Short Stub Research Articles

A design of group delay equalizer using series and parallel resonator

AbstractA novel method of designing a group delay equalizer consisting of a typical 3‐dB hybrid coupler combined with one of newly proposed 4 types of resonator is presented. It is designed by applying the phase obtained from the reflection coefficient between the 3‐dB coupler and the proposed resonator to the group delay formula. Once the resonance frequency with the group delay as the peak is set to form a desired band by setting the parallel and series resonance frequencies, each component value of the proposed equalizer is obtained. In order to improve the group delay bandwidth, the proposed equalizers with different target frequencies are connected as cascaded. One of the proposed 4 types of equalizers was implemented using open and short stubs due to the fabrication limitation of lumped components, and its measurement results showed that the insertion loss is under −1 dB, and the group delay is 4.5 ns with ±1.5 fabrication error. This implies that the measurement results were well matched with the design method of the proposed equalizer.

Compact size of the UWB BPF using π‐type meander structure and folding short stubs

AbstractIn this article, the reduced size of the ultra‐wide band (UWB) band‐pass filter (BPF) with λg/4 short stubs using π‐type meander structure and folding short stubs is presented. The π‐type meander structure and folding short stubs are adopted instead of the λg/4 transmission line (TL) and λg/4 short stubs to reduce the size of the proposed BPF. The overall size of the new BPF is reduced by 72.5% over the conventional BPF and other filters. The measurement results of the insertion and return losses are 1.61 and 15.4 dB with a bandwidth of 125% (1.96‐9.20 GHz) at a center frequency of 5.8 GHz. The total size of the BPF is 5.13 × 5.36 mm2. It is applied to a coordinate intelligent transport system. The proposed BPF can be fabricated for semiconductors because of its planar structure.

Wideband arbitrary phase‐difference coupled‐line coupler with tight coupling coefficient and small phase variation

In this study, a planar arbitrary phase-difference coupled-line coupler having wide bandwidth, tight coupling coefficient, and small phase variation are proposed. The proposed coupler consists of two quarter-wavelength coupled-line sections connected with two different transmission lines. Moreover, the interconnection transmission line can be designed as a small phase variation phase shifter with the introduction of a shorted stub. The detailed theoretical analysis is provided to illustrate the design concept. The circuit parameters of this novel arbitrary phase-difference coupler can be easily determined by the derived closed-form equations. For verification, two 3 dB couplers with 45°/135° and 60°/120° phase differences are fabricated and measured. The 45°/135° coupler achieves 34.2% fractional bandwidth for 45° phase difference with 2° phase variation and 36.3% fractional bandwidth for 135° phase difference with 3.4° phase variation. Moreover, the 60°/120° coupler achieves 30% fractional bandwidth for 60° phase difference with 0.9° phase variation and 32.9% fractional bandwidth for 120° phase difference with 1.5° phase variation.

Fully Inkjet-Printed Dual-Mode Ring Bandpass Filter Using a Cross-Bridge Structure Embedded With a Metal–Insulator–Metal Capacitor

A fully inkjet-printed ring-resonator bandpass filter on a liquid crystal polymer was realized by using metal–insulator–metal (MIM) structures and via-hole interconnections. Two short stub feeding lines and a ring resonator were coupled using a cross-bridge structure embedded with an MIM capacitor to provide a high-selectivity passband, low insertion loss, and a more compact size. A stepped-impedance line was used as a perturbation to excite the dual mode of the ring resonator. Using the proposed method, a 29% fractional bandwidth was realized with four transmission zeros to improve the selectivity. In the passband, the minimal insertion loss and maximal return loss were −2.2 and −34.2 dB at 12.7 GHz, respectively. Fully inkjet-printed technology is recognized as a method of fabrication that results in a compact and low-cost 3-D integrated circuit package.

Design Implementation of Concentric Loops with Stubs Metamaterial Absorber

A novel design for passive tuned concentric loops with stubs metamaterial absorbers (MMA) has been proposed for microwave regime. This proposed MMA consists of two concentric loops separated by stubs and modified with rectangular bars. The proposed MMA structure shows versatility in design and tuned between Ku-band and X-band just by varying the length of shorted stubs and rectangular bar. The MMA structure has been found highly insensitive to oblique angle of incidence and polarization for TE and TM modes of the electromagnetic wave. The total thickness of the modified designed absorber is only 0.0092 λ0, where λ0 is the free-space wavelength at the resonant frequency. The simulated results are well matched with the measured results. The widespread potential applications of the proposed structure are found in antenna design for the reduction of radar cross section suitable for stealth technology along with radar and other communication areas.

