Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/32865
Title: LOW-POWER FREQUENCY SYNTHESIS BASED ON INJECTION LOCKING
Authors: MEHRAN MOHAMMADI IZAD
Keywords: Injection locked oscillator, pulse shaping, spur, phase shift keying, digital power amplifier
Issue Date: 28-Dec-2011
Source: MEHRAN MOHAMMADI IZAD (2011-12-28). LOW-POWER FREQUENCY SYNTHESIS BASED ON INJECTION LOCKING. ScholarBank@NUS Repository.
Abstract: Advancements in semiconductor industry have empowered consumer devices with higher performance and more functionality with significant reduction in cost due to their ability for mass production. Wireless connectivity has expanded vigorously in these devices. An ever growing demand for higher data transfer rates and lower power consumption has created new challenges on design of these wireless communication systems. Frequency synthesizer is one of the most critical building blocks in RF communication systems which generates carrier signal for transmission. Achieving agility as well as good phase noise with low power consumption has always been a challenge in the design of frequency synthesizers. In this thesis, the concept of injection locking has been used for frequency synthesis in order to increase the power efficiency of the synthesizer and achieve faster settling time. This dissertation is divided into two parts. In the first part, a low-power ultra wide band synthesizer, as the heart of a high data rate transmitter is designed. Specific emphasis is given on the design techniques to reduce the sidebands while keeping the power consumption low. This is necessary for coexistence of an ultra wide band transmitter with other potentially available standards on the same device. A novel pulse shaping is proposed to suppress the spurious tones and achieve the required level of spectral purity. Detailed analysis of the effect of circuit non-idealities on the proposed pulse shaping technique is also provided. Moreover, a new approach to estimate the level of spurious tone in injection locked LC-oscillators is developed. Finally, a prototype is implemented to demonstrate the feasibility of the idea. Experimental results on the fabricated prototype in 0.13 µm CMOS shows 22 dB of suppression in the spurious tones. In the second part, a complete ultra low-power high data rate transmitter is designed. New transmitter architecture based on injection-locked ring oscillator and digital power amplifier is proposed. This digitally intensive architecture eliminates the need for slow and power hungry phase locked loop for frequency synthesis and thus increases the power efficiency of the transmitter. Unlike conventional ultra low power radios that trade off spectral efficiency for power efficiency, the proposed architecture adopts spectral efficient 8PSK or O-QPSK modulation to achieve higher data rates. The impact of circuit non-idealities on the transmitter performance are also discussed in depth. Moreover, an analytical expression is derived to estimate the level of spurious tones in injection-locked ring oscillators. To validate the analysis and demonstrate the capability of the proposed architecture, a prototype is fabricated in 65 nm CMOS. Measurements show that the transmitter is capable of achieving a data rate of 55 Mbps while consuming only 853 µW which translate to an energy efficiency of 15.5 pJ/bit.
URI: http://scholarbank.nus.edu.sg/handle/10635/32865
Appears in Collections:Ph.D Theses (Open)

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