Electronics Manufacturing – M528

Digesting the Apple iPhone

Apple will be launching it's first mobile phone effort this June in the US with the iPhone. Steve Jobs, when announcing the phone, claimed that it was five years ahead of any other phone. But what makes the iPhone so special? Apple are being characteristically secretive about the hardware details, however, there are some hints out there. By analysing these, predictions can be made about the technology and components that might be used.

The Screen

The big selling point of the iPhone is its main interface, a intuitive touch screen system called Multi-touch. It has been shown that the touch screen only works with a finger, not other items such as a fingernail. Therefore the touch screen is most likely a capacitive touch screen like the MicroTouch ClearTek II from 3M. Capacitive touch screens are coated with a thin conductive material, typically indium tin oxide, which is electrically charged creating a controlled capacitor. When another device that exhibits capacitance, like a person's finger, touches the screen the capacitance field is altered and the position of the finger can be worked out. Capacitive touch screens are also ideal for use in the iPhone because they are one of the clearest touch screen methods at just over 90% light transmission, compared to 75% with resistive technologies for example, which use changes in resistance due to screen depression. These screens are also resistant to scratches and are not effected by other contaminants.

3M's Capacitive Touch Screen Technology

Resistive touch screens are the traditional method for use in mobile phones. These screens require the surface layer to be 'pushed in' slightly by the pointing device. This then changes a resistance value showing the location the pointer. This type of touch screen would generally be even more resistant to scratches than a capacitive touch screen because there in no external layer, but because it has so many more layers, it has a much reduced visibility.

Resistive Touch Screens

Under the touch screen lies a 320 x 480 pixel, 3.5 inch liquid crystal display. None of the main LCD manufactures (Samsung, LG Philips, AUO, Sharp) sell a 3.5 inch screen at 160 pixels per inch off the shelf. However the AUO H241QL01 is a likely basis for the screen, at 2.4 inches it displays 160 pixels per inch with 16 million colours. This display uses LTPS (low temperature poly-silicon) to form the pixel array. LTPS is similar to the materials and technique used in semi-conductor manufacturing, but at a lower temperature because it is applied to glass, not a silicon wafer. A p-Si (poly-silicon) layer is applied to the glass substrate and then a photo-resist layer is applied. This layer is then exposed under a UV light through a filter. The exposed portions are then removed in the development stage, leaving the underlying p-Si layer and the non-exposed photo-resist sections. This is then baked and etched before removing the last of the photo-resist with an organic solvent. This process is then repeated four more times to build up layers of p-Si to form the transistors. This allows the driving circuit of the LCD to be integrated onto the glass substrate, meaning a more compact design and lower unit cost. Also, LTPS has 100 times higher mobility than conventional amorphous silicon, so the pixel change time can be achieved by a smaller TFT, and so more of the pixel area is for light transmission.

LCD Framework LCD Theory

The Engin

In the heart of the iPhone lies its processors. There is currently no advertised specification for the processors, however it has been claimed that Apple will be contributing to the ARM back-end of the LLVM open-source project with a variety of improvements including support for Darwin, the core of Apple's operating system. LLVM (Low Level Virtual Machine) is a project started in 2000 at the University of Illinois. It is basically a C compiler, but based on a virtual, RISC like instruction set rather than chip dependent instruction set. C code can then be used on any architecture supported by LLVM (currently X86, X86-64, PowerPC 32/64, ARM, Thumb, IA-64, Alpha and SPARC). If this is true then it could be assumed that Apple will be using ARM in the iPhone, which is advertised as running the same basic operating system as Apple Macintoshes. One such processor, that has been suggested, is the Marvell ARM based PXA320 series processor. The A320 is a 800MHz processor with a 2D graphics accelerator. This processor has many integrated features, including WiFi support and a large frame buffer for streaming video like H.264, which is used in Apple's QuickTime application. It is designed for the advanced smart-phone market.

