| 摘要 |
A wireless communication with a receiver subsystem capable of supporting communications operating on two or three distinct frequency bands while incorporating only one or two oscillating devices, respectively. For example, such a subsystem could be integrated in a wireless communication hand-held device configured to operate within three frequency ranges in order to support Cellular, PCS, and GPS services. The receiver subsystem includes a receiver subsystem front end configured to receive first, second, and third receive signals operating under three different frequency bands. The three receive signals are subjected to front-stage filtering, low-noise amplifier, and bandpass filtering in order to remove any unwanted radio frequency components. The first signal is subsequently down-converted into an IF signal by mixing it with a first reference signal generated by a first voltage controlled oscillator (VCO). The first VCO operates with a frequency band that is broader than necessary and generates the first reference signal with a predetermined frequency such that the mixing operation produces a specific common IF frequency. The second signal and third signals are similarly down-converted to a second common IF signal by mixing it with a second reference signal generated by a second voltage controlled oscillator (VCO). The present invention also includes a VCO feedback control loop, including a phased-lock-loop, for maintaining the accuracy and stability of the frequency signals produced by the first and second VCOs. |
