Signal structures for double side band-quadrature carrier modulation

Abstract

Double side band-quadrature carrier modulation signal points as mapped on the complex plane are drawn from an alphabet consisting of at least 8 points, and are set up in concentric rings each rotated by 45° with respect to adjacent rings. Differential encoding is shown encoding the phase components of the transmitted signals.

We claim: 
     
       1. A double side band-quadrature carrier modulation system comprising input means for receiving a sequence of symbols a k  at a rate 1/T per second.   coding means connected to said input means for providing from said symbbols a sequence of complex valued signal points d k  drawn from an alphabet comprising M points arranged in a multiplicity of concentric rings in the complex plane including an innermost ring having four equally spaced points and a plurality of additional rings each having four equally spaced points, each said ring being rotated by 45° with respect to adjacent said rings, and   modulating means connected to said coding means for providing from said signal points a signal in the form ##EQU3## where h(t-kT) represents an impulse response, w c  represents a carrier frequency, t represents time, j equals √-1, and k is the index of d k  and a k  wherein said coding means includes means for effectively providing said signal points arranged in at least four concentric rings in the complex plane. .[.   
     
     
       2.  The system of claim 1 wherein said coding means includes means for effectively providing said signal points arranged in at least four concentric rings in the complex plane..]. 
     
     
       3. The system of claim .[.2.]. .Iadd.1 .Iaddend.wherein said coding means includes means for causing the innermost four said rings to have radii in the ratio √2:3:3√2:5. 
     
     
       4. The system of claim 1 wherein said coding means includes means for causing the phase component of each d k  to depend upon a k  and upon the phase component of d.sub.(k-1). 
     
     
       5. The system of claim 1 wherein said coding means includes means for causing each said d k  to have integer valued coordinates in the complex plane. 
     
     
       6. A double side band-quadrature carrier modulation system comprising input means for receiving a sequence of symbols a k  at a rate 1/T per second,   coding means connected to said input means for providing from said symbols a sequence of complex valued signal points d k  drawn from an alphabet comprising M points arranged in a multiplicity of concentric rings in the complex plane including an innermost ring having four equally spaced points and .[.a plurality of.]. .Iadd.at least three .Iaddend.additional rings having four equally spaced points, each said ring being rotated by 45° with respect to adjacent said rings, and   filtering means connected to said coding means for providing from said signal points the real and imaginary parts of a complex valued baseband signal in the form ##EQU4## and modulating means connected to said filtering means for providing from said baseband signal a passband signal in the form ##EQU5## where h(t-kT) represents an impulse response, w c  represents a carrier frequency, t represents time, j equals √-1, and k is the index of d k  and a k .   
     
     
       7. A double side band-quadrature carrier modulation method comprising receiving a sequence of symbols a k  at a rate 1/T per second   providing from said symbols a sequence of complex valued signal points d k  drawn from an alphabet comprising M points arranged in a multiplicity of concentric rings in the complex plane including an innermost ring having four equally spaced points and .[.a plurality of.]. .Iadd.at least three .Iaddend.additional rings each having four equally spaced points, each said ring being rotated by 45° with respect to adjacent said rings, and   providing from said signal points a signal in the form ##EQU6## where h(t-kT) represents an impulse response, w c  represents a carrier frequency, t represents time, j equals √-1, and k is the index of d k  and a k .   
     
     
       8. A double side band-quadrature carrier modulation method comprising receiving a sequence of symbols a k  at a rate 1/T per second,   providing from said symbols a sequence of complex valued signal points d k  drawn from an alphabet comprising M points arranged in a multiplicity of concentric rings in the complex plane including an innermost ring having four equally spaced points and .[.a plurality of.]. .Iadd.at least three .Iaddend.additional rings having four equally spaced points, each said ring being rotated by 45° with respect to adjacent said rings, and   providing from said signal points the real and imaginary parts of a complex valued baseband signal in the form ##EQU7## and providing from said baseband signal a passband signal in the form ##EQU8## where h(t-kT) represents an impulse response, w c  represents a carrier frequency, t represents time, j equals √-1, and k is the index of d k  and a k  wherein said coding means includes means for effectively providing said signal points arranged in at least four concentric rings in the complex plane.  .Iadd.   
     
     
       9.  The system of claim 1 wherein said coding means includes means for providing signal points from an alphabet of sixteen points arranged in exactly four concentric rings in the complex plane. .Iaddend.