Fifty channel television transmitter

• US 5,148,279 A
• Filed: 03/18/1991
• Issued: 09/15/1992
• Est. Priority Date: 03/18/1991
• Status: Expired due to Fees

• Current Assignee: William D. Gabor
• Original Assignee: William D. Gabor
• Inventors: Gabor, William D.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Powell, Mark R.
• Application Number:
  US07/671,061
• Time in Patent Office: 547 Days
• Field of Search: 358/186, 455/103, 455/109, 455/114, 455/118, 455/17, 455/19, 455/20, 455/25, 455/7
• US Class Current: 348/723
• CPC Class Codes: H04N 5/38 Transmitter circuitry for the transmission of television signals according to analogue transmission standards H04N5/14 takes precedence
• CPC Class Codes: H04N 7/20 Adaptations for transmission via a GHz frequency band, e.g. via satellite

Abstract

A multi-channel microwave transmission system that employs a single antenna. A local oscillator set at a predetermined frequency provides a single to the local oscillator port of a mixer; the signal first passes through a narrow bandpass filter. The input port of the mixer receives a signal carrying fifty television channels; a microwave absorption filter and a bandpass filter positioned between the source of the multi-channel signal and the input port prevent the predetermined local oscillator frequency from intermodulating the multi-channel signal. A bandpass filter having a notch that rejects the predetermined local oscillator frequency is positioned between the output port of the mixer and the power amplifier stage of the device. In the power amplifier stage, another bandpass filter having a notch rejecting the predetermined frequency of the local oscillator is provided. The power amplifier stage feeds an inexpensive parabolic antenna of the type sold in retail outlets. The mixer converts the incoming television signals to microwave frequencies using the superheterodyne principle.

Claims

1. A device that simultaneously transmits a plurality of television channels, comprising;

a local oscillator that generates a predetermined frequency;

a mixer having an input port, a local oscillator port in electrical communication with said local oscillator, and an output port;

a microwave absorption filter electrically disposed between a source of television signals and the input port of said mixer;

a bandpass filter electrically disposed between the output port of said mixer and a transmitting antenna;

said bandpass filter having a rejection trap for the predetermined frequency generated by said local oscillator;

whereby said mixer converts the television signals to microwave side bands for transmission over an antenna;

whereby said absorption filter protects said source of television signals from intermodulation by said predetermined frequency of said local oscillator; and

whereby said bandpass filter and said rejection trap prevent said predetermined local oscillator frequency from being transmitted by said antenna.

2. The device of claim 1, further comprising a bandpass filter electrically disposed between said source of said television signals and said input port of said mixer, said bandpass filter passing the frequencies occupied by said television signals and rejecting the predetermined frequency of said local oscillator.

3. The device of claim 2, further comprising a narrow bandpass filter, electrically disposed between said local oscillator and said mixer local oscillator port, that passes said predetermined frequency and that blocks all other frequencies.

4. The device of claim 3, further comprising a power amplifier means electrically disposed between said output port of said mixer and said antenna.

5. The device of claim 4, further comprising a bandpass filter, disposed in and forming a part of said power amplifier means, having a notch for rejection of said local oscillator predetermined frequency.

6. The device of claim 5, further comprising an amplifier means electrically disposed between said local oscillator and said narrow bandpass filter.

7. The device of claim 6, further comprising a directional coupler electrically disposed between said narrow bandpass filter and the local oscillator port of said mixer.

8. The device of claim 5, further comprising a step switch attenuator electrically disposed between said microwave absorption filter and said mixer.

9. The device of claim 8, further comprising a cable television distribution amplifier electrically disposed between said source of television signals and said microwave absorption filter.

10. The device of claim 9, further comprising a step attenuator electrically disposed between said source of television signals and said distribution amplifier.

11. The device of claim 10, further comprising a final power amplifier electrically disposed between said bandpass filter disposed in said power amplifier means and said antenna.

12. The device of claim 11, further comprising a directional coupler electrically disposed between said final power amplifier and said antenna.

13. The device of claim 12, further comprising at least one voltage follower buffer circuit electrically disposed between said directional coupler of said power amplifier means and the attenuator electrically disposed between said source of television signals and said microwave absorption filter.

14. The device of claim 13, wherein said at least one voltage follower buffer circuit includes a meter circuit, an alarm signal circuit and an automatic power level control circuit, said meter circuit including a meter calibrated to read the operating power range of said final power amplifier, said alarm signal circuit adapted to activate an alarm at a predetermined threshold of power loss from said power amplifier means, and said power level control circuit adapted to control said attenuator electrically disposed between said source of television signals and said microwave absorption filter.