In a basic smartphone, there are several components which are shown in the above diagram.
Let’s start with an Antenna which uses to transmit and receive the signals. Diplexer or filter is used because the transmitter and receiver frequency is different. It will filter out desired signals and also called as double band bandpass filter.
In RF front end incoming signal reaches RF Low noise amplifier (LNA) which amplify the low power signal without degrading the sign to noise ratio (SNR). LNA main role is to reduce unwanted noise and amplify weak signals.
Next block is Mixer which used to down convert the signal with the help of local oscillator (LO) for further processing.
fd (Down conversion frequency)=fs(Signal frequency)-fl(LO frequency).
After down converting the signal it need to amplify and filter it which can be done through (Intermediate frequency amplifier and Bandpass filter).
Further signal need to demodulate to get an original signal from a carrier signal. Subsequently signal goes through Analog to Digital converter (A/D) and Digital to Analog converter (D/A) and filter block. Speech, video, data will get access from these block.
Transmitter part exactly works opposite to receiver where signal needs to modulate then feed to IF amplifier followed by a mixer. During transmission frequency needs to upconvert the signal which is done through mixer and LO block
fu (Up conversion frequency)=fs(Signal frequency) + fl(LO frequency).
These fu sent to the antenna via RF power amplifier and filter.
Human interface, Dialing, memory, battery power, Camera, Zoom lenses and sensors are control through microprocessor circuit.