microstrip antena

hey!
i'm looking for microstrip patch antena for cellol :? ar at the rang between 800-950mhz with at list 10% BW.
i need to built it with substrate eith high EPSr the EPSr around 90-120.
is it possible? how?

\epsilon_r about 90-120? What kind of material is this, stone?

Hi dghd,

I think you want to use a substrate with such a high er because of the size of your patch-antenna. Such a substrate could be a ceramic material.
The disadvantage is the antenna gain will be very low when you use a high er. This is because of the smaller overall size of the antenna.
The same thing happens with the bandwidth: a patchantenna itself has a very limited bandwidth. If you additionally use a high er, the bandwidth will further go down. I think you can reach only some MHz or less than 1%...
Perhaps it would be a better idea using a dipole antenna, which can also bu built in planar technology.

Bye

I think antenna difficult if you want 10% bandwidth. Even if you manage to combine some higher modes to obtain this bandwidth your antenna will have a very low efficiency at such high epsr. RF energy gets trapped inside ceramic and very little energy is radiated. Usually ceramic of high dielectric constant not widely used but only in special circumstances e.g. GPS antenna.

Element7k

with a resistor- and superstrate-loaded antenna, an 6.52 percent impendence bandwidth (10-db return loss) is reported,
it's gain is as large as a conventional antenna

Can you provide a link or a paper for reference please?

ELment7k

If the dielectric constant increase, you have to mind the weight of your patch antenna. The Impedance bandwidth can be increased with a reactive loading such as chip resistor,post, slots (I work on slotted patch antennas). You have to consider also eventual radiation pattern asimmetries.
Are you working in Linear Plarization aren't you?

Hope it can help you.
Regards
Lupin

I Think the effiecicy is the most dificult thing for you!

It depends on what Gain value you need...
Are you also involved in slotted patch antennas?

Regards
Lupin

Actually there are easy-to-make microstrip antennas with bandwidths up to 30%-40%. For example cut in a U-Slot.

You are right, a standard patch has less than 2% bandwidth.

You want to use a small epsilon-r as possible to keep the radiation efficiency up. You especially increase the Q of your antenna with a large epsilon. The result would be small bandwidth and minimal radiation.

For the broadband patches just search I-EEE Antennas&Pr0pagation for "u-slot"

Hi RF people,
I've to design a planar antenna whose Impedance Bandwidth is from 6 to 18 GHz...Linear polarization.. any ideas?

Thanks in advance
Lupin

hi,
a vivaldi antenna is what you are looking for!

What kind of a match are you looking for over your band? I haven't had great luck with the Vivaldi antenna for being well matched over a wide band, kind of cyclical. Could be I haven't fooled with it enough. Does the antenna have to be thin due to mounting or is thin better due to volume restrictions? If you can use both sides of a substrait for rad elements you might take a look at a planer Log.

H3O

The matching threshold is -10 dB from 6 to 18 GHz, dual linear polarization. The antenna must be thin due to volume restrictions.. probably I'll have to use it as the element radiator for an array configuration.
What do you think?

Regards
Lupin