Two Tunable Frequency Duplexer Architectures for Cellular Transceivers

• In this paper two architectures for tunable duplexersare presented. The tuning is accomplished through variablecapacitance and resistance. The architectures are based on athree element series-parallel resonator, with one pass and onestop frequency. Both architectures rely on filtering as well ascancellation for good Tx to Rx isolation while maintaining lowinsertion loss. The first architecture, the Filtered TransformerBalanced (FTB) isolator, has single ended transmit and antennaports and a differential receive port. The second architecture,the Cross Coupled Filtering (CCF) isolator, is fully differential.For a resonator Q of 50, the impedance ratio of the resonator atpass and stop frequencies is 18.5dB for 3GPP band-I. In the FTBisolator this results in 1.65dB Tx and 2.14dB Rx insertion loss,and 53 dB isolation for a 20 MHz channel bandwidth. In the CCFisolator this results in 1.9dB Tx and 1.9dB Rx insertion loss, and59dB isolation for a 20 MHz channel bandwidth. These figuresare obtained with a 20% resistive mismatch, showing feasibility ofgood performance in an environment with changing impedance.As the operating frequencies of cellular systems increase, thesestructures will become fully integratable due to the reduced sizesof inductors and transformers.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Publication and Content Type

art (subject category)

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