System and method for delivery of video, content on demand and IP packets
A method for processing a sinusoidal carrier frequency signal includes generating a series of samples by sampling the carrier frequency signal at a system sampling rate until a wrap up sample is yielded. The wrap up sample position is within a predetermined distance of an end of a cycle of the carrier frequency signal and, the series of samples constitute a digital representation of the cycle of the carrier frequency signal. A position of each of the series of samples is adjusted by an amount proportional to the wrap up sample position from the cycle end and the adjusted samples are stored in memory.
1. A method for processing a plurality of sinusoidal carrier signals at different frequencies for subsequent use in a data transmission system having a system sampling rate and a jitter tolerance, comprising:
for each different frequency:
generating a series of samples by sampling a respective one of the plurality of sinusoidal carrier signals at the system sampling rate until a wrap up sample is yielded, said wrap up sample position being within a predetermined distance of an end of a cycle of said respective carrier signal, wherein the series of samples comprise a digital representation of at least one cycle of the respective carrier signal and said predetermined distance is representative of the jitter tolerance;
adjusting a position of each of said series of samples by an amount proportional to said wrap up sample position from said cycle end; and
storing said adjusted samples in memory.
2. The method of claim 1 , wherein said generating step further comprises first sampling the respective one of the plurality of carrier signals at the system sampling rate until an intermediate sample is yielded, said intermediate sample being within a first predetermined distance of a maximum amplitude of the cycle of said carrier frequency signal.
3. The method of claim 1 , wherein said proportional amount is said wrap up sample position from said cycle end divided by a number of samples in said series.
4. The method of claim 1 , wherein said wrap up sample position from said cycle end is an angular displacement.
5. The method of claim 4 , wherein said angular displacement is measured in Hertz.
6. The method of claim 2 , wherein said first predetermined distance is one degree.
7. The method of claim 5 , wherein said predetermined distance is 22 kHz.
8. The method of claim 1 , wherein the data transmission system is a cable TV transmission system transmitting each of a plurality of data streams using a respective one of a plurality of channels, one of each of said channels associated with a respective one of said frequencies of said plurality of sinusoidal carrier signals and further comprising modulating each of said data streams onto its respective channel using QAM, a respective series of said stored adjusted samples and direct digital synthesis (DDS) and converting said modulated data streams into analog signals using a digital to analog converter.