CML Launches Low Cost, Low Bit-Rate RALCWI Vocoder IC

8th August 2007

ES Admin

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CML Microcircuits today announced the introduction of a new RALCWI (Robust Advanced Low Complexity Waveform Interpolation) vocoder IC. The product is the result of a co-operation between CML Microcircuits and SPIRIT DSP. The new CML IC is named as the CMX618, which CML will market to worldwide communication markets based upon SPIRIT’s proprietary Low Bit-Rate Vocoder technology. The co-operation combines CML’s 39-year history of developing mixed-signal semiconductors for professional and leisure communication applications, with SPIRIT’s extensive experience in embedded voice products.

The CMX618 is a flexible, half-duplex, highly integrated RALCWI vocoder IC suited to both wireless and wireline voice applications such as voice scramblers, alarm systems, military field applications and digital professional/leisure two-way radios (DMR/dPMR) to name but a few examples.

RALCWI technology uses proprietary signal decomposition and parameter encoding methods, ensuring high speech quality at high compression rates. The CMX618 offers near toll quality voice performance at very low bit rates, with independent MOS scores indicating that the CMX618 generates sound quality comparable with a standard codec running at bit rates above 4000bps.

The CMX618 includes an integrated voice audio codec, offering a complete analogue voice to low bit rate vocoded data function. There are 3 programmable vocoding rates: 2050bps, 2400bps or 2700bps and when combined with the embedded FEC, provides an overall bit rate of 3600bps. Frame length is selectable from 20, 40, or 60 ms without FEC, 60 or 80 ms can be selected with FEC protected frames. The selectable integral Viterbi decoder can use soft-decision metrics to improve its decoding ability. The FEC can also be used separately, so that data can be decoded/error-corrected, then re-encoded and forwarded on. This feature is particularly useful in voice repeaters, providing optimal voice performance and maximum range.

CML also offers designers the CMX608, a vocoder option without the integrated audio codec. This enables the use of an external audio codec solution. Both the CMX618 and CMX608 are free from any licence and royalty costs, fully meeting the requirements of high performance low bit rate digital voice applications. The CMX618 and CMX608 are available in small low power 48-pin VQFN and LQFP packages. An evaluation kit is available (EV6180), facilitating quick and easy evaluation. Connections are provided for audio input and output, power supply and a serial bus (C-BUS) header for connection to a host microcontroller.