Open-circuited Stubs Research Articles

Performance Analysis of Four Equal Port Power Splitter with Second Harmonic Suppression

This paper reports the performance analysis of 4 ports splitter for same frequency power output. A quarter wave 50 Ω transmission lines are employed for schematic design and open circuit stubs are used for the impedance matching purpose and A passive device such as inductor may employed to reduce the 2 harmonic at 4.2GHz. A high value dielectric substrate with ᶓr is 9.9 used to reduce the size of transmission line at center frequency 2.1 GHz with 500MHz bandwidth. Furthermore, all the simulated scattering parameter in terms of return losses, isolation factor and coupling factor are reported here. General Terms Power splitter, Power combiner, Isolation loss, Return loss, coupling factor, Transmission line.

Compact Marchand balun circuit for UWB application

This article presents the development of a miniaturized differential coupler for UWB application using the Marchand balun circuit in multilayer technology. The new technique employs double layer substrate where on the bottom layer the two λ/4 short-circuited stubs with balanced outputs are developed and on the top layer the λ/2 open-circuited stub for unbalanced input is etched. These three transmission lines of the Marchand balun circuit are capacitively coupled using overlapping microstrip lines. To demonstrate this technique, a Marchand balun circuit using multilayer technology is designed, simulated, fabricated and measured. The circuit size is about 2.8mm×3.7mm×0.63mm excluding the feeding ports. The results from the simulation and measurement show good agreement.

High-Efficiency Harmonic-Peaking Class-EF Power Amplifiers With Enhanced Maximum Operating Frequency

The recently introduced Class-EF power amplifier (PA) has a peak switch voltage lower than that of the Class-E PA. However, the value of the transistor output capacitance at high frequencies is typically larger than the required Class-EF optimum shunt capacitance. Consequently, soft-switching operation that minimizes power dissipation during off-to-on transition cannot be achieved at high frequencies. Two new Class-EF PA variants with transmission-line load networks, namely, third-harmonic-peaking (THP) and fifth-harmonic-peaking (FHP) Class-EF PAs are proposed in this paper. These permit operation at higher frequencies at no expense to other PA figures of merit. Analytical expressions are derived in order to obtain circuit component values, which satisfy the required Class-EF impedances at fundamental frequency, all even harmonics, and the first few odd harmonics as well as simultaneously providing impedance matching to a 50- $\Omega$ load. Furthermore, a novel open-circuit and shorted stub arrangement, which has substantial practical benefits, is proposed to replace the normal quarter-wave line connected at the transistor's drain. Using GaN HEMTs, two PA prototypes were built. Measured peak drain efficiency of 91% and output power of 39.5 dBm were obtained at 2.22 GHz for the THP Class-EF PA. The FHP Class-EF PA delivered output power of 41.9 dBm with 85% drain efficiency at 1.52 GHz.

High selectivity UWB bandpass filter with a wide notched-band

This article presents a compact ultrawideband (UWB) bandpass filter (BPF) with sharp selectivity, wide notched-band, wide out-of-band rejection, and approximately flat group delay. The proposed filter structure is composed of a U-shaped open-circuited line that is interdigitally coupled to the input/output feed-lines using high impedance lines. The structure generates multiple resonant modes across the UWB span between 3.1 and 10.6 GHz, however, high coupling between the feed-lines and the U-shaped structure transforms the discrete resonant modes into an UWB BPF. Coupling is enhanced by inserting dielectric slots in the ground-plane immediately under the coupling-lines. A wide notched-band is implemented by introducing asymmetry in the coupled lines. This was achieved by making one of the coupling lines longer by folding it and extending the line to partially couple with U-shaped structure. The length of the extended coupled line and the position of the folded section determine the center frequency of the notch-band and its 3-dB bandwidth. The notch was designed to be centered at 5.5 GHz with appropriate 3-dB bandwidth to blocking interference from WLAN signals. The selectivity of the filter was enhanced by loading the U-shaped structure with a T-shaped open-circuited stub to generate two additional resonant modes in the filter's passband and two transmission zeros that were strategically located at the upper and lower cut-off frequencies of the filter. The design was fabricated and its performance verified. The proposed filter has dimensions of 9.4 × 9.9 mm2.

