Nurul H. Noordin

A smart antenna array for brain cancer detection

A smart antenna array is designed and fabricated for brain cancer detection. The smart antenna array is composed of three ultra-wideband vivaldi antennas. A brain model with 4 layers is created and simulated with the CST Microwave Studio. A radius of 5mm tumour model is placed into the white matter close to the skull. A short pulse is transmitted into the brain and the reflected signals are detected by one or more receiver antennas placed in different positions. Analysis of the reflected signals shows that using a smart antenna array based imaging system can be used for brain cancer detection.

Uniform circular arrays for phased array antenna

This paper compares the performances of a number of uniform circular array (UCA) configurations for phased array antennas. A UCA geometry is targeted due to its symmetrical configuration which enables the phased array antenna to scan azimuthally with minimal changes in its beam width and sidelobe levels. Each UCA configuration consists of 19 isotropic elements. Particle Swarm Optimization (PSO) is used to calculate the complex weights of the antenna array elements in order to adapt the antenna to the changing environments. Comparisons are made in the context of adaptive beamforming properties and Signal to Interference Ratio (SIR). The results obtained suggest that a planar uniform hexagonal array PUHA (1:6:12) is suitable for high resolution applications as its sidelobe levels are the lowest compared to the other geometries.

Single-feed polarization reconfigurable patch antenna

A novel single-feed design of a patch antenna with polarization reconfigurability is proposed in this paper. Four identical notches with parasitic elements are embedded into the design. The antenna can switch between linear polarization (LP), left hand circular polarization (LHCP) and right hand circular polarization (RHCP). The results show that the proposed antenna demonstrates an impedance bandwidth of 50 MHz (S11 <;-10 dB), and a polarization bandwidth of 44.3 MHz (axial ratio <; 3 dB). Also, the axial ratio is obtained in a broad angular range when the antenna is in LHCP and RHCP mode. The structure of the proposed antenna is simple and suitable for antenna array applications that require circular polarization and polarization diversity properties.

An evaluation of 2-phase charge pump topologies with charge transfer switches for green mobile technology

The development of charge pumps has been motivated by the power supply requirements of portable electronic devices. Charge pumps are inductorless DC-DC converters that are small size and high integration. The quality of the charge pump greatly depends on the effectiveness of switches to turn on and off at the designated clock phases. However, to date, no analysis has been carried out on the overall performance of charge pumps based on switch components in practice. This work demonstrates the characteristics of transistors as charge transfer switches and their effects on the performance of a charge pump. Three most common charge pump topologies are evaluated in terms of voltage drop due to on-resistance and charge loss per switch. Simulations are performed in 0.35µm Austriamicrosystems (AMS) technology for Dickson, Voltage Doubler and Makowski charge pump topologies in steady and dynamic states. In addition, the effect of switch parameters for different charge pump topologies are compared and analysed. We demonstrate that the Makowski charge pump is the topology for future green mobile technology.

Analysis of DOA estimation for directional and isotropic antenna arrays

A comparison analysis between two different types of antenna arrays in direction-of-arrival (DOA) estimation is presented. This study was undertaken to point out any difference in the process of DOA estimation between isotropic and directional antenna array. To the best of our knowledge, there is no previous work that analysed the DOA estimation between these two antenna arrays. The approach taken was to estimate all predetermined angle-of-arrival (AOA) correctly by using MUSIC, a spectral-based DOA algorithm. Results obtained show that, to perform the DOA estimation, isotropic antenna array depends entirely on DOA algorithm, whereas directional antenna array required both the DOA algorithm and the position of the main beam at any instant. This work concludes that, in practical application, it is essential to consider both the performance of DOA algorithm and the beam pattern to ensure the DOA estimation is carried out correctly.

Capon-like DOA estimation algorithm for directional antenna arrays

This work proposes a new direction-of-arrival (DOA) estimation algorithm for directional antenna arrays. Most of the existing DOA algorithms are difficult to work with directional antenna arrays due to the characters of directional elements and thus proper modification is required. The proposed algorithm is based on Capon algorithm through the introduction of a new optimisation problem, which aims to maintain the array gain in the ‘look direction’, so that the DOA can be estimated correctly using a directional antenna array. To verify the performance of the proposed algorithm, computer simulations are performed and then the results obtained are compared with the Capon algorithm. The results show that the proposed algorithm outperforms the Capon algorithm.

Single-Port Beamforming Algorithm for 3-Faceted Phased Array Antenna

The implementation cost of a phased array antenna is high due to the large number of RF components required in the system. Migrating from the multiport beamforming system to a single-port beamforming system is a promising alternative. In this letter, a novel single-port beamforming algorithm using the pseudo-inverse function is proposed. The signal received at each element is estimated from the combined signal that is generated by the single-port output system. With the estimated values, the array weight is then calculated for the desired radiation pattern. The single-port concept is implemented on a 3-faceted antenna array and simulated in MATLAB. The results show that adaptive beamforming can be achieved with the estimated signals, and this technique has a faster execution time compared to a multiport beamformer. With reduced component count and implementation cost, the proposed technique demonstrates potential for commercial deployment in the mobile communication industry.

A WiFi/4G compact feeding network for an 8-element circular antenna array

This paper presents a novel one-to-eight compact feeding network based on the Wilkinson power divider for a circular antenna array. The network consists of four 1:2 conventional Wilkinson power dividers. The outputs revolve at 45° in order to satisfy the circular geometry on an FR-4 substrate. Moreover, the network size has been optimized and miniaturized targeting compact portable devices. The feeding network design targets WiFi and LTE/4G frequency bands. Designed and examined with the CST Microwave Studio, this feeding network provides suitable return loss, insertion loss and isolation parameters for the designated frequency ranges. Fabrication and measurement results closely correlate with simulation results. The design can be applied to SIMO and MIMO microwave systems.

Meandered inverted-F antenna for MIMO mobile devices

This paper presents an improved efficiency, miniaturized, meandered, inverted F antenna for MIMO systems. A 7.5 mm by 15.5 mm miniature antenna has been developed which gives 25% of improvement for the voltage standing wave ratio compared to the basic IFA structure. The antenna achieves a 10dB return loss over nearly 7% bandwidth at 2.45 GHz. Three antennas were placed on a 110mm × 50 mm ground-plane at a height of 7 mm from ground. The geometry and position of the antennas are optimized in order to achieve the low mutual coupling and small envelope correlation that complies with MIMO requirements. Simulations show that the antenna has high radiation efficiency. A prototype of the system has been fabricated and tested.

Low side lobe level synthesis for linear faceted adaptive antenna arrays

In this paper, a 3-faceted array which consists of eight left-hand circularly polarized (LHCP) elements operating at 2.4 GHz, having low side-lobe level (SLL) radiation pattern for adaptive antenna implementation for mobile communication is synthesized. A set of correction phase on top of the classical amplitude tapering method, such as Binomial, Dolph-Chebychev and Taylor, is proposed to enable the 3-faceted array to generate a radiation pattern with the desired SLL. Simulation results show that a radiation pattern with an acceptable main beam width and side-lobe level is obtained using the Taylor weighting. With this technique, not only has the 3-faceted array a wider scanning range, but also lower side lobe levels.