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    • 82. 发明申请
    • INPUT FILTER FOR IMAGE FREQUENCY SUPPRESSION
    • 用于图像频率抑制的输入滤波器
    • US20080287089A1
    • 2008-11-20
    • US12123538
    • 2008-05-20
    • Martin Alles
    • Martin Alles
    • H04B1/16
    • H03H7/0153H03H7/1725H03H7/1791H03H2007/013H03H2210/015H04B1/30
    • An input filter is provided for a superheterodyne receiver for image frequency suppression and a method for operating a superheterodyne receiver. The input filter for a superheterodyne receiver includes a first filter circuit with bandpass characteristics and a center frequency that can be preset as a function of a desired receive frequency, the circuit having a varactor diode and a first filter inductor that are connected in parallel and form a parallel-resonant circuit, wherein the center frequency can be preset by application of a control voltage to the varactor diode, and a second filter circuit with band stop characteristics that includes the varactor diode and a second filter inductor, these being connected in series and forming a series-resonant circuit, and that has a maximum attenuation in the vicinity of an image frequency belonging to the desired receive frequency. The input filter may be used in, for example, DAB receivers.
    • 为用于图像频率抑制的超外差接收机提供输入滤波器,以及用于操作超外差接收机的方法。 用于超外差接收器的输入滤波器包括具有带通特性的第一滤波器电路和可以作为期望接收频率的函数预设的中心频率,该电路具有并联连接并形成的变容二极管和第一滤波电感器 并联谐振电路,其中可以通过向变容二极管施加控制电压来预设中心频率,以及具有带阻特性的第二滤波器电路,其包括变容二极管和第二滤波电感器,这些电感器串联连接, 形成串联谐振电路,并且在属于所需接收频率的图像频率附近具有最大衰减。 输入滤波器可以用在例如DAB接收机中。