Book excerpt: Broadband voltage-controlled oscillators are critical to the design of millimeter wave frequency synthesizers. This book proposes a design technique that can be used to significantly extend the achievable frequency span of an oscillator. A dual-band oscillator topology is described that can be configured to operate in one of two modes, by an electrical reconfiguration of the negative resistance core around the resonant tank, without switching passive elements within the tank itself. The configuration helps to minimize the difference in phase noise performance between the two modes, while achieving a wide tuning range. This book includes five chapters and through these chapters the necessary information for designing millimeter wave frequency synthesizers are provided for the readers.