A Low Out-Of-Band Noise 2.5GHZ DTX

Abstract

The increasing demand for high-data-rate wireless communication requires transmitters with high efficiency, linearity, and low out-of-band noise. Digital transmitters offer advantages in terms of integration and power efficiency but suffer from unfiltered quantization noise and sampling spectral replicas. This thesis presents the design and implementation of a fully integrated digital transmitter (DTX) based on a Switched-Capacitor Power Amplifier (SCPA) combined with a Finite Impulse Response (FIR) filter to suppress out-of-band quantization noise and improve spectral purity.

The SCPA architecture was optimized through transistor and series capacitor sizing, together with a power-combining technique to enhance the output power and efficiency. A novel mixed-domain FIR filter was integrated into the DTX to suppress quantization noise and out-of-band spectral replicas. Through simulations and analysis, the proposed DTX architecture demonstrates a peak RF output power exceeding 30 dBm while suppressing noise in both frequency-division duplexing (FDD) and time-division duplexing (TDD) scenarios. The results demonstrate the potential of the proposed architecture for efficient, high-linearity wireless transmitters with improved out-of-band noise performance.