The aim of this course is to present the key underlying signal-processing principles used in software-defined radio (SDR) analysis and design. The various chapters span topics ranging from analog and digital modulation to radio frequency (RF) and digital signal processing and data conversion.
The SDR is defined as a “radio in which some or all of the physical layer functions are software defined”. This implies that the architecture is flexible such that the radio may be configured, occasionally in real time, to adapt to various air standards and waveforms, frequency bands, bandwidths, and modes of operation. That is, the SDR is a multifunctional, programmable, and easy to upgrade radio that can support a variety of services and standards while at the same time provide a low-cost power-efficient solution.
The course is divided into four sections.
Section 1 is comprised of first two chapters. The Chapter 1 represents an introduction in the software-defined radio, presenting the evolution of different SDR architecture. The Chapter 2 of the course deals with analog modulation techniques that are still relevant and widely in use today. Spectral shaping functions and their implementations are also discussed in detail. Next chapter addresses digital modulation schemes ranging from simple M -PSK and M-QAM methods to spread spectrum and OFDM. In both chapters figures of merit and performance measures such as SNR and BER under various channel conditions are provided.
Section 2 deals mainly with the RF and analog baseband. This section is divided into three chapters. Chapter 4 addresses the basics of noise and link budget analysis. Chapter 5 deals with nonlinearity specifications and analysis of memoryless systems. Design parameters such as second and third order input-referred intercept points, intermodulation products, harmonics, cross-modulation, and adjacent channel linearity specifications are a few of the topics discussed. Similarly, Chapter 6 further addresses RF and analog design principles and analysis techniques with special emphasis on performance and figures of merit. Topics include receiver selectivity, fidelity and dynamic range, degradation due to AM/AM and AM/PM, frequency accuracy and tuning, EVM and waveform quality factor and adjacent channel leakage ratio are among the topics discussed.
Section 3 addresses sampling and data conversion In Chapter 7, the basic principles of baseband and bandpass sampling are studied in detail. The resolution of the data converter as related to sampling rate, effective number of bits, peak to average power ratio, and bandwidth are derived. The chapter concludes with an in-depth analysis of the automatic gain control (AGC) algorithm.
In Chapter 8, the various Nyquist sampling converter architectures are examined in detail. Particular attention is paid to the pros and cons of each architecture as well as the essential design principles and performance of each. Chapter 9 discusses the principles of oversampled data converters. The two main architectures, namely continuous-time and discrete-time ΔΣ -modulators, are presented in detail.
Chapter 10 from Section 4 introduces the basics of multirate signal processing techniques such as interpolation and decimation. A detailed study of the various filtering structures used to perform these basic operations is provided. Topics such as polyphase filtering structures, half-band and M-band filters, and cascaded integrator-comb filters are considered. Irrational sampling rate conversion techniques that employ interpolating polynomials such as the Lagrange polynomial are also discussed. An effective structure that enables the implementation of such polynomial interpolators, namely the Farrow filter, is also discussed.
The hardware components used at the laboratory to implement software-defined radio environment are based on “RTL-SDR” device used as receiver and “TIVDIO 5W/15W Wireless FM Transmitter” and “Whole House FM Transmitter 3.0” used for RF transmission. Other devices to implement SDR systems, based on “USRP” hardware and “Raspberry Pi”, are also considered. The “RTL-SDR” can be used to acquire and sample RF (radio-frequency signals transmitted in the frequency range 25MHz to 1.75GHz, and the MATLAB, Simulink and other programming environments can be used to develop receivers using first principle DSP (digital signal processing) algorithms. Signals that the “RTL-SDR” hardware can receive include: FM radio, UHF band signals, ISM signals, GSM, 3G and LTE mobile radio, GPS and satellite signals. In this course we present different SDR methods by viewing and analyzing downconverted RF signals in the time and frequency domains, and then provide extensive DSP enabled SDR design exercises which the students can learn from. The hands-on SDR design examples begin with AM and FM receivers, and move on to the more challenging aspects of PHY layer DSP, where receive filter chains, real-time channelisers, and advanced concepts such as carrier synchronisers, digital PLL designs and QPSK timing and phase synchronisers are implemented.
