Quarter-wave Transmission Line Research Articles

Built-In Coil Current Sensing for 7-Tesla 1H/23Na and 1H/31P Magnetic Resonance Imaging

This article introduces two designs for dual-tuned built-in radio-frequency coil current sensing in 7-Tesla magnetic resonance imaging based on the current forcing property of the quarter-wave transmission line. The first design offers dual-tuned built-in coil current sensing at <sup>1</sup>H/<sup>23</sup>Na resonant frequencies to probe the coil current consecutively at 298 MHz and 78.8 MHz, without the need for any integrated sensor on the coil. The second design enables dual-tuned built-in coil current sensing at <sup>1</sup>H/<sup>31</sup>P resonant frequencies to probe the coil current at 298 MHz and 120 MHz consecutively. The first design achieved good matching (<-40 dB) and low insertion loss (<0.5 dB) for <sup>1</sup>H and <sup>23</sup>Na magnetic resonance signals. The <sup>1</sup>H/<sup>31</sup>P design also exhibited good matching (<-30 dB) and low insertion loss (<0.67 dB). Therefore, both designs show promising potential for monitoring current flows in dual-tuned coils at the Larmor frequencies of different atomic nuclei.

A 39-GHz High Image-Rejection Up-Conversion Mixer in 65-nm CMOS for 5G Communication

This brief presents an up-conversion mixer with high image rejection ratio (IRR) for 5G mmWave communication. To achieve broadband IRR at mmWave frequency with high area efficiency, a current-mode second-order tunable notch filter embedded in a cascode radio frequency (RF) buffer is proposed to realize tracking of the pole and zero frequencies with the switch capacitor array. To address the local oscillator (LO) leakage and even-harmonic distortion, a double-balanced passive mixer is adopted. For better isolation and lower insertion loss, a capacitor-inductor-capacitor (C-L-C) <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 impedance network is introduced in the mmWave T/R switch, realizing the equivalent lumped quarter wave transmission line with high area efficiency. Fabricated in a 65-nm CMOS process, the up-conversion mixer consumes 48.6 mW from a 1.2-V supply. Within the 3-dB bandwidth from 36 to 40.6 GHz, the mixer has a peak conversion gain of 0 dB, and its measured output 1-dB gain compression point (OP1dB) varies from −3 to −1.8 dBm. With the proposed tunable notch filter, the up-conversion mixer achieves a measured IRR of more than 53 dBc from 36 to 40.6 GHz, with a peak value of 58 dBc at 38.2 GHz.

Broadband InGaP/GaAs HBT Doherty Power Amplifier IC Using Direct Interstage Power Division for Compact 5G NR Handset Module

This paper presents a 2.8-3.8 GHz broadband 2-stage fully differential Doherty power amplifier using direct interstage power division based on a 2-μmInGaP/GaAs HBT process for 5G new radio handset applications. A compact transformer-less interstage network is proposed for direct power division for carrier and peaking amplifiers. The power division ratio at the interstage is designed to dynamically vary according to the input power level to provide higher power gain and desired load impedance modulation. By utilizing the non-linear input reactance of the peaking amplifier, broadband dynamic power division circuits were designed for an operating frequency band of as broad as 1 GHz. In addition, active bias circuits for the peaking amplifier were optimized to have sufficient gain expansion, so that the overall AM-AM characteristics is as flat as possible. A broadband load modulation network using one transformer and two quarter-wave transmission lines is proposed. For the off-chip output transformer, impedance trajectory for the wide band impedance matching is presented using a T-equivalent circuit of the transformer. The self-inductance ratio of the transformer is optimized to maximize the bandwidth. Using the 5G new radio uplink signal with a signal bandwidth of 100 MHz, the implemented Doherty PA IC exhibited a power gain of 31.9 to 38.4 dB, PAE of 22.0 to 30.6%, and average output power of 26.0 to 27.8 dBm at a given ACLR of -33.0 dBc without pre-distortion.

