The focus of this monograph is the development of a low power, radio
frequency transmitter architecture. Specifically, a technique for in service
automatic calibration of a modulated phase locked loop (PLL) frequency
synthesizer is presented and examined in detail. Phase/frequency
modulation is accomplished by modulating the feedback divide value in a
phase locked loop frequency synthesizer [1]. A digital pre-compensation
filter is used to extend the modulation bandwidth by canceling the lowpass
transfer function of the PLL [2]. The automatic calibration circuit
maintains accurate matching between the digital precompensation filter
and the analog PLL transfer function across process and temperature
variations. The automatic calibration circuit, which is the main contribution
of this work, has been designed to operate while the transmitter
is in service. This online calibration eliminates the need for production
calibration and periodic down time for calibration cycles.
Key features of the new calibration system include the following:
High data rate Gaussian Frequency Shift Keying (GFSK) and Gaussian
Minimum Shift Keying (GMSK) modulation.
Support for M-ary FSK modulation.
No required manufacturing calibration.
Potential for low power operation.
Key features of the implemented system include:
RF output carrier center frequency in the 1.88 GHz range.
GMSK/GFSK modulation at 2.5 Mb/s.
4-GFSK modulation at 5.0 Mb/s.
Low power (78 mW) operation.