Antenna Measurements using Modulated Signals
Author: Roger Dygert
Publication: AMTA 2013
Copyright Owner: NSI-MI Technologies
Antenna test engineers are faced with testing increasingly complex antenna systems, one of these being the AESA (Active Electronically Steered Array) antennas used for cell communications, jammers, and radars. Often these antennas have integrated electronics and RF components that are an intricate part of the antenna, and as a result must be tested with the waveforms generated by the antenna itself. One cannot simply inject an unmodulated continuous wave signal. These antennas require new measurement techniques which are compatible with their broadband waveforms.
The reference channel of a measurement receiver can be used to collapse the spectrum of the modulated signal into a single CW measurement. Done properly all the energy in the signal is captured with noise and interference being dispersed, resulting in no loss of DR (dynamic range) over a CW measurement. A receiver employing this technique can capture all the energy in modulated and pulsed signals wielding wide dynamic range measurements. Phased locked loops (PLL) are not used as they can preclude such measurements.
A measurement receiver that uses a digital correlator to collapse the spectrum of modulated and pulsed signals will be presented. This paper will describe the technique used to do this and show measured results on example broadband signals.