 Communication apparatus |
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| Spread aloha CDMA data communications |
| Even though different codes are not required for multiple access in CDMA channels, the question ... |
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| Electric slider |
| It is an object of the invention to provide an improved slider of the above-outlined type which ... |
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| System for preventing collision of vehicles |
| Accordingly, it is an object of this invention to provide an improved system for preventing ... |
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| Smoke and heat detector alarm |
| This invention relates generally to the field of alarm systems, and more particularly, is directed ... |
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| Door alarm system |
| OF THE INVENTION The door alarm system of the invention is for a door 1 (FIGS. 1 to 4) rotatably ... |
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| Armour-piercing high-explosive projectile with cartridge |
| I claim: 1. An armour-piercing high-explosive projectile comprising a body portion attached to a ... |
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| Contoured dental posts |
| Accordingly, it is an object of the present invention to provide an improved dental post. A further ... |
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| Process and apparatus for treating teeth |
| OF THE PREFERRED EMBODIMENT Referring now to the drawing, FIG. 1 shows a tooth 1 the volume of ... |
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| High performance acoustical cleaning apparatus for teeth |
| What is claimed is: 1. A dental hygiene device for cleaning teeth and interdental and gingival ... |
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Method and apparatus for pulse angle modulation
| Details |
Inventors: Andren, Carl F.; Mosley, Jr., William H.; Sanders, David E.;
Assignee: E-Systems, Inc. (Dallas, TX)
Primary Examiner: LaRoche; Eugene R.
Assistant Examiner: Paxman; W. R.
Attorney, Agent or Firm: Crowder, Jr.; Albert M.
A method and apparatus for phase modulating a carrier signal to convey an information signal (12) such that the carrier signal has a constant amplitude envelope. A Hilbert transform signal (14) of the information signal (12) is produced. The signals (12, 14) are sampled to produce signals (16, 18), which represent cartesian coordinate values. The cartesian coordinate values are then converted into equivalent polar vectors (20-36) which have both an amplitude (R) and an angle (.theta.). The polar vector quantity (R, .theta.) is converted into two unity amplitude vectors (A, B). The unity amplitude vectors (A, B) are offset from the polar vector quantity by an angle the cosine of which is proportional to the amplitude of the polar vector (R). The carrier signal is sequentially phase modulated phase angles of the unity amplitude vectors (A, B) for each sample period of the information signal. This modulation procedure maintains a constant amplitude envelope for the carrier signal and makes possible simultaneous demodulation of a plurality of carrier signals in a single demodulation channel. |
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DETAILED DESCRIPTION The present invention comprises a method and apparatus for phase modulating a carrier such that the modulated carrier has a constant envelope characteristic and has a zero carrier component without spectrum spreading of the IF signal.
The carrier modulation technique described herein is entitled Pulse Angle (PANG) Modulation and is especially applicable for use in a conferencing communication system.
In the present invention an input signal, usually audio, is processed through a Hilbert transformer which is a circuit that produces continuous output that has a 90 degree phase shift for each signal component of the input audio signal.
The combination of the audio signal and the Hilbert transformed audio signal make up a cartesian coordinate set for the audio signal at each sample point thereof.
In general, both the original audio signal and the Hilbert transform are sampled at a standard rate, such as 8 KHZ, and the samples are combined geometrically as cartesian vectors to produce a resultant vector (R) and a corresponding angle .
theta.
.
In other words the audio signals are sampled and the vectors therefrom are converted from a cartesian coordinate system into a polar coordinate system having the resultant vector R and the angle .
theta.
.
These quantities are illustrated in FIG.
1.
The vector circle 10 has vector R extending outward and rotated at an angle of .
theta.
from the positive X axis.
In order to maintain a constant envelope characteristic the modulation technique of the present invention produces two vectors of unity amplitude, A and B, for each of the pairs of samples corresponding to the resultant vector R.
The unity vectors A and B are each phase offset from the resultant vector R by an angle of .
phi.
.
This is an angle which is proportional to the amplitude of the resultant vector R and is defined as being the angle whose cosine is R/2 where R is in the range from zero to two.
From the above discussion it can be seen that the relations of the vectors are given by the following equations where X is the amplitude of the audio signal at the sample time and Y is the amplitude of the Hilbert transform signal at the sample time
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Telecommunications 
