WO1997023056A1 - Power line audio system - Google Patents

Power line audio system Download PDF

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Publication number
WO1997023056A1
WO1997023056A1 PCT/US1996/020173 US9620173W WO9723056A1 WO 1997023056 A1 WO1997023056 A1 WO 1997023056A1 US 9620173 W US9620173 W US 9620173W WO 9723056 A1 WO9723056 A1 WO 9723056A1
Authority
WO
WIPO (PCT)
Prior art keywords
audio
power line
carrier signal
modulated
signal
Prior art date
Application number
PCT/US1996/020173
Other languages
French (fr)
Inventor
Chandrakant Bhailalbhai Patel
Jack R. Harford
Thomas O. Bohlander
Original Assignee
Elcom Technologies Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Elcom Technologies Corporation filed Critical Elcom Technologies Corporation
Priority to AU12948/97A priority Critical patent/AU1294897A/en
Publication of WO1997023056A1 publication Critical patent/WO1997023056A1/en

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/54—Systems for transmission via power distribution lines
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R5/00—Stereophonic arrangements
    • H04R5/04—Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5404—Methods of transmitting or receiving signals via power distribution lines
    • H04B2203/5416—Methods of transmitting or receiving signals via power distribution lines by adding signals to the wave form of the power source
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5429—Applications for powerline communications
    • H04B2203/5437—Wired telephone
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5429—Applications for powerline communications
    • H04B2203/545—Audio/video application, e.g. interphone

