Showing papers on "Prototype filter published in 2018"

Analytical Design of Passive LCL Filter for Three-Phase Two-Level Power Factor Correction Rectifiers

Abstract: This paper proposes a comprehensive analytical LCL filter design method for three-phase two-level power factor correction rectifiers (PFCs) The high-frequency converter current ripple generates the high-frequency current harmonics that need to be attenuated with respect to the grid standards Studying the high-frequency current of each element proposes a noniterative solution for designing an LCL filter In this paper, the converter current ripple is thoroughly analyzed to generalize the current ripple behavior and find the maximum current ripple for sinusoidal pulse width modulation (PWM) and third-harmonic injection PWM Consequently, the current ripple is used to accurately determine the required filter capacitance based on the maximum charge of the filter capacitor To choose the grid-side inductance, two methods are investigated First method uses the structure of the damping to express the grid-side filter inductance as a function of the converter current ripple Reducing the power loss in the filter and optimizing the grid-side filter inductance is the main focus of the second method which is achieved by employing line impedance stabilization network (LISN) Accordingly, two LCL filters are designed for a 5 kW silicon-carbide-based three-phase PFC Various experimental scenarios are performed to verify the filters attenuation and performance

A Simple Planar Dual-Band Bandpass Filter With Multiple Transmission Poles and Zeros

Abstract: A simple and planar design structure for dual-band bandpass filter (BPF) with multiple transmission poles and zeros is proposed in this brief. According to frequency response transformation, two passbands are realized on both sides of the operation frequency. Sharp selectivity and high isolation level with eight transmission poles and seven transmission zeros are achieved just by employing three-section coupled lines and three short-circuit stubs. Besides, the analytical (closed-form) extraction process for the transmission poles and zeros of the proposed dual-band BPF is presented based on the rigorous scattering-parameters theory and the even- and odd-mode analysis method. A prototype for the dual-band BPF with 3-dB fractional bandwidth of 41.1% and 19.0% is designed and fabricated. The measured and simulated results are in good agreement to verify the validity of the proposed design principle.

Pruned DFT-Spread FBMC: Low PAPR, Low Latency, High Spectral Efficiency

Abstract: We propose a novel modulation scheme which combines the advantages of filter bank multi-carrier (FBMC)-offset quadrature amplitude modulation and single-carrier frequency-division multiple access (SC-FDMA). On the top of a conventional FBMC system, we develop a novel precoding method based on a pruned discrete Fourier transform (DFT) in combination with one-tap scaling. The proposed technique has the same peak-to-average power ratio as SC-FDMA but does not require a cyclic prefix and has much lower out-of-band emissions. Furthermore, our method restores complex orthogonality, and the ramp-up and ramp-down period of FBMC is dramatically decreased, allowing low latency transmissions. Compared to pure SC-FDMA, the computational complexity of our scheme is only two times higher. Simulations over doubly selective channels validate our claims, further supported by a downloadable MATLAB code. Note that pruned DFT-spread FBMC can equivalently be interpreted as a modified SC-FDMA transmission scheme. In particular, the requirements on the prototype filter are less strict than in conventional FBMC systems.

Anti-EMI Noise Digital Filter Design for a 60-kW Five-Level SiC Inverter Without Fiber Isolation

Abstract: Silicon carbide (SiC) power devices are beneficial to the converters in terms of size reduction and efficiency increase Nevertheless, the fast switching of SiC devices results in more serious electromagnetic interference (EMI) noise issue Optical fibers based isolation provides a reliable solution to block the EMI noises from the power circuit to the control circuit but with additional cost and size penalty, especially for multilevel converters This letter aims at the digital filters based solution to suppress the sampling noise caused by EMI without any extra hardware cost An improved median filter and a novel magnitude bandpass filter are proposed The design tradeoffs among noises filter capability, delay effect and the computation time have been discussed for proposed filters The anti-EMI noise function of proposed filters has been experimentally verified in a 60-kW five-level SiC inverter

