A 0.9-2.6 GHz Broadband RF Front-End Chip-Set with a Direct Conversion Architecture

Munenari KAWASHIMA  Tadao NAKAGAWA  Hitoshi HAYASHI  Kenjiro NISHIKAWA  Katsuhiko ARAKI  

IEICE TRANSACTIONS on Communications   Vol.E85-B    No.12    pp.2732-2740
Publication Date: 2002/12/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Software Defined Radio Technology and Its Applications)
RF front-end,  direct conversion architecture,  quadrature mixer,  local oscillator,  low-noise variable gain amplifier,  

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A broadband RF front-end having a direct conversion architecture has been developed. The RF front-end consists of two broadband quadrature mixers, a multi-band local oscillator, and a broadband low-noise variable gain amplifier (LNVGA). The mixer achieves broadband characteristics through the incorporation of an in-phase power divider and a 45-degree power divider. The in-phase power divider achieves broadband characteristics through the addition of a compensation capacitor. The 45-degree power divider achieves broadband phase characteristics through the addition of a compensation capacitor and a compensation resistor. The local oscillator, which is composed of two VCOs, two frequency dividers, and four switches, can cover three systems including one FDD system. The LNVGA achieves its broadband characteristics without the use of reactance elements, such as inductors or capacitors. In a trial demonstration, when the RF frequency was between 900 MHz and 2.5 GHz, the mixer for a demodulator experimentally demonstrated an amplitude balance of less than 1.6 dB and a quadrature phase error of less than 3 degrees. When the RF frequency was between 900 MHz and 2.5 GHz, the mixer for a modulator demonstrated an image ratio of less than -30 dBc. The local oscillator demonstrated multi-band characteristics, which are able to cover the target frequencies for three systems (PDC, PHS, 2.4 GHz WLAN). From 900 MHz to 2.5 GHz, the amplifier shows a noise figure of less than 2.1 dB and a gain of 28 1.6 dB.