FM Communication system

• US 4,517,562 A
• Filed: 03/29/1982
• Issued: 05/14/1985
• Est. Priority Date: 10/23/1979
• Status: Expired due to Fees

• Current Assignee: Cooper Industries, Inc. (Eaton Corporation PLC.)
• Original Assignee: Mcgraw-Edison Company (Eaton Corporation PLC.)
• Inventors: Martinez, Louis
• Primary Examiner(s): Yusko, Donald J.
• Application Number:
  US06/362,888
• Time in Patent Office: 1,142 Days
• Field of Search: 370/11, 340/825.07, 340/825.52, 340/825.08, 455/49, 455/51, 455/53, 455/56, 455/57, 455/2, 455/45, 455/228, 455/353, 179/5 R
• US Class Current: 340/12.5
• CPC Class Codes: G05D 23/1905 associated with tele control
• CPC Class Codes: H04H 20/36 for AM broadcasts
• CPC Class Codes: H04Q 9/14 Calling by using pulses

Abstract

Communication system for either public or private electric power load management and distribution automation, and the like, wherein subcarrier signals are sent to a plurality of remotely located receivers and transmitters using an existing standard FM broadcast station. The broadcast signal is detected by a receiver which filters out the subcarrier component of the broadcast signal. The radio frequencies of the plurality of remotely located transmitters and receivers are closely spaced and synthesized from the frequency of the broadcast subcarrier and their time of transmission, digital bit streams, and message frames are all synchronized from the subcarrier signal. The FM broadcast station thereby orchestrates all communication activity to and from the plurality of remote locations to optimize traffic flow and maximize a priori information to all components to significantly increase reliability.

Claims

1. A radio communication system for selectively addressing and controlling a plurality of remotely located apparatus comprising in combination:

(a) central controller means adapted to generate digital address and control messages for transmission to at least one local FM radio broadcast station,

(b) a local FM radio broadcast station coupled to receive said digital address and control messages from said controller, and including means for generating inaudible modulated subcarrier signals derived from a subcarrier signal of a subcarrier oscillator, the subcarrier signal being modulated by digital address and control signals responsive to said address and control messages and synchronized to said subcarrier oscillator and by occasional special sync signals generated at said local FM radio broadcast station, and for adding its normally broadcasted audio program signal to the modulated subcarrier signal and providing a frequency modulated RF signal in response thereto,

(c) a plurality of remotely addressable digital radio receivers controlling a plurality of external apparatus and tuned to receive and demodulate the frequency modulated signal of said broadcast station and comprising means to detect and lock onto said subcarrier signal, to detect special sync signals, to decode said address &

control signals synchronously with said subcarrier signal and special sync signals, and selectively respond thereto to control said apparatus.

2. The communication system of claim 1 wherein said central controller comprises:

(a) central receiver adapted to detect and phase-lock to said subcarrier of signal broadcast station to derive therefrom special sync signals and address &

control signals,

(b) digital address and control generator means connected to the output of said central receiver and adapted to receive commands from external apparatus and reformat them into digital address and control messages and "transmit sync" request signals, said "transmit sync" requests being sent at long time intervals, such as hourly,

(c) a modem coupled to the output of said digital address &

control generator to transmit said output to said FM radio station.

3. The central controller of claim 2 wherein said digital address &

control generator further compares the address &

control signals received from said central receiver to the address &

control messages which it generates in order to detect errors and generate corrected output signals for subsequent rebroadcasting.

4. The communication system of claim 1 wherein said FM radio broadcast station modification comprises:

(a) a subcarrier oscillator providing an inaudible subcarrier frequency,

(b) a digital encoder means for generating synchronized digitally coded output signals at a first output,

(c) a phase modulator means connected to said subcarrier oscillator and said digital encoder to phase modulate the subcarrier signal with the digitally coded output signals,

(d) summing means for adding the phase modulated signal to the normal audio program signal,

(e) frequency modulation means connected to said summing means for modulating the RF carrier signal prior to transmission as an FM broadcast signal.

5. The broadcast station system of claim 4 wherein said digital encoder receives digital address &

control messages from said central controller means through a telephone interface modem.

