A technique utilizing a composite magnetic series circuit is described wherein the flux density of unsaturated microwave ferrite is maintained constant in spite of large changes in microwave ferrite saturation magnetization, coercive force, and hysteresis loop shape. The composite circuit consists of a driver, a flux limiter, and a microwave ferrite. The driver supplies the necessary mmf to maintain constant flux level in the circuit throughout the temperature range. The flux limiter, a particularly stable ferrite material, establishes the constant flux level. The driver and flux limiter may lie outside the microwave region and may in consequence possess indifferent microwave properties. A simple design procedure is described for determining the driver and flux limiter dimensions. Special attention is given to the effects of air gaps and leakage fluxes which tend to reduce the effectiveness of the technique. A remanence phase shifter is described which suffers a 16% loss of phase shift as a result of an 80°C rise of temperature. By the application of composite circuit techniques, the temperature sensitivity was reduced to less than 2½% over the same temperature range.