The iPhone is a GSM based mobile phone phone operating on four bands (850, 900, 1800, 1900). The reason given for not using the latest 3G technology was given as power issues and compatibility. The lack of 3G will reduce the iPhone's download capacity. The best it can offer over a mobile network is EDGE (Enhanced Data rates for GSM Evolution). EDGE expands existing GSM networks by upgrading only the transceivers in the base stations. It uses 8 phase shift keying and greater redundancy to achieve up to three times the data rate of GSM. The iPhone also has a WiFi (802.11 b/g) system built in so that higher data rates can be achieved when in range of a WiFi network. These technologies are mature and so the actual implementation in the iPhone, along with the Bluetooth, will be very much dependent on the supplier of the main processors, and would probably involve System on Chip technology from Samsung, who produced SoC for Apple's iPods.

Other Components

Apple have also added a proximity sensor to the iPhone so that the display and touch screen input can be disabled when the phone put in a pocket. An accelerometer in included to rotate the display from portrait and landscape and back as the phone is physically rotated. The main data store, where images, music, video, phone numbers and the operating system will be stored is a 4 or 8 GB Flash unit (there are two models of the phone, this is the only difference).

As in all Apple computers, there is an ambient light sensor to adjust the screen brightness automatically according to conditions, to reduce power consumption. The iPhone does have some real buttons as well, a 'Home' button on the front, volume on the side and power on the top. There is also an Apple standard 30 pin iPod connector, a loud-speaker and a microphone. The battery will apparently last for 5 hours whilst using the network or watching video, and 16 hours whilst listening to music.


The iPhone has some new, cutting edge components. However these hardware components are not new concepts, just the very latest iterations. So why is it 5 years ahead of the competition now? I believe that the real advantage the iPhone's hardware has over its competitors' is in the choice of touch screen technology used coupled with the software user interface that supports it. The use of a finger is much more convenient over a stylus, and a very clear, high resoloution display allows this interface to work. This, together with Apple's attention to detail, like the proximity sensor, makes the iPhone innovative. However the hardware alone is not enough to push it 5 years ahead, as competitors start to copy ideas and come up with competing products. This might be achieved with Apple's software.

[1] Pogue, D. (2007). The Ultimate iPhone Frequently Asked Questions. Retrieved March 28, 2007, from http://pogue.blogs.nytimes.com/2007/01/11/the-ultimate-iphone-frequently-asked-questions/
[2] Wikipedia. (n. d.). Touchscreen. Retrieved March 28, 2007, from http://en.wikipedia.org/wiki/Touchscreen
[3] AUO. (n. d.). TFT LCD Introduction. Retrieved March 29, 2007, from http://www.auo.com/auoDEV/technology.php?sec=tftIntro&ls=en
[4] AUO. (n. d.). LTPS. Retrieved March 29, 2007, from http://www.auo.com/auoDEV/technology.php?sec=LTPS&ls=en
[5] Jobs, S. (January 2007). Mac World San Francisco 2007 Keynote Address. Retrieved March 29, 2007, from http://www.apple.com/quicktime/qtv/mwsf07/
[6] Ecker, C. (January 30, 2007). iPhone Processor: ARM? Samsung? XScale?. Retrieved March 30, 2007, from http://arstechnica.com/journals/apple.ars/2007/1/30/6824
[7] Lattner, C. (January 16, 2007). [LLVMdev] LLVM ARM backend enhancements. Retrieved March 30, 2007, from http://lists.cs.uiuc.edu/pipermail/llvmdev/2007-January/007813.html
[8] Fastpoint. (n. d.). About 8-Wire Resistive Touchscreens. Retrieved March 30, 2007, from http://www.fastpoint.com/touchscreens/resistive-touchscreens.html
[9] 3M. (n. d.). MicroTouch™ ClearTek™ II Capacitive Touch Screen. Retrieved March 28, 2007, from http://solutions.3m.com/wps/portal/3M/en_US/3MTouchSystems/TS/Solutions/TouchScreens/ClearTekII/