CubeSat Antenna Tuning

October 20, 2014

Half-Band (San Luis Obispo, CA) engineer Alex Diaz (BSEE ’09) funded through Ecliptic Enterprises (Pasadena, CA) tuned the CubeSat system antenna for optimal matching in Cal Poly’s Antenna Anechoic Chamber, which simulates the actual (free space) operating environment. Previous matching characteristics indicated a ‑5dB to ‑6dB magnitude input reflection coefficient (25.1% to 31.6% reflected power relative to incident) at the 437MHz operating frequency. Through antenna impedance measurements and Smith Chart matching network analysis and design, the network was modified to yield an improved reflection coefficient of -22dB (0.63% reflected power). Antenna length adjustments and resultant impedance effects were characterized on the Anechoic Chamber Lab’s HP 8720C vector network analyzer. Final -10dB match bandwidth is 17.2%; 418MHz to 493MHz on a 437MHz center frequency. Typical monopole antenna bandwidth is less than 5%.

The CubeSat test setup inside the Anechoic Chamber is shown above. CubeSat is scheduled to launch on SpaceX Falcon Heavy in April 2016 and will undergo environmental testing next week at Cal Poly. Antenna match optimization will improve telemetry and radio communications from CubeSat to ground stations.