Abstract: A signal generator for high level low noise signals in which the preferred embodiment of the invention utilizes the output signal of a low noise crystal oscillator as a fundamental reference signal. The fundamental reference signal is multiplied to generate a series of coherent reference signals. Additionally, one of the coherent reference signals is coupled as an input signal to a divide circuit to generate at the output of the divide circuit a plurality of coherent low frequency reference signals. The coherent reference signals and the low frequency coherent reference signals are utilized by a synthesizer to generate a plurality of coherent signals having a frequency determined by the synthesizer. The output signal of the synthesizer is combined with one or more of the reference signals to generate the microwave output signal which is stepped from a minimum to a maximum value in equal increments.