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martlet_3:radio:antennas [2016/05/19 21:55] (current)
ag611 created
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 +====== 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 ยท Last modified: 2016/05/19 21:55 by ag611