http://repository.iiitd.edu.in/xmlui/handle/123456789/953 2026-04-10T22:13:34Z http://repository.iiitd.edu.in/xmlui/handle/123456789/1055 Design of multi-band, broadband passive circuits and their application in RF power amplifiers Saxena, Antra; Hashmi, Mohammad S. (Advisor) The last two years have shown a different life scenario when the pandemic hit every part of the world. It reshaped the life of humans rapidly by forcing work from home, online education, online shopping and more. The pandemic has put brakes on this constantly fast-moving world. However, technology bridged the gap of physical distancing by providing everything online, from medical assistance to non-essential items, from family video-calling to online schooling and many more. The internet has played a preeminent role in the last two years, and technology in the hand of every human, from kids to adults, assists in overcoming stressful situations. The technologies that will formulate the next-generation wireless systems are being defined today. The primary motivation of this research was the increased complexity of mobile devices, resulting in more significant challenges and stringent requirements in the design of all front-end components, including filters, power dividers, matching networks and power amplifiers (PAs). Inevitably, RF front-end solutions for different applications, including telecommunication, aerospace, military and others, have moved from the discrete solution with one or more single-band circuits, including PA modules, matching networks etc., towards the ultimate multi-band solutions. In this approach, one module will support all existing standards while covering different frequency bands of operation. This doctoral dissertation focused on the challenges and considerations in designing different components in any RF front-end module. The main contribution of this thesis is to develop dual-band/broadband architectures for passive devices, including matching networks and power dividers, as well as their applications in active devices such as harmonically tuned power amplifiers. Various design methods have been discussed and analyzed to provide different architectures with practical solutions. Design and analysis of distinct matching networks are proposed. The theoretical basis for designing the dual-band matching networks, closed-form equations, analysis, additional case studies and fabrication of prototypes for validation purposes is contributed. Different scenarios discussed include real-to-real matching, real-to-complex matching and complex-to-complex matching, depending on the nature of the source and load type. Also, broadband power dividers have been studied rigorously to operate over a wide range of frequencies with DC blocking capability, which is a primary demand in any RF front end. Two different broadband power dividers operating over a wide range of frequencies, including their design and analysis, are proposed. Other methods are presented with inherent DC-blocking capabilities that are useful in many practical applications. Along with passive circuits, the multi-band matching network is utilized to design power amplifiers that can provide desirable performance in terms of efficiency and gain. Two methodologies are proposed, which are simple and supported by closed-form equations that maintain easy fabrication and are pragmatic in implementation. It considers the application of multi-band matching networks in designing high-efficiency RF power amplifiers. Thus the key findings of this thesis include different multi-band/broadband passive devices, including matching networks and power dividers which are accompanied by closed-form equations to obtain mathematical formulations for easy designing and prototyping. The application of matching networks in active devices, i.e. power amplifiers, is explored. The harmonically tuned power amplifier, accompanied by formulations and design procedures to obtain optimum performance, is verified with design examples and case studies. 2022-12-01T00:00:00Z http://repository.iiitd.edu.in/xmlui/handle/123456789/1042 An energy-efficient hybrid DAC based SAR ADC using deep-submicron CMOS and large-area oxide TFT technologies Tiwari, Bhawna; Bahubalindruni, Pydi Ganga Mamba (Advisor); Barquinha, Pedro (Advisor); Goes, João (Advisor); Deb, Sujay (Advisor) The successive approximation-register (SAR) analog-to-digital converters (ADCs) have excellent energy efficiency compared to other Nyquist-rate ADCs like Flash,Pipeline, etc. The simplest form of a SAR ADC employs track-and-hold (T/H) switches, a voltage comparator, a digital controller, and a capacitive digital-toanalog converter (DAC). Due to its simple architecture and highly digital and switching intensive behavior, its popularity has been boosted with technology down scaling. However, most of the designs reported in the literature employ binary-weighted capacitive DAC array, whose size increases exponentially with an increase in resolution of the ADC. This exponential increase degrades the conversion speed and energy efficiency of the SAR ADC. One of the best methods to reduce the size of the binary-weighted capacitive DAC array with the increasing resolution is to use two (or more) small-sized sub-DACs to form the complete DAC of the ADC. Though capacitive-resistive hybrid DAC-based SAR ADCs have been reported in the literature, resistive DAC tradeoff between power consumption, active area, and operating speed, which compromise the performance and energy efficiency. On the other hand, limited number of SAR ADCs with capacitive sub-DACs have been reported, which