密码 123456 The Designer s Guide to High-Purity Oscillators Oscillatory systems exist everywhere, from our planet circulating around the sun with a period of 365.2422 days in an average tropical year; to a pendulum in an antique clock ticking every second; to the vibrations of a quartz crystal in a wrist watch. The study of oscillators was initiated centuries ago in basic mechanics. Some of the very complicated problems of injection locking in coupled oscillators were experimentally verified in the century by Huygens. He used c oupled pendulums using elastic threads to move energy from one pendulum to another. Oscillators belong to a class of systems known as autonomous systems. As opposed to driven systems, oscillators possess the unique feature that they do not need a time varying input to produce a time varying output. The periodicity and amplitude of the produced oscillation are regulated by the system’s energy balance rather than an external input. This unique property makes the study of oscillators both complicated and fascinating. In the field of electrical circuits, the study of oscillators was pioneered by radio scientists and particularly flourished during World War II. Some ingenious circuit implementations were devised to produce the best oscillators possible. Along with the circuit implementations, came the formal mathematical analysis. One of the earliest models is due to Van Der Pol in the 1920s. Rigorous nonlinear analysis was carried out throughout the 1920’s until today. Despite the long history, most of the literature, until recently, focused on two questions: ‘what is the precise amplitude of oscillation?’ and ‘what is the exact period of oscillation?’