Recent research on the performance of multicarrier systems suggest that the us e of wavelet transforms (WT) outperforms the conventional fast Fourier transform (FFT) orthogonal frequency division multiplexing (OFDM) systems. Wavelets based systems provide better spectral efficiency because of no cyclic prefix requirement, have very narrow side lobes and also exhibit improved BER performance. Meanwhile, channel estimation in wavelet based multicarrier systems still remains a big challenge. In this work an investigation into the performance of discrete wavelet transform based multicarrier system using zero forcing equalization in time domain is presented. The results produced were then compared to that of conventional FFT-based OFDM system. The proposed system shows superior BER performance.

The road towards the reduction in the carbon footprint associated with power-hungry wireless communication devices will require a holistic design approach to ensure that energy saving can be achieved throughout the entire system. The information and communication technology today accounted for 3 and 2% global power consumption and global CO₂ emissions, respectively, where a significant portion is a result of the power consumption in the radio frequency (RF) power amplifier device. Moreover, tomorrow amplifiers will need to be reconfigurable and host a plethora of modulated signals to support effective signal processing. Therefore performance metrics such as linearity, power efficiency and their trade-off should be at the forefront of the RF power amplifier design. This study proposes an energy-efficient power amplifier design based on the Doherty configuration as part of a green RF front end for mobile WiMAX. The authors extend the classical Doherty to incorporate a three-stage load modulation design with a proposed new output power combiner. The performance of the three-stage load modulation RF power amplifier is compared with the legacy two-stage load modulation technique. The experimental results show that 30 dBm output power can be achieved with 67% power-added efficiency, which represents a 14% improvement over the current state-of-the-art system while meeting the power output requirements for mobile WiMAX.

The design of a reconfigurable antenna with good load matching and covering a wide frequency range presents a practical challenge when the antenna size is tightly constrained. A procedure is presented for the design of a reconfigurable mobile antenna, which overcomes the antenna size limitations. Tuning is achieved by placing a varactor diode at a specific position across a slot in the radiator conducting surface. The fabricated antenna is designed to cover a wide band, between 1700 and 2040 MHz, at a return loss better than 10 dB. The radiation of harmonics generated because of the varactor non-linearities are simulated and measured. The experimental set-up ensures that the low levels of radiated harmonics are reliably validated. The experimental results show good agreement with that computed using the Friis equation.

Without a holistic design and fabrication approach, future wireless communication devices would be extremely large in size to accommodate multiple radio access technologies (RATs) compared to today's more conventional mono-mode devices. Typically multiple RAT devices will be comprised of multiple RF power amplifiers, low noise amplifiers (LNA), RF band pass filters, modulators and demodulators; one for each wireless technology. Obviously, this will increase the complexity of the circuit design and will cover a large part of the circuit space leading to power hungry devices. Radio frequency microelectromechanical systems (RF-MEMS) can be good candidate for innovative RF front end devices since it is reconfigurable features in nature therefore allowing a reduction in the number of external components in a single device for the use of multiple RATs. This paper discusses the history, state of the art of tunable RF filter and beyond.

A small tuneable MIMO antenna module is investigated for possible UMTS mobile applications. The radiators are realized as slotted planar monopoles. The two-element MIMO antenna module occupies a volume of 50.0 × 37. 5 × 1.6 mm ³ , and is printed onto a FR4 substrate. Low mutual coupling between the radiators is achieved by means of the addition of a coupling strip to a defected ground plane structure. The effect of tuning the resonant frequency, as well as the operational bandwidth is investigated in simulation which indicates that this antenna system should provide a mutual coupling across the full bandwidth better than -13dB.

The small size of the mobile terminal poses serious integration and antenna miniaturization challenges. In this work, we propose a compact dual-band dipole balanced antenna that is based on printed folded arms radiating elements. The performance of the proposed antenna has been analysed and optimised for the two targeted frequency bands in which indicates that a good impedance matching characteristic at 700 and 2600MHz (return loss less than 8 dB) was accomplished. In addition, the effect of some parameters on the performance of the proposed antenna is also discussed in this article. Owing to the compact size and simple structure, this printed folded arms dipole antenna can be applicable for mobile handset and wireless communication applications.