Patent GB-1431252-A (GB)
Title: Position detecting device for an omega receiving system
IPC: G01S5/10
Filed: 1974-10-02
Abstract: 1431252 Radio navigation FURUNO ELECTRIC CO Ltd 2 Oct 1974 [29 Oct 1973] 42814/74 Heading H4D A position detecting device for an Omega receiving system comprises means for receiving first and second Omega signals from respective transmitting stations and for generating first and second signals synchronized with said received signals, means for dividing the frequency of said synchronized signals by a common divisor to produce first and second frequency-divided waves, and means for dividing the phase difference between said frequencydivided waves by the period of the Omega signals and outputting the integral quotient as the lane number, and the remainder as the phase difference between said first and second Omega signals. The device also comprises reference lane setting up means for shifting in phase said first frequency-divided wave with respect to said second frequency-divided wave until the phase difference therebetween becomes equal to said phase difference between said Omega signals plus a specific length of time corresponding to the reference lane number. As described, only the 10À2 kHz Omega frequency has been considered, and provision has been made for receiving all eight of the transmissions of a global system. A station signal generating section 10 includes eight synchronous signal generator units 111 to 118 with associated frequency divider units 121 to 128. The signal generator units provide either continuous signals synchronized with the signals received from the eigth Omega transmitting stations A to H by a receiver unit (not shown) and the divider units divide the frequency of these continuous signals by a common divisor, taken as 1800, to provide eigth frequency divided waves (hereinafter termed "station signals") which are fed to respective pairs of selectors 213, 214 and 223, 224 in identical first and second measuring sections 21, 22. Respective station encoders 211, 212 and 221, 222 are associated with said selectors and are pre-set for desired stations by manually operated means, such as push buttons. The measuring sections also include gate circuits 215, 225, counters 216, 226 with indicators 218, 228, and counters 217, 227 with indicators 219, 229. A clock 23 of pulse frequency 100 times the Omega frequency provides outputs through the gates 215, 225 when these are enabled. The counters 216, 226 produce outputs at every hundred pulses, so that the indicators 219, 229 represent lane numbers. The remainders in the counters 216, 226 are represented by the indicators 218, 228 as phase differences in centilanes. These phase differences are further supplied in coded form through a switching gate circuit 24 to a control wave generating section 40. Lane loading for adding a further phase shift, corresponding to the reference lane number to the phase difference between a pair of station signals is effected by interrupting the operation of the synchronous signal generator in the station signal section 10, which is associated with either of said stations, for a time interval corresponding to the reference lane number. For this purpose, the section 40 produces a control wave, a switching section 50 discriminates the station concerned, and a control section 30 executes the interrupting operation as determined by said sections 40, 50. The operation of the logical circuitry of the sections 30, 40, 50 as shown in Fig. 4, is described in the Specification with reference also to Figs. 5 to 9 (not shown). Manual controls provided comprise two lane locking switchboards 51, 52 each with eight key units corresponding to the stations A to H, and a changeover switch 43.