A New Lowpass Filter Unit Cell with Sharp Roll-off and Improved Stopband Performance in Coplanar Waveguide Technology

In this paper, a new compact unit cell for a coplanar waveguide (CPW) lowpass filter (LPF) is proposed. By combining a pair of coupled parallel stepped impedance resonators (SIRs) and high impedance short stubs in the CPW line, a fifth-order elliptic lowpass filter unit cell (LUC) is designed. The extra transmission zero introduced by parallel coupled SIRs is used to extend the stopband and increase the roll-off rate. The characteristics of the proposed LUC is investigated to achieve a sharp roll-off and a wide stopband. The measured results are in accordance with the simulated results. It has an insertion loss less than 0.9 dB from dc to 6 GHz, and a wide -15 dB stopband from 7.5 to 18 GHz. In addition, the filter dimensions are as small as 4.9 mm × 8.7 mm, that is, 0.046λg2, where λg is the guided wavelength at the cut-off frequency. The filter structure is simple and easy to fabricate as well.

Design of tri‐band bandpass filter using symmetrical open stub loaded step impedance resonator

A tri-band bandpass filter design by using conventional stub loaded step impedance resonator (SLSIR) is presented. The proposed SLSIR consists of three tri-loaded open-circuited stubs parallel attached to a short and open-circuited stub. A tri-band bandpass filter is designed using two proposed symmetrical SLSIR's separated by a short-circuited stub. In this configuration, the filter produces three bands of frequencies at 0.9, 2.4 and 5.5 GHz, respectively. It is shown that the resonating frequencies can be independently controlled by loaded stubs. For better out of band rejection and increased selectivity, four finite frequency transmission zeros around three passband edges are achieved. The obtained fractional bandwidths are 23, 10 and 17% centred at 0.9, 2.4 and 5.5 GHz, respectively. The proposed design topology is fabricated on a substrate RT/Duroid 5880. The simulated and measured results show good accordance. The fabricated prototype has a compact size of ( 0.13 × 0.16 ) λ g at 0.9 GHz.

W band single diode fundamental mixer with high intermediate frequency

AbstractThe design approach of a W‐band single diode fundamental mixer is presented here. This mixer features planar structure easy for integrating and high intermediate frequency (IF). The mixer consists of a diplexer formed by a hammer‐head lowpass filter and a coupled line with open stubs, a broadband bandpass filter (BPF) using short stubs, a series diode, and the matching networks. This mixer covers IF signal up to 18 GHz by optimizing the frequency response of the diplexer, the radio frequency (RF) BPF, and the matching networks. Two open stubs are attached to both ends of the RF BPF, in order to add a transmission zero at local oscillator (LO) frequency. By this way, the required out‐of‐band rejection is fulfilled with lower order BPF, thus reducing the in‐band insertion loss. In addition, the coupled line with open stubs has low insertion loss at LO frequency, while having a transmission zero at RF frequency. All of the techniques above lead to a low loss high IF mixer. The measured conversion loss is 6.7–10 dB with 8–19 GHz IF and 82 GHz LO.

Perancangan Filter Bandpass dengan Teknik Penggabungan Filter Lowpass dan Highpass

UWB technology started to become an attraction in the field of research since the Federal Communications Commission (FCC) allowing this communication is used for commercial communications at a frequency (3.1 GHz - 10.6 GHz). UWB has a very wide frequency range so that in practice there is often interference due to signal interference. Therefore in UWB system filter design is required to maintain UWB device. In telecommunications, filter is a transmission device that has the function to pass the desired frequency. In this paper designed bandpass filter which is applied for UWB technology. The designed bandpass filter is a combination of a lowpass filter (LPF) and a highpass filter (HPF). The lowpass filter has the characteristic of passing a frequency lower than its cut-off frequency. The highpass filter has the characteristic passing a frequency higher than its cut-off frequency. Considering the characteristics of both filters, the bandpass filter (BPF) is a combination of lowpass and highpass filters. In this research designed lowpass filter in microstrip technology with step-impedance method, that is by combining high impedance microstrip and low impedance microstrip with a certain length. As for designing HPF using the distribution method of short circuit stubs by adding via ground on each stub. The design of this filter uses Roger substrate RT 5880 with dielectric constant er = 2,2 with thickness (h) = 0.508 mm. In this research it can be concluded that bandpass filter can be designed with lowpass and highpass filter incorporation method, although at the merging of highpass and lowpass structures is disturbed by each other, but overall design shows matching bandpass.
 Keywords—Microstrip, Lowpass Filter, Highpass Filter, Bandpass Filter.

