Quarter-wavelength Transmission Line Research Articles

A compact and reconfigurable C-band DGS-based power divider using RF MEMS capacitive switch

This article presents a reconfigurable and compact power divider design that utilizes a combination of defect structures in the ground plane (DGS) and capacitance loading using a unique RF MEMS switch on the sapphire substrate. The combination of these two techniques results in a reduced-size reconfigurable power divider, wherein the length of the quarter-wavelength transmission line is reduced to λ/16 from λ/4, and the higher-order harmonics are suppressed up to 40 GHz. The RF MEMS capacitive switch is designed, and its DC characteristics are simulated in coventorware. The RF characteristics of the designed power divider are simulated in Ansys HFSS 19.2. The power divider utilizing RF MEMS technology has been fabricated through surface micromachining, requiring only four masks for fabrication. According to measurement findings, insertion loss and return loss are 3.57 dB and 24.6 dB (at 4.4 GHz) and 3.82 dB and 22.06 dB (at 5.4 GHz) when the switch is on and off, respectively. The total area of the design is 3.1 mm2 (21.3% of the conventional power divider). The proposed design can suppress harmonics up to the 8th order by 10 dB. These features render it a viable option for employment in Radio Frequency Integrated Circuits (RFICs).

Ka-Band Miniaturized 90 nm Complementary Metal Oxide Semiconductor Wideband Rat-Race Coupler Using Left-Handed and Right-Handed Transmission Lines

The traditional rat-race coupler comprises a quarter-wavelength transmission line and a three-quarter-wavelength transmission line. In this design, the slow-wave structure transmission line is employed to replace the conventional quarter-wavelength transmission line, and the three-quarter-wavelength transmission line is substituted with the left-handed transmission line. By using the TSMC CMOS 90 nm fabrication process, a circuit is created with a chip size of 300 μm × 200 μm, corresponding to the electrical size at 39 GHz of 0.039λ0 × 0.026λ0. The measured results demonstrate that the operating bandwidth is 35 to 43 GHz, with an amplitude imbalance of around 0 dB, a phase error within 1°, a return loss of less than 26 dB, and an isolation better than 40 dB.

Analysis and Design of Dual-Polarized Millimeter-Wave Filtering Magneto-Electric Dipole Antenna

A wideband dual-polarized millimeter-wave filtering magneto-electric dipole (ME-dipole) antenna design is proposed based on a transmission line model with multiple open-circuited loads. Based on the transmission line theory, the input impedance of a quarter-wavelength open-circuited transmission line is zero. Thus, a transmission line terminated with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> open-circuited loads has <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> transmission zeros. Inspired by this conclusion, the proposed antenna structure is developed which consists of three parts: the microtrip feedlines, the ME-dipole radiator and a printed branch structure. The former three parts can be regarded as three open-circuited loads of an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -stub-loaded transmission line model while the last part is utilized for bandwidth improvement. By optimizing the length parameters of these three parts, three antenna radiation nulls can be generated as predicted. For verification, a dual-polarized antenna is implemented. Measurement results show that the proposed antenna has an operation bandwidth of 42.1% and an average realized gain of 7.5 dBi. In addition, it has three controllable radiation nulls and a better than 16 dB out-of-band suppression level. Above features make the proposed antenna a good candidate for 5G millimeter-wave (mm-wave) applications.

Design of N-Way Wilkinson Power Dividers with New Input/Output Arrangements for Power-Halving Operations

In this paper, new single/double-layer N-way Wilkinson power dividers (WPDs) were designed by using slow-wave structures such as narrow-slit-loaded and meandered transmission lines. For size reduction, the slit-loaded and meandered lines were used instead of the quarter-wavelength transmission lines of a conventional WPD. Based on the proposed approaches, two-, four-, and eight-way power dividers were designed, simulated, and fabricated. The fabricated 2-, 4-, and 8-way circuits were measured at the center frequencies of 2.03, 1.77, and 1.73 GHz, which are in excellent agreement with the predicted ones. The meandered transmission lines were also used to design WPD types with novel input/output port arrangements. For this purpose, two three-way WPDs were located on both sides of the same board to have different power-splitting ratios at different inputs and outputs in order to provide alternative solutions for antenna arrays. Furthermore, a five-way dual-layer WPD was introduced by locating the meandered transmission lines into two layers. The most important advantage of the proposed 3- and 5-way WPDs is that they allowed the input power at the next output port to be halved, in the order of P/2, P/4, P/8, P/16, and P/16. All the designed power-halving WPDs were simulated, fabricated, and successfully tested.

