초록 ▼

Partial response and quadrature partial response data transmission system characterized by increased transmission rate, lower signal-to-noise ratio, low cost and simpler hardware implementation than prior art systems. A steep filter (almost rectangular) is connected to the output of a cosine filter,

Partial response and quadrature partial response data transmission system characterized by increased transmission rate, lower signal-to-noise ratio, low cost and simpler hardware implementation than prior art systems. A steep filter (almost rectangular) is connected to the output of a cosine filter, forming a composite filter, wherein the cut-off frequency of the rectangular filter is less than the Nyquist frequency by a predetermined amount which is inversely proportional to the amount in percentage by which the data transmission rate exceeds the Nyquist rate. The system is thus capable of signalling at the Nyquist rate and greater, without requiring that channel filter parameters or the basic clock rate be adjusted. A smaller number of signal levels can be selected (as compared to previously existing methods) for spectrally efficient applications, and the resulting more robust system can also be used to transmit PAM, QAM, and other baseband or modulated signals.

대표청구항 ▼

A data transmission system comprised of: (a) means for receiving a digital input signal characterized by a predetermined transmission rate, (b) a half-cosine filter for receiving and filtering said received digital input signal and for providing a filtered output signal, characterized by a transfer

A data transmission system comprised of: (a) means for receiving a digital input signal characterized by a predetermined transmission rate, (b) a half-cosine filter for receiving and filtering said received digital input signal and for providing a filtered output signal, characterized by a transfer function having a transmission null at Nyquist frequency, and (c) a very steep low-pass filter connected in series with said half-cosine filter, and having a cut-off frequency which is less than the Nyquist frequency by a predetermined amount, for receiving and further filtering said filtered output signal, thereby limiting intersymbol interference and enabling digital signal transmission at a transmission rate greater than the Nyquist rate by said predetermined amount.