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This paper proposes a new type of hybrid eighth‐mode substrate integrated waveguide (EMSIW) and microstrip line (MSL) bandpass filter (BPF) with mixed electric and magnetic coupling. Firstly, two second‐order EMSIW BPFs with mixed coupling and wide stopband performance are investigated. Then, in order to realise high‐order BPF with decent performance, half‐wavelength (λ/2) open‐circuited MSL resonators are employed in the hybrid BPFs design. In the end, two third‐order BPFs and a fourth‐order BPF are developed by combining the EMSIW and MSL resonators together. Extra transmission zeros can be introduced due to the cross couplings in the trisection and quadruplet topologies. For demonstration, the proposed prototypes are designed, fabricated and measured. Reasonable agreements can be achieved between the measurement and simulation. The proposed third‐order BPFs compete against the state of the art, exhibiting the competitive characteristics of the operating bandwidth, physical footprint and upper‐stopband rejection with less order. The proposed fourth‐order BPF features a compact size of 0.34 × 0.34λ0, a low insertion loss of 1 dB, a broad 3‐dB fractional bandwidth of 22.9% and an excellent lower‐stopband suppression. [ABSTRACT FROM AUTHOR]

This paper proposes three balanced multiple‐layer dual‐mode substrate integrated waveguide (SIW) bandpass filters. The first balanced filter has two substrate layers, and two pairs of balanced feeding ports are located on the upper substrate layer. The lower and upper dual‐mode SIW cavities are coupled by two crossed slots in the middle metal layer. The second balanced filter has two substrate layers, and two pairs of balanced feeding ports locate parallelly on the upper and lower substrate layers, respectively. The third balanced filter has three substrate layers, and two pairs of balanced feeding ports locate vertically on the upper and lower substrate layers, respectively. The proposed three balanced filters can produce three, two and one finite‐transmission zeros (FTZs), respectively. Characteristics of the proposed multiple‐layer SIW filters with controllable FTZs' locations are analysed in detail. For the demonstration, some design examples with the centre frequency of 7.5 GHz and bandwidth of 240 MHz are presented, and three design examples are fabricated to verify the performance of the proposed balanced filters. The measured results agree well with simulated ones. [ABSTRACT FROM AUTHOR]

Cross‐coupled microwave filter with flexible topology is an essential component in a modern communication system. Among the various filter networks, the use of an extended box section can effectively reduce the difficulty of filter design, but the synthesis approach for this popular structure is not well developed. This paper presents the synthesis method based on the folded coupling matrix to derive the extended box sections. At the same time, an eighth‐degree filter with extended sixth‐degree box sections is synthesized to demonstrate the correctness of the approach. Finally, the new approach's feature to derive advanced circuits such as peculiar quintets is discussed, indicating that it has certain universality. [ABSTRACT FROM AUTHOR]

This paper proposes a new time‐resolved spectral analysis method based on a modification to the linear predictive coding (LPC) method for enhancing the identification of the dominant frequencies of a signal. The method described here is based on a z‐plane analysis of the LPC poles. These poles are used to produce a series of reduced order filter transfer functions which can accurately identify and estimate the frequency of the dominant spectral features. The standard LPC method has been shown to suffer from a sensitivity to noise and its performance is dependent on the filter order. The proposed method can accurately identify the dominant frequency components over a range of filter orders and is shown to be robust in the presence of noise. Compared with traditional time‐resolved methods, it is a parameterised method where the identification of the dominant frequency changes can be directly obtained in the form of frequency measurements. In a series of 10,000 Monte Carlo experiments on single component and multiple component signals, this LPC pole processing method outperforms the standard LPC method by accurately identifying the dominant frequency components in the signals. [ABSTRACT FROM AUTHOR]

Filters are inevitable for grid‐connected inverters to attenuate the current harmonics caused by the pulse width modulation which is usually used in power conversion systems. High‐order filters have attracted much attention because they attenuate the current harmonics effectively. Nevertheless, the high‐order filters have some resonances which cause instability of the system. In addition, the resonance frequencies shift to high as the inductors and capacitors are smaller. It implies that the resonance frequencies may be beyond the Nyquist frequency in downsizing the filter. This complicates the stability and performance analyses of the system. This paper investigates rigorous input–output stability and analyses a robust performance based on the sampled‐data control theory regardless of whether the resonance frequencies are beyond the Nyquist frequency or not. Our analysis contributes to downsizing the filter synthesis while the stability and the robustness are guaranteed even if the resonance frequencies are beyond the Nyquist frequency. The effectiveness of the proposed method is verified through simulations and experiments. [ABSTRACT FROM AUTHOR]

