Intressant beslut att använda en s.k. "Software Defined Transponder" på P3E
AMSAT-DL’s Board of Directors has made the decision to fly the Software Defined Transponder (SDX) on their Phase 3-Express (P3E) spacecraft. SDX features AMSAT-NA’s implementation of the Software Defined Radio based on the Quadrature Sampling Detector. This decision was made at a recent BOD meeting in Marburg, Germany. SDX will utilize space that was originally planned for the Rudak Modem Module (RMU). SDX will allow Karl Meinzer’s (DJ4ZC) HELAPS (High Efficiency Linear Amplification by Parametric Synthesis) ideas from his doctoral thesis to be fully implemented for the first time. With the use of the SDX processor, significantly improved linearity and efficiency in the U/V transponder can be achieved compared to the all analog implementations of HELAPS in previous Phase 3 satellites.
Placement of SDX on P3E opens an opportunity to provide an early demonstration of SDX’s potential in space, including placement in an orbit that will provide flight time through the radiation belts. This "Phase 1 test" of SDX will in turn provide flight proof of concept that will benefit the later placement of SDX on AMSAT-NA’s Eagle-class spacecrafts. It also provides a test platform for evaluation of SDX’s weak signal processing that could prove valuable for an eventual Phase 5-A deep space mission that AMSAT-DL is evaluating. Along with improved
receiver performance, SDX offers the ability to program configuration changes while in orbit and the integration of uplink and downlink bands via digital connections.
Howard Long, G6LVB of AMSAT-UK, will lead the development of SDX software for both P3E and Eagle. AMSAT-NA’s Bob McGwier, N4HY and Frank Brickle, AB2KT, will conduct the integration of SDX with P3-E’s HELAPS transmitters. AMSAT-NA’s Lyle Johnson KK7P, and Chuck Green, N0ADI, who have served on a number of AMSAT satellite projects, will build the flight hardware.
AMSAT-DL President Peter Guelzow, DB2OS informed Bob McGwier, N4HY AMSAT-NA’s VP-Engineering of the Board’s decision on November 28. "This is outstanding news" notes Rick Hambly, W2GPS President of AMSAT-NA. "The opportunity to fly SDX on P3-Express will provide an early opportunity to demonstrate the potential of SDX in orbit and gives AMSAT-NA the benefit of in-orbit testing before placement on the Eagle-class satellites."
At a December meeting in Marburg, Howard, G6LVB demonstrated the functional SDX software on the target DSP processor along with a fully functional STELLA (Satellite Transponder with Equalizing Level Limiting Adapter). STELLA is designed to handle the situation where a User transmits too much power to the satellite adversely impacting the overall transponder AGC levels and thus reducing the output levels of other users on the transponder. STELLA has the ability to dynamically notch an excessive input signal to bring it into compliance with an appropriate output level versus the beacon on that d. Hambly added, "This announcement and the follow on work reinforces the close cooperation between AMSAT-NA, AMSAT-DL and AMSAT-UK as we develop the next generation of high earth orbit amateur radio satellites."
Källa: ANS 359 (2005)