GB1515333A - Broad band field displacement isolator - Google Patents

Abstract

1515333 Field-displacement isolators RYT INDUSTRIES Inc 23 May 1975 [6 Aug 1974] 22957/75 Heading H1W A stripline field-displacement isolator comprises a planar circuit member 14 having three limbs, two of which (16, 18) provide input/output ports and are symmetrically arranged with respect to a third limb 20 to which they are joined by edges each formed as a series of linearly tapered impedance-transformer sections 22. Plates 24, 26 of gyromagnetic material are arranged on either side of the limbs of the member 14 forming the input/output ports and pairs of plates 28, 30; 32, 34 of dissipative material are arranged on either side of the third limb 20. The gap between the edges of the gyromagnetic and the dissipative plates may be adjusted to maximize coupling between the same. The circuit is completed by a pair of ground planes 36, 38. Bias field is provided by permanent magnets 42, 44 and the magnetic circuit is completed by cover plates 46, 48. A plate 54 of high permittivity material may be arranged near the edge joining the input and output ports to compensate parasitic inductance appearing at this edge. The length of each transformer section 22 is #/4 where # is the wavelength in the gyromagnetic material at a frequency about 1À2 to 2À4 times the low bandedge frequency. The size of the steps between the transformer sections 22 increases towards the third limb 20. In a modification (Fig. 4, not shown), the edge joining the input/output ports is curved and is also provided with transformer sections.