Basic Working Principle of Mobile Phone

Basic Working Principle of Mobile Phone

As we discuss in the previous post about "How to Repair your mobile: Theory, Repairing tricks and basic ideas" , now we are going to learn about the Types of mobile phone.
There are two types of mobile phones they are.
  • CDMA (Code Division Multiple Access)
  • GSM (Global Standard for Mobile Network)
GSM network use TDMA Technology (Time Division Multiple Access) , in this Chapter we are discussing about GSM Technology.

Diagram showing Basic working Principle of Mobile phone
Diagram showing Basic working Principle of Mobile phone


When we press the power on switch a reset signal will apply on Power IC and it switch on different power regulators in two steps. In the first step it switch on power supply to Logic Stage(Base Module) and some supply to RF IC.

Base Band Supply includes the supply of CPU (V core supply 1.2-1.8 Volts), RAM,Flash and EEPROM(Electrically Programmable and Electrically Erasable Program Memory) etc.In the next step audio,Camera, VCO, LCD supply etc. These supply are generally 2-8 volts only apply when calling or when attending a call. 

The RF Stage receive and transmit GSM signal in a digital form. Rx signal from the antenna passes to Antenna Switch. Then it get filtered Duplex and send to Band Pass Filters and then feed to RF IC, In the RF IC it mixed with VCO frequency and converted into IQ (In phase and Quad-rate).

IQ signal then feed to Base band there it converted to Display and Audio signals. Display Data will sent to LCD and Audio Signal to Speakers. The Transmission Signal (Tx), Sound Signal from the microphone , Messenges, photo etc. will process in the CPU and converted to digital form in A.D Converter (AD and DA Converter present in Audio Processing IC) and then send to RF IC where it processed and converted to GSM signal. Here also VCO signal is used for mixing, actually the process is modulation the carrier frequency is VCO signal that may be 900 Mhz ,  1800 Mhz, 1900 Mhz depending up on the band used.

The signal then amplified through a power amplifier (P.A) and then send to Antenna switch, antenna switch is the common  gate for Rx and Tx signals.

From the antenna switch it passed to antenna and then to AIR. From the air, any one who operates antenna terminal receive the signal and then send to the respective Phones.

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