Patent US4011407A successfully refreshed from Google Patents.
US4011407A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Narrow-band eight-phase modem
Assignee: RCA Corp
•
Filing: 1976-02-26
•
Granted: 1977-03-08
•
Expires: 1996-02-26
Abstract
Abstract An eight-phase modem is described in which a 2900 H z carrier has eight phases each representing one of eight tri-bit symbols 000 through 111. The phase modulated carrier is restricted for transmission to a frequency band of 2900 ± 50 H z , and the modem can carry four time-division-multiplex 75-baud teletype channels at 250 bits per second at the upper end of a telephone voice channel without interfering with normal voice use of the channel. Or, the modem can carry eight channels at 500 bits per second in a frequency band of 2900 ± 100 H z . The modem operates reliably despite a carrier frequency translation or shift of up to ± 5 H z in the communications path. The modem extracts a carrier cycle spike from the received signal during each symbol period, and uses the spike to synchronize a locally-generated reference signal, and compares each spike with the reference signal to derive the corresponding phase-modulated tri-bit symbol information.
Inventors
- 👤 Nicholas DiSanti
- 👤 Frank Oster
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 12:09
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/18; H04L27/22; H04L27/227; H04L27/2271; H04L27/2272; H04L27/20; H04L27/2032; H04L27/2035; H04L27/2042; H04L27/2046
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
159 words
A receiver for a transmitted eight-phase carrier in which each phase represents a tri-bit symbol, and the carrier is amplitude modulated at the symbol frequency, comprising amplitude demodulator means to derive a symbol frequency pulse wave from said received carrier, means timed by said symbol frequency pulse wave to generate symbol spikes each having the phase of one cycle of the received carrier during a respective symbol period, local means to generate reference waves, phase lock means to compare each symbol spike with said reference waves and correct the phase of said reference waves if they are out of phase with the received carrier, frequency synchronizing means responsive to correction signals in said phase lock means to correct the frequency of the reference waves if they are out of synchronism with the received carrier, and information demodulating means to compare each symbol spike with said reference waves to determine the corresponding symbol phase and the corresponding three information bits.
Claim 2
Dependent Claim
159 words
A receiver for a transmitted eight-phase carrier in which each phase represents a tri-bit symbol, and the carrier is amplitude modulated at the symbol frequency, comprising amplitude demodulator means to derive a symbol frequency pulse wave from said received carrier, means timed by said symbol frequency pulse wave to generate symbol spikes each having the phase of one cycle of the received carrier during a respective symbol period, local means to generate reference waves, phase lock means to compare each symbol spike with said reference waves and correct the phase of said reference waves if they are out of phase with the received carrier, frequency synchronizing means responsive to correction signals in said phase lock means to correct the frequency of the reference waves if they are out of synchronism with the received carrier, and information demodulating means to compare each symbol spike with said reference waves to determine the corresponding symbol phase and the corresponding three information bits.
Claim 3
Dependent Claim
36 words
A receiver as defined in claim 1 wherein said reference waves have a frequency equal to eight times the frequency of the received carrier to represent the timing of the eight phases of the received carrier.
Claim 4
Dependent Claim
27 words
A receiver as defined in claim 2 wherein said reference waves include a demodulation reference wave, an early pulse reference wave and a late pulse reference wave.
Claim 5
Dependent Claim
43 words
A receiver as defined in claim 3 wherein said phase lock means includes means to compare each symbol spike with said early and late pulse reference waves, and for each coincidence cause an advancing or retarding of the phase of the reference waves.
Claim 6
Dependent Claim
49 words
A receiver as defined in claim 4 wherein said frequency synchronizing means includes means to count and compare the number of coincidences of said symbol spikes with said early and late pulse reference waves, and in case of imbalance to increase of decrease the frequency of said reference waves.
Claim 7
Dependent Claim
33 words
A receiver as defined in claim 5 wherein each symbol spike is derived from a cycle of the carrier occurring about thirty-five percent of the symbol period time following a carrier envelope closure.
