EE Times Under the Hood - June 23, 2008 - (Page U74)

UTH0623ANALOG_pg72_82.qxd 6/10/08 4:24 PM Page 74 under the hood:: w w w. e e t i m e s . c o m ANALOG an unbalanced dipole antenna (stripped coax, really), which feeds an apparent discrete RF front end. The basestation cycles through each channel selected, affecting changes to the RichWave RTC6503 frequency synthesizer with built-in VCO, whose output mixes with the received signal to get to the 480-MHz intermediate frequency (IF) used in the design. After the mixer IF output is cleaned up in a surface acoustic wave (SAW) filter, audio and video signals must be further isolated. The former is addressed in an Atmel (Temic) U2860-B dual-channel FM sound demodulator, with only one of two channels needed for the SecurityMan’s monaural output. Baseband composite video is derived in a Zarlink-marked SL1461SA PLL FM demodulator, now seemingly an orphan part, given Zarlink’s sale of its tuner and demodulator device business to Intel. Intel no longer lists the product as an active device in its demodulator family. Outside of the A/V receiver circuits, the primary remaining base unit electronics are a 5-V regulator (LM7805) and another 8-bit microcontroller. Elan Microelectronics’ EM78P153 MCU houses its own stash of about 7 kbits of one-time PROM. DIP-switch channel-select, reset, RF module control and blinky-light duties are all handled in this small, 14-pin device. The electronic design relies on inexpensive, low-integration devices, and the CMOS sensor is arguably the most complex IC present. I couldn’t help but admire the castmetal enclosures for the bullet cameras. These housings may represent the single most-expensive part of the total hardware bill of materials, surely under $50. Despite the wireless descriptor, I was overwhelmed by the amount of wired stuff that came in the blisterpacked setup. Three ac adapters— one for the base and one for each camera—made for quite a bowl of spaghetti, despite the reliance on RF links. If only we could handle power as conveniently and wire-free as the audio/video feeds seen in the SecurityMan/AEE design. ■ • w w w. t e c h o n l i n e . c o m switch on the base unit, and output from the base is via RCA-jack composite video and monaural audio for use with any TV monitor. A 100-meter range in clear line of sight is claimed, but you can bank on something far less in a real-world installation. The cameras contain the lensed imager, microphone and RF transmission circuitry, along with a ring of IR LEDs to provide human-invisible flood illumination for nighttime use. AEE claims 5-lux minimum visible-light illumination and 0-lux (with IR on) sensitivity to 7 meters. Transmission signals come over 2414-, 2432-, 2450- or 2468-MHz center frequencies (18-MHz channel separation) for some combination of multicamera utility and simple interference avoidance. An OmniVision OV7930 provides 510 x 492 NTSC video output directly, handling everything from raw image collection to gain control, auto color balance and NTSC formatting/conversion. The camera electronics consist of a BJX (Shenzhen Bojuxing Industrial Development) BJ8P153 8-bit MCU ROM controller and RichWave RTC6701 CMOS 2.4-GHz FM/FSK (frequency-shift-keying) transmitter running at 10 mW of RF output power. Although the RichWave part supports digital FSK capability, the design uses only the device’s simpler analog RF frequency-modulation (FM) func- IN BRIEF The NiteCam2 kit brings a consumer-grade opportunity for extending vigilance to the home. So-so video quality and signal fade in a highly informal “out-of-boxexperience” test suggested design compromises targeted at cost reduction. But high-bandwidth, bulletproof wireless links in crowded spectrum are no easy task, and robust solutions require serious semiconductor content, anathema in an environment of blister-pack pricing. Low cost means lowered expectations, and the NiteCam2 inexpensively gets households or small businesses set up with some level of security. tion to up-convert the NTSC output of the OmniVision image sensor. A simple wire antenna delivers RF from a stub protruding out the back of the camera. With a less-sophisticated FM scheme, there is little protection against outside interferers in the increasingly crowded ISM band. Lacking the ultratight channels, errorcorrection and/or coding for interference-resistance possible with a morecomplex digital radio, the SecurityMan leads to some compromise. The pureanalog approach wins out at the expense of radio robustness. The basestation receiver antenna is Component focus The NiteCam2 presents a classic case of dichotomy in integration. On the one hand, the core imaging of the solution relies on tremendous progress from the rapidly advancing CMOS sensor arena.Along with its CMOS photodiode array, the OmniVision part ropes in digitally controllable aspects of image processing— much done in the analog domain—to deliver a “light-in, NTSC video-out” device. By contrast, many of the RF elements are still found in fairly discrete form.The receiver is implemented with fairly long-standing IC building blocks for the separate audio and video demodulators and the frequency synthesizers.The receiver module also used a reasonably large number of active and passive discrete components for mixer and filter functions surrounding the IC building blocks. Could it all be collapsed to a single chip, more in line with the transmitter side of the cameras? You bet.Are there economies to integration in the fastmoving world of inexpensive consumer devices? Outside of a widely purposed image sensor chip, it would seem the answer here is “not so much.” 74 Electronic Engineering Times, TechOnline | June 23, 2008 http://www.eetimes.com http://www.techonline.com

Table of Contents Feed for the Digital Edition of Under the Hood - June 23, 2008

Under the Hood - June 23, 2008 Extreme Design: SuitSat Pushes Desigers' Limits Evolution of the Smart Phone Mature Devices get Rolly Rocking GPS: Garmin Nuvi 750 vs. HP iPaq 310 Inside the Sony OLED TV Multizone Dgital Audio Flip Ultra Camcorder - An Ode to Clean Design Robot Guitar Tunes Itself E-book is a Sight for Sore Eyes Scientific Calculator Boils Down to Two ICs $100 BOM Eludes First OLPC Laptop 45 nm: What Intel Didn't Tell You Next Step in NAND Flash Evolution Surveillance on a Shoestring Hot 3G Phone Owes Debt to Analog SecurID Fob: Single-Chip Safety Net

Under the Hood - June 23, 2008

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