Design and Evaluation of a Novel Short Prototype Filter for FBMC/OQAM Modulation

Abstract: Filter-bank multi-carrier with offset quadrature amplitude modulation (FBMC/OQAM) is considered by recent research projects as one of the key enablers for the future 5G air interface. It exhibits better spectral shape and improves mobility support compared to orthogonal frequency-division multiplexing (OFDM) thanks to the use of a time and frequency localized prototype filter. The choice of this filter is crucial for FBMC/OQAM, due to its substantial impact on achieved performance and complexity levels. In the context of 5G, short frame sizes are foreseen in several communication scenarios to reduce system latency, and therefore short filters are preferred. In this context, a novel short filter allowing for near perfect reconstruction and having the same size as one OFDM symbol is proposed. Using frequency-spread (FS) implementation for the FBMC/OQAM receiver, analytical analysis and simulation results show that the proposed filter exhibits better robustness to several types of channel impairments when compared to state-of-the-art prototype filters and OFDM modulation. In addition, FS-based hardware architecture of the filtering stage is proposed, showing lower complexity than the classical polyphase network-based implementation.

Band-Reconfigurable Filter With Liquid Metal Actuation

Abstract: A substrate integrated waveguide band-reconfigurable filter with four configurations: 1) dual band; 2) low band; 3) high band; and 4) no-band, is presented. Liquid metal is chosen to enable switching between the different configurations by filling or emptying certain via holes and channels. By altering the liquid metal placement in the filter, cavity boundaries and transmission lines are adjusted to obtain the desired response. In order to demonstrate the concept, a prototype filter in C-band is designed and fabricated. The frequency responses of the liquid-metal-actuated filter (in all operating configurations) are compared with simulated and fabricated copper-plated filters. Good agreement is observed between the simulation results and the measurements. For the single- and dual-band filter configurations, insertion loss less than 1.9 dB and return loss greater than 16 dB are achieved at the center frequencies of 4.6 and 7 GHz. For the no-band (or all-stop) configuration, isolation is better than 36 dB over the entire band between 4 and 8 GHz. Additionally, to quantify the impact of using liquid metal, unloaded quality factors of a fabricated liquid-metal-actuated and copper-plated resonator are compared. The presented filter clearly demonstrates the potential of using liquid metal actuation in future reconfigurable RF hardware.

Frequency- and Bandwidth-Tunable Bandstop Filter Containing Variable Coupling Between Transmission Line and Resonator

Abstract: This paper presents a frequency- and bandwidth-tunable bandstop filter using substrate-integrated wave- guide (SIW) resonators. For designing such a filter, this paper also presents a tunable coupling structure between a microstrip line and an SIW resonator for obtaining the bandwidth tuning capability. The coupling structure has two coupling slots between the microstrip line and the resonator, and the phase shift between the two slots determines the overall external coupling value of the resonator. This external coupling value can be controlled by making use of a phase shifter, which in turn makes it possible to adjust the bandwidth of a bandstop filter. A thorough mathematical analysis is shown using the equivalent circuit model of the presented coupling structure, and it has been verified by measuring an SIW resonator containing the presented structure. The presented tunable coupling structure has also been applied to a design of bandstop filter that can be tuned from 2.8 to 3.4 GHz. The measured results at 3.1 GHz show that the bandwidth can be tuned from 0 (all-pass) to 96 MHz reaching the attenuation level of 44 dB.

Band-Switchable Substrate-Integrated Waveguide Resonator and Filter

Abstract: In this paper, we present a new band-switchable substrate-integrated waveguide (SIW) filter structure and its design method. The filter can have a passband either in ${S}$ - or ${X}$ -band, or have two passbands—one in ${S}$ -band and the other one in ${X}$ -band—at the same time. The presented design method allows us to obtain the bandwidths of two passbands independently. To verify the presented filter structure and design method, we have designed, fabricated, and measured three bandpass filters having three different pairs of bandwidths using frequency-tunable SIW resonators. By virtue of the frequency-tunable resonators, the filter can be continuously tuned in both frequency bands.

A Design Method of Multimode Multiband Bandpass Filters

Abstract: In this paper, a general design method for multiband filters is proposed. First, the frequency and element transformations from a low-pass prototype filter to a practical multiband bandpass filter is derived. Afterwards, formulas for extracting the coupling coefficient $k$ between coupled multimode resonators and the external quality factor $Q_{e}$ are also obtained. Thereafter, the design procedure of coupled multiresonator multiband filters is similar to that of single-band filters. A tri-band microstrip filter with tri-mode resonators is successfully designed with the proposed method and fabricated, which validates this theory.

