Digital code transmission with medium wave AM radio transmitter

The authors describe a new system for multiplexing digital codes onto the AM radio signal at medium wave frequency, and also analyze the interference of the digital codes with the AM radio signal. This type of phase shift keying (PSK) system was actualized by using the phase modulation of a narrowband phase shift. The phase modulation of the narrowband phase shift suppressed the required spectrum band energy under 10 dB compared with that in the normal BPSK the QPSK system and the interference of the PSK signal with the AM signal was improved by approximately 15 dB compared with that in the normal BPSK or QPSK system. The experimental results agree with the results of the computer simulation. Up to 99% of the transmitted signal energy was designed to fall into a bandwidth of +or-7.5 kHz around a center frequency of 1 MHz when the system was operated at a data rate of 1200 b/s or 2400 b/s, when the total angle of phase shift was 90 degrees in 2 phi PSK and when the total angle of phase shift was 150 degrees at 4 phi PSK.<>