 Spectrum shaping microwave digital modulators |
| Turning to FIG. 1, a block diagram of a typical prior art signal transmission circuit is shown for ... |
|
| PSK modulator with noncollapsable output for use with a PLL power amplifier |
| The present invention pertains to a PSK modulator for use with either wideband power amplifier up ... |
|
| Spectrally efficient digital modulation method and apparatus |
| One object of the present invention is to provide a method of pulse shaping which permits ... |
|
| Amplifier with distortion reducing feedback |
| Accordingly, an object of the invention is to provide an amplifier device in which the distortion ... |
|
| Pulse step modulator |
| The present invention is directed to minimizing dissipation by the unit step modules in a pulse ... |
|
| High frequency pulse amplifier |
| I claim: 1. A high frequency power amplifier comprising: a power amplifier stage including a ... |
|
| Low distortion operational amplifier |
| In accordance with the present invention, an operational amplifier (op-amp) operates to work with ... |
|
| Protection circuit for RF power amplifiers |
| It is an object of this invention to provide a generic control amplifier that can receive feedback ... |
|
| Portable radio communication equipment |
| The present invention has been made to solve the problems described above, and its object is to ... |
|
| Temperature insensitive piezoelectric crystal mounting arrangement |
| OF THE PREFERRED EMBODIMENT FIG. 3A illustrates a simplified top view of the crystal mounting ... |
|
|
Digital communicationn system using partial response and bipolar coding techniques
| Details |
Inventors: Hirosaki, Botaro; Shimizu, Hiroshi; Tsujimura, Yasuhiro; Yoshida, Toshihisa;
Assignee: NEC Corporation (Tokyo, JP)
Primary Examiner: Safourek; Benedict V.
Assistant Examiner: Bocure; Tesfaldet
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas
A digital communication system comprises a transmitter including a (1,0) precoder for precoding a unipolar input digital data stream and a bipolar converter for converting the output signal of the (1,0) precoder into a bipolar signal. The bipolar signal is transmitted through a metallic transmission line to a receiver. The receiver comprises a digitizer for digitizing the transmitted signal to and a line equalization filter for equalizing losses encountered during propagation through the transmission line. A (1,1) converter is provided for converting the output signal of the line equalization filter in a manner opposite to the bipolar converter. A clock recovery circuit derives sample timing pulses from the output of the line equalization filter. A decoder responds to the sample timing pulses to detect symbols from the output signal of the (1,1) converter to generate a replica of the original digital data stream. |
|
DETAILED DESCRIPTION It is therefore an object of the present invention to provide a digital communication system which combines the advantages of the partial response signalling and bipolar coding techniques and eliminates the disadvantages of the prior art.
The digital communication system of the present invention comprises a transmitter including a (1, 0) precoder for precoding a unipolar input digital data stream and a bipolar converter for converting the output signal of the (1, 0) precoder into a bipolar signal, which is transmitted over a transmission line to a receiver.
The receiver comprises a line equalization filter for equalizing losses encountered during propagation through the transmission line and a (1, 1) converter for converting the output signal of the equalization filter in a manner opposite to the bipolar converter.
A clock recovery circuit derives sample timing pulses from the output signal of the line equalization filter.
In response to the sample timing pulses a decoder detects symbols from the output signal of the (1, 1) converter to generate a replica of the original digital data stream.
In a specific aspect of the present invention, l the (1, 0) precoder has a transfer function 1/(1.
sym.
z.
sup.
-2) which is implemented by a modulo-2 adder for modulo-2 summing the unipolar input digital data stream with a second signal, and a delay line for introducting a delay time 2T to an output signal from the modulo-2 adder and supplying the delayed signal to the modulo-2 adder as the second signal, (where T represents intervals between successive symbols).
The bipolar converter has a transfer function 1-z.
sup.
-1 which is implemented by a second delay line that introduces a delay time T to the output signal of the precoder and a subtractor for subtracting the output of the second delay line from the output of the precoder.
At the receiver, the (1, 1) converter has a transfer function 1+z.
sup.
-1 which is realized by a third delay line for introducing a delay time T to the output signal of the line equalization filter and an adder for summing the output signal of the third delay line with the output signal of the line equalization filter and suppresses the higher frequency components of the output signal of the line equalization filter
|
|
Audio Signal Processing 
