Hossein Alavi

Array analysis using high efficiency mm-wave antenna for gigabit plus throughput wireless communication

In the past few decades, advances in wireless technologies have increased the requirement for high data throughput. Newer demand for high quality visual graphic and multimedia contents such as high definition video and high throughput wireless data transfer requires wireless communication to support Gigabit plus data rates. The world wide license-free 5–7GHz spectral band in 60GHz provides great potentials to enable multi-Gigabit data transfer and has been drawing strong commercial interests [1–3]. High gain adaptive beam steering phased array antenna is a key component of a low cost mm-wave CMOS RFIC solution for commercial adaptation. In this paper, a high efficient mm-wave microstrip antenna design with various antenna array architectures is presented. Simulations indicated that a peak gain of 9.1dBi and 12% bandwidth can be achieved with a single mm-wave microstrip patch antenna. Various antenna array architectures are designed and studied to quantify the impact of the antenna array architecture and performance on the mm-wave network performance.

Figures of merit for self-beating filtered microwave photonic systems.

We present a model to compute the figures of merit of self-beating Microwave Photonic systems, a novel class of systems that work on a self-homodyne fashion by sharing the same laser source for information bearing and local oscillator tasks. General and simplified expressions are given and, as an example, we have considered their application to the design of a tunable RF MWP BS/UE front end for band selection, based on a Chebyshev Type-II optical filter. The applicability and usefulness of the model are also discussed.

Lens-enhanced phased array antenna system for high directivity beam-steering

This paper investigates a hybrid steerable antenna topology composed of a small phased array and a significantly larger planar lens-array. The phased array antenna creates an electronically steerable beam, and the lens-array further confines the beam to enhance its directivity. The feasibility of this approach is examined via a 60 GHz design example based on a 4 × 4 phased array and a 24 × 24 lens-array. It is observed that adding the lens-array improves the directivity by 2.5–6 dB for beams within 45° of the boresight direction. Since the lens consumes no power and it may be manufactured inexpensively, this improvement comes at very little cost. The overall depth of the system in this example is 1 cm, which is quite small compared to typical lens-based systems. These characteristics make the proposed topology suitable for applications in laptop computers, tablets PCs, PDAs, flat screen TVs and similar products.

Channel-adaptive complex K-best MIMO detection using lattice reduction

Lattice reduction (LR) aided detectors mitigate the exponentially increasing complexity of large multiple-input, multiple-output (MIMO) systems while achieving near-optimal performance with low computational complexity. In this paper, a channel-adaptive complex-domain LR-aided K-best MIMO detector is presented that reduces the gap between the K-best sphere decoding (SD) detector and the maximum likelihood (ML) optimal MIMO detector. While maintaining BER performance, computational complexity is reduced by 50% over a conventional complex domain K-best SD detector by implementing a new on-demand complex-domain candidate symbol selection algorithm. Two tunable variables in the candidate selection process are introduced to enable both coarse-grained and fine-grained adaptation of computational complexity to channel conditions.

Flicker noise mitigation in direct-conversion receivers for OFDM systems

Direct-conversion receiver (DCR) architecture has received considerable attention recently owing to its portable architecture and superior performance in terms of power and cost over its super-heterodyne counterpart. Flicker noise is one of the major impairments which severely affects the performance of the system. In this work, we investigate the use of signal processing techniques in the mitigation of flicker noise in OFDM-based systems which employ DCR architecture. The statistical properties of flicker noise are exploited to develop adaptive signal processing algorithms that reduce the effect of flicker noise in DCRs. Results indicate that signal processing algorithms can provide significant performance gain under low SNR conditions.

Third-order linearization for self-beating filtered microwave photonic systems using a dual parallel Mach-Zehnder modulator

We develop, analyze and apply a linearization technique based on dual parallel Mach-Zehnder modulator to self-beating microwave photonics systems. The approach enables broadband low-distortion transmission and reception at expense of a moderate electrical power penalty yielding a small optical power penalty (<1 dB).

Analytical method to calculate the unloaded Q of a T-type stepped-impedance resonator

Conventional filter synthesis procedures assumes ideal building blocks (losses with infinite unloaded quality factor Q). In practice, the insertion loss (IL) of microwave filters depends primarily on the unloaded Q of their constituent resonators. A reliable mechanism for a priori estimation of achievable filter IL using practical resonators with limited Q is highly desirable. This paper presents an analytical derivation of the unloaded Q of a microstrip T-type stepped-impedance resonator. An efficient filter design procedure is deduced from the derived formulas. Finally, the comparison between simulated resonators and the proposed formulation are presented, as well as, a simulation of a filter designed with one of the resonators.

Design of nine pole microstrip low pass filter with metal loaded defected ground structure

A novel design methodology for sharpening the response of a low pass filter (LPF) using metal loaded DGS and broadened transmission line elements is being proposed in this paper. The technique presented by Lim et al.[7] is used to design a nine pole low pass filter using square dumbbell DGS to replace the high impedance inductive sections. Further, metal strips are inserted in the etched gap connecting the dumbbells to increase the sharpness of response. Simulation results are used to analyze the dependence of the filter response on the defect type. The metal loaded DGS is tuned to get the optimal design parameters. The designed filter is fabricated and a sharp cut off is received at the cutoff frequency of 2.4 GHz while reducing the size by ≈40% when compare with an stepped impedance filter. All the measurements have been done on Rohde and Schwarz Vector Network Analyzer 1127.8500

Embedded DTV diversity antenna for notebook application with high SNR

A fully functional internal DTV diversity antenna has been designed and tested. The proposed internal balanced dipole antenna was integrated with a DTV module in a notebook computer. The results demonstrate that a balanced dipole antenna for noise suppression and diversity reception enable high quality reception of a DTV signal even though we trade-off some antenna performance after packaging in notebook computer.