AMBE-2020™ Vocoder Chips


Digital Voice System's AMBE-2020™ Vocoder Chip is an extremely flexible, low cost, half-duplex, voice compression solution that is ideal for commercial, consumer, and military mobile radio communication applications. As a new addition to DVSI's family of high performance vocoder chips, the AMBE-4020™ Vocoder Chip boasts a built-in 16-bit ADC and 12-bit DAC in a small footprint design that makes it easy to integrate and requires minimal power.

Please Note:

The AMBE-2000™ is out of production and no longer available. Check out the AMBE-4020™ Full Duplex (FD) Vocoder Chip.


Digital Voice System’s AMBE-2020™ Vocoder Chip is an extremely flexible, high-performance voice compression solution that provides exceptional voice quality at rates as low as 2.0 kbps and toll-quality at 4.0 kbps. The AMBE-2020™ Vocoder Chip is a low cost, DSP-based voice codec for half-duplex real and non-real time voice compression applications.

The AMBE-2020™ Vocoder Chip implements DVSI’s patented and award winning AMBE® Voice Compression Algorithm. The field-proven success of this technology has resulted in its recognition as the standard for voice quality in communication systems around the globe. Satellite systems such as ACeS, AMSC/TMI, ICO, Inmarsat, Iridium,  Optus and Thuraya use this technology because of its superior voice quality at low bit rates.

DVSI has packaged this advanced vocoder technology onto a proprietary chip from the world’s leading DSP manufacturer. This single-chip solution achieves a level of performance and reliability typically associated only with customized ASICs but without the risks and high-development costs.

DVSI developed the AMBE-2020™ Vocoder Chip to offer the latest AMBE® Voice Compression Technology with no licensing fees, royalties or the engineering expense typically associated with custom DSP software implementation. With small quantity off-the-shelf availability, this DSP provides low-risk cost-effective voice compression.

The AMBE-2000™ Vocoder Chip supports bit rates from 2000 to 9600 bps, formed from the combination of compressed speech data and Forward Error Correction (FEC) data . The AMBE-2000™ can change speech and/or FEC rates within one frame for on-the-fly flexibility.


With variable-rate high-performance FEC built-in, the AMBE-2020™ Vocoder Chip provides exceptional robustness to background noise and bit errors. Offering block and convolution codes with up to four bits of soft-decision decoding, the AMBE-2020™ Vocoder Chip can achieve peak performance in degraded channel conditions that include significant bit errors. The Viterbi decoder offers rates as low as R=1/4 for intelligible speech at up to 20% BER. This level of performance can lead to the successful development and deployment of wireless communication systems in the most demanding environments.

The AMBE-2020™ Vocoder Chip also includes a number of advanced features such as automatic Voice/Silence detection (VAD), adaptive comfort noise generation, DTMF and North American call progress tone detection and signaling, 16 ms echo cancellation and low-power consumption.

The AMBE-2020™ Vocoder Chip is easily configured to transmit and receive digitized speech to and from most linear, a-law, or u-law A/D-D/A codecs through its serial interface. The digitized speech from the external A/D is converted into compressed digital data (encoded) by the AMBE-2020™ Vocoder Chip and output to the channel interface. The serial channel interface may use a processor, controller, modem or similar device to handle the transmission of the compressed voice data across a channel.

Block Diagram
Click for Enlarged Block Diagram

The AMBE-2020™ Vocoder Chip employs DVSI’s latest AMBE-2020™ voice coder technology providing toll-quality speech at rates as low as 4.0 kbps. Along with improved performance and enhancements such as convolutional FEC coding, an operational mode exists that provides a seamless migration path into systems already using DVSI’s AMBE-1000™ Vocoder Chip. The AMBE-2020™ Vocoder Chip offers the afford-ability, mobility and power efficiency required by virtually all personal communication devices.

The value of DVSI’s AMBE® Voice Compression Technology goes beyond low-bit-rate and voice quality. It has been thoroughly evaluated and tested by international manufacturers under various conditions using a variety of languages. This assures the user is getting the best vocoder available and makes the DVSI vocoder the logical choice without the need for additional comparison tests. Plus the fact, that DVSI’s Voice Compression technology has been implemented worldwide for more than ten years delivers the added security of a field proven technology that can play a key role in making any communication system an overall success.

As another member DVSI's family of advanced voice compression products, the AMBE-4020™ has inter-operable modes that provide a seamless migration path from systems already using DVSI's AMBE-3000™ , AMBE-2020™ and AMBE-1000™ Vocoder Chips.

AMBE-2020™ Chip Rates YES
AMBE-3000™ Chip Rates YES*
APCO Project 25 Half Rate NO
APCO Project 25 Full Rate NO
TerreStar NO
MexSat NO
GlobalStar NO

(* NOTE: The following AMBE-3000™ built-in rates are not supported: 33-37, 47, and 51-55. As a result, MotoTRBO, DMR, dPMR, NXDN and APCO Project 25 Half Rate are not supported as indicted above.)


  • AMBE+™ Vocoder - Toll-Quality at 4.0 kbps User selectable bit rate (2.0 kbps - 9.6 kbps)
  • Integrated convolutional and block code Forward Error Correction (FEC)
  • Viterbi Decoder (1/4 < rate < 1) with up to 4 bits of soft-decision decoding
  • High-performance Voice Activity Detection (VAD) with adaptive Comfort Noise Insertion (CNI)
  • Low Delay
  • Echo Cancellation


  • Low Cost
    - Ideal for wireless products
    - No licensing fees or royalties
    - Low power consumption (65 mw @ 3.3v)
    - Single IC solution (100 pin TQFP)
  • Simple Integration
    - Flexible A/D-D/A interface that works with many low cost codecs
    - User selectable speech and FEC rates for flexibility in system design
    - Serial channel interface with independent encoder and decoder rates
    - Interoperable with DVSI's AMBE-1000™ Vocoder Chip

High Quality Performance

  • Superior voice quality, DVSI's latest generation half duplex AMBE+2™ Vocoder Technology
  • Maximizes channel bandwidth efficiency supports data-rates from 2.0 kbps to 9.6 kbps
  • User selectable forward error correction rates - 50 bps to 7.2 kbps
  • Excellent performance at low data rates and harsh environments
  • Robustness to acoustic background noise and channel bit errors
  • Advanced features like Noise Suppression, Improved Error Mitigation, and Soft Decision FEC Decoding
  • Supports a-law and u-law companding via I2S interface
  • DTMF detection and regeneration with North American call progress tones

Design Flexibility/Low Cost Integration

  • Integrated 16-bit ADC / 12-bit DAC and vocoder in one chip
  • Works with most low-cost A/D-D/A codecs
  • Input Interfaces available internal ADC or digital mic or I2S
  • Output interfaces available: internal DAC or I2S
  • Interface for low-cost digital microphone
  • Push-to-talk Half-duplex Operation
  • Very low power consumption - Ideal for portable mobile devices
  • Small compact footprint design
  • 80 pin 12mm x 12mm LQFP or 121 ball 8mm x 8mm BGA package available
  • No licensing fees or royalties
  • Off-the-shelf availability for quick delivery