Novel Semiconductor Phase Shifters

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.


1. LOW LOSS,
ACCURATE
phase shift

2.

Review of magnetized ferrite phase shifters:

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

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

1Damping LOSS

2 CW and CCW

3
-
CP;

until damping

losses stop


•
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
H
o
) 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
.

1.

2. M. field is

†
䡯

㌮卥攠晩g



•
Increasing
H
o

or
thickness

of the phase
phase shift section,
increases

the
phase
-
shift

•
The
direction

of phase shift depends on
the direction of
H
o

and not in the
direction of propagating EM wave =>
nonreciprocity
.

1.rotation of LP

2. Until saturation.


45+45=90



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


•
Typically,
[

r
]

50
-
3000 and

r

10
-
20.

•
EM field components within ferrite are
expressed by substituting
[

r
]

and
boundary condition into Maxwell’s
equations.


where

K
o
2
=

2

o

o
,

ef f
= (

2
-

2
)/


, R=radius
and

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

YIG G 113:M
S
=140 KA/m;

r
=15.9; B
r
=1277
G;R=5


eff
=
{

2
H
in
2
-
f
2
+2

2
H
in
M+(

M)
2
}
/
{

2
H
in
2
-
f
2
+

2
H
in
M
}

Yig G113: M
S
=140 KA/m;

r
=15.9; B
r
=1277
G;R=5

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,
H
o

(and thickness)

•
Semiconductor phase shifters :
nonreciproca
l

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


where

K
o
2
=

2

o

o
,

r
= dielectric constant,

radius R

C.E. of semiconductor circular wave
-
guide :



-
f plot of magnetised semiconductor

at
H
o
=150 KA/m,

r
=16, N=1e18 m
-
3
,
m
*
/m
e
=0.014, R=1mm


Phase

shift

per

unit

length

of

semiconductor

(R=
1
mm)



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



For

r
=12, N=1e16 m
-
3
, m
*
/m
e
=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
H
o
=
0.5 mT

•
Phase shift per unit length is plotted for
a magnetized InSb
semiconductor

phaser of
1mm

radius and magnetized
by
H
o
=
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.