Query: tunable slot matching

title: CPW Fed Frequency Reconfigurable Slot Loop Antenna With a Tunable Matching Network Based on Ferroelectric Varactors
abstract: A frequency reconfigurable slot loop antenna with a tunable matching network (TMN) is designed, fabricated, and measured. The frequency reconfigurable antenna is designed by loading ferroelectric (FE) varactors along a slot loop. The varactor loaded slot loop antenna is fed using a coplanar waveguide (CPW) line rather than a microstrip line to preserve the advantage of being uniplanar. However, because it is more difficult to achieve a good matching over wide bandwidth with a direct CPW feed, we propose to add a TMN. It is found that the TMN can be realized using a series varactor, which does not increase the size of the antenna. Measurement results show that by adjusting the bias of the FE varactors from 0 to 15 V, the operating frequency of the antenna can be tuned from 6.71 to 9.14 GHz, translating into a 30.6% frequency tuning range (FTR) At 6.71 GHz, the size of the slot loop is 0.056 l0 x0.056l0. When biased at 15 V, the antenna gain is 3.1 dBi. Over the entire FTR, the return loss is greater than 20 dB, demonstrating the effectiveness of the tunable matching technique.

title: Tunable Slot Type Ground Radiation Antenna with Dual Band Operation Using LC Resonator
abstract: A dual band tunable slot type ground radiation antenna is proposed. The feeding structure consists of a coplanar waveguide and a lumped capacitor to excite currents for first and second order resonant modes of the ground. The resonant frequencies of both bands are controlled using a series combination of a capacitor and an inductor. The proposed design may be an attractive choice for mobile devices owing to its compact geometry and tunable operating frequencies. The measurement and simulation results of the proposed antenna show good agreement, indicating good impedance matching and radiation performance.

title: Efficient and tunable strip to slot fundamental mode coupling.
abstract: We present a novel photonic wire to slot waveguide coupler in SOI. The phase matching between a wire and slot mode is achieved using a mode transformer. The architecture consists of a balanced 50/50 power splitter and a tunable phase matched taper combiner forming a slot waveguide. We show a theoretical wire to slot coupling efficiency of 99 is achievable and experimentally, we demonstrate a coupling efficiency of 99 in the 1550 nm band. Based on the coupling scheme, we also show excitation of a slot mode in a slotted ring resonator and verified the excitation through the thermo optic response of the rings. We show a nearly athermal behaviour of a PMMA filled slot ring with a thermo optic response of 12.8 pm/degC compare to 43.5 pm/degC for an air clad slot waveguide.

title: Tunable slot loaded patch antenna for cognitive radio
abstract: This paper presents a reconfigurable microstrip patch antenna for cognitive radio applications. The antenna is fed by a coplanar waveguide via capacitive coupling slot. The antenna allows easy tuning of the resonant frequency by employing two switches and two capacitors inserted in the coupling slot. The resonant frequency of the antenna can be adjusted by activating the switches and/or varying the capacitors. The achievable tuning bandwidth is 1.7:1 and it extends from 1.39 GHz to 2.36 GHz. The structure has a compact and simple biasing circuit. The proposed antenna was verified through both electromagnetic simulation and measurement which indicate that it presents very good impedance matching, stable radiation patterns and good gain within the tuning bandwidth.

title: Compact and Tunable Slot Loop Antenna
abstract: A compact and tunable slot loop antenna is studied in this communication. By periodically loading the slot line with varactor diodes, the slow wave loop is capable of operating at frequencies from 2.34 GHz to 4 GHz with the measured input reflection coefficient better than 7.5 dB while occupying a small footprint of 0.072 lg x 0.072 lg (8.1 mm x 8.1 mm) where lg is the guided wavelength of a slot line at 2.34 GHz. The slot loop in the ground plane is excited by a simple microstrip line, which enables the impedance matching from 3.2 GHz to 4 GHz for VSWR 2. A LC low pass circuit is configured into the bias network to isolate the RF signal from the DC power path and consistent radiation patterns are experimentally obtained across the entire tunable frequencies of interest. The slot loop combined with the feed line and the bias circuitry is only 40 mm x 38.97 mm. Experimental results validate the feasibility of the presented antenna and agree well with simulation data.

