Method and apparatus for echo cancellation in digital communications using an echo cancellation reference signal

An equalizer comprising:

• an extraction circuit for extracting a copy of an echo cancellation reference signal from a digital data stream transmitted over a transmission path;
• a microprocessor coupled to the extraction circuit for calculating filter coefficients from the extracted copy of the echo cancellation reference signal;
• and
• a filter receiving the digital data stream at an input thereof and coupled to the microprocessor for receiving the filter coefficients and substantially canceling echo interference from the digital data stream using the filter coefficients;
• wherein the echo cancellation reference signal is non-cyclic, has a substantially flat frequency response within the bandwidth of the transmission path, has a large plurality of amplitude peaks over a time interval, and has proportionally shorter tails relative to the large plurality of amplitude peaks,
• wherein the echo cancellation reference signal is of a class of signals substantially defined by:
• f ⁢ ( t ) = 1 2 ⁢ π ⁢ ∫ 0 Ω ⁢ [ A ⁢ ⁢ cos ⁢ ( b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω + 1 2 ⁢ π ⁢ ∫ - Ω 0 ⁢ [ A ⁢ ⁢ cos ⁢ ( - b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( - b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω
• A, b and Ω being real numbers, wherein A=0.707×8.6×10−6 volts;
• b=0.9×10−12 sec2/radian;
• and Ω=5.38×2π×106 radian/sec.

An equalizer for substantially eliminating echoes occurring during transmission of a digital data stream comprising a plurality of field syncs over a transmission path, a plurality of segments of symbol spaces being between successive ones of the field syncs, and a plurality of echo cancellation reference signals added between the field syncs, comprising:

• means for receiving the digital data stream after transmission;
• means for extracting copies of the echo cancellation reference signals from the received digital data stream;
• means for calculating filter coefficients from the extracted copies of the echo cancellation reference signals;
• and
• means for substantially canceling echo interference from the received digital data stream using the filter coefficients;
• wherein the echo cancellation reference signals are non-cyclic, have a substantially flat frequency response within the bandwidth of the transmission path, have a large plurality of amplitude peaks over a time interval, and have proportionally shorter tails relative to the large plurality of amplitude peaks, and includes residual channel information;
• wherein the echo cancellation reference signals are of a class of signals substantially defined by:
• f ⁢ ( t ) = 1 2 ⁢ π ⁢ ∫ 0 Ω ⁢ [ A ⁢ ⁢ cos ⁢ ( b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω + 1 2 ⁢ π ⁢ ∫ - Ω 0 ⁢ [ A ⁢ ⁢ cos ⁢ ( - b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( - b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω
• A, b and Ω being real numbers.

An apparatus for substantially eliminating echoes occurring during transmission of a digital data stream comprising a plurality of field syncs over a transmission path, a plurality of segments of symbol spaces being between successive ones of the field syncs, and a plurality of echo cancellation reference signals between the field syncs, comprising:

• means for receiving the digital data stream after transmission;
• means for extracting copies of the echo cancellation reference signals from the received digital data stream;
• means for calculating filter coefficients from the extracted copies of the echo cancellation reference signals;
• and
• means for substantially canceling echo interference from the received digital data stream using the filter coefficients;
• wherein the echo cancellation reference signals are non-cyclic, have a substantially flat frequency response within the bandwidth of the transmission path, have a large plurality of amplitude peaks over a time interval, and have proportionally shorter tails relative to the large plurality of amplitude peaks,
• wherein the echo cancellation reference signals are of a class of signals substantially defined by:
• f ⁢ ( t ) = 1 2 ⁢ π ⁢ ∫ 0 Ω ⁢ [ A ⁢ ⁢ cos ⁢ ( b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω + 1 2 ⁢ π ⁢ ∫ - Ω 0 ⁢ [ A ⁢ ⁢ cos ⁢ ( - b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( - b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω
• A, b and Ω being real numbers, wherein A=0.707×8.6×10−6 volts;
• b=0.9×10−12 sec2/radian;
• and Ω=5.38×2π×106 radian/sec.

A method for substantially eliminating echoes occurring during transmission of a digital data stream before providing said digital data stream to a vestigial side band (VSB) receiver, said digital data stream comprising a plurality of field syncs over a transmission path, a plurality of segments of symbol spaces being between successive ones of the field syncs, and a plurality of echo cancellation reference signals between the field syncs, comprising:

• receiving the digital data stream after transmission;
• extracting copies of the echo cancellation reference signals from the received digital data stream;
• calculating filter coefficients from the extracted copies of the echo cancellation reference signals;
• and
• substantially canceling echo interference from the received digital data stream using the filter coefficients;
• wherein the echo cancellation reference signals are non-cyclic, have a substantially flat frequency response within the bandwidth of the transmission path, have a large plurality of amplitude peaks over a time interval, and have proportionally shorter tails relative to the large plurality of amplitude peaks;
• wherein the echo cancellation reference signals are of a class of signals substantially defined by:
• f ⁢ ( t ) = 1 2 ⁢ π ⁢ ∫ 0 Ω ⁢ [ A ⁢ ⁢ cos ⁢ ( b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω + 1 2 ⁢ π ⁢ ∫ - Ω 0 ⁢ [ A ⁢ ⁢ cos ⁢ ( - b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( - b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω
• A, b and Ω being real numbers.

A method for substantially eliminating echoes occurring during transmission of a digital data stream comprising a plurality of field syncs over a transmission path, a plurality of segments of symbol spaces being between successive ones of the field syncs, and a plurality of echo cancellation reference signals between the field syncs, comprising:

• receiving the digital data stream after transmission;
• extracting copies of the echo cancellation reference signals from the received digital data stream;
• calculating filter coefficients from the extracted copies of the echo cancellation reference signals;
• and
• substantially canceling echo interference from the received digital data stream using the filter coefficients;
• wherein the echo cancellation reference signals are non-cyclic, have a substantially flat frequency response within the bandwidth of the transmission path, have a large plurality of amplitude peaks over a time interval, and have proportionally shorter tails relative to the large plurality of amplitude peaks;
• wherein the echo cancellation reference signals are of a class of signals substantially defined by:
• f ⁢ ( t ) = 1 2 ⁢ π ⁢ ∫ 0 Ω ⁢ [ A ⁢ ⁢ cos ⁢ ( b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω + 1 2 ⁢ π ⁢ ∫ - Ω 0 ⁢ [ A ⁢ ⁢ cos ⁢ ( - b ⁢ ⁢ ω 2 ) + j ⁢ ⁢ A ⁢ ⁢ sin ⁢ ( - b ⁢ ⁢ ω 2 ) ] ⁢ ⅇ jω ⁢ ⁢ t ⁢ ⁢ ⅆ ω
• A, b and Ω being real numbers, wherein A=0.707×8.6×10−6 volts;
• b=0.9×10−12 sec2/radian;
• and Ω=5.38×2π×106 radian/sec.