To achieve VSWR of 1 at 2.4GHz using a normal mode helical  RF
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gavinhp

Post subject: To achieve VSWR of 1 at 2.4GHz using a normal mode helical
Posted: Thu Apr 28, 2005 11:07 pm



hi to all, Can anyone help me to the VSWR of
1 at 2.4GHz. the parameter is as following: N=3
raduis of wire =0.3mm diamter of helix coil =3mm
pitch angle =37degree h=2mm right handed helix
2.4GHZ
I attached my file here for ur reference.
** Mesh parameters and points ** d = lamda/4
or 0.125m/4= 0.03125 ** N = 3 turns ** S =
0.00710207960366(Base on pitch angle =37 degree)
** r = 0.0003m or 0.3mm ** D = 0.003m or 3mm
** h = 0.002m or 2mm ** Max wire segment length
= 0.05m or 50mm ** Max Segment Length = 0.0019m
(20 segments in 1 coil) ** All values in m
************************************************************************
********************** ** Tuning Parameter
********************** ** #d is the lambda or
distance between the 2 helical antenna ** #r
is the radius of the helical wire ** #seg is
the number of segments on the helix coil ** #s
is the spacing between coil turn ** #c is the
diameter of the helix coil
** #d = 0.0
** #r = 0.0003 ** #seg = 0.002 ** #z
= 0.0079 ** #c = 0.0023
** Wire
segment length h #h1 = 1.0 #h2 = 1.0
#d = 0.0 **Lambda Distance #e = 0.0 **X coordinate
#r = 0.3 **Helix Radius #seg = 2.0 **Helix
Segment #s = 7.1 **Turn Spacing #c = 3.0 **Helix
Circumference
************************************************************************
** Frequency #freq = 2.4e9
** Parameters
for segmentation IP #r 50
************************************************************************
** Left Side ** Parameters for helix segmentation
LA 1 DP A1 #e #d #h1 DP B1 #e #d #s DP
C1 #c #d #h1
** Right handed helix (1)
HE A1 B1 C1 1 3 #seg
** Define the endpoints
and create the wire segment h DP D1 #c #d #h2
DP E1 #c #d 0
LA 2 BL E1 D1
**********************************************************************
** ** Right Side ** ** ** Parameters
for helix segmentation ** LA 4 ** DP A2
#e #d #h2 ** DP B2 #e #d #s ** DP C2 #c #d
#h2
** Right handed helix (2) ** HE
A2 B2 C2 1 3.0 #seg
** Define the endpoints
and create the wire segment h ** DP D2 #c #d
#h1 ** DP E2 #c #d 0
** LA 5 **
BL E2 D2
***********************************************************************
SF 1 0.001
** End of geometric input EG
1 0 0 0 0
** Specify an infinite ground
plane ** BO 2
**Set Discrete Frequency
2GHz3GHz FR 10 0 0.51e9 2.6e9
**
Voltage gap excitation at a segment ** A2 0 2
1 90 50 A1 0 2 1 90 50 ** A2 1 5 1 90
** Calculate surface currents for current display
OS 1 1
** Horizontal far field pattern
FF 1 1 181 1 90 0 2
** End EN





SMSG 
Post subject:
Posted: Sat Apr 30, 2005 12:48 pm


Joined: Tue Apr 26, 2005
6:47 am Posts: 4 Location: Singapore

since you ar talking about spot frequency at 2.4
GHz you should not find much difficulties to get
this VSWR of 1, plat with the number of turns and
pitch, you should be able to get it,
please
do not stick to the formula dimension play with
your hand and see outcome.....................





Graham 
Post subject:
Posted: Fri Sep 02, 2005 9:02 pm


Joined: Fri Sep 02, 2005
7:25 pm Posts: 34 Location: Hampshire UK

Helix antennas that keep the same pitch all the
way to the reflector plane have an impedance of
about 140 ohms. This assumes you have the feedpoint
right at the point it meets the plane. If you attach
a small strip tab along the last quarterturn as
it approaches the feedpoint, shaped to in effect
"widen" the helix conductor, making increased capacitance
to the plane, you go most of the way to getting
a match.
Next step is to feed it with a signal,
and slightly compress and adjust the helix at that
quarter turn until the VSWR is 1:1, (assumes you
a using a VSWR bridge to get the match).


Posted 11/12/2012







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