a low phase noise frequency multiplier is disclosed for multiplying a sine wave obtained from a low phase noise crystal oscillator to higher frequencies than can be directly obtained from a crystal oscillator . the multiplication occurs without the ordinary increase in phase noise . the multiplier , when tripling the frequency contains a low phase noise frequency doubler . the double and triple frequency terms in the tripler are synthesized from two orthogonally related derivatives of the same wave , which are then multiplied in a double balanced mixer . the process reinforces the desired harmonics while not reinforcing the short term random phase noise , and produces a substantial improvement in the single sideband phase noise ratio over conventional frequency multipliers .