Ultra‐miniaturised C ‐band power divider using capacitive loading and defect grounded structures

This article reports a compact Power Divider design employing a combination of a capacitive load and Defect Grounded Structures (DGS) on GaAs substrate for MMIC technology in the C band. The integration of these two techniques offers a compact power divider with a decrease in quarter-wave transmission line length from λ/4 to λ/16 and harmonic suppression up to 50 GHz. Capacitive loading reduces the size, and DGS improves harmonic suppression and further decreases the size of the structure. The designed power divider is simulated in Ansys HFSS 19.2 and provides a return loss of 25.66 dB, with an insertion loss of 3.01 dB at 5.4 GHz and isolation of 13.37 dB. Isolation is further improved to 30.89 dB using a parallel combination of resistor and capacitor in the isolation network. The prototype of the proposed circuit has been fabricated using RT/duroid® 5880 as substrate. Measurement results show insertion loss and return loss of 3.02 and 23.46 dB. Isolation of 22.43 dB was achieved. The proposed design provides a size reduction of 73.7% with harmonic suppression up to 10th harmonics by 10 dB, making it suitable for high-performance monolithic microwave integrated circuits (MMIC).

Design and Analysis of a Compact Wide-Band BPF using Quarter Wave Transmission Lines

Design and Analysis of a Compact Wide-Band BPF using Quarter Wave Transmission Lines

Analysis and design of the biasing network for 1 GHz bandwidth RF power amplifier

The bandwidth of the wireless communication has increased due to the various applications of the wireless devices. A radio frequency power amplifier (RFPA) is one of the crucial components of the transceiver. So, to meet the requirement of the bandwidth, wideband RFPA is needed. The RFPA not only requires a wideband matching network but importantly the biasing network. For the next-generation communication system, a wideband biasing network is needed to operate in the wide GHz bandwidth range. In this paper, a wideband biasing network for the power amplifier is designed using a quarter-wave transmission line and a butterfly stub for the frequency band of 3.3 GHz to 4.3 GHz. Roger’s RO3006 is used as the substrate for the design of the biasing network. The designed network performed well in the required frequency range. The performances of the biasing network have shown 9 dB to 19 dB return loss, the radio frequency (RF) isolation has more than 35 dB, and 0 dB to 1.5 dB insertion loss. This wideband biasing network can be used for the next generation communication system.

Theory and Design of a Flexible Two-Stage Wideband Wilkinson Power Divider

This article presents the design scheme of a wideband Wilkinson Power Divider (WPD) with two-stage architecture utilizing quarter-wave transmission lines and short-circuit stubs. The bandwidth of the proposed WPD is flexible and can be controlled using the design parameters. The proposed design achieves excellent isolation between output ports in addition good in-band performance. The analysis of the proposed circuit results in a simplified transfer function which is then equated with a standard band-pass transfer function to determine the parameters of transmission lines, stub’s impedances, and the value of the isolation resistors. Furthermore, it is also demonstrated that a simple alteration in the proposed circuit enables the design of a wideband DC isolated WPD that maintains a good in-band and isolation performance. A number of case studies have been included to highlight the flexibility of the proposed design. Two distinct prototypes are developed on different boards to demonstrate the wideband performance of the proposed design. An excellent agreement between the experimental and measured results for both the designs over a wide band including very good isolation between ports validate the proposed design.

A 20–36-GHz Voltage-Controlled Analog Distributed Attenuator With a Wide Attenuation Range and Low Phase Imbalance

A K-/Ka-band distributed attenuator in a 28-nm CMOS process is presented for a phased array. The proposed voltage-controlled distributed attenuator is designed using nonuniform varistors for a wide attenuation range with a compact size. An attenuation range of 25 dB was achieved with only three sections, which are 90° apart. The phase imbalance of the proposed attenuator is minimized using an artificial quarter-wave transmission line with series-connected varistors. The measured insertion loss of the proposed attenuator is 1.6-2.5 dB from 20 to 36 GHz. The insertion phase imbalance is less than 10° within the same bandwidth. The input 1-dB compression point is 10.6 dBm (defined as the 1-dB drop in the maximum attenuation range) at 28 GHz. The total chip size, including pads, is 0.77 × 0.42 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The proposed attenuator has the highest attenuation range relative to the chip area compared with previously distributed attenuators.

