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Impedance matching in low frequency range

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sweetchoto

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Hi,
I have designed an antipodal Vivaldi antenna using HFSS which is very compact in size(57x52mm).The antenna have perfect impedance match(s11<-10dB) in the range of 3.3-11 GHz. I want to increase the impedance match on the low frequency edge,e.g i want the impedance match from 100MHz onwards. Any good suggestions to achieve impedance matching for low frequencies??? Due to compact size of antenna i can not use any impedance matching network here.

Any suggestions would be helpful.
 

With a 50 mm antenna at a few 100 MHz, the radiation resistance will be very low according to fundamental antenna relations. It can be possibly impedance matched for a single frequency, resulting in a very high Q respectively a very low bandwidth.
 

Even if your antenna type is very wide bandwidth (almost two octaves), cannot change to go down in frequency 5 octaves. Vivaldi antenna is wideband due to its exponential shape, and generally is not working well for frequencies below 3GHz.
 

@Vfone.....Yes i agree with you.But i have seen some of the papers in which they have got Impedance match Even Below 3GHz and i just wonder how they have go match at low frequency range.
 

As was mentioned above, for this kind of antenna impedance matching at lower frequencies doesn't make the antenna working properly at those frequencies.
Theoretically any piece of wire or metal could be impedance matched for any frequency, but this doesn't mean it will radiate energy.
 

i just wonder how they have go match at low frequency range
Click to expand...
The papers should tell. Perhaps they use a larger antenna?

I completely agree with vfone, that you can't expect good performance for an electrical small antenna. But if you can achieve impedance matching for a single frequency, then the bandwidth will be very low. You won't achieve wideband and efficient operation simultaneously.
 

vfone said:
As was mentioned above, for this kind of antenna impedance matching at lower frequencies doesn't make the antenna working properly at those frequencies.
Theoretically any piece of wire or metal could be impedance matched for any frequency, but this doesn't mean it will radiate energy.
Click to expand...

IT Really helps in clearing things up. Thx for the help!!
 

Look at ground penetrating radar antenna papers. They have wide bandwidth, and can go down to a few hundred MHz. Unfortunately, they are large.
 

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