Digital modulate/demodulate system
阅读：911发布：2021-11-25
专利汇可以提供Digital modulate/demodulate system专利检索，专利查询，专利分析的服务。并且A digital information signal modulating system is disclosed which increases the carrying capacity of a given designator band by approximately 2. The disclosure illustrates how a quadrature phase-shift keyed system having four signal states can be converted to a system having nine signal states.，下面是Digital modulate/demodulate system专利的具体信息内容。
1. A digital information signal modulating system comprising means to provide a two-state NRZ digital waveform having a known clock period, means to provide a carrierfrequency wave, means to apply said digital waveform to double-phase-shift modulate said carrier wave at a known substantially constant amplitude, means to create a three-state waveform representative of said digital waveform including partial-response filter means having an input and an output, and means to apply said modulated wave to said input, said filter means having a bandwidth so limited that in a time interval equal to one clock period of said digital waveform said modulated wave traversing it cannot swing more than approximately one-half said amplitude as seen at said output.
2. A system according to claim 1 including substantially linear amplifier means coupled to the output of said filter means.
3. A system according to claim 1 including non-linear amplifier means coupled between the output of said carrier frequency means and the input of said filter means.
4. A digital information signal modulating system according to claim 1 including means to provide a second two-state NRZ digital waveform having said known clock period and temporally interleaved with said first-named digital waveform, means to provide a second carrier-frequency wave of like frequency to said first-named carrier-frequency wave and off-set 90* in phase relative thereto, means to apply said second digital waveform to double-phase-shift modulate said second carrier-frequency wave at said known amplitude, means to combine said second modulated wave with said first-named modulated wave, and means to apply said combined modulated waves to said input of said filter means.
5. A system according to claim 4 including substantially linear amplifier means coupled to the output of said filter means.
6. A system according to claim 4 including non-linear amplifier means having an input and an output, means to apply said combined modulated waves to said amplifier input, and means to couple said amplifier output to said input of said filter means.
7. A digital information signal modulating system comprising in combination means providing first and second signals representing respective first and second NRZ digital waveforms each having a known clock period, the first signal modulating a carrier selectively at one or the other of two first phase states 180* apart and the second signal modulating said carrier selectively at one or the other of two second phase states 180* apart and each respectively angularly spaced 90* from one of said first phase states, said carrier having substantially the same amplitude in each of said phase states, and partial-response filter means having an input coupled to receive the modulated carrier signals, said filter means having a bandwidth so limited that in a time interval equal substantially to said clock period a switching of either of said digital waveforms from one Of its digital states to the other reduces from full-amplitude substantially to zero in the output of said filter the amplitude of the carrier modulated thereby.
8. A system according to claim 7 including substantially linear amplifier means coupled to the output of said filter.
9. A system according to claim 7 including non-linear amplifier means between said modulated carrier signals and said filter means.
10. An amplitude-modulated phase modulation system comprising a quadrature-phase-shift-keyed (QPSK) system for phase modulation at a known substantially constant amplitude with a bit stream at a given clock rate split into two parallel data waveforms each at one-half of the input bit-rate, partial-response filter means having an input and an output, and means to apply the output of said QPSK system to said input, said filter means having a bandwidth so limited that in a time interval equal to two clock periods of said input bit stream a modulated wave from said QPSK system cannot swing more than approximately one-half said amplitude as seen at said output.
11. A system according to claim 10 including substantially linear amplifier means coupled to the output of said filter means.
12. A system according to claim 10 including non-linear amplifier means coupled between the output of said QPSK system and the input of said filter means.
13. A 9-state phase-modulated signal on a pair of quadrature-related carrier waves of like frequency in which each of said carrier waves has three mutually-exclusive modulation states one only of which is a substantially zero-amplitude state, the simultaneous occurrence of the zero-amplitude state of both of said carrier waves constituting one of said nine states, the simultaneous occurrence of a non-zero amplitude modulation state of one of said carrier waves with the zero-amplitude state of the other constituting a unique one of said nine states, and the simultaneous occurrence of a non-zero amplitude modulation state of one of said carrier waves with a non-zero amplitude modulation state of the other carrier wave constituting by vector addition another unique one of said nine states.
