Blackberry Storm has some good qualities, and some not so good - Embedded.com

Blackberry Storm has some good qualities, and some not so good

The BlackBerry Storm came out not too long after I purchased my Blackberry Curve. Like lots of the latest consumer electronics devices, you're always hesitant to jump in and make a purchase, because you know your device will be trumped by something cooler in a very short time.

That was the case with my Curve, but not exactly. Shortly after I acquired my Curve, the Storm crossed my desk, as the object of a Tear Down. My first inclination with a Tear Down is to try the device out for a while, to get a feel for the user experience. In this case, it was to see what I was missing out on.

To my surprise (and delight), I found out that the Storm doesn't have a better user experience. In fact, I like my Curve better. The biggest reason for that is the touch interface that accompanies the Storm. I found it quite difficult to press the right buttons. I may have big fingers, but they're not so big that I should have that much trouble with the interface.

Being the engineer that I am, I decided not to let that one design flaw completely ruin the user experience, although it was hard to get passed that point. I found that as a telephone, the Storm worked really well. And that's an important component, although I use the phone more for e-mail and texting than I do as a phone (nobody calls anybody anymore, do they?).

The second feature I found to be quite attractive was the imaging quality, both for still images and for video. So that's where my Tear Down started. I wanted to find out what was the cause of those qualities that I found to be so appealing.

The sensor that's in the Blackberry Storm is from OmniVision Technologies, the OV3647. It's a low-power, low-cost CMOS image sensor. Containing a parallel interface as well as a mobile digital display interface (MDDI), the sensor has a resolution of 3 Mpixels running at 15 frames/s. It has embedded phase-locked loop (PLL) and can be embedded into a module that's 7 by 7 by 5 mm, as is the case in the Storm. It has an embedded 1.5-V regulator for operation at full power, but the core power is about 1.4 V.

View the full-size image

The OV3647, which is related to the sensor in RIM's Blackberry Curve handset (the OV2640), supports a raw RGB output format, image sizes of QV-XGA and XGA, and has a programmable frame rate. Image quality controls like lens correction, auto exposure, auto gain, auto balance, and defect pixel canceling help enhance the images, along with support for LED and flash-strobe mode.

One of the unique features of the OV3647 is that it contains Qualcomm's proprietary MDDI. This is a key differentiator because it provides a proven solution for the interconnect challenge provided by the hinge in a flip (clamshell) phone. This reduces the wire cost, and ultimately reduces the overall system cost.

According to the engineers at OmniVision, the interface also helps reduce the EMI in the differential signaling protocol. This, in turn, eliminates the need to use a parallel port where you've got eight data bits swinging at 1.8 V with a clock and two syncs signals.

While the Storm obviously doesn't employ a clamshell design, the EMI is reduced nonetheless. Qualcomm supports MDDI on most of its newer chip sets. Hence, it gives OmniVision easier entry into a Qualcomm design.

While the phone was designed by RIM, the designers at OmniVision were involved in integrating the sensor into the handset. This process occurred about 18 months ago.

While it's obviously a hardware integration challenge, there were some software issues that OmniVision had to iron out with RIM, like which settings should be used. OmniVision's applications team worked hand in hand with RIM to get the best image quality, resolution, etc. That led to OmniVision doing some scripting for the Storm and tuning the image parameters, like the lens correction and the defect correction, so the image looks the best regardless of temperature. The OmniVision developers also had to ensure that they provided the modes for all image sizes.

The makings of a world phone
The power amplifier (PA) in the Storm is a Wideband CDMA HSPA UMTS model, the AWT6241, from Anadigics. The device provides the amplification for the phone's 3G mode. This particular model is a world phone that runs on Verizon's CDMA network in the U.S. It enters roaming mode while in Europe, taking advantage of a GSM /EDGE power amplifier.

RIM chose the AWT6241 because of its high efficiency and high output power. The device is part of Anadigics' third-generation High-Efficiency, Low-Power (HELP3) product line. It's real claim to fame is its low quiescent current and the high efficiency at backed-off power. The result is a longer battery life, which is essential in a device like that Storm that contains a touch screen, a web browser, an e-mail client, and lots of other bells and whistles.

“For the IMT band, the 6241 is compatible with the Qualcomm chip set which is really the heart and soul of the Storm,” says Bruce Webber, director of marketing for Anadigics' wireless products. “Sometime next year, we'll have our fourth generation HELP parts, which offer even further improvements in efficiency and quiescent current.”

Note that in the design of a handset, there are some shortcuts you can take, and others you should avoid. Handsets are obviously space-constrained, and designers would prefer to use a single-sided board rather than a double-sided board.

Webber says, “One of the things we've seen is that the continuing drive to reduce board area and BOM costs is causing people to leave out matching components. They'll try to do a one- or two-component match and sometimes that's not ideal. You need to leave yourself enough flexibility to match the power amp to the duplexer that's selected for best power output efficiency. Otherwise you can end up having problems with linearity or even oscillation under some circumstances.”

Anadigics provides reference designs for many of its parts. And the company is quick to point out that designers shouldn't get too hung up on saving components at the expense of good matching between the components and the RF subsystem. Because that's where you can achieve the high efficiency, good linearity, and low spurious emissions, while simultaneously resulting in good RF performance.

“The end user might not be aware of all the stuff that goes on inside, but they certainly know when a call gets dropped,” adds Webber.

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