Hexagonal ferrites for use in microwave notch filters and phase shifters

Abstract

Recently there has been interest in small, planar, high frequency (10–50 GHz) signal processing devices which are based on metallic ferromagnets. This paper, in contrast, presents theoretical results for devices utilizing a hexagonal ferrite. The notch filter results show attenuation of frequencies in the 40–60 GHz range with applied fields in the 1–5 kOe range. For geometries similar to the ultrasmall metallic devices, the transmission loss at the notch can be from 20 to 140 dB/cm depending on the thickness of the hexagonal ferrite film and the inclusion of dielectric spacers. The phase shifter results show phase shifts of up to 360°, with losses below 2 dB/cm. These results are obtained for devices using thin films around 1 μm in thickness for the hexagonal ferrite, and for reasonable linewidths below 200 Oe.

M-Type Barium Hexagonal Ferrite Films

“…It should be noted that previous theoretical calculations for microstrip geometry had shown that the position of the dip in transmission did not necessarily occur at the same frequency as the maximum absorption in a FMR experiment. 20 The field correction found here is consistent, in magnitude and sign, with the shift found in Ref. [20].…”

“…20 The field correction found here is consistent, in magnitude and sign, with the shift found in Ref. [20].…”

“…10,[18][19][20][21][22][23][24] Such devices include (1) notch filters made of BaM thin films and microstrip geometry, (2) notch filters made of BaM slabs and strip-line geometry, (3) selfbiased notch filters using high-M r BaM thin films and coplanar waveguide (CPW) geometry, (4) notch filters based on the excitation of confined magnetostatic waves in narrow BaM strips and CPW configurations, and (5) phase shifters using BaM thin films and CPW geometry. This section describes the device configurations and responses of (3), (4), and (5).…”

“…Emphasis has been placed on the optimization of deposition processes for low-loss, self-biased BaM thin films, 7,8,9,10 the deposition of BaM thin films on "non-conventional" substrates, such as semiconductor substrates 11,12,13,14 and metallic substrates, 15 the fabrication of BaM thick films on semiconductor substrates, 16,17 the demonstration of BaM-based planar mm-wave devices, 18,19,20,21,22,23,10,24 the development of BaM-based ferromagnetic/ferroelectric heterostructures, 25,26,27,28,29 and the study of multiferroic effects in single-phase BaM materials. 30 A variety of different techniques have been used to fabricate BaM film materials.…”

“…These include pulsed laser deposition (PLD), 7,8,9,10,11,12,28,31 liquid phase epitaxy (LPE), 32,33,34,35 RF magnetron sputtering, 36,37,19,38,39,40 molecular beam epitaxy (MBE), 14 metallo-organic decomposition (MOD), 15 chemical vapor deposition (CVD), 41 and screen printing. 16,17 The device demonstration includes both numerical 20,21,22 and experimental efforts. 18,21,22,23,10,24 The devices demonstrated include phase shifters, 21 filters, 22,23,10 ,24 circulators, 18 and isolators.…”