DC Bias Network Research Articles

Cost-Effective Design of Polarization and Bandwidth Reconfigurable Millimeter-Wave Loop Antenna.

A singly fed reconfigurable circular loop antenna is proposed for millimeter-wave (mmWave) communication systems. This antenna's distinctive feature lies in its capacity to adjust both polarization and bandwidth characteristics, a capability made possible by the strategic integration of two PIN diodes. These diodes are engineered to function in various modes, allowing for three distinct polarization states and accommodating two distinct bandwidths. A meticulous alignment of these PIN diodes enables the utilization of a single DC bias network as a highly effective RF choke, which simplifies the design and reduces the associated losses. Additionally, a planar biasing network that consists of coplanar strip-lines (CPS) has been employed eliminating the need for lumped elements. The simple and totally planar configuration offers a choice of right-hand circularly polarized (RHCP) radiation or left-hand circularly polarized (LHCP) radiation at 28 GHz. This is accompanied by impedance matching and axial ratio (AR) bandwidths of 12.9% and 8%, respectively, over the same frequency range with a gain of 7.5 dBic. Moreover, when the PIN diodes are unbiased, the antenna offers linear polarization (LP) over two narrow bandwidths at 27 GHz and 29 GHz featuring a maximum gain of 7.2 dBic. Therefore, the proposed configuration offers three operating modes: wide-band RHCP, wide-band-LHCP, and LP over dual narrow bands. Significantly, simulated results closely align with the measured outcomes, affirming the robustness and accuracy of this design.

Miniaturized frequency-reconfigurable single-feed multi-band antenna with bandwidth enhancement for wireless applications

We propose a miniaturized frequency-reconfigurable multiband antenna with bandwidth enhancement. The main radiating patch is shorted from one edge to reduce the antenna footprint. An inverted U-shape microstrip line is integrated onto the antenna structure to excite more resonant frequencies. Indeed, by shorting the U-shape's arms, seven frequency bands can be created and controlled. The activation of the two p-i-n diodes is ensured by employing a simple symmetrical DC bias network. Furthermore, by adjusting the arms’ lengths, two resonances are combined to enhance the working bandwidth. Measurements reveal that the antenna resonates around the operating frequencies of 2.91 GHz, 3.55 GHz, 3.69 GHz, 3.83 GHz, 4.14 GHz, 4.18, and 4.24 GHz. The antenna exhibits stable patterns, with a measured peak gain and efficiency of 5.5 dBi and 86%, respectively. The antenna is compact; thus, it is recommended in wireless systems requiring multiband function with stable patterns and a reduced area.

A compact four states radiation-pattern reconfigurable monopole antenna for Sub-6 GHz IoT applications

A simple design of a compact radiation-pattern reconfigurable monopole antenna with different states is proposed. The antenna switches between four radiation patterns by introducing two parasitic elements, which can be controlled by activating or deactivating two p-i-n diodes. The antenna presents two opposite-direction unidirectional modes, one bidirectional mode, and one omnidirectional mode. Few lumped components are used in the DC bias network, reducing the fabrication cost and antenna complexity. An antenna prototype is fabricated and tested to validate the proposed approach. The common operating frequency band measured realized gain and realized efficiency ranging from 3.36 GHz to 3.6 GHz, 2.13 dBi to 4.93 dBi, and 62% to 82%, respectively. The antenna presents the benefits of a low profile, simple DC bias, and the ability to suppress radiations in unwanted directions. Therefore, the antenna can be easily integrated and used in different wireless systems requiring pattern diversity, for instance, in Sub-6 GHz Internet of Things (IoT) Applications.

