New type of multifrequency detector using DSP for control signal transmission system

Digital signal processing (DSP) has become an important modern tool in detection of signal transmission. This paper discusses a new method to detect a frequency component from multifrequency signals at low frequencies in the multifrequency parallel data transmission system. Each frequency component is picked up from multifrequencies utilizing the DSP hardware in accordance with the algorithm to realize a bandpass filter. The BPF output has a sharp cutoff which eliminates crosstalk among the other frequencies even though the frequency is in the range of 1.6 kHz to 2.4 kHz unlike the conventional BPF realized by operational amplifiers. The bandwidth was, as an example, 1.5 kHz to 2.5 kHz at a center frequency of 2 kHz. When frequencies of 2.0 kHz and 2.8 kHz were applied to the BPF at the same time and when the BPF had a bandpass characteristic at a center frequency of 2 kHz, 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 4.5 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