Novel Semiconductor Phase Shifters

EE Department.

KFUPM

IEEE-TEM 2000

• Introduction:

• The gyromagnetic properties of magnetized

ferrite is widely used for phase shift section.

• Due to its frequency limitations and high cost, gyroelectric properties of magnetized semiconductors are exploted here for designing millimeter wave phase shifters.

Review of magnetized ferrite phase shifters:

•When magnetized, the magnetic moments of spinning electrons starts to rotate around the axis of Ho, until unidirectional alignment.

•Direction & frequency of rotation depends on Ho. Assume the direction is same as -CP wave

•Propagating EM wave interacts and causes aligned magnetic moments to restart rotating.

•Circularly polarized modes are fundamental for EM wave propagation in biased ferrites.

•So, interaction between ferrite magnetic moments (in -CP direction) and magnetic field component of EM wave ( to Ho) results : =›Accelerated -CP component of mag. field. =›Retarded +CP component of magnetic field.

So, two CP’s are rotated by different angles. Consequently, incident LP wave is rotated.

• Increasing Ho or thickness of the phase phase shift section, increases the phase-shift

• The direction of phase shift depends on the

direction of Ho and not in the direction of

propagating EM wave => nonreciprocity.

• In ferrites, the anisotropic interaction of the magnetic moments and the EM wave is governed by its permeability tensor;

• Typically, [r]50-3000 and r10-20.

• EM field components within ferrite are expressed by substituting [r] and boundary condition into Maxwell’s equations.

where Ko2 = 2oo , ef f= (2-2)/ , R=radius and

(2) 0s

1

s

1 Rn

RsJRs'J

ss

β ε ..μK

RsJRs'J

ss

β rε ..μK

22

21

2

2n

2n2

2

2reff

20

1n

1n1

1

2eff

20

222r

20

22r

20r

20

2

2r

20r

20

222,1

K4

K11K5.0

K11K5.0S

C.E. of Ferrite filled circular wave-guide :

YIG G 113:MS=140 KA/m;r=15.9; Br=1277 G;R=5

eff={2Hin2-f2+22HinM+(M)2}/{2Hin

2-f2+2HinM}

Yig G113: MS=140 KA/m;r=15.9; Br=1277 G;R=5

4.5 5 5.5 6 6.5 7 7.5 8 8.5 9

x 109

10

20

30

40

50

60

70

B-

B+

(Region 1)

TE11

Freq. (GHz)

Rot

atio

n (D

eg./m

)

O

Phase shift per unit length of ferrite (R= mm)

Magnetized semiconductor phase shifters:

•The interaction of Electric field (EM wave) and free electrons of biased semiconductor produces gyroelectric cyclotron motion (of electrons), responsible for phase shift action

•The direction and magnitude of phase shift depends on the direction and magnitude of biasing magnetic field, Ho (and thickness)•Semiconductor phase shifters : nonreciprocal

•According to drude model, the gyroelectric properties of semiconductor is described by;

)1(

)cjf(*

m.o.f

o.f

2e.N

r00

02

)oHoe(2

)}cjf(*

m{

o.f

)cjf(*m.2e.N

r2)oHoe(

2)}cjf(

*m{

o.f

2)oH.o.3e.N

j

02

)oHoe(2

)}cjf(*

m{

o.f

2)oH.o.3e.N

j2

)oHoe(2

)}cjf(*

m{

o.f

)cjf(*m.2e.N

r

r

where Ko2 = 2oo , r= dielectric constant, radius R

C.E. of semiconductor circular wave-guide :

(4) 0s

1

s

1 ..KRn

RsJRs'J

ss

β ..K

RsJRs'J

ss

β..K

23

24

r2

0

4n

4n4

4

2r

20

3n

3n3

3

2r

20

22220

2220

20

2

220

20

224,3

K4

K1K5.0

K1K5.0S

2.8 2.9 3 3.1 3.2 3.3

x 1010

0

500

1000

1500

B-

B+

(Region 2)TE01

Frequency (Hz)

Phas

e C

onst

ant (

B)

-f plot of magnetised semiconductor at Ho=150 KA/m, r=16, N=1e18 m-3, m*/me=0.014, R=1mm

Phase shift per unit length of semiconductor (R=1mm)

2.85 2.9 2.95 3 3.05 3.1 3.15 3.2

x 1010

15

20

25

30

35

40

45

50

O

Freq. (Hz)

Rot

atio

n (D

eg/u

nit l

engt

h)

)6( m .e .N)H . .e(m .f f .

e .N m .e .N .2H . .em .f f .

*22oo

2*2

2*22oo

2*2

eff

For r=16, N=1e18 m-3, m*/me=0.014, R=1mm

For r=12, N=1e16 m-3, m*/me=0.067, R=1mm

• Conclusion:

• Phase shift per unit length is observed for a circular YIG G113 ferrite phaser of 5 mm in radius and magnetized by Ho= 0.5 mT

• Phase shift per unit length is plotted for a magnetized InSb semiconductor phaser of 1mm radius and magnetized by Ho=0.19mT

• For ferrites, the frequency range of 4.5 to 9 GHz was plotted and for semiconductor the frequency range of 28 to 32.5 GHz was observed. The phase shift is noted to increase with frequency.