Quarter-wavelength Transmission Line Research Articles

NOVEL TRI-BAND BANDPASS FILTER WITH HIGH SELECTIVITY

This paper presents a tri-band bandpass filter (BPF) consisting of a wide BPF and two narrow bandstop filters (BSFs). BPF is a ninth-order interdigital structure, and BSFs are designed fifth- order series resonators with quarter wavelength transmission line connected. The selectivity of BPF and the bandwidth of BSF are analyzed using simulation software. A tri-band BPF, made of metal cavities, is designed and measured. Three passbands are located in 1.332∼1.401 GHz, 1.443∼1.458 GHz, 1.506∼1.660 GHz, and insertion losses in passbands are less than 2.1 dB. Ratios of Δf40dB/Δf3dB are 1.9, 2.67 and 1.33, respectively, and isolation between passbands is more than 75 dB. The good agreement between the simulated and measured results validated the proposed structure.

A dual‐band branch line coupler based on Pi‐shaped coupled lines

ABSTRACTThis article presents a coupler using Pi‐shaped coupled lines for dual‐band operations. In this design, two open circuited stubs are tapped at both ends of a coupled line structure to realize the 90° phase changes at two frequencies. The designed structure is used in place of a conventional quarter wavelength transmission line for dual‐band application. For verification, a 3‐dB branch line coupler with operating frequencies of 0.95 and 1.52 GHz is designed. The simulated and measured results are in good agreement with each other. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:501–504, 2015

Miniaturized Rat-Race Coupler With Harmonic Suppression

In this letter, a miniaturized rat-race coupler with harmonic suppression is proposed. The quarter-wavelength transmission lines in a traditional rat-race coupler are substituted by their equivalent stub-loaded transmission lines. As a result, the overall size is significantly reduced while maintaining the coupler performance. Furthermore, one transmission zero is introduced by the stubs to suppress the harmonics. Finally, a miniaturized rat-race coupler with harmonic suppression is designed, fabricated and measured, and the measurement verifies the theoretical and simulation analysis.

Design of an ultra-wideband power divider with harmonics suppression

The design of an ultrawideband (UWB) power divider with harmonics suppression is presented. With the proposed approach, the size of the quarter-wavelength transmission line can be reduced and the high order harmonics can be suppressed. The design equations are deduced by transmission line theory. A prototype power divider operated at UWB band is designed and fabricated. Experimental results show good performance of the proposed design. In addition, a stop-band with rejection level more than 20 dB is from 17.3 to 24.5 GHz. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:299–304, 2015.

COMPACT WILKINSON PASS-BAND FILTERING POWER DIVIDER BASED ON QUARTER-WAVELENGTH SIDE-COUPLED RING

A Wilkinson power divider with improved bandpass filtering and high isolation performance is proposed. These characteristics are achieved by replacing the quarter-wavelength transmission line in the conventional coupled line Wilkinson power divider with quarter-wavelength side-coupled ring (QSCR). Additional features such as DC blocking between arbitrary two ports, single-layer via-less structure for low-cost fabrication and convenient integration (as only one isolation resistor required) are highlighted. A 2-GHz Wilkinson microstrip power divider with a fractional bandwidth of 4% has been fabricated and experimentally characterized. The consistency between simulated and measured results validates the effectiveness of our proposed design.

14–30 GHz low‐power sub‐harmonic single‐balanced gate‐pumped mixer with transformer combiner in 0.18 μm CMOS

A 14-30 GHz sub-harmonic single-balanced gate-pumped mixer with a wideband transformer combiner in 0.18 μm CMOS technology is presented. The transistors of the sub-harmonic mixer core are biased at weak inversion to lower the required local oscillator (LO) driving power and DC power consumption. The wideband combiner including a Marchand balun and a 1:1:1 trifilar transformer was designed to combine the radio frequency (RF) and LO driving signals to produce four states of signals, where the RF frequency is about twice the LO frequency. Two quarter-wavelength transmission lines are adopted to improve the RF-to-intermediate-frequency (IF) and 2LO-to-IF isolations. The measured results show that the maximum conversion gain of -1 dB is at 18 GHz and a 3 dB bandwidth is from 14 to 30 GHz while applying the LO driving power of only 1 dBm. The total power consumption including the output buffer is only 7.8 mW.

