Efficiency Improvement of Delta Sigma Modulator-Based Transmitter Using Complex Delta Sigma Modulator and Noise Reduction Loop

This paper proposes an architecture to enhance coding efficiency (CE) of the Delta Sigma Modulator (DSM) transmitters. In this architecture, a complex-low pass delta sigma modulator (LPDSM) is used instead of existing Cartesian-LPDSM and polar-low pass envelope delta sigma modulator (LPEDSM). Simulation results show that for Uplink long-term evolution (LTE) signal with 1.92 MHz bandwidth and 7.8-dB peak to average power ratio (PAPR), the CE for the complex-LPDSM-based transmitter is equal to 41.7% in compare to 9.7% CE for Cartesian-LPDSM transmitter. Also, due to the resolving of noise convolution problem, the complex-LPDSM-based transmitter baseband part needs lower oversampling ratio (OSR) and clock speed than polar-LPEDSM transmitter baseband part to achieve the same signal-to-noise and distortion ratio (SNDR). In the next step, a quantization noise reduction loop is implemented in this architecture. By using this technique for an Uplink LTE signal with 1.92 MHz bandwidth, with the same PAPR and OSR of 16, the CE is improved from 41.7% to 56.1% with 40 dB SNDR.