DESIGN AND ANALYSIS OF ULTRA WIDE BAND ELLIPTICAL SLOT WITH QUARTER WAVE TRANSMISSION LINE GROUND FOR WIRELESS APPLICATIONS

UltraWide Bandwidth (UWB) antenna with Deflected Ground Structure for wireless communication is presented in this paper. Our proposed antenna design is consisting of elliptical shape slot at patch and Quarter wave transmission line at the ground with multiband frequency operation in various wireless communications.An antenna is designed using FR4 substrate with permittivity value of 4.4 and thickness of 0.8 mm. The size of the antenna is 50 x 70 mm2presents a high gain of 4 dB with Ultra Wide Bandwidth. In proposed antenna quarter wave ground is imposed with Deflected Ground Structure to achieve overall size reduction. The ultra bandwidth antenna proposed in this paper operates at multiband frequencies centered at 3.0267 GHz, 6.1933 GHz, 9.1911 GHz, 12.1467 GHz, and 15.06 GHz with corresponding return loss of -24.0553 dB, -40.9292 dB, -20.7534 dB, -41.8718 dB, -30.1747 dB.

Design and Analysis of Dual-Band Circular Patch Antenna for X-Band Applications with Enhanced Bandwidth

An antenna is a crucial component in the wireless communication system which converts electrical waves to EM waves and vice-versa which leads to revaluation in wireless communication technology. Due to this reason the experiment was performed on a simple circular patch antenna for better radiation along with wide transmission bandwidth. In this paper, a simple circular microstrip antenna structure is designed to operate at dual bands. The proposed antenna consists of a circular radiating patch, a 50-ohm feedline line, a quarter-wave impedance matching transmission line, and a ground plane. It meets significant requirements for large bandwidth, optimized gain, minimum reflections, and small size with high directivity and efficiency. This antenna contains FR4 Epoxy substrate material with permittivity 4.4 and size 36mm x 36mm x 1.67mm. ANSOFT HFSS simulator is used to analyze various parameters like return loss, VSWR, Impedance, and gain. The Resonant Frequency of the designed antenna is 8.77 GHz and 10.6 GHz. with minimum Return Loss of -52 dB and -21.66 dB respectively. It was also observed that 1.005 and 1.2 VSWR at 8.77 GHz and 10.6 GHz respectively.

A Compact Dual-Band Out of Phase Power Divider Having Microstrip Compatibility

A compact dual-band out of phase difference power divider having microstrip transmission capability has been proposed in this brief. To realize the proposed power divider a dual-band quarter-wave transmission line (DBQWTL) with closed-form design equations have also been proposed. In order to validate the proposed approach, a power divider has been designed and implemented on a printed circuit board for 0.7GHz and 2.6GHz operating frequencies and tested. The S - parameters of the power divider have been measured at the operating frequencies with maximum ±0.26dB amplitude imbalance and ±2° phase deviation. The first time a dual-band out of phase power divider having microstrip compatibility is proposed. In addition, it has the smallest size, minimum phase deviation, design with fewer number of lumped components, and having output ports on the same plane.

Unidirectional Antenna for Disease Detection Purpose

A brain tumor is defined as a mass of tissue formed by an accumulation of abnormal cells within the brain. This paper proposes a high gain ultra-wideband (UWB) reflector array antenna for cancer detection. Introduction of the copper reflector with ideal distance contribute to increasing the proposed antenna gain. The antenna is printed with 4×1 copper radiating patch array properly connected with quarter wave transformer transmission line associated with a copper parasitic element for the front side. The patches comprise of four identical circulars with a diameter of 15 mm. Parasitic element is placed on very close to feeding line with the gap only 0.2 mm. Each quarter wave transmission line has its own specific wide dimension for 50Ω, 70.71Ω and 100Ω to ensure equal current distribution towards all four patches could be realized. Quarter-wave transformers of 70.71 Ω are used to have an ideal match between the 100 Ω lines and the 50 Ω lines. The high gain antenna is essential in a human microwave detection system for penetrating the multilayer structures by enhancing the focus of the electromagnetic energy into the desired structure. The antenna with reflector recorded wider bandwidth; 1.6 GHz-10.8 GHz associated with higher gain ranged from 3.2 dB until 14.1 dB compared with an antenna without reflector operated from 2.2 GHz to 10.8 GHz with lower gain ranges of 2.1 dB to 10.2 dB.

