Abstract: Techniques for using a narrow filter located before a power amplifier to reduce interference in an adjacent frequency band are disclosed. In an exemplary design, an apparatus (e.g., a wireless device) includes the narrow filter and the power amplifier. The narrow filter is for a first frequency band (e.g., Band 40) and has a first bandwidth that is more narrow than the first frequency band. The narrow filter receives and filters an input radio frequency (RF) signal and provides a filtered RF signal. The power amplifier receives and amplifies the filtered RF signal and provides an amplified RF signal. The apparatus may further include a full filter for the first frequency band and located after the power amplifier. The full filter receives and filters the amplified RF signal and provides an output RF signal when it is selected for use.

Abstract: Techniques for detecting and correcting phase discontinuity of a local oscillator (LO) signal are disclosed. In one design, a wireless device includes an LO generator and a phase detector. The LO generator generates an LO signal used for frequency conversion and is periodically powered on and off. The phase detector detects the phase of the LO signal when the LO generator is powered on. The detected phase of the LO signal is used to identify phase discontinuity of the LO signal. The wireless device may further include (i) a single-tone generator that generates a single-tone signal used to detect the phase of the LO signal, (ii) a downconverter that downconverts the single-tone signal with the LO signal and provides a downconverted signal used by the phase detector to detect the phase of LO signal, and (iii) phase corrector that corrects phase discontinuity of the LO signal in the analog domain or digital domain.

Abstract: Techniques for detecting and correcting phase discontinuity of a local oscillator (LO) signal are disclosed. In one design, a wireless device includes an LO generator and a phase detector. The LO generator generates an LO signal used for frequency conversion and is periodically powered on and off. The phase detector detects the phase of the LO signal when the LO generator is powered on. The detected phase of the LO signal is used to identify phase discontinuity of the LO signal. The wireless device may further include (i) a single-tone generator that generates a single-tone signal used to detect the phase of the LO signal, (ii) a downconverter that downconverts the single-tone signal with the LO signal and provides a downconverted signal used by the phase detector to detect the phase of LO signal, and (iii) phase corrector that corrects phase discontinuity of the LO signal in the analog domain or digital domain.

Abstract: Techniques for using a narrow filter located before a power amplifier to reduce interference in an adjacent frequency band are disclosed. In an exemplary design, an apparatus (e.g., a wireless device) includes the narrow filter and the power amplifier. The narrow filter is for a first frequency band (e.g., Band 40) and has a first bandwidth that is more narrow than the first frequency band. The narrow filter receives and filters an input radio frequency (RF) signal and provides a filtered RF signal. The power amplifier receives and amplifies the filtered RF signal and provides an amplified RF signal. The apparatus may further include a full filter for the first frequency band and located after the power amplifier. The full filter receives and filters the amplified RF signal and provides an output RF signal when it is selected for use.