This chapter presents a new idea that is to optimize the lossy junctions as part of the optimization of the equalizers used in a multistage amplifier. The lossy junctions are introduced between lossless unit elements (UEs) composing an equalizer so that the equalizers can be used to offset power gain issues at low frequencies. In this resistive matching case, the real frequency technique (RFT) is used to directly synthesize the resistors and the UEs to satisfy both gain flatness and stability. The distributed multistage amplifier RFT is successfully modified to introduce the lossy elements and incorporated into a CAD program called SYNTARD. The chapter first validates the new concept by designing a single-stage 0.1-5 GHz microwave amplifier. Then, it uses the modified multistage RFT to design a two-stage 0.1-9 GHz broadband amplifier. In order to realize the equalizers, the chapter gives a lossy UE network synthesis method.

This book focuses on the authors' Real Frequency Technique (RFT) and its application to a wide variety of multi-stage microwave amplifiers and active filters, and passive equalizers for radar pulse shaping and antenna return loss applications. The first two chapters review the fundamentals of microwave amplifier design and provide a description of the RFT. Each subsequent chapter introduces a new type of amplifier or circuit design, reviews its design problems, and explains how the RFT can be adapted to solve these problems. The authors take a practical approach by summarizing the design steps and giving numerous examples of amplifier realizations and measured responses.

We will discuss the spectral power density in the cases of the coherent and differential modulations. We will also discuss the effect of the noise.

We have to transmit the signal s(t) at the discreet times ti, and s(ti) are the samples. If these samples s(ti) are quite numerous, then it is possible to recover the signal s(t). This is a consequence of Shannon's theorem.

In many applications of communications, we require amplification of the signals. To avoid obstacles, the communications very often go through a satellite and the conception of reception microwave amplifiers is different from these emission microwave amplifiers. At the emission, the amplitude of the signals is powerful but at reception the amplitude is small. The characteristics of a microwave amplifier are gain, stability, noise, power, linearity, etc. We will deal with only the first three properties and give only a measure of the latter two. The choice of the active element will be given by the central frequency f0, the passband Δf, the gain G and the noise factor F. In the microwave domain, we use generally field effect transistor (FET) made up of gallium arsenide (GaAs).

A dielectric resonator (DR) is a ceramic microwave resonator with equivalent characteristics as a microwave cavity but with weak dimensions. TE01δ is the fundamental mode and then the DR is equivalent to a magnetic dipole. The dimensions are about λg=λ0εr, where εr is the relative electric constant, which is important (about 40). Also the important quality factor of the DR alone Q0 involves that the energy is confined in the resonator, and radiation losses are weak. In general, the used material is the barium titanate (Ba2Ti9O23) and the oscillations go from 2 to 20 GHz.

The transmission’s supports are the radio beams, the satellites, the optic fibers, and the radar. We give some quick information on these support elements.

Couplers can also be used to characterize the return loss of a structure. There are two methods: first, a zero method where we compare the unknown reflection coefficient to this of an etalon load; second, a reflectometric method where we separate and compare the incident and reflected waves. In this chapter, we will discuss only about the zero methods.

In order to bring more and more information, we need efficient transmission systems such as: radio beams (with numerical rate ranging from 50 to 100 Mbits/s); microwave circular wave guide (up to 35–50 GHz), which can transport more than 150,000 phone lines; optic fiber with laser.

We have to transmit an analog wave that is coded. Then we introduce an error that can be considered as a noise: the quantization noise. If the quantization samples are of equal amplitude, then the smaller the signal, the more significant the relative error.

We want to transmit a binary and noisy signal x(t) that is written in a simple form as:x(t)=∑k=−∞+∞akδ(t−kT)+n(t) x(t) is a series of Dirac impulses δ(t); weighted by the binary digit ak = ±1; n(t) is a white Gaussian noise with a bilateral density power N0/2.

We begin to give a very simple “filter” made of only one guide-resonator and two irises. This chapter will give a description and the method of filtering of this system. The analysis considers: the iris alone; the resonator (cavity) alone; and the resonator between two iris.

Digital communications plays an important role in numerical transmission systems due to the proliferation of radio beams, satellite, optic fibbers, radar, and mobile wireless systems. This book provides the fundamentals and basic design techniques of digital communications with an emphasis on the systems of telecommunication and the principles of baseband transmission. With a focus on examples and exercises, this book will prepare you with a practical and real-life treatment of communication problems.This book provides: A complete analysis of the structures used for emission or reception technologyA set of approaches for implementation in current and future circuit designA summary of the design steps with examples and exercises for each circuit

The propagation structure is made up of three conductors in a homogeneous medium (only one dielectric). We can see that two modes can propagate: the symmetrical mode (even mode) and the non-symmetrical mode (odd mode). These are called the normal modes of the coupler.

Synthesis is a method of identification between a prototype and a physical structure. The filter is formed of n successive cavities. The space between two irises is approximate to λG0/2. The iris are formed by diaphragms, coupling holes, self bars and all have an equivalent circuit given by a parallel and imaginary admittance jX¯.

The information has to be transmitted in the form of binary digit (bit). To do this, the analogical signal is converted into a (digital) numerical signal by sampling the signal.

We consider the lines of propagation in which length and coupling are about the wavelength λ. We use to say that the effect is distributed. The electromagnetic (EM) field of the line (1) induces an EM field of the line (2) and reciprocally. The phenomenon is induced on a wavelength λ that is around some Giga Hertz = GHz = 109 Hz in microwaves.λ=cf=300,000km/s109=3×108109=0.3m