Wireless multi-standard terminals: system analysis and design of a reconfigurable RF front-end

Abstract

38The availability of multi-standard terminals will be key to provide location independent connections able to take advantage of any possible infrastructure. This paper addresses both the architecture and the circuits for the RF front-end of a terminal with cellular (GSM, EDGE and UMTS), LAN (IEEE802.11a/b/g) and Bluetooth radio interfaces. A multi-standard simulator has been developed to validate the architectural and design choices in terms of error rates at bit or packet level. The simulator takes into account implementation non-idealities and performs all tests to be passed to comply with the given standards. It also hints at the need for implementation margins as well as at possible optimization between different RF-blocks. The final solution, still under design, will consists of two chips, one including the TX and the other the RX for all the above standards. The cellular (plus Blue-tooth) transmitter relies on a Linear amplification with Non-linear Component (LINC) architecture that uses direct modulation of the carrier. This allows power saving because DAC and up-conversion mixers are not required. The WLAN (plus BlueTooth) transmitter adopts a direct-conversion architecture that implements an internal output matching over all the frequency bands while maintaining good system efficiency. The same building blocks are used for all standards, saving power and chip area. The cellular receiver architecture is able to reconfigure between Low-IF for GSM and direct conversion for UMTS and Blue-tooth. The key aspects in achieving the specs in a fully integrated fashion are a mixer with a very high dynamic range, a careful control of DC offsets and a highly tunable VCO. The WLAN receiver also uses direct-conversion with a Low Noise Amplifier based on a common gate topology that uses positive feedback through integrated transformers to improve input matching and noise. The frequency down-converter uses current driven passive mixers to achieve low 1/f noise corner, and high linearity with low power consumption. Finally, the base-band blocks can be shared among all the standard, thanks to their high reconfigurability. The paper describes the ideas behind the key RF blocks and some details of circuit implementation. Experimental measurements from sub-blocks in a 0.13 µm CMOS technology are presented and discussed. Abstract Feature IEEE CIRCUITS AND SYSTEMS MAGAZINE

Subsampling Receivers with Applications to Software Defined Radio Systems

“…Using a narrowband strategy, an alternative multi-standard receiver solution is proposed by [2], separating into two different RF channels, one for 2.4 and 5 GHz wireless local area networks (WLANs) and the other for Global System for Mobile Communications (GSMs).…”

“…Table 3 [8] shows the specifications for most of common wireless communication standards [2] and the results obtained in some of these previously published works on noise performance. These results are compared with those obtained in [8], in order to observe the benefits of implementation of a multiple clock technique for multi-standard receivers based on subsampling.…”

“…As a consequence, there is a tendency to design transceivers for multiple standards [1][2][3][4][5][6][7][8]. A similar problem arises in the test industry, where providers of testing and certification services to the wireless communication industry need multi-standard receivers, in order to reduce the cost in testing equipment.…”

A 1.2V inductorless receiver front-end for multi-standard wireless applications

“…The OTA ensures a self-biasing mechanism of the SDC and an offset correction at the two differential outputs of the circuit. The resistors 1 R improve matching between the transistors 1 M and 2 M . The drain currents of these two transistors have the same amplitude and opposite phases.…”

“…It is a challenge to stretch the design space of an RF front-end in such a way that it satisfies simultaneously the requirements of as many standards as possible. One possibility is the use of tuned RF front-ends based on narrow band, tunable LNAs [1]. The complexity and the occupied chip area of this multi-standard RF front-end grow rapidly as the number of covered standards increases.…”