Method, system, and apparatus for blind equalization of BPSK signals
AssigneeInfinera Corporation
InventorsDavid J. Krause, Han Henry Sun, John D. McNicol
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Abstract
A system, method, and apparatus is disclosed for enabling a constant modulus algorithm (CMA) to be reliably used for blind equalization training of an equalizer. According to one embodiment, received signals in a binary phase shift keying (BPSK) format are converted to a quadrature phase shift keying (QPSK) format, to which CMA processing can be reliably applied for equalization. According to another aspect of this embodiment, the equalized QPSK signals are rotated to convert the signals to an equalized BPSK format for output.
Claims23
An apparatus, comprising:
- a finite impulse response (FIR) filter circuit configured to successively supply a plurality of symbols;
- a calculation circuit configured to provide a plurality of coefficients to the FIR filter circuit, the calculation circuit calculating the plurality of coefficients in accordance with a Constant Modulus Algorithm (CMA) and in response to first and second inputs to the calculation circuit, the first input including a first group of the plurality of symbols, and the second input being a plurality of sums;
- and
- an adder circuit configured to supply the plurality of sums to the calculation circuit, the adder circuit generating the plurality of sums by adding each kth symbol of a second group of the plurality of symbols to a product of each (k−1)th symbol times a number, where k is an integer greater than or equal to 2 and greater than or equal to n, and n is a number of symbols in the second group of the plurality of symbols.
A method comprising:
- successively supplying each of a plurality of symbols from a finite impulse response (FIR) filter;
- calculating a plurality of coefficients in accordance with a Constant Modulus Algorithm (CMA) and in response to first and second inputs, the first input including a first group of the first plurality of symbols, and the second input being a plurality of sums;
- and
- generating the plurality of sums by adding each kth symbol of a second group of the plurality of symbols to a product of each (k−1)th symbol times a number, where k is an integer greater than or equal to 2 and greater than or equal to n, and n is a number of symbols in the second group of the plurality of symbols.
A method in accordance with 10, wherein the plurality of coefficients is a first plurality of coefficients, the calculating including
- determining a second plurality of coefficients based on the first input;
- determining a third plurality of coefficients based on the second input;
- and
- adding the second and third pluralities of coefficients to provide the first plurality of coefficients.
A system, comprising:
- a transmitter configured to supply an optical signal;
- a receiver configured to receive the optical signal, the receiver including a photodiode that converts the optical signal to an electrical signal;
- an analog-to-digital converter circuit configured to receive the electrical signal and supply a first plurality of symbols;
- a finite impulse response (FIR) filter circuit configured to successively supply a second plurality of symbols based on the first plurality of symbols;
- a calculation circuit configured to provide a plurality of coefficients to the FIR filter circuit, the calculation circuit calculating the plurality of coefficients in accordance with a Constant Modulus Algorithm (CMA) and in response to first and second inputs to the calculation circuit, the first input including a first group of the second plurality of symbols, and the second input being a plurality of sums;
- and
- an adder circuit configured to supply the plurality of sums to the calculation circuit, the adder circuit generating the plurality of sums by adding each kth symbol of a second group of the second plurality of symbols to the product of each (k−1)th symbol times a number, where k is an integer greater than or equal to 2 and greater than or equal to n, and n is a number of symbols in the second group of the second plurality of symbols.
Dependencies are inferred from the claim text.