Mark B. Child

Compact microstrip antenna design for microwave imaging

An ultra-wideband microstrip antenna design is considered with respect to applications in breast cancer detection. The underlying design concept is based on ground penetrating radar (GPR). Simulated and measured prototype performance show excellent performance in the input impedance and radiation pattern over the target range from 4 GHz to 8 GHz. The 4 GHz to 8GHz frequency band for microwave imaging perform better in comparison with other microwave frequencies. The antenna also shows a reasonable uniform radiation performance in the broadside direction which contributes to the reduction of clutter levels, thus aiding the reconstruction quality of the final image

A Frequency Tunable PIFA Design for Handset Applications.

A frequency tunable planar inverted F antenna (PIFA) is presented for use in the following bands: DCS, PCS, and UMTS. Initially, the tuning was achieved by placing a lumped capacitor, with values in the range of 1.5 to 4 pF, along the slot of the radiator. The final tuning circuit uses a varactor diode, and discrete lumped elements are fully integrated with the antenna. The antenna prototype is tunable over from 1850 MHz to 2200 MHz, with an associated volume of 21×13.5×5 mm3, making it suitable for potential integration in a commercial handset or mobile user terminal.

Analysis of the effect of EBG on the mutual coupling for a two-PIFA assembly

Size constraints and mutual coupling on the performance of a two-element PIFA assembly are investigated for a design frequency of 2.4 GHz. A benchmark antenna assembly, employing a normal metallic ground plane is compared with an EBG modified ground plane. The height of the antenna elements over the EBG is optimised, and an isolation factor of 9.12 dB is achieved for a gap of 2.5 mm. Prototype structures have been constructed and measured for both cases.

Design of a planar inverted F-L antenna (PIFLA) for lower-band UWB applications

This paper examines the case for an ultrawideband planar inverted-F-L-antenna design intended for use in the lower sub-band. The antenna construction is based on the conventional inverted F, and inverted L as its feed element, and parasitic element, respectively. The optimized antenna size is 30×15×4mm3. The prototype antenna has a good return loss of −10 dB, and a 66.6% impedance bandwidth (2.8 GHz–5.6 GHz), the gain varies between 3.1 dBi and 4.5 dBi.

Optimum Design of Doherty RFPA for Mobile WiMAX Base Stations

RF power amplifiers in mobile WiMAX transceivers operate in an inherently nonlinear manner. It is possible to amplify the signal in the linear region, and avoid distortion, using output power back-off; however, this approach may suffer significant reduction in efficiency and power output. This paper investigates the use of Doherty techniques instead of back-off, to simultaneously achieve good efficiency and acceptable linearity. A 3.5 GHz Doherty RFPA has been designed and optimized using a large signal model simulation of the active device, and performance analysis under different drive levels. However, the Doherty EVM is generally poor for mobile WiMAX. Linearity may be improved by further digital pre-distortion, and a simple pre-distortion method using forward and reverse AM-AM and AM-PM modeling. Measurements on the realized amplifier show that this approach satisfies the EVM requirements for WiMAX base stations. It exhibits a PAE over 60%, and increases the maximum linear output power to 43 dBm, whilst improving the EVM.

Automatic liquid level indication and control using passive UHF RFID tags

This paper proposes a new perspective to the liquid level monitoring and control technique by deploying energy efficient passive UHF RFID tags as liquid level sensors. The system consists of the pump, storage tank, level sensors (passive tags), RFID tag reader, pump control circuit, alarm circuit, and an indicator circuit. The tags are sealed (air and water tight), programmed with unique level labels using the Alien Reader software(860-868MHZ) and deployed to various levels of a storage tank for level monitoring and control. The mirrored P-shaped tag is designed modelled and deployed for use as the liquid level sensors. The RFID reader is disguised to form a part of the tank cover literarily few inches away from the tags. A variation of the tag readings received is used to infer level information which is communicated via the reader middleware to a computer database for monitoring.

A capacitively loaded antenna for use in mobile handsets

A tuneable slotted patch antenna design is presented and verified for use in the DCS, PCS and UMTS bands. The tuning circuit consists of two varactor diodes, with some passive components, and is integrated fully with the radiator patch, with the varactors occupying different locations over the slot. The tuning does not require any further modification to the patch or feed geometry. Good agreement is observed between the predicted and observed impedance bandwidth, return loss, gain and radiation pattern, throughout the range 1.70 GHz–2.05 GHz.

An ultra wide band power divider for antenna array feeding network

This paper presents a design procedure for a physically small, equal phase and equal power, 1-to-4 ultra-wideband Wilkinson power divider is presented. Initially, a 1-to-2 divider was designed and optimized for the full 3.1 GHz to 10.6 GHz range. The 1-to-4 divider was realized using three 1 to 2 dividers, and further optimized for full band insertion loss, return loss, and isolation. The circuits were constructed using a 0.75mm thick Rogers RO3035 substrate, and experimentally validated.

A Staircase-Shaped DGS Structure Monopole Antenna for UWB Operations

This paper presents a novel, physically compact, miniaturized, ultra-wideband (UWB) monopole antenna design, which utilizes a defected ground structure (DGS). The defected ground design is realized as a spiral staircase-shaped pattern, and the optimized antenna volume is 26 × 25 × 1.6 mm3. The resultant antenna operates over the full UWB frequency range from 3.1 GHz to 10.6 GHz, with predicted gains in the range 0.1 dBi to 3.36 dBi across the band.

Design of a compact tuned antenna system for mobile MIMO applications

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 mm3, 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.