Sharp Skirt Selectivity Research Articles

A high‐power dual‐mode oversized substrate‐integrated waveguide (OS‐SIW) filter with flexible transmission zero (TZ) and bandwidth

AbstractThis paper presents a high‐power and sharp‐skirt‐selectivity bandpass filter with flexible transmission zero (TZ) and bandwidth. The proposed filter consists of three cascaded dual‐mode resonant cavities and a bandstop resonant structure. The dual‐mode resonant cavity is composed of a substrate‐integrated waveguide structure and a mushroom metal structure, which can implement a controllable bandwidth and generate a TZ for sharp skirt selectivity. Meanwhile, the middle dual‐mode resonant cavity is an oversized waveguide structure to improve power capacity. Moreover, the integrated bandstop resonant structure is used to generate another flexible TZ. The effect of different dimensional mushroom metal structures and bandstop resonant structures are also analyzed in detail. Finally, the proposed structure is fabricated and tested. Simulation results show that the proposed filter has an insertion loss of −1 dB at the passband 8.9–10.7 GHz with two TZs on both sides of the passband. Additionally, the proposed filter can obtain an 11 MW power capacity. Compared with the traditional filters, the proposed filter possesses high‐power and sharp skirt selectivity characteristics, and its position of TZ and bandwidth can be properly adjusted.

Dual-Band and Triple-Band Filtering Power Dividers Using Coupled Lines

In this brief, new dual-band and triple-band filtering power dividers (FPDs) with sharp frequency selectivity are proposed. Firstly, the dual-band FPD is developed and mainly composed of a quarter-wavelength three-line parallel coupled line structure, five transmission lines, and a pair of short-ended parallel coupled lines. Based on this specific structure, with two extra transmission lines imported, a triple-band FPD is further attained. Multiple transmission zeros are generated successfully in the above two designs, thus leading to a sharp skirt selectivity. For the above FPD designs, only a single isolated resistor is arranged between the two side lines of three-line parallel coupled line for nice port-to-port isolation within wide passbands. For demonstration, a prototype dual-band FPD operating at 2.38 and 3.80 GHz with a size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.67{\lambda }\text{g}\,\,{\times }\,\,0.68{\lambda }\text{g}$ </tex-math></inline-formula> , and a triple-band FPD operating at 2.38 GHz, 3.42 GHz, and 3.91 GHz with a size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.66{\lambda }\text{g}\,\,{\times }\,\,0.68{\lambda }\text{g}$ </tex-math></inline-formula> are designed, fabricated, and tested, respectively.

A band-notched base station antenna using the grounded coplanar waveguide filter

A band-notched dual-polarized crossed dipole antenna for the 2G/3G/4G base station applications using the grounded coplanar waveguide (GCPW) filter is proposed in this paper. Firstly, the crossed dipole antenna using GCPW feeding structure is designed to cover the frequency of 1.7–2.7 GHz. Then, a compact GCPW filter is proposed inside the dipole antenna to realize a notched band of 2.2–2.5 GHz with sharp skirt selectivity. As a result, the proposed antenna has two operating bands of 1.67–2.23 GHz and 2.45–2.75 GHz for VSWR < 1.5 and a sharp notch band of 2.23–2.45 GHz. The proposed antenna is analyzed, fabricated and measured. Measured isolation of higher than 26 dB, half-power beamwidth of about 68° and average gain of around 8.3 dBi across the working band are achieved. The minimum gain in the notched band is −9 dBi, which is 17 dB less than the gain in the working frequency.

