Noise is present in every system. Phase noise, in particular, commonly found in oscillators and phase-locked loops, can degrade the performance of a system. Phase noise in the oscillator of a wireless communication system degrades the receiver’s sensitivity in reciprocal mixing conditions. Phase noise in a telecommunications system causes time jitter in the signal chain. Although engineers usually try to minimize phase noise, sometimes for test purposes they degrade the phase noise intentionally. The deliberate introduction of phase noise aids in testing a system’s tolerance for phase noise or jitter. Consequently, signals with an adjustable level of phase noise are useful for testing purposes.


This application note illustrates techniques for producing phase noise and techniques for producing noise voltage.