Compact Frequency and Bandwidth Tunable Bandpass–Bandstop Microstrip Filter

Abstract: This letter presents the design and implementation of a compact microstrip filter with frequency and bandwidth (BW) reconfiguration. The proposed filter consists of a transmission line coupled with a U-shaped microstrip line resonator. Varactor diodes are deployed at specific locations and are tuned to achieve BW and frequency reconfiguration from 0.8 to 1.5 GHz. The transition from the bandpass mode to the bandstop mode is achieved by reconfiguring the transmission zeros simultaneously. The filter percentage lower passband edge tuning and 17.33% higher passband edge tuning. The proposed filter has simple geometry, low profile, and offers a higher level of operational flexibility in the designed frequency range. The filter is tuned with the help of simple actuators requiring simple bias circuitry. The prototype filter is fabricated, and the simulation results are validated using the experimental measurements.

A New Active Output Filter (AOF) for Variable Speed Constant Frequency (VSCF) Power System in Aerospace Applications

Abstract: In this paper a new “active output filter” (AOF) for variable speed constant frequency (VSCF) power system in aerospace applications is proposed. The proposed AOF is envisioned as a power semiconductor filter block. In the proposed system the passive L-C output filter components are replaced by an H-bridge. The H-bridge is operated at high frequency to inject voltage harmonics to achieve a sinusoidal output voltage to the load. Advanced wide band gap devices can be employed in the design of AOF block to obtain high performance with simultaneous reduction in size. The proposed AOF concept offers a significant reduction in size/weight compared to passive L-C. Further, in the presence of AOF the main VSCF inverter can be operated in a six-step and/or at a reduced PWM frequency. An example 250 kVA, 3-phase 400-Hz system with the proposed AOF concept is evaluated via simulation with a corresponding passive L-C filter configuration. Experimental results on reduced kVA laboratory prototype are discussed.

Tunable Constant-Bandwidth Substrate-Integrated Bandstop Filters

Abstract: A new method for designing tunable bandstop filters with constant fractional and absolute bandwidths (ABWs) is presented. The constant bandwidth is achieved through a new coupling structure, which is passive and consists only of coupling elements and transmission lines. Its theory of operation is presented, and design principles and tradeoffs are examined in detail. Several prototype filters are fabricated and measured to demonstrate the performance and versatility of this method. An octave-tunable filter with less than 12% fractional bandwidth variation is demonstrated, along with an octave-tunable filter with 12.3% variation in ABW variation, a filter with a 50% tuning range and less than 4% variation in ABW, and a four-pole octave-tunable filter with less than 4% variation in its 10-dB ABW. These results represent state-of-the-art performance when compared to other constant-bandwidth bandstop filters at frequencies higher than those compatible with lumped-element filters.

Mixed Lumped and Distributed Circuits in Wideband Bandpass Filter Application for Spurious-Response Suppression

Abstract: Mixed lumped and distributed circuits (MCs) have been analyzed and applied in a wideband bandpass filter (BPF) synthesis procedure for spurious-response suppression First, an MC is proposed and compared with the conventional commensurate line With the even–odd mode analysis, the MC is decomposed into an inverter and the shunt stubs on the two sides, which finds its lowpass equivalent circuit Then, constant and frequency mapping functions, simply formed by two basis functions, are derived to link the MC and its lowpass equivalent circuit With this technique, the lowpass prototype filter can be mapped to its BPF counterpart Finally, the BPF design variables are obtained by comparing the input admittances of the even/odd mode in the MC or the shunt stubs to the basis functions A fifth-order ladder type BPF has been implemented following the proposed procedure The experimental results accurately predict both wide passband and spurious-response rejection band

New Models for the Calibration of Four-Channel Time-Interleaved ADCs Using Filter Banks

Abstract: New linear models to calibrate four-channel time-interleaved analog-to-digital converters are proposed and investigated. The ideal four-periodic correction filters, which cancel distortions, are computed as a function of the error filters that model the analog transfer function of each channel, including the sampling time. These correction filters are then approximated as a linear combination of base filters and new accurate models with a limited number of free parameters are proposed. Calibration is performed using the recursive least squares algorithm to estimate the coefficients of the linear combination (and the offset term). The resulting algorithms are tested for accuracy, convergence speed, and stability in a fixed-point implementation, and are compared with previously published linear background calibration techniques. The proposed filter bank significantly improves the accuracy/complexity tradeoff with respect to previously published techniques.

