MULTILEVEL PCM SYSTEM ENABLING AGC CONTROL OF A TRANSMITTED MULTILEVEL SIGNAL IN ANY SELECTED FREQUENCY PORTION OF SAID TRANSMITTED SIGNAL

• US 3,798,544 A
• Filed: 08/23/1972
• Issued: 03/19/1974
• Est. Priority Date: 09/23/1971
• Status: Expired due to Term

• Current Assignee: STC PLC (f/k/a Standard Telephones and Cables)
• Original Assignee: Peter Norman
• Inventors: Norman, Peter
• Primary Examiner(s): Mayer, Albert J.
• Application Number:
  US05/283,148
• Time in Patent Office: 573 Days
• Field of Search: 178/DIG.3,5.1 179/15AV,15BW,15AC 325/13,15,32,62,64,141,326 333/17,18,28 340/146.1A,146.1AL
• US Class Current: 375/211
• CPC Class Codes: H04B 3/06 by the transmitted signal
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04L 27/08 Amplitude regulation arrangements

Abstract

This relates to a PCM system having a substantially constant power amplitude distributed throughout the frequency spectrum of a digital signal. This enables selecting a suitable portion of the spectrum of the digital signal for operation of the AGC circuits of the system, particularly those AGC circuits contained in predetermined ones of repeater incorporated in the system. To accomplish this, the system includes, in the transmitter, a pseudo-random scrambler operating on a binary signal input to provide the substantially constant power amplitude distributed throughout the frequency spectrum of the input binary signal. The output signal of the scrambler is converted to a ternary signal prior to transmission. At the receiver the ternary input signal is converted to a binary signal. The binary signal at the output of the last converter is descrambled to compensate for the scrambling of the scrambler and to produce a replica of the binary input to the system.

Claims

1. A multilevel pulse code modulation transmission system comprising:

a transmitter including a system input for binary signals, a scrambler coupled to said system input to provide scrambled binary signals having a substantially constant power amplitude distributed throughout the frequency spectrum thereof, and a binary-to-ternary converter coupled to said scrambler to convert said scrambled binary signals to scrambled ternary signals having said substantially constant power amplitude distributed throughout the frequency spectrum thereof;

at least one repEater including a first means coupled to said binary-to-ternary converter to select a predetermined frequency portion of said frequency spectrum of said scrambled ternary signals and to produce a control signal from said predetermined frequency portion, and second means coupled to said binary-to-ternary converter and to said first means, said second means being responsive to said control signal to control the gain and/or gain-frequency characteristic thereof; and

a receiver including a ternary-to-binary converter coupled to said second means to receive said scrambled ternary signals and convert said received scrambled ternary signals to said scrambled binary signals, and a descrambler coupled to said ternary-to-binary converter to produce from said scrambled binary signals at the output of said descrambler a replica of said binary signals at said system input.

2. A system according to claim 1, wherein said scrambler includes a pseudo-random scrambler.

3. A system according to claim 1, wherein said descrambler includes a pseudo-random descrambler.

4. A system according to claim 1, wherein said first means includes a filter coupled to said binary-to-ternary converter, and an automatic gain control circuit coupled to said filter to produce said control signal;

and said second means includes an amplifier coupled to said binary-to-ternary converter and said automatic gain control circuit.