Coplanar Stripline Single Pole Single Throw Switch

Coplanar stripline (CPS) series-connected spurline resonators are terminated with diodes, which can have a voltage applied to them, creating either a short circuit or open circuit. By connecting two spurline resonators in series separated by a quarter-wavelength transmission line, and when the diodes are reverse biased, the total circuit passes the RF power unimpeded. When the diodes are forward-biased, the circuit is a bandstop filter. This creates a CPS RF series switch with an insertion loss of 0.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 0.1 dB, a reflection coefficient of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 30 dB, and an isolation of 20 dB. The switch was simulated, fabricated, and measured for both single-element and two-element configurations.

Filtenna-Filter-Filtenna-Based FSS With Simultaneous Wide Passband and Wide Out-of-Band Rejection Using Multiple-Mode Resonators

A novel Filtenna-Filter-Filtenna (FA-F-FA)-based frequency selective surface (FSS) technique is proposed using multiple-mode resonators (MMRs). Based on this method, a bandpass FSS with simultaneous wide passband and wide out-of-band rejection is validated. The MMR unit cell consists of two back-to-back magneto-electric (ME-) dipole antennas and a filter-embedded GND plane. Four modes are analyzed and used to acquire a wide passband of the FSS. At the same time, wide out-of-band rejections in both lower and upper bands are controlled by the filter-embedded GND plane with four rotationally symmetric quarter-wavelength transmission lines (QWTLs). Moreover, the GND plane plays a crucial role in the impedance matching of the proposed FSS. As a result, four transmission poles (TPs) and three transmission zeros (TZs) of the proposed FSS can be obtained, leading to a fourth-order filtering response and wide out-of-band rejection. An equivalent circuit model, current distributions, and electric field distributions are introduced to illustrate the working mechanism of the FSS. Finally, the proposed FA-F-FA-based FSS with a 50.2% 3-dB fractional bandwidth ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FBW</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3dB</sub> ) in the passband, 53.5% and 119.2% of the 20-dB fractional bandwidth ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FBW</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20dB</sub> ) respectively in the lower and upper rejection bands is achieved. The S-parameters are stable under an oblique incident angle of 50 degrees. The measured and simulated results are in good agreement. In addition, the proposed FSS has the advantages of low profile, assembly free, and dual-polarization application, which verify the versatility of the FA-F-FA-based MMR FSS.

Analytical expressions for the design of twin junction tuning in SIS mixers

We derive general analytical expressions for matching the complex impedance of the feeding radio frequency (RF) circuit to a twin junction device in Superconductor-Insulator-Superconductor (SIS) mixers. A unique feature of our analysis is that it allows for junctions of different admittance and an RF circuit with complex admittance. This provides important design flexibility and accommodates device fabrication tolerances. We then focus on special cases of identical junctions, in particular those cases that yield simple expressions for matching the twin junction to a real impedance. Finally, we derive design curves that allow the determination of the twin junction parameters for a given complex impedance of the feeding circuit. These curves allow the designer to choose different solutions than the commonly used quarter-wavelength transmission line separating the two SIS junctions, which our analysis shows is not always the optimal solution. Moreover, even when commercial software is used for designing the circuits, our analytical equations will act as an important guide to understanding the physics and guide the designer to the optimal solution.

Orthogonal Adjacent-Order Filtering Element-Based Wideband Transmissive Linear-to-Circular Polarization Converter

This article proposes a unified design method for a highly efficient wideband transmissive linear-to-circular polarization converter composed of two orthogonal adjacent-order bandpass filtering elements for the first time. First, the linear-to-circular polarization converter is constructed to convert two orthogonal linearly polarized (LP) spatial waves split from a 45°-slant incident plane wave into a desired circularly polarized (CP) wave. Taking advantage of the wideband filter synthesis method and phase shifter theory, polarization converter elements with prescribed specifications [e.g., fractional bandwidth (FBW) and Chebyshev passband ripple] are then synthesized by the corresponding low-characteristic-impedance bandpass filtering networks with the loading of shunt short-circuited stubs on quarter-wavelength transmission line (TL) sections. The adjacent-order phase difference function with a natural ±90° value at a center frequency can be simultaneously manipulated by a filtering bandwidth. The theoretical axial ratio (AR) curve is calculated by the synthesized magnitude responses and phase deviation (PD) function. The design guideline is then summarized. Finally, based on the third- and fourth-order bandpass filtering networks, a prototype of the proposed linear-to-circular polarization converter operating at 5 GHz with a designable 70% 3 dB AR bandwidth is implemented, fabricated, and tested by the free-space measurement method. The transmitted CP wave with three in-band AR minima and relatively stable angular performances can be efficiently converted from the incident LP spatial wave as well verified in the experiment. The AR curves and design requirements of different adjacent-order bandpass filtering combinations are further explored according to the proposed design guideline.

