Patent ID: 6993356
Filing Date: 2006-01-31
Classification: H04B

Abstract:
1. A frequency generating system for a mobile radio transceiver operating in two radio frequency (RF) bands spaced apart from each other, comprising: a transmitter having an intermediate frequency (IF) filter; a receiver having a common highly selective IF filter; and a single voltage controlled oscillator (VCO) connected to said transmitter and said receiver, said voltage controlled oscillator outputting two mutually offset local-oscillator frequency bands including a lower local-oscillator frequency band and a higher local-oscillator frequency band having a higher frequency than the lower local-oscillator frequency band, said transmitter generates a transmit signal, conducted through said IF filter, and with an aid of the lower local-oscillator frequency band the transmit signal is converted into an upper transmit frequency band and a lower transmit frequency band, respectively, and a signal received in an upper receive frequency band and a lower receive frequency band, respectively, in said receiver is converted with an aid of the two mutually offset local-oscillator frequency bands into a receive IF, a frequency conversion into and, respectively, out of an upper band being effected with the lower local-oscillator frequency band and into and, respectively, out of a lower band being effected with the higher local-oscillator frequency band, said common highly selective IF filter being provided for filtering out an IF signal for both the upper band and the lower band in said receiver, the higher local-oscillator frequency band exclusively provided for converting the upper receive frequency band into the receive IF and the lower local-oscillator frequency band provided both for converting the lower receive frequency band into the receive IF and also for converting the transmit signal from an IF into a RF transmit frequency in the upper transmit frequency band and the lower transmit frequency band, an upper transmit IF for conversion into the upper transmit frequency band being identical to a lower transmit IF for conversion into the lower transmit frequency band, and that a percentage frequency difference between the two mutually offset local-oscillator frequency bands is of such a magnitude that both the lower and higher local-oscillator frequency bands can be generated by said single voltage-controlled oscillator functioning as a local oscillator, said voltage-controlled oscillator having a resonator which is electronically switched in a manner of a so-called “band-switched” VCO during band switching without significant impairment of noise characteristics in at least one of the upper and lower local-oscillator frequency bands.