Quarter-elliptical antenna with a complementary ground slot for wideband applications

This paper presents the design of a novel compact, printed antenna with a 6dB return loss performance exceeding the 800MHz - 6GHz frequency bandwidth. This wideband operation is achieved using a planar quarter-elliptical monopole accompanied by a quarter-elliptical slot in a finite ground plane. Computer simulations show that the proposed radiating structure achieves better than 10dB return loss within the GSM, DCS, PCS, UMTS, GPS, 3.5GHz WiMAX and 5GHz WLAN bands. This performance is confirmed by measurements on the manufactured antenna which also show that the 6dB return loss reference is met between 750MHz and 6GHz. Because of its planar format, the designed antenna is suitable for integration in compact portable wireless devices aiming for multi-band support of modern wireless standards. © 2010 EuMA

Design of UWB uniplanar 180° hybrid employing ground slots and microstrip-slot transitions

The paper describes the design of a uniplanar 180° hybrid with an ultra wideband (UWB) performance. The device uses a single substrate and all its four ports are of microstripline type. Its construction is accomplished by first designing separately the out-of-phase and in-phase dividers. To merge the two devices into the hybrid, the input port of the in-phase power divider is split into two lines to overpass a ground slot in the outof- phase divider. The proposed design strategy results in the 180° hybrid exhibiting a well-balanced power division between the output ports and good quality return losses of the out-of-phase (difference) and in-phase (summation) ports across the band from 3 to 11GHz. The isolation between the difference and signal ports is excellent and the differential phase shift is also close to the ideal case of 180º and 0º across this band

Super slim multiband inverted-F antenna for GSM/DCS/PCS operation

This paper presents the design of a super slim multiband wrapped inverted-F antenna that covers the frequency bands allocated for GSM, DCS and PCS wireless services. In the first step, the quarter-wavelength size (at 850 MHz) open-end arm of an inverted-F radiator is folded and meandered. Then the antenna is wrapped using a fourth-order folding technique to reduce its projection area to only 40 x 10 x 3mm. Full wave EM simulations show that the antenna excites a lower mode resonance at about 850MHz and a higher one at about 1900MHz. Its radiation pattern is nearly omni-directional with a gain of about 2.5dBi at the lower band and 4.6dBi at the upper band. A prototype of the proposed antenna is fabricated and tested. A close agreement between simulated and measured result is achieved. The measured 6-dB return loss or VSWR 3:1 bandwidths for the lower and upper resonances are 200MHz (770 to 970 MHz) and 280MHz (1710 to 1990 MHz) respectively. These bandwidths are sufficient to cover GSM 850/900/1800/1900MHz, DCS 1800MHz and PCS 1900MHz bands. Because of its compact volume the proposed antenna is a very attractive candidate for modern slim size portable transceivers

Performance of block diagonalization scheme for various array antennas in multiuser MIMO system

This paper reports the performance of Block Diagonalization (BD) scheme for different array antenna structures used in a multiuser Multiple Input Multiple Output (MIMO) system. The assessment is performed in terms of sum rate capacity. Theoretical analysis as well as computer simulations shows that the spatial correlation downgrades downlink performance of BD. The simulations also reveal that the system equipped with Uniform Circular Array (UCA) has a better performance than the one employing Uniform Linear Array (ULA). © 2010 IEEE

BER performance of MIMO system employing fast antenna selection scheme under imperfect channel state information

In this paper, a closed-form expression for Bit Error rate (BER) of a Multiple-Input Multiple-Output (MIMO) system employing the Minimum Mean Square Error MMSE channel estimation method is derived. The numerical results show that when the Channel State Information (CSI) is free of estimation errors BER decreases when the number of receive antennas increases. However under imperfect CSI, BER is getting worse when the number of Rx antennas is increased. In order to improve BER, a fast antenna selection scheme is proposed. The obtained numerical results prove that the proposed antenna selection scheme indeed improves the MIMO system BER performance. ©2010 IEEE

A novel blind channel estimation for a 2x2 MIMO system

A novel blind channel estimation method based on a simple coding scheme for a 2 by 2 multiple input multi-ple output (MIMO) system is described. The proposed algorithm is easy to implement in comparison with conventional blind estimation algorithms, as it is able to recover the channel matrix without performing sin-gular value decomposition (SVD) or eigenvalue decomposition (EVD). The block coding scheme accompa-nying the proposed estimation approach requires only a block encoder at the transmitter without the need of using the decoder at the receiver. The proposed block coding scheme offers the full coding rate and reduces the noise power to half of its original value. It eliminates the phase ambiguity using only one additional pilot sequence

Performance of MIMO beamforming transmission scheme in the presence of mutual coupling

This paper reports investigations into mutual coupling effects on performance of a beamforming transmission scheme of a multiple-input multipleoutput (MIMO) system operating under Rician channel conditions. It is shown that the presence of mutual coupling in a transmitting array antenna degrades the radiation pattern. However, it does not adversely affect the system capacity. If the correlated Rayleigh component (NLOS) dominates the channel, the mutual coupling leads to lower capacity. The presence of mutual coupling results in a higher capacity when the LOS component prevails. For some specific ranges of array inter-element spacing, mutual coupling can be seen as beneficial in terms of increasing the capacity when a signal beamforming strategy is applied. © 2010 IEEE

Investigation into a folded wideband monopole antenna for use in portable devices

This paper presents investigations into a compact antenna for use in portable devices to access almost all modern wireless services from about 800MHz to 6GHz. Initially, a microstrip-fed planar monopole of quarter-elliptical shape on FR-4 substrate is designed to generate a wide impedance bandwidth. This radiating element is augmented with a parasitic microstrip stub and a ground-plane cut to improve wideband performance. To reduce its projection area, the planar monopole is folded. The folded antenna occupies a volume of 13mm × 50mm × 5.6mm. It operates over two wide bands between 0.85 and 3.8GHz, and 4.9 and 6GHz, with reference to 6dB return loss (VSWR 3:1). Its radiation patterns are omnidirectional in the lower band and deteriorate at higher frequencies. The corresponding gain varies between 1.5 and 7dBi