Making Transient Antenna Measurements
Authors: Roger Dygert, Steven R. Nichols
Publication: AMTA 2012
Copyright Owner: NSI-MI Technologies
In addition to steady state performance, antennas also have transient responses that need to be characterized. As antennas become more complex, such as active phased arrays, the transient responses of the antennas also become more complex. Transient responses are a function of internal antenna interactions such as coupling and VSWR, active circuitry, and components such as phase shifters and attenuators. This paper will show techniques for measuring antenna transient responses.
The first measurements utilize standard instrumentation capable of sampling at up to 4 MHz, giving 250 nS time resolution of the transient effect. Recognizing that some transient measurements require finer time resolution, a higher sampling rate prototype receiver was developed with 1 nS time resolution. After verification of its performance, the prototype receiver was used to measure the transient effects of a 50 nS pulse through a broadband antenna. The spectrum of the pulse yields information on the time and frequency domain responses of the antenna.
Phased arrays may exhibit transient signals when switching between beam directions as well as switching between frequencies. The methods presented in this paper are applicable to both.