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

• 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)
• Download:

  IMEKO-IWADC-2011-65.pdf
• DOI:

  _unreg_iwadc-2011.65

Event details:

• IMEKO TC:

  TC4
• Event name:

  IWADC 2011
• Title:

  16th IMEKO International Workshop on ADC Modeling and Testing - Data Converter Design, Modeling and Testing (together with IEEE ADC Forum) (IWADC)

• Place:

  Orvieto, ITALY
• Time:

  30 June 2011 - 1 July 2011