Learn the 2 Block Diagram of a Cellphone

Step by step Cellphone repair tutorial - Basic to Advance - Topic 01

How Cellphone Works?

A Cell-phone handset is basically composed of two sections,
which is RF and Baseband Sections.

Radio Frequency (RF) - The spectrum of electromagnetic energy between audio and light: 500 KHz to 300 GHz.

Cell phones communicate with nearby cell towers through RF waves, a form of energy located on the electromagnetic spectrum between FM radio waves and microwaves. Like FM radio waves, microwaves, visible light, and heat, they are a form of non-ionizing radiation.

Baseband
Describing a telecommunication system in which information is carried in digital form on a single unmultiplexed signal channel on the transmission medium.
Any frequency band on which information is superimposed, whether or not the band is multiplexed and information is sent on subbands. In this usage, there is sometimes the meaning that the frequency band is not shifted to some other frequency band but remains at its original place in the electromagnetic spectrum.

Cell-phone have three sections since baseband is differentiated by into two which is the Analog and Digital function while the RF section remains as a whole circuit section.. which is the following cosists.

1. Radio Frequency (RF Section - receiver and transmitter)
2. The Analog Baseband Processor
3. And the Digital Baseband Processor.

Radio frequency elements
The radio frequency section of the mobile phone is one of the crucial areas of the cell phone design. This area of the mobile phone contains all the transmitter and receiver circuits. Normally direct conversion techniques are generally used in the design for the mobile phone receiver.

The signal output from the receiver is applied to what is termed an IQ demodulator. Here the data in the form of "In-phase" and "Quadrature" components is applied to the IQ demodulator and the raw data extracted for further processing by the phone.

On the transmit side one of the key elements of the circuit design is to keep the battery consumption to a minimum. For GSM this is not too much of a problem. The modulation used is Gaussian Minimum Shift Keying. This form of signal does not incorporate amplitude variations and accordingly it does not need linear amplifiers. This is a distinct advantage because non linear RF amplifiers are more efficient than linear RF amplifiers.

Analog Baseband Processor
A/D and D/A section
The Analog Baseband compose of two parts, the analog-to-digital (A/D) signal and digital-to-analog (D/A) signal converters that link RF transceiver and the baseband circuits.

Control section
This is the section acts as the controller of the the input and output of any analog and digital signal.
Power Management
A power management section in mobile phones is designed to handle energy matters that is consumed in mobile phones. There are two main sub sections in a single power section.

Charging Section

A power distribution section is designed to distribute desired Voltages and currenst to the other sections of a phone. this section takes power from a battery (which is figured commonly 3.6 Volts)and in some places it converts or step down to various volts like 2.8 V 1.8V 1.6V etc.while on other place it also steps up the voltage like 4.8 V. this section is commonly designed around a power IC(and integrated circuit) which is used to distribute and regulate the voltage used in other components.
The Charging section is based on a charging IC which takes power from an external source and gives it to battery to make it again power up when it is exhausted. this section uses convertibly 6.4 V from an external battery charger and regulates it to 5.8V wile giving it to battery. The battery is made charged by this process and it is ready to use for the next session (a battery session is a time which is provided by the manufacturer of a cell phone for standby by condition of a mobile phone or talk condition.)

Audio Codecs Section
This section where analog and digital audio properties being process like the microphone, earpiece speaker headset and ring-tones and also the vibrator circuits.

Digital Baseband Processor
This is the part where All Application being process. Digital Baseband Processor section is used in mobile phones to handle data input and ouput signal like switching, driving applications commands and memory accessing and executing.
These are the parts and sections o a Digital Baseband Circuit were installed.
CPU
CPU( Centeral Processing Unit) The Central Processing Unit (CPU) is responsible for interpreting and executing most of the commands from the users interface. It is often called the "brains" of the microprocessor, central processor, "the brains of the computer"
Flash and Memory Storage Circuits
*RAM( Random Access Memory)
*ROM,Flash(Read Only Memory
Interfaces such as the following were also part on this section:
*Blutooth
*Wi-fi
*Camera
*Screen Display
*Keypads
*USB

*SIM-CardHere a typical overview of a block diagram on latest mobile phone designs.

Various mobile phones have different concepts and design on every aspects, but the methods and operational flow are all exactly the same. It differs on how and what certain IC chips and parts they are being used and installed to a certain mobile phone circuitry.

Step by step Cellphone repair tutorial - Basic to Advance - Topic 01