System and method for sending and receiving a digital signal over a radio pathway

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 he(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 he(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 he 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 we,m,i, and σe,m,i, ae,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 C0(t) regardless of the number of states of the modulation,
• wherein the parameters of the frequency pulses he(a(n), t) and impulse response filter C0(t) are optimized to minimize inter-symbol interference of the digital data.