Compact, High Power Capacity, and Low Insertion Loss Millimeter-Wave On-Chip Limiting Filter With GaAs PIN Technology

In this paper, a collaborative design of compact, high-power capacity, and low insertion loss millimeter-wave limiting filter using gallium arsenide (GaAs) PIN technology is presented. Parallel topology is employed to distribute the PIN diodes of the first stage of limiting circuit for high power handling capacity. In order to reduce the circuit size, the filtering function structure is incorporated into the limiter. Four transmission zeros (TZs) are introduced to improve the out-of-band suppression performances of the limiting filter. By utilizing the inductive short-circuited stub, a parallel resonator is introduced to exhibit the passband characteristic. Semi-lumped and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> -type topologies are employed to reduce the size of the conventional quarter-wavelength transmission line and introduce several TZs within the stopband. An on-chip limiting filter sample is fabricated by the GaAs PIN process and occupies an area of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.1\times 0.9$ </tex-math></inline-formula> mm2. It is measured with the insertion loss of 1.67 dB at the center frequency of 35 GHz, the stopband suppression of better than 20 dB, and the tolerable input power of greater than 40 dBm. Compared with the traditional designs, good features of high-power capacity, low insertion loss, and miniaturization are obtained with the presented on-chip limiting filter.

Design of dual-band Wilkinson power divider based on novel stubs using PSO algorithm

AbstractIn this paper, a new dual-band Wilkinson power divider (WPD) is designed and fabricated using novel low and high impedance stubs instead of quarter-wavelength transmission lines. The proposed circuit was analyzed using odd and even mode analysis, and the optimal values of design parameters were obtained using the particle swarm optimization algorithm. The designed power divider has input reflection coefficients (S11) of −22.1 and −17 dB at the first operating frequency of 2.2 GHz and the second operating frequency of 14.2 GHz, respectively. It also improves stop-band and fractional bandwidth (FBW) while maintaining a simple topology. The proposed WPD suppresses undesired harmonics from the second to the fifth with an attenuation level of less than −20 dB in the first band and generates a broad stop-band (4.4–11.5 GHz). In the first band, the FBW is 54.5%, and in the second band, it is 20.1%.

A 12.4–32 GHz CMOS Down-Conversion Mixer for 28 GHz 5G New Radio (NR)

We report a low voltage (VDD) and power (PDC) 12.4–32 GHz CMOS down-conversion mixer with high conversion gain (CG) for 28 GHz 5G communications. A quarter-wavelength (λ/4) transmission line (TL) and a coupling capacitor (Cc), named the λ/4-TL-C-based coupler, is proposed. This is the way to attain low-VDD, independent RF transconductance (gm)-stage bias, harmonic suppression, and near perfect coupling from the RF gm stage to the LO switch transistors. The body-self-forward-bias (BSFB) technique, i.e., connection of the gm-stage transistors’ body to drain via a large body resistance, is used for threshold voltage (Vth) and VDD reduction and substrate leakage suppression. CG and noise figure (NF) enhancement at the same or even a lower PDC is achieved because lower VDD and higher gm (due to larger bias current) are used. To facilitate the RF measurement, a compact Wilkinson-power-divider-based balun with small-phase deviation and amplitude imbalance is included at RF and LO inputs. The mixer consumes 6.5 mW and achieves a CG of 14.4 ± 1.5 dB for 12.4–32 GHz (i.e., 3 dB bandwidth (f3dB) of 19.6 GHz), a lowest noise figure (NFmin) of 7 dB, and figure-of-merit (FOM) of 0.023, which is one of the best results ever reported for millimeter-wave (mm-wave) down-conversion mixers with an f3dB larger than 10 GHz and PDC lower than 10 mW.

