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
