Filter circuitry

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.