Planar Multifrequency Wideband Bandpass Filters With Constant and Frequency Mappings

Abstract: A new planar filter design technique with constant and frequency mappings has been proposed for multifrequency wideband bandpass filters (BPFs). The constant mapping treats components in the $LC$ circuit (e.g., frequency invariant admittances, capacitors, and ideal inverters) as frequency dependent. It is consistent with practical planar circuits and caters to a wide frequency range. Following the classic single-to-multiband transformation, a new frequency mapping function is proposed by incorporating this constant mapping idea. With these two mapping functions, a direct relation between the $LC$ circuit and its microstrip counterpart is established. Therefore, the multifrequency wideband BPF is readily designed from a lowpassing $LC$ circuit to the transmission line circuit. A ladder-type Chebyshev filter and a trisection filter with the general Chebyshev response have been designed as examples. The first one is a dual-band case exhibiting a wide bandwidth for each passband. The second filter is a triple-band one showing a large frequency ratio between the first and third passband. Both examples experimentally validate the proposed constant and frequency mapping technique.

Spectrum Efficient MIMO-FBMC System Using Filter Output Truncation

Abstract: Due to the use of an appropriately designed pulse shaping prototype filter, filter bank multicarrier (FBMC) system can achieve low out of band (OoB) emissions and is also robust to the channel and synchronization errors. However, it comes at a cost of long filter tails, which may reduce the spectral efficiency significantly when the block size is small. Filter output truncation (FOT) can reduce the overhead by discarding the filter tails but may also significantly destroy the orthogonality of FBMC system, by introducing intercarrier interference (ICI) and intersymbol interference (ISI) terms in the received signal. As a result, the signal-to-interference ratio (SIR) is degraded. In addition, the presence of intrinsic interference terms in FBMC also proves to be an obstacle in combining multiple-input multiple-output (MIMO) with FBMC. In this paper, we present a theoretical analysis on the effect of FOT in an MIMO-FBMC system. First, we derive the matrix model of MIMO-FBMC system, which is subsequently used to analyze the impact of finite filter length and FOT on the system performance. The analysis reveals that FOT can avoid the overhead in the time domain but also introduces extra interference in the received symbols. To combat the interference terms, we then propose a compensation algorithm that considers odd and even overlapping factors as two separate cases, where the signals are interfered by the truncation in different ways. The general form of the compensation algorithm can compensate all the symbols in a MIMO-FBMC block and can improve the SIR values of each symbol for better detection at the receiver. It is also shown that the proposed algorithm requires no overhead and can still achieve a comparable bit error rate (BER) performance to the case with no filter truncation.

Dimensional Synthesis of Evanescent-Mode Ridge Waveguide Bandpass Filters

Abstract: This paper introduces a method giving dimensions of inline evanescent-mode ridge waveguide bandpass filters. Evanescent mode couplings are evaluated individually, without optimization of the entire filter. This is obtained through an improved network model of the evanescent-mode coupling, together with novel analytical formulas to correct the resonators slope parameters. Unlike prior works based on full-wave optimization of the overall structure, this method is fast and leads to accurate bandwidth results. Several filter examples are included to support the design method. A prototype filter has been manufactured and the RF measurements are in good agreement with theory.

Design of S-band combline coaxial cavity bandpass filter

Abstract: This paper presents the design of high power, low loss combline coaxial cavity bandpass filter. The design is based on Chebyshev prototype element values for lowpass filters, which are used in calculating the normalized capacitances per unit length between adjacent resonators and resonator to ground. The resonator diameter depends on the capacitance between resonator and the ground, while its length is set equal to λ 0 /8, where λ 0 is the free space wavelength at center frequency f 0 . Similarly the spacing between resonators is calculated using the capacitances between adjacent resonators. In order to tune the filter fo and bandwidth, the tuning and coupling screws are added in the design. The diameter of screws is computed using coaxial capacitance formulations. Once the theoretical calculations are completed, the filter is optimized using 3-D EM simulator to finalize its dimensions. A 5th-order prototype filter at 2.8 GHz with 9% FBW (fractional bandwidth) and 0.01 dB passband ripple is designed, optimized and fabricated for verification. A good agreement between the measured and simulated results validates the proposed synthesis technique.