6. The communication system of claim 1 wherein said FM radio broadcast station modification comprises:

(a) a first frequency divider means connected to output of a subcarrier oscillator to derive therefrom a digital bit stream clock rate,

(b) a second frequency divider means driven by said first frequency divider to generate a message frame rate,

(c) a first input of a sync frame generator means connected to output of said second frequency divider and a second sync frame generator input connected to one output of a digital encoder means to generate therefrom a special sync code output signal upon receipt of a sync enable signal from said encoder,

(d) said digital encoder means being coupled to receive the output of said first frequency divider at a first input and the output of said sync frame generator at a second input, and said digital address &

control signals and sync request signals at a third input, said digital encoder being a means to generate synchronized digitally coded output signals at a first output, and sync enable signals at a second output,

(e) a phase modulator means connected to said subcarrier oscillator and said digital encoder to phase modulate the subcarrier with the digitally coded output signals,

(f) summing means for adding the phase modulated signal to the normal audio program signal, and

(g) frequency modulation means connected to said summing means for modulating the RF carrier signal prior to transmission as an FM broadcast signal.

7. The communication system of claim 1 wherein said remotely located radio receiver comprises:

(a) receiving means to detect FM broadcast signals from said broadcast station,

(b) demodulating means connected to output of said receiving means for demodulating said broadcast signals, and

(c) filter and detection means connected to said demodulating means for separating the subcarrier signal from the audio program signal, and for phase demodulating the subcarrier signal, and to derive reference frequencies including a digital clock signal,

(d) a digital address detector and control signal decoder means connected to the output of said filter and detection means to synchronously detect and compare address portion of said carries signal to individual or group address stored therein and to decode the control portion of said signal and output control signals to external apparatus,

whereby said references frequencies may be used to synchronize and control an optional return-link transmitter.

8. The communication system of claim 1 wherein said remotely located radio receiver further comprises arbitrator means connected to the output of said decoder means to provide manual or automatic control.

9. The communication system of claim 1 wherein said radio receivers are connected to the electrical power wiring of buildings to receive therefrom their energizing power and the radio signals from said broadcast station, said building power wiring acting effectively as an antenna, said receivers being adapted to provide control signals on output connecting wires to external apparatus to control their function selectively upon command of said address &

control signal.

10. The communication system of claim 1 wherein said receivers are packaged in a form identical to conventional electrical circuit breakers and wherein said receiver derives its power and receives its radio signals through the terminals of said circuit breaker.

11. The control receiver of claim 10 wherein said circuit breaker package includes a conventional circuit breaker adapted to provide power interruption upon receipt of a command from said copackaged receiver.

12. The communication system of claim 1 wherein said radio receiver and external apparatus comprise:

(a) a multiregister watt-hour meter to measure power consumption on a plurality of sets of indicating dials as engaged by a selector mechanism,

(b) said radio receiver mounted behind said plural dial sets to selectively engage any one of said plurality dials as commanded by said address &

control signal.

13. The communication system of claim 1 wherein said external apparatus comprises a smart thermostat.

14. The communication system of claim 1 wherein external apparatus comprises an audio-visual alert and display to warn of emergency conditions.

15. The communication system of claim 1 having a plurality of local FM radio broadcast stations, each coupled to receive said digital signals from said controller, and including means for generating inaudible subcarrier signals derived from a subcarrier oscillator and modulated by the digital signals and special sync signals, and adding its normally broadcasted audio program signal to the generated subcarrier signals and providing a frequency modulated RF signal in response thereto.

16. The communication system of claim 15 wherein at least two of said plurality of local FM radio broadcast stations broadcast on the same FM radio broadcast channel.

17. The communication system of claim 16 wherein said at least two of said plurality of local FM radio broadcast stations broadcast in separate geographic areas, which areas are contiguous, whereby said radio receivers will lock on to the stronger FM signal as a result of the FM capture effect.

18. A narrowband bidirectional radio communication system comprising:

(a) a plurality of independent paired radio receiver and transmitter means wherein said receivers are adapted to detect broadcasted subcarrier modulated by address &

control signals from an existing standard FM broadcast station in its forward link, and said transmitter means are adapted to accept RF reference and sync signals from its companion receiver and to accept reply message signals from message sources connected at their respective inputs and to transmit said reply message signals synchronously on a corresponding plurality of closely spaced radio carrier frequencies to a central station receiver selectively in response to coded address &

control signals transmitted from the local FM radio broadcast station;

(b) central station receiver means being adapted to receive said radio reply signals simultaneously at said plurality of closely spaced return-link radio carrier frequencies, and to simultaneously detect said RF reference and sync signals from said broadcast station and employ them to synchronously demodulate the radio signals from said plurality of remote transmitter means,

(c) central controller means adapted to generate digital address &

control signals synchronized to said sync signals broadcasted by said FM radio station, and

(d) at least one local FM radio broadcast station adapted to generate and broadcast special sync signals derived from a inaudible subcarrier oscillator and adapted to receive and broadcast digital address &

control signals received from said central control means by adding its normally broadcasted audio program signal to the subcarrier signal and then frequency modulating the broadcast RF signal.