Analysis of Matching Circuit to Improve the Efficiency of RF to DC Conversion for Ambiet RF Energy Harvesting

This paper presents an analysis of matching circuit with rectifier for RF energy harvesting. The matching circuit has a significant influence to improve the efficiency of RF-DC conversion. In this paper, comparative analysis of rectifier efficiency is performed, particularly the rectifier with-and without-matching circuit. The analysis is conducted using ADS simulation version 2011, to determine the output power as well as the efficiency of the rectifier. The results show the rectifier with-matching circuit produced higher efficiency about 72%, compared to the rectifier without-matching circuit which is only achieved 20% of the efficiency. The effects of tuning the matching circuit upon the rectifier efficiency had been studied. In this paper, the parametric studies of the effect of short circuit and open circuit stubs tuning are performed to determine the efficiency of the rectifier. The results show matching circuit after tuning produced higher efficiency compared to matching circuit before tuning. This study is useful to provide an insight on the optimum technique to design RF energy harvesting.

Four-Way Microstrip-Based Power Combining for Microwave Outphasing Power Amplifiers

A lossless multi-way outphasing and power combining system for microwave power amplification is presented. The architecture addresses one of the primary drawbacks of Chireix outphasing; namely, the sub-optimal loading conditions for the branch power amplifiers. In the proposed system, four saturated power amplifiers interact through a lossless power combining network to produce nearly resistive load modulation over a 10:1 range of output powers. This work focuses on two microstrip-based power combiner implementations: a hybrid microstrip/discrete implementation using a combination of microstrip transmission line sections with discrete shunt elements, and an all-microstrip implementation incorporating open-circuited radial stubs. We demonstrate and compare these techniques in a 2.14 GHz power amplifier system. With the all-microstrip implementation, the system demonstrates a peak CW drain efficiency of 70% and drain efficiency of over 60% over a 6.5-dB outphasing output power range with a peak power of over 100 W. We demonstrate W-CDMA modulation with 55.6% average modulated efficiency at 14.1 W average output power for a 9.15-dB peak to average power ratio (PAPR) signal. The performance of this all-microstrip system is compared to that of the proposed hybrid microstrip/discrete version and a previously reported implementation in discrete lumped-element form.

A UWB bandpass filter with a notched band using dual stepped-impedance stub-loaded resonators

In this article, a new notched-band ultra-wide bandpass filter (BPF) is proposed, using dual stepped-impedance stub-loaded resonators (SISLRs), open-circuited stubs, and stepped-impedance ports (SIPs). As dual SISLRs overlay the frequency responses of the two resonators, the in-band performance of dual SISLRs is better than that of a single SISLR under the same external coupling. Open-circuited stubs of length λ/4 were placed between dual SISLRs to reject the wireless LAN interference signal band at 5.8 GHz. In addition, we combined SIPs with dual SISLRs for improved passband performance at high frequencies. The proposed filter was validated via simulation and measurement. The measured return loss of the BPF was less than −10 dB throughout the passband of 3.2–11.01 GHz. The group delay remained relatively flat and less than 0.5 ns throughout this passband, except in the notched band. The rejection bandwidth was 5.73–6.31 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1785–1787, 2014

Triband bandpass filter using asymmetrically loaded resonators

Compact microstrip triband bandpass filters are proposed and designed based on asymmetrically loaded resonators in this letter. By attaching single open-circuited stub or short-circuited stub at the proper position of the microstrip line and adjusting their lengths, the first three resonant modes of the proposed resonators can be usefully allocated within the three passbands of the triband filter. Two alternative triband filters with compact size are designed and measured. The measured results provide successful verification for the theoretical analysis. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1862–1865, 2014

Design of Artificial Transmission Line and Low-Pass Filter Based on Aperiodic Stubs on a Microstrip Line

Among many microstrip configurations, the open-circuited shunt stub is probably the most common and versatile one. It is capable of performing a wide range of functions. Despite extensive studies and applications of the open-circuited shunt stub, comparatively little is known about aperiodic stubs on a microstrip line. In this paper, aperiodic stubs on a microstrip line are exploited to implement a high-performance low-pass filter and a joint design of the artificial transmission line and low-pass filter. The experimental results validate the performance of the proposed circuits. For the low-pass filter application, the proposed circuit outperforms a seventh-order Butterworth filter while their circuit sizes are comparable. For the joint design, it may potentially enhance the degree of integration in RF and microwave systems.