A neuro‐based approach to designing a Wilkinson power divider

In this paper, a new neuro-based approach using a feed-forward neural network is presented to design a Wilkinson power divider. The proposed power divider is composed of symmetrical modified T-shaped resonators, which are a replacement for quarter-wave transmission lines in the conventional structure. The proposed technique reduces the size of the power divider by 45% and suppresses unwanted bands up to the fifth harmonics. To verify the concept, a prototype of the power divider has been fabricated and tested, exhibiting good agreement between the predicted and measured results. The results show that the insertion loss and the isolation at the center frequency are about 3.3 ± 0.1 dB and 23 dB, respectively.

Hexa-Band Branch Line Coupler and Wilkinson Power Divider for LTE 0.7 GHz, LTE 1.7 GHz, LTE 2.6 GHz, 3.9 GHz, Public Safety Band 4.9 GHz, and WLAN 5.8 GHz Frequencies

A hexa-band branch line coupler (BLC) and Wilkinson power divider (WPD) for long term evolution (LTE) 0.7 GHz, LTE 1.7 GHz, LTE 2.6 GHz, 3.9 GHz, public safety band (PSB) 4.9 GHz, and wireless local area network (WLAN) 5.8 GHz frequencies have been proposed, designed, implemented, and analyzed in this brief. To realize the proposed BLC and WPD a hexa-band quarter wave transmission line (TL) with complete derivation for a hexa-band operation has been introduced. A good performance for the BLC/WPD has been achieved over all the six bands with maximum 0.42/0.21 dB amplitude imbalance and 4.81°/0.9° phase deviation. Compared to the most of the existing BLCs/WPDs, the proposed BLC/WPD has simpler design structure and, compact size than the existing hexa and quad-band BLCs/WPDs.

Compact filtering power dividers with wide upper stopband

AbstractA series of compact filtering power dividers (FPDs) with simple layouts are proposed based on coupling topology. The structure of the presented FPD1 is composed of three resonators and one isolating resistor. These FPDs can be designed based on coupling matrix filter theory. A half-wave transmission line is employed in FPD2 to introduce a transmission zero (TZ) locating at 1.27f0. The FPD3 is designed by replacing quarter-wave transmission lines in FPD2 with quarter-wave coupled lines, which will produce a TZ locating at 1.96 f0 and extend upper stopband bandwidth. For verification, three FPDs centered at 2.45 GHz are fabricated and measured. All measured results are in good agreement with the full-wave simulation results.

A dual‐band branch line coupler for LTE 0.7 GHz and LTE 2.6 GHz frequencies

In this paper, a dual-band branch line coupler (BLC) for Long Term Evolution (LTE) 0.7 GHz and LTE 2.6 GHz frequencies is designed and developed. A dual-band quarter wave transmission line (DBQWTL) capable to perform dual band operation for frequency ratio >3 is also proposed. The dual band BLC is designed by replacing the quarter wave transmission line of the conventional single band BLC with the proposed DBQWTL. By means of even and odd mode analysis, the closed form design equations of the proposed DBQWTL are obtained. Considering the implementation viewpoint of the proposed BLC, the circuit parameter analysis is carried out. The proposed BLC performs dual band operation with maximum amplitude imbalance of 0.26 dB and phase deviation of 3.07°. It is found in the comparative analysis that the proposed BLC has novelty in terms of its operating frequency ratio range.

