The k-means clustering algorithm has been implemented to find patterns in the time-averaged stored energy distribution in various filter networks. A large data set comprising of numerous topologies for 50 different single band specifications has been investigated. By finding key characteristics within this data set, general guidelines for predicting the optimum topology for power handling have been established.
A new concept for the design of power combiners based on matched directional filters is presented. The directional filters consist of individual balanced sections composed of hybrids and single resonators. Each of the sections corresponds to a pole of an all-pass function composed of the sum of S 11 and S 12 of the desired filter transfer function. A simple synthesis method is presented. The filter combiner has the advantage of ease of tunability because each pole is associated with a single resonator. Furthermore, no cross couplings are required to realize finite frequency transmission zeros.
The study investigates the impact of compulsory computer studies (CS) on information and communication technology (ICT) literacy in secondary schools in the Livingstone District, Zambia. The objectives were to investigate the availability of specialised ICT teachers, to find out the availability of ICT equipment and infrastructure, and to establish the impacts of compulsory ICT. The study was mainly qualitative using primary data, however, had a component of quantitative research using secondary data in form of Examination Council of Zambia (ECZ), ICT examinations results for grade nine. The study established that the introduction of ICT as a compulsory subject had an impact on teacher and pupil literacy in ICT, and due to insufficient ICT equipment, may have negatively affected the performance of the pupils in the ICT final examination.
A general and direct synthesis of $N_{p}$ poles pseudo-elliptic inline filters having $N_{p}$ purely real and/or imaginary frequency transmission zeros is presented. Using an appropriate model of the resonators (bandpass distributed or lumped element) and shifting the reference planes at the input and output of the filter network, a novel direct synthesis and realization of filters based on frequency variant coupling (inductive or capacitive) in the distributed domain is demonstrated for accurate modeling of narrow and broadband filters. First, a complete general synthesis procedure is described that allows for flexible or mixed topologies realizing transmission zeros anywhere on the frequency plane (including complex and infinite frequencies). Furthermore, by exploiting the power of modular design, a synthesis procedure that enables simultaneous extraction of reflection zero (a pole) and a transmission zero in the form of a symmetrical and physically realizable singlet as an elementary unit is showcased. The physical dimensions of the extracted singlets are independently determined in any chosen technology, and the overall filter is obtained by directly cascading the physical singlets. To validate this novel synthesis technique, three design examples are shown: a narrowband four-pole, four transmission zeros (fully canonical) filter from literature is synthesized and physically dimensioned, a wideband three-pole, three transmission zero (fully canonical) filter, and a broadband three-pole, one transmission zero, filter. In the first two examples, each of the singlet blocks was implemented in an overmoded rectangular waveguide cavity operating at the TE201 mode coupled at the input and output to the fundamental nonresonating TE10 mode. The third example was implemented in a re- entrant coaxial resonator operating at the fundamental mode. The simulation of the electromagnetic (EM) [high-frequency structure simulator (HFSS)] models of the overall example filters was in excellent agreement with the synthesized models, thereby validating the effectiveness of the proposed synthesis technique. Furthermore, the measured results of the fabricated wide bandpass filter showed close agreement with synthesis and EM model.
High speed mobile internet results in better user experience and satisfied subscriber. However factors that affect the download speed include transfer technology, number of subscribers sharing the connection, device capability and radio conditions at the subscriber location. This research was conducted to review the mobile internet performance in Zambia and determine its conformity to the regulator, ZICTA, QoS regulation. Two sets of empirical data were collected in the capital city, first in 2021 during the covid pandemic period and second in 2024. The data was compared to check for network operator developments. The results reveal that two MNOs acquired new 2600MHz spectrum, however only one MNO drew maximum benefit resulting in improved 4G download speeds. This improvement was despite an increase in market share over the same period. The second operator that deployed the 2600MHz LTE TDD mode spectrum recorded a degradation in overall downloads speeds when compared to the initial data set in spite of a reduction in market share over the same period. Thus the steps to improve the LTE network are to add more spectrum to at least reach the 3GPP Rel 10 standard of 5 carrier configuration (5CC) to reach a total 100MHz and configure network features like Carrier Aggregation (CA) to provide for higher throughputs for capable devices. Other ways to expand LTE network include add more antennas to allow for higher spectral efficiency using 8 x 8 MIMO or more and thirdly deploy Small cells solution to enhance coverage and capacity in both indoor and outdoor environment.
Firstly, a new synthesis method for the generation of the generalized Chebyshev characteristic polynomials has been presented. The general characteristic function is generated by a linear combination of Chebyshev basis characteristic functions. The basis functions for different filtering functions may easily be determined based on the number and position of reflection and transmission zeros. These basis functions enable direct synthesis of both lumped and distributed filter networks. Different filter functions including but not limited to low-pass, bandpass and dual bandpass filters, have been synthesised to demonstrate the general application of the synthesis method.
Secondly, a new method for the design of a new class of distributed low-pass filter has been presented that enables exact realisation of the series short circuited transmission lines which are normally approximated via unit elements in other filter realisations. The filters are based on parallel coupled high impedance transmission lines which are terminated at one end in open-circuited stubs. The approach enables realisation of both finite and quarter-wave frequency transmission zeros hence giving improved stopband performance. A complete design is presented and the fabricated low-pass filter demonstrates excellent performance in good agreement with theory.
Finally, design techniques for microwave bandpass filters using re-entrant resonators are presented. The key feature is that each re-entrant resonator in the filter generates a passband resonance and a finite frequency transmission zero, above the passband. Thus an Nth degree filter can have N finite frequency transmission zeros with a simple physical realization. A new synthesis technique for pseudo-elliptic low-pass filters suitable for designing re-entrant bandpass filter has also been show-cased. A physically symmetrical 5 pole re-entrant bandpass prototype filter with 5 transmission zeros above the passband was designed and fabricated. Measured results showed good correspondence with theories.
A new synthesis method for the generation of the generalized Chebyshev characteristic polynomials has been presented. The general characteristic function is generated by linear combination of elementary Chebyshev characteristic functions. The characteristic function is suitable for synthesis of dual bandpass filters as well as direct synthesis for single bandpass filters.
A new concept for the design of power combiners based on matched directional filters is presented. The directional filters consist of individual balanced sections composed of hybrids and single resonators. Each of the sections corresponds to a pole of an all‐pass function composed of the sum of S 11 and S 12 of the desired filter transfer function. A simple synthesis method is presented. The filter combiner has the advantage of ease of tunability because each pole is associated with a single resonator. Furthermore, no cross‐couplings are required to realise finite frequency transmission zeros. Experimental results for a prototype device are presented.
Design techniques for microwave bandpass filters using re-entrant resonators are presented. The key feature is that each re-entrant resonator in the filter generates a passband resonance and a finite frequency transmission zero above the passband. Thus, an N th degree filter can have N finite frequency transmission zeros with a simple physical realization. A physically symmetrical five-pole re-entrant bandpass filter prototype with five transmission zeros above the passband was designed and fabricated. Measured results showed good correspondence with theories.
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