Transmission Zeros Research Articles

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.

A high-selective multiple-mode bandpass filter design, applicating in both millimeter-wave 5G and WiFi systems

This paper proposes a millimeter-wave bandpass filter (BPF) with high selectivity, which can be applied in both 5G and WiFi systems. Two dual-mode resonators (DMRs) are adopted and analyzed coupled microstrip lines (CMLs) and can form six transmission poles (TPs) and four transmission zeros (TZs). Furthermore, a multiple-mode resonator (MMR) is presented based on the DMRs to realize a high selective passband. Additionally, five extra TZs are introduced by two pairs of open-circuited stubs and transversal signal interference (TSI), which are introduced by cross-coupling of two signal paths. These TZs significantly enhance out-of-band suppression performance. The proposed BPF is fabricated in ceramic process, and measurement results demonstrate a minimum insertion loss of −1.52 dB, a 3-dB passband from 38.3 to 48.2 GHz, a 30-dB rectangular coefficient of 1.21, and a 30-dB stopband extending to the test limit of 67 GHz.

Sharp-rejection dual ultra-wideband bandpass filter using sextuple mode resonator

ABSTRACT In this paper, a novel sextuple mode resonator (SMR) is proposed to design a compact ultra-wide dual-band bandpass filter (BPF) with high selectivity. An even- and odd-mode analysis method is employed to analyze the proposed SMR, and the SMR can excite six resonant modes simultaneously. In addition, a cross shape and several open-circuit stubs are used in the proposed SMR for generating multiple transmission zeros (TZs). The TZs can divide the transmission poles into two groups to form the two passbands. With properly tuned the TZs and the transmission poles, the proposed dual-band ultra-wideband BPF is of high selectivity. The center frequencies (CFs) of the BPF are centered at 1.6 GHz and 5.2 GHz, respectively. The 3-dB fractional bandwidths (FBW) of the two passbands are larger than 145% and 25%, respectively. To demonstrate the performance of the proposed method, an ultra-wide dual-band BPF is fabricated. Measurement results show that the proposed BPF has high band-to-band isolation, wide stopband, low insertion losses (ILs), controllable bandwidth, and compact size. The stopband is up to 12.5 fc1 (fc1 is the center frequency of passband 1st), and the circuit size is only 0.1λg × 0.12λg.

Design of IPD-based wideband bandpass filter chips with controllable transmission zeros

ABSTRACT In this brief, two novel wideband bandpass filter (BPF) chips with independently controllable transmission zeros are proposed. BPF I uses bridge T-type highpass and lowpass structures cascaded to achieve wideband filtering. On this basis, BPF II adds three pairs of LC resonant circuits to add additional transmission zeros while retaining the lowpass structures. The analytical methods of odd-even mode and ABCD matrix to S-parameter matrix are used to analyze and calculate two designs. For validation, two prototypes of proposed BPFs in integrated passive device (IPD) have been designed, fabricated, and measured. One prototype operates at 5.3 GHz, providing a 3-dB fractional bandwidth (FBW) of 46.9%, while the other prototype operates at 4.7 GHz, providing a 3-dB FBW of 57.6%. Moreover, the two chips exhibit minimum insertion losses of 1.55 dB and 1.5 dB, respectively, while occupying compact sizes of 2.27 mm × 0.83 mm and 1.7 mm × 0.88 mm.

A broadband diplexer-integrated double-pole single-throw switch for FDD/TDD operations

ABSTRACT A broadband diplexer-integrated double-pole single-throw (DPST) switch is proposed to realize frequency division duplexing (FDD) and time division duplexing (TDD). It consists of a lowpass filter (LPF) and a bandpass filter (BPF). The series LC resonators are used in both channels to create transmission zeros (TZs) in the stopband to ensure high selectivity. The diplexer is realized by inter-digital capacitors and microstrip section inductors, which can achieve low cost and compact size. Besides, this diplexer does not require a T-junction, achieving a compact size. For demonstration, a diplexer operating in DC-1.78/3.29–4.42 GHz has been designed, fabricated, and measured. The diplexer has four operating modes. And it has a compact size of 24.67 mm × 21.4 mm. The measured results show that the diplexer exhibits broadband, low insertion losses, high isolation, and high selectivity.

A super-compact wideband bandpass filter using capacitor-loaded coupled lines

Abstract A wideband bandpass filter (BPF) using capacitor-loaded coupled lines is proposed with super-compact circuit size and very simple structure. By loading three lumped capacitors in parallel to three same pairs of coupled lines, three transmission poles and four transmission zeros can be achieved and they can be calculated by input admittance derivation. To verify the design, a wideband BPF prototype with center frequency at 1.34 GHz is fabricated, whose measured 3-dB fractional bandwidth is 98.5 % (0.68–2 GHz), in-band insertion loss is less than 0.5 dB, return loss is greater than 17.5 dB, and circuit size is only 0.24 λ g × 0.02 λ g (λ g: guided wavelength at the center frequency).

Miniaturized IPD band pass filter with low insertion loss based on modified T‐section for 5G applications

AbstractA miniaturized bandpass filter (BPF) with low insertion loss based on a modified T‐section and a grounded transmission‐zero resonator is proposed. The novel T‐section consists of two resonators, which can achieve the bandpass performance with two transmission zeros (TZs) in the upper band. The grounded transmission‐zero resonator can generate an extra transmission zero in the lower band. Therefore, high frequency selectivity can be achieved by the above three transmission zeros near the passband. The proposed BPF can achieve an insertion loss of 0.8 dB and a return loss of 22 dB covering 3.3–4.2 GHz, and the upper‐stopband attenuation is better than 20 dB up to 12.5 GHz (3.3f0). The proposed BPF with a miniaturized size of 1.2 mm × 0.5 mm × 0.3 mm have been fabricated using Si‐based integrated passive devices (IPDs) technology and measured by on‐wafer probing. The simulated and measured results of the proposed BPF are in reasonably good agreement.