Phase and amplitude modulated modem

Claim 2

In a data transmission system for sending digital data between a transmitter and a receiver over a transmission link by establishing predetermined phase differences and amplitude levels in a carrier signal during successive modulation periods representative of preselected data combinations which comprises: a modulator at the transmitter including: means for continuously grouping the digital date into multibit words of equal length; means responsive to preselected data combination subgroups within each of the multibit words for providing predetermined phase differences in the carrier signal during successive modulation periods in such a manner that each of the subgroups corresponds to a predetermined phase difference relative to the phase of the carrier in the immediately preceding modulation period; means responsive to the possible data combinations within each subgroup for varying the amplitude of the carrier signal during said successive modulation periods in such a manner that each possible data combination within each subgRoup corresponds to a predetermined amplitude level; and filter means connected in the signal transmission link, the filter being characterized as having a passband width of about 1/T Hz. And a center frequency of fo; where T is the modulation period; fo is the carrier signal frequency, and T/2 is cycles per second.

Claim 3

The data transmission system of claim 1 wherein said grouping means comprises: storage means having three binary bit storage locations and responsive to the digital data to be transmitted for storing three binary bits of data during each modulation period.

Claim 4

The data transmission system of claim 2 wherein said phase difference providing means comprises: means responsive to predetermined data patterns in two of said three storage locations for establishing phase differences in the carrier signal during successive modulation periods in accordance with the function N90*, where N O, 1, 2 or 3, whereby phase differences of 0* , 90* , 180* and 270* will be established during successive modulation periods as a function of said predetermined data patterns.

Claim 5

The data transmission system of claim 3 wherein said carrier signal amplitude varying means comprises: means responsive to the bit value of the remaining storage location for establishing one of two predetermined amplitude levels for the carrier signal for each modulation period, whereby the carrier signal will be provided with one of two predetermined amplitude levels as a function of the value of the remaining binary bit.

Claim 6

The data transmission system of claim 1 further comprising: a scrambler receiving the digital data for scrambling the data, the scrambled data being supplied to the grouping means, whereby the grouping means will be provided with nonrepetitive successive data patterns.

Claim 7

In a data transmission system for sending digital data between a transmitter and a receiver over a transmission link by establishing predetermined phase differences and predetermined amplitude levels in a carrier signal during successive modulation periods representative of preselected data combinations, a demodulator at the receiver for detecting said phase differences and said amplitude levels to restore the digital data to its original format which comprises: means responsive to the received modulated carrier signal for providing a multibit digital output as a function of the phase of said carrier signal during a modulation period relative to the phase of the carrier signal during the immediately preceding modulation period, said multibit digital output representing portions of said preselected data combinations; means at the demodulator for varying the amplitude of said received modulated carrier signal; means responsive to said varied amplitude carrier signal for providing a magnitude output signal corresponding to the amplitude of said amplitude varied carrier signal during each modulation period; means responsive to the level of said magnitude output signal for generating a digital output signal representing the remaining portions of said preselected data combinations; and means responsive to the level of said magnitude output signal for generating a gain selection command for varying the gain of said amplitude varying means to accurately correspond said amplitude varied carrier signal with said predetermined amplitude levels.

Claim 8

In a data transmission system for sending digital data between a transmitter and a receiver over a transmission link by establishing predetermined phase differences and predetermined amplitude levels in a carrier signal during successive modulation periods representative of preselected data combinations, a demodulator at the receiver for detecting said phase differences and said amplitude levels to restore the digital data to its original format which comprises: means responsive to the received modulated carrier signal for providing a multibit digital output as a function of the phase of said carrier signal during a modulation period relative to the phase of the carrier signal during the immediately preceding modulation period, said multibit digital output representing portions of said preselected data combinations; means at the demodulator for varying the amplitude of said received modulated carrier signal; means responsive to said varied amplitude carrier signal for providing a magnitude output signal corresponding to the amplitude of said amplitude varied carrier signal during each modulation period; means responsive to the level of said magnitude output signal for generating a digital output signal representing the remaining portions of said preselected data combinations; and means responsive to the level of said magnitude output signal for generating a gain selection command for varying the gain of said amplitude varying means to accurately correspond said amplitude varied carrier signal with said predetermined amplitude levels.

Claim 9

The system of claim 6 wherein said amplitude varying means comprises: a feedback amplifier receiving said modulated carrier signal, said feedback amplifier having a control terminal adapted to vary the gain of said amplifier as a function of control signals applied to said control terminal.

Claim 10

The system of claim 7 wherein said gain selection command generating means comprises: means responsive to the level of said magnitude output signal for providing a digital magnitude signal the value of Which is varied as a function of whether the magnitude output signal is above or below said predetermined amplitude levels; means for time integrating the digital magnitude signals; and means for applying said integrated signals to the control terminal of said feedback amplifier.

Claim 11

The system of claim 8 wherein said gain varying means further comprises: means responsive to the level of said magnitude output signal being substantially above the highest of the predetermined amplitude levels to bypass said time integrating means and provide a rapid gain decrease signal to the control terminal of said feedback amplifier.

Claim 12

The data transmission system of claim 6 wherein the carrier signal is provided with a first amplitude level representing a first data bit value and a second amplitude level representing a second data bit value and wherein said digital output signal generating means comprises: means for generating a digital signal representing said first data bit value when said magnitude output signal is above a predetermined detection level; and means for generating a digital signal representing said second data bit value when said magnitude output signal is below said predetermined detection level.

