Transmission Zeros Research Articles

Design and implementation of a multibeam filtering antenna array using compact 3 × 3 Nolen matrix aided by grey wolf algorithm

This paper presents a novel multibeam filtering antenna array based on a compact 3 × 3 Nolen matrix integrated with HRR filters for solar observations. The design facilitates the simultaneous recording of solar radio flux density and sky background flux density, streamlining calibration processes. The use of stub-loaded transmission line (SLTL) couplers achieves a significant 43.4% reduction in the size of the Nolen matrix, enhancing compactness. The hairpin ring resonator (HRR) filter with two transmission zeros (TZs) is employed to ensure electromagnetic compatibility (EMC). Given the limitations of conventional manual design methods, the intelligent grey wolf algorithm (GWA) is adopted to optimize the physical parameters of the Nolen matrix layout, realizing rapid and accurate achievement of the desired performance. The −6.2±0.15 dB transmission coefficient and 0°, −120°and +120°of output phase differences within 2° phase error are accomplished at 2.8 GHz. Finally, the proposed multibeam filtering antenna array is fabricated and measured to confirm its ability to generate the required three beams with filtering characteristics. The measured results have a good agreement with the simulated results.

Air-filled substrate integrated waveguide bandpass filter based on miniaturized non-resonant node structure

Abstract This paper proposes an air-filled substrate integrated waveguide (AFSIW) bandpass filter with a miniaturized non-resonant node (NRN). The NRN structure is introduced between the three resonators, and its size is smaller than the resonator size, which can realize the NRN structure’s miniaturization and reduce the model’s size. The NRN size of this filter is 41% of the NRN size of the existing AFSIW filter. This filter also introduces a transmission zero (TZ) above the passband. The measured results show that the filter’s center frequency is 20.73 GHz, and the bandwidth is 0.86 GHz. The insertion loss in the passband is 0.95 dB, and the return loss is better than 23 dB. Due to the TZ in the upper stopband, the AFSIW filter obtained good selectivity.

A simple miniaturized sub‐6‐GHz bandpass filter with wide upper stopband in gallium arsenide‐based integrated passive device process

AbstractA very compact three‐pole bandpass filter with wide upper stopband is proposed and implemented by gallium arsenide integrated passive device technology. By organizing inductor and capacitor in parallel with an LC series network, a dual‐frequency bandstop structure is constructed in the first step to achieve transmission zeros (TZs). Then, the lowpass capacitor network and highpass inductor network are wisely cascaded with the bandstop structure, thus to the realization of three‐pole bandpass filter with a wide upper stopband. Based on the even‐/odd‐mode analysis, theoretical equations for the in‐band resonances and out‐of‐band TZs are given. Then, one filter prototype centered at 4.4 GHz with 3‐dB fractional bandwidth of 45.5% is designed, fabricated, and measured. Both simulated and measured results indicate that the proposed filter exhibits a wide stopband rejection of 25 dB from 6.4 to 22.8 GHz as well as a very compact size about 0.026λg × 0.031λg.

Compact IPD bandpass filter with wide upper stopband based on modified topology for 5G applications

AbstractA compact bandpass filter (BPF) with wide stopband performance is proposed and implemented on Si‐based integrated passive device (IPD) technology. A modified topology consisting of a novel Pi‐section and two capacitors are introduced in this BPF. The Pi‐section topology can achieve a band‐pass performance and generate four transmission zeros out‐of‐band. These two capacitors can improve the in‐band matching and also widen the stopband. The proposed BPF with a compact size of 1.0 mm × 0.5 mm × 0.3 mm is fabricated using Si IPD technology and measured by on‐wafer probing. It shows that the insertion loss is less than 1.75 dB, the return loss is better than 18 dB in the 5G band, and the upper stopband suppression level is better than 17.5 dB up to 18 GHz. The simulated and measured results of the proposed BPF are in reasonably good agreement.