Claim 8
Dependent Claim
189 words
A receiver for a transmitted eight-phase carrier wave in which each phase represents a tri-bit symbol, and the carrier wave is amplitude modulated at the symbol frequency, comprising means to derive a symbol frequency pulse wave from said received carrier wave, means timed by said symbol frequency pulse wave to generate symbol spikes each having the phase of one cycle of the received carrier wave during a respective symbol period, local means to generate a reference wave, an early pulse wave, and a late pulse wave, all having a frequency equal to eight times the frequency of the carrier wave. phase lock means to compare each symbol spike with said early and late pulse waves, and for each coincidence cause an advancing or retarding of the phase of said waves, frequency synchronizing means to count and compare the number of coincidences of said symbol spikes with said early and late pulses, and in cases of imbalance to increase or decrease the frequency of said waves, and demodulator means to compare each symbol spike with said reference wave to determine the corresponding symbol phase and the corresponding three information bits.
Claim 9
Dependent Claim
189 words
A receiver for a transmitted eight-phase carrier wave in which each phase represents a tri-bit symbol, and the carrier wave is amplitude modulated at the symbol frequency, comprising means to derive a symbol frequency pulse wave from said received carrier wave, means timed by said symbol frequency pulse wave to generate symbol spikes each having the phase of one cycle of the received carrier wave during a respective symbol period, local means to generate a reference wave, an early pulse wave, and a late pulse wave, all having a frequency equal to eight times the frequency of the carrier wave. phase lock means to compare each symbol spike with said early and late pulse waves, and for each coincidence cause an advancing or retarding of the phase of said waves, frequency synchronizing means to count and compare the number of coincidences of said symbol spikes with said early and late pulses, and in cases of imbalance to increase or decrease the frequency of said waves, and demodulator means to compare each symbol spike with said reference wave to determine the corresponding symbol phase and the corresponding three information bits.
Claim 10
Dependent Claim
289 words
A receiver for a transmitted eight-phase carrier wave in which each phase represents a tri-bit symbol, and the carrier wave is amplitude modulated at the symbol frequency, comprising means to translate a received carrier wave to a narrow spike wave having the same frequency and the same symbol phases as the received carrier wave, means to extract a symbol frequency pulse wave from said received carrier wave, means employing said extracted symbol frequency pulse wave to gate out one symbol spike from said spike wave about 35 percent after the beginning of each symbol period, a local oscillator and a frequency multiplying and dividing chain producing an output wave having a frequency eight times the frequency of the received carrier wave to represent the timing of the eight phases of the received carrier wave, means synchronized from said chain to generate early pulse and late pulse waves having a frequency eight times the frequency of the received carrier wave, means to compare each symbol spike with said early and late pulse waves, and for each coincidence cause a retarding or advancing of the phase of the output of said chain, means to count and compare the number of coincidences of said symbol spikes with said early and late pulses, and in case of imbalance to periodically cause a continuing decrease or increase in the frequency of the output of the chain to lock the frequency to eight times the frequency of the received carrier, means coupled to the output of the chain to derive signals representing the eight phases of the carrier wave frequency, and means to compare each symbol spike with said signals representing the eight phases to determine the symbol phase and the corresponding three information bits.
Claim 11
Dependent Claim
289 words
A receiver for a transmitted eight-phase carrier wave in which each phase represents a tri-bit symbol, and the carrier wave is amplitude modulated at the symbol frequency, comprising means to translate a received carrier wave to a narrow spike wave having the same frequency and the same symbol phases as the received carrier wave, means to extract a symbol frequency pulse wave from said received carrier wave, means employing said extracted symbol frequency pulse wave to gate out one symbol spike from said spike wave about 35 percent after the beginning of each symbol period, a local oscillator and a frequency multiplying and dividing chain producing an output wave having a frequency eight times the frequency of the received carrier wave to represent the timing of the eight phases of the received carrier wave, means synchronized from said chain to generate early pulse and late pulse waves having a frequency eight times the frequency of the received carrier wave, means to compare each symbol spike with said early and late pulse waves, and for each coincidence cause a retarding or advancing of the phase of the output of said chain, means to count and compare the number of coincidences of said symbol spikes with said early and late pulses, and in case of imbalance to periodically cause a continuing decrease or increase in the frequency of the output of the chain to lock the frequency to eight times the frequency of the received carrier, means coupled to the output of the chain to derive signals representing the eight phases of the carrier wave frequency, and means to compare each symbol spike with said signals representing the eight phases to determine the symbol phase and the corresponding three information bits.
References Cited (Backward Citations)
US3737578A
Cited
US3753114A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-03-07 | 1980-09-06 | 1981-03-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-03-07 | 1984-09-06 | 1985-03-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-03-07 | 1988-09-06 | 1989-03-08 | $7700.00 | Window Closed / Lapsed |