Filtered Manchester Coded PSK transmission system

• US 4,507,794 A
• Filed: 05/04/1983
• Issued: 03/26/1985
• Est. Priority Date: 05/04/1983
• Status: Expired due to Fees

• Current Assignee: Donald A. Johnston, Stephen K. Jones
• Original Assignee: Donald A. Johnston, Stephen K. Jones
• Inventors: Jones, Stephen K., Johnston, Donald A.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Chin, Stephen
• Application Number:
  US06/491,605
• Time in Patent Office: 692 Days
• Field of Search: 375/17, 375/18, 375/55, 375/87, 375/94, 375/103, 375/58, 340/347 DD, 360/45, 364/724
• US Class Current: 375/282
• CPC Class Codes: H04L 25/4904 using self-synchronising codes, e.g. split-phase codes
• CPC Class Codes: H04L 7/0054 Detection of the synchronisation error by features other than the received signal transition by means of signal transition H04L7/033

Abstract

A system for digital transmission includes an active pulse forming network to convert a digital data signal into a Manchester Coded PSK format. A low pass filter network is provided to transform the Manchester Coded signal for transmission over a bandlimited wireline channel. The receiver includes a low pass filter and a bandpass filter that combine to form an overall bandpass filter response for receiving the output of the wireline channel. The transmitter low pass filter and the receiver bandpass filter combine to transform the Manchester Coded PSK data signal into a quasi-raised cosine signal that has the digital data signal coded therein. A timing recovery circuit is included that extracts a timing signal from the quasi-raised cosine signal to provide a coherent timing signal such that the quasi-raised cosine signal can be sampled and the digital data signal reconstructed. The timing recovery circuit delays the quasi-raised cosine signal and multiplies it by the reconstructed digital data signal and the product signal thereof is half-wave rectified and input to a phase lock loop which locks onto the signal to provide a reconstructed timing signal to drive a sampling circuit.

Claims

1. A method for digital transmission comprising:

coding a binary antipodal data signal into a Manchester Coded PSK format;

passing the coded data through a first transforming network having a transfer function of low pass type;

transmitting the signal output by the first transforming network over a communications channel;

receiving the transmitted data;

passing the received data through a second transforming network having a second transfer function of low pass type to transform the signal into two superimposed raised cosine signals of opposite polarities and shifted in time by the signaling rate thereof;

passing the signal output by the second transforming network through a third transforming network of bandpass type to transform the signal into a quasi-raised cosine signal; and

coherently sampling the raised cosine signal to reconstruct the digital data signal.

2. The method of claim 1 wherein the step of coherent sampling comprises reconstructing a timing signal from the quasi-raised cosine signal and sampling the quasi-raised cosine signal at the signalling rate thereof.

3. The method of claim 2 wherein the step of reconstructing comprises:

multiplying the quasi-raised cosine signal by the reconstructed data signal;

halfwave rectifying the product signal; and

locking a phase lock loop to the halfwave rectified product signal.

4. A system for digital transmission comprising:

means for coding a digital data signal into a bandpass type format;

a first low pass transforming network;

a transmitter for transmitting the signal output by said first transforming network;

a communications channel for receiving the output of said transmitter, said communications channel having a channel transfer function;

a receiver for receiving the signal output by said communications channel;

a second low pass transforming network for transforming the received signal into two superimposed raised cosine signals having equal and opposite polarities and shifted in time by the signalling rate thereof;

a bandpass transforming network for transforming said superimposed raised cosine signals into a quasi-raised cosine signal to provide an output signal having no DC component; and

means for coherently sampling said output signal to reconstruct said digital data signal.

5. The system of claim 4 wherein said bandpass type format comprises a Manchester Coded PSK format.

6. A system for digital transmission comprising:

means for coding a digital data signal into a Manchester Coded PSK format;

means for transforming said coded data by a first transfer function of low pass type;

means for transmitting the data processed with said first transfer function over a communications channel;

means for receiving the output of said communications channel;

a low pass filter for transforming said transformed data into two superimposed raised cosine signals having equal and opposite polarities and shifted in time by the signalling rate thereof;

a bandpass filter for transforming said superimposed raised cosine signals into a quasi-raised cosine signal; and

means for coherently sampling said quasi-raised cosine signal to reconstruct said digital data signal.

7. The system of claim 6 wherein said means for transforming comprises a low pass filter.

8. The system of claim 6 wherein said means for coherently sampling comprises:

a delay circuit for delaying said quasi-raised cosine signal;

a sampling circuit for sampling said quasi-raised cosine signal and outputting a binary antipodal data signal;

a multiplication circuit for multiplying the signal output from said delay circuit by said data signal; and

a phase locked loop for receiving the output of said multiplication circuit, the output of said phase locked loop for controlling the sampling rate of said sampling circuit.

9. A system for digital transmission comprising means for coding a digital data signal into a Manchester Coded PSK format;

a first low pass filter having a first transfer function for transforming said coded data;

a communications channel for transmitting the output of said first low pass filter to a receiver;

a second low pass filter having a second transfer function for receiving the transformed data from said first low pass filter that is transmitted over said communications channel;

a bandpass filter having a third transfer function for receiving the output of said second low pass filter, said first and second low pass filters and said bandpass filter concatenated to transform said coded data signal into a quasi-raised cosine signal;

a sampling circuit; and

a timing signal recovery circuit for recovering the timing signal from said quasi-raised cosine signal for input to said sampling circuit such that said quasi-raised cosine signal is sampled at the optimum point.

10. The system of claim 9 wherein said timing recovery network comprises:

a delay circuit for delaying said quasi-raised cosine signal;

a multiplication circuit for receiving the reconstructed digital data signal output by said sampling network and the output of said delay circuit, said multiplication circuit outputting a product signal;

a half wave rectifier for half wave rectification of said product signal; and

a phase lock loop for receiving the output of said half wave rectifier and locking thereto.