H - Electricity – 04 – Q
Patent
H - Electricity
04
Q
H04Q 7/32 (2006.01) H03J 7/06 (2006.01) H04B 1/40 (2006.01)
Patent
CA 2158774
In the frequency synthesizer described in the present invention, the stable transmission frequency required by the digital operating mode is created from a frequency produced by a free running oscillator and which includes frequency errors. A local frequency (f1) and an intermediate frequency (fIF) including frequency errors are input to a mixer (105) located in the signal path of the transmitter. A transmission frequency transmission signal (fTX) is input to a phase-lock loop with a voltage-controlled oscillator (103) that produces the local frequency (f1). Thereby the frequency error caused by the intermediate frequency (fIF) can be corrected with the local frequency (f1) by adjusting the voltage- controlled oscillator (103) of the loop with a voltage (VD) that is proportional to the phase difference between the transmission frequency signal and a reference signal (VREF) input to a phase comparator. This is implemented by connecting the mixer (105) to the loop during the transmission time period with a controllable switch (104), for example. The local frequency (f1) of the receiver is produced with the frequency synthesizer described in the present invention by disconnecting the mixer (105) from the loop. The invention can be applied in producing frequencies for radio telephones that include dual-mode operating modes and exclusively digital operating modes.
Hulkko Jaakko
Vuolteenaho Merja
Nokia Mobile Phones Ltd.
Sim & Mcburney
LandOfFree
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