APPLICATION OF NON-BIASED FERRITES

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Randall Osborne
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1 IMS-004 Workshop WMH APPLICATION OF NON-BIASED FERRITES FOR THE SUPPRESSION OF EMI FROM RF TO MM WAVES Karén Kocharyan RENAISSANCE Electronics Corporation 1 Lancaster County Rd., Harvard, MA kkocharyan@rec-usa.com

2 OVERVIEW Dispersion of Initial Magnetic Permeability Ferrites for Wire Line EMI Filters Ferrite Microwave Absorbers MM-Wave Ferrites and Characterization Conclusion K. Kocharyan

3 COMMON AND DIFFERENTIAL MODES IN WIRE LINES S I S I C I D L N D N C K. Kocharyan 3

4 SUPPRESSING COMMON MODE NOISE WITH CHOKE COIL S 1 L N Frequency Characteristics Design Limitations K. Kocharyan 4

5 SUPPRESSING DIFFERENTIAL MODE WITH BAND-REJECT FERRITE FILTER S Z F N D Z S Z L L IL(dB) = 0 log 10 (ZS + ZL + Z (Z + Z ) S L F ) Differential Mode Noise and Signal at Different Frequency Bands K. Kocharyan 5

6 DISPERSION OF INITIAL MAGNETIC PERMEABILITY m m m I II 1 m f(khz) 10 I Domain Wall Resonance II Natural Magnetic Resonance K. Kocharyan 6

7 EQUIVALENT CIRCUIT OF INDUCTANCE INCORPORATING FERRITE CORE X L (f) R S (f) Z Z F = R S + X L N = 3 where X L = wl 0 m R S = wl 0 m L 0 ~ N - air core inductance Z F 1 N - the number of turns Ferrite EMI Filters operating at resistive mode do not introduce parasitic oscillations and signal distortions! R S X L f K. Kocharyan 7

8 MAGNETOCRYSTALLINE ANISOTROPY AND NATURAL MAGNETIC RESONANCE w 0 = gh int H int = H 0 + H A + H i (M) H 0 external magnetic field H A effective field of magnetocrystalline anisotropy H i (M) magnetization-dependent terms at H 0 = 0, M = 0 and H i (M) = 0 H int = H A w NR = gh A w NR frequency of natural magnetic resonance K. Kocharyan 8

9 EVALUATING ANISOTROPY FIELD IN ISOTROPIC FERRITES H A *) = K 1 /M S K 1 constant of cubic anisotropy M S /3K 1 H M S /3m *) Soft ferrite manufacturers usually do not specify this parameter K. Kocharyan 9

10 SNOEK S LIMIT ON RF PERMEABILITY OF ISOTROPIC FERRITES CUBIC SYMMETRY IMPLIES LOW MAGNETIC ANISOTROPY: K J/m 3 H A < Oe f NR = 500 MHz S = fm = gm S /3 = 5 GHz E.W.Gorter, Proc. IRE 43, 45, (1955) K. Kocharyan 10

11 HEXAGONAL FERRITES WITH UNIAXIAL MAGNETIC ANISOTROPY K 1 constant of axial anisotropy K constant of in-plane anisotropy C K 1 >> K C M K 1 > 0 K 1 < 0 easy axis easy plane M K.Kocharyan 11

12 SNOEK S LIMIT ON PERMEABILITY OF EASY-PLANE HEXAFERRITES H A1 ~ 10,000 Oe H A ~ 100 Oe f NR = g (H A1 H A ) / p ~ 1GHz S = gm S sin q 0 (H A1 /H A ) 1/ ~ 15 GHz Jonker, Wijn and Brawn, Phillips, Tech. Rev., 18, 150 ( ) K. Kocharyan 1

13 HEXAGONAL FERRITES WITH EASY-AXIS ANISOTROPY TYPICAL CHARACTERISTICS H A1 = 000-0,000 Oe f NR = gh A1 / p ~ 6-60 GHz m, m ~ e ~ 18-0 s ~ (MOhm m) -1 e ~ K. Kocharyan 13

14 MICROWAVE FERRITE ABSORBERS FOR WIRELESS APPLICATIONS Broader Bandwidth m is strongly dispersive Thinner Absorber k ~ (m e + e m ) / (m e ) 1/ Available Forms Ferrite Tiles Ferrite Composites Ferrite Paints K. Kocharyan 14

