Method and apparatus for time companding an analog signal
First Claim
1. A method for compressing an analog signal, comprising the steps of:
- (a) digitizing the analog signal at a first rate using a continuously variable slope delta modulator to provide a digitized signal;
(b) storing said digitized signal at said first rate in a digital storage means to provide a stored signal;
(c) retrieving a time segment of said stored signal from said digital storage means at a second rate, said second rate being at least twice that of said first rate, to provide a time segment retrieved signal;
(d) converting said time segment retrieved signal into an analog signal using a continuously variable slope delta demodulator to provide a compressed signal.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and apparatus to compand an analog message to afford a two-to-one improvement in spectral efficiency, while contemporaneously minimizing distortion in the received signal. According to the invention, an analog message such as a voice message is digitized in a continuously variable slope delta modulator (CVSD) and stored at a first rate. The digitized message is removed from the storage means, interleaved with a predetermined signal, and converted back into an analog message in a continuously variable slope delta demodulator at a second rate being at least twice as fast as the first rate. The analog signal is then transmitted during at least one time slot of a communication channel. The predetermined pattern operates to minimize the distortion ordinarily created by digitizing the analog signal.
31 Citations
8 Claims
-
1. A method for compressing an analog signal, comprising the steps of:
-
(a) digitizing the analog signal at a first rate using a continuously variable slope delta modulator to provide a digitized signal; (b) storing said digitized signal at said first rate in a digital storage means to provide a stored signal; (c) retrieving a time segment of said stored signal from said digital storage means at a second rate, said second rate being at least twice that of said first rate, to provide a time segment retrieved signal; (d) converting said time segment retrieved signal into an analog signal using a continuously variable slope delta demodulator to provide a compressed signal.
-
-
2. A method for expanding a time segment time compressed analog signal, comprising the steps of
(a) digitizing the time segment compressed signal at a first rate using a continuously variable slope delta modulator to provide a time segment digitized signal; -
(b) storing said time segment digitized signal at said first rate in a storage means to provide a time segment stored signal; (c) retrieving said time segment stored signal from said storage means at a second rate, said first rate being at least twice that of said second rate, to provide a time segment retrieved signal; (d) converting said time segment retrieved signal into an analog signal using a continuously variable slope delta demodulator to provide an expanded signal.
-
-
3. A method of companding an analog signal, comprising the steps of:
-
(a) digitizing the analog signal at a first rate using a continuously variable slope delta modulator to provide a first digitized signal; (b) storing said first digitized signal at said first rate in a storage means to provide a first stored signal; (c) retrieving a time segment of said first stored signal from said storage means at a second rate, said second rate being at least twice that of said first rate, to provide a time segment first retrieved signal; (d) converting said time segment first retrieved signal into an analog signal using a continuously variable slope delta demodulator to provide a time segment compressed signal; (e) digitizing said time segment compressed signal at said second rate using a continuously variable slope delta modulator to provide a time segment second digitized signal; (f) storing said time segment second digitized signal at said second rate in a storage means to provide a time segment second stored signal; (g) retrieving said time segment second stored signal from said storage means at said first rate to provide a time segment second retrieved signal; (h) converting said time segment second retrieved signal into an analog signal using a continuously variable slope delta demodulator to provide an expanded signal.
-
-
4. A full duplex transceiving device, for time compression multiplexing an analog signal, comprising:
-
means for storing a first and second digitized signal each having a respective data rate, said second rate being at least twice that of said first rate, to provide a first and second stored signal; means for retrieving said first and second stored signals from said storage means at converse data rates to provide a first and second retrieved signal; first continuously variable slope delta modulator/demodulator means for alternately converting said first retrieved signal at said second data rate to provide a compressed analog signal, and for digitizing a received compressed analog signal at said second data rate provide said second digitized signal; second continuously variable slope delta modulator/demodulator means for continuously digitizing the analog signal at said first data rate provide said first digitized signal; means for transmitting said compressed analog signal during at least one time slot of a communication channel; means for receiving said compressed analog signal during at least one time slot of said communication channel to provide said received compressed analog signal; third continuously variable slope delta modulator/demodulator means for continuously converting said second retrieved signal into an analog signal at said first data rate to provide a expanded recovered signal; whereby, said first continuously variable slope delta modulator/demodulator means is multiplexed at said second data rate, and said second and third continuously variable slope delta modulator/demodulator means continually operate at said first data rate to provide full duplex communication on a single communication channel.
-
-
5. A compressor for compressing an analog signal, comprising:
-
continuously variable slope delta modulator means for digitizing the analog signal at a first rate to provide a digitized signal; means for storing said digitized signal at said first rate to provide a stored signal; means for retrieving a time segment of said stored signal from said storage means at a second rate, said second rate being at least twice that of said first rate, to provide a time segment retrieved signal; continuously variable slope delta demodulator means for converting said time segment retrieved signal into an analog signal to provide a compressed signal.
-
-
6. An expandor for expanding a time segment time compressed analog signal, comprising:
-
continuously variable slope delta modulator means for digitizing the time segment compressed signal at a first rate to provide a time segment digitized signal; means for storing said time segment digitized signal at said first rate to provide a time segment stored signal; means for retrieving said time segment stored signal from said storage means at a second rate, said first rate being at least twice that of said second rate, to provide a time segment retrieved signal; continuously variable slope delta demodulator means for converting said time segment retrieved signal into an analog signal to provide an expanded signal.
-
-
7. A method for minimizing distortion in a time compressed analog transmission system, comprising the transmitter steps of:
-
(a) digitizing an analog signal at a first rate in a continuously variable slope delta modulator to provide a digitized signal; (b) storing said digitized signal at said first rate in a digital storage means to provide a stored signal; (c) retrieving said stored signal from said digital storage means at a second rate, said second rate being at least twice that of said first rate, to provide a retrieved signal; (d) interleaving said retrieved signal with a predetermined digital pattern to provide an interleaved signal; (e) converting said interleaved signal into an analog signal in a continuously variable slope delta demodulator to provide a compressed signal; (f) transmitting at least said compressed signal.
-
-
8. A method for minimizing distortion in a time compressed analog transmission system, comprising the transmitter steps of:
-
(a) digitizing an analog signal at a first rate in a continuously variable slope delta modulator to provide a digitized signal; (b) storing said digitized signal at said first rate in a digital storage means to provide a stored signal; (c) retrieving said stored signal from said digital storage means at a second rate, said second rate being at least twice that of said first rate, to provide a retrieved signal; (d) interleaving said retrieved signal with an alternating logic 1 - logic 0 (dotting) pattern to provide an interleaved signal; (e) converting said interleaved signal into an analog signal in a continuously variable slope delta demodulator to provide a compressed signal; (f) transmitting at least said compressed signal.
-
Specification