Analysis and Design of Low-Cost Waveguide Filters for Wireless Communications

The area of research of this thesis is built around advanced waveguide filter structures. Waveguide filters and the waveguide technology in general are renowned for high power capacity, low losses and excellent electromagnetic shielding. Waveguide filters are important components in fixed wireless communications as well as in satellite and radar systems. Furthermore, their advantages and utilization become even greater with increase in frequency, which is a trend in modern communication systems because upper frequency bands offer larger channel capacities. However, waveguide filters are relatively bulky and expensive. To comply with more and more demanding miniaturization and cost-cutting requirements, compactness and economical design represent some of the main contemporary focuses of interest. Approaches that are used to achieve this include use of planar inserts to build waveguide discontinuities, additive manufacturing and substrate integration. At the same time, waveguide filters still need to satisfy opposed stringent requirements like small insertion loss, high selectivity and multiband operation. Another difficulty that metal waveguide components face is integration with other circuitry, especially important when solid-state active devices are included. Thus, improvements of interconnections between waveguide and other transmission interfaces are addressed too. The thesis elaborates the following aspects of work: Further analysis and improved explanations regarding advanced waveguide filters with E-plane inserts developed by the Wireless Communications Research Group, using both cross coupled resonators and extracted pole sections (Experiments with higher filter orders, use of tuning screws, degrees of freedom in design, etc. Thorough performance comparison with competing filter technologies) - Proposing novel E-plane filter sections with I-shaped insets - Extension of the E-plane filtering structures with metal fins to new compact dual band filters with high frequency selectivity and miniaturized diplexers. - Introduction of easy-to-build waveguide filters with polymer insert frames and high-performance low-profile cavity filters, taking advantage of enhanced fabrication capabilities when using additive manufacturing - Developing new substrate integrated filters, as well as circuits used to transfer signals between different interfaces Namely, these are substrate integrated waveguide to metal waveguide planar transitions that do not require any modifications of the metal waveguides. Such novel transitions have been designed both for single and orthogonal signal polarizations

Compact Inline E plane Waveguide Resonators and Bandpass Filters with I-shaped Resonant Insets

In this paper, waveguide resonators and bandpass filters with E-plane inserts containing I-shaped resonant insets are presented. These insets introduce to the response finite transmission zeros much less sensitive than those produced by cross-couplings. Also, their use results in structure compactness, unlike bandstop resonant cavities that add volume. Two kinds of extracted pole sections that demonstrate response flexibility of the proposed resonators are designed at 10 GHz and tested. One is based on the dominant mode with a transmission zero in the upper stopband and the other on a pair of higher order modes with a transmission zero in the lower stopband. Also, a 3rd order filter for 11 GHz band combining both dominant and higher order mode resonators is modeled to illustrate the scalability of such a modular design. These filters are very suitable for low-cost mass production

A Fully Planar Substrate Integrated Probe-Based Wideband Orthomode Transducer

This paper introduces a planar orthomode transducer (OMT) using substrate integrated waveguides (SIWs) and substrate integrated coaxial lines (SICLs) that is entirely contained within two substrate layers. SICLs form a quadruplet of probes inside the metal waveguide with fully symmetrical geometry. Such a structure is smaller and lighter than a waveguide OMT, its construction is simpler than of a coaxial OMT, however, isolation and loss properties are less degraded compared to the use of planar unshielded technologies such as microstrip. A new wideband inline SICL to SIW transition has been developed to allow grade separation of SIWs belonging to opposite polarizations through different substrate layers. The designed substrate integrated probe-based OMT on RO4003CTM substrate covers the frequency band from 8.1 to 12.5 GHz with return loss higher than 19 dB, insertion loss less than 1.2 dB, inter-port isolation higher than 62 dB and cross-polarization discrimination higher than 65 dB

Substrate Integrated Coaxial Line Planar Transitions to Single-Layer Transmission Lines and Waveguides

This paper presents inline transitions from substrate integrated coaxial line (SICL) to microstrip line, coplanar waveguide (CPW), as well as substrate integrated waveguide (SIW). A common property is the conversion of transmission medium from double to single substrate layer of PCB. The first two of described transitions can be used from DC up to the presence of higher order modes if the characteristic impedances of two meeting transmission lines are matched. The transition to substrate integrated waveguide is of higher complexity, yet compact. Both sides of the SICL-SIW transition are strongly coupled to resonant cavity, and return loss greater than 20 dB is achieved in fractional bandwidth of 10.91 %. Improvements compared to the existing solutions have been made in designs of all three transitions

Hybrid Manufactured Waveguide Resonators and Filters for mm-Wave Applications

Additive and hybrid manufactured waveguide resonators and bandpass filters for mm-wave applications are presented. A Ka band 3D printed waveguide resonator with inductive windows and 28 GHz 5G band hybrid manufactured waveguide resonator and bandpass filter are designed. Hybrid manufacturing combines 3D polymer printing and conventional metal processing technologies. In order to illustrate the accuracy of the design, a 3D printed waveguide transmission line and resonator with the resonant frequency of 33 GHz are fabricated and tested

