Patent GB-1236349-A (GB)
Title: Two-port magnetoelastic delay line
IPC: H03H9/40
Filed: 1969-08-22
Abstract: 1,236,349. Magneto-elastic delay lines. HAZELTINE CORP. 22 Aug., 1969 [24 Sept., 1968], No. 41933/69. Heading H3U. A delay line comprises, Figs. 1a, 1c, a body 10 of ferrimagnetic electrically insulating material, e.g. yittrium iron garnet, supported by a member 11 so that an end face 10a of the body abuts the end face 12a of a block 12 of conducting material, the end face 10a being polished to reflect elastic waves. In Fig. 1c, the body 10 is omitted to show grooves 25, 30 formed in the block face 12a, these grooves facing the end face 10a of the body. Permanent magnets 17, 18 subject the body 10 to a magnetic field which increases in a direction away from the end face 10a as indicated by arrow 29, whereby as waves propagate away from the end face their wavelength decreases. The magnetic field may be shaped to produce either a dispersive or non-dispersive delay line. The input to the delay line comprises a stripline section 13 having a-connector 15 and the output comprises a strip-line section 14 having a connector 16. The section 13 includes a thin conductor 21 situated in the groove 25 and conmected at one end to the ungrounded conductor 24 of the strip-line, the other end being connected at 26 to the bottom of the conducting block 12, the latter being connected to a grounded conductor 23. Similarly, the section 14 includes a thin conductor 22 in the groove 30, one end of the conductor being connected at 31 to the block 12 and the other end being connected to an ungrounded conductor 28. A further grounded conductor 27 is connected to the block 12. The thin conductors 21, 22 are shielded from one another by having their fields confined by the conducting block 12; also, the distance 48 between the conductors must be at least one-third the length L of the conductors. Dielectric strips 39, 40 in the grooves' 25, 30 prevent contact between the conductors 21, 22 and the grooves and the conductors are positioned to make direct contact with the polished face 10a. As shown in Fig. 2, a wave propagated at the launch point 34 in the face 10a, which corresponds to the position of input conductor 21, decreases in wavelength as it moves away from the face due to the magnetic field increasing in direction 29. At the launch point 34 the frequency of the waves may lie in the range 350 MHz to 10 GHz. At the branch point 35 the waves convert to spin waves and at point 36 they convert to elastic waves which are reflected from the face 10a to the point 37. At point 37 they convert back to spin waves and at point 38 they convert to waves of the original high frequency. These waves arrive at the point 46 which is opposite to the wire 22 and are received by the latter as a delayed output signal. In a modification (Fig. 5, not shown), the grooves in the block 12 are omitted and a layer of dielectric material is provided on the face 12a to isolate the conductors 21, 22 from the block. In another embodiment, Figs. 7b, 7c, the YIG body 10 is positioned between two permanent magnets (not shown) as in Fig. 1a and on its polished end face 10a is a thin sheet 57 of conductive material having apertures 58, 59. Thin input and output conductors 60, 63 spaced from the apertures by a thin dielectric sheet 65 are connected at one end at points 62, 66 to the sheet 57. The other ends of the conductors 60, 63 are connected, respectively, to the ungrounded conductors 55, 56 of the input and output striplines having connectors indicated by the dash-line circles 13a<SP>1</SP>, 14a<SP>1</SP>. A grounded conductor 54 common to both input and output is connected to the sheet 57.