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Material characterization for the 18 MHz to 40 MHz sweep-tuneable RF system. Christine Vollinger, Erk Jensen. Measurement support by Fritz Caspers. RF tuning cavity with magnetic bias. E xample for parallel bias (from Gardner, 1991). E xample for perpendicular bias (from Friedrichs , 1991). - PowerPoint PPT Presentation

Slide 1

Christine Vollinger, Erk JensenMaterial characterization for the 18 MHz to 40 MHzsweep-tuneable RF systemMeasurement support by Fritz CaspersRF tuning cavity with magnetic bias

Example for perpendicular bias (from Friedrichs, 1991)

Example for parallel bias (from Gardner, 1991)2From Talk of Erk in PS2 Review:Parallel plus perpendicular biasing possible?Smythe suggested in 1983 to usetransverse bias to get into saturation (lower losses)addl. parallel bias for tuning (less bias).Could this work? (Id like to try!)

3Leads to two primary goals:Characterization of ferrite samples with different saturation and line widths under different bias conditions in the required f-range. (This required a dedicated test set-up, since supplier data does not exist PART 1). Verification of Smythes claims (PART 2).First requirement for an f-range of 18-40 MHz is a -range of approx. 5 (since f 1 / Sqrt[] ).Ratio of maximum to minimum f is given by Sqrt[max/ min]; max is the value at minimum bias field.

4Measurement Set-up Problematic: samples are available in sizes 1 x 1 (or smaller); Small sample size led to strip-line set-up on ferrite; 1-port frequency swept measurement with NWA chosen to obtain s11. From s11, the DUT impedance is determined and the can be calculated; Measurement taken with magnetic bias field applied perpendicular to signal propagation; Carries the assumption that the magnetic RF-field left/right of the strip-line can be neglected (there the bias field would be parallel).

HbiasCoaxial connectionFerriteStrip-line5 for Material #1 (Y36)

-ratio:

(20 MHz,300 G)/(40 MHz, 1005 G)=4.0 -ratio:

(20 MHz,145 G)/(40 MHz, 1005 G)=11.16 for Material #1 (Y36)

-values:

(20 MHz,145 G)= 6.3(20 MHz,300 G)= 0.2(40 MHz,1005 G)= 0.074

7 for Material #2 (G300)

-ratio:

(20 MHz,145 G)/(40 MHz, 1005 G)=9.0 -ratio:

(20 MHz,300 G)/(40 MHz, 1005 G)=2.88 for Material #2 (G300)

-values:

(20 MHz,145 G)= 10.1(20 MHz,300 G)= 0.12(40 MHz,1005 G)= 0.076

9 for Material #3 (G810) -ratio:

(20 MHz,558 G)/(40 MHz, 1008 G)= 5.8 -ratio:

(20 MHz,153 G)/(40 MHz, 1008 G)= 8.5

10 for Material #3 (G810)

-values:

(20 MHz,153 G)= 11.9(20 MHz,558 G)= 1.2(40 MHz,1008 G)= 0.03

11 for Material #4 (RG3)

-ratio:

(20 MHz,145 G)/(40 MHz, 1004 G)= 12.5 -ratio:

(20 MHz,349 G)/(40 MHz, 1004 G)= 3.1412 for Material #4 (RG3)

-values:

(20 MHz,145 G)= 17.01(20 MHz,349 G)= 0.1(40 MHz,1004 G)= 0.05

13Summary (1/3) Four ferrite samples have been ordered from industry and measured in an external magnetic bias field. This allowed the determination of their available -range and the corresponding values of as a function of frequency and Bias-field. Requirement for an f-range of 2.2 from 18-40 MHz is a -ratio of approx. 5.Y36G300G810RG3-ratio, [145 1005 Gauss]11.1(,145 G= 6.3)(,1005 G = 0.074)9.0(,145 G= 10.1)(,1005 G = 0.076)8.5(,153 G = 11.9)(,1005 G= 0.03)12.5(,145 G = 17.01)(,1005 G= 0.05)-ratio, [300 1005 Gauss]4.0(,300 G= 0.2)(,1005 G = 0.074)2.8(,300 G= 0.12)(,1005 G = 0.076)-----ratio, [558 1008 Gauss] ----5.8(,558 G = 1.2)(,1005 G= 0.03)---ratio, [349 1004 Gauss] ------3.14(,349 G = 0.1)(,1004 G = 0.05)14Summary (2/3) Measurement set-up is found that appears robust and stable (1-port-measurement with NWA). More ferrite samples from different suppliers are already ordered for measurement. Next step will be to investigate potential non-linearity of the materials, if exposed to moderate power (IP3 measurement).15Leads to two primary goals:Characterization of ferrite samples with different saturation and line widths under different bias conditions in the required f-range. (This required a dedicated test set-up, since supplier data does not exist PART 1). Verification of Smythes claims (PART 2).16Verification of Smythes Claims (PART 2)Smythe suggested in 1983 to usetransverse bias to get close to saturation (reduces losses)additional parallel bias for tuning (less bias required for same -range).

17

HappliedMeasurement Set-up

HappliedHtuneHbias

for Material #2 (G300) in 2-Directional Magnetic BiasChange of 55 G (parallel) with 200 G perpendicular -> -ratio > 6 -ratio with Hperp=200G:

(20 MHz,HparBias=18 G)/(40 MHz, HparBias=200 G)= 6.4

19 for Material #2 (G300) in 2-Directional Magnetic Bias -values with Hperp=200G :

(20 MHz, Hpar=18 G) = 1.23(20 MHz, Hpar=73 G)= 0.106(40 MHz, Hpar=200 G)= 0.105

20Contour-plots Smythe and G300 MaterialRF field direction

Hpar/4MsHperp/4MsPlot of SmytheMeasured Data21Summary (3/3)22 The idea of Smythe to use a 2-directional magnetic bias field appeared in 1983, but (to my knowledge) has never been used or further investigated. Smythe had no measurement data to support his claims.

From the measurement done on the G300 sample, it appears as if the method is promising and could work; we will continue further tests with other samples and higher parallel bias fields.G300 with perpendicular biasG300 with 2-directional bias-ratio, [300 1005 Gauss]4.0(,300 G= 0.2)(,1005 G = 0.074)---ratio, [ 200 Gauss perpendicular] &[18 200 Gauss parallel]--6.4(,18 G= 1.23)(,200 G = 0.105)23I would like to thank Fritz Caspers for his strong and unfailing support with all kind of measurement problems!