Demodulation of 16-QAM signals using RF direct orthogonal phase under-sampling technique

We have developed new digital receiver architecture that can demodulate a higher-order modulation signal, such as a 16-QAM signal, without losing any information even if an RF carrier is sampled at a frequency much lower than the carrier frequency. The sampling frequency is set so that a phase relationship of the sampling point of an alias signal generated by sampling a carrier at a sampling frequency lower than that of a carrier coincides with a phase relationship of the sampling point of the carrier. We call this sampling ¿RF direct orthogonal phase under-sampling¿. Using this sampling, both I-channel and Q-channel information can be obtained directly. The only drawback of the sampling is it must be precisely timed so that it is synchronized with the input RF carrier. Therefore, we have developed a new synchronization technique between samplings and RF carrier modulated with 16-QAM. To prove the validity of our technique, we have demonstrated demodulating the 16-QAM signal by using receiver simulations on Matlab.