Modulators – Pulse or interrupted continuous wave modulator – Including stabilization or alternatively distortion – noise...
Reexamination Certificate
1998-08-28
2001-02-27
Mis, David (Department: 2817)
Modulators
Pulse or interrupted continuous wave modulator
Including stabilization or alternatively distortion, noise...
C332S106000, C329S311000, C329S370000, C455S259000, C455S295000
Reexamination Certificate
active
06194978
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and apparatus for efficiently transmitting digital information with an analog carrier for wireless communications. More specifically, this invention relates to a method of interrupting an analog carrier so that the absence of the carrier directly corresponds to the digital information being transmitted.
BACKGROUND OF THE INVENTION
In the past most wireless communication systems used either frequency modulation (FM) and/or amplitude modulation (AM) to embed analog information within a carrier frequency. In recent years digital information has been transmitted using the same modulation techniques or derivatives of those techniques.
When using either AM, FM or a combined AM/FM modulation technique the carrier frequency is the center point of the overall bandwidth which the signal occupies. Due to the modulation of information onto the carrier frequency the modulated carrier signal occupies bandwidth above and below the carrier frequency. Because the allocation of the radio spectrum is fixed only a limited number of signals can be transmitted in the allotted radio bandwidth.
A number of modern digital technologies increase the overall flow of information transmitted within a given segment of the radio spectrum by using data compression, information packeting, and other digital formats and modulation schemes. While signal throughput and integrity are increased these technologies continue to rely on modulation techniques which occupy sections of bandwidth. The same radio spectrum bandwidth limitations described above again limit the number of signals or channels of information that can be wirelessly transmitted.
Therefore, in light of the foregoing deficiencies in the prior art, the applicant's invention is herein presented.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for wirelessly transmitting and receiving digital information using an analog carrier where the required bandwidth is limited to approximately the frequency of the analog carrier signal. The method is called interrupt modulation and consists of interrupting an un-modulated carrier signal so the interruptions correspond directly to the digital information to be transmitted. The digital information is used to control a high speed analog switch which either passes or blocks the un-modulated carrier signal thereby converting the digital information to time domain information. In the preferred embodiment the un-modulated analog carrier signal is interrupted to directly correspond with the time length of the high segments of the digital information.
To receive and demodulate or decode the digital information wirelessly transmitted the interrupt modulated signal is rectified to create a digital pulse waveform that represents the original digital information only inverted. Once the digital pulse waveform is detected it can easily be conditioned and inverted to identically match the digital information originally transmitted. Digital information is transferred by the time lengths of the absence of the analog carrier signal. Due to reliance on the absence of the carrier or absence information, interrupt modulation provides substantial self-filtering with any additional filtering needed capable of being done simply and inexpensively. The absence information provided by interrupt modulation alleviates or eliminates many conventional wireless problems such as multi-path interference, signal drop off and imaging distortion.
These along with other objects and advantages of the present invention will become more readily apparent from a reading of the detailed description taken in conjunction with the drawings and the claims.
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