fabricated. The antenna is composed of circular parasitic element with unequal microstrip lines at both sides and a rectangular partial ground plane. A fractional bandwidth of 13.5% has been achieved from 5.5 GHz to 6.3 GHz (WLAN band) for the lower band. The upper band covers from 7.1 GHz to 8 GHz with a fractional bandwidth of 12%. A gain of 6.4 dBi is achieved at the lower frequency and 4 dBi is achieved at the upper frequency. The VSWR of the antenna is less than 2 at the resonance frequency.

Ultra-Wideband Printed Slot Antenna With Graded Index Superstrate

An ultra-wideband (UWB) compact slot antenna with a directional radiation pattern is presented in this communication. The concept is based on dielectric loaded multi-element slot antennas. Wide bandwidth operation is achieved using a driven wide slot antenna fed via an off-centered microstrip line capable of creating a fictitious short along the slot and a number of parasitic antenna elements. The proposed slot antenna uses a graded index superstrate with tapered dielectric constants, from high index to low index , in order to further improve the bandwidth and achieve directional radiation pattern. The superstrate dimensions are carefully chosen so that a dielectric resonator mode is excited to provide radiation at the lowest frequency. A sensitivity study is carried out to optimize the geometric parameters of the slot antennas and the graded index superstrate in order to achieve the maximum bandwidth as well as an unidirectional and frequency invariant radiation pattern. Through this optimization, a compact antenna is designed, fabricated, and tested to show a VSWR value of lower than 2.5 across a 2.9:1 frequency range whose dimensions are 0.27 λ×0.2 λ×0.068 λ at the lowest frequency of operation.

Single Front-End MIMO Architecture with Parasitic Antenna Elements

In recent years, wireless communication technology has been studied intensively. In particular, MIMO which employs several transmit and receive antennas is a key technology for enhancing spectral efficiency. However, conventional MIMO architectures require some transceiver circuits for the sake of transmitting and receiving separate signals, which incurs the cost of one RF front-end per antenna. In addition to that, MIMO systems are assumed to be used in low spatial correlation environment between antennas. Since a short distance between each antenna causes high spatial correlation and coupling effect, it is difficult to miniaturize wireless terminals for mobile use. This paper shows a novel architecture which enables mobile terminals to be miniaturized and to work with a single RF front-end by means of adaptive analog beam-forming with parasitic antenna elements and antenna switching for spatial multiplexing. Furthermore, statistical analysis of the proposed architecture is also discussed in this paper.

Optimal Low Noise Single Front-End MIMO Receiver System with Parasitic Antenna Element

Optimal Low Noise Single Front-End MIMO Receiver System with Parasitic Antenna Element

On the Link Performance of a Proposed Compact Antenna System

In this paper we consider an antenna system, that consists of one active and one parasitic antenna element. Different antenna patterns may be created by loading the parasitic element with appropriate reactive impedances on each symbol period. We demonstrate the performance of a communication link that uses the proposed antenna system at the transmitter and two omnidirectional antennas at the receiver. The Arimoto-Blahut algorithm is used to find the capacity achieving distribution on the channel symbols. The capacity of the antenna system is compared to the capacity obtained by a single transmitter antenna.

Experimental Analysis of a Wideband Adaptive-MIMO Antenna

An experimental measurement campaign to investigate the wideband performance of an adaptive multiple-input multiple-output (AdaM) antenna consisting of two active and six parasitic antenna elements. The measurements are conducted over a 30 MHz bandwidth at a center frequency of 2.55 GHz and in a variety of locations in an indoor environment. The system uses a traditional two-element array at the transmitter and either a two-element traditional array or the AdaM antenna at the receiver. The results show that compared to the traditional array, the AdaM receive antenna can achieve the same throughput with an average power reduction of 2.7 dB and a maximum power reduction of 7.7 dB. The analysis further shows that the parasitic configuration works well over the entire frequency band, although improved power reduction can be obtained when the operation bandwidth is limited.

A compact broadside/endfire printed array antenna

AbstractA novel double‐layer patch array antenna is presented. The proposed antenna consists of two identical parallel layers, each containing five patch elements. The antenna is fed through one of the elements in the lower layer while other elements act as parasitic antenna elements. Both simulated and experimental results show that the proposed antenna has a relatively high gain, low side‐lobes, and improved cross polarization. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 459–461, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10950

Diversity performance analysis of two parallel dipole antennas mounted on a small metal body

AbstractDiversity technology is an effective means to improve the transmission quality in mobile communications. Hence, some portable telephones are equipped with diversity antennas. However no detailed analysis has been carried out. The reason for the low correlation coefficient of such antennas in experiments has not been clarified quantitatively.In this paper, the diversity antenna is assumed to be made of two half‐wave dipole antennas placed in parallel on a small transceiver with a rectangular shape, and its correlation coefficient and efficiency characteristics are analyzed by the method of moments using wire grid models. It is found that the correlation coefficient of 0.23 and the efficiency including the mismatch loss is −2.7 dB even for an antenna element spacing of 0.1 wavelength. Thus a sufficient diversity effect can be obtained on a small transceiver. Specifically, the reason for the low correlation coefficient is studied by separating the mutual coupling between the antenna elements and the effect of the metal body. The relationship between the incoming wave profile and the correlation coefficient is presented. It is shown that the correlation coefficient never exceeds 0.6 in an ordinary operating condition and that the correlation coefficient can be made almost 0 if the load impedance of the parasitic antenna element is chosen appropriately.