No description available.

No description available.

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.

In radio frequency (RF), filtering is an essential part of RF transceivers. They are employed for different purposes of band selection, channel selection, interference cancellation, image rejection, etc. These are all translated in selecting the wanted signal while mitigating the rest. This can be performed by either selecting the desired frequency range by a band pass filter or rejecting the unwanted part by a band stop filter. Although there has been tremendous effort to design RF tunable filters, there is still lack of designs with frequency and bandwidth software-tuning capability at frequencies above 4 GHz. This prevents the implementation of Software Defined Radios (SDR) where software tuning is a critical part in supporting multiple standards and frequency bands. Designing a tunable integrated filter will not only assist in realization of SDR, but it also causes an enormous shrinkage in the size of the circuit by replacing the current bulky off-chip filters. The main purpose of this research is to design integrated band pass and band stop filters aimed to perform interference cancellation. In order to do so, two systems are proposed for this thesis. The first system is a band pass filter capable of frequency and band with tuning for C band frequency range (4-8 GHz) and is implemented in 0.13 µm BiCMOS technology. Frequency tunability is accomplished by using a variable capacitor (varactor) and bandwidth tuning is carried out by employing a negative transconductance cell to compensate for the loss of the elements. Additional circuitry is added to the band pass filter to enhance the selectivity of the filter. The second system is a band stop filter (notch) with the same capability as the band pass filter in terms of tuning. This system is implemented in C band, similar to its band stop counterpart and is capable of tuning its depth by using a negative transconductance in an LC tank. A negative feedback is added to the circuit to improve the bandwidth. While implemented in the same process as the band pass filter, it only employs CMOS transistors since it is generally more attractive due to its lower cost and scalability. Both of the systems mentioned use a varactor for changing the center frequency which is a nonlinear element. Therefore, the nonlinearity of it is modelled using two different methods of nonlinear feedback and Volterra series in order to gain further understanding of the nonlinear process taking place in the LC tank. After the validation of the models proposed using Cadence Virtuoso simulator, two methods of design and tuning are suggested to improve the linearity of the system. After post layout-extraction, the band pass filter is capable of Q tuning in the range of 3 to 270 and higher. With the noise figure of 10 to 14 dB and input 1-dB compression point as high as 2 dBm, the system shows a reasonably good performance along its operating frequency of 4 to 8 GHz. The band stop filter which is designed in the same frequency band can achieve better than 55 dB of rejection with the noise figure of 6.7 to 8.8 dB and 1-dB compression point of -4 dBm. With the power consumption of 39 to 70 mW, the band stop filter can be used in a low power receiver to suppress unwanted signals. The technique used in the band stop filter can be applied to higher frequency ranges if the circuit is implemented in a more advanced silicon technology. Implementing the mentioned filters in a receiver along with other elements of low noise amplifiers, mixers, etc. would be a major step toward full implementation of SDR systems. Studying the linearity theory of varactors would help future designers identify the sources of nonlinearity and suggest more efficient tuning techniques to improve the linearity of RF electronic systems. / Master of Science

No description available.

This thesis deals with concept of universal frequency filter by application of a switched-capacitor functional block. The concept is based on the theory of switched-capacitor circuits and the theory of a design of classical frequency filters. The printed circuit board was designed based on the filter connection developed by using a software Eagle. The filter was implemented as a laboratory product. This product has been revitalized and the frequency response of all types of filters has been measured. The measured parameters were compared with the parameters set out in the technical documentation of functional block.