Five-channel control signal transmission system using DSP

Digital signal processing (DSP) has become an important modern tool to transmit control signals. This paper discusses a five-channel control signal transmission system so that it can simultaneously transmit five channels of parallel digital data at low frequencies. This new system is characterized by the realization of the BPFs used for data detection. Each frequency component is picked up from multifrequencies utilizing the DSP hardware in accordance with the algorithm used to realize a bandpass filter (BPF). The BPF output has a sharp cutoff which eliminates crosstalk among the other frequencies even though the frequency is in the range of 400 Hz to 600 Hz unlike the conventional BPF realized by operational amplifiers. When frequencies of 400 Hz and 600 Hz were applied to the BPF at the same time as and when the BPF had a bandpass characteristic at a center frequency of 500 Hz, the crosstalk was -40 dB or less. When an envelope of a stepwise input at a repetition rate of 1 Hz or less was applied, the delay time was 15 ms. Due to the excellent performance, multifrequency signals at low frequencies compress the bandwidth needed for transmission and eliminate the skewing of data transmission since the time delay is independent of the frequencies of the multifrequency signals.