Influence of the airframe on the performance of antennas for avionics

The performance of antennas mounted on airframes is an important factor in the design of airborne radio systems, and is considered at an early stage in the study and definition of the system requirements for any particular aircraft and associated operational scenario. This is becoming critical as the number of systems and their complexity increases, and as the number of associated antennas required is further multiplied in the application of such techniques as adaptive array signal processing. The infuences of the airframe environment on antenna properties such as radiation pattern, gain, impedance, polarization and coupling, and means of quantifying such influences are discussed. Related electromagnetic structure-dependent effects due to non-linear junctions, and the use of carbon fiber composite materials are also considered. The limitations of system performance resulting from airframe-antenna interaction are difficult to quantify, since detailed knowledge of particular system parameters, associated hardware, and operational scenarios is required.