demand calibration logic and additional digital controller circuitry. Charge-Sharing (CS) and Merged-Capacitor Switching (MCS) are the two extensively employed switching schemes in the SAR ADCs. While the CS switching principle works on a single array of binary-weighted capacitive DAC, MCS works on two arrays of binary-weighted capacitive DAC for the differential implementation SAR ADC. It should be noted that though CS DAC employs a single array of capacitive DAC, it requires explicit T/H capacitors to perform the conversion algorithm. In addition, this scheme requires a pre-charging phase, in which the capacitors of the DAC array are charged to the reference voltage. As a result, for moderate to high resolution ADCs, the DAC size will be significant, and it will require a large current from the reference buffer to charge the DAC capacitors in a short duration of time. This research work presents a new hybrid capacitive DAC design for SAR ADC, which employs two switching principles, namely CS and MCS, to improve the performance metrics of the SAR ADC. The proposed hybrid DAC is purely based on capacitors, and it is designed to work without any calibration logic and additional digital controllers. Moreover, the proposed hybrid DAC architecture presents a solution where the capacitors of the MCS DAC act as T/Hcapacitors for the CS scheme when the conversion is done using this scheme, thus, eliminating the explicit T/H capacitors. On the other hand, due to the deployment of two sub-DACs in the proposed hybrid DAC design, the size of the CS sub-DAC can be reduced significantly, which helps in pre-charging the DAC capacitors in a small duration of time without drawing large current from the reference buffers. As a result, the hybrid DAC design can significantly improve the operating speed and energy efficiency of the complete ADC architecture. The proposed hybrid DAC based SAR ADC has been implemented in both deep-submicron CMOS and large-area oxide Thin-film transistor (TFT) technologies to show the design suitability for deep sub-micron and large-area semiconductor technologies. Since oxide TFT technology lacks stable and reproducible amorphous p-type transistors with reasonable performance, the complete ADC in this technology is designed using all enhancement n-type transistors with novel switches, comparator and shift register. The obtained results show FoM of the proposed SAR ADC to be 5fJ/c.s and 56nJ/c.s. in CMOS and oxide TFT technologies respectively, which are the best compared to the similar state of the art work reported in a particular technology to the best of authors knowledge. Since, the proposed CS-MCS hybrid DAC based SAR ADC design offers high energy efficiency, it finds wide applications in the field of wireless communication, biomedical, smart packaging and sensing systems. 2022-12-01T00:00:00Z http://repository.iiitd.edu.in/xmlui/handle/123456789/1041 Learning algorithms for non intrusive load monitoring Singh, Shikha; Majumdar, Angshul (Advisor) Non-Intrusive Load Monitoring (NILM), also known as Energy Disaggregation, is the process of segregating a building’s total electricity consumption into its appliances by appliance consumption from the smart meter data. In developed countries, Smart meters are currently being rolled out on a large scale, mainly due to the two most important benefits of energy disaggregation: 1)helps consumers understand their energy usage by providing itemized bills; 2)helps grids with capacity planning. These benefits ultimately lead to energy saving andcost-cutting. Existing algorithms for NILM consist of a training phase in which sub-metered appliance data is used to build models of the appliances. In the test phase, these models are used to disaggregate the total electrical energy consumption. To collect the appliance-level data, we need to put sensors on appliances present in the building. This makes the training phase intrusive. Due to this, such methods do not provide a scalable solution for NILM. This thesis has three main objectives: 1)To propose more accurate algorithms for NILM than state of the art; 2)To propose the methods which make the training phase completely non-intrusive, i.e., to dodge the requirement of the submetered data ; 3)To propose an algorithm that can work with compressed energy signals in order to save the bandwidth and avoid network congestion. First, we propose a dictionary-learning based algorithm called Deep Sparse Coding for NILM. The usual technique is to learn a dictionary for every device and use the learned dictionaries as a basis for blind source separation during disaggregation. Prior studies in this area are shallow learning techniques, i.e., they learn a single layer of dictionary for every device. In this work, we learn multiple layers of dictionaries for each device. These multi-level dictionaries are used as a basis for source separation during disaggregation. We show that this algorithm outperforms the benchmark techniques like Factorial Hidden Markov Model and Discriminative Disaggregating Sparse Coding. Second, we follow the multi-label classification based paradigm for NILM and determine the state(On/Off) of the appliances present in the building. For this, we propose several algorithms that adapted Transform Learning, Sparse Representation Classifier, Restricted Boltzmann Machine and Long Short Term Memory to perform multi-label classification and subsequently disaggregating the appliance-level load. Third, we propose a compressed sampling(CS) approach. The high-frequency power signal from a smart meter is encoded (by a random matrix) to very few samples making the signal suitable for WAN transmission without choking network bandwidth. CS guarantees the recovery of the high-frequency signal from the few transmitted samples under certain conditions. This work shows how to recover the signal and simultaneously disaggregate it. The motive of the work presented in this thesis is to propose NILM algorithms independent of the sub-metered data and make advancements in state-of-the-art in the field of energy disaggregation. 