OKI Semiconductor introduces EchoPath series of echo cancellers for emerging communications applications; Application-specific echo cancellers replace general-purpose DSPs reducing cost and power consumption and increasing ease of implementation.
EchoPath products are designed to replace the use of general-purpose digital signal processors (DSPs) as echo cancelling devices by reducing cost, power consumption, increasing integration and ease of implementation.
The MSM7718, the first product of the new EchoPath family, is a unique device that offers two modes of operation. In the first mode, the MSM7718 combines an ADPCM CODEC with a 27 ms echo cancellation function integrated into a single chip. The second mode of operation offers a single 55 ms echo cancellation function and a transcoder (digital PCM to ADPCM conversion) capability in a single-chip solution.
The MSM7718 was initially designed for infrastructure applications that require analog-to-digital conversion coupled with a line echo cancellation feature, such as basestations for wireless local loop (WLL), remote exchanges and trunk cancellers. This device can also be used for handset applications like automobile accessory kits.
The second product in the EchoPath family is the MSM7603, an EC that provides 59 ms of cancellation time and is designed for use in "hands-free" applications such as cellular phones, car accessory kits, conference room telephone equipment, and the integration of voice capabilities in computers. In the past, only cost-prohibitive, high-performance general-purpose DSPs came close to offering the significant delay times required for such applications.
With growing concern over the safety of cellular phone use while driving, many countries require the use of hands-free technology. Several states within the United States are considering similar legislation. Such moves would cause the market for these devices to explode.
Due to its unique design, the MSM7603 can reduce EC costs by 40 percent and power consumption by 50 percent. The "howling" phenomenon, caused by background noise inherent in automobiles, is detected and minimized by the MSM7603.
As near-end echo times widen due to more complex signal technologies like CDMA, basestations are turning to longer delay-path products like cascading echo cancellers. The MSM7602 is capable of cascade operation, where multiple EC circuits are run in series, producing cancellation times of up to 213 ms. The MSM7602 provides flexibility in operation over the full 3 - 5-volt range, simplifying component selection.
"There are a number of extremely hot technologies requiring echo cancellers that are just starting development," said Scott Gardner, communications marketing manager at Oki Semiconductor. "The EchoPath family of products will be invaluable to systems designers building devices for markets in which quality, cost, higher integration, low-power consumption and ease of implementation are all critically important."
EchoPath vs. DSPs
EchoPath products are the first practical hardware alternative to the use of expensive general-purpose DSPs for echo cancellation and offer significant benefits in terms of ease of implementation, power consumption, size and cost. First, in order for a general-purpose DSP to perform a specific function, it must be programmed, a process that can take several months to complete. EchoPath ECs are designed to carry out functions without programming prior to implementation.
Second, because general-purpose DSPs carry out designated functions through software, the processors must run very fast to perform a specific task in real time, which consumes a great deal of power. EchoPath ECs do not require the use of external software and can perform the same functions using less power. In addition, EchoPath products have a sleep mode, so they consume minimal power when not in use, unlike general-purpose DSPs. Finally, since general-purpose DSPs are designed for a variety of uses, they are larger and more expensive than Oki's application-specific devices.
How ECs Work
A typical hands-free kit, for example, incorporates a speaker, a microphone, an EC and a PCM CODEC. The data shift clock and the 8 KHz sync clock from the handset are connected directly to the hands-free kit. The acoustic echoes that are present when the voice signals from the speaker appear at the microphone are cancelled by a pseudo-echo signal generated inside the EC by calculating the impulse response of the echo path. The result is a clear, echo-free conversation between the hands-free user and the telephone user.
In basestations or infrastructure using WLL or PCS technologies, designers face the daunting task of eliminating far-end line echoes caused by path distortions, such as impedance mismatch and I2R loss. Selection of a digital technology by carriers can equate to several hundred millisecond deviations in delay.
Such variances require flexibility as provided in cascadable solutions from Oki.
Pricing and Availability
The MSM7718 is volume priced at $9, the MSM7603 is volume priced at $9.90 and the MSM7602 is volume priced at $5.55. All three devices are available immediately on a functional test bed using Oki's IC-SK evaluation board.
Oki continually develops new products targeting the entire voice or data path channel from CODECs to RF components. By developing synergistic communication devices, including ECs, RF mixers, low-noise amplifiers, SAW filters, PAs and voice recognition processors, Oki helps its customers with the lowest available cost structures and turnkey applications support in the industry.
Oki Semiconductor, founded in 1977, manufactures a broad line of advanced integrated circuits for use in computers, communications, EDP, automotive, and consumer products. A leader in CMOS memories, CODECs, ECs and ASICs, Oki's product lines also include voice recognition, speech synthesis, microcontrollers and advanced communications devices for wired, wireless and fiber optic applications. Oki is also a leader in packaging technology, offering sophisticated options to its customers. Headquartered in Sunnyvale, Calif., Oki has manufacturing facilities in Japan, Thailand and Portland, Ore. All Oki manufacturing facilities are ISO 9001-certified. Oki Semiconductor is a division of OKI America Inc., a subsidiary of Oki Electric Industry Co., Ltd. FAXBACK: 1 (800) OKI-6994 for the United States, and (609) 222-9716 for both Canada and Mexico. Oki's Web URL is: http://www.okisemi.com.
CONTACT: Oki Semiconductor
Lori Higa, 408/720-1900
Walt & Company Communications
Jenn Knudsen/Dean Rodgers, 408/496-0900
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|Date:||May 19, 1997|
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