Measured Input Return Loss Research Articles

Harmonic Suppressed Wilkinson Power Divider Using Parallel Resonant Shunt Stub

This paper proposes a harmonic-suppressed Wilkinson power divider (HS WPD) utilizing parallel resonant shunt stubs (PRSSs). PRSSs are integrated into the conventional WPD by adding functionalities such as bandpass filtering, harmonic suppression, and physical port separation. The resonance conditions and design equations of the PRSS are theoretically derived and verified through circuit simulations. Using the PRSS, we designed an HS WPD operating at 1 GHz. The fabricated HS WPD demonstrated an insertion loss of 3.2 dB at the fundamental frequency, with a wide 3 dB bandwidth of 129%. The harmonic suppression levels at the 2nd and 3rd harmonic frequencies are measured to be 21.0 dB and 25.8 dB, respectively. The measured input return loss at the fundamental frequency was 27.9 dB, whereas the output return loss was 24.6 dB. Additionally, the HS WPD demonstrates isolation levels at the fundamental, 2nd, and 3rd harmonic frequencies, with levels of 29.2 dB, 17.8 dB, and 47.1 dB, respectively. It also exhibited broadband isolation (>8.7 dB) across the frequency range of 100 kHz to 3.35 GHz. The PRSS design allows for the physical separation of the ports without requiring additional circuitry. Compared to previously reported PDs, the proposed design offers multiple functions in a compact size, making it highly suitable for various microwave systems.

Wideband Multi-Channel Multi-Way Power Combiner With High Frequency Selectivity

A wideband multi-channel multi-way power combiner with high frequency selectivity circuit using the center-loaded multimode step impedance resonator (SIR) is presented in this paper. The SIR stubs can generate four transmission zeros on the both sides of the passbands, which improves the frequency selectivity of the two channels. The distributed coupling technique is used to connect the two different-frequency channels without any additional matching network. The presented power combiner is designed, fabricated, and measured. The measured center frequency and relative 3-dB bandwidth of the two channels are 1.73/2.71 GHz and 43%/35%, respectively. The measured input return loss are greater than 16.4/20.8 dB, the measured output return loss is greater than 20.4/13.4 dB, and the measured insertion loss are 0.7/1.0 dB. Moreover, the measured different-frequency isolation between the two channels is greater than 26.8 dB, and the measured same -frequency isolation are greater than 23.9/29.1 dB, respectively.

A Sub-6G SP32T Single-Chip Switch with Nanosecond Switching Speed for 5G Applications in 0.25 μm GaAs Technology

This paper presents a single-pole 32-throw (SP32T) switch with an operating frequency of up to 6 GHz for 5G communication applications. Compared to the traditional SP32T module implemented by the waveguide package with large volume and power, the proposed switch can significantly simplify the system with a smaller size and light weight. The proposed SP32T scheme utilizing tree structure can dramatically reduce the dc power and enhance isolation between different output ports, which makes it suitable for low-power 5G communication. A design methodology of a novel transmission (ABCD) matrix is proposed to optimize the switch, which can achieve low insertion loss and high isolation simultaneously. The average insertion loss and the isolations are 1.5 and 35 dB at 6 GHz operating frequency, respectively. The switch exhibits the measured input return loss which is better than 10 dB at 6 GHz. The 1 dB input compression point of SP32T is 15 dBm. The prototype is designed in 5 V 0.25 μm GaAs technology and occupies a small area of 12 mm2.

Low-insertion-loss Gysel power combiner with high power density and high isolation

AbstractA suspended-stripline Gysel low-insertion-loss power combiner is presented in this paper. The multi-layer cavity structure reduces the circuit size and increases power density, composed of suspended strip lines and coaxial lines. The transmission-line theory is used to analyze this proposed power combiner, and the equivalent circuit model is developed to investigate the characteristics and design of the power combiner. The measured input return loss is greater than 20 dB from 7.15 to 9.35 GHz. The measured insertion loss is less than 0.36 dB, and the power-combining efficiency is greater than 92% from 7.39 to 9.19 GHz. The maximum power-combining efficiency is 98.8% at 8.1 GHz. Besides, the measured isolation is greater than 20 dB from 7 to 10 GHz. The power capacity is analyzed, and the cross-sectional power density is greater than 3.57 kW/cm2. The measured and simulated results show reasonable agreement with each other.