Compact Low-Profile Differential Filtering Microstrip Patch Antenna With High Selectivity and Deep Rejection Using Single-Layer Substrate

A compact low-profile differential filtering microstrip patch antenna with high selectivity and deep rejection using single-layer substrate is proposed. The presented antenna mainly consists of the quasi-H-shaped patch (QHSP) and the meandering quasi-T-shaped resonator (QTSR) which is composed of two open-end meandering arms in opposite direction and an inset coupling structure. To the best of our knowledge, a novel differential feeding structure is adopted for the first time that a pair of differential inset coupling feeding structures are placed in opposite direction to drive the QHSP with insetting-capacitive-coupling, simultaneously. Its equivalent lumped circuit is further analyzed to study the characteristics. In the point of views of filter and antenna design, the meandering QTSR not only acts as the first stage of resonator, but also a feed structure, and the QHSP can be treated as the last order of resonator as well as the radiator. A prototype of the proposed antenna is designed, analyzed, simulated and measured. Two controllable radiation nulls (RNs) locate at the both sides of the passband, a sharp skirt selectivity with the sideband roll-off rates of 667/182 dB/GHz and out-of-band suppressions of −40.1/−39 dB in lower and upper stopbands are achieved, respectively. The measured flat realized gain can be obtained in the passband with the average gain more than 6 dBi and the low cross-polarization level can be achieved. The dimension of the proposed antenna is only $0.361\lambda _{0} \times 0.426\lambda _{0} \times 0.013\lambda _{0}$ . Good agreement between the simulated and measured results is obtained, which verifies the proposed antenna with the differential feeding structure has excellent performance only using single layer low profile substrate. The proposed antenna is a good candidate for WLAN and power harvest application.

A Differentially Fed Dual-Polarized Filtering Patch Antenna With Good Stopband Suppression

A differentially-fed dual-polarized filtering patch antenna with no extra filtering circuits involved is proposed. The filtering response is realized by symmetrically loading four short strips and a long cross-type strip, and a square ring slot to insert radiation zeros on the dual-polarized antenna element. The short and long strips can generate two transmission zeros at lower and upper band edges, respectively, leading to a sharp skirt selectivity. In addition, the long cross-type strip and the square ring slot can respectively introduce an extra resonance close to the original one, broadening the impedance bandwidth. Also, the equivalent circuit is presented to show that the two zeros can be brought by the two equivalent series resonant circuits extracted from the short/long strips resulting in the bandpass response. We may note that the proposed filtering structure owns the merits of simple, compact and complete symmetry, thus it can be well integrated with the dual- polarized antenna. Consequently, a compact and high-gain dual- polarized filtering antenna with good stopband suppression, low cross-polarization level and symmetrical radiation patterns is obtained. It can achieve an impedance bandwidth about 15% and a maximum gain of 8.4 dBi. The simulated cross-polarization level is below -40 dB, and the measured one is lower than -22 dB. Moreover, the upper stopband can be up to 2.6 f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the center frequency of the antenna), where the stopband radiations from all the directions can be suppressed and the measured suppression ratio can reach 90%.

Compact quintuple notched-band UWB BPF with high selectivity and wide bandwidth

AbstractIn this paper, a compact quintuple notched-band ultra-wideband bandpass filter with high selectivity and wide bandwidth is proposed. The filter adopts an approximate closed-loop C-shaped stepped impedance resonator to generate triple notched bands, and uses Hilbert fractal curve slit and L-shaped resonator to create single notched band, respectively. Multiple notched-band are centered at 5.29, 6.61, 7.92, 8.95, and 9.93 GHz to eliminate undesired interference from coexisting wireless services of WLAN, C-band, and X-band. Additionally, two transmission zeros are introduced to enhance the sharp skirt selectivity up to 0.944. This filter could exhibit high sharp selectivity and wider bandwidth simultaneously. The filter is fabricated on a RT/Duroid 5880 substrate (ɛr = 2.2 and thickness = 0.787 mm) and measured to verify the simulation results. Both simulation and measurement are in well agreement, showing the good performance of the filter.

Quintuple-mode wideband bandpass filters with improved out-of-band rejection

AbstractThis paper presents design of quintuple-mode wideband bandpass filters, implemented with off-centered perturbed metallic cylinders in a rectangular waveguide cavity. Three perturbation cylinders are placed at the bottom of the rectangular waveguide cavity, along with a pair of perpendicularly fed coaxial lines; excite five quasi-transverse magnetic modes to realize the desired passband. The height of the waveguide cavity and the shape of the perturbation cylinders are exploited to shift the resonant modes far away from the passband and achieve a good out-of-band rejection and sharp skirt selectivity. The filter operates at the center frequency of 2.68 GHz with a wide fractional bandwidth of 43%. The proposed filter is fabricated with aluminum. The measured and simulated results are in good agreement with each other.

