Digital signal coding

Claim 1

A coding apparatus comprising: (i) a convolutional coder having a plurality n of defined states and operable at regular intervals to assume a state which, for any preexisting state, is one of two mutually different states according to the binary value of an input thereto, such that the behaviour of the coder is capable of being represented by a diagram in which each such state is represented by a point and each transition, and its direction between two states or from a state to the same state, is represented by a line whose ends are joined to the point representing those states or that state, said diagram being unchanged when rotated by any multiple of 90 degrees; (ii) mapping means responsive to said coder states to generate in response to each possible pair of consecutive states an assigned one of four signals having relative phases 0, 90, 180 and 270 degrees, the assignment being such that each possible sequence of three consecutive coder states gives rise to a pair of assigned signals having the same signed phase difference as would a pair generated by a corresponding coder state sequence which, in said diagram, occupies a position rotated by 90° from that of said three consecutive coder state sequence; and (iii) input means responsive to a single bit input stream producing said binary input to said convolutional coder to control the state transitions so that one bit value gives rise to a signal of phase difference a or b from the preceding signal and the other bit value gives rise to a signal of phase difference c or d from the preceding signal, where a, b, c and d have different values and said values being in any order 0, 90, 180 and 270 degrees.

Claim 10

A method of transmitting a bit sequence by modulating a carrier to generate in a convolution coder a series of signals each having a phrase and an amplitude, comprising: (a) receiving a single bit input stream; (b) controlling in response to said single bit input stream the convolutional coder having a plurality of defined states, said convolutional coder assuming at regular intervals a state which, for any preexisting state, is one of two mutually different states, such that the behavior of the coder is capable of being represented by a diagram in which each state is represented by a point and each transition, and its direction between two states or from a state to the same state, is represented by a line whose ends are joined to the points or point representing those states or that state, said diagram being unchanged when rotated by any multiple of 90 degrees; and (c) generating said signals in response to said coder states, each possible pair of consecutive states producing an assigned one of four signals having relative phases 0, 90, 180 and 270 degrees, the assignment being such that each possible sequence of three consecutive coder states gives rise to a pair of assigned signals having the same signed phase difference as would a pair generated by a corresponding coder state sequence which, in said diagram, occupies a position rotated by 90° from that of said three consecutive coder state sequence wherein, in said step (b) of controlling said convolutional coder, the state transitions are controlled so that one bit value results in generation of a signal of phase difference a or b from the preceding signal and the other bit value results in generation of signal of phase difference c or d from the preceding signal, where a, b, c and d have different values and said values being in any order 0, 90, 180 and 270 degrees.

Claim 11

A method of transmitting a bit sequence by modulating a carrier to generate in a convolution coder a series of signals each having a phrase and an amplitude, comprising: (a) receiving a single bit input stream; (b) controlling in response to said single bit input stream the convolutional coder having a plurality of defined states, said convolutional coder assuming at regular intervals a state which, for any preexisting state, is one of two mutually different states, such that the behavior of the coder is capable of being represented by a diagram in which each state is represented by a point and each transition, and its direction between two states or from a state to the same state, is represented by a line whose ends are joined to the points or point representing those states or that state, said diagram being unchanged when rotated by any multiple of 90 degrees; and (c) generating said signals in response to said coder states, each possible pair of consecutive states producing an assigned one of four signals having relative phases 0, 90, 180 and 270 degrees, the assignment being such that each possible sequence of three consecutive coder states gives rise to a pair of assigned signals having the same signed phase difference as would a pair generated by a corresponding coder state sequence which, in said diagram, occupies a position rotated by 90° from that of said three consecutive coder state sequence wherein, in said step (b) of controlling said convolutional coder, the state transitions are controlled so that one bit value results in generation of a signal of phase difference a or b from the preceding signal and the other bit value results in generation of signal of phase difference c or d from the preceding signal, where a, b, c and d have different values and said values being in any order 0, 90, 180 and 270 degrees.