How can i increase the band width of microstrip antenna?

[ehsan_ullah]

Hi everyone
I am designing a microstrip patch antenna (in HFSS). the return loss is good but its bandwdith is very small about 30MHz but i want to increase it to 200MHz and gain is about -4dB.
How can i increase bandwidth and gain..?

There is limitation on subistrate high and Er ( both must be kept constant to h=1.6mm and Er=4.7). and i can't change them..

 

[userdce]

parasitic patches may help

 

[WimRFP]

Hello,

Having 30 MHz bandwidth from a patch and wishing 200 MHz may not be feasible without sacrificing radiation efficiency or increasing the height above the ground plane.

Try to get the book: Compact and Broadband Microstrip Antennas by Kin-lu Wong.

By using a second or even two additional resonating structures, you can increase the BW with about factor 3, but this will not bring you close to 200 MHz. All designs that use multiple resonances in the patch itself of other structures increase the design complexity significantly.

The parasitic patch (as suggested by userdce) does really help, but increases the total height, unless you use patches adjacent to the main radiating patch

The problem in the gain can be caused by heat losses in the dielectric. The losses can be derived from the radiation efficiency and/or directivity. When the directivity is (for example) +2 dBi, you have good match and the gain is (for example) -2 dBi, you only radiate 40% of the electrical input power.

When you increase the conductivity of the conductors, you may only see a very small increase in radiation efficiency. This shows that in such a case dielectric losses are dominant. To increase gain, you have to increase the height and/or use better substrate material.

Note that when you use better substrate material (without increasing the heigth, you will get less useful bandwidth.

 

[vivek bauskar]

how to decrease vswr in dual band microstrip antenna?
give me any dual band antenna in hfss..

 

[WimRFP]

Hello,

As mentioned before, use a second (radiating or non-radiating) resonator, it gives you an increase of BW of factor 2.4 (VSWR=2). As wide bandwidth with patch is still hot, you can find lots of info on the Web.

doubling the height above ground will give about factor 2 increase of BW. When you use a better dielectric (so less loss), your useful bandwidth will decrease.

Best is to study why a patch close to a ground plane has narrow bandwidth. If the radiaton pattern allows, you may use a quarter wave patch (shorted to ground at one end). This gives some design flexibility.

I don't have an example for you that meets what you want.