The first part of this thesis proposes a method to synthesize the T- and £S-prototype of band-pass filters using the two reflection zeros and the rolloff rate. According to the characteristics of passive components embedded in different substrates, £S-prototype band-pass filter is suitable for implementation on LTCC substrate, while T-prototype band-pass filter is suitable for implementation on organic substrate. The second part of this thesis employs the £S-prototype to design the LTCC band-pass filters. It has been found that mutual coupling and feedback elements can be used to create the multiple transmission zeros. With these synthesized transmission zeros, the stopband attenuation can be enhanced at several specific frequencies. For demonstration, this thesis implements the LTCC band-pass filters in 2.4 GHz ISM band and 3.5 GHz WiMAX band. The measured results show that insertion loss and return loss in the passband for these LTCC filters is less than 2 dB and more than 10 dB, respectively. In addition, these filters have the additional transmission zeros for enhancing the stopband attenuation. Moreover, miniaturization is also a key issue in implementing these LTCC filters. The 2.4 GHz and 3.5 GHz LTCC filter can meet the standard 1608 size and 2520 size, respectively, which are the smallest compared to the other LTCC filters reported for similar applications in the current literature and commercial media.

This thesis proposes an analytical method to synthesize bandpass filter with multiple transmission zeros. By using the six pre-determined parameters including two reflection zeros, two matching quality factors, and two transmission zeros, the method can exactly synthesize the corresponding prototype of second-order coupled-resonator bandpass filter. The synthesized filters not only can provide two pre-determined transmission zeros in the lower and upper side of the passband, but also can generate an extra transmission zero in the stopband. This thesis presents the prototypes of the bandpass filter and the methods of synthesis in detail. Finally this thesis implements compact LTCC bandpass filters by using the proposed synthesis method for 3.5 GHz WiMAX applications.

A novel algorithm for making the combination of outputs in the output zero direction of the plant always equal to zero was formulated. Using this algorithm and the result of MacFarlane and Karcanias, a fault detection scheme was proposed which utilizes the directional property of the multivariable linear system. The fault detection scheme is applicable to linear multivariable systems. Results were obtained for both continuous and discrete linear multivariable systems. A quadruple tank system was used to illustrate the results. The results were further verified by the steady state analysis of the plant.

This thesis proposes a novel dual passband filter architecture and develops a design flow and synthesis method for this architecture. The technical contents include the fundamental passband filter design and the further methods for generating the higher second passband and the multiple transmission zeros. This thesis organizes a design flow based on analytical formulation for the proposed dual passband filter architecture. One can follow this design flow to substitute the filter specifications into the formulation and then can obtain the necessary element values for the filter architecture that match the specified specifications. The dual passband filter architecture is finally implemented on LTCC substrate for WLAN (IEEE 802.11 a/b/g) applications with verification of S parameters using EM-simulation and actual measurement.

Phase shifters play a crucial role in radar, satellite communications, and 5G networks. Recently, the idea of using filters as phase shifters have attracted much interest due to providing many benefits such as smaller area, lower noise figure, easier fabrication method as compared with other technologies, reduced cost, and the ability to work as multi-functioning device. This work focuses on the implementation of bandstop-based and bandpass-based filtering phase shifters. For the bandstop-based approach, some of the resonating structures that were examined are stubs, LC tanks, L-shaped/U-shaped half wavelength resonators and many others. Periodic stub loading filter design method was compared against traditional filter synthesis method in order to determine which approach can provide better insertion loss range, higher phase range, and wider bandwidth. Optimization of stub impedance and the size of the device was presented. With regards to bandpass-based filtering phase shifters, microstrip-based and substrate integrated waveguide-based designs were investigated. The benefits of microstrip technology include low profile, low cost, ease of fabrication and integration. Microstrip-based designs were implemented using square shaped and octagon shaped split ring resonators. Then, substrate integrated waveguide (SIW) cavity-based designs were proposed and realized using hexagon resonators. The advantages of SIW-based filters are low insertion loss, high power handling, high immunity to external noise and crosstalk. A novel SIW-based filtering phase shifter with tunable transmission zero and tunable center frequency was developed aimed at maximizing device performance.