26 GHz-Band Direct Digital Signal Generation by a Manchester Coding 1-Bit Band-Pass Delta-Sigma Modulator using It's 7th Nyquist Zone

In this paper, we propose a direct digital RF transmitter using a I-bit band-pass delta-sigma modulator for micro-wave/millimeter-wave applications. This transmitter directly generates a RF signal from the lower rate 1-bit stream by utilizing it's higher order Nyquist zone. We made signal power and SNR comparisons between three types of 1-blt DAC signals; non-return-to-zero (NRZ), 50% duty return-to-zero (RZ) and Manchester coding. By using 1Vp-p / 8 Gbps DAC output, Manchester coding shows the highest output signal power of -20.3 dBm and SNR of more than 40 dB in the 7th Nyquist zone (around 26 GHz). Based on this study, we have tried to adopt this technique to generate a 26 GHz-band 5 Mbps QPSK modulated signal and have confirmed that an EVM of 2.4% can be obtained in the 7th Nyquist zone.