Millimeter-Wave Reduced-Size Wilkinson Power Divider

The letter reports the analysis of the reduced-size planar microstrip Wilkinson power divider which uses miniaturized microstrip line instead of conventional quarter wavelength transmission line. The full design formulae of the miniaturized Wilkinson power divider with arbitrary power ratio is first proposed.3dB one-stage and two-stage miniaturized Wilkinson power divider are designed according to the formulae. The ADS EM simulation results of the one-stage miniaturized Wilkinson power divider when the smaller electrical angle is 45 degrees show its reflection coefficient<-20dB,isolation>20dB and the transmission loss<0.4dB in the bandwidth of 28.9-34.9GHz,for the two-stage reduced-size Wilkinson power divider its reflection coefficient <-20dB,isolation>20dB and the transmission loss<0.4dB in the bandwidth of 26-37.5GHz.This kind of miniaturized Wilkinson power divider has a very compact size as well as good match and isolation.

CMOS Doherty Amplifier With Variable Balun Transformer and Adaptive Bias Control for Wireless LAN Application

This paper presents a novel CMOS Doherty power amplifier (PA) with an impedance inverter using a variable balun transformer (VBT) and adaptive bias control of an auxiliary amplifier. Unlike a conventional quarter-wavelength (λ/4) transmission line impedance inverter of a Doherty PA, the proposed VBT impedance inverter can achieve load modulation without any phase delay circuit. As a result, a λ/4 phase compensation circuit at the input path of the auxiliary amplifier can be removed, and the total size of the Doherty PA can be reduced. Additionally, an enhancement of the power efficiency at backed-off power levels can successfully be achieved with an adaptive gate bias in a common gate stage of the auxiliary amplifier. The PA, fabricated with 0.13-μm CMOS technology, achieved a 1-dB compression point (P1 dB) of 31.9 dBm and a power-added efficiency (PAE) at P1 dB of 51%. When the PA is tested with 802.11g WLAN orthogonal frequency division multiplexing (OFDM) signal of 54 Mb/s, a 25-dB error vector magnitude (EVM) compliant output power of 22.8 dBm and a PAE of 30.1% are obtained, respectively.

Wideband Microstrip 90° Hybrid Coupler Using High Pass Network

A wideband 90° hybrid coupler has been presented and implemented in planar microstrip circuit. With similar structure of conversional 2-section branch-line coupler, the proposed coupler consists of a lumped high-pass network but not the quarter wavelength transmission at the center. The values of all lumped elements were optimized to replace a quarter-wavelength transmission line with a phase inverter. To demonstrate the proposed concept, a 1-GHz prototype was fabricated and tested. It achieves 90% impedance bandwidth with magnitude of S11 less than −10 dB. Within this bandwidth, more than 13 dB port-to-port isolation, less than 5.0 degree phase imbalance, and less than 4.5 dB magnitude imbalance are achieved, simultaneously. The proposed coupler not only achieves much wider bandwidth but also occupies less circuit area than that of the conversional 2-section branch-line coupler.

DESIGN OF A COMPACT WILKINSON POWER DIVIDER WITH HIGH ORDER HARMONICS SUPPRESSION

A new method for designing compact Wilkinson power dividers with three order harmonics suppression is presented. The quarter-wavelength transmission line in the traditional Wilkinson power divider is replaced by two pairs of parallel coupled lines with one end connected in series with an open stub. With this structure, the quarter-wavelength line will be shorter and three attenuation poles can be added in the stopband. As a result, this newly proposed structure carries the functions of impedance matching at operating frequency and three orders harmonics suppression. In this study, an example of power divider operating at 1 GHz is designed and fabricated. The measured results show good performance at the operating frequency. In addition, the second, third and fourth harmonics suppressions are 43 dB, 49 dB and 37 dB, respectively, which validates the feasibility of the proposed design.

