Analog signal scrambling system
First Claim
1. Scrambling apparatus for converting digital samples of an analog signal having a prescribed bandwidth into a scrambled analog signal for application to a channel having a bandwidth no greater than that needed for the original signal, comprising:
- means for forming a first vector α
of discrete prolate spheroidal sequence coefficient signals from said digital samples of said analog signal,means responsive to said signals formed by said first means for rearranging said first vector of signals into a scrambled vector β
of discrete prolate spheroidal sequence coefficient signals,means responsive to said output rearranging means for reforming said scrambled vector of discrete prolate spheroidal sequence coefficient signals to output scrambled digital signal samples (Bn) for transmission, andmeans for applying said output scrambled digital signal samples as an analog signal to said channel.
0 Assignments
0 Petitions
Accused Products
Abstract
A speech scrambling system using discrete prolate spheroidal sequence coefficients (PC). The problem is to provide high fidelity and high security in a scrambling system while limiting the bandwidth of the scrambled signal to the bandwidth of the original speech signal. The disclosed system uses PC to solve this problem. The analog speech signal is digitally sampled (100), converted to PC (203, 204, 205), scrambled (208, 209), and converted to scrambled samples (211, 212, 213). The scrambled samples are transmitted using pulse amplitude modulation (102) in the same bandwidth as the original signal. At the receiving end, the inverse steps are performed to recover the original speech. The scrambling is periodically modified (220, 320) to improve security.
-
Citations
8 Claims
-
1. Scrambling apparatus for converting digital samples of an analog signal having a prescribed bandwidth into a scrambled analog signal for application to a channel having a bandwidth no greater than that needed for the original signal, comprising:
-
means for forming a first vector α
of discrete prolate spheroidal sequence coefficient signals from said digital samples of said analog signal,means responsive to said signals formed by said first means for rearranging said first vector of signals into a scrambled vector β
of discrete prolate spheroidal sequence coefficient signals,means responsive to said output rearranging means for reforming said scrambled vector of discrete prolate spheroidal sequence coefficient signals to output scrambled digital signal samples (Bn) for transmission, and means for applying said output scrambled digital signal samples as an analog signal to said channel. - View Dependent Claims (2, 3, 4, 5)
-
-
6. Descrambling apparatus for converting digital samples of a scrambled analog signal received over a channel into a descrambled analog signal comprising:
-
means for forming a preliminary vector (β
) of scrambled discrete prolate spheroidal sequence coefficient signals from said digital samples of said scrambled analog signal,means for rearranging said preliminary vector of signals into a further vector α
of descrambled discrete prolate spheroidal sequence coefficient signals,means for reforming said further vector of descrambled coefficient signals to output descrambled digital signal samples (An), and means for converting said descrambled samples to an analog signal.
-
-
7. Signal scrambling the method for converting digital samples of an analog signal having a prescribed bandwidth into a scrambled signal capable of being transmitted without substantial distortion over a channel having a bandwidth no greater than that of the original signal, comprising the steps of:
-
forming a first vector α
of discrete prolate spheroidal sequence coefficient signals from said digital samples of said analog signal,rearranging said first vector of signals into a scrambled vector β
of discrete prolate spheroidal sequence coefficient signals,reforming said scrambled vector of discrete prolate spheroidal sequence coefficient signals to output scrambled digital signal samples (Bn) for transmission, and applying said scrambled digital signal samples as an analog signal to said channel.
-
-
8. Signal descrambling method of converting digital samples of a scrambled analog signal into a descrambled analog signal comprising:
-
forming a preliminary vector (β
) of scrambled discrete prolate spheroidal sequence coefficient signals from said digital samples of said scrambled analog signal, rearranging said preliminary vector of signals into a further vector α
of descrambled discrete prolate spheroidal sequence coefficient signals,reforming said further vector of descrambled coefficient signals to output descrambled digital signal samples (An), and converting said descrambled samples to an analog signal.
-
Specification