Pulse or digital communications – Systems using alternating or pulsating current
Patent
1998-03-23
2000-09-19
Ghebretinsae, Temesghen
Pulse or digital communications
Systems using alternating or pulsating current
370442, 370522, H04L 2700
Patent
active
061223239
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to methods and apparatuses for the use of electromagnetic waves for information transfer and more particularly to methods and apparatuses for the use of electromagnetic waves for digital information transfer.
BACKGROUND OF THE INVENTION
There are several principal modulation methods for electromagnetic signals used in communications. The ones that are most widely used are frequency modulation (FM), amplitude modulation (AM), pulse width modulation (PWM) and phase modulation (PM). There have also been some other less widely used methods for transmitting and receiving information by means of electromagnetic signals. The demands of modern information transfer, in particular computer networking and multi-media communications, have increased the need to transmit more and more information on limited channels of communication. With the ever increasing capacity of digital computers, there is an ever increasing demand for modulation methods to enhance the volume of digital data that can be transmitted and received.
Methods have been developed for increasing the amount of information that can be transmitted and received. One such method is described in U.S. Pat. No. 4,387,455 to Schwartz. This method utilizes several different modulation systems at the same time over the same channel. However, this method uses FM and AM modulation and requires several cycles for each digital bit. Similarly, the device disclosed in U.S. Pat. No. 4,103,238 to Deming, provides for three modulation patterns to be transmitted simultaneously on a single carrier wave. Again, multiple cycles are required for each digital bit. The deficiencies of these methods are typical of efforts to increase the amount of information transmitted.
The method disclosed in U.S. Pat. No. 4,584,692 to Yazuka relies on the same common modulation methods but introduces polarity modulations as a means of enhancing the amount of information that can be transmitted. The polarity of the waves is modulated to encode information and then the original wave and the modulated wave are compared to allow decoding of the information. This results in a modest increase in the amount of information that can be transmitted over a single signal.
Various methods designed specifically for digital information transfer provide some enhancement of the data transfer capabilities. The method disclosed in U.S. Pat. No. 4,001,728 to Schneider is a method of transmitting digital signals through the use of pulse width modulation on an incremental ramp wave. A method of transmitting multiple digital signals on a single carrier wave is disclosed in U.S. Pat. No. 4,347,616 to Murakami. Another method providing for the simultaneous transmission of multiple digital signals independently modulated is disclosed in U.S. Pat. No. 3,805,191 to Kawai.
The method disclosed in U.S. Pat. No. 3,890,620 to Toman provides for the modulation of a carrier wave at prescribed time intervals with digital information. This method, however, points up the limitations of attempts to enhance existing methods of digital information transfer. Incoming digital data must first be stored and then it is recalled for transmission at a rate compatible with the carrier wave modulation. The receiver then extracts the digital information from the signal by synchronization with the transmitter. The resultant signal is subject to interference at both the carrier frequency and the modulation frequency.
U.S. Pat. No. 5,364,536 to Tsujimoto discloses a means of modulating a "data burst" on a carrier signal. Tsujimoto uses a modulation scheme to add a sync burst to the modulated carrier signal. This is accomplished by taking a delayed version of the data burst and the non-delayed data burst and taking the difference. This creates an artificial null in the frequency spectrum of the signal. This null spectrum sync burst is added to the signal before signal transmission. Thus for Tsujimoto, the sync burst becomes a signature burst for identifying the data burst. This method, as with the
REFERENCES:
patent: 3805191 (1974-04-01), Kawai
patent: 3890620 (1975-06-01), Toman
patent: 4001728 (1977-01-01), Schneider
patent: 4103238 (1978-07-01), Deming
patent: 4347616 (1982-08-01), Murakami
patent: 4387455 (1983-06-01), Schwartz
patent: 4584692 (1986-04-01), Yazuka
patent: 4766589 (1988-08-01), Fisher
patent: 5220557 (1993-06-01), Kelley
patent: 5274672 (1993-12-01), Weiss
patent: 5364536 (1994-11-01), Tsujimoto
patent: 5369669 (1994-11-01), Tombal et al.
patent: 5390185 (1995-02-01), Hooijmans et al.
Ghebretinsae Temesghen
International Automated Systems, Inc.
Nelson J. David
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