Reducing Spurious Output of Balanced Modulators by Dynamic Matching of I, Q Quadrature Paths

Jun OTSUKI  Hao SAN  Haruo KOBAYASHI  Takanori KOMURO  Yoshihisa YAMADA  Aiyan LIU  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E88-C   No.6   pp.1290-1294
Publication Date: 2005/06/01
Online ISSN: 
DOI: 10.1093/ietele/e88-c.6.1290
Print ISSN: 0916-8516
Type of Manuscript: Special Section LETTER (Special Section on Analog Circuit and Device Technologies)
Category: AD/DA
Keyword: 
Cartesian transmitter,  arbitrary waveform generator,  IQ mismatch,  SFDR,  spread spectrum,  

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Summary: 
This paper presents a technique for reducing spurious output of balanced modulators used in transmitters and arbitrary waveform generators. Two-step upconversion is a convenient way to produce a desired single-sideband (SSB) radio-frequency (RF) signal--baseband quadrature I and Q signals (which are analog outputs of direct digital frequency synthesizers) are upconverted by mixers and local oscillators (LOs)--but mismatches between the DACs in I and Q paths cause spurious output. We propose a method of dynamically matching the I and Q paths by multiplexing two DACs between I and Q paths in a pseudo-random manner. MATLAB simulation shows that multiplexing the two DACs spreads the spurious output, caused by mismatches between the two DACs, in the frequency domain, and reduces the peak level of spurious signals.