Contemporary wireless systems have advanced toward smart and multifunctional radios such as software-defined or cognitive radios which access a wideband or multiband spectrum dynamically. It is desirable for the wireless systems to have high frequency selectivity early in the receiver chain at RF to relax the dynamic range requirements of subsequent stages. However, integration of high selectivity RF band-pass filters (BPF), or band-stop filters (BSF) is challenging because of limited quality factor (Q) of passive components in integrated circuit (IC) technology [1].
This proposed research achieves the followings:
1. Developing, and demonstrating innovative integrated band-pass filter that relaxes the performance tradeoffs in conventional LC filters to maximally increase filter reconfigurability in frequency tuning range (2-18 GHz), selectivity (Q=5~100) with superior dynamic range (DR>100 dB) at RF to microwave frequency range [2].
2. Implementing active notch filter system comprised of a Q-enhancement band-pass filter (BPF) and an all-pass amplifier. The notch response is synthesized by subtracting the BPF output from the all-pass output. In the proposed synthetic notch filters, the BPF is responsible for defining selectivity while stop-band attenuation is primarily dependent on the gain matching between the BPF and all-pass amplifier. Therefore, notch attenuation is controllable independently from the bandwidth tuning, providing more operational flexibility. Further, the filter dynamic range is optimized in the all-pass amplifier independently from the selectivity control in the BPF, resolving entrenched tradeoff between selectivity and dynamic range in active filters [3].
3. Demonstrating the mode reconfigurable LC filter that works in either BPF or BSF for a flexible blocker filtering adaptive to the dynamic blocker environments.
4. Implementing a novel feedback-based interference rejection system to improving the linearity of the BPF for high Q cases, in which the BPF Q is set to a specific value and further increase in Q is achieved using feedback gain. And finally, the second LC tank is added to increase the out of band rejection in band-pass characteristics. / Ph. D. / As many radios coexist and interference environment becomes more hostile and dynamic, it is critical to establish high frequency selectivity at the earliest possible stage in a receiver chain to avoid desensitization with a minimal power penalty. Historically, band-pass filters and band-stop filters have been used to avoid the receiver desensitization, however, the design of bandpass/band-stop filters are more challenging at radio frequencies (RF).
There are different type of RF filters including Q-enhanced LC filters and N-path filters. Qenhanced LC filters have been widely investigated for filtering blockers, but only with limited system applications due to a narrow dynamic range (DR). While, recently N-path filters are gaining growing attention, a high selectivity comes at the cost of system complexity and power penalty thereof: due to the inherent array architecture driven by multiphase clocks, the dynamic power dissipation in the N-path filter will be proportional to the increase of the filter center frequency (fc), claiming > 100’s mW when the fc is projected over 10GHz for instance. Therefore, designing on-chip RF filters are still challenging due to the strong tradeoff among selectivity, dynamic range, and power consumption.
The main goal of this research is to realize a high performance on-chip filter which is capable of mode switching between bandpass (BPF) and bandstop (BSF) for a flexible blocker filtering adaptive to the dynamic blocker environments.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/84427 |
| Date | 03 February 2017 |
| Creators | Mohammadi, Laya |
| Contributors | Electrical and ComputerEngineering, Koh, Kwang-Jin, Lu, Guo Quan, Raman, Sanjay, Reed, Jeffrey H., Ha, Dong S. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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