Definitions

  • This invention relates to a system for transmitting audio signals over a power line, and more particularly to a system in which the two components of stereo audio signals, developed in a two-channel transmitter, are transmitted along a power line separately and received by a two-channel receiver.
  • Telephone audio signals have been transmitted over power lines.
  • the audio frequency in a telephone is below 3.4 kHz.
  • the frequency requirements are as high as 20 kHz.
  • Conventional stereo transmission uses two channels. However, the two channels left (L) and right (R) are combined and transmitted as (L+R) and (L-R) to permit listeners who have monaural systems to hear the full content of the transmission in monaural. This leads to the problem of cross-talk if there is any inequality in receiving (L+R) and (L-R).
  • a power line audio system constructed in accordance with the present invention, includes a power line, a transmitter and a receiver.
  • the transmitter has first and second channels.
  • the first transmitter channel includes means for supplying a first audio signal, means for supplying a first audio carrier signal having a first frequency, means for modulating the first audio carrier signal with the first audio signal, and means for filtering the modulated first audio carrier signal.
  • the second transmitter channel includes means for supplying a second audio signal, means for supplying a second audio carrier signal having a second frequency, means for modulating the second audio carrier signal with the second audio signal, and means for filtering the modulated second audio carrier signal.
  • the transmitter also has a coupler for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal to the power line for transmission along the power line.
  • the receiver has a coupler for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal transmitted along the power line from the power line.
  • the receiver also has first and second channels.
  • the first channel in the receiver includes means for passing the filtered, modulated first audio carrier signal transmitted along the power line, means for demodulating the filtered, modulated first audio carrier signal transmitted along the power line to detect the first audio signal, and means for supplying the detected first audio signal to a first speaker.
  • the second channel includes means for passing the filtered, modulated second audio carrier signal transmitted along the power line, means for demodulating the filtered, modulated second audio carrier signal transmitted along the power line to detect the second audio signal, and means for supplying the detected second audio signal to a second speaker.
  • Figure 1 is a functional block diagram of an exemplary transmitter in accordance with the present invention.
  • Figure 2 is a functional block diagram of one channel of an exemplary receiver in accordance with the present invention.
  • L and R are included in the transmitter and receiver portions of a system constructed in accordance with the present invention.
  • Two channels are included because the power line environment dictates what happens to the individual carriers. Thus, one carrier can have much more attenuation than the other. However, this difference does not matter as long as the received signal is above the FM capture sensitivity. In other words, as long as the FM signal remains within the r.f. dynamic range of the system, the audio levels remain constant.
  • the two carriers L and R are transmitted separately, rather than combined as (L+R) and (L-R), in order to eliminate non-linearity in L and R that can result in cross-talk (i.e.
  • the two carriers are transmitted separately, they are received at the receiver with perfect linearity. Thus, cross-talk is eliminated and pure L and pure R carriers are received. Because the L and R carriers have different frequencies and, therefore, are put on the power line separately, there is little, if any, mixing of the L and R carriers during transmission or at the receiver, as long as there is enough separation between the two carrier frequencies.
  • a potential problem with a system, constructed in accordance with the present invention is that there might be a delay difference between the two channels. To minimize this problem, the two transmission carrier frequencies are selected such that they are as close as possible, yet separated sufficiently to minimize or eliminate the possibility of mixing. Although the delay difference might not be entirely eliminated, it can be reduced to a level that the listener will not notice or will tolerate.
  • the input audio for each channel is not received from a controlled level source, the input can be gain adjusted using a limiting amplifier for automatic gain control (AGC).
  • AGC automatic gain control
  • the AGC for the gain control has a quick attack time but a slow delay time. Best results are achieved when the audio inputs are supplied from a controlled level source.
  • the transmitter portion of a power line audio system has a first channel LEFT (L) and a second channel RIGHT (R).
  • the first transmitter channel LEFT includes means for supplying a first audio signal.
  • Such means can include an audio input line 10, an AGC/amplifier circuit 12 and a pre-emphasis circuit 14 which conditions the first audio signal.
  • the first transmitter channel LEFT also includes means for supplying a first audio carrier signal having a first frequency (fj), for example 3.58 MHz, and means for modulating the first audio carrier signal with the first audio signal.
  • a modulator 50 serves as a source of the first audio carrier signal and to modulate the first audio carrier signal by the first audio signal.
  • the first transmitter channel LEFT further includes means for filtering the modulated first audio carrier signal.
  • Such means can include an amplifier 52 and a bandpass filter 54 which, as indicated, fo ⁇ n a power line driver 70.
  • the second transmitter channel RIGHT includes means for supplying a second audio signal.
  • Such means can include an audio input line 20, an AGC/amplifier circuit 22 and a pre-emphasis circuit 24 which conditions the second audio signal.
  • the second transmitter channel RIGHT also includes means for supplying a second audio carrier signal having a second frequency ), for example 4.5 MHz, and means for modulating the second audio carrier signal with the second audio signal.
  • a modulator 60 serves as a source of the second audio carrier signal and to modulate the second audio carrier signal by the second audio signal.
  • the second transmitter channel RIGHT further includes means for filtering the modulated second audio carrier signal.
  • Such means can include an amplifier 62 and a bandpass filter 64 which, as indicated, form a power line driver 80.
  • the transmitter also has a coupler 90 for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal to a power line for transmission along the power line.
  • the receiver portion of a power line audio system constructed in accordance with the present invention, has first and second channels, only one of which is illustrated.
  • the other receiver channel is identical to the one illustrated in Figure 2 except that the two channels are arranged to separately process the two audio carrier signals, as indicated by the fi ) notations in Figure 2, and detect the two audio signals.
  • the receiver has a coupler 110 for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal transmitted along the power line from the power line.
  • Each of the receiver channels has means for passing one of the filtered, modulated first audio carrier signal transmitted along the power line or the filtered, modulated second audio carrier signal transmitted along the power line.
  • Such means can include a bandpass filter 120, a limiter amplifier 125 and another bandpass filter 130.
  • Each of the receiver channels also includes means for demodulating one of the filtered, modulated first audio carrier signal transmitted along the power line to detect the first audio signal or the filtered modulated second audio carrier signal transmitted along the power line to detect the second audio signal.
  • Such means can include a demodulator 140 to detect the respective audio signals.
  • Each of the receiver channels further includes means for supplying the detected audio signal to a speaker.
  • Such means can include a de-emphasis circuit 142 and an amplifier 145 which conditions the detected signal.
  • a volume and bass/treble control can be provided in the receiver portion of the system.

Abstract

An audio system for transmitting stereo audio signals over a power line and having two channels in the transmitter and two channels in the receiver, so that the two components of the stereo audio signals are transmitted and received separately.