A compact and sharp ultra-wide bandpass filter by using short-stub-loaded rectangular ring and split ring resonators

ABSTRACTA compact and sharp-rejection ultra-wideband (UWB) microstrip bandpass filter (BPF) is presented. The proposed filter is constructed with multiple-mode resonator (MMR) and split ring resonator (SRR). Moreover, proposed structure consists of two doublets parallel coupling gaps at each side of a microstrip ring. In comparison with some other filters, this structure shows a significantly wider passband due to the introduction of a cross-coupling between the feed lines (input and output) which generate four pairs of attenuation zeros in the passband.In order to control the transmission zeros in the passband and adjust the transmission zeros near the lower edge of the filter, a short stub loaded on microstrip rectangular ring is used. Also, In order to sharpen the upper edge of the filter, the SRRs have been used in both side of the doublets parallel coupling gaps which leads to the addition of one extra transmission poles at the upper edge of the filter. Consequently, a compact five-zero and one-pole UWB BPF is designed which exhibits extremely sharp-rejection skirts around the target passband.The proposed filter has a passband covering 2.83–10.06 GHz and its measured 3 dB fractional bandwidth is about 112.5%. Furthermore, rejection level better than 20 dB in upper stop-band is extended to around 18 GHz. To our knowledge, the size of proposed UWB filter is more compact in comparison with known similar filters.

Compact UWB bandpass filter with sharp roll‐off using APCL structure

In this letter, a quintuple-mode bandpass filter for a UWB system with improved performance is presented. The presented filter is implemented with asymmetric parallel-coupled lines loaded open stub and short stub connected at the symmetrical plane of the filter to increase its frequency selectivity. Five resonant frequencies within the UWB band and two transmission zeros at the lower and upper passband/stopband edges are observed. A filter prototype is fabricated for verification and the experimental data are corresponding well with the simulated results. The proposed filter achieves a bandwidth that can exactly cover the whole UWB frequency band. Moreover, this filter has a compact size (0.645 λ g × 0.318 λ g ) and low insertion loss.

Approach for filtering crossover design using mixed electric and magnetic coupling

A new approach for the filtering crossover design is proposed in this Letter. This approach is based on the mixed electric and magnetic coupling. A compact filtering crossover constructed by the short stub loaded resonator is presented according to the proposed approach. By using a short stub loaded resonator the filtering response is achieved and by using the cancelling effect between the electric coupling and magnetic coupling, the isolation between two signal paths is achieved. A filtering crossover is fabricated for demonstration. The measured result presents good agreement with the simulated result.

An analysis of RCS for dual-band slotted patch antenna with a thin dielectric using shorted stubs metamaterial absorber

A dual-band slotted patch antenna with thin dielectric has been proposed for Ku–band applications. A rectangular patch with pair of bent slots at each side of center has been designed and resonant at 11.95 GHz and 14.25 GHz with respect to ITU standard. A dual resonance ultrathin metamaterial absorber (MMA) based on circular rings and shorted stubs operating at same frequency bands have been designed. Its behavior at an oblique angle of incidence and polarization sensitivity has been also observed. In this research work, it has been obtained that when dual–band slotted patch antenna is surrounded by proposed MMA structure, it significantly enhances in-band stealth capability of the antenna. The monostatic and bistatic RCS of the proposed design has been reduced significantly whilst maintaining and preserving the antenna radiation performance. This design finds its application in satellite and wireless communication.

Compact Multiband Bandpass Filter Using Low-Pass Filter Combined With Open Stub-Loaded Shorted Stub

This paper presents a new method for designing multiband bandpass filters (BPFs). The filter consists of low-pass filter and two open stub-loaded shorted stubs. Multiple transmission zeros (TZs) are produced by the open stub-loaded shorted stub, and multiple passbands can be realized. For the first time, different numbers of open stubs are used to realize multiband BPFs with two to seven passbands. The center frequencies and the last passband bandwidth can be tuned in a certain range by adjusting the TZs and transmission poles. First, a wideband BPF is presented to introduce the design concept. Theoretical analysis is done to illustrate the design principle. Then, a wide single-band BPF and a dual-band BPF are designed to demonstrate the design method. The design procedure is summarized to guide the design process. Finally, tri-/quad-/quint-/sext-/sept-band BPFs are designed according to the design principle. All the BPFs are manufactured. Measured results show good agreement with simulated ones.

