SDR implementation for DCF77

The DCF77 signal is used to carry out the information of precise time for long distances. Standard DCF77 receivers consist of AM long wave receiver circuit, connected to a data processing unit. Whole AM receiver circuit is often integrated into a chip with some external components. Such circuit gives demodulated logical data output, which can be led right to the processor to be decoded and presented. The idea is to remove the analog demodulator and process the amplified RF signal also on the processor. Specialized AM radio chip then would be replaced by a simple amplifier, e.g. operational amplifier circuit. Nowadays, microcontrollers include AD converters fast enough to digitalize signals at frequencies above 77.5 kHz. Using the advantages of undersampling, Goertzel algorithm and correlation techniques, it allows to make program very low computational power demanding. Developed algorithm is supposed to be implemented to 70 MHz ARM7 LPC2103 microcontroller. Examples of code realization in GCC are introduced also with discussion of possible complications.