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.

A New Design of Equal and Unequal Dual-Band Gysel Power Divider with Controllable Bandwidth

In this article, a new design for an equal and unequal dual-band Gysel power divider with a novel dual-band transformer has been proposed. This transformer is replaced with two conventional quarter-wavelength transmission lines between the isolation resistors. The proposed power divider thus has controllable bandwidth, exactly the same as the conventional Gysel power divider, as well as simple structure, wide frequency band ratio, good isolation and return loss, and high-power handling capability advantages over the Wilkinson power divider.

Solar cell stacked dual‐polarised patch antenna for 5.8 GHz band WiMAX network

A novel combination of a two-port slant +/- 45 degrees dual-polarised microstrip patch antenna with a polycrystalline silicon (poly-Si) solar cell operating as an RF stacked parasitic patch element is presented and discussed for 5.8 GHz band polarisation diverse multifunctional WiMAX systems. To minimise the effect of the solar operation on the RF antenna performance, an effective DC/RF isolation circuit consisting of quarter-wavelength microstrip transmission lines is demonstrated. The proposed solar patch provides identical E-plane and H-plane far-field radiation patterns for +45 degrees and -45 degrees polarisations with a gain of 7.8 dBi and operates at the frequency band of 5.66-5.91 GHz.

Analytical Derivation of T-Shaped Structures for Synthesis of Quarter-Wavelength Transmission Lines

T-shaped structures, proposed to synthesize the quarter-wavelength transmission lines, have proved efficient for circuit miniaturization. While the design equations for the symmetric case are published, the existing equations for asymmetric cases, as reported recently, could lead to frequency-shift problems. In this letter, we analytically study the T-shaped structures and present closed-form design equations for synthesis of quarter-wavelength transmission lines. The equations explicitly show that quarter-wavelength transmission lines synthesized with asymmetric T-shaped structures cannot be perfectly matched to the reference impedance. The design of couplers with asymmetric T-shaped structures can be regarded as exploiting reflection cancellations to attain the matched condition at each port, as indicated by the equations. The closed-form equations are clear and concise enough for facilitating the design and application of T-shaped structures.

Active Millimeter-Wave Phase-Shift Doherty Power Amplifier in 45-nm SOI CMOS

A 45 GHz active phase-shift Doherty PA is proposed and implemented in 45-nm SOI CMOS. The quarter wave-length transmission line at the input of the auxiliary amplifier is replaced by an amplifier, increasing the gain and PAE by more than 1 dB and 5%, while reducing the die area. Use of slow-wave coplanar waveguides (S-CPW) improves the PAE and gain by approximately 3% and 1 dB, and further reduces the die area. Two-stack FET amplifiers are used as the main and auxiliary amplifiers, allowing a supply voltage of 2.5 V and increasing the output power. The active phase-shift Doherty amplifier demonstrates a peak power gain and PAE of 8 dB and 20% at 45 GHz. It occupies 0.45 mm2, and at 6-dB back-off power, the PAE is 21%.

Design and Analysis of the Millimeter-Wave SPDT Switch for TDD Applications

This paper presents a low-loss and high Tx-to-Rx isolation single-pole double-throw (SPDT) millimeter-wave switch for true time delay applications. The switch is designed based on matching-network and double-shunt transistors with quarter-wavelength transmission lines. The insertion loss and isolation characteristics of the switches are analyzed revealing that optimization of the transistor size with a matching-network switch on the receiver side and a double-shunt switch on the transmitter side can enhance the isolation performance with low loss. Implemented in 90-nm CMOS, the switch achieves a measured insertion loss and Tx-to-Rx isolation of 1.9 and 39 dB at 60 GHz, respectively. The input 1-dB gain compression point is 10 dBm at 60 GHz, and the return loss of the SPDT switch ports is greater than 10 dB at 48-67 GHz.