Half-Mode Buried Corrugated Substrate Integrated Waveguide

A half-mode buried corrugated substrate-integrated waveguide is proposed. Its dominant mode propagation behavior is almost identical to that of the half-mode substrate-integrated waveguide but offers a floating top conductor thereby permitting active devices connected to its longitudinal open-edge to be biased without the need for extra biasing chokes. The corrugations comprise open-circuit stubs buried in the substrate that are connected to the top wall of the waveguide by vias. These stubs are quarter-wave in length at a frequency twice the dominant mode cut-off frequency. The corrugations and vias are used to obtain an electric wall. Burying stubs in the substrate results in a low stub input impedance over a wide bandwidth which allows a monomode bandwidth of 3:1 to be obtained. Experiments for waveguides with a TE0.5,0 mode cut-off frequency of 2.8 GHz demonstrate its effectiveness.

Design of Dual-Band Millimeter-Wave Antenna-in-Package Using Flip-Chip Assembly

A dual-band antenna-in-package for millimeter-wave (mmW) applications is presented in the paper. The proposed antenna, which consists of a radiating slot and an air-filled cavity, is fed by a microstrip loaded with two tuning open-circuited stubs through a coupling C-shape aperture to achieve dual-band characteristics. The air-filled cavity, which is formed by the space between CMOS chip and integrated passive device substrate after flip-chip assembly process, can reduce loss and improve antenna gain. Simulation and measurement regarding antenna reflection coefficient, radiation pattern, and peak gain are conducted for design validation. The measured results show that the antenna can operate in V-band and E-band, and the impedance bandwidths with the reflection coefficient less than -10 dB are 6.1% and 5.8%, respectively. The measured gains are -2 dBi at 58 GHz and 0.3 dBi at 77 GHz, respectively. The proposed antenna is well suited for dual-band mmW high-data-rate wireless communication systems.

Compact monopole antenna with triple band-notched characteristics for UWB applications

A novel ultrawideband antenna with triple band rejection characteristic is proposed in this article. The antenna consists of a U-shaped monopole antenna and a modified grounded plane. To realize triple band-notched characteristics, a pair of I-shaped and L-shaped stubs embedded in the square slots of the ground plane and resonant open-circuited stubs placed adjacent to the antenna edges are used. Surface current distributions are described to analyze the effects of these stubs. Modified version of the antenna is also designed to reduce the overall metallic surface of the antenna while maintaining its band-notched characteristics. Measured results show that this antenna operates from 2.77 to 11.38 GHz for voltage standing wave ratio less than 2, except the triple notched bands (3.27–3.75, 5.51–5.96, and 6.95–7.65 GHz). © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:822–827, 2014

Design of a Wideband Bandpass Filter With Composite Short- and Open-Circuited Stubs

A new wideband bandpass filter (BPF) with composite short- and open-circuited stubs has been proposed in this letter. With the two kinds of stubs, two pairs of transmission zeros (TZs) can be produced on the two sides of the desired passband. The even-/odd-mode analysis method is used to derive the input admittances of its bisection circuits. After the Richard's transformation, these bisection circuits are in the same format of two LC circuits. By combining these two LC circuits, the equivalent circuit of the proposed filter is obtained. Through the analysis of the equivalent circuit, the open-circuited stubs introduce transmission poles in the complex frequencies and one pair of TZs in the real frequencies, and the short-circuited stubs generate one pair of TZs to block the dc component. A wideband BPF is designed and fabricated to verify the proposed design principle.

High-efficiency S-band harmonic tuning GaN amplifier

In this paper, we present a high-efficiency S-band gallium nitride (GaN) power amplifier (PA). This amplifier is fabricated based on a self-developed GaN high-electron-mobility transistor (HEMT) with 10 mm gate width on SiC substrate. Harmonic manipulation circuits are presented in the amplifier. The matching networks consist of microstrip lines and discrete components. Open-circuited stub lines in both input and output are used to tune the 2nd harmonic wave and match the GaN HEMT to the highest efficiency condition. The developed amplifier delivers an output power of 48.5 dBm (∼70 W) with a power-added efficiency (PAE) of 72.2% at 2 GHz in pulse condition. When operating at 1.8–2.2 GHz (20% relative bandwidth), the amplifier provides an output power higher than 48 dBm (∼ 65 W), with a PAE over 70% and a power gain above 15 dB. When operating in continuous-wave (CW) operating conditions, the amplifier gives an output power over 46 dBm (40 W) with PAE beyond 60% over the whole operation frequency range.