Wave discrimination at C-band frequencies in microstrip structures inspired by electromagnetically induced transparency

We present the design and practical implementation of a microstrip diplexer based on the wave discrimination property associated with the electromagnetically induced transparency (EIT)-like effect. The EIT is a quantum interference phenomenon which happens between two atomic transition pathways and allows wave propagation within a medium’s absorption spectrum. Here, we exploit an analogous interference mechanism in a three-port microstrip structure to demonstrate a diplexer based on the EIT-like effect in the microwave regime. Since the transparency is accompanied by a high transmission and strong dispersion characteristics, compact frequency discriminating structures that can resolve nearby frequencies with high isolation can be devised. Our proposed C-band diplexer consists of pairs of unequal open-circuit stubs, which resonate at detuned frequencies and interfere to form the EIT-like passbands for diplexer action. The design is highly compact and scalable in frequency for both PCB and on-chip applications. A prototype of diplexer is fabricated for the center frequencies of lower and upper passbands at 4.6 GHz and 5.5 GHz respectively. The transmission zeros are designed at the complementary channels so that the two passbands are highly isolated presenting the isolation of about 40 dB. The measured insertion loss of lower and upper passband is 0.59 dB and 0.61 dB respectively. Measured input return loss is better than − 15 dB, while the output return losses are well below − 12 dB. Moreover, a decent value of about 200 is achieved for the group refractive index around the EIT-like passbands, which reveals the slow wave characteristics of the proposed EIT-based diplexer.

A 4.4-mA ESD-Safe 900-MHz LNA With 0.9-dB Noise Figure

A 900-MHz 1.2-V 4.36-mA low-noise amplifier (LNA) with a minimum of 0.92-dB noise figure (NF) at 868 MHz, -12-dBm IIP3, with one inductor (external) is demonstrated. The circuit achieves narrowband input matching on a wideband LNA without inductive degeneration. A new half-cascoding technique is used to improve the input matching (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) while simultaneously achieving sub-1-dB NF performance. The 0.13-μm CMOS LNA is fabricated with embedded electrostatic discharge (ESD) protection diodes that add 60 and 80-fF loads at the RF input and output ports. At 868 MHz, the packaged LNA has a measured input return loss (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) of -18 dB and the transmission gain (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> ) of 14.2 dB. At 900 MHz, the LNA has a measured NF of 0.98 dB. The LNA (excluding the buffer) occupies an area of 0.047 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The chip passes the human body model (HBM) test with an ESD zap of 2.5 kV within 10% margin of its prezap I-V characteristics, under JEDEC standards. Multiple packaged chips were characterized with no perceptible difference in performance, indicating a robust design.

A Fully Integrated Arbitrary Power Divider on Printed Circuit Board by a Novel SMD-Resistor-Free Isolation Network

An arbitrary power divider (PD), which can be fully integrated on a multilayered printed circuit board (PCB), is presented without using the surface-mounted device (SMD) resistors. In the proposed SMD-resistor-free isolation network, a new multiple microstrip gap-coupled resonators (MM-GCRs) is designed in an FR4 substrate based on an optimization algorithm to achieve an equivalent grounded resistor in the desired frequency band. Consequently, the acquired output matching and isolation bandwidths are designable and much wider than that of other existing SMD-resistor-free PDs with both output matching and isolation characteristics. To verify it, the design of PCB-based SMD-resistor-free PDs with the power division ratio being 1–3 is given. For all fabricated PDs, the measured input return loss and extra insertion loss are, respectively, better than 20 dB and less than 0.52 dB, respectively, at the operating frequency. In addition, the measured output return loss and isolation loss are better than 15 dB from 2.4 to 2.5 GHz. Moreover, the measured output matching and isolation bandwidths are, respectively, 8 and 3.5 times wider than that of other existing SMD-resistor-free PD with both output matching and isolation characteristics. Since the proposed PD is synthesized based on distributed elements without using any SMD resistor, the proposed PD thus possesses the advantages of being suitable for system-on-package (SoP), cost-efficient, suitable for millimeter-wave (mm-Wave) application, and capable to be fully integrated on a multilayered PCB.