Design guidelines for single and dual wide band leaky periodic microstrip line antennas

Leaky wave antennas using periodic microstrip lines are natural choices for versatile beam scanning applications. In this work, a shorted stub and an open stub are simultaneously used in the same unit cell to generate resonant frequencies dependent on the stub dimensions. Placing one such resonant frequency at the second Bragg stop band, a single wideband response is obtained. Next, the stub lengths are tuned to obtain two resonant frequencies which are placed at the second and fourth Bragg stop bands, respectively to obtain a dual wideband response. Design guidelines are outlined for obtaining these wide bands and corresponding radiation regions. Two such geometries with single and dual-band nature are fabricated. The single wide-band antenna has a pass-band from 5.89 to 11.57 GHz with a beam scanning range of −56° to 33°. The dual-band antenna has two pass-bands radiating in the frequency range 5-6.5 GHz and 10.7-14.7 GHz. Beam scanning range in the first pass-band is −72° to −5°. The second pass-band, in part, demonstrates a dual-beam nature with the forward beam scanning from 28.9° to 54.5° and backward beam scanning from −54.5° to 14.76° as the frequency varies from 12 to 14.5 GHz.

Theoretical Based Design of Ultra-Wideband Filter with Dual Band-Notch

In this paper, a compact ultra-wideband microstrip band-pass filter with single/dual-notched bands is proposed. The filter is theoretically designed based on a multiple-mode resonator which consists of a short circuit stub loaded-ring resonator. A multi stepped impedance resonator is also applied to reject unwanted in-band frequencies and extend the upper-stopband. The proposed filter is analyzed by utilizing graphs according to odd- and even-mode method. The resonant modes are allocated between 3.1 GHz to 10.6 GHz and transmission zeros are adjusted at upper stopband to create a sharp roll-off and suppress the spurious harmonics, as well as a compact physical size. Full-wave simulations are performed for three types of filters, with and without notch-bands, to verify theoretical results. The measurement results demonstrate that not only − 3 dB fractional bandwidth is more than 120% and but also at least − 20 dB suppression can be achieved at upper-stopband.

Design of stubs loaded SIR filters by reflection coefficient analysis

In this paper, a new method for designing stubs loaded SIR filter is presented. We can calculate the reflection coefficient of stubs loaded resonator directly by converting the admittance to input terminal. This method replaces the transmission matrix and even-mode and odd-mode analysis. Then, genetic algorithm (GA) is applied to search the corresponding electrical parameters, which provides a more effective and intuitive way to design filters. Then, an ultra-wideband bandpass filter using short-stub loaded SIR is realized, which exhibits a good frequency selectivity from 3.1 GHz to 10.4 GHz. In addition, by applying this method, a dual-passband filter with short and open stubs is achieved. It contains two wide bands at 2 GHz and 5.8 GHz, which concerns the frequencies of GPS and WLAN. Meanwhile, the sizes of these filters are further minimized by bend structure. Finally, the filters are manufactured. As a result, the measured results are in good agreement with the calculated ones. These filters exhibit great frequency-selection characteristics: flat passbands and extremely sharp rejections around the passband. So, based on the verifications of the manufactured filters, this method can be widely used in microwave filter design field.

High selectivity seventh‐order wideband bandpass filter using coupled lines and open/shorted stubs

A compact seventh-order wideband bandpass filter (BPF) with sharp roll-off skirts using coupled lines and open stubs (OSs)/shorted stubs (SSs) is proposed. Seven transmission poles in the passband and four deep transmission zeros from 0 to 2f 0 (f 0 denotes centre frequency of the passband) can be realised with the help of half-wavelength OSs and quarter-wavelength SSs. For demonstration, a wideband BPF prototype is designed, fabricated with a measured 3-dB fractional bandwidth of 78% (1.22–2.77 GHz) and transition band roll-off rates of over 175 dB/GHz. Good agreement between the simulations and measurements validates the design method.

Fractal Dual-Mode Open-Loop Quasi-Elliptic Bandpass Filter with Source-Load Coupling

To realize the feature of small size and high selectivity, a microstrip miniature fractal quasi-elliptic bandpass filter (BPF) with two transmission zeros (TZs) near each skirt is investigated in this paper. The TZs are created by source-load coupling between the input and output E-shaped feeding structures. By using a dual-mode Minkowski fractal shorted stub loaded open-loop resonator, the proposed BPF achieved a size reduction of 97.5% compared with the conventional square dual-mode loop BPF. Even mode analysis is adopted to characterize the Minkowski structure. The frequency responses of the current BPF were simulated and measured with good agreement.

A decoupling method for MIMO antennas by using a short stub

A decoupling method for MIMO antennas by using a short stub