Software defined radio: SDR is a radio communication system that employs reconfigurable software-based components for processing and conversion of digital signals. SDR can transmit and receive signals at different frequencies to implement wireless standards from FM radio to Wi-Fi and LTE.

Fig:Software Defined Ratio:

As shown in Figure above, a typical SDR system consists of an analog front-end and a digital back-end. The analog front-end handles the transmit (Tx) and receive (Rx) functions of a radio communication system. The highest bandwidth SDR platforms are designed to operate over a broad range of frequencies; usually near DC-18 GHz. The front-end of an SDR system handles signals in the analog domain, the back-end processes signals in the digital domain.

The architecture of a typical SDR platform consists of the following boards: power, digital, time, receive (Rx) and transmit (Tx) modules. The boards are connected using high speed cables to ensure fast transfer of data from one board to another. The function of the power board is to supply power to the daughter boards of an SDR system.

Fig:Receive (Rx) and transmit (Tx) chains of an SDR system:

Receive (Rx) board of an SDR platform consists of multiple independent receive channels. Each receive channel is capable of performing the receive functions and handles signals in the analog domain. Analog signals from the Rx board are channeled to an independent chain consisting of amplifiers, down converters, various filters and an ADC for conversion to digital domain. Like the receive (Rx) board, the transmit (Tx) board features multiple independent transmit channels. Each Tx channel is capable of performing transmit functions and sends signals in analog format from the DAC, up converter, filter and amplification stages.