Digital signal processor modem

• US 4,620,294 A
• Filed: 09/09/1983
• Issued: 10/28/1986
• Est. Priority Date: 09/09/1983
• Status: Expired due to Fees

• Current Assignee: Tommy Y. Leung
• Original Assignee: CTS Corporation
• Inventors: Waldron, Mark A., Leung, Tommy Y.
• Primary Examiner(s): Heckler, Thomas M.
• Application Number:
  US06/530,690
• Time in Patent Office: 1,145 Days
• Field of Search: 370/11, 370/19, 375/46, 375/56, 375/89, 375/62, 364/200 MS File, 364/900 MS File
• US Class Current: 375/222
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 5/143 for modulated signals H04L5/1469 takes precedence

Abstract

A dual speed, full duplex modem for transmitting and receiving data on a dialed-access telephone line includes a signal processor for storing samples corresponding to a sinusoidal waveform, for selecting samples at intervals determined by the mode in which the modem is operating to synthesize a signal for modulating by data for transmission, and for autocorrelating a received signal at a frequency determined by the mode in which the modem is operating to recover data from the received signal. The signal processor includes configuring input ports, and a microcomputer receives instructions related to the mode in which the modem is to operate to output a mode-configuring word to the configuring inputs. Conversion from the signal processor'"'"'s digital output to the analog signal to the line and from the line'"'"'s analog signal to the signal processor'"'"'s digital input take place through two time-division multiplexed coder-decoders. The stored sinusoid is mu-law compressed. The modem can dual tone, multiple frequency dial. The DTMF pair requires a different amplitude from the amplitude of the synthesized signal for modulating by data for transmission. A power series expansion of the required amplitudes of the DTMF tone pair permits both the synthesized signal for modulating by data for transmission and the tones of the DTMF pair to be calculated from the mu-law compressed sinusoid.

Claims

1. A telephone network between an originate modem and an answer modem, at least one said modem comprising a two speed, full duplex modem for transmitting and receiving analog signals through said telephone network, said full duplex modem comprising:

(a) a data terminal means for transmitting and receiving digital data;

(b) a microcomputer means in communication with the data terminal means;

(c) a signal processor means in communication with the microcomputer means, said signal processor means further providing a means for storing a plurality of digital data samples corresponding to a sinusoidal waveform;

(d) a converting means in communication with the signal processor means for converting digital data from the signal processor to the analog signal for transmission over the telephone network, and for converting the received analog signal from the telephone network to the digital data;

(e) a filter means in communication with the converting means and the telephone network for filtering the analog signal for transmission between the converting means and the telephone network, and for filtering the received analog signal; and

(f) a selecting means in communication with the microcomputer means for selecting a bit rate mode using the digital data from the data terminal means;

said selecting means further providing a means responsive to the bit rate of the originate modem, to selectively communicate either a relatively higher bit rate by differential phase shift keying, or a relatively lower bit rate by frequency shift keying;

the selecting means further providing a means for selecting digital data samples at intervals determined by the bit rate mode, to synthesize the digital data modulated for transmission through the converting means to the analog signal for transission through the filter means over the telephone network for communication between the originate modem and the answer modem.

2. The modem of claim 1, wherein the signal processor means further comprises a means for selecting the digital data samples at intervals determined by a dialed digit stored in the microcomputer means to generate a tone pair for transmission through the converting means to the telephone network.

3. The modem of claim 2 wherein the means for selecting samples at intervals determined by a dialed digit to generate a tone pair comprises a means for dividing a time base into substantially equal first and second alternating intervals and for selecting at intervals to generate a sample of one of the tones of the pair during alternate first intervals, and for selecting at intervals to generate a sample of the other tone of the pair during alternate second intervals.

4. The modem of claim 3 wherein the tone pair is a DTMF pair.

5. The modem of claim 3, wherein the signal processor means further comprises a means for storing a power series approximation of a stored sample, and for calculating one of a first and second amplitudes from the power series approximation and the stored sample to provide one of the tones of the pair selectively at the first and second intervals of the time base.

6. The modem of claim 1, wherein the signal processor means further comprises a means for correlating the received analog signal at a frequency determined by the selecting means to recover data from the received analog signal for communication to the microcomputer means.