Electrically tunable liquid crystal phase shifter with excellent phase shift capability per wavelength based on opposed coplanar waveguide

A tunable liquid crystal phase shifter based on opposed coplanar waveguide (OCPW) with excellent phase shift capability per wavelength is proposed. The proposed OCPW not only has good transmission characteristics and a quasi-TEM operating mode similar to the CPW, but also avoids the metalized via and complicated bias circuit in designing the phase shifter. Consequently, the phase shifter is easy to fabricate and miniaturize. The main structure of the phase shifter includes two functional components. One is the transition section, in which the flaring grounds and gradient stubs are utilized to realize the impedance and wave-number matching to the OCPW phase shift part; the other is a tunable phase shift section, which is composed of the OCPW centerline and ground with staggered periodic stubs stretching out. To realize tunable phase shifting by applying different DC bias voltages, a DC bias network capable of blocking RF signal is elaborately designed. An equivalent circuit model of the phase shift part is established and represented using the ABCD matrix, so that the relation between the related parameters and the phase shift per wavelength can be easily obtained to guide the design. The measurement results demonstrate that the proposed phase shifter achieves a total of 300° phase shifting, as high as 289°/λ0 phase shift per wavelength, and a good figure-of-merit of 59°/dB at 14.5 GHz. The phase shifter features the reflection coefficient less than −10 dB and the transmission coefficient bigger than −6 dB from 9.3 to 15 GHz.

Design of a 1 Bit Broadband Space-Time-Coding Digital Metasurface Element

A 1 bit single-polarization broadband space-time-coding digital metasurface element with a zero cross polarization is proposed. This element consists of a modified patch, an electronic switch, a dc-bias network, a ground plane, and two-layer dielectrics. The upper patch with edge loading and centered square hole is fully optimized to achieve broadband and stable phase difference between two states. By electronically controlling the diode, the element achieves a 1 bit phase shift with a relative bandwidth of 20% within 180° ± 30° from 7.71 to 9.43 GHz. Moreover, a negligible cross polarization is obtained due to the uniaxial symmetry of the structure, and the amplitude loss is less than 0.8 dB for two states. The experimental results measured in a rectangular waveguide are well matched with the simulations, further demonstrating validity of the proposed element.

Frequency and impedance reconfigurable antenna using magnetically-actuated low-loss Ferrofluid loads

ABSTRACTWith space and spectrum at a premium, antennas must be capable of operating well across a variety of frequencies and environments. This work presents a novel method of frequency and impedance reconfiguration through the actuation of a ferrofluid load with a permanent magnetic bias field, while still achieving up to 85% efficiency. Under a sufficiently strong bias field, the ferrofluid load behaves as a low-loss movable dielectric load, and the actuation method avoids the complexity associated with microfluidic pumps and DC bias networks. This work opens a new field of reconfiguration mechanisms for antennas through magnetic repositioning of low-loss ferrofluid loads.

An Electronically Controlled Leaky-Wave Antenna Based on Corrugated SIW Structure With Fixed-Frequency Beam Scanning

A novel electronically controlled (EC) leaky-wave antenna (LWA) based on corrugated substrate integrated waveguide (CSIW) with fixed-frequency beam-steerable capability is presented in this letter. This structure is based on a CSIW structure with rectangular ring slots and metallic vias to the ground, which realizes two isolated dc equipotential planes. Each slot of the rectangular ring is loaded with a varactor diode, and thus the series and shunt capacitance are tunable by adjusting the dc bias voltage, which eventually results in beam scanning at a fixed frequency. The proposed antenna is a single-layer structure and has a simplified dc bias network, which merely needs an inductor and a short microstrip line. An EC beam-steerable CSIW LWA is designed and experimentally validated. It is experimentally demonstrated that the radiation angle ranges from −40.66° to 31.32° as the bias voltage is tuned from 32 V to 7.5 V at 4.5 GHz.

