A CMOS 1.5-Bit ΣΔ DIGITAL IF TO RF TRANSMITTER FOR WCDMA APPLICATION

Yongping Han, Shahin Mehdizad Taleie, Tino Copani, Bertan Bakkaloglu, Sayfe Kiaei

Abstract

A digital intermediate frequency (IF) to RF transmitter targeted for 2 GHz wideband code division multiple access (WCDMA) is presented. The proposed transmitter integrates a 3-level digital IF current-steering cell, an up-conversion mixer with a tuned load and an RF variable gain amplifier (RF VGA) with an embedded semidigital finite impulse response (FIR) reconstruction filter. A 4^th-order 1.5-b IF bandpass sigma delta modulator (BP ΣΔM) is designed to guarantee in-band signal-to-noise ratio (SNR) and error vector magnitude (EVM) performances while the out-of-band quantization noise due to noise shaping is suppressed by the embedded FIR reconstruction filter to meet spectrum emission mask and ACPR requirements. The on-chip RF VGA provides 50 dB power scaling in 10-dB steps with less than 1 dB gain error. Together with the power control at the ΣΔM stage, the 74-dB dynamic range at RF frequency is achieved. The design is fabricated in a 4-metal 0.18-µm CMOS technology with a total core area of 0.8 × 1.6 mm². The IC delivers 0 dBm output power to the 50 Ω load at 2 GHz and it draws approximately 120 mA from a 1.8 V DC supply at the maximum output power.

Keywords

digital transmitter, sigma-delta modulator, digital to analog converters (DACs), digital IF, RF variable gain amplifier (RF VGA), wideband code division multiple access (WCDMA)

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DOI

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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