A NOVEL COMPACT WIDEBAND BANDPASS FILTER USING ROTATIONAL SYMMETRIC LOADED STRUCTURE

A novel compact wideband bandpass fllter using rotational symmetric loaded structure is proposed in this paper. A ‚/4 parallel coupled line is flrst introduced to form a passband with desired center frequency. The rotational symmetric structure with short/open circuit stubs is then introduced as a loading structure to improve the fllter's performance. The rotational symmetric loading structure is discussed in detail in this paper, and a pair of transmission zeros is obtained and located at two sides of the passband to improve the passband selectivity intensively. Moreover, three open circuit stubs are utilized to replace one single stub for obtaining a wide stopband. At last, the proposed fllter is fabricated and measured, and the results show a good agreement with each other.

DESIGN OF COMPACT WIDEBAND HIGH-SELECTIVITY BAND-STOP FILTER BASED ON COUPLED LINES

In this paper, a compact band-stop filter with a wideband and high-selectivity performance is proposed and analyzed. This band-stop filter includes two parallel-coupled lines of different electrical lengths and two open-circuit stubs. A lossless transmission line model is used to obtain the filter design parameters. In order to verify this new filter circuit structure and its corresponding design theory, five groups of numerical examples are demonstrated. Finally, a practical band-stop filter with a 3-dB cutoff frequency bandwidth of 58.2% centered at 0.94 GHz has been designed, simulated and measured. The measured results show a good agreement with the simulated responses.

Wideband Bandpass Filter Composed of Dual-Path Resonators Using Coupled-Line and Transmission Line With Inductive Elements

A dual-path resonator for a wideband bandpass filter (bandpass filter) is proposed by using a coupled-line and a transmission line with inductive elements. It realizes a dual-mode resonance by an open-circuited interdigital coupled-line and a transmission zero near the lower cutoff frequency due to the effect of the dual-path. The wideband BPF composed of two resonators and two open-circuited stubs is also presented. The presented filter shows that steepness at both the lower and upper cutoff frequencies and high attenuation level at the stopband are obtained. Measurement result with electromagnetic simulation is observed and they are good agreement. Its bandwidth is about 1.7 GHz and the fractional bandwidth is about 44% on compact size of 22×17 mm2.

A Novel Dual-Band Bandpass Filter With Closely Spaced Passbands

This letter proposes a double-slot-loaded resonator for exploration of a novel dual-band bandpass filter with two closely spaced passbands. A small ratio of dual-passband central frequencies is realized by positioning the double slot stubs in an offset way. The first-passband fractional bandwidth can be properly tuned by a distance between the two slots, while the second one is determined by attaching a microstrip open-circuited stub at center. After the principle of this initial filter is described, a prototype filter is designed and fabricated. Measured results satisfactorily validate the predicted ones of the proposed filter.

DIRECT SYNTHESIS OF STUB LOW-PASS FILTERS WITH CHEBYSHEV CHARACTERISTIC

The method of synthesis of stub lowpass filters with Chebyshev characteristic that does not use filters prototypes is proposed. This method is used to solve the problem of synthesizing a lowpass filter with a symmetrical structure, being composed of quarter wavelength transmission lines and open-circuit stubs. In the process of solving this task are defined model elements of the filter structure. Composed filtering function to ensure equal characteristics. A procedure for the synthesis, starting with the choice of filter elements and ending with the determination of their impedances. A comparison of the results of synthesis of the proposed direct method and a method that uses the prototype filter, show the advantages of the proposed method.

Design and analysis of a coplanar waveguide fed ultrawideband hexagonal open slot antenna with WLAN and WiMAX band rejection

ABSTRACTA simple coplanar waveguide fed hexagonal like open slot antenna has been considered for ultrawide bandwidth (UWB) in this article. This antenna is then modified to obtain dual band rejection. Dual band rejection frequencies (WLAN: 5.0–5.9 GHz, WiMAX: 3.3–3.7 GHz) at 5.5 and 3.5 GHz are achieved by embedding a U‐shape slot in the exciting stub as well as a couple of L‐shape open circuit stubs at the edge of the slot, respectively. The length and width of the U‐shape slot and L‐shape stubs offer sufficient freedom for selecting and shifting the notch bands. Impedance bandwidth, gain and radiation characteristics of them are studied and discussed here. A prototype and proposed antenna is designed, fabricated, and tested. The simulated and measured results of the proposed antenna have reasonable agreement between them. Proposed antenna has acceptable performances in terms of bandwidth, radiation pattern, gain, efficiency, phase, and group delay. Hence the proposed antenna may be suitable for UWB applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:434–443, 2014