Patent ID: 8804868

Claim:
A constant-amplitude and continuous-phase modulation method for modulating digital data and for demodulating said modulated digital data, said digital data being in the form of symbols having M number of states, where M is an integer greater than 2, the method comprising: recovering the symbols a(n) of the digital data to be transmitted, the symbols a(n) of the digital data being recovered periodically at a constant time interval T; associating, with each symbol a(n), a frequency pulse denoted h e (a(n)) having a frequency pulse of length L T, where L is an integer greater than or equal to 1, and having a form dependent on the value of a(n); weighting the frequency pulse h e (a(n), t) by a total phase variation associated with a(n), the total phase variation being in the form π(2a(n) −(M−1))/M, where a(n) is an integer less than or equal to M−1, and for a symbol of value m, where m is less than M, said function h e having a form corresponding to a combination of 2 K +1 individual pulses: h e ⁡ ( m , t ) = ∑ i = 1 K ⁢ ⁢ w e ⁡ ( m , i ) ⁢ ( g ⁡ ( + a e , m , i , σ e , m , i , t ) + g ⁡ ( m , - a e , m , i , σ e , m , i , t ) ) + ( 1 - 2 ⁢ ∑ i = 1 K ⁢ ⁢ w e ⁡ ( m , i ) ) ⁢ g ⁡ ( 0 , σ e , m , 0 , t ) where the function g is a continuous function of standard deviation σ and optimized weighting coefficients, where w e,m,i , and σ e,m,i , a e,m,i are the symbol and a number of successive derivatives of the function g to limit the spectral width of the digital data sent, a is an integral equal to 1, K is the degree of freedom associated with the weight w(i), and t is a given instant; applying a sum of successive weighted pulses to an input of a voltage-controlled oscillator to generate the modulated digital data to be sent; and filtering, on reception, the received modulated digital data by a single impulse response filter C 0 (t) regardless of the number of states of the modulation, wherein the parameters of the frequency pulses h e (a(n), t) and impulse response filter C 0 (t) are optimized to minimize inter-symbol interference of the digital data.