Transmitter architectures with digital modulators, D/A converters and switching-mode power amplifiers

This thesis is composed of nine publications and an overview of the research topic, which also summarises the work. The research described in this thesis focuses on research into the digitalisation of wireless communication base station transmitters. In particular it has three foci: digital modulation, D/A conversion and switching-mode power amplification. The main interest in the implementation of these circuits is in CMOS. The work summarizes the designs of several circuit blocks of a wireless transmitter base station. In the baseband stage, a multicarrier digital modulator that combines multiple modulated signals at different carrier frequencies digitally at baseband, and a multimode digital modulator that can be operated for three different communications standards, are implemented as integrated circuits. The digital modulators include digital power ramping and power level control units for transmission bursts. The upconversion of the baseband signal is implemented using an integrated digital quadrature modulator. The work presented provides insight into the digital-to-analogue interface in the transmitters. This interface is studied both by implementing an intermediate frequency D/A converter in BiCMOS technology and bandpass Delta-Sigma modulator-based D/A conversion in CMOS technology. Finally, the last part of the work discusses switching-mode power amplifiers which are experimented with both as discrete and integrated implementations in conjunction with 1-bit Delta-Sigma modulation and pulse-width modulation as input signal generation methods.Tämä väitöskirja koostuu yhdeksästä julkaisusta ja tutkimusaiheen yhteenvedosta. Väitöskirjassa esitetty tutkimus keskittyy langattaman viestinnän tukiasemien lähettimien digitalisoinnin tutkimukseen. Yksityiskohtaisemmin tutkimusalueet ovat: digitaalinen modulaatio, D/A muunnos ja kytkinmuotoiset tehovahvistimet. Näiden elektronisten piirien toteutuksessa keskitytään CMOS teknologiaan. Työ vetää yhteen useiden langattoman viestinnän tukiasemien lähettimien piirilohkojen suunnittelun. Kantataajuusasteella toteutetaan integroituna piirinä monikantoaaltoinen digitaalinen modulaattori, joka yhdistää useita moduloituja signaaleja eri kantoaalloilla digitaalisesti ja monistandardi digitaalinen modulaatori, joka tukee kolmea eri viestintästandardia. Digitaaliset modulaattoripiirit sisältävät digitaalisen tehoramping ja tehotason säätöyksikön lähetyspurskeita varten. Kantataajuussignaalin ylössekoitus toteutetaan integroitua digitaalista kvadratuurimodulaattoria käyttäen. Esitetty työ antaa näkemystä lähettimien digitalia-analogia rajapintaan, jota tutkitaan toteuttamalla välitaajuinen D/A muunnin BiCMOS teknologialla ja päästökaistainen Delta-Sigma-modulaattoripohjainen D/A muunnin CMOS teknologialla. Lopuksi työn viimeinen osa käsittelee kytkinmuotoisia tehovahvistimia, joita tutkitaan kokeellisesti sekä erilliskompontein toteutettuina piirein että integroiduin piirein toteutettuina käyttäen sisääntulosignaalin muodostamismenetemänä yksibittistä Delta-Sigma-modulaatiota ja pulssin leveys modulaatiota.reviewe

ENABLING HARDWARE TECHNOLOGIES FOR AUTONOMY IN TINY ROBOTS: CONTROL, INTEGRATION, ACTUATION

The last two decades have seen many exciting examples of tiny robots from a few cm3 to less than one cm3. Although individually limited, a large group of these robots has the potential to work cooperatively and accomplish complex tasks. Two examples from nature that exhibit this type of cooperation are ant and bee colonies. They have the potential to assist in applications like search and rescue, military scouting, infrastructure and equipment monitoring, nano-manufacture, and possibly medicine. Most of these applications require the high level of autonomy that has been demonstrated by large robotic platforms, such as the iRobot and Honda ASIMO. However, when robot size shrinks down, current approaches to achieve the necessary functions are no longer valid. This work focused on challenges associated with the electronics and fabrication. We addressed three major technical hurdles inherent to current approaches: 1) difficulty of compact integration; 2) need for real-time and power-efficient computations; 3) unavailability of commercial tiny actuators and motion mechanisms. The aim of this work was to provide enabling hardware technologies to achieve autonomy in tiny robots. We proposed a decentralized application-specific integrated circuit (ASIC) where each component is responsible for its own operation and autonomy to the greatest extent possible. The ASIC consists of electronics modules for the fundamental functions required to fulfill the desired autonomy: actuation, control, power supply, and sensing. The actuators and mechanisms could potentially be post-fabricated on the ASIC directly. This design makes for a modular architecture. The following components were shown to work in physical implementations or simulations: 1) a tunable motion controller for ultralow frequency actuation; 2) a nonvolatile memory and programming circuit to achieve automatic and one-time programming; 3) a high-voltage circuit with the highest reported breakdown voltage in standard 0.5 μm CMOS; 4) thermal actuators fabricated using CMOS compatible process; 5) a low-power mixed-signal computational architecture for robotic dynamics simulator; 6) a frequency-boost technique to achieve low jitter in ring oscillators. These contributions will be generally enabling for other systems with strict size and power constraints such as wireless sensor nodes