Patent ID: 8428545

Claim:
A circuitry for use in a direct conversion receiving chain for a radio receiver, the circuitry comprising: mixing circuitry configured to downconvert radio frequency signals to baseband; a local oscillator configured to provide a local oscillator signal to the mixing circuitry for use in the downconversion, the local oscillator signal comprising a first component and a second component corresponding to a harmonic of the first component; and a filter circuit configured to filter radio frequency signals input thereto and to output filtered radio frequency signals to the mixing circuitry, wherein the filter circuit is configured to attenuate radio frequency signals output at a first frequency by an amount which is low relative to the attenuation of signals output at frequencies other than the first frequency, and to attenuate signals output at a second frequency by an amount which is high relative to the attenuation of signals output at frequencies other than the second frequency, the filter circuit being tunable such that the first frequency can be tuned to correspond to a frequency of the first component of the local oscillator signal, and the filter circuit being configured such that the second frequency is maintained at a predetermined integer multiple of the first frequency.