Design of a Multifunctional Reconfigurable Metasurface for Polarization and Propagation Manipulation

In this paper, a multifunctional reconfigurable polarization conversion metasurface (MRPCM) is designed for controlling both the propagation and the polarization of electromagnetic wave. The proposed metasurface contains two-layered structures separated by the air layer. The top layer is composed of two back-to-back C-shaped metallic resonators, which is used to convert the polarization. The bottom layer is consisted of two orthogonal metal gratings, which works as the patterned ground. The PIN diodes are embedded on both the upper and lower layer of the patterned ground and controlled through two independent sets of external DC bias network to achieve the multi-function. The gratings serve as both the resonant structure and the PIN diode biasing lines. Therefore, no additional feeding lines are introduced, which can decrease the impact on the performance of the MRPCM. When the PIN diodes of the two layers are turned on, the MRPCM will reflect and convert the incident wave into cross-polarization. When the PIN diodes of the two layers are turned off, the dual-polarization incident waves are transmitted through the MRPCM without conversion. If the PIN diodes of the two layers are in different state, the x - (OFF-ON) and y -polarized (ON-OFF) incident waves are transmitted and their E-field are rotated by 90°, respectively. Both numerical simulations and experimental results show good reconfigurable performance of the MRPCM.

Beam‐ and polarisation‐reconfigurable SIW ring‐slot antenna array

A beam- and polarisation-reconfigurable substrate integrated waveguide (SIW) ring-slot antenna array is proposed in this study. The 2×2 ring-slot antenna array can generate beams in four different directions in two orthogonal linear polarisations (LPs). This is achieved by a feeding network consisting of four 90° SIW 3 dB couplers arranged in a multilayer structure for a compact antenna size of 131.6 mm × 65.8 mm × 4.9 mm. The antenna elements' LP plane is controlled by PIN diodes, switched by a DC bias network integrated on the antenna substrate. The proposed antenna array is designed for the 5.8 GHz industrial, scientific and medical (ISM) frequency band and verified by measurements. Experimental results validate good impedance matching over the entire frequency band as well as the beam and polarisation reconfigurability.

A Wideband Multifunctional Multilayer Switchable Linear Polarization Metasurface

In this letter, a wideband multifunctional and switchable linear polarizer has been presented based on an active metasurface for the X-band. The proposed structure consists of three metallic layers and two dielectric spacers. The switchable function is obtained by embedding PIN diodes, which are controlled by four independent sets of external dc bias networks on the top and bottom metallic layers. Two main functions (polarization conversion and polarization separator) and four working states are exhibited by combining four independent sources. As a polarization rotator, the proposed structure converts electromagnetic (EM) waves to cross-polarization from 5.2 to 16.7 GHz with the polarization conversion ratio beyond 90%, while as a polarization separator, the copolarization EM waves can be transmitted and the cross-polarization waves reflected with isolation over 10 dB from 8 to 14.3 GHz. The numerical and experimental results are in a good agreement, which demonstrates the excellent and stable performance of the proposed structure.

A 6–18-GHz GaN Reactively Matched Distributed Power Amplifier Using Simplified Bias Network and Reduced Thermal Coupling

Two-stage reactively matched gain cells are proposed to implement a high-gain multioctave distributed power amplifier (DPA). The proposed reactively matched distributed amplifier (RMDA) structure shows high gain and power in a small die size. Detailed analysis is presented to understand the design criteria for interstage matching of reactively matched cells. A shared dc bias network is proposed to simplify the biasing of each section to reduce the DPA die size. The thermal coupling effect of GaN high-power amplifier is minimized by optimizing the chip layout. The theoretical analysis is verified by the simulation and supported by the measured data. Two RMDAs are fabricated with a commercial 0.25- $\mu \text{m}$ GaN HEMT process. The implemented RMDA with the compact transistor layout has been implemented in a small die size of 10.7 mm2 and shows output powers reaching 40.3–43.9 dBm, power added efficiencies (PAEs) of 16–27%, and small-signal gains of 15.3–23.2 dB. The RMDA with the reduced thermal coupling achieves 40.6–43.4 dBm with a peak PAE of 29% in a slightly larger die size of 13.8 mm2. To the best of our knowledge, this is the first demonstration of a GaN DPA using reactively matched gain cells, showing very high gain and efficiency over multioctave bandwidth in a small die size.

