The Field Displacement Isolator

The need for passive nonreciprocal structures has long been recognized.1 In the microwave field, Hogan's gyrator 2 paved the way for an increasingly important class of such devices. The isolator, in particular, has emerged as one of the more useful ferrite components. It performs the function, as its name implies, of isolating the generator from spurious mismatch effects of the load. Unlike lossy pads, which consume generator power, the isol^ter provides a unidirectionally low loss transmission path. A. G. Fox, S. E. Miller and M. T. Weiss3 have pointed out that nonreciprocal ferrite devices may exploit any of the following waveguide effects: 1. Faraday rotation 2. Gyromagnetic resonance 3. Field displacement 4. Nonreciprocal phase shift In the present paper we shall discuss an isolator, based upon the field displacement effect, which was developed to meet the following requirements for a proposed microwave relay system (5,925-6,425 mc/sec): 1. Forward loss 0.2 db 877 878 THE BELL SYSTEM TECHNICAL JOURNAL, JULY