Background

For all the headlines and personal anecdotes lamenting how commercial air travel isn’t what it used to be, there are some clear benefits enabled by recent advances in technology we might be taking for granted. One of these is in-flight internet service. Whether domestic or international, most flights now offer internet service via satellite, allowing passengers to remain connected for personal and business use throughout the majority of their journey.

For most aircraft in service today, the satellite up/downlink connection is achieved with a mechanically steerable antenna mounted to the top of the fuselage. The antenna has a limited range of motion to maintain connection with the satellite while compensating for the movements of the aircraft during normal flight operation. These mechanical systems are now giving way to electronically steerable systems using phased array antennas to deliver more reliable connectivity with lower costs of operation and maintenance for the carriers.

While the older mechanical systems used a few RF filters in the transmit and receive paths, the newer phased array designs incorporate multiple antenna elements, each of which requires a set of filters. This evolution in hardware has created a need for filters that are small enough to fit in the compact assembly while providing the necessary rejection and selectivity in the necessary application bands. Until recently, designers typically had to choose between the high Q of filters using air cavities or discrete elements and the smaller size and better manufacturability of surface-mount designs with shallower rejection floor and gentler slope in the transition band. Fortunately, Mini-Circuits recent innovations in LTCC filter design offer the best of both worlds.