Simple DC Bias Research Articles

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.

Millimeter-Wave Frequency-Reconfigurable Metasurface Antenna Based on Vanadium Dioxide Films

A novel frequency-reconfigurable method using vanadium dioxide (VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) is proposed. VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is one kind of phase change material (PCM) which can be electrically switched between the states of insulator and metal. By integrating the VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film into a uniplanar compact photonic-bandgap (UC-PBG) structure, a frequency-reconfigurable metasurface (FRMS) structure with frequency ratio of 1.78 is constructed accordingly. Moreover, the active VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based FRMS is used as radiation element to design a high-gain millimeter-wave frequency-reconfigurable metasurface antenna (FRMSA), which is excited by a stepped waveguide through two slots of different lengths. In order to electrically activate the VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films of the antenna, a simple dc bias co-planarly localized with the FRMS is well designed. Benefiting from the convenient connection of the UC-PBG, only simple connection with two sides of the antenna is required for the dc bias, thus causing little impact on radiation due to far from the radiation region. One prototype is fabricated and measured for demonstration. When the VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film is activated to insulating state, the measured results show that the proposed FRMSA can operate in 23.25-24.3 GHz with the maximum gain of ~8.7 dBi, while it can work in 37-39.8 GHz with a peak gain of ~7.6 dBi when driven to metallic state. The ratio of two frequencies is about 1:1.61. Compared with other reported VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based antennas, the proposed antenna exhibits a larger frequency ratio and higher gain in millimeter-wave bands.

Development of a DC bias structure with reduced RF leakage for suppressing the multipacting effect in the high power coaxial couplers

Coaxial power couplers are being employed for RF power transmission to the low beta superconducting cavities used for proton beam acceleration in the 25 MeV superconducting linear accelerator (linac) demonstration facility of the China Initiative Accelerator Driven System (CiADS) project. However, the operation stability of the coaxial couplers was mainly limited by the multipacting effect, which can be suppressed by applying DC bias voltage between the inner and the outer conductors. In this paper, we found an RF leakage problem that the electromagnetic (EM) field inside the couplers can penetrate the bias capacitor and then propagate along the DC bias cable, thus disturbing the stability of the DC power supply and finally disabling the RF system. Therefore, a simple DC bias “T” transition part has been developed, where the series resistors are introduced to reduce the electromagnetic field propagating along the cable and make the structure intensely stable. The test results indicate that the blocking effect of the resistive solution is better than that of the conventional inductive method. The equivalent circuits of the resistive structure and the inductive structure are established and analyzed. The detailed test and analysis results of the new DC bias structure will be reported.

Metasurface-Inspired Low Profile Polarization Reconfigurable Antenna With Simple DC Controlling Circuit

A wide-band metasurface inspired polarization reconfigurable antenna with a low profile and a simple DC controlling circuit is introduced and analyzed in this paper. The proposed antenna consists of three parts, i.e., a coplanar waveguide-fed slot coupling antenna with slot slanted angle of 40 degrees, a metasurface superstrate which is composed of a 3·4 array of metallic rectangular patches, and a simple DC bias controlling circuit including p-i-n diode switches, metallic vias, chip inductors, and bias lines. When all the p-i-n diode switches are in ON state, the antenna will work in linear polarization state and generates linear polarized (LP) wave, the measured operating band ranges from 5.2 to 6.2 GHz (17.5% -10 dB impedance bandwidth), while the measured average realized gain is 6.2 dBi. When all the PIN diode switches are in OFF state, the polarization state of the antenna will alter to left-handed circular polarization and produces left-handed circular polarized wave, the measured -10 dB impedance bandwidth and 3 dB axial ratio bandwidth are 20.7% (ranges from 5.2 to 6.4 GHz) and 15.1% (ranges from 5.5 to 6.4 GHz), respectively, while the average realized gain is 7.1 dBi. Measured results of the reflection coefficients, realized gains at broadside, axial ratio, and radiation patterns are in good agreement with numerical simulations, which verifies the effectiveness and correctness of the proposed design.

