Low-distortion bandpass /spl Sigma/-/spl Delta/ modulator for wireless radio receivers |
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Authors: | Rusu A Ismail M |
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Affiliation: | Microelectron. & Inf. Technol. Dept., IMIT, Kista, Sweden; |
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Abstract: | A low-distortion bandpass sigma-delta modulator is proposed. It was found that the key to improving linearity is to add a feedforward signal path in a double-delay resonator bandpass structure. The proposed technique improves the tonal behaviour even at low oversampling ratio and can be applied for any order of modulator. Based on the proposed architecture, a fourth-order single-bit sigma-delta modulator can achieve a dynamic range of 84 dB and a spurious free dynamic range of 98 dB at 10.71 MHz with a signal bandwidth of 200 kHz, making it ideal for a narrowband IF-sampled wireless receiver designed for compliance with GSM/GPRS standards. |
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