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    A SYSTEM AND METHOD FOR RECOVERING SYMBOL TIMING OFFSET AND CARRIER FREQUENCY ERROR
    2.
    发明公开
    A SYSTEM AND METHOD FOR RECOVERING SYMBOL TIMING OFFSET AND CARRIER FREQUENCY ERROR 审中-公开
    DEVICE AND METHOD FOR RECOVER符号时移和载波频率误差

    公开(公告)号：EP1155545A2

    公开(公告)日：2001-11-21

    申请号：EP00908707.3

    申请日：2000-02-17

    申请人： USA Digital Radio, Inc.

    发明人： PEYLA, Paul, James ,  BRONDER, Joseph, Bertram

    IPC分类号： H04L27/26

    CPC分类号： H04L27/2662 ,  H04L27/2657 ,  H04L27/2676

    摘要： The system for recovering symbol timing offset and carrier frequency error from an orthogonal frequency division multiplexed (OFDM) signal includes a receiver circuit for receiving an OFDM modulated signal representing a series of OFDM symbols, and providing a received signal to an output thereof. A peak development circuit is included for developing a signal having a plurality of signal peaks representing symbol boundary positions for each received OFDM symbol, where each of the signal peaks is developed responsive to an amplitude and phase correspondence produced between the leading and trailing portions of each of the received OFDM symbols. The system includes a circuit for enhancing the signal peak detectability, which includes a circuit for additively superimposing and then filtering the signal peaks, to produce an enhanced signal peak having an improved signal-to-noise ratio. A circuit for establishing a temporal position indicative of the symbol boundary position from at least one of the enhance signal peaks output from the signal enhancing module is also provided. Further, a circuit for recovering the received OFDM signal carrier frequency error corresponding to the temporal position is included.

    AM COMPATIBLE DIGITAL WAVEFORM DEMODULATION USING A DUAL FFT
    3.
    发明公开
    AM COMPATIBLE DIGITAL WAVEFORM DEMODULATION USING A DUAL FFT 失效
    AM-兼容解调的数字波形采用双FFT

    公开(公告)号：EP0847642A4

    公开(公告)日：2001-09-12

    申请号：EP96928969

    申请日：1996-08-21

    申请人： USA DIGITAL RADIO INC

    发明人： CARLIN BARRY W ,  DAPPER MARK J ,  GEILE MICHAEL J

    IPC分类号： H04L27/00 ,  H03D1/22 ,  H04J11/00 ,  H04L27/26 ,  H04L27/06 ,  H03D1/00

    CPC分类号： H03D1/2245 ,  H04H2201/186 ,  H04L27/265

    摘要： The invention provides a method and apparatus for demodulating a composite AM DAB waveform which contains digitally modulated carriers and which employ a mixer (180) for converting a received signal (170) into two signals, the first of these signals represents an in-phase component and the second of the signals represents a quadrature component, two analog-to-digital converters (182, 184) for converting the two signals into digital signals, and two fast Fourier transform elements (188, 190) for extracting data separately from the two digital signals. Complementary digital carrier signals are recovered from the quadrature, and non-complementary digital carriers are derived from a sum of the complementary data and the output of the in-phase component FFT process. Leakage of the AM signal through a highpass filter (186) is prevented from interfering with the demodulation of the complementary carrier signal's use of separated demodulation channels.

    AUDIO BLEND METHOD, TRANSMITTER AND RECEIVER FOR AM AND FM IN BAND ON CHANNEL DIGITAL AUDIO BROADCASTING
    4.
    发明公开
    AUDIO BLEND METHOD, TRANSMITTER AND RECEIVER FOR AM AND FM IN BAND ON CHANNEL DIGITAL AUDIO BROADCASTING 有权
    TONMISCHUNGSVERFAHREN，AM和FM IN-BAND发送者和接收者打开通道数字音频广播

    公开(公告)号：EP1155521A1

    公开(公告)日：2001-11-21

    申请号：EP00908706.5

    申请日：2000-02-17

    申请人： USA Digital Radio, Inc.