Quadruple-Mode Wideband Bandpass Filter with Improved Out-of-Band Rejection

This paper proposes a method for designing a quadruple-mode wideband bandpass filter using off-centered perturbed metallic cylinders in a rectangular waveguide cavity with compact size and improved out-of-band rejection. Two off-centered perturbation cylinders were placed at the bottom of the rectangular waveguide cavity along with a pair of perpendicularly-fed coaxial lines, which excited four quasi-transverse magnetic (TM) modes to realize the desired passband. The height of the waveguide cavity and the shape of the perturbation cylinders were exploited to achieve an all quasi-TM modes filter with good out-of-band rejection and sharp skirt selectivity. The proposed filter operates at 2.93 GHz center frequency with 38% wide fractional bandwidth (FBW). The proposed filter is fabricated using aluminum. The measured and simulated results are in good agreement with each other.

Design of a 3-D Integrated Wideband Filtering Magneto-Electric Dipole Antenna

A new design of 3-D integrated wideband filtering magneto-electric dipole antenna with high selectivity is presented. The proposed antenna is mainly composed of a horizontal planar dipole and a vertically oriented shorted patch antenna. A pair of C-slots is etched on the planar dipole to obtain sharp skirt selectivity near both band-edges. In addition, a slotline loaded with the patch antenna provides good impedance matching. The proposal exhibits a quasi-elliptic gain response with three introduced radiation nulls without additional filtering circuits. To verify the design concept, a prototype is fabricated and measured. The result exhibits an impedance bandwidth of 55.4% with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {SWR}\le 1.5$ </tex-math></inline-formula> from 1.58 to 2.79 GHz. Moreover, the low back radiation levels ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\le } -16$ </tex-math></inline-formula> dB), stable radiation patterns with low cross polarization levels ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\le } -26$ </tex-math></inline-formula> dB), and an average antenna gain of 7.8 dBi are achieved within the operating band. In addition, an out-of-band suppression level, better than 17 dB, is reached.

Design of a New Balanced-to-Balanced Filtering Power Divider Based on Square Patch Resonator

A new balanced-to-balanced filtering power divider based on the square patch resonator is proposed in this paper. Originating from the field distributions of degenerate modes on the square patch resonator, a prototype of the balanced-to-balanced power divider is successfully developed with only one square patch resonator. Its working principle can be fully explained by the field distribution of the relevant resonant modes. Afterwards, to achieve the sharp skirt selectivity outside the passband, a compact second-order circuit is constructed based on the original prototype. With this new structure, both good bandpass filtering response and power division characteristics are well obtained. Moreover, to suppress the differential-mode (DM) harmonic response in the upper stopband, an improved structure is built up by modifying the feeding scheme. Ultimately, to validate the design concept, both the two types of second-order balanced-to-balanced filtering power dividers operating at 1.8 GHz are designed and fabricated. The measured results of the two fabricated circuits well agree with the simulated ones, manifest equal power division, high performances in terms of DM response, in-band common-mode (CM) suppression, port-to-port isolation, and expected harmonic suppression.

Wideband Bandstop Filter With Extreme Sharp Skirt Selectivity

A novel and simple wideband bandstop filter with extreme sharp skirt selectivity is proposed. The wideband bandstop response with multi-transmission zeros and large skirt-band attenuation rate is realized based on the modified coupled-line sections with open-/short-circuited termination and two quarter-wavelength transmission lines. In order to simultaneously improve stopband rejection (SR) and passband return loss, the gray boxes with different circuit structures are introduced. For demonstration, a designed prototype operating at 1 GHz with 64% relative bandwidth of 17-dB SR is simulated, fabricated, and measured.

