Su, Zi Jun2025-02-202025-02-202025-02-202025-02-07https://hdl.handle.net/10012/21478The rise of sixth-generation (6G) wireless technology has created a need for wideband signal generation at high radio frequencies (RF). However, current digital-to-analog converters (DACs) face limitations, offering either wide bandwidth with low resolution or high resolution with limited bandwidth. This thesis proposes two methods that utilize multiple DACs to generate multiple narrowband sub-bands of a wideband signal, that are combined to produce the desired wideband signal. These methods employ distinct digital processing approaches tailored to specific applications, such as instrumentation or real-time Orthogonal Frequency Division Multiplexing (OFDM) signal generation. To address non-idealities in frequency-stitching-based transmitters, a frequency-domain calibration technique using multi-tone signals is introduced. Experiments at X-band (9.6 GHz) and D-band (129.6 GHz) validate these methods, demonstrating up to 8 GHz bandwidth and achieving an error vector magnitude (EVM) as low as 0.3\% for a 7.2 GHz 256-QAM OFDM signal. A comparative study of three signal generation approaches—direct Arbitrary Waveform Generator (AWG) generation, baseband in-phase and quadrature (IQ) generation with up-conversion, and frequency stitching—shows EVMs of 1.5\%, 0.8\%, and 1\%, respectively, for an 8 GHz OFDM signal. A novel architecture using phase-coherent IQ-DACs and mixers for each sub-band is also presented. Calibration using non-uniformly interleaved tones corrects IQ imbalances and distortions, enabling the generation of a 256-QAM OFDM signal with 12 GHz bandwidth at D-band (149 GHz) and achieving a peak data rate of 96 Gbps. Calibration improves EVM and normalized mean square error (NMSE) from 82.6\% and 23.8\% to below 2\% and 1\%, respectively. Additionally, D-band amplifier linearization with a 4 GHz modulation bandwidth improves adjacent channel power ratio (ACPR) from -27.8/-26 dBc to -42.8/-43.1 dBc and EVM from 8.5\% to 1.2\%. Finally, two architectures for sub-band combination are compared. One generates a wideband signal at intermediate frequency (IF) and up-converts it, while the other up-converts narrowband IF signals and combines them. The second approach demonstrates superior ACPR at high IF power levels, enhancing ACPR by up to 8 dB when generating a 1.2 GHz modulated signal at 142.5 GHz. These results highlight the efficacy of the proposed methods for generating and linearizing high-quality wideband signals, supporting advanced applications in millimeter wave and sub-THz frequency bands for 6G technologies.enwideband 6G signals generationfrequency-stitchingcalibration techniqueD-bandcomponent testing systemsMaster Thesis