 Polygraphic encryption-decryption communications system |
| In accordance with this invention, an electronic memory is loaded with a binary matrix of "0" or "1"... |
|
| Alternating variable delay control arrangement and method for push-pull audio transducers |
| What is claimed as new and desired to be secured by Letters Patent of the United States is: 1. A ... |
|
| Loudspeaker with heat radiating hole and electrical device employing the same |
| It is therefore an object of the present invention to provide a loudspeaker superior in space ... |
|
| Low range loudspeaker system |
| What is claimed is: 1. An audio speaker system comprising the usual driven primary radiator having ... |
|
| Passive radiator cooled electronics/heat sink housing for a powered speaker |
| What is claimed is: 1. An electronics/heat sink housing for a powered speaker having a speaker ... |
|
| Audio signal processing apparatus |
| What is claimed is: 1. In combination, four conducting means, source and selector means for ... |
|
| Linear phase response multi-way speaker system |
| What is claimed is: 1. A multi-way speaker system comprising a low pass filter, a high pass filter ... |
|
| Sound reproducing with remote amplifying transducer |
| OF PREFERRED EMBODIMENTS With reference now to the drawing and more particularly FIG. 1 thereof, ... |
|
| Audio signal processing system |
| What is claimed is: 1. An audio signal processing system of the type for generating ambient effects,... |
|
| Method of improving the acoustics of a hall |
| I claim: 1. A method of improving the acoustics of a room having a performance area in which sound ... |
|
|
Modulator having direct digital synthesis for broadband RF transmission
| Details |
Inventors: Graham, Hatch;
Assignee: Stanford Telecommunications, Inc. (Sunnyvale, CA)
Primary Examiner: Mis; David
Assistant Examiner:
Attorney, Agent or Firm: Townsend and Townsend Khourie and Crew
A modulator for data transmitted in a reverse channel or upstream spectrum in a cable transmission system requires a single frequency translation from baseband to a selected RF channel, thus eliminating conventional intermediate frequency (IF) translation. The modulator requires fewer components than the conventional modulator while eliminating nonlinearity, noise, and delay introduced by the IF upconversion. In a preferred embodiment, the modulator includes a serial to parallel differential quadrature phase shift keying encoder with transversal FIR filters and interpolation filters connecting the phase shift keyed data to a single mixer stage for directly translating the baseband signal to an RF (e.g., 5-40 MHz) channel spectrum. |
|
DETAILED DESCRIPTION In accordance with the invention, a modulator is provided for use in the 5-40 MHz reverse channel and which requires a single frequency translation from baseband to RF, thus eliminating the conventional intermediate frequency, IF, translation.
The modulator requires fewer components than a conventional modulator, while eliminating nonlinearity, noise, and delay introduced by the IF upconversion.
In a preferred embodiment, the modulator includes filter means for receiving and digitally sampling an input data stream and providing a sampled data stream.
Mixer means, including a tunable oscillator, receives the sampled data stream and provides an RF data stream in selected frequency bands.
A digital to analog converter then receives the RF data stream and converts the digital data to an analog signal for direct application to a cable transmission system.
In one embodiment, the filter means includes means for translating serial input data into parallel data and then encoding the data using differential quadrature phase shift keying.
The filter means further includes transversal finite impulse response (FIR) filter means for digitally sampling the in-phase and quadrature phase encoded data, and an interpolation filter provides additional control data for the sampled encoded data.
The tunable oscillator in the mixer means includes a numerically controlled oscillator for providing modulation signals for in phase and quadrature phase mixers which step the encoded data directly to an RF signal having a frequency in the spectrum of the reverse channel, such as 5-40 MHz.
The invention and objects and features thereof will be more readily apparent from the following detailed description and appended claims when taken with the drawing.
|
|
Audio Signal Processing 
