Timing and Time Information Extraction in a Radio Controlled Clock Receiver

Abstract

A novel and useful system and method for extracting timing, time and additional information from a broadcast received in a radio controlled clock (RCC) receiver. The RCC receiver extracts timing information represented by a known synchronization sequence that is used for acquisition and tracking purposes. The RCC receiver extracts time information as a merged 26-bit time information word linearly coded into 31 bits comprising the number of minutes (or hours) since the turn of the current century. A minute counter representing the 26 bits is converted into the date, hour, and minute. The RCC extracts additional information including the schedule for the next daylight saving time transition and for an imminent leap second. The communications protocol optionally employs error correcting codes to provide protection for data fields in the frame, which the RCC may use to enhance reception reliability in the presence of noise and interference.

What is claimed is: 
     
         1 . A radio receiver method, said method comprising:
 receiving a phase modulated (PM), pulse width modulated (PWM)/amplitude shift keyed (ASK) broadcast signal encoded with phase-modulated time information frames;   extracting said time information frames from the phase of said received signal; and   wherein each said time information frame includes a synchronization sequence field and a current time field.   
     
     
         2 . The method according to  claim 1 , wherein each said time information frame further comprises a daylight-saving time data field. 
     
     
         3 . The method according to  claim 1 , wherein each said time information frame further comprises a leap second data field. 
     
     
         4 . The method according to  claim 1 , wherein each said time information frame further comprises a daylight saving time data field and leap second data field, which are jointly protected using an error correcting code. 
     
     
         5 . The method according to  claim 1 , wherein said current time field indicates the current minute, hour, date and year expressed as a number of hours from the beginning of the current century. 
     
     
         6 . The method according to  claim 1 , wherein said current time field indicates the current minute, hour, date and year expressed as a number of minutes from the beginning of the current century. 
     
     
         7 . The method according to  claim 1 , wherein said current time field comprises a current time protected using an error correcting code. 
     
     
         8 . The method according to  claim 1 , further comprising avoiding using marker symbols in a WWVB legacy protocol to convey time information. 
     
     
         9 . The method according to  claim 1 , further comprising using marker symbols in a WWVB legacy protocol only to convey timing information using said synchronization sequence. 
     
     
         10 . The method according to  claim 1 , wherein said synchronization sequence field comprises a 14-bit synchronization sequence. 
     
     
         11 . A radio receiver method, said method comprising:
 receiving a phase modulated (PM), pulse width modulated (PWM)/amplitude shift keyed (ASK) broadcast signal encoded with phase-modulated time information frames;   extracting said time information frames from the phase of said received signal; and   wherein each said time information frame includes a synchronization sequence field, a current time field, daylight savings time data field and leap second data field, said current time field, daylight savings time data field and leap second data field protected using error correcting codes.   
     
     
         12 . The method according to  claim 11 , wherein said current time field indicates the current minute, hour, date and year expressed as a number of hours from the beginning of the current century in a first subfield and the current minute (0-59) in a second sub-field. 
     
     
         13 . The method according to  claim 11 , wherein said current time field indicates the current minute, hour, date and year expressed as a number of minutes from the beginning of the current century. 
     
     
         14 . A radio receiver method, said method comprising:
 receiving a phase modulated (PM) broadcast signal encoded with time information frames;   extracting said time information frames from the phase of said received signal; and   wherein each said time information frame includes a synchronization sequence field and a current time field.   
     
     
         15 . The method according to  claim 14 , wherein said current time field is split into a first sub-field indicating the current minute (0-59) and a second sub-field indicating the hour, date and year expressed as a number of hours from the beginning of the current century. 
     
     
         16 . The method according to  claim 14 , wherein said current time field indicates the current minute, hour, date and year expressed as a number of minutes from the beginning of the current century. 
     
     
         17 . A radio receiver, comprising:
 a receiver circuit operative to receive a phase modulated (PM), pulse width modulation (PWM)/amplitude shift keyed (ASK) broadcast signal encoded with phase-modulated time information frames;   a circuit operative to extract said time information frames from the phase of said received signal; and   wherein each said time information frame includes a synchronization sequence field and a current time field.   
     
     
         18 . The receiver according to  claim 17 , wherein said current time field indicates the current minute, hour, date and year expressed as a number of hours from the beginning of the current century in a first subfield and the current minute (0-59) in a second sub-field. 
     
     
         19 . The receiver according to  claim 17 , wherein said current time field indicates the current minute, hour, date and year expressed as a number of minutes from the beginning of the current century. 
     
     
         20 . The receiver according to  claim 17 , wherein each said time information frame further comprises a daylight saving time data field. 
     
     
         21 . The receiver according to  claim 17 , wherein each said time information frame further comprises a leap second data field. 
     
     
         22 . The receiver according to  claim 17 , wherein each said time information frame further comprises a daylight saving time data field and leap second data field, both of which are protected using an error correcting code. 
     
     
         23 . The receiver according to  claim 17 , wherein each said time information frame further comprises a field to indicate whether daylight saving time is in effect or not, said indication provided with an error correcting code. 
     
     
         24 . The receiver according to  claim 17 , wherein said current time field comprises a current time protected using an error correcting code. 
     
     
         25 . The receiver according to  claim 17 , wherein marker symbols in a WWVB legacy protocol are not used to convey time information. 
     
     
         26 . The receiver according to  claim 17 , wherein marker symbols in a WWVB legacy protocol are used only to convey timing information using said synchronization sequence. 
     
     
         27 . The receiver according to  claim 17 , wherein said synchronization sequence field comprises a 14-bit synchronization sequence. 
     
     
         28 . The receiver according to  claim 17 , wherein the least-significant bit (LSB) of said current time field is extracted during a tracking operation.