Shark Fin antenna modules containing SDARS LNAs are found in an ever-increasing number of new automobiles sold in North America. These LNAs serve to enhance the overall sensitivity of the SDARS receiver, as well as to compensate for the cable losses between the roof-mounted antenna and the dash-mounted radio.

Since the design of the LNA front end directly impacts the performance of the SDARS radio, Sirius XM™ has created strict guidelines which are outlined within the Standard LNA Performance Requirements section of their Vehicle Mobile Antenna Requirements document. This article addresses these specific design constraints by providing a detailed comparison between the two basic antenna module configurations—namely with and without co-located cellular transmitters. Solutions are also provided for each use case.