Here, a novel design of absorber loading dual‐layer frequency selective surfaces (FSSs) in the Salisbury screen is proposed. The design of frequency selective surfaces is mainly composed of cross‐dipole and dual‐loop metal patch. Simulation results show that this absorbing structure can achieve ultra‐wideband absorption from C band to K band and the fractional bandwidth reaches 117.1% below –10 dB. The thickness of the proposed absorbing structure is 0.078 λL and the unit cell size is 0.262 λL, where λL is the wavelength of the lowest absorbing frequency. Moreover, it shows excellent polarization stability in TE and TM modes, and it has great angular stability. Finally, the prototype of this structure is fabricated, and the measured results are in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Design procedure of a novel transmission line low‐pass filter is presented. The filter has a flexible rejection response for a prescribed cut‐off frequency and an in‐band ripple factor. It is compact by using a Z‐shaped coupled‐line section, which is loaded with open‐circuited stubs. All of the transmission line elements are identical in electrical length, and the impedances can be calculated by solving certain specific equations according to prescribed in‐band specifications. The simulated results show that the circuit can generate low‐pass responses with third‐, fifth‐, and seventh‐order filtering functions. The filter order depends on the number and position of the loading stubs. For verification, two sample filters with cut‐off frequency of 0.5/0.3 GHz are fabricated using a three‐/five‐layer PCB process, which generate seventh‐order low‐pass filtering responses with good selectivity. The experimental results agree well with the predictions. [ABSTRACT FROM AUTHOR]

A new bandpass filter (BPF) with two switchable operating passbands has been proposed. The BPF topology is formed by switchable resonators and stepped‐impedance resonators. The two operating bands can be switched on and off independently. For verification, a switchable BPF with a third‐order Chebyshev bandpass response was designed and fabricated using microstrip technology. The developed BPF was measured to verify the predicted and simulated results. A close agreement was observed between them. The proposed switchable BPF has good in‐band and out‐of‐band performances. Besides, the attenuation is > 30 dB as the passband is switched off. [ABSTRACT FROM AUTHOR]

A design method of compact wideband balun bandpass filter (BPF) with high selectivity based on corrugated slot is proposed here. To realize wideband balun response in compact size, metal strips are deployed parallel to the half‐mode corrugated slot (HMCS). Besides, the coupling of corrugated slot to the metal stripline provides the conversion of slot to microstrip structure at the balanced ports. By placing a pair of resonators at the balanced ports, a wideband balun BPF response with high selectivity can be realized. In addition, a U‐shaped resonator is also loaded at the end of the corrugated slot to suppress harmonics. Afterwards, a compact wideband balun BPF centred at 2.42 GHz with 3‐dB FBW of 45% is designed, fabricated, and measured. The effective size is 0.13λg × 0.39λg (λg is the guided wavelength of the centre frequency) and the measured results indicate that the magnitude imbalance is less than 0.45 dB and the phase imbalance is less than 4.8° within the operation frequency band. [ABSTRACT FROM AUTHOR]

To reject the disturbances of the nonminimum‐phase systems, the generalised dual‐filter disturbance observer is proposed. The conventional disturbance observer methods inevitably lead to nonminimum‐phase systems' instability. To stabilise the system, the forward plant and dual filters are introduced. The stability constraints are transferred to the dual filters. Based on any stable designs of the close‐loop controller, the dual filters can be easily designed. The simulations effectively verify that the disturbance rejection performances of the proposed method are triple those of the closed‐loop nonminimum‐phase system, and the original system's tracking capabilities and stability margins are few affected. [ABSTRACT FROM AUTHOR]

High‐Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) utilizes the characteristics of nonlinear ion mobility at high electric fields to filter ions. We propose a novel glass‐cell FAIMS olfactory sensor that mimics the olfactory sense of living organisms by applying LCD mass production process technology. This olfactory sensor has a simple configuration consisting of an odor molecule ionization section and a glass‐cell FAIMS sensor, which is a pair of glass substrates with patterned electrodes. The ionized odor molecules pass through the glass‐cell FAIMS sensor, and the filtered ion molecules are detected. We have experimented with different odorous components, including fermented beverages (wine) and animal excrement (cat urine, stool), to create unique "odor fingerprints". [ABSTRACT FROM AUTHOR]