Digitally Assisted, Fully Integrated, Wideband Transmitters for High-Speed Millimeter-Wave Wireless Communication Links (original) (raw)

The millimeter-wave (mmW) range of the electromagnetic spectrum, which includes frequencies from around 30 to 300 GHz, offers some unique propagation properties and a vastly available bandwidth. Therefore, it enables relieving the overpopulated lower part of the spectrum and satisfying the huge data demands from the users. It also allows the proliferation of new applications such as automotive radar, high-speed personal area networks, and noninvasive surveillance, just to name a few of them. In addition, while in the past working at mmW frequencies was only possible using III-V technologies, the successive scaling of silicon-based technologies like CMOS and BiCMOS has brought mmW circuit designs and applications to the mass market. Many excellent books on RFIC design using silicon technologies have been published, and with the aid of the existing powerful simulation software, one can design RF circuits with acceptable performance quickly and with moderate effort. However, when it comes to mmW circuit design, succeeding is not that simple. Semiconductor technologies are struggled to their limits in terms of operation frequency and available power, and PVT variations can greatly jeopardize the device performance. This is especially critical in transmitters, which need to provide enough output power to compensate for the high path loss, while at the same time maintaining the bandwidth in a power-efficient way. Furthermore, the wide bandwidth and data throughput required by current communication applications are also pushing digital design to the limits in terms of sampling speed and power consumption, and it is, therefore, not straightforward to use DSP techniques to compensate for the RF imperfections. In this book, we present an approach to mmW circuit design using advanced RF circuit design and digital processing techniques at the same time. This way, front-end architectures that balance the requirements of the RF and DSP blocks can be selected, and it is possible to sense the operating conditions of the critical circuits in order to compensate for the imperfections and bring the performance back to the vii optimum values. All the design stages of a typical mmW transmitter are covered, from the link budget analysis to transistor-level design and system tests using high-order modulated signals. The procedure to present the different designs and subsystems is to first explain the concepts from a theoretical point of view, and then apply them to the design of an E-band 10-Gbps BiCMOS-integrated transmitter. Some previous knowledge of semiconductor devices, transmission systems, and signal theory is assumed from the reader, although theoretical concepts and expressions are introduced when required for the discussion. These prior concepts are sometimes explained in a rather intuitive way, as our intention is to focus more on the actual scope of the book: revisiting the traditional approaches and proposing new techniques appropriate for wideband and power-efficient mmW IC design. Nevertheless, references where the information is more thoroughly explained are provided, in case the reader feels some concepts are oversimplified or seeks further explanation. Chapters are intended to be self-contained, each with its own introduction and conclusion sections, so that most of them can be read independently. Nevertheless, they are ordered according to the natural design flow, starting from the system-level analysis and going down to the transistor-level design. Chapter 1 is a general introduction to millimeter waves, explaining the motivations to explore this frequency range and the technologies that make it possible. In Chap. 2, considerations for the link budget and system-level analysis are given, whereas Chap. 3 analyzes the typical imperfections that degrade the performance of mmW communication systems, showing how they affect the signal. One of the imperfections that most affects wideband mmW systems is transmitter I/Q imbalance. It is typically addressed as non-frequency selective, but in wideband and spectrally efficient systems this assumption is no longer true and different correction techniques need to be applied. Therefore, Chap. 4 is dedicated to I/Q imbalance analysis and compensation. The rest of the chapters deal with the circuit-level design of the core blocks of an integrated mmW transmitter front-end. Chapter 5 outlines a design methodology for BiCMOS mmW integrated circuits. Chapters 6-8 deal with the design of upconverters, power amplifiers, and power detectors, respectively. Different alternatives and trade-offs for the design of these blocks are first presented, and then design examples of real implemented circuits are given. These circuits are designed aiming at wideband operation and transmission of multi-Gbps signals, and they allow implementing the digitally assisted correction, self-healing and built-in integrated self-test (BIST) techniques outlined in the previous chapters. Finally, Chap. 9 presents an integrated and digitally assisted BiCMOS transmitter, which is able to transmit at 10-Gbps speeds in the E-band. The techniques presented in the previous chapters have been applied to its design. This book comes after years of research in the field of wideband-integrated mmW transmitters for high-speed communications. We have tried to gather all the wisdom and experience we have acquired in the way, because we believe that viii Preface Preface ix Government through its Ph.D. scholarship program, and the European Commission through its FP7 Research Program. xi Contents xv xvi Contents