| 摘要 |
PROBLEM TO BE SOLVED: To provide a band-pass sigma-delta modulator with a high speed and a high dynamic range. SOLUTION: A bandpass sigma-delta modulator using acoustic resonators or micro-mechanical resonators is disclosed. In order to improve the resolution at high frequencies, acoustic resonators or micro-mechanical resonators are utilized in a sigma-delta modulator. The quantized output is fed back, by using a pair of D/A converters to an input summation device. Such a sigma-delta modulator is usable in a software-defined radio cellular telephone system and in other applications, where high-frequency and high-resolution A/D conversion are required. An anti-resonance cancellation circuit may remove the anti-resonance component from the output of the resonators, by providing a signal which is subtracted from the output of the resonator. The cancellation circuit includes a capacitor which matches the static capacitance of the resonator. The loads of the resonator and of the cancellation network are also matched. COPYRIGHT: (C)2009,JPO&INPIT
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