Electrically small antennas for 433 MHz

[ojniemin]

Could anyone give me a hint on electrically small antennas for 433 MHz? The antenna shouldn't be larger than about 30mm in diameter and it will be placed close to a ground plane (1mm). I know that the antenna performance will be extremely poor but maybe some solutions are better than the others. Loading will be needed in order to get some bandwidth.

Thanks in advance!

 

[fil]

is it transmit or receive?
with receive only possibly the best way would be to use the antenna as a voltage field probe and convert from high impedance to low impedance with an amplifier and balun
if it is t/r then this would work on the receive side with another matching network for the transmitting side

 

[Bluebell]

I've done something like this before.The antenna is about 30mm in height with a reasonable gain. The idea is to attach a simple matching network to the antenna, that's all.

 

[jbartos]

Suggestion: Visit

http://www.awirelessworld.ch/data/radio/bim2.pdf

etc. for more info

 

[Bluebell]

Hi jbartos, I've built a helix before simliar to one in your article, but the gain is only -20dBi. Care to give your comments?

 

[jbartos]

Suggestion: Have you try another ones for higher gain? See the link for:
Antenna requirements
Three types of integral antenna are recommended and approved for use with the module:
A) Helical Wire coil, connected directly to pin 2, open circuit at other end. This antenna is very
efficient given it’s small size (20mm x 4mm dia.). The helical is a high Q antenna, trim
the wire length or expand the coil for optimum results. The helical de-tunes badly with
proximity to other conductive objects.
B) Loop A loop of PCB track tuned by a fixed or variable capacitor to ground at the 'hot' end and
fed from pin 2 at a point 20% from the ground end. Loops have high immunity to
proximity de-tuning.
C) Whip This is a wire, rod ,PCB track or combination connected directly to pin 2 of the module.
Optimum total length is 16cm (1/4 wave @ 433MHz). Keep the open circuit (hot) end
well away from metal components to prevent serious de-tuning. Whips are ground plane
sensitive and will benefit from internal 1/4 wave earthed radial(s) if the product is small
and plastic cased

A B C
helical loop whip
Ultimate performance ** * ***
Easy of design set-up ** * ***
Size *** ** *
Immunity proximity effects ** *** *
Range open ground to similar antenna 200m

 

[wademcnary]

I'm also making a handheld 433 MHz product and want to use a coil antenna on the receiver. I've seen 2 configurations and want to know if somebody can advise me on what difference in performance to expect. The antenna sticks out from the product.

Config. 1: 0.5mm wire, 20mm long X 4.2mm diameter, 24 turns.
Config. 2: 1mm wire, 30mm long X 7mm diameter, 17 turns.

 

[jbartos]

Suggestion: Visit

http://www.radiometrix.co.uk/dsheets/bim2.pdf

and search for helical antenna

http://www.geocities.com/euro446/tech.html

etc. for more info

 

[LMSolo]

lockheed Martin in palmdale california has been doing alot of research in electrically small antenas. contact Peter Von Burke @ 661-572-2359 or email him @ peter.r.von.burke@lmco.com