DCF77

Abstract: The identification system takes the form of apparatus which provides security by generating a numerical code which continually changes within a defined time period. A module receives the time signal from the atomic clock of the Physical-Technical Bundesanstalt (transmitter DCF77). The date and time signal is combined with a primary code entered by the user. The result defines an access address or a storage chip (e.g. EPROM). This address contains a numerical sequence (transfer code) which is transmitted and compared by the receiver with an identically generated numerical sequence. The apparatus can be connected to diverse data and signal transmission units and security systems, e.g. telephoned back transactions, bank cash machines, EDI systems and military control systems.

Abstract: DCF77 is a longwave radio transmitter located in Germany. Atomic clocks generate a 77.5-kHz carrier which is amplitudeand phase-modulated to broadcast the official time. The signal is used by industrial and consumer radio-controlled clocks. DCF77 faces competition from the Global Positioning System (GPS) which provides higher accuracy time. Still, DCF77 and other longwave time services worldwide remain popular because they allow indoor reception at lower cost, lower power, and sufficient accuracy. Indoor longwave reception is challenged by signal attenuation and electromagnetic interference from an increasing number of devices, particularly switched-mode power supplies. This paper introduces new receiver architectures and compares them with existing detectors and time decoders. Simulations and analytical calculations characterize the performance in terms of bit error rate and decoding probability, depending on input noise and narrowband interference. The most promising detector with maximum-likelihood time decoder displays the time in less than 60 s after powerup and at a noise level of Eb/N0 = 2.7 dB, an improvement of 20 dB over previous receivers. A field-programmable gate array-based demonstration receiver built for the purposes of this paper confirms the capabilities of these new algorithms. The findings of this paper enable future high-performance DCF77 receivers and further study of indoor longwave reception.

Abstract: The invention discloses a compass-based method for generating a Germany long-wave near Frankfurt 77.5 KHz (DCF77) time code. The method comprises the following steps that: 1, a compass satellite time service receiving module receives a compass satellite signal as a clock source of a time synchronous clock in the invention, processes the received compass satellite signal to acquire compass time information and second pulse information, and respectively provides the acquired compass time information and the acquired second pulse information for a time maintenance processing module and a DCF77 code element generation module; 2, after receiving the compass time information, the time maintenance processing module analyzes the compass time information, re-frames, and then forwards to the DCF77 code element generation module; and 3, the DCF77 code element generation module generates minute pulse information according to the received second pulse information and the forwarded compass time information, uses the acquired minute pulse information and the second pulse information as time origins which are generated by a code element, and obtains a code element value by correct code word addressing and code element addressing to generate the DCF77 code for output.

Abstract: The automatic correction of the autonomous clock time is undertaken using time data from the weather fax transmission programme. The automatic correction of the autonomous clock time is achieved using DCF77 time signals. A single receiver which can be changed over concerning the frequency is used for the reception of weather and time signals. Two separate receivers can be used for the reception of weather and time signals.