Design of an E-band QPSK Modulator Employing a Novel Power Combining Strategy
Examensarbete för masterexamen
Wireless, photonics and space engineering (MPWPS), MSc
Quadrature phase shift keying is an important modulation format in telecommunications engineering. The most common ways in which a signal in this modulation format is generated is associated with large losses of up to and exceeding 50 % of the available signal power. At the high operating frequencies of modern state-of-the-art telecommunications circuitry, this output power comes at a significant cost. In this work, we show how the traditional way of combining power from an in-phase and quadrature signal source in a QAM system is associated with losses. We then start from first principles and derive the conditions under which a network operates as an ideal power combiner, respecting the constraints imposed by the modulation format. Furthermore, we show how a practical passive circuit that comprises this benefit can be designed. The theory is then put into practice in an illustrative design of an E-band QPSK modulator, where we also design a purpose-built power combiner according to the elaborated theory and show that this circuit can be easily designed into a modulator circuit. We finally perform simulations to verify the benefits of the designed power combiner. As predicted by theory, the combiner itself is almost lossless save from the small resistive losses that are expected in associated metal conductors, reasserting its benefit over traditional circuits, such as the Wilkinson power combiner.
Informations- och kommunikationsteknik , Hållbar utveckling , Elektroteknik och elektronik , Telekommunikation , Elektroteknik , Elektronik , Information & Communication Technology , Sustainable Development , Electrical Engineering, Electronic Engineering, Information Engineering , Telecommunications , Electrical engineering , Electronics