    发明人： KROEGER, Brian, William

    IPC分类号： H04H1/00

    CPC分类号： H04H20/30 ,  H04H60/11 ,  H04H2201/20

    摘要： A method is provided for processing a composite digital audio broadcast signal to mitigate intermittent interruptions in the reception of said digital audio broadcast signal. The method includes the steps of separating an analog modulated portion of the digital audio broadcast signal from a digitally modulated portion of the digital audio broadcast signal, producing a first plurality of audio frames having symbols representative of the analog modulated portion of the digital audio broadcast signal, and producing a second plurality of audio frames having symbols representative of the digitally modulated portion of the digital audio broadcast signal. The first plurality of audio frames is then combined with the second plurality of audio frames to produce a blended audio output. A method is also provided for transmitting a composite digital audio broadcast signal having an analog portion and a digital portion to mitigate intermittent interruptions in the reception of said digital audio broadcast signal. The method comprises the steps of arranging symbols representative of the digital portion of the digital audio broadcast signal into a plurality of audio frames, producing a plurality of modem frames, each of the modem frames including a predetermined number of the audio frames, and adding a frame synchronization signal to each of the modem frames. The modem frames are then transmitted along with the analog portion of the digital audio broadcast signal, with the analog portion being delayed by a time delay corresponding to an integral number of the modem frames. The invention also encompasses radio receivers and transmitters which process signals according to the above method.

    A SYSTEM AND METHOD FOR MITIGATING INTERMITTENT INTERRUPTIONS IN AN AUDIO RADIO BROADCAST SYSTEM
    5.
    发明公开
    A SYSTEM AND METHOD FOR MITIGATING INTERMITTENT INTERRUPTIONS IN AN AUDIO RADIO BROADCAST SYSTEM 审中-公开
    DEVICE AND METHOD FOR一天我避免中断在音频广播系统

    公开(公告)号：EP1025663A1

    公开(公告)日：2000-08-09

    申请号：EP98953529.9

    申请日：1998-10-06

    申请人： USA Digital Radio, Inc.

    发明人： KROEGER, Brian, William ,  STEHLIK, Roy, Ronald

    IPC分类号： H04H1/00 ,  H04L1/02 ,  H04L27/26 ,  H04B7/12

    CPC分类号： H04H20/22 ,  H04B7/12 ,  H04H20/30 ,  H04H60/11 ,  H04H2201/183 ,  H04H2201/20 ,  H04L1/02 ,  H04L5/0005

    摘要： A system (100) for mitigating intermittent interruptions in an audio radio broadcast system is provided wherein a primary radio signal and a redundant radio signal are transmitted from a transmitter subsystem (120) and received by a receiver subsystem (140). The output (112) of an audio source (110) is coupled to a modulator (160) for modulating a radio frequency signal (162) for coupling to a transmit antenna (172). A second output (114) of audio source (110) is coupled to a delay circuit (116), for adding a predetermined time delay thereto. The delayed audio source signal is coupled to a modulator (164) for modulating a second radio frequency signal (166) that is also coupled to the transmit antenna (172). The receiver subsystem (140) receives both the primary radio signal and the delayed redundant radio signal and couples each to a respective demodulator (180, 182). At least demodulator (180) includes a circuit (181) for determining the degradation in the primary radio signal and provides a quality measurement output signal (186) to a blend control circuit (190). The recovered primary audio signal from demodulator (180) is coupled to a second delay circuit (184), the time delay of second delay circuit (184) being substantially equal to the time delay of delay circuit (116). The audio output from delay circuit (184) and the redundant audio output from demodulator (182) are coupled to a blending subsystem (135), wherein each is combined with a weighting factor and then combined together to form a composite audio signal for coupling to the audio output circuit (150).