A Dual Band Branch Line Coupler With Wide Frequency Ratio

A dual-band quadrature branch line coupler (BLC) with wide frequency ratio has been proposed in this paper. A dual-band quarter wave ( $\lambda $ /4) transmission line structure with wide frequency ratio operation has also been presented here with closed-form design equations. An analysis for the BLC’s circuit parameters variations versus frequency ratio in the view of the implementation has been carried out as well. In order to the experimental verification, a dual-band BLC has been designed, implemented, and analyzed then tested for long term evolution (LTE) 0.7GHz and public safety band (PSB) 4.9GHz. The novelty of the proposed design is the wide frequency ratio of its dual-band operation, which can reach up to 11.8.

Novel Design of Miniaturized Filtering Power Dividers Using Dual-Composite Right-/Left-Handed Resonators

One kind of miniaturized filtering power divider (FPD) with a new topology is proposed. For previously published FPDs, the isolation resistors were usually added with additional quarter-wave ( $\lambda $ /4) transmission lines for output isolation. In this paper, $\lambda $ /4 transmission lines are removed, and the resistor is added to the loaded resonator for the miniaturized design. By regarding the input external quality factor ( $Q_{e\text {-in}}$ ) as an admittance inverter, the indispensable 90° delay can be easily realized. To further improve the miniaturization, the dual-composite right-/left-handed (D-CRLH) resonators are adopted; therefore, the overall sizes of the resulting FPDs can be smaller than $0.012\lambda _{g}^{2}$ . Moreover, the equivalent circuit of the proposed FPD is investigated for the performance improvement. Input $Q_{e\text {-in}}$ should be double of output $Q_{e\text {-out}}$ for good matching, and good isolation can be obtained by appropriately utilizing $Q_{e\text {-in}}$ . For demonstration, three D-CRLH FPDs are designed for narrowband, wideband, and dual-band applications. Satisfactory agreements between the measured results and theoretical expectations are observed, verifying the validity of the proposed design concepts.

Quasi-Circulator Using an Asymmetric Coupler for Tx Leakage Cancellation

A quasi-circulator is proposed by using an asymmetric coupler with high isolation between the transmitting (Tx) and receiving (Rx) ports. The proposed quasi-circulator consists of quarter-wave transmission lines, which have unbalanced characteristic impedances and the terminated port, which is purposely unmatched with the reference impedance in the coupler. The port compensates for the asymmetric impedances of the coupler using the proposed design parameter. Because of its asymmetric structure and the usage of the unmatched port, the proposed circulator can be accurately designed to have high Tx–Rx isolation without increasing the signal losses in the Tx and Rx paths at the operating frequency. The proposed quasi-circulators show isolation improvements of 9.07 dB at 2.45 GHz and 7.95 dB at 24.125 GHz compared with conventional circulators using the symmetric couplers. The characteristic improvement of the proposed quasi-circulator was demonstrated by the increase of the detectable range of the 2.45 GHz Doppler radar sensor with the quasi-circulator.

Highly Efficient Fully Integrated GaN-HEMT Doherty Power Amplifier Based on Compact Load Network

This paper presents a fully integrated gallium-nitride high-electron-mobility transistor (GaN-HEMT) Doherty power amplifier (DPA) based on a compact load network for small-cell applications. The gate width of the transistor is optimized to have a load impedance of $100~\boldsymbol{\Omega }$ with a shunt inductor that can compensate for the output capacitor using a parallel resonance. A quarter-wave transmission line (TL) with a characteristic impedance of $100~\boldsymbol{\Omega }$ is realized using a high-pass ${\pi }$ -type lumped network for the carrier amplifier. The on-chip input network, including a power splitter, a quarter-wave TL, and matching networks for the carrier and peaking amplifiers, is designed using lumped components. The circuits are simplified by merging the multiple shunt components at a node into an inductor or a capacitor. As a result, the load network has only two shunt inductors. To verify the proposed circuits, a 2.6-GHz DPA integrated circuit (IC) was designed and implemented using a 0.4- ${\mu }\text{m}$ GaN-HEMT process. The implemented IC, which was mounted on a quad-flat no-lead package, exhibited a high drain efficiency of 54.4% at an average output power of 37.6 dBm with an adjacent channel leakage power ratio of −27.0 dBc using a downlink long-term evolution signal having a channel bandwidth of 10 MHz and a peak-to-average power ratio of 6.5 dB.