|Dimensions||1500μm x 1500μm|
Frequency synthesizers provide the local oscillator signal required by wireless transceivers to perform frequency translation from and to the RF band. Extraordinary stiff requirements to the purity and accuracy of the synthesized signal are demanded by GSM and other standards. Besides these constraints, low power consumption and compatibility with standard CMOS are the main synthesizer requirements for cellular handsets.
An integer-N 4GHzfrequency synthesizer with 400kHz frequency resolution has been designed in a 0.18\u03bcm CMOS technology. The integrated circuit provides a dual modulus prescaler designed for minimum power consumption, a frequency divider which is programmable through a serial interface, a phase frequency detector and a charge pump. A few passive components for the loop filter and a voltage controlled oscillator (VCO) module complete the frequency synthesizer.
A novel charge pump circuit, designed for rail-to-rail output operation and for minimum spurious tones generation has been developed. Spurious tones are reduced by a self-calibration technique diminishing the mismatch of the charge pump current sources.
A test board and a PC based control program have been set up to characterize the synthesizer performance. First measurements show the synthesizer to be fully operational.