New technology developed to transport of radio frequency (RF) through optical methods could improve digital & satellite communication

Source: The post is based on the article “New technology developed to transport of radio frequency (RF) through optical methods could improve digital & satellite communication”  published in PIB on 24th August 2023.

What is the News?

Researchers at IIT Madras have developed a prototype in the Next-Generation Photonic Analog-to-Digital Converters (NG-PADC) project.

What is Next-Generation Photonic Analog-to-Digital Converters (NG-PADC)?

NG-PADC prototypes have the capability to instantly measure, generate, and transmit Radio Frequency (RF) using optical methods. 

This could bring significant changes to various sectors, including faster digital communication, improved satellite communication, better medical imaging, and advanced photonic radars.

What are the limitations of traditional electronic Analog-to-digital converters (ADCs)?

Analog-to-digital converters (ADCs) are crucial for developing advanced digital receivers.

But the traditional electronic ADCs(EADCs) have limitations, especially in maintaining vertical resolution at high bandwidths. 

Photonics offers two potential solutions to overcome this limitation:

Stretching RF Signals: RF signals can be modulated onto a spectrally rich optical pulsed source and then stretched in the optical domain through a dispersive medium.This transformation converts high-frequency RF signals into effectively lower-frequency signals.As a result, the input bandwidth requirements for the backend ADC are significantly reduced.

Stable Optical Clocks: Photonics can utilize optical clocks generated by short-pulsed lasers. These optical clocks have much smaller timing fluctuations (timing jitter) compared to electronic clocks.

–When high-bandwidth RF signals are sampled using stable optical clocks, it leads to a much higher effective number of bits (ENOB) compared to electronic clocks.This enables the digitization of signals with much greater precision.

How can NG-PADC help in this?

NG-PADC incorporates a time-stretched photonic ADC with an effective bandwidth 12 times higher than a corresponding EADC. This enables the sampling of higher bandwidth signals using lower bandwidth EADCs.

These advancements are particularly beneficial for digital coherent communication with high-bandwidth signals.