Passive intermodulation distortion filtering

An apparatus for filtering, the apparatus comprising:

• passive means for generating a composite transmit signal by combining multiple radio-frequency transmit signals associated with different transmit frequency bands;
• means for attenuating one or more frequencies within the composite transmit signal that are associated with a receive frequency band to generate a filtered composite transmit signal;
• and
• means for transmitting the filtered composite transmit signal using a feed that is separate from another feed used to receive a radio-frequency receive signal associated with the receive frequency band.

A method for filtering, the method comprising:

• accepting multiple radio-frequency transmit signals associated with different transmit frequency bands;
• passively combining the multiple radio-frequency transmit signals together to generate a composite transmit signal;
• attenuating one or more frequencies within the composite transmit signal that are associated with a receive frequency band to generate a filtered composite transmit signal;
• and
• passing the filtered composite transmit signal to a feed of an antenna that is separate from another feed of the antenna associated with receiving a radio-frequency receive signal, the radio-frequency receive signal associated with the receive frequency band.

A radio-frequency front-end circuit comprising:

• a multiplexer comprising multiple band-pass filters configured to have different frequency responses associated with different transmit frequency bands;
• and
• a filter coupled to an output of the multiplexer, the filter configured to:
• be coupled to a feed of an antenna that is separate from another feed that is to be used to receive a radio-frequency receive signal;
• and
• have a frequency response that represents a combination of the different frequency responses of the multiple band-pass filters.