A 0.1–1.5 GHz multi-octave quadruple-stacked CMOS power amplifier

In this letter, we design and analyze 0.1–1.5 GHz multi-octave quadruple-stacked CMOS power amplifier (PA) in 0.18 μm CMOS technology. By using two-stage quadruple-stacked topology and feedback technology, the proposed PA realizes an ultra-wideband CMOS PA in a small chip area. Wideband impedance matching is achieved with smaller chip dimension. The effects of feedback resistors on the RF performance are also discussed for this stacked-FET PA. The PA shows measured input return loss (< –10.8 dB) and output return loss (< –9.6 dB) in the entire bandwidth. A saturated output power of 22 dBm with maximum 20% power added efficiency (PAE) is also measured with the drain voltage at 5 V. The chip size is 0.44 mm2 including all pads.

Compact four-way suspended-stripline power divider with low loss and high isolation

AbstractA four-way suspended-stripline power divider is presented in this letter. The power dividing network is designed by using the suspended stripline, while the isolation network is designed by using the microstrip line. The vias are used to connect the power dividing network and the isolation network. The even- and odd-mode analysis method is applied to design the presented power divider. The simulated and measured results of the presented power divider show reasonable agreement with each other. The measured input return loss in the band is greater than 28 dB (7.92 to 9.53 GHz), while the measured insertion loss is less than 0.37 dB. The measured output return loss is greater than 20 dB from 7.82 to 9.86 GHz. Besides, the measured output isolation is greater than 20 dB.

Additive manufactured graphene composite Sierpinski gasket tetrahedral antenna for wideband multi-frequency applications

Here we report a pre-fractal antenna design based on the Sierpinski tetrahedron that has been developed with additive manufacturing. The Sierpinski tetrahedron-based antenna was simulated with finite element method (FEM) modeling and experimentally tested to highlight its potential for wideband communications. The Sierpinski tetrahedron-based antennas were fabricated by two methods, the first involves printing the antenna out of acrylonitrile butadiene styrene (ABS), followed by spin casting a coating of an ABS solution containing graphene flakes produced through electrochemical exfoliation, the second method involves 3D printing the antenna from graphene-impregnated polylactic acid (PLA) filament directly without any coating. Both fabrication methods yield a conductive medium to enable receiving EM signals in the low GHz frequency range with measured input return losses higher than 35 dB at resonance. These antennas incorporate the advantages of 3D printing which allows for rapid prototyping and the development of devices with complex geometries. Due to these manufacturing advantages, self-similar antennas like the Sierpinski tetrahedron can be realized which provide increased gain and multi-band performance.

A Resistor-Free $N$ -Way Power Divider With Simultaneous Output Matching and Isolation

This letter introduces a resistor-free $N$ -way power divider (PD) having simultaneous output matching and output isolation characteristics. By properly designing the parameters of the proposed isolation network, an equivalent grounded resistor is obtained under odd-mode excitation of the output ports. Based on this characteristic, the proposed $N$ -way PD can then achieve output matching and isolation between the output ports. To verify it, the design of a three-way resistor-free PD structure is given. At the operating frequency, the measured input return loss and insertion loss are 47 and 5.18 dB with corresponding output reflection and isolation coefficients less than −15 dB.

Novel Wideband Absorptive Bandstop Filters With Good Selectivity

This paper presents a new type of wideband absorptive bandstop filter (ABSF) design that is capable of absorbing the input power within the stopband at its Port 1. It is achieved by introducing one additional resistor to a conventional wideband stub bandstop filter. Suitable design procedures are established to facilitate the synthesis of the proposed wideband ABSFs with different filter orders and stopband bandwidths. To validate the proposed design method, microstrip ABSF design examples with a stopband center frequency $f_{0}$ of 2 GHz and 30-dB stopband bandwidths ranging from 12% to 42% are demonstrated. The measured stopband rejection at $f_{0}$ is larger than 60 dB for all design examples. In addition, good input return losses both in the passband and stopband are achieved, and the measured input return loss is better than 10 dB from dc to $2.5f_{0}$ . Larger than 90% of the input power within the stopband can thus be dissipated by the proposed ABSF. To the best of our knowledge, these are the ABSFs with the widest stopband bandwidth ever reported.

