Single chip VLSI implementation of a digital receiver employing orthogonal frequency division multiplexing

A receiver for receiving modulated symbols that have an active interval and a guard interval separated by a boundary, the receiver having a guard interval detector, said receiver comprising:

• a measurement block;
• a delay block having a delay approximately equal to the active interval;
• a subtractor generating a difference sample corresponding to the difference in measured signal strength between a first symbol and a second delayed symbol;
• a storage block storing N difference samples;
• and
• a processing block applying a mathematical operation to the stored N difference samples.

A method of processing a modulated multi-carrier signal, said method comprising the step of:

• receiving digitized data representing modulated multi-carrier symbols having an active interval and a guard interval;
• passing the received data through an I/Q demodulator;
• synchronizing an FFT window to the active interval;
• performing an FFT on the active interval;
• estimating the channel characteristics;
• and
• producing an output including unmodulated digitized video data corresponding to the received modulated multi-carrier signal, said steps of passing, synchronizing, performing, applying, estimating, and producing being performed within a single ship.

A method for synchronizing an FFT window to a modulated multi-carrier signal having symbols, said method comprising the steps of:

• choosing a pair of blocks of symbols;
• measuring a characteristic of a first symbol of a first block of the pair;
• measuring a characteristic of a first symbol of a second block of the pair;
• determining the difference between the first symbol of the first block and the first symbol of the second block;
• repeating the measuring steps and the determination step for successive symbols in each block;
• and
• applying a statistical test to the determined differences between the first and second blocks.

A method for synchronizing an FFT window to a modulated multi-carrier signal having symbols, said method comprising the steps of:

• receiving a digital signal corresponding to the multi-carrier signal;
• producing a delayed signal by delaying the received signal by L symbols;
• determining the difference between the delayed signal and the received signal and producing a difference signal;
• delaying the difference signal by N symbols;
• inputting the difference signal and the delayed difference signal into an adder/subtractor;
• delaying the output of the adder/subtractor;
• and
• feeding back the delayed output of the adder/subtractor as an additional input into the adder/subtractor.

A method for synchronizing an FFT window to a modulated multi-carrier signal having symbols, said method comprising the steps of:

• receiving a digital signal corresponding to the multi-carrier signal;
• delaying the digital signal producing a delayed signal;
• correlating the delayed signal to the received signal;
• and
• accessing data in a lookup table stored in memory as a function of the correlating.

A method for synchronizing an FFT window to a modulated multi-carrier signal having symbols, said method comprising the steps of:

• receiving a digital signal corresponding to the multi-carrier signal;
• measuring the signal to noise ratio of the digital signal;
• and
• choosing a selected synchronization technique from a plurality of synchronization techniques, said choosing step performed as a function of the measure of signal to noise ratio.