Orlando, Fla. -- Akustica Inc. announced last week that Fujitsu's LifeBook Q2010--a notebook aimed at no-holds-barred "road warriors" like traveling executives--will include two AKU2000 single- chip microphones located on the display's bezel.
This design win indicates that high-end laptop computers are switching from analog to digital microphones, according to Akustica (Pittsburgh). At the same time, the company introduced a chip, the AKU2001, that permits multiple microphones to share a single interface wire.
Codec maker SigmaTel Inc. (Austin, Texas) simultaneously announced support for the AKU2001 microphones. The compatible codec will permit designers to multiplex multiple microphones on a single interface wire without using any other supporting circuitry.
"Fujitsu is just our first customer-adoption announcement, but we have many other design wins pending," said Davin Yuknis, Akustica's vice president of marketing. "We predict 25 percent penetration of the high-end notebook PC market by next year, and 50 percent penetration within two years."
Market research firm Yole Development (Lyon, France) puts the silicon microphone market last year at nearly 100 million units and predicts it will grow to 800 million units by 2010. Most of those, however, will be analog silicon chip microphones made for analog cell phones by Knowles Electronics LLC (Itasca, Ill.) and Sonion MEMS A/S (Roskilde, Denmark). In contrast, Akustica's silicon microphone has the analog-to-digital converter on the same chip, greatly simplifying integration into notebook PCs and other digital devices.
Beginning with MEMS
Akustica, Knowles and Sonion all use microelectromechanical systems (MEMS) techniques to fabricate an ultratiny microphone diaphragm, allowing them to produce a single-chip microphone. Akustica's approach is unique, however, because its diaphragm is fabricated on a standard CMOS wafer along with all supporting circuitry. After that, the diaphragm is freed to move in a step that etches away sacrificial material below and around it. Akustica's approach simplifies system designs by combining the diaphragm, the analog preamplifier and the A/D converter functions on the same CMOS chip. Thus it can be more easily integrated with such digital devices as PDAs, Bluetooth headsets and the increasing number of ports for voice-over-Internet Protocol (VoIP).
"Akustica is certainly attaching itself to an interesting market with the Fujitsu LifeBook," said Steve Ohr, research director of analog semiconductors at Gartner Dataquest. "The number of VoIP ports has a 24.1 percent compound annual growth rate, increasing from over 29.5 million ports in 2005 to 73.8 million in 2010. Revenue growth, in the same period, will go from $1.5 billion in 2005 to $3.5 billion in 2010, for a 20.3 percent compound annual growth rate."
Fujitsu, according to Akustica's Yuknis, chose the AKU2000 because it needed to improve the quality of the signal it was getting from the voice-input port to its notebook PC for VoIP as well as for speech recognition and other voice-enabled applications. Fujitsu's LifeBook, which weighs just 2.2 pounds and is only three-quarters of an inch thick with a 12.1-inch display, will enable users to make cell phone calls from the PC using the third-generation Universal Mobile Telecommunications System and the Evolution Data Optimized protocols. Numerous RF transmitters and antennas are built in, including an internal wide-area network , personal-area network and wireless local-area network.
"Fujitsu's LifeBook had to build in immunity to just about every source of radio-frequency emission there is, with all its internal radio transmitters and antennas," said Yuknis. "With the amount of RF energy being generated by Fujitsu's new LifeBook, an analog microphone was just too noisy for them."
The LifeBook uses two AKU2000 microphones to provide stereo-signal localization and to run noise-canceling algorithms to improve the voice signal by subtracting out both RF noise and background sounds. It uses two Akustica AKU2000s, which are connected to SigmaTel's STAC9228 audio codec by two wires. For future devices, Akustica's AKU- 2001 and SigmaTel's STAC9205 and STAC- 9255 codecs will simplify such multiple microphone installations by allowing the two microphones to share a single interface wire.
The AKU2000 and the AKU2001 integrate an acoustic transducer, analog preamplifier and 4th-order sigma-delta pulse density modulator to supply a single-bit digital output stream, which is intended to be decimated by a digital filter in an audio codec, DSP or other baseband processor.
The AKU2001 also includes tristate outputs, thereby allowing stereo signals from both left and right channels to be multiplexed on a single interface wire. And it simplifies microphone array applications where two microphones are used together for noise cancellation and beam steering.
Making pins count
"The AKU2001, which is pin-compatible with the AKU2000, is our next version and specifically targets microphone arrays by multiplexing the feed from multiple microphones onto a single wire," said Yuknis. "It cuts down on the number of pins on your codec and the number of wires you have to route through the hinge of a notebook PC."
Meanwhile, future designs of SigmaTel's four-channel, high-definition audio codec chips will include voice input to VoIP, instant messaging and speech recognition applications. The design will be able to simplify systems integration tasks by harnessing SigmaTel's STAC9205 and STAC9255 codecs. The SigmaTel codecs enable two-channel VoIP to run simultaneously with other two-channel stereo audio applications. The direct on-chip interface allows notebook manufacturers to handle two-channel high-defini- tion audio applications today, as well as to integrate up to four digital microphones for future stereo signal localization and noise-cancelling algorithms built into Microsoft's forthcoming Vista.