Design of an Efficient Frequency Synthesizer used For Multi-Band OFDM

Abstract— This journal describes the design of a 3GHz -10 GHz [1] frequency synthesizers for Multi-band OFDM in an Ultrawide band (UWB) transceiver at 180nm CMOS technology. As there is a requirement of high speed data rate, reduction in chip size and low power consumption for wireless devices there is demand for high speed complex signal processing architecture which meet the requirements. Bandwidth is another precious commodity, according to FCC regulations available unlicensed bandwidth is 3.1GHz – 10.6GHz [1] (UHB). In this journal the system requirements for the Frequency synthesizer in an Ultrawide band (UWB) is discussed. OFDM is combination of modulation and multiplexing, the signal which is to be sent through channel is first split into independent sub channels, modulated by data at transmitter and then de-multiplexed at the receiver. In this process the frequency synthesizer generates carrier tone for each sub channel. Data which is to be transferred is split using multiplexer and can be transferred in each band separately and combined at the receiver. The number of RF blocks are implemented for generating carrier tones, 14 carrier tones are generated to reduce power consumption, to increase the data rate. An efficient frequency synthesizer is proposed to reduce number of RF blocks. The efficient system could be used for high data rate communication system like 3G, 4G and other applications which require high data rate.

Keywords— Frequency Synthesizer, Ultra-Wide Band, OFDM, Radio Frequency, TSPC.

INTRODUCTION

As the technology goes on improving there is demand for high speed data rate signal processing applications. FCC (Federal Communications Commission) in the year 2002 released unlicensed UHB band in the range 3.1 GHz to 10.6 GHz [1], bandwidth is the precious commodity so we need to utilize available bandwidth to achieve high data rate. Multiband OFDM is one of the most efficient systems to effectively utilize available bandwidth, increase high data rate. Frequency synthesizer generates different carrier tones in the range 3-10 Hz range. This technique divides the available bandwidth into 14 different channels with each of 528MHz.
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