7. The modem of claim 6, wherein the received analog signal and the digital data modulated for transmission are frequency division multiplexed for substantially simultaneously transitting and receiving data.

8. The modem of claim 1 wherein the digital signal samples corresponding to a sinusoidal waveform comprise a mu-law compressed sinusoidal waveform.

9. The modem of claim 1, wherein the converting means comprises a coder-decoder.

10. The modem of claim 1 wherein the signal processor means and microcomputer means comprise one or more configuring input terminals and one or more configuring output terminals for coupling respective configuring output terminals to respective configuring input terminals.

11. A telephone network between an originate moden and an answer modem, said modems for transmitting and receiving analog signals over said telephone network, at least one said modem comprising:

(a) a data terminal means for transmitting and receiving digital data;

(b) a microcomputer means in communication with the data terminal means;

(c) a selecting means responsive to the microcomputer means for selecting one of a relatively higher bit rate mode by differential phase shift keying, and a relatively lower bit rate mode by frequency shift keying;

the selected bit rate mode determined by the bit rate mode of the originate modem;

(d) a signal processor means in communication with the microcomputer means, said signal processor means for storing digital data samples corresponding to a mu-law compressed sinusoidal waveform;

(e) and a converting means in communication with the signal processor means and the telephone network, said converting means for converting the digital data for transmission from the signal processor means to synthesize the analog signal for transmission over the telephone network, and for converting the received analog signal from the telephone network to the digital data.

12. The modem of claim 11, wherein the microcomputer means selects samples stored at intervals from the digital data samples stored in the signal processor means, to generate a tone pair corresponding to a dialed digit.

13. The modem of claim 12, wherein the tone pair corresponding to a dialed digit comprises a means for dividing a time base into substantially equal first and second alternating intervals and for selecting the digital data samples at intervals to generate a sample of one of the tones of the pair during alternate first intervals and for selecting a sample of the other tone of the pair during alternate second intervals.

14. The modem of claim 13 wherein the tone pair is a DTMF pair.

15. The modem of claim 13, wherein the digital data modulated for transmission is provided generally at a first amplitude and the tones of the pair are provided generally at a second amplitude, the signal processor means further comprising means for storing a power series approximation of one of the first and second amplitudes from any stored sample and for calculating the one of the first and second amplitudes from the power series approximation and the stored sample to provide signals selectively at the first and second amplitudes.

16. The modem of claim 11 wherein the converting means comprises a coder-decoder.

17. The modem of claim 11 and further comprising means for filtering the signal for transmission.

18. The modem of claim 11 and further comprising means for filtering the received signal.

19. A dialed access telephone line between an originate modem and an answer modem, at least one modem comprising a two speed full duplex modem for simultaneously transmitting and receiving an analog signal over said dialed access telephone line, said full duplex modem comprising:

a data terminal for transmitting and receiving digital data;

a microcomputer means in communication with the data terminal means;

a signal processor means in communication with the microcomputer means, said signal processor means with a dual speed mode for correlating a received analog signal from the telephone line at a frequency determined by the bit rate of the originate modem to recover digital data from the received analog signal, said signal processor means for storing a plurality of digital data samples corresponding to a sinsusoidal waveform, and for selecting the digital data samples at intervals determined by the bit rate in which the originate modem is operating the synthesize an analog signal for transmission over the telephone line, and to selectively communicate over the telephone line a relatively higher bit rate by differential phase shift keying, or a relatively lower bit rate by frequency shift keying.

20. The modem of claim 19, wherein the samples corresponding to a sinusoidal waveform are a mu-law compressed sinusoidal waveform.

