Carrier recovery for use in an ultra-wideband communication system

Abstract

In an ultra-wideband (“UWB”) receiver, a received UWB signal is periodically digitized as a series of ternary samples. During a carrier acquisition mode, the samples are continuously correlated with a predetermined preamble sequence to develop a correlation value. When the value exceeds a predetermined threshold, indicating that the preamble sequence is being received, estimates of the channel impulse response (“CIR”) are developed. When a start-of-frame delimiter (“SFD”) is detected, the best CIR estimate is provided to a channel matched filter (“CMF”). During a data recovery mode, the CMF filters channel-injected noise from the sample stream. Both carrier phase errors and data timing errors are continuously detected and corrected during both the carrier acquisition and data recovery modes of operation.

What we claim is: 
     
         1 . A method for use in an ultra-wideband (UWB) communication system in which a modulated carrier signal is transmitted via a transmission channel having an impulse response, the method comprising the steps of:
 1.1. sequentially developing a plurality of complex estimates of said impulse response;   1.2. developing an accumulated estimate of said impulse response as a function of a first set of said estimates;   1.3. correlating with said accumulated estimate a second set of said estimates;   1.4. developing an estimated peak of said correlation, said peak corresponding to a selected on-time estimate in said second set of estimates;   1.5. developing a timing phase error as a function of said on-time estimate, a selected early estimate in said second set of estimates preceding said on-time estimate, and a selected late estimate in said second set of estimates following said on-time estimate.   
     
     
         2 . The method of  claim 1  wherein the early estimate comprises the estimate in said second set immediately preceding said on-time estimate. 
     
     
         3 . The method of  claim 1  wherein the late estimate comprises the estimate in said second set immediately following said on-time estimate. 
     
     
         4 . The method of  claim 1  further characterized as comprising the step of:
 1.6. resampling by said timing phase error said estimates following said second set of estimates. 
 
     
     
         5 . Apparatus for use in an ultra-wideband (UWB) communication system in which a modulated carrier signal is transmitted via a transmission channel, the apparatus configured to perform the method according to  claim 1 . 
     
     
         6 . A method for use in an ultra-wideband (UWB) communication system in which a modulated carrier signal is transmitted via a transmission channel having an impulse response, the method comprising the steps of:
 1.1. developing a first complex estimate of said impulse response;   1.2. filtering the carrier signal as a function of the first complex estimate to develop a filtered carrier signal;   1.3. despreading the filtered carrier signal to develop a set of timing error metrics comprising an early metric, an on-time metric and a late metric; and   1.4. developing a timing phase error as a function of at least a selected one of said metrics.   
     
     
         7 . The method of  claim 6  further characterized as comprising the step of:
 1.5. resampling by said timing phase error said filtered carrier signal. 
 
     
     
         8 . Apparatus for use in an ultra-wideband (UWB) communication system in which a modulated carrier signal is transmitted via a transmission channel, the apparatus configured to perform the method according to  claim 6 . 
     
     
         9 . A method for use in an ultra-wideband (UWB) communication system in which a modulated carrier signal is transmitted via a transmission channel having an impulse response, the method comprising the steps of:
 1.0. in a carrier acquisition mode of operation:
 1.1. sequentially developing a plurality of complex estimates of said impulse response; 
 1.2. developing an accumulated estimate of said impulse response as a function of a selected first set of said estimates; 
 1.3. correlating with said accumulated estimate a selected second set of said estimates; 
 1.4. developing an estimated peak of said correlation, said peak corresponding to a selected on-time estimate in said second set of estimates; 
 1.5. developing a timing phase error as a function of said on-time estimate, a selected early estimate in said second set of estimates preceding said on-time estimate, and a selected late estimate in said second set of estimates following said on-time estimate; and 
   2.0. in a data recovery mode of operation:
 2.1. filtering the carrier signal as a function of said accumulated estimate to develop a filtered carrier signal; 
 2.2. despreading the filtered carrier signal to develop a set of timing error metrics comprising an early metric, an on-time metric and a late metric; and 
 2.3. developing said timing phase error as a function of at least a selected one of said metrics. 
   
     
     
         10 . The method of  claim 9  further characterized as comprising the step of:
 1.6. resampling by said timing phase error said estimates following said second set of estimates. 
 
     
     
         11 . The method of  claim 9  further characterized as comprising the step of:
 2.4. resampling by said timing phase error said filtered carrier signal. 
 
     
     
         12 . Apparatus for use in an ultra-wideband (UWB) communication system in which a modulated carrier signal is transmitted via a transmission channel, the apparatus configured to perform the method according to  claim 9 .