Description

POWER LINE AUDIO SYSTEM
FIELD OP THE INVENTION
This invention relates to a system for transmitting audio signals over a power line, and more particularly to a system in which the two components of stereo audio signals, developed in a two-channel transmitter, are transmitted along a power line separately and received by a two-channel receiver.
BACKGROUND OF THE INVENTION
Telephone audio signals have been transmitted over power lines. The audio frequency in a telephone is below 3.4 kHz. For audio in the form of music, for example, the frequency requirements are as high as 20 kHz. Conventional stereo transmission uses two channels. However, the two channels left (L) and right (R) are combined and transmitted as (L+R) and (L-R) to permit listeners who have monaural systems to hear the full content of the transmission in monaural. This leads to the problem of cross-talk if there is any inequality in receiving (L+R) and (L-R). SUMMARY OF THE INVENTION
A power line audio system, constructed in accordance with the present invention, includes a power line, a transmitter and a receiver. The transmitter has first and second channels. The first transmitter channel includes means for supplying a first audio signal, means for supplying a first audio carrier signal having a first frequency, means for modulating the first audio carrier signal with the first audio signal, and means for filtering the modulated first audio carrier signal. The second transmitter channel includes means for supplying a second audio signal, means for supplying a second audio carrier signal having a second frequency, means for modulating the second audio carrier signal with the second audio signal, and means for filtering the modulated second audio carrier signal. The transmitter also has a coupler for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal to the power line for transmission along the power line. The receiver has a coupler for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal transmitted along the power line from the power line. The receiver also has first and second channels. The first channel in the receiver includes means for passing the filtered, modulated first audio carrier signal transmitted along the power line, means for demodulating the filtered, modulated first audio carrier signal transmitted along the power line to detect the first audio signal, and means for supplying the detected first audio signal to a first speaker. The second channel includes means for passing the filtered, modulated second audio carrier signal transmitted along the power line, means for demodulating the filtered, modulated second audio carrier signal transmitted along the power line to detect the second audio signal, and means for supplying the detected second audio signal to a second speaker.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 is a functional block diagram of an exemplary transmitter in accordance with the present invention. Figure 2 is a functional block diagram of one channel of an exemplary receiver in accordance with the present invention.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
For 20 kHz audio transmission, wider FM deviation and transmission of two separate audio carriers, Left (L) and Right (R) channels are included in the transmitter and receiver portions of a system constructed in accordance with the present invention. Two channels are included because the power line environment dictates what happens to the individual carriers. Thus, one carrier can have much more attenuation than the other. However, this difference does not matter as long as the received signal is above the FM capture sensitivity. In other words, as long as the FM signal remains within the r.f. dynamic range of the system, the audio levels remain constant. The two carriers L and R are transmitted separately, rather than combined as (L+R) and (L-R), in order to eliminate non-linearity in L and R that can result in cross-talk (i.e. some of the L component occurring in R, and vice- versa). Because the two carriers are transmitted separately, they are received at the receiver with perfect linearity. Thus, cross-talk is eliminated and pure L and pure R carriers are received. Because the L and R carriers have different frequencies and, therefore, are put on the power line separately, there is little, if any, mixing of the L and R carriers during transmission or at the receiver, as long as there is enough separation between the two carrier frequencies. A potential problem with a system, constructed in accordance with the present invention, is that there might be a delay difference between the two channels. To minimize this problem, the two transmission carrier frequencies are selected such that they are as close as possible, yet separated sufficiently to minimize or eliminate the possibility of mixing. Although the delay difference might not be entirely eliminated, it can be reduced to a level that the listener will not notice or will tolerate.
If the input audio for each channel is not received from a controlled level source, the input can be gain adjusted using a limiting amplifier for automatic gain control (AGC). The AGC for the gain control has a quick attack time but a slow delay time. Best results are achieved when the audio inputs are supplied from a controlled level source.
Referring to Figure 1 , the transmitter portion of a power line audio system, constructed in accordance with the present invention, has a first channel LEFT (L) and a second channel RIGHT (R). The first transmitter channel LEFT includes means for supplying a first audio signal. Such means can include an audio input line 10, an AGC/amplifier circuit 12 and a pre-emphasis circuit 14 which conditions the first audio signal. The first transmitter channel LEFT also includes means for supplying a first audio carrier signal having a first frequency (fj), for example 3.58 MHz, and means for modulating the first audio carrier signal with the first audio signal. A modulator 50 serves as a source of the first audio carrier signal and to modulate the first audio carrier signal by the first audio signal. The first transmitter channel LEFT further includes means for filtering the modulated first audio carrier signal. Such means can include an amplifier 52 and a bandpass filter 54 which, as indicated, foπn a power line driver 70.
The second transmitter channel RIGHT includes means for supplying a second audio signal. Such means can include an audio input line 20, an AGC/amplifier circuit 22 and a pre-emphasis circuit 24 which conditions the second audio signal. The second transmitter channel RIGHT also includes means for supplying a second audio carrier signal having a second frequency ), for example 4.5 MHz, and means for modulating the second audio carrier signal with the second audio signal. A modulator 60 serves as a source of the second audio carrier signal and to modulate the second audio carrier signal by the second audio signal. The second transmitter channel RIGHT further includes means for filtering the modulated second audio carrier signal. Such means can include an amplifier 62 and a bandpass filter 64 which, as indicated, form a power line driver 80.
The transmitter also has a coupler 90 for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal to a power line for transmission along the power line.
Referring to Figure 2, the receiver portion of a power line audio system, constructed in accordance with the present invention, has first and second channels, only one of which is illustrated. The other receiver channel is identical to the one illustrated in Figure 2 except that the two channels are arranged to separately process the two audio carrier signals, as indicated by the fi ) notations in Figure 2, and detect the two audio signals.
The receiver has a coupler 110 for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal transmitted along the power line from the power line. Each of the receiver channels has means for passing one of the filtered, modulated first audio carrier signal transmitted along the power line or the filtered, modulated second audio carrier signal transmitted along the power line. Such means can include a bandpass filter 120, a limiter amplifier 125 and another bandpass filter 130. Each of the receiver channels also includes means for demodulating one of the filtered, modulated first audio carrier signal transmitted along the power line to detect the first audio signal or the filtered modulated second audio carrier signal transmitted along the power line to detect the second audio signal. Such means can include a demodulator 140 to detect the respective audio signals. Each of the receiver channels further includes means for supplying the detected audio signal to a speaker. Such means can include a de-emphasis circuit 142 and an amplifier 145 which conditions the detected signal. As shown in Figure 2, a volume and bass/treble control can be provided in the receiver portion of the system.
Although illustrated and described herein with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.

