NEW METHODS FOR MEASURING SPURIOUS EMISSIONS

Newer, simpler, and more accurate methods of measuring the spurious emission power of microwave transmitters were investigated. Two of these methods--the fixed probe and the movable probe methods--measure the power in the waveguide. A third, the free-space method, measures the power outside the transmission line. All of the methods are capable of accuracies of 1 db or better. In all three methods, the electric-field amplitude is measured in a region where the modal phase constants and the wave impedance have essentially their free-space values. For the waveguide methods, this region is an oversize section of waveguide. For the free-space method, this region is out side the transmission line. The fixed-probe method lends itself most readily to automatic instrumentation and received the greatest emphasis during this program. Instrumentation was developed to measure peak power levels as low as -40 dbm in the 3 to 10 Gc frequency range in less than 5 minutes per frequency. Primary emphasis was on measurements of power flow into matched loads. However, the extension of the fixed probe method to the measurement of power transferred into mismatched loads is also described.