19. The communication system of claim 18 wherein said radio receiver comprises a single conversion synchronous design comprising receiving antenna means to detect said broadcast signal connected to RF amplifier means which drives:

(a) the series combination of a bandpass filter coupled to mixer means driving an intermediate frequency (IF) limiter-amplifier means driving a phase detector means driving an amplifier driving a first low pass filter means coupled to a sync detector which drives a frequency divider chain means, and driving second low pass filter means which drives a voltage controlled oscillator means which provides the RF frequency and drives said frequency divider chain means having plural outputs,

(b) one output of said divider chain means being connected to a second input of said mixer means and a second output of said divider being connected to a second input of said phase detector means in a phase-lock loop arrangement whereby said oscillator is forced to operate at a frequency precisely equal to the frequency of said broadcast station, or a multiple of it,

(c) wherein the output from said first low pass filter comprises the desired data signal and wherein plural outputs from said frequency devider chain comprise the desired bit stream clock and message frame rate signals,

(d) external circuit means connected to receive said output signals from said synchronous superheterodyne receiver so as to process said signals and selectively respond thereto to control said external apparatus.

20. The bidirectional communication system of claim 18 wherein said central station receiver comprises;

(a) a first antenna to detect broadcasted signals and drive a digital control receiver phase-locked to the carrier frequency of said broadcast station to derive therefrom a radio reference frequency, sync signals, bit stream and message frame rates, and address &

control signals,

(b) a conventional central radio receiver RF section including a second antenna to detect signals from said remote transmitters and a radio frequency amplifier having a programmable gain control connected to the output of said second antenna, and a first mixer connected to output of said amplifier, and a local oscillator phase-locked to a multiple of the reference radio frequency from said digital control receiver to thereby generate a stable intermediate frequency (IF) output from said mixer in the frequency range required by the FFT processor,

(c) a fast Fourier transform (FFT) processor connected to the IF output of said central radio receiver to compute power spectral density distributions to thereby determine the presence or absence of signals on each of the plurality of frequencies transmitted from the corresponding plurality of remote transmitters, said FFT processor being programmed to operate using time windows, input data sampling rates, and reference radio frequency synchronized from said digital control receiver output signals.

21. The bidirectional communication system of claim 18 wherein said return transmitter means comprises:

(a) a first antenna to detect broadcasted signals and drive a digital control receiver phase-locked to the carrier frequency of said broadcast station to derive therefrom a radio reference frequency, frame sync signals, time slot signals, clocking signals and address and control signals,

(b) a digital frequency control circuit coupled to receive said clocking signals and said radio reference frequency from said digital control receiver and providing a control signal in response thereto,

(c) an oscillator coupled to receive the control signal from said digital frequency control circuit for providing a reference frequency,

(d) a data buffer coupled to receive said time slot signals, frame sync signals and clocking signals, providing a synchronized bit output signal representative of bits within frames synchronized to said clocking and frame sync signals,

(e) an amplifier modulator coupled to receive said reference frequency and synchronized bit signals, said modulator amplifying and modulating said signals,

(f) an amplifier for amplifying said modulated signals from said amplifier modulator, and

(g) a second antenna for transmitting said amplified signals.

22. The narrowband bidirectional radio communication system of claim 18 having a plurality of local FM radio broadcast stations, each adapted to generate and broadcast special sync signals derived from an inaudible subcarrier oscillator and adapted to receive and broadcast digital address and control signals received from said central control means by adding its normally broadcasted audio program signal to the subcarrier signal and then frequency modulating the broadcast RF signal.

23. The communication system of claim 22 wherein at least two of said plurality of local FM radio broadcast stations broadcast on the same FM radio broadcast channel.

24. The communication system of claim 23 wherein said at least two of said plurality of local FM radio broadcast stations broadcast in separate geographic areas, which areas are contiguous, whereby said radio receivers will lock on to the stronger FM signals as a result of the FM capture effect.