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martlet_3:radio:antennas

Martlet 3 Radio Antennas

Thought/Research Dump

We need

  • A low profile antenna that doesn't get in the airflow
  • A radiation pattern that ideally has telem going to the ground and GPS to the horizon and up
  • Resonant on about 868MHz for telem and 1.6GHz for GPS

Problems include

  • Rocket bodies all conductive so can't easily put an antenna inside
  • Nosecones an option on boosters only, and even then they separate so not ideal

Some easily discarded designs/ideas

  • Dipole on the outside. Wouldn't really work over a ground plane/metal
  • Dipole or bazooka dipole inside. Doesn't work inside conductive tube

Possible options

  • Slot (maybe with cavity)
  • Folded F
  • Patch array
  • Cylindrical patch antennas

Probably the cylindrical patch is the best option. Some details…

  • Dielectric permittivity sets the size of the patch, so higher would be better
  • But higher dielectrics give lower bandwidths and efficiencies
  • Also the dielectric gap has a small effect on the size, and a big effect on the bandwidth and efficiency
  • We'd like a very small gap but that would give a very small bandwidth
  • Radiation pattern is broadside from the rocket which is not ideal
  • Various options for feeding - inset feed with a probe might match to 50R but is hard to do with multiple feedpoints. End feeding gives 200R impedance but we can use a microstrip feed network to match and distribute. This seems the most common approach
martlet_3/radio/antennas.txt · Last modified: 2016/05/19 21:55 by ag611