Dual-Wideband Filtering Power Divider Based On Coupled Stepped-Impedance Resonators

A new approach to design dual-wideband filtering power divider (FPD) with high selectivity and wide stopband is presented. The proposed FPD is mainly composed of two pairs of tapped-line fed coupled stepped-impedance resonators and an isolation resistor. With this specific coupling structure, multiple transmission zeros are successfully generated, thus leading to a sharp skirt selectivity and a wide stopband. For demonstration, a prototype dual-wideband FPD operating at 2.43 and 5.06 GHz with size of $0.67 \lambda _{g} \times 0.68\lambda _{g}$ is designed, fabricated, and tested. The 3-dB fractional bandwidths are measured as 38.3% and 18.8%. Results indicate that the proposed FPD exhibits not only high selectivity with a 16-dB out-of-band rejection from 5.77 to 9.43 GHz but also a 19.8-dB port-to-port isolation within the whole operation band.

Design and characterisation of dual‐mode suspended‐substrate stripline filter

A new design technique of a dual-mode ring-resonator suspended-substrate stripline filter is reported here to achieve low passband insertion loss, high quality factor, and good spurious response. A fourth-order bandpass filter was designed and fabricated at the operational frequency of 2.07 GHz with two ring resonators packaged in a metallic cavity where each ring resonator is one wavelength long. The transmission zeros of the dual-mode filter are generated due to the phase cancellation between the two paths in a ring, thus a sharp-skirt selectivity filter response was achieved. Perturbation notch structure was implemented on each ring resonator to provide the electromagnetic coupling of two degenerate modes, thus a dual-mode response of the filter can be synthesised. Measurement results of the first dual-mode filter prototype showed a return loss and an insertion loss of better than 16.42 and 0.926 dB, respectively, while an out-of-band rejection of up to 55 dB was achieved. The novel filter design technique proved that no cross-coupling is required to obtain the transmission zeros of the filter, thus the sharp-skirt response was achievable.

Compact Millimeter-Wave CMOS Wideband Three-Transmission-Zeros Bandstop Filter Using a Single Coupled-Line Unit

This brief presents the design and implementation of millimeter-wave ultra-wide bandstop filter (BSF) using a standard 0.18-μm CMOS technology. The BSF configuration consists of a single coupled-line resonator shorted at the middle, which operates as not only a resonant element but also an open stub. The BSF realizes three transmission zeros in the stopband that results in sharp skirt selectivity. The overall width of the filter is less than the width of a 50-Ω line and occupies a compact area of 0.0066λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> × 0.443λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> is the guided wavelength at 60 GHz. Explicit design equations are derived analytically using lossless transmission model. A prototype wideband BSF with a 3-dB bandwidth of 110% at 60 GHz is realized on a thin-film microstrip structure. The impact of several CMOS process parameters on the designed filter is also examined.

Triple-Mode Bandpass Filters on CSRR-Loaded Substrate Integrated Waveguide Cavities

In this paper, a novel approach is proposed to design and explore a class of triple-mode bandpass filters on substrate integrated waveguide (SIW) structure. Two degenerate modes of an SIW rectangular cavity and one resonant mode of a complementary split-ring resonator (CSRR) are employed to implement these filters. As the primary advantage, the CSRR mode is utilized instead of the fundamental mode of the SIW cavity to provide us with an attractive capacity in easily controlling the frequency band of the designed SIW filters through the dimensions of this CSRR. Moreover, the positions of transmission zeros can be properly adjusted by the metallic vias. Finally, three examples of SIW multimode bandpass filters are designed, fabricated, and tested to verify the effectiveness of the proposed approach. The measured results are found in good agreement with the simulated ones, showing that these filters have achieved high out-of-band rejection and sharp skirt selectivity.