Claim 13

The data transmission system of claim 10 wherein said predetermined detection level is approximately midway between said first and said second amplitude levels.

Claim 14

The data transmission system of claim 11 wherein the amplitude range of said magnitude output signal is divided into four zones; the first zone being below said first amplitude level, the second zone being between said first amplitude level and said detection level, the third zone being between said detection level and said second amplitude level, the fourth zone being above said second amplitude level, said gain selection command generating means comprising: means for generating a gain control signal which increases the gain of said amplitude varying means when said magnitude output signal is in said first or third zones; and means for generating a gain control signal which decreases the gain of said amplitude varying means when said magnitude output signal is in said second or fourth zones.

Claim 15

The data transmission system of claim 12 wherein there is a fifth amplitude zone, the fifth amplitude zone being substantially above said second amplitude level, said gain selection command generating means further comprising: means for generating a gain control signal which rapidly decreases the gain of said amplitude varying means when said magnitude output signal is in said fifth amplitude zone.

Claim 16

In a data transmission system for sending digital data between a transmitter an a receiver over a transmission link, the combination which comprises: modulating means at the transmitter for continuously grouping the digital data into multibit words of equal length and for generating a phase and amplitude modulated carrier signal in which the phase of the carrier signal between adjacent modulation periods is representative of first preselected digital data combination subgroups within each of the words, and the amplitude of the carrier signal during each modulation period is representative of second preselected digital data combinations within each subgroup wherein each such second preselected data combination corresponds to a predetermined amplitude level; means at the transmitter for applying the phase and amplitude modulated carrier signal to the transmission link; means at the receiver for detecting said phase differences and for generating a digital signal representative of said preselected multibit subgroup data patterns; means at the receiver for varying the amplitude of said modulated carrier signal; means responsive to said amplitude varied signal for generating a magnitude output signal corresponding to the amplitude of said amplitude varied carrier signal; means responsive to the level of said magnitude output siGnal for generating a digital output signal representing the selected data combination within said subgroups; and means responsive to the level of said magnitude output signal for generating a gain selection command for varying the gain of said amplitude varying means to accurately correspond the amplitude of said amplitude varied carrier signal with said predetermined amplitude levels.

Claim 17

In a data transmission system for sending digital data between a transmitter an a receiver over a transmission link, the combination which comprises: modulating means at the transmitter for continuously grouping the digital data into multibit words of equal length and for generating a phase and amplitude modulated carrier signal in which the phase of the carrier signal between adjacent modulation periods is representative of first preselected digital data combination subgroups within each of the words, and the amplitude of the carrier signal during each modulation period is representative of second preselected digital data combinations within each subgroup wherein each such second preselected data combination corresponds to a predetermined amplitude level; means at the transmitter for applying the phase and amplitude modulated carrier signal to the transmission link; means at the receiver for detecting said phase differences and for generating a digital signal representative of said preselected multibit subgroup data patterns; means at the receiver for varying the amplitude of said modulated carrier signal; means responsive to said amplitude varied signal for generating a magnitude output signal corresponding to the amplitude of said amplitude varied carrier signal; means responsive to the level of said magnitude output siGnal for generating a digital output signal representing the selected data combination within said subgroups; and means responsive to the level of said magnitude output signal for generating a gain selection command for varying the gain of said amplitude varying means to accurately correspond the amplitude of said amplitude varied carrier signal with said predetermined amplitude levels.

Claim 20

The method of claim 15 comprising the additional step of: rapidly decreasing the amplitude of the amplitude varied carrier signal when the detected amplitude is substantially above the second amplitude level.

Claim 21

In a data transmission system for sending digital data between a transmitter and a receiver over a transmission link by establishing predetermined phase differences and amplitude levels in a carrier signal during successive modulation periods representative of preselected data combinations which comprises: a modulator at the transmitter which includes: means for continuously grouping serial digital data into words of three binary bits; means for providing N90* phase differences in a carrier signal during successive modulation periods, where N 0, 1, 2 or 3, so that each of four possible data pattern subgroups corresponds to a predetermined phase difference relative to the phase of the carrier in an immediately preceding modulation period; and means for establishing one of two predetermined amplitude levels for the carrier signal during successive modulation periods so that each data combination of a subgroup corresponds to one of said two distinct predetermined carrier amplitude levels; and filter means connected in the signal transmission link, the filter being characterized as having a passband width of about 1/T Hz. And a center frequency of fo; where T is the modulation period; fo is the carrier signal frequency, and T/2 is cycles per second.

Claim 22

In a data transmission system for sending digital data between a transmitter and a receiver over a transmission link by establishing predetermined phase differences and amplitude levels in a carrier signal during successive modulation periods representative of preselected data combinations which comprises: a modulator at the transmitter which includes: means for continuously grouping serial digital data into words of three binary bits; means for providing N90* phase differences in a carrier signal during successive modulation periods, where N 0, 1, 2 or 3, so that each of four possible data pattern subgroups corresponds to a predetermined phase difference relative to the phase of the carrier in an immediately preceding modulation period; and means for establishing one of two predetermined amplitude levels for the carrier signal during successive modulation periods so that each data combination of a subgroup corresponds to one of said two distinct predetermined carrier amplitude levels; and filter means connected in the signal transmission link, the filter being characterized as having a passband width of about 1/T Hz. And a center frequency of fo; where T is the modulation period; fo is the carrier signal frequency, and T/2 is cycles per second.