A Compact Frequency-Reconfigurable 36-States Patch Antenna for Wireless Applications

We propose a simple and compact design of a patch antenna with the frequency-reconfigurability function. Six p-i-n diodes are positioned symmetrically along the nonradiating edges to allow the selection of one frequency band among 36 different states. One patch edge is shorted to the ground plane to reduce the antenna footprint. The antenna measured operating frequency ranges from 2.35 to 3.43 GHz. The measured peak gain and the measured peak efficiency are 4.3 dBi and 73%, respectively. The antenna has a compact size, preserves stable and unidirectional radiation patterns, uses a simple dc bias circuit, and is printed on a single-layer substrate. Hence, it is suitable for wireless applications requiring miniaturized size and acceptable performances.

Switchable circularly‐polarised square ring antenna controlled by dual‐loaded dual‐loop

A new switchable perturbing method is presented for a microstrip square ring antenna with a circular-polarisation diversity. The proposed antenna consists of three identical loops at the back ground side and one diagonal dual-loop at the front patch side for obtaining switchable circular-polarisation senses with a simple DC bias circuit. By control of the states of the two pin diodes in the front-sided dual-loop, both the left-handed and the right-handed circular polarisations can be easily alternated. The implemented antenna employing the dual-loop perturbation shows a good agreement with the simulation results and symmetrical circular polarisation characteristics at the resonant frequencies.

Small-Size Eight-Band Frequency Reconfigurable Antenna Loading a MEMS Switch for Mobile Handset Applications

A planar small-size eight-band frequency reconfigurable antenna for LTE/WWAN mobile handset applications is proposed. The proposed antenna consists of a feeding strip and a coupled strip, with a total dimension of 10 × 29.5 mm2. Reconfigurability is realized by incorporating a one-pole four-throw RF switch, which is embedded in the coupled strip and changes the resonant modes for the lower band. By combining four different working modes, the proposed antenna successfully realize the eight-band operation, covering the operating bands of 700~787 MHz, 824~960 MHz, and 1710~2690 MHz. In addition, the simple DC bias circuit of the RF switch has little effect on the antenna performances, with no significant reduction in antenna efficiency and variations in the radiation patterns. The measured antenna efficiencies are 40%~50% and over 60% for the lower band and the upper band, respectively. Prototypes of the proposed frequency reconfigurable antenna incorporating the one-pole four-throw switch are fabricated and measured. The measured results including return losses and radiation characteristics are presented.

Compact Metamaterial-Based Tunable Phase Shifter at 2.4 GHz

A compact metamaterial (MTM)-based tunable phase shifter consisting of four unit cells with a simple DC bias circuit has been designed at 2.4 GHz. The variable series capacitors and shunt inductors that are required to be loaded periodically onto a host transmission line are realized employing only chip variable capacitors (varactors). In addition, the proposed phase shifter requires only one DC bias source to control the varactors, with the matching condition of the MTM line automatically satisfied. The measured phase shifting range is 285.2° (from —74.2° to 211°). The measured insertion loss is approximately 1.5 dB. The circuit/electromagnetic-simulated and measured results are in good agreement.

Theory and design of a tunable Quasi‐Lumped Quadrature Coupler

AbstractIn this article, we present the theory and a design methodology for a tunable Quasi‐Lumped Quadrature Coupler (QLQC). Because of its topology, the coupler is simply reconfigured by switching the bias of two varactor diodes via a very simple DC bias circuitry. No additional capacitors or inductors are required. A prototype at 3.5 GHz is etched on a 0.130‐mm‐thick layer substrate with a dielectric material of relative permittivity of 2.22. The simulated and measured scattering parameters are presented. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2219–2222, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24526

A Novel Quad-Polarization Agile Patch Antenna

In this communication we present a novel polarization-agile microstrip antenna design. To dynamically change the polarization state, the radiating patch is fed by a tunable quasi-lumped coupler. The whole structure can be dynamically altered to radiate electromagnetic waves with vertical linear, horizontal linear, right-handed circular or left-handed circular polarization simply by changing the operating mode of the quasi-lumped coupler. Due to its topology the coupler is simply reconfigured by switching the bias of two varactor diodes via a very simple DC bias circuitry: no additional capacitors or inductors are required. A prototype is fabricated with a 0.762-mm-thick upper layer substrate for the radiating element and a 0.130-mm-thick layer substrate for the coupler circuit, both with the same dielectric material relative permittivity of 2.22. The simulated and measured scattering parameters, the axial ratio in circular radiation-mode and the cross-polarization level in linear mode, the gain and the radiation patterns are presented. The agile polarization capabilities of this new antenna, as demonstrated in this communication, underscore its suitability for modern wireless communications in a multi-path propagation environment.