| 摘要 |
The invention provides a switchable up-conversion loop for a transmitting stage of a mobile phone having multiple transmitting frequency bands, said up-conversion loop comprising a phase detector (21) generating a phase detector output signal in response to the phase difference between an input signal and a mixing product signal, multiple switchable voltage controlled oscillators (35, 37; 100, 101, 102; 111, 112; 120), each connected to the phase detector (21) for generating an output oscillation signal the frequency of which depends on the phase detector output signal, and a coupling means (44; 110; 119; 121) for coupling the output oscillation signal to a mixer (26) for mixing said output oscillation signal with a locally generated oscillation signal to produce said mixing product signal. <IMAGE>
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