Method of operation of receiver combiner for spatial diversity digital communications

Abstract

Apparatus for and method of processing received signals for use with multiple antenna spatial diversity receivers used in a digital communications system. The receiver has received signal phase modulator apparatus for each diversity received signal. The phase modulator provides a two state phase perturbation of zero or pi radians, based on the carrier frequency, which is switched to modulate the phase of the received signal for a fifty percent duty cycle over a symbol period.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:  
     
         1 . Received signal processing apparatus for use with a spatial diversity receiver having a first receiving element producing a received signal and at least one physically separated diversity receiving element producing a received diversity signal comprising: 
 phase perturbation means for each received diversity signal, to modulate the phase of the received diversity signal selectively by a predetermined phase adjustment in response to a control signal, producing a phase perturbed output signal;    switching control means to produce a control signal for each phase perturbation means; and    summing means to sum the received signal with all said phase perturbed output signals to produce a combined output signal.    
     
     
         2 . A receiver as claimed in    claim 1    wherein said switching control means produces control signals that are periodic over a symbol period.  
     
     
         3 . A receiver as claimed in    claim 1    wherein said switching control means produces mutually orthogonal control signals.  
     
     
         4 . A receiver as claimed in claims  2  wherein said switching control means produces control signals selected from the family of functions called Walsh functions.  
     
     
         5 . A receiver as claimed in    claim 2    wherein said predetermined phase adjustment is substantially one-half the carrier cycle.  
     
     
         6 . A receiver as claimed in    claim 2    wherein said phase perturbation means comprises a switched delay line path.  
     
     
         7 . A receiver as claimed in    claim 2    wherein said phase perturbation means comprises a switched negative unity gain amplifier.  
     
     
         8 . Received signal processing apparatus for use with a spatial diversity receiver having at least two physically separated receiving elements each producing a received signal comprising: 
 phase perturbation means for each receiving element to modulate the phase of the received signal selectively by a predetermined phase adjustment in response to a control signal, producing a phase perturbed output signal;    switching control means to produce a control signal for each phase perturbation means; and    summing means to sum the outputs from all said phase perturbation means to produce a combined signal output.    
     
     
         9 . A receiver as claimed in    claim 8    wherein said switching control means produces control outputs that are periodic over a symbol period.  
     
     
         10 . A receiver as claimed in    claim 9    wherein said switching control means produces mutually orthogonal control outputs.  
     
     
         11 . A receiver as claimed in claims  10  wherein said switching control means produces control outputs selected from the family of functions called Walsh functions.  
     
     
         12 . A receiver as claimed in claims  8  wherein said predetermined phase adjustment is substantially one-half the carrier cycle.  
     
     
         13 . A receiver as claimed in    claim 8    wherein said phase perturbation means comprises a switched delay line path.  
     
     
         14 . A receiver as claimed in    claim 8    wherein said phase perturbation means comprises a negative unity gain amplifier.  
     
     
         15 . A method for processing the signals received by a diversity receiver having a first receiving element and at least-one diversity receiving element comprising the steps of: 
 periodically perturbing the phase by a predetermined amount of each received signal produced by a diversity receiving element over a symbol period; and    combining all received signals    
     
     
         16 . The method of    claim 15    wherein the predetermined amount is substantially one-half of the carrier frequency.  
     
     
         17 . The method of    claim 15    wherein said periodic perturbation has a duty cycle substantially equal to fifty percent of the symbol period.  
     
     
         18 . The method of    claim 15    wherein each said periodic perturbation is mutually orthogonal to all others.  
     
     
         19 . A method for processing the signals received by a diversity receiver having at least two receiving elements comprising the steps of: 
 periodically perturbing each received signal phase by a predetermined amount over a symbol period; and    combining all received signals.    
     
     
         20 . The method of    claim 15    wherein the predetermined amount is substantially one-half of the carrier frequency.  
     
     
         21 . The method of    claim 19    wherein said periodic perturbation has a duty cycle substantially equal to fifty percent of the symbol period.  
     
     
         22 . The method of    claim 20    wherein each said periodic perturbation is mutually orthogonal to all others.