Pulse or digital communications – Receivers – Particular pulse demodulator or detector
Reexamination Certificate
1999-03-16
2001-05-22
Bocure, Tesfaldet (Department: 2734)
Pulse or digital communications
Receivers
Particular pulse demodulator or detector
C375S260000
Reexamination Certificate
active
06236691
ABSTRACT:
FIELD OF THE INVENTION
This invention is the field of filters for electromagnetic signals and in particular the field of filter systems for separating the components of multiple frequency signals.
BACKGROUND OF THE INVENTION
The conventional method for separating out an information signal of a specific frequency from signals of other frequencies, which together with the specific frequency comprise a combined signal, and from noise, is a filter comprised of inductor and capacitor circuits. Such filters interfere with and alter the wave and, therefore, fail to reproduce the wave in the pure form in which it was transmitted. The bandwidth of the retrieved wave is substantially larger than the bandwidth of the wave as transmitted. It should be noted, however, that the increase in the bandwidth is not a function of the propagation of the wave. It is a function of the filtering process.
Another problem with conventional filters is that they require multiple cycles of the input signal in order to ramp up. Until the ramping up is complete, the filtering will be ineffective. This substantially limits the amount of data that can be transmitted by multiple frequency signals and extracted by conventional filters. A filtering method is needed which will allow a single cycle to be filtered and data to be accurately extracted from each cycle.
The inventor herein has had three prior patents issued which disclose methods and apparatuses for digital information transfer. They are U.S. Pat. Nos. 5,517,528, 5,640,422, and 5,689,529 to Johnson, and are hereinafter referred to as the “prior related patents”. Also, a prior application, U.S. application Ser. No. 08/879,755, has been filed by the inventor herein which discloses certain methods and apparatuses for filtering electromagnetic signals. The present application discloses an additional method and an additional apparatus for filtering electromagnetic signals.
Continuous combined information waves which are simultaneously generated at multiple frequencies, combined and transmitted as a single information signal are disclosed in the prior related applications and patents. Advanced filter systems which allow the utilization of the capabilities of the inventions disclosed in the prior related applications and patents are also disclosed in the prior related applications and patents. However, a filter method and apparatus is needed which will provide for minimizing the complexity of the signal separation process, minimizing the bandwidth of the extracted multiple frequency components, and enhancing the accuracy of the extracted data.
The limitations of conventional signal extraction methods also impose substantial limitations on digital information storage technology. Current digital technology allows only one bit per cycle to be transferred from a read/write head to a magnetic storage device such as a hard drive, a magnetic disc, or an external magnetic drive. These current storage systems operate using analog functions. In addition, as data is transferred, the spacing between the storage medium and the read/write head changes, distorting or degrading the signal amplitude. When the distance between the head and the storage medium changes, the energy transfer rate is inversely proportional to the square of the distance. Therefore, any deviation of the read/write head changes the amplitude of the waves. For this reason digital recording procedures can measure only amplitude change. No information is derived from actual amplitudes.
One objective of the present invention is to provide an improved and simplified method and apparatus for filtering and separating combined multiple frequency signals.
Another objective of the present invention is to provide for separation of individual frequency components of multiple frequency signals while minimizing interference and minimizing the bandwidth of each of the extracted components, thus further enhancing the accuracy of the data transmitted by each of the extracted wave components.
A still further objective of the present invention is to provide a method and apparatus for separating multiple frequency combined signals while minimizing bandwidth distortion.
A still further objective of the present invention is to provide a method and apparatus for filtering simultaneous multiple frequency signals of distinct frequencies which is simpler, more reliable, and less costly than conventional methods.
A still further objective of the present invention is to provide a filter method and apparatus which will increase the storage capacity of magnetic digital storage devices and will enhance the accuracy of data transfer between a read/write head and a magnetic storage device.
A still further objective of the present invention is to provide an effective filter method and apparatus which is adapted for use with the information transfer receiver apparatuses disclosed in the prior related applications.
SUMMARY OF INVENTION
The present invention provides an improved method and apparatus for filtering and separating a received multiple frequency combined signal into its various frequency components. It may be used in conjunction with the digital information transfer inventions disclosed in the prior related applications and patents.
The method of the present invention comprises a method of extracting information from an electromagnetic signal which is comprised of two or more waves of distinct frequencies. Under certain preferred embodiments the combined information wave is comprised of a reference wave with a known wave form, amplitude, frequency and phase and one or more component information waves with known wave forms and frequencies and a known phase relationship to the reference wave. The frequencies of each of the component information waves is distinct from the frequency of each of the other component information waves and the reference wave. For certain preferred embodiments the frequency of the reference wave is sufficiently less than the frequencies of the component information waves so that it can be separated from the rest of the combined information wave by a typical narrow bandpass filter. The ratio of the amplitude of each cycle of each respective component information wave to the amplitude of the reference wave is a function of the digital data being transmitted by that component information wave.
Rather than consisting of an arrangement of narrow band pass filters and other necessary components as in a conventional filter system or consisting of the special filters disclosed in the prior related applications and patents, certain preferred embodiments of the method of the present invention simply requires one or more computer circuits which perform a mathematical analysis on the received combined signal.
The first step in extracting the information from the combined information wave as received by the receiving apparatus is to store the combined information wave for processing. The combined information wave is then passed through a narrow bandpass filter with frequency selected to match the frequency of the reference wave, thereby extracting the reference wave from the combined information wave. Next, the zero crossing points of the reference wave are determined by locating points on the wave which are half way between the positive apex and the negative apex of the wave. Once the zero crossing points of the reference wave have been determined, since the frequencies and the phase relationship of the component information waves with respect to the reference wave are known the zero crossing points of each of the component information waves can be determined.
Amplitude equations are then generated for each of the component information wave zero crossing points. Each of these equations is in the form of the sum of the unknown amplitude of each non-zero component information wave as multiplied by its known phase factor at that point which together equal the observed amplitude at the component information wave zero crossing point in question. This process results in the generation of linear amplitude equations with
Bocure Tesfaldet
International Automated Systems, Inc.
Nelson J. David
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