A CPW-Fed Dual-Band-Notched Antenna with Sharp Skirt Selectivity for UWB Applications

A coplanar waveguide- (CPW-) fed dual-band-notched antenna with sharp skirt selectivity for ultrawideband (UWB) applications is presented. The proposed antenna is composed of a radiant patch with a C-shaped slot and a C-shaped stub on the back surface of the substrate. By using the C-shaped slot and the C-shaped stub, dual-band-notched characteristics can be generated. In this way, a more practical and effective approach to design an UWB antenna with sharp notched-band-edge selectivity is developed. The measurement results show dual notched bands of 4.96–5.42 GHz and 5.71–5.91 GHz, which can reject the interference between IEEE 802.11a bands (5.15–5.35 GHz and 5.725–5.825 GHz) and UWB systems. The fabricated antenna shows good omnidirectional radiation patterns with acceptable gain and group delay.

Design of Miniaturized Filtering Power Dividers for System-in-a-Package

Miniaturized power dividers with high-selectivity bandpass behavior are presented and analyzed theoretically in this paper. Based on the coupled-resonator topology, the circuit area of the proposed power divider can be reduced as the size of the assembled resonators shrinks. Therefore, in order to effectively reduce the circuit area and improve the stopband performance, the net-type resonator is selected to design the filtering power dividers. For demonstration, power dividers with Chebyshev- and quasi-elliptic bandpass responses have been designed and fabricated with microstrip in printed circuit boards. The highly symmetric structure of each power divider provides a low in-band magnitude and phase imbalances. Consequently, the proposed filtering power dividers have advantages of small size, sharp skirt selectivity, high isolation, and superior out-of-band performance. All measured results are in good agreement with the full-wave simulation results.

NOVEL IN-LINE MICROSTRIP COUPLED-LINE BANDSTOP FILTER WITH SHARP SKIRT SELECTIVITY

This paper presents a novel design approach to design in- line microstrip bandstop fllter with accurate design theory and sharp skirt selectivity. This kind of bandstop fllter is based on a simple coupled-line structure, indicating compact and ∞exible circuit layout for microstrip implementation. For a single-section bandstop fllter, the scattering parameters and their constrain conditions are achieved, which provides an efiective design guide for multi-section bandstop fllters. Theoretical analysis indicates that the even-mode and odd- mode characteristic impedances can be easily used to determine the desired bandstop performance while the total circuit layout keeps very compact. For demonstration, seven numerical examples are designed, calculated, and compared. Finally, both experimental and simulation results of a two-section two-cell microstrip bandstop fllter operating at 1GHz are presented to verify the theoretical predications.

Metamaterial-inspired waveguide filters with compact size and sharp skirt selectivity

In this paper, a metamaterial-inspired miniaturization method for waveguide filter design is proposed. The transmission response and effective medium parameters of I-shaped resonator in metallic rectangular waveguide are first discussed. By embedding such an I-shaped resonator, a novel λg/2-type inverter is then proposed (λg: the guided wavelength). The large effective refraction index with low loss which appears below the resonant frequency of the I-shaped resonator is skillfully exploited, and then the size of λg/2-type inverter is greatly reduced with acceptable low insertion loss. The most negative permittivity of the I-shaped resonator at its resonant frequency produces an additional transmission zero which leads to sharp skirt selectivity in the upper side band. Using the novel λg/2-type inverter, two improved waveguide filters are further designed with good performances. One has an extremely compact size. The other has further improved selectivity. Two such filters are finally fabricated and the measured results agree well with the simulated ones.

A Simple Microstrip Bandpass Filter with Analytical Design Theory and Sharp Skirt Selectivity

A simple coupled-line circuit configuration is proposed to design microstrip bandpass filter with sharp skirt selectivity in this paper. This novel circuit consists of two-section coupled lines with a common connected point. An equivalent odd-mode and even-mode analysis is applied to analyze transmission and reflection property, and the effective analytical scattering parameters' expressions are achieved. Design curves for this novel bandpass filter are given while six typical numerical examples are presented. The presented simulation results show that the reflection zeros in pass band and transmission zeros in stop band can be tuned by changing the even- and odd-mode characteristic impedances of these coupled lines. Finally, two microstrip bandpass filters with different transmission and reflection zeros are fabricated, measured and compared. The experimental results show excellent bandpass filtering property with sharpened rejection skirts and low insertion loss.