15 METAL-TERMINATED FERRITE ABSORBER Z * in = µ e * * tanh j pdf c µ * e * * * RL < 0dB Zin Z Zin + Z Computational Methods Matching Solution Map (Cole-Cole magnetic diagram) K. Kocharyan 15

16 BROADBAND FERRITE ABSORBER DESIGN PARAMETERS INPUT PARAMETERS Dispersion of Complex Magnetic Permeability Complex Dielectric Permittivity Required Suppression Level OUTPUT PARAMETER Range for product - (fd) K. Kocharyan 16

17 MM-WAVE MATERIAL CHARACTERIZATION METHODS Waveguide - rectangular/cylindrical sample - deteriorating effect of the air gap - standard equipment Coaxial Line - complicated sample geometry - moderate accuracy - standard equipment Quasi-Optical - simple sample geometry - high accuracy - custom designed spectrometer K. Kocharyan 17

18 BLOCK DIAGRAM OF QUASI-OPTICAL MM-WAVE BWO-SPECTROMETER *) S BWO N I II *) At TUFTS University, Medford, MA K. Kocharyan 18

19 TECHNICAL CHARACTERISTICS OF BWO-SPECTROMETER RADIATION SOURCE - Backward Wave Tubes RADIATION TYPE - Coherent, Tunable POLARIZATION - Linear/Circular DETECTORS - Diodes/Bolometer SCAN RANGE (GHz) ; 44-76; SCAN STEP - 3 MHz SCAN TIME (1000 point) - 1 min. DYNAMIC RANGE - > 40 db MAGNETIC FIELD - up to 15 koe K. Kocharyan 19

20 EQUATIONS T R = = E E t i E E r i = = E[ ( 1 R0 ) + 4R0 sin ϕr ] ( 1 ER0 ) + 4ER0 sin ( A + ϕ r ) R0 [( 1 E) + 4E sin ( A + ϕr )] ( 1 ER ) + 4ER sin ( A + ϕ ) 0 0 r R 0 ( a 1) + b ( a + 1) + b b = ϕ r = atan a + b 1 ( c) E = exp 4πkdf a + jb Z * = µ * ε * A = πndf c n jk = µ * ε * K. Kocharyan 0

21 APPROXIMATIONS Dielectric Permittivity, ε * = ε - jε : ε = const ε ε Magnetic Permeability, µ * = µ - jµ : oriented ceramic: µ jµ = [( f AC + fm ) f ] ( f AC f ) randomly oriented: µ jµ = 1 + [( f + f ) f ] ( f f ) AC σ f f = f + jα f f = γh π, f = γm π AC NR G, NR A M S M AC f NR, α G, f M, ε, ε 0, σ Simulation Parameter Set K. Kocharyan 1

22 EXAMPLE 1: LOW-LOSS CERAMIC Transmittance Experiment Theory Frequency, GHz Reflectance Experiment Theory Frequency, GHz a) b) MM-Wave transmission a) and reflection b) spectra of M-(easy-axis) type oriented Bahexaferrite ceramic. Wave propagation is along the direction of orientation. Sample thickness is 1.67 mm. K. Kocharyan

23 EXAMPLE 1: BEST-FIT PARAMETERS Real Permeability, m' Frequency, GHz Imaginary Permeability, m'' 10 3 f M (GHz) f NR (GHz) σ (MOhm m) -1 α G ε ε < K. Kocharyan 3

24 Transmittance EXAMPLE : LOSSY CERAMIC Experiment Theory Frequency, GHz Reflectance a) b) Experiment Theory Frequency, GHz MM-Wave transmission a) and reflection b) spectra of lossy M-(easy-axis) type oriented Ba-hexaferrite ceramic. Wave propagation is along the direction of orientation. Sample thickness is 9.67 mm. f M (GHz) f NR (GHz) σ (MOhm m) -1 α G ε ε K. Kocharyan 4

25 CONCLUSION In Wire Line EMI Applications the Anisotropy Field of Ferrite Core Should Match to the Noise Spectrum Hexagonal Ferrites with Uniaxial Anisotropy are Suitable for Application at Short Microwaves Quasi-Optical BWO Spectroscopy Allows Complete MM-Wave Characterization of Ferrite Materials K. Kocharyan 5

Characteristic of Capacitors

3.5. The Effect of Non ideal Capacitors Characteristic of Capacitors 12 0 (db) 10 20 30 capacitor 0.001µF (1000pF) Chip monolithic 40 two-terminal ceramic capacitor 0.001µF (1000pF) 2.0 x 1.25 x 0.6 mm