
Demystifying Switched-Capacitor Circuits
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preferred in the digital high-IF receivers [11][17]. For the ∆Σ modulators in this
chapter, three different IFs are chosen: 78 MHz for GSM, 138.24 MHz for WCDMA,
and 110.59 MHz for DECT.
As mentioned earlier, a third-order 1-bit single-stage modulator structure is
adequate to the design requirements in Table 8.3. An OSR of 192 is chosen for GSM
to achieve a high SNR more than 100 dB. For DECT, the value of its OSR is set to
64. The OSR is set to only 24 since a channel bandwidth of about 2 MHz is required
by the WCDMA standard.
Having determined the OSR values, we can calculate the different sampling ...