Dual‐band bandpass‐filtering high‐efficiency power amplifier with second harmonic suppression

AbstractThis study proposes a dual‐band bandpass‐filtering high‐efficiency power amplifier based on dual‐function dual‐band impedance control network (DBICN) and a dual‐band bandpass‐filtering impedance transformer (DBBFIT). The dual‐function DBICN is exploited to transform the optimal fundamental complex load impedance to real one, and control the second harmonic load impedances of two bands to the high‐efficiency region in the Smith chart. Besides, two transmission zeros are constructed at dual‐band second harmonics to enhance harmonic suppression. Meanwhile, an easy‐to‐design DBBFIT is proposed by utilizing filter theory to realize real‐to‐real impedance transformation, and all design parameters can be obtained by simple closed‐form analytical equations. For validation, a prototype is designed, fabricated, and measured. The measured results indicate the drain efficiencies are 61.6% and 58.3% at 1.78 and 2.42 GHz with saturation output power of 40.8 and 39.6 dBm, respectively. Moreover, the second harmonic suppressions of the two bands are 40.1 and 47.1 dBc, respectively.

Ultracompact Bandpass Filter With Multiple Transmission Zeros and Low Insertion Loss

Ultracompact Bandpass Filter With Multiple Transmission Zeros and Low Insertion Loss

3-D printed triple-band metasurface filter based on groove gap waveguide technology

This article proposes a 3-D printed high selectivity triple-band metasurface bandpass filter (BPF) for millimeter-wave applications using groove gap waveguide (GGW) technology. Firstly, the metasurface composed of electromagnetic bandgap elements in GGW technology is designed and analyzed. This configuration effectively mitigates radiation and electromagnetic wave leakage. Subsequently, the multimode split-type topology under the resonances of TE102 and TE201 modes is utilized to realize a triple-band bandpass response with a compact circuit size. Additionally, the TE101 mode considered as an extra energy coupling path is used to introduce more transmission zeros (TZs). Finally, the design prototype is fabricated using 3D printing technology. The measured results are in good agreement with the simulated ones, providing an excellent option for mm-wave wireless communication systems.

A Modified High-Selective Frequency Selective Surface Designed by Multilevel Green’s Function Interpolation Method

A compact high-selective band-pass frequency selective surface (FSS) with the unit cell less than λ/7 is presented. For the simulation of the structure, the multilevel Green’s function interpolation method (MLGFIM) using Floquet theory is adopted to accelerate the calculation of the complex unit cell. The radial basis function (RBF)-QR method is used in the interpolation, which makes the shape parameter in the RBF function not required to be retested for different periodicity. In this design, with an aperture coupling structure between the top and bottom layers patterned by triangular patches and meander lines, the FSS has two transmission zeros (TZs) on both sides of the pass-band and achieves a steep roll-off rate of 192 dB/GHz. Consequently, the FSS has high selectivity and out-of-band suppression, besides profiting from the low profile and symmetric geometry, this FSS exhibits good angular and polarization stabilities. The prototype of the proposed FSS is fabricated and good performance is obtained.

A Wideband Circularly Polarized Dipole Antenna with Compact Size and Low-Pass Filtering Response.

This paper presents a compact wideband circularly polarized cross-dipole antenna with a low-pass filter response. It consists of two pairs of folded cross-dipole arms printed separately on both sides of the top substrate, and the two dipole arms on the same surface are connected by an annular phase-shifting delay line to generate circular polarization. A bent metal square ring and four small metal square rings around the cross-dipoles are employed to introduce new resonant frequencies, effectively extending the impedance and axial-ratio bandwidth. Four square patches printed on the middle substrate are connected to the ground plane by the vertical metal plates in order to reduce the antenna height. Thus, a compact wideband circularly polarized antenna is realized. In addition, a transmission zero can be introduced at the upper frequency stopband by the bent metal square rings, without using extra filter circuits. For verification, the proposed model is implemented and tested. The overall size of the model is 90mm×90mm×33mm (0.37λ0×0.37λ0×0.14λ0; λ0 denotes the center operating frequency). The measured impedance bandwidth and 3 dB axial-ratio (AR) bandwidth are 53.3% and 41%, respectively. An upper-band radiation suppression level greater than 15 dB is realized, indicating a good low-pass filter response.