14. A method of digital pulse-code modulating a carrier wave to produce a 9-state phase-modulated signal, comprising the steps of providing said carrier wave in two components phased substantially 90* apart, providing a bit stream at a known clock rate and splitting said bit stream into two parallel wave-forms each at one-half said clock rate, double-phase-shift modulating each of said components at a known substantially constant amplitude with a unique one of said waveforms, and band-limiting said modulated components so that in a time interval equal substantially to two clock periods a modulated wave cannot swing more than approximately one-half its said amplitude, whereby each modulated carrier wave component can at a given instant occupy one only of first and second states of like amplitude and respective opposite phases and a third state of essentially zero-amplitude, and said components in combination will provide a 9-state signal in which the simultaneous occurrence of the zero-amplitude state of both of said carrier waves constitutes one of said 9 states, the simultaneous occurrence of a non-zero amplitude modulation state of one of said carrier waves with the zero-amplitide state of the other constitutes a unique one of said nine states, and the simultaneous occurrence of a non-zero amplitude modulation state of one of said carrier waves with a non-zero amplitude modulation state of the other carrier wave constitutes by vector addition another unique one of said nine states.
15. A method according to claim 14 in which said modulated carrier wave components are combined and then band limited.
16. A method according to claim 14 in which each of said modulated carrier wave components is separately band-limited, and thereafter they are combined.
17. A method according to claim 14 in which said modulated carrIer wave components are combined prior to being band-limited, the combined modulated carrier wave signal is amplified non-linearly, and after amplification said combined signal is band-limited to provide said 9-state signal.
18. A method according to claim 14 in which said 9-state signal is linearly amplified.
19. A digital information signal modulating system comprising means to provide a two-state NRZ digital waveform having a known clock period, means to provide a carrier-frequency wave, means to apply said digital waveform to double-phase-shift modulate said carrier wave at a known substantially constant amplitude, waveform modifying means to create a (2+n)- state waveform representative of said digital waveform, (''''n'''' being an integer), said waveform modifying means including partial-response filter means having an input and an output, and means to apply said modulated wave to said input, said filter means having a bandwidth so limited that in a time interval equal to one clock period of said digital waveform said modulated wave traversing it cannot swing more than approximately one-nth of said amplitude as seen at said output.
20. In a digital information transfer system having means to convert an original two-state digital signal having a known clock rate to a n-level signal where ''''n'''' is an integer greater than 2, means to transmit the n-level signal, means to receive the transmitted n-level signal, and n-level to 2-level converter means for converting the n-level signal to a two-level digital signal the information content of which is a substantial replica of the information content of said original signal, said n-level to 2-level converter means comprising, logic means for creating said two-level digital signal in response to sampling of said n-level signal at a clock rate corresponding to the clock rate of said original signal, signal input means to said logic means for establishing n-1 boundary levels each lying between a pair of adjacent levels in said received n-level signal, and clock input means to said logic means for effecting said sampling.
21. A system according to claim 20 in which said means to receive includes clock-pulse generator means responsive to said n-level signal for generating a train of clock pulses at a rate corresponding to said known clock rate, said generator means comprising an input for said n-level signal, clock oscillator means having a parameter that is variable for controlling the frequency of oscillation, means responsive to crossings of said n-level signal over a prescribed level to generate reference signals for said parameter, and means to apply said reference signals to said parameter to adjust the frequency of said oscillator to correspond with the clock frequency of said original digital signal.
22. In a digital information transfer radio link system according to claim 20 employing suppressed carrier modulation without transmitting a pilot signal to enable the receiver means to recover the carrier, carrier recovery means comprising n-phase extraction circuit means to sample the received waveform and provide a series of pulse-like waves temporally spaced in phase (360/n) *, local oscillator means controllable in frequency to oscillate in the region including the frequency of the suppressed carrier, means to multiply the frequency of the pulse-like waves by ''''n,'''' means to multiply the frequency of the local oscillator by ''''n,'''' comparator means for comparing the two multiplied signals and generating a control signal for the oscillator means, and means to apply the control signal to adjust the oscillator frequency to the frequency of the suppressed carrier.
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