Claims

What is Claimed: 1. A power line audio system comprising: a power line; a transmitter having: (a) a first channel having: (1) means for supplying a first audio signal, (2) means for supplying a first audio carrier signal having a first frequency, (3) means for modulating said first audio carrier signal with said first audio signal, and (4) means for filtering the modulated first audio carrier signal, (b) a second channel having: (1) means for supplying a second audio signal, (2) means for supplying a second audio carrier signal having a second frequency, (3) means for modulating said second audio carrier signal with said second audio signal, and (4) means for filtering the modulated second audio carrier signal, and (c) a coupler for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal to said power line for transmission along said power line; and
a receiver having: (a) a coupler for coupling the filtered, modulated first audio carrier signal and the filtered, modulated second audio carrier signal transmitted along said power line from said power line, (b) a first channel having: (1) means for passing said filtered, modulated first audio carrier signal transmitted along said power line, (2) means for demodulating said filtered, modulated first audio carrier signal transmitted along said power line to detect said first audio signal, and (3) means for supplying said detected first audio signal to a first speaker, and (b) a second channel having: (1) means for passing said filtered, modulated second audio carrier signal transmitted along said power line, (2) means for demodulating said filtered, modulated second audio carrier signal transmitted along said power line to detect said second audio signal, and (3) means for supplying said detected second audio signal to a second speaker. 2. A power line audio system according to claim 1 wherein: (a) said means for supplying said first audio signal include means for conditioning said first audio signal, (b) said means for supplying said second audio signal include means for conditioning said second audio signal, (c) said means for supplying said detected first audio signal include means for conditioning said detected first audio signal, and (d) said means for supplying said detected second audio signal include means for conditioning said detected second audio signal. 3. A power line audio system according to claim 2 wherein: (a) said means for conditioning said first audio signal include an automatic gain control circuit, an amplifier, and a pre-emphasis circuit, (b) said means for filtering said modulated first audio carrier signal include an amplifier and a bandpass filter, (c) said means for conditioning said second audio signal include an automatic gain control circuit, an amplifier, and a pre-emphasis circuit, (d) said means for filtering said modulated second audio carrier signal include an amplifier and a bandpass filter, (e) said means for passing said filtered, modulated first audio carrier signal transmitted along said power line include a first bandpass filter, a limiter amplifier and a second bandpass filter, (f) said means for passing said filtered, modulated second audio carrier signal transmitted along said power line include a first bandpass filter, a limiter amplifier and a second bandpass filter, (g) said means for conditioning said detected first audio signal include a de-emphasis circuit and an amplifier, and (h) said means for conditioning said detected second audio signal include a de-emphasis circuit and an amplifier. 4. A power line audio transmission system according to claim 3 wherein: (a) said amplifier in said means for conditioning said detected first audio signal includes means for controlling the volume level of said detected first audio signal, and (b) said amplifier in said means for conditioning said detected second audio signal includes means for controlling the volume level of said detected second audio signal. 5. A power line audio transmission system according to claim 3 wherein said first audio carrier signal has a frequency of 3.58 MHz and said second audio carrier signal has a frequency of 4.5 MHz.
PCT/US1996/020173 1995-12-19 1996-12-18 Power line audio system WO1997023056A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU12948/97A AU1294897A (en) 1995-12-19 1996-12-18 Power line audio system

