[Discuss-gnuradio] GMSK modulator for higher modulation index
From:
wayne roberts
Subject:
[Discuss-gnuradio] GMSK modulator for higher modulation index
Date:
Wed, 4 Apr 2012 10:42:30 -0700
To support GFSK modulations, a higher modulation index needs to be used.
MSK is defined as a fixed modulation index of 0.25. However, GFSK is used in many simple ISM (unlicensed) systems, where the modulation index can vary from 0.5 to 2.0 typically. So, I would ask how the existing digital FM modulator blocks (such as GMSK mod) could be used in such case as (G)FSK. This is used in low-cost low-power simple systems, which are not as spectrally efficient.
I have also noticed in gnuradio-companion, under Digital Modulators: "GMSK Mod" which uses file gr-digital/python/gmsk.py, and "GMSK Modulator" which uses file gr-digital/lib/digital_gmskmod_bc, which just calls digital_cpmmod_bc.cc