Compact Microstrip IF Lossy Filter With Ultra-Wide Stopband

Abstract: A novel compact six-pole intermediate frequency lossy filter based on double-layer microstrip coupled microstrip resonators is proposed in this paper. A detailed theoretical analysis for the performance operation mechanism is illustrated. Significant advantages of the proposed structure over existing lossy filters include its low passband insertion loss variation, compact footprint, and ultra-wide stopband bandwidth. Excellent experimental results are provided to confirm these improvements, by using LCP bonded PCB multilayer technology. In general, the fabricated prototype filter operates at 0.97 GHz, with 0.19-dB insertion loss variation in the passband. In addition, it obtains a sharp selectivity with a pair of transmission zeros, as well as the 10th harmonic suppression with better than the 32-dB rejection level. Good agreement between the measured and simulated results can be observed finally.

Optimal filter design for GFDM that minimizes PAPR under performance constraints

Abstract: Generalized frequency division multiplexing (GFDM) is a promising candidate of the fifth generation of wireless communication systems. Though featuring low out-of-band (OOB) radiation and relaxed requirements of time and frequency synchronization, GFDM may suffer from high peak-to-average power ratio (PAPR), which degrades the performance of data transmission. To tackle the PAPR problem, we propose a novel prototype filter optimization algorithm for GFDM with the PAPR minimization toward GFDM data blocks and the characterization of GFDM systems, while maintaining the performance of OOB radiation and symbol error rate (SER). Simulation results show that the optimal filter can best strike a balance among PAPR, OOB radiation and SER, compared to orthogonal frequency division multiplexing (OFDM) systems and several prototype filters existing in the literature. The results also reveal a trade-off between the PAPR and OOB radiation.

Unified Low Complexity Radix-2 Architectures for Time and Frequency-Domain GFDM Modem

Abstract: Most of the conventional multicarrier waveforms explicitly or implicitly involve a generalized frequency division multiplexing (GFDM)-based modem as a core part of the baseband processing. Some are based on GFDM with a single prototype filter, e.g. orthogonal frequency division multiplexing (OFDM) and others employ multiple filters such as filter bank multicarrier (FBMC). Moreover, the GFDM degrees of freedom combined with multiple prototype filters design allow the development and optimization of new waveforms. Nevertheless, GFDM has been widely considered as a complex modulation because of the requirements of odd number of subcarriers or subsymbols. Accordingly, the current state of the art implementations consume high resources. One solution to reduce the complexity is utilizing radix-2 parameters. Due to the advancement in GFDM filter design, the constraint of using odd parameters has been overcome and radix-2 realization is now possible. In this paper, we propose a unified low complexity architecture that can be reconfigured to provide both time-domain and frequency-domain modulation/demodulation. The design consists of several radix-2 fast Fourier transform (FFT) and memory blocks, in addition to one complex multiplier. Moreover, we provide a unified architecture for the state of the art implementations, which is designed based on direct computation of circular convolution using parallel multiplier chains. As we demonstrate in this work, the FFT-based architecture is computationally more efficient, provides more flexibility, significantly reduces the resource consumption, and achieves similar latency for larger block size.

Integrated inductors, capacitors, and damping in bus bars for dv/dt filter applications

Abstract: A dv/dt filter is useful to mitigate the deleterious effects of voltage pulses with high edge rates, such as voltage overshoot in motor drive systems, which can cause premature motor failure. With the introduction of wide-bandgap semiconductor drives, these issues will become more pronounced. This paper introduces a new type of dv/dt filter where the inductor, capacitor, and damping resistor are integrated into the output bus bar or cable of the inverter. This integrated filter may be smaller, lighter, and cheaper to construct than filters built from discrete components. An analytical model of the integrated dv/dt filter is developed, and this model is used to design output filters for a 460 V AC, 3-phase silicon carbide motor drive that meet the NEMA MG 1 Part 31 requirements for inverter-rated motors. Prototype filters are constructed and tested with a silicon carbide inverter connected to a 460 Vrms induction motor, and experimental results demonstrate output waveforms that match the analytical model and meet the NEMA requirements.

