The analog signal processing is substituted everywhere by its digital counterpart because of its higher accuracy and flexibility, its much lower cost and because in digital signal processing there is no need for regular calibration as it is required in the analog systems. The most important feature of digital approach is that the HW and SW components can be fully separated and the same HW, referred to as a universal HW device, can be used to implement very different applications. Although digital signal processing has been around everywhere in the low frequency applications for many years, until this time it could not satisfy the requirements of RF and microwave engineering. The main challenges in RF and microwave radio communications and measurements are: (i) implementation of ultra wide dynamic range (limited by the quantization noise and linearity) and (ii) minimize sampling rate required. In our time the situation is changing rapidly. Software Defined Radio, Universal Software Radio Peripheral and Virtual Instrumentation all mean that a universal HW device is used to extract the complex envelope of an RF bandpass signal to be demodulated or analyzed, and the implementation of radio receiver or signal analyzer is implemented entirely in SW. The complex envelope, processed in SW, carries all information available in the RF signal and assures the minimum sampling rate which is determined by the bandwidth of RF signal. The complex envelope represents fully the RF bandpass signal without any distortion and every RF bandpass signal can be reconstructed from its complex envelope without any distortion. This tutorial surveys the theory of complex envelopes, shows how the baseband equivalent models of RF systems can be derived and demonstrates how different radio transceivers and test equipment can be implemented by means of the same universal RF HW device in the 2.4-GHz ISM frequency band.
ASJC Scopus subject areas
- Electrical and Electronic Engineering
- Computer Science Applications