Spiral transmission-line baluns for RF multichip module packages

We describe a design method and lumped model for a circular spiral transmis sion-line balun, All lumped values are extracted from the geometric paramet ers of the balun. From simulation, the design parameters with well predicte d characteristics are defined, The balun is fabricated using multi-chip mod ule processing technology, which is suitable for integration in RF packages . Measurements show a wide bandwidth of 1.5-4.1 GHz and excellent balanced outputs. Amplitude imbalance less than 0.5 dB and phase imbalance less than 4 degrees are achieved. The simulation results are compared with the measu rement. The model captures all important properties of the balun with reaso nably high accuracy.