Experimental demonstrations of high-Q superconducting coplanar waveguide resonators

We successfully designed and fabricated an absorption-type of superconducting coplanar waveguide (CPW) resonators. The resonators are made from a niobium film (about 160 nm thick) on a high-resistance Si substrate, and each resonator is fabricated as a meandered quarter-wavelength transmission line (one end is short to the ground and another end is capacitively coupled to a through feedline). With a vector network analyzer we measured the transmissions of the applied microwave through the resonators at ultra-low temperature. The obtained loaded quality factors are significantly high, i.e. up to ∼106. When the temperature increases slowly from the base temperature (20 mK), the resonance frequencies of the resonators are blue shifted and the quality factors are lowered slightly. In principle, this type of device can integrate a series of CPW resonators with a common feedline, making it a promising candidate as the data bus for coupling distant solid-state qubits and the sensitive detector of single photons.

Miniature Butler Matrix Design Using Glass-Based Thin-Film Integrated Passive Device Technology for 2.5-GHz Applications

In this paper, miniature branch-line coupler and Butler matrix designs for 2.5-GHz applications are proposed using the glass-based thin-film integrated passive device (TF-IPD) technology. The size reduction is achieved by replacing the quarter-wavelength transmission lines in a conventional branch-line coupler with the bridged-T coil. In this way, the circuit size can be largely reduced without sacrificing the operation bandwidth. The proposed miniature branch-line coupler is then applied to the design of a 4 × 4 Butler matrix centered at 2.5 GHz using the glass-based TF-IPD technology. The measured results show a bandwidth of 2.4-2.6 GHz for better than 13-dB return loss with a maximal dissipation of 4 dB, amplitude imbalance within 1.1 dB, and phase imbalance less than 13°. Notably, the proposed Butler matrix occupies a chip area of 3.13 mm × 3.3 mm, which is only about 0.026 λ0 × 0.027 λ0 at 2.5 GHz.

Millimeter-wave coplanar stripline power dividers

We present the design, fabrication, and measurement of a 2-way modified Wilkinson divider constructed in a coplanar geometry exhibiting ultra wideband isolation, transmission, and port matching in the millimeter-wave frequency range. The proposed divider replaces the lumped resistor in the conventional Wilkinson divider with two quarter-wave length transmission lines, a phase inverter, and two 2Z0 resistors. Except for the three ports that are coplanar waveguides (CPWs), the main body of the divider uses coplanar striplines (CPS). The phase inverter is realized using a simple airbridge-based crossover which is compatible with a modern monolithic microwave integrated circuit process. The divider has a ring-like configuration fabricated on a 620 µm thick semi-insulating GaAs wafer using electron beam lithography (EBL) technology. Three-dimensional (3D) full-wave electromagnetic simulations have been carried out to optimize the design and investigate the possible effect of fabrication tolerance on the performance of the crossover and the divider. Two dividers working at center frequencies of 25 and 80 GHz have been designed, fabricated, and tested. They all show consistent performance in terms of bandwidth, isolation, and port matching. Experimental and simulation results are in excellent agreement.

A novel miniaturized Wilkinson power divider with nth harmonic suppression

In this paper, a miniaturized Wilkinson power divider using a novel technique for nth harmonic suppression is presented. In this technique, a novel low-pass filter (LPF) is inserted into each quarter-wavelength transmission line of the conventional Wilkinson power divider and open stubs are used at each port. For verification, the proposed 1 GHz power divider and the miniaturized LPF are fabricated and measured. The presented structure not only impressively suppresses the harmonics (2nd–12th) with high levels of attenuation, but also significantly reduces the size over 71% of the conventional one. The overall size of the fabricated power divider is only 14.1 mm × 18.2 mm (0.06 λg × 0.08λg).