Applied To Uwb System Of Four-channel Digital To Analog Converter Design

Orthogonal frequency division multiplexing(OFDM) is a promising technique for achieving high bit rates and high reliabilities required for wireless communication. This new technique has gained increased interest for its high bandwidth efficiency and robust performance in multipath dispersive environment. DC-OFDM based UWB technique has been selected as the standard of Information technology Telecommunications and information exchange between systems of China. For achieving this high-performance base station, it is required that the Digital-Analog-Converter(DAC) has the higher performance, such as having sufficient signal bandwidth to cover all of its operating frequency, having enough dynamic range in order to prevent adjacent channel signal obstruction. All these requirements are for the purpose of simplifying the increasingly complex structure of the base station.To be applied in the MB-OFDM UWB System, an4channel8-bit650MHz Current-Steering DAC is designed in this paper. Firstly the application environment and the development of DAC are briefly introduced. And then, the basic structure of the high-speed high-resolution DAC is discussed from the system point of view. After that various non-ideal factors of the critical circuits are analyzed and the specifications and system architecture is proposed. Then the key module circuit analysis and design, including the cascade current source, the switch circuit and the swing reduction driver is elaborated in detail from the circuit point of view. In the last, the layout design and testing result is introduced.The proposed DAC is fabricated in SMIC0.13μm one-poly eight-metal CMOS Mixed-Signal process. The measured integral nonlinearity (INL) and differential nonlinearity (DNL) are0.32LSB and0.41LSB, respectively, and the measured Nyquit spurious free dynamic range (SFDR) is42dB for signals in band width at650MS/s clock.