Patent ID: 7561103

Claim:
A method of generating a modulated navigation signal ( 7 ) which is intended to be used to position a downlink receiver ( 6 ), comprising multiple pseudorandom navigation codes of chip rhythms greater than 0.5 MHz, modulated onto a carrier of frequency fp greater than 500 MHz, wherein four distinct and independent pseudorandom navigation codes C 1 , C 2 , C 1 ′, C 2 ′ are modulated onto the carrier according to an 8-PSK modulation of constant amplitude with a modulation frequency fM such that: 8fc≦fM where fc=Max(fci), and fci designates the chip rhythms fc 1 , fc 1 ′, fc 2 , fc 2 ′ of the navigation codes C 1 , C 2 , C 1 ′, C 2 ′, each fci value being such that fM=Ni.fci, Ni being an integer greater than or equal to 8, two navigation codes C 1 , C 1 ′ being quadrature modulated at frequency f 1 =fp−fM/8, and two other navigation codes C 2 , C 2 ′ being quadrature modulated at frequency f 2 =fp+fM/8, and the modulated navigation signal presenting a constant envelope, wherein one of i) 8-PSK modulation of symmetrical constant amplitude in the Fresnel plan is used, and ii) 8-PSK modulation of asymmetrical constant amplitude in the Fresnel plan is used.