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Title: Antenna design for 2.4 GHz ISM band
Authors: LU LU
Keywords: Antenna, 2.4GHz
Issue Date: 19-Apr-2006
Citation: LU LU (2006-04-19). Antenna design for 2.4 GHz ISM band. ScholarBank@NUS Repository.
Abstract: The utilization of 2.4 GHz ISM band has experienced enormous growth in the last 5 years. A lot of research has been conducted on the design of antennas operating inside this band. The limited space on the circuit board for the RF module imposes a limit on the physical size available for the antenna. This thesis presents two types of antennas to explore possible ways to solving this problem: reduced antenna size and multiple operating frequency band antennas.A novel reduced size antenna which can easily be implemented has been designed and shows promising results. This thesis gives the theoretical and experimental results and provides a guideline for the design of such an antenna. This antenna is fed by a pair of MCX connectors which is commercially available and small in size. (MCX connector is one type of sub-miniature connectors. It is possibly because these connectors are one of the few small connectors that can be used inside PCs.) Different feeding mechanisms are explored and the effects on antenna performance are shown. A range of planar monopole antennas are also presented in this thesis. Prototype antennas have been fabricated on the FR4 substrate with thickness of 0.8 mm. Simulated and measured results of the impedance properties are presented. Based on these designs, a new dual-band planar monopole antenna is proposed. It is designed to work in both 2.4 GHz ISM band and 5.3 GHz band. The size of the ground is purposely chosen to be same as a WLAN (Wireless Local Area Network) adapter card size. FDTD (Finite Difference Time Domain) is used in the antenna impedance prediction. Results from measurement, FDTD and FEM-based commercial results are presented. The thesis also explores a possible way to further increase the impedance bandwidth. Another prototype antenna was fabricated. The measured impedance bandwidth covers frequency band from 3.22 GHz to 11.62 GHz. It produces a radiation pattern which remains relatively stable at different frequencies. This work does not only consider the antenna design parameters from a microwave perspective, but also focuses on the communication point of view. A CASIRA Bluetooth development module was used to measure the BER (Bit Error Rate) using the different antenna designs mentioned above together with the RF module of the development kit. The measurement results presented are used to determine whether the proposed antennas are suitable for the Bluetooth applications. Furthermore, a way of mitigating the coexistence interference in the 2.4 GHz ISM is proposed in this thesis. A circularly polarized antenna was designed and BER measurements were performed. These results are compared to those obtained with a linearly polarized antenna. It is found that Bluetooth communication using a circularly polarized antenna has better BER results when no counter-interference methods have been employed. The circularly polarized antenna also shows better performance when there is no line of sight transmission path in the Bluetooth channel.
Appears in Collections:Master's Theses (Open)

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