NEW METHODS FOR MEASURING SPURIOUS EMISSIONS

The experimental results obtained with two methods of measuring the spurious emission power of microwave transmitters are reported-the fixed-probe method which measures the waveguide power by means of probes located on the boundary of an enlarged waveguide and the movable-probe method which measures the waveguide power by means of movable probes that scan a plane transverse to the direction of propagation in the enlarged waveguide. With the fixed-probe method an accuracy of 0.26 db was obtained at 9.755 kmc when measuring the waveguide power with a typical S-band doorknob coaxial-to-waveguide transition. SWR and high-power tests made on the new multimode load are described. High-power tests of the line-stretcher and fixed-probe section at a level of 3.1 megawatts gave no indication of breakdown. A new four-band fixed-probe section and a trombone-type line stretcher are described. In connection with the movable probe method, the directivity of the new Z-axis balanced dipole probe was greater than 14 db at 3.8 and 5.0 kmc. At 5.0 kmc, a power measurement accuracy of 0.04 db was obtained. The new probes were tested at a level of 500 kw with no indication of breakdown. Author