Electronic – Possibility of an extremely directional antenna

antennapcb-antennaRFwireless

I'm fairly new to RF technology, but a direction-finding application has come up where a highly directional antenna can offer a convenient solution, so I started searching for such antennas.

Most, like Yagi antennas, that can be purchased seem to have gain patterns that are not very focused, with half-power beamwidths of no less than 30 degrees, often much greater.

Is it possible to design PCB antennas (or alternatively, purchase pre-made antennas) with a very narrow/focused radiation pattern — Ideally, I'm looking for a small (size < 10 cm) antenna with a half-power beamwidth under 10 degrees? Assume any transmission frequency between, e.g., 433 Mhz up to 10 GHz is acceptable (because the application has some leeway in this).

What keywords should I research for this, or are such antennas impossible due to scientific limitations?

For example, Wikipedia contains this image within a radiation-pattern article, but I haven't yet been able to find an antenna with such favorable pattern:

enter image description here

Best Answer

Your requirements will never be met.

A dish antenna is the best for providing focus and if you looked at voyager II, it used a 3.7 metre dish at about 3 GHz. This would give a 3dB half-beam-width of about 0.91 degrees.

I'm using the example of Voyager II because they would not ship something to the planets that had not been thought about (o-rings excluded from this statement).

At 1 GHz this half beam angle increases to 2.74 degrees

At 1 GHz and a 1m dish this increases to 10.2 degrees

See this calculator to check. To help you get further ideas about this follow these rules: -

  • If you double the frequency, the gain of an antenna will quadruple.
  • If you double the frequency, the beam-width of an antenna will halve.
  • If you double the antenna diameter (keeping the frequency the same), the gain of the antenna will quadruple.
  • If you double the antenna diameter (keeping the frequency the same), the beam-width of an antenna will halve.