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US889595P 1995-12-19 1995-12-19
US60/008,895 1995-12-19
US76652996A 1996-12-13 1996-12-13
US08/766,529 1996-12-13

Publications (1)

Publication Number Publication Date
WO1997023056A1 true WO1997023056A1 (en) 1997-06-26

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PCT/US1996/020173 WO1997023056A1 (en) 1995-12-19 1996-12-18 Power line audio system

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WO (1) WO1997023056A1 (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001031806A1 (en) * 1999-10-22 2001-05-03 Openglobe, Inc. Data power line network
EP1253725A2 (en) * 2001-04-26 2002-10-30 Robert Bosch Gmbh Method for data transmission and device therefor
KR20040006044A (en) * 2002-07-09 2004-01-24 삼성전기주식회사 Audio system using PLC
WO2006029825A1 (en) * 2004-09-14 2006-03-23 K + H Vertriebs- Und Entwicklungsgesellschaft Mbh Device for receiving audio signals transmitted in a wireless manner
KR100736128B1 (en) 2004-12-01 2007-07-06 주식회사 파이컴 apparatus for transmitting and receiving analog audio signal by power line
CN107948855A (en) * 2017-11-24 2018-04-20 海尔优家智能科技（北京）有限公司 A kind of method and apparatus that audio signal is transmitted by power cord

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0119290A1 (en) * 1983-03-22 1984-09-26 ANT Nachrichtentechnik GmbH Three-stage single-side band premodulated frequency carrier system
US4829570A (en) * 1987-05-22 1989-05-09 Recoton Corporation Wireless remote speaker system
US4847903A (en) * 1987-05-22 1989-07-11 Recoton Corporation Wireless remote speaker system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0119290A1 (en) * 1983-03-22 1984-09-26 ANT Nachrichtentechnik GmbH Three-stage single-side band premodulated frequency carrier system
US4829570A (en) * 1987-05-22 1989-05-09 Recoton Corporation Wireless remote speaker system
US4847903A (en) * 1987-05-22 1989-07-11 Recoton Corporation Wireless remote speaker system

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001031806A1 (en) * 1999-10-22 2001-05-03 Openglobe, Inc. Data power line network
EP1253725A2 (en) * 2001-04-26 2002-10-30 Robert Bosch Gmbh Method for data transmission and device therefor
EP1253725A3 (en) * 2001-04-26 2003-02-12 Robert Bosch Gmbh Method for data transmission and device therefor
KR20040006044A (en) * 2002-07-09 2004-01-24 삼성전기주식회사 Audio system using PLC
WO2006029825A1 (en) * 2004-09-14 2006-03-23 K + H Vertriebs- Und Entwicklungsgesellschaft Mbh Device for receiving audio signals transmitted in a wireless manner
KR100736128B1 (en) 2004-12-01 2007-07-06 주식회사 파이컴 apparatus for transmitting and receiving analog audio signal by power line
CN107948855A (en) * 2017-11-24 2018-04-20 海尔优家智能科技（北京）有限公司 A kind of method and apparatus that audio signal is transmitted by power cord

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