Ultra‐wideband power divider employing coupled line and short‐ended stub

ABSTRACTA compact two‐way equal power divider using three‐line coupled structure is proposed. The effective length of the power divider is around a quarter‐wavelength. To enhance the bandwidth of operation, a half‐wavelength resonator is constructed by introducing a short‐ended stub to combine with the open‐ended microstrip line. A prototype of the power divider is designed and fabricated. The measured input return loss, output return loss, isolation, amplitude imbalance, and phase imbalance are better than 10.3, 14.4, 10.1, 0.2 dB, and 3.2°, respectively, across the entire ultra‐wideband (UWB). © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:713–715, 2016

Range-Adaptive Wireless Power Transfer Using Multiloop and Tunable Matching Techniques

In this paper, a range-adaptive wireless power transfer (WPT) system is proposed to achieve high efficiency over a wide range of distances by using tunable impedance matching techniques. A multiloop topology is employed to greatly reduce the variation in the input impedance of the WPT system with respect to the distance, where one of the four loops with a different size is selected, depending on the distance. It enables the design of a simple tunable matching circuit using a single variable capacitor. An algorithm is written to find the optimum loop and capacitance in the matching network, based on the measured input return loss using a directional coupler and rectifiers. The fabricated WPT system shows a range-adaptive operation with high efficiency over a wide range of distances. It attains 48% efficiency at a distance of 100 cm with a maximum efficiency of 92% at a distance of 10 cm.

Enhanced dual‐circular polarised four‐arm Archimedean spiral antenna with low‐profile cavity backing

A wideband dual-circular unidirectional four-arm Archimedean spiral antenna operating from 0.6 to 2.4 GHz is presented. Without a cavity, the antenna radiates bi-directionally and the dual-circular polarisation of the spiral antenna at boresight is limited to a frequency range from 0.6 to 1.5 GHz. After adding a low-profile, 15 mm deep metallic cavity, the dual-circular polarisation at boresight is extended to more than 2.4 GHz and uni-directional radiation is realised. The four-arm spiral antenna is excited through a feed network consisting of a wideband four-way power divider and four wideband digital 2-bit phase shifters. This feed network facilitates instantaneous switching between right hand circular polarisation and left hand circular polarisation. The measured input return loss of the system is more than 10 dB for the entire two-octave bandwidth. The measured boresight gain from 0.6 to 2.4 GHz is −2.8 to 11.2 dBi and −3.1 to 8.7 dBi for RHCP and LHCP, respectively.

CMOS Broadband Programmable Gain Active Balun With 0.5-dB Gain Steps

This paper presents a CMOS broadband programmable gain active balun (PGAB) that demonstrates seven digitally controlled gains with 0.5-dB gain steps separately for plus and minus output ports. The PGAB was designed and fabricated in a 130-nm RFCMOS process. For the maximum gain state, the measured gains of the plus and minus ports are 0.0 and 1.1 dB at 2 GHz. The operating frequency range is from 1.0 to 8.0 GHz by 0.3-dB gain step error, and it is from 1 to 13.0 GHz by 3-dB gain attenuation. For the maximum gain state, the measured amplitude imbalance and phase imbalance from 1 to 16 GHz are less than 1.4 dB and 4.1 $^{\circ}$ , respectively. The measured input return losses are better than 13.5 dB, and the output return losses are better than 18.5 dB for all controlled gain states from 1 to 16 GHz. The measured IP1dB at 7 GHz is 6.1 dBm. The measured noise figures for the plus and minus ports from 2 to 14 GHz are less than 11.2 and 10.2 dB, respectively. The supply voltages are 3.0 and 1.5 V, and the measured power consumption is 93 mW. The core area of the fabricated integrated circuit is 0.38 mm $\,\times\,$ 0.36 mm.

