The aperture of horn antennas is usually large. This creates problems of requiring more distance and room for far field measurements. Is there a way, we can use patch antennas or other miniaturized antennas for measurements instead.
I think the most rational answer to your question is to define the specifications of your microwave source suitable for testing.
For example you have to specify:
The frequency band,
The beam width such that to get specific spatial variations of the radiation intensity
The radiation intensity range
In fact you can specify the horn pattern at first
and then you try to mimic it by a pattern of antenna batches.
Best wishes.
Some of the reasons horn antennas are used:
1. Horn antennas are wideband. A patch antenna has a narrow bandwidth so you would need a different patch for different frequencies, this can lead to long and tedious measurements.
2. Horn antennas are more robust and once they have their gain standardised they can be used for a long time and many tests. And again since they are wideband, one horn can be used for a large bandwidth. Imagine how many patch antennas you would need standardised for gain to achieve the same functionality as a horn!
3. Horns have a well defined aperture and are easier to setup during measurements than most patch antennas.
@mohamed K. Emara
Thankyou for your answer. No doubt horn antennas has its advantages, but in some cases, its large aperture becomes an issue. so thats why i was wondering if one could use a wideband patch or any other smaller antenna instead.
If you have a patch (or any antenna) operating at the frequency of interest and its gain is characterized you can definitely use it instead of a horn for measurements.
Yo can use a small horn antenna instead of a patch. It won't be much bigger and will have a wide bandwidth.
Usually you need a large antenna so that it doesn't have a wide beamwidth, because reflections off things you don't want to measure are a potentially big problem, and are one of the main thing to try to avoid. They will probably have their polarization changed, they will come from the wrong direction, and in transmission measurements they may go round your sample, and they add or subtract to the measurement you want.
Almost every small antenna (in wavelengths) has a wide beamwidth, and those that don't (superdirective) are usually not practical to use.
@Malcolm White
Thankyou for this providing this insight regarding beamwidth.
Yes, you can use patch antenna in combination with metamaterials cells in the substrate and around path antenna to expand her bandwidth and increase her gain.
Conference Paper Metamaterials on antenna solutions
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