Design of double-layer active frequency-selective surface with PIN diodes for stealth radome**Project supported by the National Basic Resarch Program of China (Grant No. 2014CB339800) and the National Natural Science Foundation of China (Grant No. 11173015).

An experimental double-layer active frequency-selective surface (AFSS) for stealth radome is proposed. The AFSS is a planar structure which is composed of a fixed frequency-selective surface (FSS), a PIN diodes array, and a DC bias network. The AFSS elements incorporating switchable PIN diodes are discussed. By means of controlling the DC bias network, it is possible to switch the frequency response for reflecting and transmitting. Measured and simulated data validate that when the incidence angle varies from 0° to 30° the AFSS produces more than −11.5 dB isolation across 6–18 GHz when forward biased. The insertion loss (IL) is less than 0.5 dB across 10–11 GHz when reverse biased.

Electronically Switchable Broadband Metamaterial Absorber

In this study, the novel electronically switchable broadband metamaterial absorber, using a PIN diode, is proposed. The unit cell of the absorber was designed with a Jerusalem-cross resonator and an additive ring structure, based on the FR-4 dielectric substrate. Chip resistors and PIN diodes were used to provide both a broadband characteristic and a switching capability. To satisfy the polarization insensitivity, the unit cell was designed as a symmetrical structure, including the DC bias network, electronic devices, and conductor patterns. The performance of the proposed absorber was verified using full-wave simulation and measurements. When the PIN diode was in the ON state, the proposed absorber had a 90% absorption bandwidth from 8.45–9.3 GHz. Moreover, when the PIN diode was in the OFF state, the 90% absorption bandwidth was 9.2–10.45 GHz. Therefore, the absorption band was successfully switched between the low-frequency band and the high-frequency band as the PIN diode was switched between the ON and OFF states. Furthermore, the unit cell of the proposed absorber was designed as a symmetrical structure, and its performance showed insensitivity with respect to the polarization angle.

A Novel 2-B Multifunctional Active Frequency Selective Surface for LTE-2.1 GHz

This paper proposes a 2-b multifunctional active frequency selective surface (MAFSS) whose structure is made up of two metallic layers printed on both sides of an F4BME substrate, measuring $320 \times 320 \times 0.8$ mm3. The PIN diodes, embedded on two metallic layers, are controlled through two independent sets of external dc bias network. No additional feeder lines are considered necessary within the MAFSS array, which weakens the bias network’s negative impact on the transmission characteristics of the MAFSS. Using an innovative and effective diode switching technique, two functions (electromagnetic switch and polarization selection) and thus four working states (dual-polarized bandpass for code “00,” dual-polarized shielding for code “11,” TE wave selection for code “10,” and TM wave selection for code “01”) have been realized. The equivalent circuit method and the surface current analysis have been used for a better understanding of the physical principles of the design. A prototype of the proposed structure has been fabricated and measured. The measurements have shown a good agreement between the simulated and the measured results, demonstrating thereby that the proposed structure can give excellent performance. Using the results of extensive numerical and experimental studies, the proposed structure has also been proved to give stable performance, with respect to different incident angles and wave polarizations around LTE-2.1 GHz.

Multi-band pattern reconfigurable Yagi-Uda antenna

In this study, novel designs of single-band and tri-band pattern reconfigurable antennas are proposed. The design of single-band pattern reconfigurable antenna is accomplished by the use of varactor diodes with the parasitic elements placed on both sides of the driven conventional printed dipole antenna. By tuning the capacitance of varactor, the antenna operates in four different configurations of radiation pattern which include bi-directional end-fire, broadside, and uni-directional end-fire radiation patterns. The tri-band pattern reconfigurable antenna design is achieved by the use of parasitic elements on both sides of a tri-band driven dipole antenna. Dual-band LC resonators are used as loading elements along the arms of printed dipole to get two lower order modes in addition to the reference dipole mode, resulting in a triband operation of the driven element. The electrical lengths of the parasitic elements with respect to the tri-band driven element are controlled by suitably embedding varactor and PIN diodes with them. The proposed tri-band antenna operates in ten different configurations of radiation patterns in the three operating bands. Fully functional prototypes of single-band and tri-band pattern reconfigurable antennas along with the DC bias networks have been fabricated to validate the results obtained in simulation.