Design of Hybrid Ambient Energy Harvesting Antenna for Wireless Sensor Nodes

To the high maintenance cost for changing wireless sensor’s battery in Internet of Things (IoT), a hybrid ambient energy harvesting system for wireless sensor’s power supply is proposed. The system can collect the ambient RF energy, vibration energy and light energy, converts them into DC supply. This paper focuses on the analysis and design of the hybrid energy harvesting antenna, using a novel structure to combine three energy receivers in one antenna, which reduces the size and the cost effectively. The antenna operates at both 3G mobile frequency (1.9GHz) and 4G mobile frequency (2.6GHz), the measured input return loss is 24.3dB and 19.9dB, respectively.

Dual-Band N-Way Series Power Divider Using CRLH-TL Metamaterials With Application in Feeding Dual-Band Linear Broadside Array Antenna With Reduced Beam Squinting

A general design for a non-radiating dual-band N-way series power divider (SPD) is presented in this paper. The non-linear phase responses of composite right and left handed transmission-line (CRLH-TL) and non-radiating CRLH-TL (NR-CRLH-TL) are used to achieve the desired dual-band performance. Theory and design procedure of this divider are analyzed in detail. For demonstration, a dual-band 3-way power divider was designed, fabricated and tested at two arbitrary design frequencies: 0.915 GH (UHF) and 2.440 GHz (ISM). There is nearly equal and in-phase power division to all three output ports in the two passbands while the measured input return loss remains below 10 dB. Also, the dual-band divider presents the benefit of setting the output ports arbitrarily apart. In addition, the dual-band nature of the proposed SPD, low cost and easy integration with printed antenna make it well suited for feeding dual-band planar antenna arrays. To verify the performance of the proposed divider, the designed dual-band 3-way SPD is used as a series feed network for a linear array of printed monopole antennas, designed to radiate in the broadside direction. It is shown that the proposed dual-band planar antenna array experiences a decrease in the amount of beam squinting with a change in frequency for both the operating bands.

A 1.2-V 5.2-mW 20–30-GHz Wideband Receiver Front-End in 0.18-$\mu{\hbox {m}}$ CMOS

This paper presents a low-power wideband receiver front-end design using a resonator coupling technique. Inductively coupled resonators, composed of an on-chip transformer and parasitic capacitances from a low-noise amplifier, a mixer, and the transformer itself, not only provide wideband signal transfer, but also realize wideband high-to-low impedance transformation. The coupled resonators also function as a wideband balun to give single-to-differential conversion. Analytic expressions for the coupled resonators with asymmetric loads are presented for design guidelines. The proposed receiver front-end only needs a few passive components so that gain degradation caused by the passive loss is minimized. Hence, power consumption and chip area can be greatly reduced. The chip is implemented in 0.18-μm CMOS technology. The experimental result shows that the - 3-dB bandwidth can span from 20 to 30 GHz with a peak conversion gain of 18.7 dB. The measured input return loss and third-order intercept point are better than 16.7 dB and -7.6 dBm, respectively, over the bandwidth. The minimum noise figure is 7.1 dB. The power consumption is only 5.2 mW from a 1.2-V supply. The chip area is only 0.18 mm2 .

Ultra-wideband (UWB) coaxial-waveguide power divider using end-coupling structures

Based on end open-circuited electrical coupling structure, a novel ultra-wideband (UWB) coaxial-waveguide power divider is presented in this study. The simple equivalent circuit for the presented UWB coaxial-waveguide power divider is developed and the maximum power handling capability of the presented coaxial power divider is evaluated. A UWB four-way coaxial-waveguide power divider is designed, optimised and fabricated. The simulated and measured results of the fabricated power divider show reasonable agreement. The measured input return loss is greater than 10 dB over the entire UWB band and also greater than 17 dB from 2.7 to 9 GHz. The measured average insertion loss, amplitude imbalance, group delay and group delay imbalance are about 0.4 dB (not including the 6 dB power-dividing insertion loss), ±0.45 dB, about 0.41 ns and ±0.5 ns, respectively, across the UWB band.