By suspending the patch on air

By shorting

By tuning antenna dimensions

I have the same ideas as Muhammad Khan. In addition, if you already chose the substrate with fixed permittivity and tangent delta, you can try to change the height of the ground plan behind the radiation patch.

For example, i applied this technique in antenna design for UWB by keeping the height of ground plan just cover the feeding line (from the SMA connection point to a bit lower than the radiation patch.

You can improve the BW of the antenna by cutting a slot in the patch You also for babau r vishvakarma to see lots of papers on the topic

You can improve the BW of the antenna by cutting a slot in the patch You also SEARCH for babau r vishvakarma to see lots of papers on the topic

Just now

use air as a substrate or RT Duriod substrate instead of normal FR4 SUBSTRATE.

or use stacked patches..

Stacking one or two patches can improve bandwidth of the antenna.

substrate is rogers with permitivity 2.2,i have another problem and that is i want to have another band in 3.5 GHZ, i have could to catch it but my essential problem is BW in these two bands,and i want my antenna to have wearable application,can anyone give me some good idea?

You can design multi resonant antenna which can covet several usable freqiencies like GPS,WLAN,Wi max etc but you have to wotk hard.

Is it possible with this substrate?how can i improve bw?

You can improve the BW of the patch on any substrate using several techniques like cutting slots on the patch, stacking one or two ptches,parasitic patches.

you can change the feeding method from coaxial probe to CPW feeding

Coaxial or CPW feeding is immaterial . The feed and the patch at the feed point must match for the required band that ensures the BW.

The bandwidth which is mentioned is of little use thus you have follow some good books of increasing bandwidth.

Increase height between patch and ground plane.

Widen of radiating edges of patch

U can enhance the bandwidth by using line feed in normal fr4 substrate.

try to use PBG structures in the ground plane.

In case of PBG structure you need big ground above it

You can improve the BW of the antenna by using:

1) Fractal patch

2) superconductor patch

3) multilayer

4) thick substrates

A simple way of improving the bandwidth is to increase your substerate height, however that will generate surface wave effect and deteriorate antenna performance with respect to gain and efficiency (even cross polarization increases). So for a nominal improvement in bandwidth add 2 or 3 parasitic resonator (patch) near to your main radiating patch On same layer) such that their resonant mode is very near to the main radiating patch. The effective dimensions of these parasitic elements could be kept for 2.3 GHz or 2.5 GHz depending on your higher and lower frequency requirements.

I think the feed point of coax or MS line is not set well, so the Impedance bandwidth is low, pattern bandwidth must be bigger than 30 MHz. Some optimization to determine best feed point is required.

You might use

1) BALUN to change the matched impedance of antenna from 50 ohm to antenna structure natural impedance

2) @Anton Lukyanov : Increase height between patch and ground plane

3) @Ouarda Barkat : Fractal patch or multilayer or thick substrates

I Think,

You may use Defected Ground Structure (DGS), Parasitic (element) effect, Stacked/multi layer substrate, or Metamaterial to improve the bandwidth Issue. Thank you.

@ Raimi Dewan

I agree

Thank you =)

@ Raimi Dewan

I am applying DGSs in Microwave Circuits for performance enhancement.

@Chandra

Interesting. Wishing you all the best (^_^)~

One of the problems with microstrip antennas is low bandwidth. To find higher bandwidth, one way is to use finite or partial substrate.

microstrip patch antenna has 7 to 15 percent bandwidth. And antenna that works in 2.4 GHz, but its bandwidth is 30 MHz; WoW

all answers are good to improve bandwidth to near 2:1 frequency-band.

But the above question should be answered by the different ways to feed and match the microstrip patch antenna; if it solved, then the other ways to enhance bandwidth are good and acceptable.

Bandwidth can be increased in different ways, some of which are stated below:

Use thick substrate (surface wave should not generate) to design antenna at 2.4GHz.

Use multi-layered configuration (proximity-coupled or aperture-coupled).

Single-layered microstrip antenna with 2 or 3 thin rings surrounding the antenna may increase bandwidth due to parasitic effect.

Fundamentally, microstrip is sharp response over frequency, hence it is inherent nature. To improve bandwidth,

1) Create 'cuts' in side the patch uniformly

2) Create 'LPDA' using patches

3) Create patch in the form of self complementary

4) Use of mateamaterials

Increase the thickness, Using L-shaped probe, Parasitic elements, U-Shaped Slot in the patch radiator. You can read the paper or the book wrote by K. M. Luk from City University of Hong Kong.

Come with a specfiic question

Read Girsh Kumar and K P Ray " Broad Band Microstrip antenna" Book 

Before designing the Microstrip Antenna you should decide the application. For instance, you want to design a Microstrip Antenna for WLAN application that requires the frequency range from 2.40-2.48 GHz. It means for this application only 80 MHz bandwidth is sufficient.

   You can enhance the bandwidth by using line feed techniques in stead of coaxial probe. you can also increase the bw by stacking structure.

Any solution for increasing the band width of Microstrip antennas is not independent of its other aspects and characteristics. So, use of defected ground structures or adding additional rings in the proximity of main patch may be avail, however they have inevitable effect on radiated pattern. Accordingly the best solution is strongly depends on your application.

Patch antenna bandwidth is directly proportional to the substrate height but increasing substrate height will reduce gain and further surface waves also increases. So you can choose increasing substrate height at the cost of Gain.

Some modification on the patch. If you increase substrate height the bandwidth would increase but H shape patch or cutting slots in it would also help.

Cuts and slots introduce second resonance and if these resonances become in on frequency band, the bandwidth increase.

In thin substrates these cuts wouldn't help because it is hard to bring these resonances to one band

Dear Nooshin Valizade

         First of all you should decide the application for which you want to design the microstrip antenna such WLAN (2.40GHz-2.48 GHz), WiMAX (2.495GHz-2.695GHz).

        Bandwidth of Microstrip Antenna can be increased by introducing different slots such as U slot or H slot within the patch. Also by using line feed you can also enhance the bandwidth.