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Inside a Digital Cell Phone
When it comes to complexity, a cell phone could easily win an award when it comes to complexity per cubic inch. A cell phone is one of the most intricate and complicated devices that people use every day. Modern digital cell phones are capable of processing millions of calculations per second. They must do this to compress and decompress a voice stream.
When you take a digital cell phone apart you’ll find that it contains a number of individual parts:
• Circuit Board.
• Antenna.
• Liquid Crystal Display [LCD].
• Keyboard.
• Microphone.
• Speaker.
• Battery.
The cell phone’s circuit board is the heart of the phone system. Its analog-to-digital and digital-to-analog conversion chips translate outgoing audio signals from analog to digital. Then, it translates incoming signals from digital back to analog. A digital signal processor, or DSP, is a highly technical and customized processor designed to perform these signal manipulation calculations at high speeds.
The digital cell phone’s microprocessor takes care of all the main keyboard and display functions. It deals with command and control signals with the base station. It also coordinates the rest of the keyboard’s functionality.
Flash memory chips, and the phone’s ROM, provide room to store the phone’s operating system. It has customizable features like the phone directory. The power section and the radio frequency [RF] handle recharging, power management and deal with hundreds of FM channels. The RF also amplifies signals that travel to and from the antenna.
The cell phone display grew considerably in size as features were added to the phone. Most modern cell phones have built-in phone directories, games, and calculators. Many also have web browsers and PDAs delivered.
Most phones store information like the SID and MIN codes using internal Flash memory. Other phones use external cards like SmartMedia cards.
The speakers and microphones in a cell phone are tiny. So, it’s incredible how well most of these devices reproduce sound. Speakers are about the size of a dime, and microphones are no larger than a watch battery.
What’s really incredible about all of this cell phone technology, and functionality, is how fast the technology has developed. Think about it, 30 short years ago the technology to reproduce the functionality of a digital cell phone
would have filled an entire floor of an office building with gear. Now, it simply fits into a package that sits comfortably in the hand of a child!
Do you need a new cell phone battery? Be sure to buy a replacement cell phone battery from a reputable online merchant who sells cell phone batteries which are fully compatible with the manufacturers’ own brand replacements. LaptopsForLess.com has a huge selection of mobile phone batteries in stock, at very reasonable prices [often a fraction of the cost of manufacturers’ own brand replacements]. Brands stocked include: Audiovox, Ericsson, LG, Motorola, Nextel, Nokia, Samsung, Sprint, Sanyo and more…
Analog Cell Phones
Back in 1983, an analog cell phone standard called AMPS [Advanced Mobile Phone System] received approval by the FCC. It was first used in Chicago and used frequencies ranging between 824 megahertz [MHz] and 894 MHz. To create healthy competition, and keep prices low, the government required that two carriers be present in every market. One of these carriers was typically a local phone company, and the other a national carrier.
Each carrier was assigned 832 frequencies. The standard issue was 790 for voice use and 42 for data use [telephony housekeeping like registration and paging]. A pair of frequencies were used to create one channel [one to transmit, and one to receive]. Analog voice channel frequencies are normally 30 kHz wide. So, 30 kHz was selected as standard size because it gives the voice quality of a landline wired phone.
The two frequencies that make up the single channel are separated by 45 MHz. This keeps the frequencies from interfering with each other. So, there were 395 voice and 21 data channels.
After AMPS, another technology was introduced. It is known as Narrowband Advanced Mobile Phone Service [NAMPS]. This incorporates digital technology and allowed the system to carry around three times as many calls as AMPS. However, this is still considered analog because it can only operate on the 800 MHz band and doesn’t offer common digital cellular services like web browsing or email.
Enter Digital
The second generation of cell phones is 2G digital technology. These phones use the same radio technology as analog devices, but use it in a different way. The analog systems do not completely use the signal between the cellular network and the phone. Analog signal is not compressed and manipulated as easy as a digital signal. Companies can fit more channels on a given bandwidth. This makes digital systems more efficient.
A digital phone converts your voice into binary. This binary information [0s and 1s] gets compressed. This compressed information allows anywhere from three to ten digital cell phone calls to occupy the space of a single analog cell phone call.
Most of the digital cellular systems rely on frequency-shift keying [FSK]. FSK sends data back and forth over AMPS. FSK uses two frequencies. One is for 0s and the other is for 1s. The frequencies alternate rapidly between the two, and send their digital information between the phone and the cell tower. Modulation and encoding is required. This converts analog information to digital, compresses it, and converts it back again. After all of this it must maintain an acceptable level of voice quality! So, believe it or not, that little phone in your hand is quite a powerful device when coupled with cellular technology.
Do you need a new cell phone battery? Be sure to buy a replacement cell phone battery from a reputable online merchant who sells cell phone batteries which are fully compatible with the manufacturers’ own brand replacements. LaptopsForLess.com has a huge selection of mobile phone batteries in stock, at very reasonable prices [often a fraction of the cost of manufacturers’ own brand replacements]. Brands stocked include: Audiovox, Ericsson, LG, Motorola, Nextel, Nokia, Samsung, Sprint, Sanyo and more…