State-space formulation of 2-D frequency transformation in Fornasini–Marchesini second model

Abstract: This paper presents a state-space formulation for the two-dimensional (2-D) frequency transformation in the Fornasini–Marchesini second (FM II) model. Specifically, by introducing some new state vectors, an equivalent description of the FM II model will be first established. Then based on this new description, a state-space formulation of the 2-D frequency transformation in the FM II model is derived by revealing the substantial input and output relations among the state vectors of the prototype filter, all-pass filters and the transformed filter. The resultant formulation owns an elegant and general expression, and can be viewed as a natural extension of its counterpart in the Roesser model. Furthermore, as one of the various possible applications of the proposed formulation, a 2-D zero-phase IIR filters design procedure will be shown, by which the desired 2-D zero-phase IIR filters can be constructed in a more flexible way to avoid the kind of image distortions caused by the nonlinear phase of the used filter. Three typical image processing examples as well as the computational complexity analysis will be given to show the effectiveness and efficiency of the proposed procedure.

3D-Printed Low-Pass Filter with Conical Inductors for Broadband RF Applications

Abstract: In this paper we present the preliminary electromagnetic characterization of a 3D-printed low-pass filter for broadband RF applications. The filter consists of two conical 3D inductors and a 3D capacitor, arranged in a third-order Butterworth topology. We designed, fabricated, and tested the prototype filter. The results for insertion loss, cut-off frequency, and bandwidth enhancement, are presented, discussed and correlated with the design and production parameters.

Design of Least-Squares and Minimax Composite Filters

Abstract: We study a class of composite FIR filters (C-filters), each is composed of a prototype filter and a shaping filter in cascade, where the shaping filter is constructed by cascading several complementary comb filters. In particular, the problems of designing C-filters that are optimal in least-squares, equiripple passband and lease-squares stopband, and minimax sense are formulated, and three algorithms for designing such linear-phase FIR C-filters are proposed. The algorithms are based on an alternating optimization strategy in that the prototype and shaping filters are optimized in separate steps, which are coupled and carried out in a sequential manner to yield a satisfactory design. Design examples are presented to illustrate the algorithms and demonstrate the performance of the C-filters relative to their conventional FIR counterparts.

Learning Prototype Spatial Filters for Subject-Independent SSVEP-Based Brain-Computer Interface

Abstract: Data-driven classification approaches have substantially boosted the classification performance in steady-state visual evoked potentials (SSVEP)-based brain-computer interface (BCI). However, as a tradeoff to classification accuracy, a long calibration session is required to collect training data, which greatly reduces the applicability of BCI. In order to minimize the calibration effort while retaining good performance, this paper considers the problem of transferring knowledge from historical subjects to new subject, i.e., subject-independent SSVEP-based BCI. To tackle the problem, we propose a novel way to learn the transferable spatial filters by estimating the invariant task-related spatial filter subspace. The bases of the invariant subspace, which we call prototype spatial filters, are robust estimation of the task-related spatial filters. They can be generalized to the unseen subject for better recovering the latent signals. A new classification approach based on the prototype filters, namely transfer template and filter canonical correlation analysis (ttf-CCA), is then proposed and compared with the state-of-art approaches on the SSVEP benchmark data set. The feasibility of the proposed method is validated by the significant improvement on the classification accuracy and information transfer rate (ITR).

FBMC Prototype Filter Design via Convex Optimization

Abstract: In this work, we propose a prototype filter design for Filter Bank MultiCarrier (FBMC) systems based on convex optimization, aiming superior spectrum features while maintaining a high symbol reconstruction quality. Initially, the proposed design is written as a non-convex Quadratically Constrained Quadratic Programming (QCQP), which is relaxed into a convex QCQP guided by a line search. Through the resulting problem, we design three prototype filters: Type-I, II and III. In particular, the Type-II filter shows a slightly better performance than the classical Mirabasi-Martin design, while Type-I and III filters offer a much more contained spectrum than most of the prototype filters suitable for FBMC applications. Furthermore, numerical results corroborate the effectiveness of the designed filters as the proposed filters offer fast decay and contained spectrum while not jeopardizing symbol reconstruction in practice.

Filter bank based multicarrier systems for future wireless networks.

