In radiofrequency (RF) receivers of communication devices, a carrier signal is typically received via an antenna and then processed by circuitry to obtain a lower frequency baseband signal. Such circuitry have different circuit stages or circuit elements to process the carrier signal. Processing the carrier signal includes amplification, mixing to convert the carrier signal to the baseband signal and filtering of noise or undesired harmonics resulting from the amplication or the mixing.
Performance of the stages or elements can be characterised with parameters such as, for example, a second or a third order intercept point (IP2&IP3). IP2 and IP3 indicates how well such stages or elements perform in the presence of strong nearby signals including noise and undesired harmonics. Such nearby signals cause intermodulation distortion, which affects desired signals that are processed by the stages or elements. In a communication device such as, for example, a two way radio, an overall or system IP2 or IP3 of the (RF) receiver within the two way radio can be degraded by the IP3 of an individual stage or element. One technique to overcome or alleviate degradation of the system IP2 or IP3 is to couple the stages or elements of the (RF) receiver with low impedance stages. Hence, as a low impedance stage, a diplexer typically couples a mixer to a crystal filter in conventional (RF) receivers. Such a diplexer preceeds the crystal filter to thereby provide a low impedance load for the mixer.
However, diplexers do not provide a complete solution to the degradation of the system IP2 or IP3 of (RF) receivers. This is because different types of mixers or crystal filters require different circuitry to be configured for the diplexers. Furthermore, diplexers can be complex and require many discrete elements which, therefore, increase the cost of (RF) receivers.