Re-broadcast system for a plurality of AM signals

• US 5,471,642 A
• Filed: 01/28/1994
• Issued: 11/28/1995
• Est. Priority Date: 01/28/1994
• Status: Expired due to Fees

• Current Assignee: Martinez Barbara A, Martinez Michael G
• Original Assignee: James K. Palmer
• Inventors: Palmer, James K.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): FAILE, ANDREW I
• Application Number:
  US08/188,030
• Time in Patent Office: 669 Days
• Field of Search: 455/11.1, 455/12.1, 455/13.1, 455/15, 455/16, 455/17, 455/20, 455/22, 455/24, 455/73, 455/234.1, 455/253.2, 455/103, 375/3
• US Class Current: 455/17
• CPC Class Codes: H04B 7/15535 Control of relay amplifier gain amplifier gain control in general H03G3/00; gain control reducing self - or loop interference H04B7/15578
• CPC Class Codes: H04H 20/02 Arrangements for relaying broadcast information
• CPC Class Codes: H04H 20/59 for emergency or urgency
• CPC Class Codes: H04H 20/61 for local area broadcast, e.g. instore broadcast

Abstract

Apparatus for simultaneously receiving a plurality of AM signals of widely differing strengths on a set of carrier frequencies and for re-broadcasting the AM signals at equalized strengths at either the original carrier frequencies or at a set of carrier frequencies that are offset from the original from the received frequencies by a constant difference. Regardless of whether the re-broadcast carriers are offset, the system includes provision for interrupting the re-broadcast signals by an audio message of general interest or public safety.

Claims

1. Apparatus for simultaneously receiving a plurality of AM signals of widely differing strengths on carriers having frequencies of f₁, . . . f_i, . . . f_N where N is an integer greater than 1 and for re-broadcasting the AM signals at an equal strength and at the original carrier frequencies, said apparatus comprising in combination:

a receiving antenna;

an input bus connected to said receiving antenna;

an output radiator;

an output bus connected to said output radiator;

a plurality of circuit boards, one for each of said plurality of AM signals, each of said plurality of circuit boards connected to said input bus and to said output bus, the circuit board for carrier frequency f_i including

a local oscillator producing an output having a frequency equal to f_i ±

f_o, where f_o is a chosen intermediate frequency (IF) which is the same for all of the circuit boards;

a down-converter connected to said input bus and connected to said local oscillator and producing an amplitude modulated carrier of frequency f_o as an output;

an IF amplifier connected to receive the output of said down-converter, having a controllable gain, and producing an output;

first means connected to said IF amplifier for controlling its gain in inverse relation to the strength of the carrier of frequency f_i, whereby the gain is reduced if the carrier of frequency f_i is strong, and whereby the gain is increased if the carrier of frequency f_i is weak;

an up-converter connected to said IF amplifier and connected to said local oscillator for mixing the output of said IF amplifier of frequency f_o with the output of said local oscillator of frequency f_i ±

f_o to produce on an output terminal an output of frequency f_i having a signal strength that is substantially uniform for all of said plurality of circuit boards; and

,

second means connecting the output terminal of said up-converter to said output bus.

2. The apparatus of claim 1 wherein said apparatus further comprises a preamplifier interposed between said input bus and said down-converter.

3. The apparatus of claim 1 wherein said second means further comprise a radio frequency (RF) amplifier interposed between the output terminal of said up-converter and said output bus.

4. Apparatus for simultaneously receiving a plurality of AM signals of widely differing strengths on carriers having frequencies of f₁, . . . f_i, . . . f_N, where N is an integer greater than 1, for re-broadcasting the AM signals at an equal strength and at the original carrier frequencies, and for selectively broadcasting on the original carrier frequencies a common modulating signal, said apparatus comprising in combination:

a receiving antenna;

an input bus connected to said receiving antenna;

an output radiator;

an output bus connected to said output radiator;

a plurality of circuit boards, one for each of said plurality of AM signals, each of said plurality of circuit boards connected to said input bus and to said output bus, the circuit board for carrier frequency f_i including

a local oscillator producing an output having a frequency equal to f_i ±

f_o where 1≦

i≦

N and where f_o is a chosen intermediate frequency (IF) which is the same for all of the circuit boards;

a down-converter connected to said input bus and connected to said local oscillator and producing an amplitude modulated carrier of frequency f_o as an output;

an IF amplifier connected to receive the output of said down-converter, having a controllable gain, and producing an output;

first means connected to said IF amplifier for controlling its gain in inverse relation to the strength of the carrier of frequency f_i, whereby the gain is reduced if the carrier of frequency f_i is strong, and whereby the gain is increased if the carrier of frequency f_i is weak;

a first up-converter connected to said IF amplifier and connected to said local oscillator for mixing the output of said IF amplifier of frequency f_o with the output of said local oscillator of frequency f_i ±

f_o to produce on an output terminal an output of frequency f_i having a signal strength that is substantially uniform for all of said plurality of circuit boards;

an oscillator generating an output signal having a frequency equal to the intermediate frequency f_o ;

a second up-converter connected to said oscillator for receiving the output signal at frequency f_o of said oscillator, connected to said tunable local oscillator for receiving the output of said tunable local oscillator at frequency f_i ±

f_o, and producing in response thereto a carrier of frequency f_i as an output;

a modulator connected to said second up-converter for receiving the output of said second up-converter, and responsive to an applied modulating signal to produce an amplitude modulated carrier of frequency f_i ; and

,

switching means connected to said first up-converter, connected to said modulator, and connected to said output bus for selectively applying the output of said first up-converter and the output of said modulator to said output bus.

5. Apparatus for simultaneously receiving a plurality of AM signals of widely differing strengths and carriers having frequencies of f₁, . . . f_i, . . . f_N, where N is an integer greater than 1, and for re-broadcasting the AM signals at an equal strength at frequencies f₁ +Δ

, . . . f_i +Δ

, . . . f_N +Δ

, where Δ

is a chosen constant offset frequency, said apparatus comprising in combination;

a receiving antenna;

an input bus connected to said receiving antenna;

an output radiator;

an output bus connected to said output radiator;

a plurality of circuit boards, one for each of said plurality of AM signals, each of said plurality of circuit boards connected to said input bus and to said output bus, the circuit board for carrier frequency f_i including

a first local oscillator producing an output having a frequency equal to f_i ±

f_o where 1≦

i≦

N and where f_o is a chosen intermediate frequency (IF) which is the same for all of the circuit boards;

a down-converter connected to said input bus and connected to said first local oscillator and producing an amplitude modulated carrier of frequency f_o as an output;

an IF amplifier connected to receive the output of said down-converter, having a controllable gain, and producing an output;

first means connected to said IF amplifier for controlling its gain in inverse relation to the strength of the carrier of frequency f_i, whereby the gain is reduced if the carrier of frequency f_i is strong, and whereby the gain is increased if the carrier of frequency f_i is weak;

a second local oscillator producing an output having a frequency equal to f_i ±

f_o +Δ

;

an up-converter connected to said IF amplifier and connected to said second local oscillator for mixing the output of said IF amplifier of frequency f_o with the output of said second local oscillator of frequency f_i +f_o +Δ

to produce on an output terminal an output of frequency f_i +Δ

having a signal strength that is substantially uniform for all of said plurality of circuit boards; and

,

second means connecting the output terminal of said up-converter to said output bus.