Phase Generation and Manipulation in CMOS Integrated Circuits

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Yong, Gideon S. K.
CMOS , Integrated circuits , Phase generation , Phase manipulation , Microwave , Radio frequency
In this thesis three circuits are presented that demonstrate the creation and manipulation of various phases over a large bandwidth. Many systems demand the interoperability of various circuit blocks over a large frequency range in order to minimize costs. In addition, the use of low resistivity silicon facilitates a further reduction in costs. The circuits presented in this thesis demonstrate both these key concepts by using the conventional CMOS process in addition to operating over large bandwidths which is ideal for inclusion in any number of standard wireless systems. A new novel balun is proposed that achieves wideband performance through the use of an external compensating capacitor to counter the effects of parasitic capacitances that reduce its effective bandwidth. An input stage common gate amplifier is then used to improve the return loss and provide additional gain. The fabricated active balun using the proposed circuit shows that the device performs with a 7.5 GHz bandwidth. In addition an excellent 16 dB return loss, -5.8 dBm compression point and 12 mW power consumption are also reported. Following this, an inductorless quadrature oscillator is proposed using an artificial resonator composed of conventional OTA circuits in order to increase the tuning range. The measured tuning range was found to be 100 MHz. This circuit demonstrates the ability to use a synthetic resonator circuit as a method of achieving wide tuning. The measured phase noise of -97.7 dBc/Hz is on par with other inductorless oscillators found in literature. Finally a wideband feedback quadrature generator is presented. Existing circuits do not provide a wide frequency of operation and in addition are highly susceptible to variances in component values used. The result is that the fabricated system will not operate at its intended operating frequency. In order to mitigate this problem a RC-CR network was used in conjunction with two variable gain amplifiers that uses a feedback network to actively compensate the amplitude imbalance over a large frequency range. This new design first is of its kind and the resulting circuit is measured to have over a 4 GHz bandwidth while maintaining a +/- 1 dB amplitude balance.
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