2010 IEEE International Ultrasonics Symposium
DOI: 10.1109/ultsym.2010.5935487
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The present work discusses the implications to the RF front-end for multi-standard multi-band cellular radios by analyz- ing noise and linearity specifications of the active circuits as well as isolation and insertion loss limits of the involved passive elements. Optimal adjustments of pertinent trade-offs and an outlook into future requirements and trends are presented. . Index Terms — Reconfigurable architectures, digital front-end, RF-Transceiver. I. INTRODUCTION Today's modern mobile smartphones are characterized by an enormous amount of functionality and applications. The huge number of these new features and applications are moti- vating the user to utilize the smartphone almost permanently. The limited capacity of the battery of the smartphone, together with the increased use-time, drives the semiconductor industry to reduce the power consumption of the whole mobile phone platform. In the near future a modern cellular radio has to support various cellular standards like GSM, UMTS and LTE. Moreo- ver, a modern multi-standard smartphone has to be capable to operate at several different frequency bands in a TDD- or FDD mode. All those requirements result in a dramatically increased complexity of the RF front-end as is shown in Fig. 1. To reduce the complexity and to minimize costs and PCB area, the removal of the external interstage SAW and/or BAW filters in the receiver (RX) and transmitter (TX) front-end (FE) has become a mandatory feature of state-of-the-art full-duplex capable cellular radios in recent years. Inevitably, this removal increased the requirements for the linearity and noise behavior of the active circuits in the wireless transceivers resulting in an increased current consumption and circuit complexity. The design for such tough requirements results in an increased current consumption of the entire wireless transceiver. In this paper, we analyze the linearity and noise require- ments of modern cellular RF transceivers with respect to the RF front-end performance. Furthermore, we present and dis- cuss the trends in modern power optimized RF transceiver design.