Predict NPR for RF modules using system simulation

INCREASING demand for mobile and satellite communications and the related n eed for multiple-channel equipment require system designers to know the int ermodulation distortion (IMD) of devices and subsystems that they intend to use. IMD occurs when mixing two or more carriers and is caused by the nonl inearities of the active devices used in the circuits. Evaluating IMD invol ves the measurement of noise-power ratio (NPR), which is defined as the rat io of the averaged power of the multiple carriers to the averaged IM power falling into a narrow frequency notch.'s The first NPR measurement was perf ormed more than 30 years ago through an analog method using a diode-based n oise generator as the stimulus and a spectrum analyzer for analysis. Recent ly, a digital method was proposed using digital synthesis and digital filte ring to generate the noise stimulus, together with digital signal analysis. (4,5) But these two measurement methods require very specific equipment tha t is rarely at the disposal of every system designer.