Micro- and millimetre-wave circuits for broadband six-port junction receivers
Qayyum, Saad; Negra, Renato (Thesis advisor); Bensmida, Souheil (Thesis advisor)
Aachen (2019) [Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (xi, 176, xvii Seiten) : Illustrationen, Diagramme
Software-defined-radios (SDRs) employ a broadband RF frontend and allow flexibility in terms of changing the operating characteristics of a communication receiver using software routines without any hardware modification. An SDR frontend covering the allocated 27-GHz bandwidth in the unlicensed millimetre-wave V- and E- bands has the potential to deliver multi-Gbps data rates. Issues like high cost, design complexity, narrow bandwidth, and high power consumption of the traditional receivers necessitate the research of alternative receiver architectures. The design simplicity and wideband characteristics of a six-port junction receiver makes it an ideal candidate for SDR implementation, especially for integrated millimetre-wave systems. A six-port junction receiver frontend consists of a passive six-port junction and four power detectors. Integrated systems implemented in a standard CMOS technology offer the benefit of realising a complete system-on-chip, which offers a low-cost solution for a mass volume production. However, the passive microwave devices implemented in a standard CMOS technology possess poor quality factor due to the lossy, low resistivity substrate. Hence, it is a challenge to realise a broadband, CMOS-based passive six-port junction. Furthermore, it is difficult to design power detectors with broadband input matching without sacrificing its sensitivity. CMOS power detectors possess low voltage sensitivity due to the inferior second-order transfer coefficient, gd2, of the MOSFET's nonlinear transfer characteristic operating in the resistive and strong-inversion regimes. This opens up the space to explore broadband power detector topologies suitable for fabrication using a standard CMOS process. The goal of this thesis is to develop novel topologies for the broadband, passive six-port junctions as well as the broadband and high sensitivity power detectors suitable for fabrication using PCB-based microwave hybrid and bulk CMOS technologies. A multilayer passive six-port junction, covering microwave frequencies, is proposed for a hybrid implementation to achieve broadband operation. Furthermore, a compact and broadband six-port junction has been demonstrated using a standard CMOS process. The proposed six-port junction takes benefit of a broadside CPW coupling structure to achieve low insertion loss and broadband operation in terms of the junction’s q-points. Several broadband power detectors are also proposed for hybrid and CMOS implementations. A broadband, high sensitivity power detector employing a tunable input matching network is proposed for a Schottky diode-based hybrid implementation. Moreover, a detailed analysis of the diode-based distributed power detectors is presented to aid an optimal design. For CMOS power detectors, it is proposed to operate the MOSFET device in the subthreshold regime to boost its voltage sensitivity. The increased voltage sensitivity, in turn, can be traded off to achieve wide video bandwidth. It is demonstrated that the power detectors implemented in deep submicron CMOS technologies can deliver wide matching bandwidth with a resistive input matching network. However, the matching bandwidth may not be sufficient for the CMOS processes with relatively long channels lengths due to an increase in the input capacitance. Moreover, two CMOS power detectors based on a distributed topology are proposed, which provide wider matching bandwidth than possible with a resistive input matching network. Apart from providing broadband input matching, the distributed topology has the ability to deliver wide video bandwidth as well as improving the threshold sensitivity. This thesis demonstrates the ability of the constituent circuits of the six-port junction receivers’ frontend to cover wide bandwidth at microwave and millimetre-wave frequencies. The findings of this thesis endorse the possibility of realising a high-capacity, millimeter-wave SDR frontend for future wireless systems.