the properties that problems have in common. Last but not least, for generations to come, it provides a well-organized gateway to acquire and expand knowledge and experience. 1.2 This work This work focuses on theory and methods for modeling and analysis of telecommunica- tion frontends and their building blocks. The theory builds on a classification of build- ing blocks according to their behavioral properties. These properties are exploited to 2 There is no shame in using previous experience to make life a little easier. However, it is important to embed this experience within a structured framework. 1.2.1 Main contributions construct methods that render analysis as efficient as possible. Both theory and methods apply to large classes of systems. Their use often extends beyond telecommunications. In summary, this work contributes to a structured approach towards telecommunication system analysis and provides a well-organized gateway to methods that may be of use in capturing system and/or building block behavior. 1.2.1 Main contributions This book reports work on two particular subjects: Linear periodically time-varying (LPTV) systems: LPTV behavior arises when system or circuit behavior is linearized in the neighborhood of a periodic (time-varying) operating point. This is comparable to traditional linear time-invariant (LTI) small- signal analysis where the operating point is constant. LPTV behavior is typically ob- served in systems driven by a large periodic signal, e.g. mixers and phase-locked loops (PLLs). It is characterized by the up- and downconversion of signal content. A first part develops frequency-domain methods that extend traditional time-invariant techniques to cope with LPTV behavior. The starting point is the Harmonic Transfer Matrix (HTM) representation of an LPTV system, a concept borrowed from power electronics and microwave theory. HTMs allow us to handle LPTV systems in a man- ner that is similar to dealing with LTI systems using (Laplace- or frequency-domain) transfer functions. Unfortu