A Multi-Band Low-Supply-Voltage 16-QAM Transmitter Based on a Digital Fractional-N PLL With TDC Calibration for...

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Wireless Communication

Background:

• Capsule endoscopy requires high data rates and energy efficiency for wireless data transmission.
• Limited battery capacity in capsules necessitates power-efficient transmitter designs.
• Meeting receiver sensitivity specifications demands adequate output power and low noise.

Purpose of the Study:

• To present a highly digital transmitter for multi-band 16-QAM modulation for capsule endoscopy.
• To achieve high data rates with high energy efficiency and output power.
• To reduce power consumption in battery-powered endoscopy capsules.

Main Methods:

• Utilized a counter-assisted digital phase-locked loop (CDPLL) for low-noise clock generation across multiple bands.
• Implemented a time-to-digital converter (TDC) calibration for improved EVM performance.
• Developed a digital power amplifier with high power efficiency.

Main Results:

• The transmitter, fabricated in a 180-nm CMOS process, supports 40 Mbps with 16-QAM modulation.
• Achieved energy efficiency of 0.27/0.26 nJ/bit at 40 MHz data rate and 1.1-V supply.
• Measured EVM of 3.24/3.7% with -5-dBm output power in narrow bandwidths (10 MHz) at 435/415 MHz.
• Reported a figure of merit of 0.86/0.82 nJ/bit/mW in respective bands.

Conclusions:

• The developed digital transmitter meets the stringent requirements for capsule endoscopy, including high data rate, energy efficiency, and output power.
• The CDPLL with TDC calibration significantly improves EVM performance.
• The high-efficiency digital power amplifier contributes to reduced overall system power consumption, extending capsule operation time.