What is the SMALLEST antenna can be used

[radioman]

Very small antenna

Hi Dderijken,

About your small antenna, you can go down to 1/10 lambda. That's what they use in social alarming etc.
I've made a very small antenna. It works on 868 MHz (ISM band) and is only 8x13 mm in size. It is a patch antenna on a multi layer PCB. The complete antenna is first simulated with HFSS. The measured reflection coefficient is about -20 dB. The bandwith is about 15 MHz. The impedance is 50 Ohm.
With a transceiver of 1 mW and a basestation with the same transceiver and a rubber duck antenna, you can cover a distance of about 25 meter.
So how small can you go ? Very small !

 

[yingyang]

small antenna

Hi,
Good reply given by so many guru.
Many have forgotten to use capacitive or inductive loading to shorten the antenna. The length need not be lambda/4. It can be very small if loading is adopted. In addition, one can also use the concept of coupling (whether aperture or direct coupling) or the cavity type antenna.

Hope this clear some doubt.....

 

[yingyang]

small antenna


Hi,
I think the question should be rephrased as how small can a ground plane be rather than how small can the antenna be.

A ground plane need not necessary be horizontal; It can wrap around in certain plane and yet provide good efficiency or gain. The only drawback is the cross-polarisation.

 

[ppAntenna]

I think use high dielectric can reduce the size of the patch antenna but the impedance bandwidth may be decreased.
Moreover size reduce gain also decrease.
If gain and the bandwidth is not the mainly concern in your design.
You can try adding shorting pins the reduce the patch antenna size.

 

[mwpro]

Is it correct to think that any thing can be an antenna except that the efficiency will be extremely poor. But for short range communication, it wouldn't be a problem.

 

[zorro]

Efficiency is the point. Think in the widely used receiving antennas for MW AM broadcasting: the wavelengths are 200 - 500 meters but the sizes are centimeters (ferrite loops) or decimeters (wires = capacitive antennas). Efficiency is sacrified in the receiving side for obvious reasons.
On the oter hand, at the transmitter side (where efficiency is important, not only power handling) the antennas are typically monopoles of 1/4 wavelength (sometimes shortened with capacitive heats, but the size is in the same order of magnitude).

Z

 

[ovni_cba]

disminucion del tamaño de antena

hello, se puede disminuir el tamaño de la antenna patch, aumentando el Er.
ver planilla excel.

ovni_cba

 

[yingyang]

smallest antenna

You may like to cut slot on it. 8) 8) 8)

 

[yingyang]

antenna

I forgot to mention, you can add resistor too?????