Broadband Doherty Power Amplifier Using Short Ended λ/4 Transmission Lines Based on the Analysis of Negative Characteristic Impedance

This paper presents a broadband Doherty power amplifier (DPA) using quarter-wavelength ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4) transmission lines with negative characteristic impedance. In conventional DPA designs, the load modulation network is frequency-dependent, leading to bandwidth limitation at the back-off power region. In this design, by integrating two <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4 transmission lines with negative characteristic impedance into the main and auxiliary branches, the impedance at the back-off power can be manipulated to maintain high efficiency at back-off power over a wide frequency range. Thus, the operational bandwidth is extended. In circuit realization, the two negative characteristic impedance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4 transmission lines are replaced by paralleled negative LC components. Then, the negative capacitor is combined into the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> -shaped impedance matching network, while the negative inductor is eliminated by introducing Norton transformation. For verification, a broadband DPA with a fractional bandwidth of 108.6% from 0.8 to 2.7 GHz is implemented. The measured saturated output power is 41.8-44 dBm. The saturated and 6-dB back-off power drain efficiencies are 47.6%-84.4% and 39.5%- 52%, respectively. A 20-MHz LTE modulated signal with peak-to- average power ratio (PAPR) of 7.5 dB is also applied to measure the fabricated DPA. After digital predistortion, the adjacent channel leakage ratio (ACLR) better than −45.35 dBc is achieved, and the measured average efficiency is higher than 40% within the operating band.

A Self-Packaged SISL Low-Power Rectifier Based on a High-Impedance Line for C-Band Applications

In this letter, a self-packaged substrate-integrated suspended line (SISL) rectifier is proposed. The rectifier consists of a quarter-wavelength high-impedance transmission line, a diode, a tuning inductor, and a dc pass filter. The lower the power is, the lower the rectifying efficiency is. At a low input power level, the diode impedance real part is almost zero. A tuning inductor is introduced to form a parallel resonator to enhance the diode voltage. A quarter-wavelength high-impedance line is presented to match the rectifying diode to the source. In addition, due to the self-packaging characteristics and air cavity of SISLs, the radiation loss and dielectric loss of the proposed rectifier are reduced. A rectifier was designed, fabricated, and measured at 5.8 GHz. The radio frequency (RF)-dc conversion efficiency reaches 3.5% at −30 dBm, which is close to its theoretical estimated efficiency at 5.8 GHz. This ultralow power rectifier may be used in energy harvesting at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -band.

Area-Efficient 28-GHz Four-Element Phased-Array Transceiver Front-End Achieving 25.2% Tx Efficiency at 15.68-dBm Output Power

An area-efficient 28-GHz four-element phased-array transceiver front-end (TRx FE) is proposed in this article. Transmitter/receiver (T/R) switch, phase shifter (PS), and power combining/splitting network all use customized coupler-based structures to replace area-consuming quarter-wavelength ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4) transmission line (T-line) structures. In Tx mode, a three-stage power amplifier (PA) is designed by cascading a class-AB predriver amplifier, a deep class-AB driver amplifier, and a class-A output amplifier for high output power. In Rx mode, a two-stage low noise amplifier (LNA) is designed with a 3-bit resistive adjusting load for high dynamic range of input power. A coupler is adopted in the variable gain amplifier (VGA) to achieve constant phase during gain adjustment. The proposed TRx FE is fabricated in a 40-nm CMOS process. Measurement results show that output 1-dB compression point (OP1dB) of 14.99 dBm and saturated output power (OPsat) of 15.68 dBm with 25.2% power efficiency are achieved in each Tx element. In each Rx element, noise figure (NF) of 4.54 dB, input 1-dB compression point (IP1dB) of −10.15 dBm, and maximum gain of 26.3 dB with 56.1-mW power consumption are realized. The gain range of Rx/Tx mode is 9.9–26.3 dB/24.2–44.6 dB with a resolution of 0.3 dB and phase variation less than 2° at 28 GHz. Thanks to the area-efficient coupler-based structures, the phased-array TRx FE occupies an area of 0.42 mm2 for each element and 0.084 mm2 for total area of combiner/splitter, achieving high area efficiency for Ka-band phased-array TRx FEs.

A Dual-Band Branch-Line Coupler with Ultra-Wideband Harmonic Suppression

A dual-band branch-line coupler with ultra-wideband harmonic suppression is proposed in this paper. The conventional quarter-wavelength transmission lines are replaced with π-shaped lines to achieve a dual band. In addition, ultra-wideband harmonic suppression is obtained by the frequency-selecting coupling structure (FSCS) providing three transmission zeros. The two operating frequencies are 0.9 GHz and 2.0 GHz, and the corresponding -10 dB bandwidth at 0.9 GHz and 2.0 GHz is 18.9% and 10.5%, respectively. A wide harmonic suppression band is generated from 3.7 GHz to 8.3 GHz. The simulation and measurement results are in good agreement.

