摘要:

The paper opens with a brief review of gyromagnetic media in general, followed by a more detailed description of the microwave behaviour of a ferromagnetic medium, of which ferrites form a suitable class of material. The general physical properties of ferrites are outlined briefly, together with a description of several of the mechanisms to account for the dispersion which occurs in their r.f. permeability. The propagation of an electromagnetic wave through an infinite ferrite medium is considered. The properties of different guided systems containing ferrites are then studied. The behaviour of various ferrite waveguide structures is described and their applications are suggested. Most of the data quoted are from published papers, but in a few instances some unpublished work of the authors has been included for completeness. An extensive bibliography completes the survey.

DOI:10.1049/pi-b-1.1957.0046

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The paper describes some results of an experimental investigation of the propagation behaviour of circular waveguides containing longitudinally magnetized ferrite rods. Measurements have been made at 9.250kMc/s using nickel–zinc ferrite. Reasonable correlation is obtained between experimental and theoretical results for the limiting cases of the thin ferrite rod and the waveguide completely filled with ferrite. Factors determining the propagation behaviour in the partially filled waveguide are discussed and illustrated by experimental results. The dependence of propagation behaviour on ferrite-rod diameter is studied in detail using polystyrene foam and polystyrene as supporting media.

DOI:10.1049/pi-b-1.1957.0049

出版商:IEE    

年代:1957

数据来源: IET

摘要:

A review is given of the techniques available for measuring the properties of ferrite materials at microwave frequencies. A detailed account is given of permeability and permittivity measurements in the 3 cm band using a cavity technique. The input impedance of an H11-mode cavity loaded with a ferrite disc or sphere is derived by a perturbation calculation. The equivalence between this impedance and the input impedance of two tuned coupled circuits is shown, and hence the ferrite permeability is derived from accepted circuit theory. The range and accuracy of the apparatus is discussed, and the results of measurements on a wide range of ferrites using this technique are presented.

DOI:10.1049/pi-b-1.1957.0050

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The ‘intrinsic’ and ‘external’ permeabilities of a ferrite are defined, and the relationship between the elements of these tensors is discussed. The derivation from Maxwell's equations is given of the magnetic field in a ferrite sphere when this is placed in a uniform microwave field perpendicular to the polarizing field. This result is used in the calculation of the frequency shift which takes place when a ferrite sphere is placed in a resonant cavity. From the frequency shift, the elements of either permeability tensor can be calculated. Also, regarding the frequency shift as complex, the change in the Q-factor on introducing the ferrite sphere can be used to calculate the imaginary parts of these elements. Finally, the derivations of the frequency shift given by previous authors are reviewed, and certain misconceptions and mistakes cleared up in the light of the theory given in the present paper.

DOI:10.1049/pi-b-1.1957.0051

出版商:IEE    

年代:1957

数据来源: IET

DOI:10.1049/pi-b-1.1957.0052

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Nickel ferrite was prepared from pure ferric and nickel oxides by firing at temperatures between 1090 and 1350°C. The influence of the firing temperature on the Faraday effect at 3cm wavelength was studied. Results are reported for nickel ferrites with excess and deficiency of iron oxide, and for nickel ferrite-aluminates. It is shown that low loss combined with high rotation may be obtained by using a composition deficient in iron oxide and firing at a high temperature. The loss in zero field of nickel ferrite may be reduced by replacing a small proportion of the iron by aluminium. Some correlation was found between the microwave loss of these ferrites and the conductivity measured at 10Mc/s. The d.c. conductivity was also measured and compared with the a.c. conductivity.

DOI:10.1049/pi-b-1.1957.0055

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The effect of temperature on some of the properties of ferrites in WG16 rectangular waveguide has been studied between 20 and 300°C. The properties investigated were the zero-field loss, the absorption at ferromagnetic resonance and the external applied magnetic field required for ferromagnetic resonance. For thin samples the variation of the properties can be explained, at least qualitatively, on the existing theory of ferromagnetic resonance, and the slight semi-conductor nature of ferrites. Thicker samples gave more complicated variations probably due to ‘waveguide effects’ resulting from changes with temperature of the complex dielectric constant and the components of the permeability tensor. The behaviour of these samples with changes of temperature cannot easily be predicted. Some of the useful and interesting properties of ferrite inserts of triangular cross-section are given. Two applications of ferrites are described. The first is an absorption isolator capable of dissipating 50 watts mean power in the reverse direction without the need for forced cooling; this device, using ferrite inserts of triangular cross-section, has very broad-band characteristics. The second is a high-speed waveguide switch. The conditions necessary for rapid switching based on Faraday rotation have been investigated and are included.

DOI:10.1049/pi-b-1.1957.0056

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Two methods for the determination of tensor susceptibility components of ferrites, based on an exact solution of the field equations in contrast to the existing perturbation technique, have been developed. They have the advantage of enabling a larger amount of material to be introduced in the cavity, thereby producing a more accurate measurement of the properties of very low-loss ferrites. Also a method for the determination of dielectric constant and scalar permeability is described.

DOI:10.1049/pi-b-1.1957.0057

出版商:IEE    

年代:1957

数据来源: IET

DOI:10.1049/pi-b-1.1957.0058

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The paper gives the results of the extension to higher frequencies than heretofore of work already performed on ferrites and outlines the applications to which these results pertain. The dispersion and absorption occurring in ferrite materials in the presence of an applied magnetic field is briefly mentioned. A description is then given of measurements on typical ferrites with both longitudinal and transverse fields. It is shown how ferrite structures can be made to have nonreciprocal and other useful properties. The paper concludes with a description of the uses of these structures in such applications as switches, duplexers, radiometry and cyclotron resonance detection.

DOI:10.1049/pi-b-1.1957.0061

出版商:IEE    

年代:1957

数据来源: IET