title: Wideband Tunable PIFA Antenna with Loaded Slot Structure for Mobile Handset and LTE Applications
abstract: A compact planar inverted F antenna (PIFA) with a tunable frequency response is presented. Tuning of the resonant frequency is realized by loading a varactor on an embedded slot of the proposed antenna structure with out further optimizing other antenna geometry parameters. The antenna exhibits a wide frequency range from 1570 to 2600 MHz with a good impedance matching (S11 10dB) covering the GPS, PCS, DCS, UMTS, WLAN and LTE systems. To validate the theoretical model and design con cept, the antenna prototype was fabricated and measured. The compact size of the antenna is 15 mm x 8 mm x 3 mm, which makes this antenna a good candidate for mobile handset and wireless communication applications.

title: Integration of slot antenna with evanescent mode filter for tunable front end applications
abstract: An evanescent mode cavity filter integrated with a slot antenna is presented herein. Evanescent mode cavities are commonly used to design low loss filters due to their high quality (Q) factors and small size. The integration of the slot antenna and evanescent mode filter provides nearly zero transition loss with reduced size. The filter/antenna is designed at the center frequency of 8.56 GHz with a fractional bandwidth of 2.86% The center frequency of this filter/antenna is then tuned from 8.18 to 8.80 GHz by just changing the resonant frequency of the resonators. The impedance matching, filtering shape, and radiation pattern of the filter/antenna system are preserved across the entire tuning range.

title: Low Profile Independently and Concurrently Tunable Quad Band Antenna for Single Chain Sub 6GHz 5G New Radio Applications
abstract: This paper presents a quad band frequency agile antenna, with independent and concurrent frequency tunability in each band, for a tunable, concurrent, quad band single chain radio receiver for 5G New Radio (NR) More specifically, the antenna comprises of four planar slots etched in a ground plane and fed through a single microstrip feedline, without any impedance matching network. The structure is optimized to maximize isolation between the individual slots and their respective resonant frequencies. Furthermore, a novel high order harmonic suppression method is demonstrated, which controls the current distribution via creating a fictitious short circuit in the slot antenna enabling the antenna to achieve a much wider tuning range. Numerical simulations are verified using experimental implementation and measurements, with good agreement observed. The four slots resonate around the 830 MHz, 1.8 GHz, 2.4 GHz and 3.4 GHz frequency bands, which are independently tuned (using a varactor diode in each slot) to achieve tuning ranges of approximately 64% 66% 27% and 33% respectively. More importantly, the contiguous four bands covers a total frequency tuning from 0.6 to 3.6 GHz i.e. a tuning range of approximately 143% Finally, far field measurements are performed and the antenna is evaluated in over the air testbed (quad band radio receiver) which measures the Error Vector Magnitude performance for the individual channels. Good performance is observed, confirming acceptable isolation performance between the four bands. The data reported in this paper is available, from ORDA The University of Sheffield Research Data Catalogue and Repository, at https:/doi.org/10.15131/shef.data.11219000.v1.

title: An Electronically Steerable Parasitic Array Radiator (ESPAR) Using Cavity Backed Slot Antennas
abstract: The electronically steerable parasitic array radiator (ESPAR) is an inexpensive way to achieve beam steering. Planar ESPARs usually exhibit narrow fractional bandwidth (FBW) in terms of both impedance matching and beam squinting. Herein, an E plane three element ESPAR using cavity backed slot antennas is presented to demonstrate a wider FBW, i.e. 4% by investigating not only S11 but also beam squinting. It is found that a tunable load which uses a fixed inductor, a varactor, and a delay line can provide a much larger impedance tuning range compared to that without the inductor. This tunable load is critical to enhance the FBW by considering beam squinting. This ESPAR is able to scan from 26deg to 20deg in the E plane, operating around 5.15 GHz. The measured peak gain is between 5.52 and 6.05 dBi at all scan angles. The radiation patterns are measured at different scan angles in the E plane. In addition, they are measured at different frequencies to demonstrate the beam squinting performance.

title: Comparative analysis of tunable compact rotators
abstract: Three versions of two layer polarization plane rotators in a circular waveguide based on the internal fringing field interaction are considered. They work on the excitation of unusual eigen oscillations within the gap between a pair of peculiar four slot metal irises. The subjects for comparison were the range of rotation angles, the possibility to provide good matching, and the ability of rotators to be tuned by mutual iris to iris rotation. The best properties were found in the case of the conjugated planar chiral irises.