Ultra Compact Inline E-Plane Waveguide Bandpass Filters Using Cross Coupling

This paper presents novel ultra-compact waveguide bandpass filters that exhibit pseudo elliptic responses with ability to place transmission zeros on both sides of the passband to form sharp roll offs. The filters contain E plane extracted pole sections cascaded with cross-coupled filtering blocks. Compactness is achieved by the use of evanescent mode sections and closer arranged resonators modified to shrink in size. The filters containing non-resonating nodes are designed by means of the generalized coupling coefficients (GCC) extraction procedure for the cross-coupled filtering blocks and extracted pole sections. We illustrate the performance of the proposed structures through the design examples of a third and a fourth order filters with center frequencies of 9.2 GHz and 10 GHz respectively. The sizes of the proposed structures suitable for fabricating using the low cost E plane waveguide technology are 38% smaller than ones of the E plane extracted pole filter of the same order

Low-Cost Hybrid Manufactured Waveguide Bandpass Filters with 3D Printed Insert Dielectric

In this paper, a new type of simple and inexpensive waveguide filter manufacturing that minimizes material consumption and has capabilities of high performance and rapid prototyping is presented. Filter inserts are fabricated by a combination of additive dielectric manufacturing and subtractive metal manufacturing, whereas standard waveguides are used as housings, utilizing best properties of each technology. Along with it, a suitable filter design using metal rectangular rings has been developed. Since the rings that act as positive reactance discontinuities in the passband are resonant at frequencies below it, it is possible to bring lower stopband transmission zeros near the passband to create sharp skirt. A resonator of such a filter and a third order bandpass filter sample have been designed at 11.13 GHz and 11.36 GHz centre frequencies respectively. In addition, smaller size rectangular rings in waveguide can realize upper stopband transmission zeros while acting as negative reactance discontinuities in the passband. This was utilized in fourth order bandpass filter at 11.36 GHz centre frequency with finite transmission zeros in both stopbands. All the filtering structures have been fabricated with 3D printer to extrude polylactic acid and circuit board plotter to mill copper sheet, and tested. Excellent measurement results that have been obtained validate the proposed design. Practical sides of achieving quality 3D printouts are analysed

A simple method to assess freezing of gait in Parkinson's disease patients

Freezing of gait (FOG) can be assessed by clinical and instrumental methods. Clinical examination has the advantage of being available to most clinicians; however, it requires experience and may not reveal FOG even for cases confirmed by the medical history. Instrumental methods have an advantage in that they may be used for ambulatory monitoring. The aim of the present study was to describe and evaluate a new instrumental method based on a force sensitive resistor and Pearson's correlation coefficient (Pcc) for the assessment of FOG. Nine patients with Parkinson's disease in the "on" state walked through a corridor, passed through a doorway and made a U-turn. We analyzed 24 FOG episodes by computing the Pcc between one "regular/normal" step and the rest of the steps. The Pcc reached +/- 1 for "normal" locomotion, while correlation diminished due to the lack of periodicity during FOG episodes. Gait was assessed in parallel with video. FOG episodes determined from the video were all detected with the proposed method. The computed duration of the FOG episodes was compared with those estimated from the video. The method was sensitive to various types of freezing; although no differences due to different types of freezing were detected. The study showed that Pcc analysis permitted the computerized detection of FOG in a simple manner analogous to human visual judgment, and its automation may be useful in clinical practice to provide a record of the history of FOG

Enforced Expression of the Transcriptional Coactivator OBF1 Impairs B Cell Differentiation at the Earliest Stage of Development

OBF1, also known as Bob.1 or OCA-B, is a B lymphocyte-specific transcription factor which coactivates Oct1 and Oct2 on B cell specific promoters. So far, the function of OBF1 has been mainly identified in late stage B cell populations. The central defect of OBF1 deficient mice is a severely reduced immune response to T cell-dependent antigens and a lack of germinal center formation in the spleen. Relatively little is known about a potential function of OBF1 in developing B cells. Here we have generated transgenic mice overexpressing OBF1 in B cells under the control of the immunoglobulin heavy chain promoter and enhancer. Surprisingly, these mice have greatly reduced numbers of follicular B cells in the periphery and have a compromised immune response. Furthermore, B cell differentiation is impaired at an early stage in the bone marrow: a first block is observed during B cell commitment and a second differentiation block is seen at the large preB2 cell stage. The cells that succeed to escape the block and to differentiate into mature B cells have post-translationally downregulated the expression of transgene, indicating that expression of OBF1 beyond the normal level early in B cell development is deleterious. Transcriptome analysis identified genes deregulated in these mice and Id2 and Id3, two known negative regulators of B cell differentiation, were found to be upregulated in the EPLM and preB cells of the transgenic mice. Furthermore, the Id2 and Id3 promoters contain octamer-like sites, to which OBF1 can bind. These results provide evidence that tight regulation of OBF1 expression in early B cells is essential to allow efficient B lymphocyte differentiation