21. A dual speed, full duplex modem system comprising a first data terminal;

a first, or originate modem;

a conductor pair;

a second, or answer modem; and

a second data terminal;

means for coupling the first data terminal to the first modem;

means for coupling the second data terminal to the second modem;

means for coupling the first modem to the conductor pair;

means for coupling the second modem to the conductor pair;

at least one of the originate and answer modems comprising a dual speed means for selectively transmitting data at or about a first carrier frequency by frequency shift keying, and for simultaneously receiving data at or about a second carrier frequency by frequency shift keying;

the dual speed means further comprising means for selectively transitting data at or about a third carrier frequency by quadrature differential phase shift keying and for simultaneously receiving data at or about a fourth carrier frequency by quadrature differential phase shift keying;

each modem comprising means for converting outgoing analog signals for transmission from digital data to analog signals and for converting incoming analog signals for reception from analog signals to digital data, wherein each of the first and second modems comprises a signal processor means for processing outgoing data to produce a first stream of digital data;

means for coupling the signal processor means to a converter means to convert the first stream of digital data into analog signals at or about the first frequency or the third frequency, the converter means being capable of processing an incoming second stream of analog signals and converting the second stream of analog signals into received digital data for simultaneously processing by the signal processor means;

means for coupling the signal processor means to the converter means to convert digital data at or about the second or fourth frequency into the second stream of digital signals, the first and second modems further comprising a microcomputer means operatively connected to the signal processor means, for storing digital data regarding the signals at or about the first, second, third and fourth frequencies and for configuring the signal processor means to selectively process the digital data at or about th first and second frequencies;

or at or about the third and fourth frequencies depending upon the dual speed means of the originate modem.

22. The modem system of claim 21, wherein the microcomputer means includes a scrambler/descrambler for scrambling information supplied by one of the first and second data terminals in accordance with a pre-determined scrambler algorithm;

and for descrambling information received from the other of the first and second data terminals in accordance with a predetermined descrambler algorithm.

23. The modem system of claim 21, wherein the frequency shift keying is coherent.

24. The modem system of claim 21, wherein the signal processor means further comprises a means for correlating the digital data signals at or about the second and fourth frequencies to recover the second stream of digital data signals.

25. The modem system of claim 21, wherein the signal processor means further comprises a means for storing sample values corresponding to the signals at or about the first and third frequencies at various sampling points and a means for synthesizing the stored sample values at or about the first and third frequencies.

26. The modem system of claim 21, wherein the digital-to-analog converter comprises a coder-decoder.

27. A dual speed, full duplex modem system comprising a first data terminal;

a first, or originate modem;

a dialed-access telephone line;

a second, or answer modem;

a second data terminal;

means for coupling the first data terminal to the first modem;

means for coupling the first modem to the dialed-access telephone line;

means for coupling the second modem to the second data terminal;

means for coupling the second modem to the dialed access telephone line;

each modem including means for transmitting data at or about a first carrier frequency by frequency shift keying and for simultaneously receiving signals at or about a second carrier frequency by frequency shift keying;

each modem further including means for transmitting data at or about a third carrier frequency by quadrature differential phase shift keying and for simultaneously receiving data at or about a fourth carrier frequency by quadrature differential phase shift keying;

each modem comprising means for converting outgoing signals for transmission from digital to analog form and for converting incoming signals for reception from analog to digital form;

at least one of the first and second modems comprising a signal processor means for processing outgoing data to produce a first stream of digital signals;

means for coupling the signal processor means to a digital-to-analog converter to convert the first stream of digital signals into analog signals at or about the first frequency or the third frequency;

an analog-to-digital converter to convert signals at or about the second or fourth frequency into a second stream of digital signals;

the signal processor means being capable of simultaneously processing the incoming second stream of digital signals and converting the second stream of digital signals into received data;

means for coupling the signal processor means to the analog-to-digital converter;

a microcomputer means for storing data regarding the signals at or about the first, second, third and fourth frequencies; and

for configuring the signal processor means to selectively process signals either at or about the first and second frequencies or at or about the third and fourth frequencies.

28. The modem system of claim 27 wherein the microcomputer includes a scrambler/descrambler for scrambling information supplied by one of the first and second data terminals in accordance with a predetermined scrambler algorithm;

and for descrambling information received from the other of the first and second data terminals in accordance with a predetermined descrambler algorithm.

29. The modem system of claim 27, wherein the frequency shift keying is coherent.

30. The modem system of claim 27, wherein the signal processor means further comprises a means for correlating the signals at or about the second and fourth frequencies to recover the second stream of digital data signals.

31. The modem system of claim 27, wherein the signal processor means further comprises a means for storing sample signals at or about the first and third frequencies at various sampling points and a means for synthesizing the stored sample values corresponding to the signals at or about the first and third frequencies.