An Analog Correlator for Ultra-Wideband Receivers
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An Analog Correlator for Ultra-Wideband Receivers Chunjiang Tu Institute of Microelectronics of Tsinghua University, District 9, East Main Building, Beijing 100084, China Email: [email protected]
Boan Liu Institute of Microelectronics of Tsinghua University, District 9, East Main Building, Beijing 100084, China Email: [email protected]
Hongyi Chen Institute of Microelectronics of Tsinghua University, District 9, East Main Building, Beijing 100084, China Email: [email protected] Received 29 September 2003; Revised 5 March 2004 We present a new analog circuit exhibiting high bandwidth and low distortion, specially designed for signal correlation in an ultrawideband receiver front end. The ultra-wideband short impulse signals are correlated with a local pulse template by the correlator. A comparator then samples the output for signal detection. A typical Gilbert mixer core is adopted for multiplication of broadband signals up to 10 GHz. As a result of synchronization of the received signal and the local template, the output voltage level after integration and sampling can reach up to 100 mV, which is sufficient for detection by the comparator. The circuit dissipates about 30 mW from double voltage supplies of 4 V and 4.4 V using 0.24 µm SiGe BiCMOS technology. Simulation results are presented to show the feasibility of this circuit design for use in ultra-wideband receivers. Keywords and phrases: analog correlator, Gilbert cell, ultra-wideband receiver.
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INTRODUCTION
Ultra-wideband (UWB) communication systems have been drawing increasing attention in recent years due to their attractive features of high transmission rates and low cost. UWB systems transmit information through short impulses, in contrast to traditional wireless communication systems, which use sinusoidal carriers. In impulse radio systems, several modulation techniques may be deployed including pulse position modulation (PPM) and pulse amplitude modulation (PAM) [1], for all of which a correlator is an indispensable component for detection by the receiver [2]. In order to lower the cost and power of wireless mobile devices, it is necessary to integrate UWB systems on a single chip, thereby enabling a wide range of applications in the wireless data communication field. This process represents a big challenge for current VLSI technology, because of the UWB range involved from 3.1 GHz to 10.3 GHz. At present, only a few publications dealing with this topic have therefore been published. An integrated UWB transceiver architecture for low data rates (100 Kbps) at low bandwidth (below 960 MHz) using a digital implementation of the correlator has been described in [3]. Although a correlator can also be implemented in digital format for high
data rates of up to 100 Mbps at high bandwidth, direct sampling of 3.1 GHz to 10.3 GHz frequency signals is ultimately required, which is almost impossible for current ADC techniques. The advantage of an analog correlator is that it can process signals in real time and provide a continuous output at
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