Transmission Purity Software: Pre-distortion Software

Joe WD5Y

In reading articles regarding SDR I came across discussions about TX IMD and pre-distortion software that would provide improvements with transmission purity in mind. I am not indicating there is any issues at all with the Flex 6000 series; I just read about a new feature within SDR. Could someone please explain what this is? It sounds very interesting. I would assume with the processing inside of the Flex 6000 and with it's horsepower that the response time to eliminate transmission distortion would be very fast. Thanks, Joe WD5Y

Keith - AE5XN

Joe, It's essentially measuring the transmitter's harmonics and then generating tones equal in magnitude and frequency to those harmonics, but at 180 degrees out-of-phase with the harmonics. The idea is to try to use DSP techniques to cancel out the transmitter's harmonics. That's the theory, anyway. In practice, there are other non-linearities and IMD products in a 100W 13.8V PA that would somewhat hamper complete cancellation, and may actually create other spurs. So, you'll get some improvement, but it won't be 100% cancellation by any means. Keith - AE5XN

Joe WD5Y

Thanks Keith for the explanation. I've been reading this with curiosity. It sounds interesting but like everything else for an action there is a reaction and it may or may not be a good one. Thanks and 73's Joe

Sergey R5AU

Hi Joe, thank you for nice topic. Keith, sure, no doubts, 100% compensation of the distortions impossible, but already exist exmaple with good theory realisation and i wonna to see it also in my best F6700. Can you look completely at: http://www.adat.ch/index_e.html , and strongly recommended read Measurement results (German only, but understandable)- http://www.adat.ch/pub/Parameter_Verifikation_090305.pdf i wonna to adress this question to FRS, as really existing feature.