Looking at a PSK modulated signal, my oscilloscope reveals ripples in the envelope of the signal. What is causing this and how can I correct it?
If the chip rate is high (>5 MHz) and the ripple is about +/- 5% or less, this is to be expected. The distortion is a result of the non-linearity of the code input port of the mixer. While this distortion is of little consequence in many situations, in others it may be unacceptable. Refer to the FAQ on code imbalance for more information regarding the consequence of this distortion, and for a technique to correct it. If the ripple is greater than +/-5%, or occurs even at low chip rates (<2 MHz), you may be connecting the generator to the mixer incorrectly. Refer to the FAQ on mixer connections for instructions on driving a double-balanced mixer.
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