Designing ultra-small Wilkinson power divider with multi-harmonics suppression

ABSTRACT This paper presents a miniaturized Wilkinson Power Divider (WPD) with the capability of attenuating unwanted harmonics up to the 19th harmonic. In this study, a low pass filter was embedded as the quarter-wavelength transmission lines of the conventional WPD. To reduce the size of the proposed structure, the high impedance line is meandered. A simple T-shape resonator is added to suppress the high frequency. The even and odd mode analysis were reported as the analytical descriptions. The operational frequency of the presented WPD is 1.95GHz, and S21, S11, S22, and S23 in this frequency are -3.79dB, -15.56dB, -14.15dB, and -10.89dB, respectively. The overall size of implemented WPD is only 8.8 mm × 8.02 mm, and its normalized circuit size equals 0.078 × 0.071. The designed structure has been fabricated and measured on the RT-5880 substrate with a thickness of 20mil. The desired matching between the simulation results and the measurement ones has been evident.

A Novel Filtering Power Divider Based on Ring Resonator

In this paper, a compact dual-band filtering power divider (FPD) combined by conventional Wilkinson power divider and dual-mode resonators is proposed. The resonators submitting the quarter wavelength transmission line can act as a filter. The proposed resonator is composed of two cascading symmetrical ring branches connected to the ground in the middle. The inter-digital coupling structure constitutes the feed lines of the band-pass filter (BPF) operating at 2.45/5.8 G. The resonator with symmetrical structure is analyzed by the odd-even mode method in detail. The two resonant frequencies can be adjusted by the length of the stub separately. In addition, two isolation resistors are placed at proper position for ensuring the isolation effect. The proposed FPD is fabricated for verifying simulation results, and good agreements between the simulated and measured results are achieved here.

A compact mesoband microwave radiation system.

A compact mesoband radiation system is designed and tested. The system is composed of a charging power supply, a Marx generator, a switched quarter-wavelength oscillator, and a circularly polarized patch antenna. The Marx generator outputs a fast high-voltage pulse with a rise time of 10ns and an amplitude of 100kV, which is used to charge the oscillator. The oscillator consists of a quarter-wavelength coaxial transmission line, a ring ground switch, and a coupler. It generates a mesoband oscillation pulse with a center frequency of 350MHz and a percentage bandwidth of 10%. The oscillation pulse is radiated by the circularly polarized patch antenna. The measured radiation factor is greater than 50kV, and the radiation waveform is consistent with the simulation waveform.

A miniaturized dual-band bandpass filter with sharp roll-off rate using coupled lines and dual transmission lines

This paper presents a compact, high roll-off rate second-order dual-band bandpass filter with seven transmission zeros. The proposed filter design constructs of dual transmission lines, coupled lines, stepped impedance open stubs, and quarter-wavelength transmission lines. The proposed filter has a size of 0.31λg × 0.24λg and is printed on RT/duroid 5880 substrate to operate at two different frequencies (1.16 GHz and 2.71 GHz). The proposed filter is fabricated and measured, and good input matching is obtained at desired frequencies. Excellent isolation is achieved between two passbands due to the stopband effect created by the dual transmission lines. The simulated and tested frequency responses are in high agreement with each other.

A dualband bandpass filter with tunable bandwidths for automotive radar and 5G millimeter-wave applications

A compact dual wideband bandpass filter for automotive radar (AR) and 5G millimeter-wave (mmWave) applications with adjustable bandwidths is presented in this work. The filter is based on microstrip dual-mode edge-coupled stub-loaded resonators (SLR). The novelty of this configuration is that it allows independent control of the bandwidths which is not obvious for many reported SLR-based filters. To achieve an overall size of 1.23λ_g× 2.02λ_g, these resonators are coupled and bent int o U-shape, T-shape, and E-shape. The U-shaped resonator, based on a quarter-wavelength transmission line, is coupled to the T-shaped element which constitutes the main feed line to obtain the dual-band response. Having a symmetrical structure, the design i s studied using the even-odd mode analysis. The layout is made using the Ansys high-frequency structural simulator (HFSS) and fabricated on Rogers RO3010 with a thickness of 1.28 mm, a dielectric constant of 10.2, and a loss tangent of 0.0022. The measured bandwidths are 660 MHz and 880 MHz at central frequencies of 23.92 GHz and 28.38 GHz respectively. The measured insertion losses are less than 3.9 dB and the return losses are greater than 17 dB in both bands. A good agreement is obtained between simulate d and experimental results.