Miniaturized independent controllable dual-band bandpass filter by using transversal signal interference concepts

Abstract This paper presents and validates a compact dual-band bandpass filter with independent controllable passbands and isolation. The proposed filter is constructed by two transmission paths from input port to output port. Based on the transversal cancellation mechanism of two transmission paths, dual passband with independent controllable characteristics can be approached. The transversal cancellation techniques yield extra transmission zeros, which are located at 2.56 GHz, 3.58 GHz and 4.43 GHz respectively. Therefore, two passbands centered at 2.25/3.9 GHz are divided by triple transmission zeros. These transmission zeros also improve the out-of-band suppression performance of proposed filter. The designed prototype filter is implemented and tested, the measured 3 dB passband fractional bandwidths are 12.4 % and 7.5 %, respectively, and the minimum insertion losses are 0.48 dB and 0.88 dB respectively. Additionally, the dual-band transversal filter only occupies 0.012 λ g 2 ${\lambda }_{g}^{2}$ , which λ g is the guided wavelength at 50 Ω microstrip line at 2.25 GHz.

The co-design of IPD high-selectivity diplexer and dual-band filter chips based on lumped element single-band filter

In this paper, a dual-band bandpass filter (D-BPF) and a diplexer are proposed. Their core structures are both a lumped element single-band bandpass filter (S-BPF) with dual transmission poles (TPs) and dual transmission zeros (TZs). For the D-BPF, based on this S-BPF, single-band impedance matching networks (S-IMNs) are used to form the second/third passbands. Two S-BPFs with different first reactance elements are used for the diplexer to achieve good isolation without T-junction. Finally, the D-BPF and the diplexer with center frequencies of 2.26/4.75 GHz and 2.3/5.75 GHz are fabricated by thin-film integrated passive device (IPD) technology. The physical size of the D-BPF chip is only 1.5 × 1.1 mm2, and the diplexer chip is 2.3 × 1.5 mm2. Measured results show they both have the advantages of good insertion loss, excellent impedance matching, high roll-off, and broad stopband rejection. The isolation of the diplexer is greater than 23 dB from 0 to 10 GHz.

Compact High-Performance Balanced Wideband BPF With a Notch Band and Multiple Transmission Zeros

Compact High-Performance Balanced Wideband BPF With a Notch Band and Multiple Transmission Zeros

Wideband Absorptive Bandpass Filter With Multiple Transmission Zeros and Flat Group Delay

Wideband Absorptive Bandpass Filter With Multiple Transmission Zeros and Flat Group Delay

Lumped-Distributed Resonators Providing N or 2N Transmission Zeros at Real Frequencies in Bandpass Filters Without Cross and Mixed Couplings

Lumped-Distributed Resonators Providing N or 2N Transmission Zeros at Real Frequencies in Bandpass Filters Without Cross and Mixed Couplings

A broadband second-order bandpass frequency selective surface for microwave and millimeter wave application.

This paper presents a frequency selective surface (FSS) with a wideband second-order bandpass response in the dual-band of microwave and millimeter wave. The overall structure consists of three layers of metal pattern and two layers of thin dielectric substrate. The top and bottom metal layers have capacitive patches with integrated curled Jerusalem cross slot resonators, while the intermediate metal layer has an inductive grid structure with cross-shaped slot resonators. The incorporated slot resonators play a pivotal role in achieving the desired transmission poles or zeros, which enable a wideband second-order filtering response in the dual-band and a quick roll-off at the passband edges, increasing the efficacy of electromagnetic shielding. To fully investigate the structure's frequency response, an equivalent circuit model of the structure is created, spanning the complete frequency range of 5-50 GHz. Physical samples are created and measured to confirm the suggested approach's efficacy. The passband center frequencies of the FSS are found at f1 = 19.42 GHz and f2 = 42.78 GHz, and the - 3dB bandwidth is 4.34 GHz (17.25-21.59 GHz) and 8.54 GHz (38.51-47.05 GHz), respectively. The simulation results align well with the experimental data. The transmission response rapidly transitions from the passband to the stopband at the passband boundaries.

Compact high attenuation wide rejection bandwidth 5-pole Butterworth LPF using transmission zeros in GaAs process

In this work, a systematic design method for a compact 5-pole Butterworth transverse resonance low pass filter (TR-LPF), in 0.15 μm Gallium Arsenide process, with wide rejection bandwidth (RBW), is presented. The circuit model of TR-LPF and closed-form expressions are provided to appreciate the design process. The fabricated TR-LPF has a cut-off frequency of 10.5 GHz, an insertion loss of 0.4 dB, and the return loss is better than 20 dB. The 20 dB, 30 dB, and 40 dB deep rejection bandwidths (RBWs), across 50 GHz, 45.5 GHz, and 17 GHz respectively, are obtained. The novel use of stubs and spur resonators, within stubs; provides the deep and wide RBW. The compactness of the TR-LPF is realized by the ‘C’-and ‘Z’-shaped folding of stubs. The dimension of the filter is approximately 0.11λg×0.079λg.

