New structures for six-port reflectometers covering very large bandwidths

This paper presents two new structures for six-port reflectometers with very large operating bandwidths of more than three decades, using a combination of lumped reflectors and transmission lines. Circuits working over a range of 2-1300 MHz and 2-2200 MHz have been built using inexpensive passive surface mount elements and Schottky detector diodes. Comparing results obtained from the new proposed structures with those obtained from a commercial network analyzer show a worst case absolute value of 0.020 for the complex difference between the measured reflection coefficients. A convenient calibration procedure, for the entire band, is proposed using three standards and four approximately known loads.