Multipath canceller for cancelling a distortion caused to a radio frequency pulse by multipath transmission

A multipath canceller responsive to each distorted pulse in a succession of distorted pulses of a pulse amplitude modulated radio frequency signal received through a plurality of transmission paths comprising a shortest path and other undesired paths for cancelling a distortion to which an original radio frequency pulse of an original pulse shape is subjected before reception as said distorted pulse, said multipath canceller comprising:

• first means responsive to said distorted pulse for producing a distortionless pulse of a distortionless pulse shape which is similar to said original pulse shape;
• and
• second means responsive to said distorted and said distortionless pulses for producing a distortion cancelled pulse which is exempted from said distortion, wherein said second means comprises:
• a cross-correlator responsive to said distorted and said distortionless pulses for producing a cross-correlation coefficient therebetween;
• an autocorrelator responsive to said distortionless pulse for producing an autocorrelation coefficient thereof;
• pulse position estimating means responsive to said cross-correlation and said autocorrelation coefficients for estimating an estimated pulse position which said original radio frequency pulse has when received through said shortest path alone;
• and
• means responsive to said distortionless pulse and said estimated pulse position for producing said distortionless pulse at said estimated pulse position as said distortion cancelled pulse.

A multipath canceller responsive to each distorted pulse in a succession of distorted pulses of a pulse amplitude modulated radio frequency signal received through a plurality of transmission paths comprising a shortest path and other undesired paths for cancelling a distortion to which an original radio frequency pulse of an original pulse shape is subjected before reception as said distorted pulse, said multipath canceller comprising:

• first means responsive to said distorted pulse for producing a distortionless pulse of a distortionless pulse shape which is similar to said original pulse shape;
• second means responsive to said distorted and said distortionless pulses for producing a distortion cancelled pulse which is exempted from said distortion;
• and
• said original radio frequency pulse being each of a first and a second original radio frequency pulse which share said original pulse shape, said distorted pulse being each of a first and a second distorted pulse which result in said pulse amplitude modulated radio frequency signal from said first and said second original radio frequency pulses, respectively, said undesired paths comprising near and distant paths, said distortion comprising a primary and a secondary distortion component, said primary distortion component formed in each of said first and second distorted pulses by a corresponding one of the first and the second original radio frequency pulses received through said near paths, said secondary distortion component formed in said second distorted pulse by the first original radio frequency pulse received through said distant paths, wherein said second means comprises:
• third means responsive to said first distorted and said distortionless pulses for producing said primary distortion component and a first distortion cancelled pulse which corresponds to said first distorted pulse and is exempted from said primary distortion component;
• and
• fourth means responsive to said second distorted and said distortionless pulses and to the primary distortion component produced by said third means for producing a second distortion cancelled pulse which corresponds to said second distorted pulse and is exempted from said primary and said secondary distortion components.

A multipath canceller responsive to a first and a second distorted pulse of a pulse amplitude modulated radio frequency signal received through a plurality of transmission paths comprising a shortest path, near paths, and distant paths for cancelling a distortion to which each of a first and a second original radio frequency pulse of a common original pulse shape is subjected before reception as each of said first and said second distorted pulses, the distortion of each of said first and said second distorted pulses comprising a primary distortion component, the distortion of said second distorted pulse further comprising a secondary distortion component, the primary distortion components of said first and said second distorted pulses being caused by reception through said near paths of said first and said second original radio frequency pulses, respectively, said secondary distortion component being caused by reception of said first original radio frequency pulse through said distant paths, said multipath canceller comprising:

• processing means for processing said first and said second distorted pulses to produce a first and a second processed pulse in response to said first and said second distorted pulses, respectively;
• distortionless pulse producing means responsive to said first processed pulse for producing a distortionless pulse of a distortionless pulse shape which is similar to said common original pulse shape;
• first means responsive to said first processed and said distortionless pulses for producing said primary distortion component and a first distortion cancelled pulse which corresponds to said first processed pulse and is exempted from said primary distortion component;
• and
• second means responsive to said second processed and said distortionless pulses and to the primary distortion component produced by said first means for producing a second distortion cancelled pulse which corresponds to said second processed pulse and is exempted from said primary and said secondary distortion components.

A multipath canceller responsive to each distorted pulse of a pulse amplitude modulated radio frequency signal received through a plurality of transmission paths comprising a shortest path and other undesired paths for cancelling a distortion to which an original radio frequency pulse of an original pulse shape is subjected before reception as said distorted pulse, said distortion comprising a first and a second distortion component which are in an inphase and a quadrature phase relationship relative to the original radio frequency pulse received through said shortest path alone as a distortionless pulse, said original pulse shape having instantaneous amplitudes which are distributed substantially according to Gaussian distribution, said multipath canceller comprising:

• first power calculating means responsive to said radio frequency signal for calculating an instantaneous electric power of said signal as a first electric power;
• subtracting means for subtracting an input electric power from said first electric power to produce a difference electric power;
• pulse estimating means responsive to said difference electric power for generating an estimated pulse;
• component estimating means responsive to said estimated pulse for estimating a first and a second estimated component which correspond to said first and said second distortion components, respectively;
• second power calculating means responsive to said estimated pulse and said first and said second estimated components for calculating an instantaneous electric power of a combination of said first and said second distortion components as a second electric power;
• means for delivering said second electric power to said subtractor as said input electric power;
• and
• training means responsive to said estimated pulse and coupled to said component estimating means for training said first and said second estimated components so as to make said estimated pulse converge to said distortionless pulse.