Micro-fabrication considerations for MEMS-based reconfigurable antenna apertures: with emphasis on DC bias network

This note addresses the main challenges involved in monolithic micro-fabrication of large capacitive-MEMS-based reconfigurable electromagnetic apertures in antenna applications. The fabrication of a large DC bias line network, and also the metallic features in such apertures, requires special attention and optimization. It is shown that the choice of DC bias network material can impact DC and RF performance of the structure, and a trade-off between switching time and radiation pattern integrity should be considered.

Compact beam‐reconfigurable feed for large aperture antennas

This study presents a novel compact beam-reconfigurable horn antenna using a fully operational MEMS-tuned partially reflective surface (PRS). Two symmetric MEMS capacitive switches across a slot on a single layer patch PRS tune its reflection and enable the dynamic reconfiguration of the horn pattern. The authors explore the potential of this PRS in two different applications: beamwidth and beam-shape reconfiguration. Furthermore, a novel in-house process for monolithic fabrication of the MEMS-integrated full PRS and a dedicated DC bias network is developed and analysed. The proposed structure can be used as the feed of a reflector, reflectarray or transmittarray to control the aperture illumination and allow beam-reconfiguration.

Dual‐band GaN power amplifiers with novel DC biasing networks incorporating offset double‐sided parallel strip line

This study presents a novel dual-band DC biasing network and its application in the design of GaN power amplifiers (PAs). By integrating offset double-sided parallel strip line which can easily realise high characteristic impedance and thus narrow microstrip line, the proposed biasing network can obtain much higher operation frequency ratio than the conventional design. To demonstrate the new methodology, two dual-band GaN PAs applying the presented dual-band DC biasing network are implemented. The operation frequencies are 1.8/3.5 and 0.9/3.5 GHz. Three-section networks for complex load are used for dual-frequency input and output matching. Good agreement between the simulation and measurement is observed, which fully demonstrate the feasibility and validity of the presented DC bias networks in power amplifier designs.

Monolithic-Integrated MEMS-Tunable Reflective Cell for Ku-Band Mobile Satellite Two-Way Connectivity

This paper presents the design and measurement of a single-layer micro-electromechanical system (MEMS)-tunable reflective unit cell with orthogonally polarized dual bands for Ku-band mobile satellite connectivity. Six capacitive MEMS switches across each slot of a cross-slotted patch tune its reflection phase at 12 GHz (reception) with vertical polarization and 14 GHz (transmission) with horizontal polarization. This unit cell provides four phase states with overall phase swing of 200° and 180° and average reflection amplitude of -0.79 and -0.69 dB at the lower and upper bands, respectively. This unit cell can be used for generation of an independently controlled beam at each of its operating bands. A monolithic process is also developed for the fabrication of this reflective cell along with the dedicated dc bias network. For unit cell measurements, a custom-designed waveguide setup with four DC pins was fabricated for simultaneous and independent control of all MEMS switches. The measurement results are in good agreement with simulations.

Active metasurface for controlling reflection and absorption properties

A novel active metasurface is proposed in this paper. The proposed metasurface can be electronically switched between the reflection and the absorption modes by a tunable component, such as a PIN diode. When the PIN diode is in the on-state, the proposed metasurface exhibits near-perfect absorptivity at 10 GHz. On the other hand, when the PIN diode is in the off-state, the proposed metasurface exhibits near-perfect reflectivity over a wide bandwidth at 10 GHz. A unit cell is designed to include a DC bias network, which yields reliable performance.