Antennas, Base and Mobile Stations -10.Frequency Synthesizer
As the system allocates limited frequency bandwidths to each mobile station, the mobile terminal must be prepared to instantly respond no matter what frequency bandwidth the base station designates. This requires a local oscillator that can set up frequencies for certain intervals on the mobile terminal side. In order to avoid interference with other channels resulting from deviations in the setup frequency at the local oscillator, however, improved precision in synthesizer oscillation frequencies became an issue affecting the operation of the overall system.
In addition to technological progress in frequency synthesizers from the 150-MHz multiple type to 800-MHz direct oscillation demultiplying type, we developed REFRESH-AFC that calibrates frequencies using highly stable reception waves from the base station, as well as SPILL that is used for intermittent operations. As faster channel switchover is required by the TDMA system used in digital communications, we also developed various high-speed switchover synthesizers including the TC-DLPS synthesizer.
Frequency Stability in FDMA Mobile Communications