Abstract: Filter bank based multicarrier (FBMC) systems are one of the promising waveform candidates to satisfy the requirements of future wireless networks. FBMC employs prototype filters with lower side lobe and faster spectral decay, which enables it to have the advantages of reduced out-of-band energy and theoretically higher spectral efficiency (SE) compared to conventional multicarrier scheme i.e., orthogonal frequency division multiplexing (OFDM). These systems also have the ability to facilitate aggregation of non-adjacent bands to acquire higher bandwidths for data transmission. They also support asynchronous transmissions to reduce signaling overhead to meet the ever increasing demand of high data rate transmission in future wireless networks. In this work, the primary research objective is to address some of the critical challenges in FBMC systems to make it viable for practical applications. To this end, the following contributions are provided in this thesis. First of all, despite numerous advantages, FBMC systems suffers from long filter tails which may reduce the SE of the system. Filter output truncation (FOT) can reduce this overhead by discarding the filter tails but may also destroy the orthogonality in FBMC system. As a result, the signal to interference ratio (SIR) can be significantly degraded. To address this problem, we first presented a theoretical analysis on the effect of FOT in a multiple input multiple output (MIMO) FBMC system, when assuming that transmitter and receiver have the same number of antennas. We derive the matrix model of MIMO-FBMC system which is subsequently used to analyze the impact of finite filter length and FOT on the system performance. The analysis reveals that FOT can avoid the overhead in time domain but also introduces extra interference in the received symbols. To combat the interference terms, we then propose a compensation algorithm that considers odd and even overlapping factors as two separate cases, where the signals are interfered by the truncation in different ways. A general form of the compensation algorithm is then proposed to compensate all the symbols in a MIMO-FBMC block to improve the SIR values of each symbol for better detection at the receiver. Secondly, transmission of quadrature modulated symbols using FBMC systems has been an issue due to the self-interference between the transmitted symbols both in the time and frequency domain (so-called intrinsic interference). To address this issue, we propose a novel low complexity interference-free FBMC system with QAM modulation (FBMC/QAM) using filter deconvolution. The proposed method is based on inversion of the prototype filters which completely removes the intrinsic interference at the receiver and allows the use of quadrature modulated signaling. The interference terms in FBMC/QAM with and without the proposed system are analyzed and compared in terms of mean square error (MSE). It is shown with theoretical and simulation results that the proposed method cancels the intrinsic interference and improves the output signal to interference plus noise ratio (SINR) at the expense of slight enhancement of residual interferences caused by multipath channel. The complexity of the proposed system is also analyzed along with performance evaluation in an asynchronous multi-service scenario. It is shown that the proposed FBMC/QAM system with filter deconvolution outperforms the conventional OFDM system. Finally, subcarrier index modulation (SIM) a.k.a., index modulation (IM) has recently emerged as a promising concept for spectrum and energy-efficient next generation wireless communications systems due to the excellent trade-offs they offer among error performance, complexity, and SE. Although IM is well studied for OFDM, FBMC with index modulation (FBMC-IM) has not been thoroughly investigated. To address this topic, we shed light on the potential and implementation of IM technique for FBMC system. We first derived a mathematical matrix model of FBMC-IM system (FBMC/QAM-IM) along with the derivation of interference terms at the receiver due to channel distortions and the intrinsic behavior of the transceiver model. We have analytically shown that the interference power in FBMC/QAM-IM is smaller compared to that of conventional FBMC/QAM system as some subcarriers are inactive in FBMC/QAM-IM system. We then evaluated the performance of FBMC/QAM-IM in term of MSE, SIR and output SINR. The results show that combining IM with FBMC/QAM can improve the system performance since the inactive subcarriers are not contributing to the overall interference in the system. Based on the interference analysis, we then proposed an improved log-likelihood ratio (LLR) detection scheme for FBMC/QAM-IM system. At the end, BER performance of FBMC/QAM system with and without IM is presented and it can be seen that since the power from inactive subcarriers is reallocated to the active subcarriers in FBMC/QAM-IM, the system shows improved performance compared to conventional FBMC/QAM system.

Direct Metal Printed 4th order Stepped Impedance Filter in the C/X Band

Abstract: In recent years, additive manufacturing (AM) techniques were increasingly applied to develop RF and microwave components. The main advantage of AM is a reduction in both mass and production time. The AM technique investigated in this paper is direct metal printing (DMP). As a consequence, challenging geometries can be implemented. Here we present a 4th order cavity filter, realized by cascading four lollypop-shaped resonators. The filter was designed to be manufactured in one block using stainless steel as a base material, however, for reasons of workpiece accessibility the two halves and the closing plates of the first prototype were produced separately and subsequently fixed together. Tuning screws were used to adjust the performance. The prototype filter exhibits a measured insertion loss of 1.14 dB with the matching being better than −12.77 dB, a fractional bandwidth of about 3.6 % at 7.926 GHz, and a Q-factor of 1600.