pcb mounted aerials

[zizka]

I'm looking for a pcb mounted (ceramic patch or similar) aerial for the 433MHz ism band.

Ideally I'm wanting a part that can be mounted on a groundplane.


Any ideas ?

[PaulL]

Assuming you have a 50 ohm line on your PCB why not just stop the ground plain (on both sides of course) and continue the center line to form a 1/4 wave? Old people like me would call that a Marconi antenna.

[c4_esp_VR]

Hi Zizka:

I always want to know how make my own pcb antenna, but never found a good tutorial to how to make...

This is a good link that have 4 parts to make pcb antenna and examples.

http://www.rfdesignline.com/howto/lowpowerrf/197004535

PaulL if you could do a small tutorial that how make a Marconi antenna...would be a great tutorial

See you.

[zizka]

Thanks Pauli ...... not quite what I had in mind.

I should have stipulated "small pcb antenna" (1/4 wavelength at my 433MHz looks like about 16cm)

Cheers, anyhow.

[PaulL]

c4_esp_VR wanted a tutorial on Marconi 1/4 wave antennas, well I think a tutorial would be a bit over the top, but here is some more information.
Lets start with a dipole. A length of wire 1/2 wavelength long (that's 1/2 wavelength in the wire, a liitle shorter than in air). This resonates nicely at the required frequency. You can put your signal in or out anywhere along the wire, but the most common way is to cut it half way and to put a coaxial feed onto either side (i.e. braid on one wire and inner on another). conveniently the impedance is low, about the same as coaxial cables and the output of radio modules. (that's why the output impedance is as it is - historical).
You can even put in extra elements and end up with a yagi (like a T.V. aerial). The extra elements means that the dipole is bent around - but thats a bit complicated for here.
Now for the clever bit. If you have half of the dipole (1/4 wave), with the inner of the coaxial connected to one end you can then connect the braid to a flat metal sheet (a ground plane). At radio frequencies the sheet acts as a mirror, so to a radio signal it looks like a dipole. Well, the metal sheet should be infinite, and the less metal (or PCB groundplane) you have the lower the gain. Thats why for experimentation manufacturers recommend a specific length of wire attached to the antenna input (or output pin), the PCB forming a passable ground plane.
The gain is nothing special, but it is probably far better than something small and clever mounted on the PCB. However if you thinking highly portable you may not have a choice

Sorry if this a bit basic for most of you, but perhaps someone will find it useful.

Paul