Design of Hybrid Bandpass Filter Chips with High Selectivity and Wideband Using IPD and FBAR Technology

A novel hybrid bandpass filter (BPF) with wideband and high selectivity is proposed in this paper. The hybrid BPF is composed of two film bulk acoustic resonator (FBAR) cells and three lumped component resonators realized by the integrated passive device (IPD) technology. The ABCD matrix to S-parameters matrix method is used to calculate the frequency response of the BPF. Moreover, the expressions of transmission zeros (TZs) have been extracted. In the design process, an iterative design approach is proposed to improve the circuit and layout of the hybrid filter based on the packaged acoustic-electric hybrid simulation effect. Finally, two parts of the filter are packaged based on the flip-chip method, and two prototypes for the BPF are measured. The measured results of two chips with 3 dB fractional bandwidth of 13.7% and 15.8% are designed and fabricated, which verifies the validity of the proposed design principle.

A design method for filter to achieve arbitrary distribution of multiple transmission zeros without cross-coupling

This paper proposes a method for introducing transmission zeros (TZs) in filters using dual-mode resonators. By loading a dual-mode resonator as a second-order extracted-pole unit (EPU) at the input or output of the filter, a pair of finite TZs can be introduced without cross-coupling. This approach reduces the size of the filter while generating two finite transmission zeros compared to conventional methods. Since the dual-mode resonator is characterized by its separable odd and even modes, and by adjusting the resonant frequency of the EPU, it can achieve an arbitrary distribution of TZs. It is worth noting that the EPU does not affect the insertion loss of the filter because it operates mainly outside the passband. Furthermore, this work delves into the EPU’s mechanism for generating TZs and the method of adjusting TZ position by designing filters of second, fourth, sixth, and eighth orders, providing a solid foundation for the creation of higher-order filter circuits.

Wideband bandpass filter with ultra-wide stopband based on cross-shaped parallel coupled lines

A broadband out-of-band rejection capability and multiple transmission zeros of wideband bandpass filter are proposed and validated in this article, which employ quadruple anti-parallel coupled-line structures to form a novel cross-shaped resonator planar topology. The centered frequency of the single wideband bandpass filter designed for verification is located at 2.4 GHz (f 0) with a fractional bandwidth of 50%. The interaction of crossed multiple anti-coupled lines with a lowpass-loaded fan constitutes the wideband with nine transmission zeros in the 5 f 0 frequency range for improved suppression extending to 26.5 GHz (10.7 f 0) with a suppression level of 12.5 dB. Moreover, the designed prototype filter is implemented and tested with a measured minimum insertion loss of 0.9 dB. Good agreement between the measured and simulated results is attained to successfully validate the correctness of the proposed design approach.

Design of high selectivity tri-band bandpass filter based on triple transversal transmission path

By utilizing transversal signal interference concepts, a tri-band bandpass filter with a triple transmission path is proposed in this paper. Triple transversal transmission paths are respectively constructed with the employ of parallel coupled stub loaded resonator, microstrip gap coupled line and parallel coupled shorted stub loaded resonator. Based on the triple transversal transmission path, nine transmission poles (TPs) are excited; therefore, triple independently controllable wideband passbands are realized. Due to the transversal cancellation between transmission paths with the virtual short mechanism of each transmission path, seven transmission zeros (TZs) can be excited and managed. Therefore tri-wideband characteristics with high selectivity and high band-to-band isolation can be obtained by properly adjusting the TPs and TZs. To further demonstrate the proposed design methodology, a prototype tri-wideband bandpass filter operating at 1.93/3.52/5.11 GHz with fractional bandwidth of 11.8 %, 19.8 % and 22.8 % for LTE, WiMAX, Wi-Fi and 5G applications is synthesised. The presented tri-wideband bandpass filter is designed, manufactured and measured. The measured results agree well with theoretical predictions, which exhibit superior performance such as sharp shirts, high band-to-band isolation compact size and ideal out-of-band suppression.