2022-07-01T00:00:00Z http://repository.iiitd.edu.in/xmlui/handle/123456789/1040 High throughputs and information freshness over the internet via transport layer advancements Shreedhar, Tanya; Kaul, Sanjit Krishnan (Advisor) Next-generation applications such as augmented reality, virtual reality, teleoperated driving, and video streaming, along with a wide spectrum of real-time monitoring and actuation applications, are expected to challenge the current Internet on at least two fronts. Many of these applications desire high throughput and reliability at low end-to-end path latencies. To better support them, we must optimize the joint use of the diversity of high link rate wireless access technologies commonly available at end-user devices. In addition, there is a burgeoning class of applications that requires the availability of fresh information (for example, sensor measurements and actuation commands in IoT applications) at the destination. The current Internet treats such applications no differently than it does those that care for throughput. In this thesis, we address the challenges posed by these distinct requirements of high throughput and high freshness via innovations at the transport layer of the networking stack. We address the challenge posed by applications that require high end-to-end throughputs via a novel cross-layer scheduler, QAware, for Multipath TCP (MPTCP). The QAware scheduler uses local queue occupancy information for every access network available on a user device in addition to the typically used end-to-end round-trip delay estimates. This results in a more efficient use of the available interfaces and considerable gains in aggregate throughput compared to other MPTCP schedulers for a varied set of applications and over heterogeneous access networks. For real-time monitoring and remote sensing applications, we address the challenge of enabling freshness, as quantified by the metric of age-of-information (AoI) over an end-to-end Internet path. Specifically, we propose and detail the Age Control Protocol (ACP) and its improved version called ACP+. Both use ACKs to maintain an estimate of the number of unacknowledged packets in the system along with the end-to-end RTT. This, together with an estimate of the time average age of updates is used to determine an ACP source’s update rate. We study the efficacy of ACP and ACP+ using extensive simulations and real-world experiments over the Internet. To gain further insight into age control, we also empirically compare ACP+ with a mix of loss-based, delay-based, and hybrid congestion control algorithms used by TCP. TCP tries to fill the network pipe using estimates of bottleneck rate and baseline RTT, but these estimates may not shed as much light on the age-optimizing update rate. In our experiments over paths in the Internet, ACP+ utilizes only a fraction of the bottleneck link rate for achieving low age. When the path had a wireless access as its first hop that was the bottleneck link, the path beyond the access, with links much faster than the access, was the constraining factor with regards to minimizing age over the end-to-end path. Age being optimized at update rates much lower than typical bottleneck access link rates has interesting consequences for end-to-end flows sharing the wireless access to send updates to the cloud. We experimented with a large number of ACP+ sources (up to 80 sources and fixed physical layer rates of 6, 12 and 24 Mbps) sharing a WiFi access point to send their updates to a cloud server over the Internet. We show that ACP+ allows sources to share the access well. When the wireless access isn’t the constraining factor, given the low age minimizing rate over the end-to-end path, all sources send at the minimizing rate. As the number of sources increases, the resulting congestion over the WiFi access has ACP+ gradually reduce the rate of updates per source in a manner such that the sources together fully utilize the WiFi access link rate. While fully utilizing the access like TCP, ACP+, however, keeps age much lower than TCP congestion control algorithms. Even the packet retry rates because of collisions over WiFi are much lower than for TCP. In fact, TCP algorithms are unsuitable for age control, which we demonstrate using simulations and real-experiments in this thesis. On the other hand, ACP+’s behavior, as determined using controlled simulations, is in line with what would be expected of a good age control strategy enabling sharing of access amongst multiple sources. User devices are expected to support a mix of applications, some of which may care for high throughput and others for the freshness of information. We conclude this thesis with a study on the coexistence of ACP+ and TCP flows sharing an end-to-end Internet path over a WiFi access. In line with expectation, ACP+ flows coexisting with TCP flows remain unaffected when assigned a higher Differentiated Services Code Point (DSCP) priority when all flows originate in the same device. However, the gains from prioritization vanish when the flows are instead sharing a contended wireless access. 2022-11-01T00:00:00Z