DocumentCode :
396562
Title :
A novel frequency synthesizer concept for wireless communications
Author :
Gaudes, Cesar Caballero ; Valkama, Mikko ; Renfors, Markku
Author_Institution :
Grupo de Tecnologias de las Comunicaciones, Zaragoza Univ., Spain
Volume :
2
fYear :
2003
fDate :
25-28 May 2003
Abstract :
Strict requirements for high spectral purity, high operating frequencies and fast switching speed together with the power consumption limitations make the frequency synthesizer design an extremely challenging task for wireless applications. In this paper, a combination of analog and digital synthesis techniques is discussed and analyzed. A low frequency tone generated digitally is upconverted to the final frequency range by means of I/Q mixing. Ideally, the use of I/Q processing eliminates the need for any sideband suppression filtering. In practical implementations, however, the amplitudes and phases of the I and Q branches can only be matched with finite relative accuracy, resulting in finite image tone attenuation. Apart from I/Q imbalance, another practical non-ideality is the leakage of the local oscillator signals to the I/Q mixer output ports, creating another undesired tone at the synthesizer output. A compensation structure based on digital predistortion of the low frequency signals is presented to enhance the signal quality. Furthermore, a simple and practical algorithm for updating the compensator coefficients is proposed based on minimizing the envelope variation of the synthesizer output signal. Simulation results illustrate the performance of the proposed frequency synthesizer concept.
Keywords :
compensation; frequency synthesizers; mobile communication; I/Q mixing; analog synthesis techniques; compensation structure; compensator coefficients; digital predistortion; digital synthesis techniques; envelope variation; finite image tone attenuation; finite relative accuracy; frequency synthesizer concept; low frequency signals; low frequency tone; operating frequencies; power consumption limitations; sideband suppression filtering; signal quality; spectral purity; switching speed; wireless communications; Computer architecture; Energy consumption; Frequency conversion; Frequency synthesizers; Phase locked loops; Signal processing algorithms; Signal resolution; Signal synthesis; Tuning; Wireless communication;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Circuits and Systems, 2003. ISCAS '03. Proceedings of the 2003 International Symposium on
Print_ISBN :
0-7803-7761-3
Type :
conf
DOI :
10.1109/ISCAS.2003.1205896
Filename :
1205896
Link To Document :
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