MELP Communication, Modem and HF Radio

Communications-related options available for the real-time MELP algorithm include:

• Synchronous 2400 bps serial communication using either C54x or C54xx serial port; data transmitted in 8-bit word format, with/without framesync. Other rates include 1200 bps, 3200 bps, 4000 bps, 4800 bps, and 9600 bps.
• Sync bit detection, loss of sync detection and notification
• frame packing/unpacking
• automatic audio-side clock adjustment to allow continuous synchronization with 2400 bps serial clock; tolerance up to 3% clock differential; compatible with SigSD4 audio module

The above options are implemented in real-time C54xx C/asm code.

For more information about off-the-shelf modem-ready and HF radio MELP-related products, please send e-mail to: dspinfo (at) signalogic.com to obtain contact information for major defense subcontractors and suppliers for MELP + HF-Radio information.

HF radio modems tested in the lab include Rockwell-Collins MDM-3001 and Q9600. HF radios or modems used in the field include L-3 Linkabit Multiband

Signalogic performed pioneering work with Rockwell-Collins in 2002 to demonstrate MELPe-over-HF radio. Page 9 of this Rockwell Collins "HF Communications" presentation shows time domain speech data displayed in Hypersignal-Macro software. Below is a capture of page 9:

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