An Overview of Generalized Frequency Division Multiplexing (GFDM)

<div>As a candidate waveform for next-generation wireless communications, generalized frequency division multiplexing (GFDM) features several decent properties which make it promising. In this paper, we systematically overview the research about GFDM. We start with GFDM transceivers with their main components, which consist of prototype filter design, low-complexity transceiver implementation, and symbol detection algorithms. Then, we investigate a couple of non-ideal issues of GFDM, including synchronization issues, channel estimation, and in-phase/quadrature (I/Q) imbalance compensation. Lastly, we study the applications of GFDM-based cognitive radio and full-duplex radio which boast of a high spectral efficiency.</div>

An Overview of Generalized Frequency Division Multiplexing (GFDM)

<div>As a candidate waveform for next-generation wireless communications, generalized frequency division multiplexing (GFDM) features several decent properties which make it promising. In this paper, we systematically overview the research about GFDM. We start with GFDM transceivers with their main components, which consist of prototype filter design, low-complexity transceiver implementation, and symbol detection algorithms. Then, we investigate a couple of non-ideal issues of GFDM, including synchronization issues, channel estimation, and in-phase/quadrature (I/Q) imbalance compensation. Lastly, we study the applications of GFDM-based cognitive radio and full-duplex radio which boast of a high spectral efficiency.</div>

Microwave lowpass filter with improved out-of-band performance based on tilted rectangular slots

A compact microwave lowpass filter with sharp selectivity and wide stopband based on tilted rectangular slots is proposed in this paper. The developed prototype filter is based on the log periodic theory, where tilted log-periodic rectangular slots are studied for the first time. Effects resulting from the tilted slots on the performance of the studied filter are discussed and conclusions are drawn. A prototype of the proposed lowpass filter was fabricated and measured. The measured results show that the lowpass filter features a high selectivity and a wide suppression band from 4.05 GHz to 24.91 GHz under a level of 19.2 dB. Both measured and simulated performances are presented with good consistency.

Монолитный миниатюрный полосно-пропускающий фильтр на многопроводниковых полосковых резонаторах

A new monolithic design of a miniature bandpass filter has been developed for the multilayer PCB technology fabrication. The use of multi-conductor stripline resonators in the design provides not only miniaturization, but also high selectivity of the device, which is demonstrated on a prototype filter of the fourth order. The center frequency of the passband of the manufactured filter is f0 = 546 MHz, the fractional bandwidth is Δf / f0 = 25%, the insertion loss is 0.8 dB. The filter has an extended high-frequency stop band, which at a level of ‒30 dB extends up to a frequency of 10f0. The dimensions of the filter are 15.0×12.0×4.3 mm3 (0.027λ0×0.021λ0 ×0.007λ0, where λ0 is the wavelength in vacuum at the frequency f0), and its mass is only 1.8 g. The filter's characteristics and ease of construction for surface mounting prove its high prospects.

Design of microwave lowpass filter based on log periodic zigzag DGS

This contribution presents, for the first time, the design of microwave lowpass filter with ultrawide stopband and low insertion loss based on the log-periodic zig-zag defected ground structure (DGS); the design is specifically evolved from the principle of the log-periodic line antenna and the slotline based DGS. Based on the log-periodic property, studies show that ultra-wideband suppression can be realized by increasing the flare angle or the angle subtended by each element of the slotline DGS. The developed filter therefore shows low insertion loss of 0.7 dB within the passband, sharp transition between the passband and the stopband and ultra-wide suppression band from 2.61-26.5 GHz with a 20 dB suppression level. The DGS architecture is simple and easy to realize, and the design is thus useful in many microwave applications. The fabricated prototype filter validates the study, both from simulations and from measurements.

The role of filter media geometry in tap water biofilms

&lt;p class=&quot;MDPI17abstract&quot;&gt;&lt;span lang=&quot;EN-US&quot;&gt;Biofilms are inextricably linked to the hydrodynamics of flow through a filter and yet engineers rarely explicitly engineer this interaction. We developed a system that links computer simulation and 3-D printing to optimize filter media geometry and biofilm function. The main objective is to prototype filter media to passively induce vortices that roll down a surface, imposing oscillating flow in the channel to enhance biofilm formation. Thus, a 2-D model was developed and linked to a 3-D printer. The model was solved to determine the wall shear stress distribution with time. The experiments showed that the thickest, densest and most extended biofilms were formed for the strongest oscillations in the channel due to the presence of a filter medium. This is a speeding-up innovation in the design and implementation of small-scale biofiltration systems for rural communities.&lt;/span&gt;&lt;/p&gt;