Researches of Microwave Oscillator Phase-Noise Measurement and Quadrature-Tracking Demodulator

• Main Authors: LEE, CHAN-HUNG, 李展宏
• Other Authors: PENG, KANG-CHUN
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/aj597w

博士 === 國立高雄第一科技大學 === 工學院工程科技博士班 === 106 === Measurement is the basis for the development of microwave circuit system and mastering the skill of accurate and good measurement is the key requirement for the development of an excellent microwave system. However, the high cost of microwave measuring instrument often leaves researchers hesitant to continue research and development in the discipline of microwave technology or in their specialty. In order to resolve the problem, this paper proposed and developed two precise and low-cost phase noise measurement technologies, which were injection-locking frequency discriminator and injection-locking six-port frequency discriminator, respectively, to greatly reduce the developmental cost of microwave oscillator phase noise measurement instrument, while it could be applied to the performance verification of Microwave oscillator prototype circuit in general labs. It could also help researchers to accurately understand the characteristics of circuit design. In order to overcome the increase in bit error rate of receiver due to the quadrature phase imbalance of the conventional co-demodulator for the orthogonal frequency division multiplexing (OFDM) system, an advanced quadrature-tracking demodulator was also proposed. The architecture of proposed quadrature-tracking demodulator was mainly composed of two novel QPLLs that could respectively track the IQ phases of the received OFDM signals and simultaneously demodulate them. In order to maintain the quadrature characteristic of the QPLLs, the two PLLs shared the same quadrature voltage-controlled oscillator (QVCO), synchronous tracking of the received OFDM IQ signal. The design of QVCO chip used two sets of cross-coupled pair QVCO with the same differential, while synchronously control and phase tracking the voltage adjustment ports of these two oscillators to ensure the quadrature characteristics of the QVCO output signal. In addition, since OFDM radio frequency receivers of wireless communication system generally adopted direct frequency down-demodulation architecture to reduce the possible impact of DC-offset, the DC subcarriers in the related OFDM communication protocols were not standardized for use. Therefore, with phase-locked loop bandwidth lower than the subcarrier spacing of the OFDM signal, the QPLL coherent demodulation technology proposed in this paper was especially suitable for the receiver architecture of an OFDM system.