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Helical antenna Ground Plane

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hyperbola

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helical antenna design equations

Hello,
I am trying to integrate a helical antenna into a communication system.My system consists of a Tranceiver from TI which gives an output of 10 db. The helical antenna(single feed) has bandwidth in the ISM band 433 MHz.The antenna has 24.5 turns,1.428 mm pitch,outer dia of 5.3mm,inner dia of 3.8mm.The antenna requires a ground plane.My questions are 1. How much are ground plane i require?
2.if i miniaturise the antenna to 6 turns, can i reduce the ground plane accordingly.

My application calls for miniaturisation.hoping to get a reply

with regards
hyperbola
 

ground plane helix

there are some antenna projects on the web do a search
 

For best performance in Helix antenna design the diameter of the ground plane should be greater than 3λ/4. The antenna works with smaller ground planes, but with lower efficiency.
The dimension of the ground plane doesn’t have anything with the number of turns, only with the wavelength where the antenna resonate.
 

    H

    hyperbola

    Points: 2
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Thanks for your replies.
However I have a severe area constraint for the ground plane.Also is it possible to
reduce the size of the helix considerably to about 6 turns and get 433MHz performance of 10 db or nearby.
Are there any design equations for helix

rgds
 

Helix in Normal mode:
- Diameter: D = (√2*S* λ) / Π
- Pitch angle: tan α = (Π*D) / (2* λ)


Helix in Axial mode:
- Diameter: 3/4 < [(Π*D) / λ] < 4/3 or D = λ / Π for optimum performance
- Spacing between turns: S = λ/4 or S = 0.25* Π*D
- Pitch angle: 12˚ ≤ α ≤ 14˚

where

D = the diameter of the Helix,
S = the spacing between each turn,
α = the Pitch angle which is the angle formed by the line tangent to the helix wire and a plane perpendicular to the helix axis.


The Helix input impedance (purely resistive) can be approximate by:
Z_helix (ohms) = 140*[(Π*D) / λ]
 

    H

    hyperbola

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Hi,
pl see the foll attachment..
Well ur application needs miniaturuzation...U can also try by creatin defects in the ground plane say dumbell or spiral shaped ...these increase the electrical leenth..so to get the original electrical length u need to reduce the size and there are formulae for all that..U c defects increase the slow wave effect..
 

    H

    hyperbola

    Points: 2
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Thanks. I have one more constraint however.My antenna has to be integrated on a pcb along with the tranceiver chip.The ground plane has to be one of the layers of the pcb,i guess.Will it be possible to make the pcb as small as possible?.Are there any good software for modeling the helix
 

Can the ground plane be the same as the pcb ground....?
 

Kindly help me as to how to route the pcb containing the helical antenna.The transceiver chip has multiple pins for analog and digital as well as separate pins for avdd and dvdd
 

Hello,

How ground clearance should we give for the via and lines in the RF pcb.Is there any standard design procedure.Hoping for a reply

rgds
 

As a rule of thumb the distance between vias shall me smaller than λ/10, and the clearance between microstrip lines and the external ground shall be greater than TL_width*1.5
 

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