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    • 10. 发明申请
    • CONTROLLING THE BANDWIDTH OF AN ANALOG FILTER
    • 控制模拟滤波器的带宽
    • WO2008048744A3
    • 2008-07-03
    • PCT/US2007077169
    • 2007-08-30
    • FREESCALE SEMICONDUCTOR INCRAHMAN MAHIBURPARKES JOHN JRICHES JAMES J
    • RAHMAN MAHIBURPARKES JOHN JRICHES JAMES J
    • H04B1/66
    • H04B1/30H03H11/1256H03H11/1291H03H2210/012H03H2210/015H03H2210/025H03H2210/036
    • A digital tuning system (250) for changing a cutoff frequency of an analog filter (132) includes digital synthesizers (292 and 294) for producing a two-tone calibration signal (196) applied to an input of the filter after a quality factor of the filter is increased The filter includes at least one R/C circuit with two resistors (304 and 306) for changing the quality factor and arrays (308 and 310) of capacitors for changing the cutoff frequency The amplitude of the magnitude responses (409 and 411 ) of the filter to each tone (405 and 407) is measured by a two discrete Fourier transform single-frequency bin power detection circuits 10 (253 and 254) while the filter is sequenced through a plurality of capacitance settings An optimal capacitance for the R/C circuit is selected by comparing, to a pre¬ selected value, a difference between the responses of the filter to each tone, for each capacitance setting.
    • 用于改变模拟滤波器(132)的截止频率的数字调谐系统(250)包括数字合成器(292和294),用于产生应用于滤波器的输入的双色调校信号(196) 滤波器增加滤波器包括至少一个具有两个电阻器(304和306)的R / C电路,用于改变用于改变截止频率的电容器的品质因子和阵列(308和310)。幅度响应的幅度(409和 411和滤波器对于每个音调(405和407)的测量是通过两个离散的傅里叶变换单频箱功率检测电路10(253和254)来测量的,而滤波器通过多个电容设置进行排序。 对于每个电容设置,通过将滤波器的响应与每个音调的差值与预选值进行比较来选择R / C电路。