GB1416474A - Tunable ferrimagnetic resonant circuit arrangement - Google Patents

Abstract

1416474 Ferrimagnetic devices; frequency discriminators; radio receiving circuits VARIAN ASSOCIATES 19 March 1973 [22 March 1972] 13075/73 Headings H3U H3A and H3Q In a tunable ferrimagnetic resonant circuit arrangement, the resonant frequencies of a pair of frequency selective circuits are controlled by having parts of each circuit magnetically coupled to pairs 2, 7, resp. 35, 36, see also Figs. 3, 12 (not shown) of ferrimagnetic resonator bodies whose resonant frequencies are proportional to an applied magnetic field in virtue of the gyromagnetic ratio of the electrons they contain, the pair 2, 7 being subjected to the magnetic field H provided by coils 31, 32 coaxial with polepieces 24, 25 of soft iron shell 27, the pair 35, 36 additionally being subjected to an offset field #H provided by auxiliary winding 34. The arrangement is tuned by sweeping the field H under the control of generator 37, the offset field #H ensuring that the difference between the resonant frequencies of the two circuits remains constant as they are both tuned together. A second generator 38, swept in synchronism with generator 37, allows for slightly different tuning rates in the respective circuits. Heterodyning arrangement.-The resonator bodies 2, 7 comprise part of a filter (11), Fig. 7 (not shown), resonators 35, 36 forming part of a local oscillator (17), the intermediate frequency (f 1 -f 2 ) corresponding to the offset field #H. Fig. 11 (not shown) displays an alternative local oscillator discriminator (49) comprising loops (54-55, 54-56), Fig. 12 (not shown), coupling both resonators to a differential amplifier (57) providing a D.C. signal whose sign changes as the input frequency on coax (53) varies on either side of the desired operating frequency of the oscillator, see Fig. 13 (not shown). The discriminator (49) controls a varactor tuned transistor, or backward wave, oscillator (48) providing the local oscillator output, which additionally provides the discriminator input. The pre-filter, and local oscillator are inter-connected in the manner of units (11, 17, Fig. 7). The resonator bodies are yttrium iron garnet, gallium yttrium iron garnet, or lithium ferrite. It is stated that the required degree of temperature regulation of the sweep generators is much reduced for given circuit performance, as compared with the known use of separate magnetic fields for each of pairs 2, 7, resp. 35, 36.