Independent Frequency Tuning Research Articles

A High-Isolation SIW Self-Octaplexing Antenna With Independent Frequency Tuning Capability

A High-Isolation SIW Self-Octaplexing Antenna With Independent Frequency Tuning Capability

A high‐integration dual‐resonance element with independent frequency tuning for wideband reflectarrays

AbstractIn this letter, a novel design methodology of dual‐resonance elements for wideband reflectarrays is proposed for the first time. The alluring merits of this design lie in the compact common‐via dual‐resonance element with weak inner coupling and independent frequency tuning. To improve compactness, a traditional dipole is terminated by a metallic via connected to the ground plane. The element operates in monopole mode, decreasing the size by half. To realize a high‐integration dual‐resonance element, two monopoles operating at different frequencies are adopted to construct an asymmetric common‐via element, with an equivalent size to the traditional dipole resonating at merely one frequency. The first‐ever proposed element embodies superiorities of compactness, independent frequency tuning, and low profile. The proof‐of‐concept is validated by a fabricated reflectarray. The elaborately designed element with a compact size of 0.42 λ × 0.105 λ × 0.0737 λ exhibits an extended phase range of 484° at 14 GHz. The measured 3‐dB gain bandwidth is 36% (12.5–18 GHz) with a maximum gain of 26.9 dBi. The design strategy is capable of integrating more resonant structures in a compact area, rendering it suitable for broadband reflectarrays.

Compact SIW-Based Self-Quadruplexing Antenna for Microwave and Mm-Wave Communications

A compact self-quadruplexing antenna is presented, using substrate-integrated waveguide (SIW) technology and operating at 5.8, 7.4, 28, and 38 GHz. The design process is based on bisecting diagonally a square cavity into two triangles to obtain two HMSIW cavities. The right-upper corner of the structure is separated by slots to incorporate mm-wave frequencies. By utilizing five capacitive slots, independent frequency tuning in the operating frequency bands is achieved. To the best of our knowledge, this is the most compact quadruplexing antenna in the literature that operates at both mm-wave and microwave frequencies, and it has the best isolation between ports. The size of the antenna is 0.25 λg2 and the isolation between ports is less than -26 dB. A prototype of the antenna is fabricated and measured, showing a good agreement with the simulations, and therefore confirming the design approach.

Substrate Integrated Waveguide-Based Full-Duplex Antenna With Improved Out-of-Band Suppression

This brief presents a self-diplexing antenna with harmonic-suppression capability. The suggested antenna operates at 7.8 and 9 GHz and maintains a harmonic suppression of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.17f_{1}$ </tex-math></inline-formula> (where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{1}$ </tex-math></inline-formula> is the lower resonant frequency.) The isolation between two ports is more than 22 dB. The substrate-integrated waveguide (SIW) is used in the construction of the cavity-backed planar duplexing antenna. Starting from a microstrip patch antenna with undesirable high-frequency harmonics, a series of vias are used to suppress those harmonics. Finally, a slot (rotated over 45°) is used to bring the higher order mode to lower frequencies. Moreover, the size reduction in this design is achieved using capacitive slots. Consequently, the proposed antenna suppresses the second, third and fourth harmonics by using two pairs of slots and shorting pins. Besides having a low-profile and offering harmonic suppression, it provides independent frequency tuning in the operating frequency bands by means of capacitive slots. The proposed antenna is built and tested, displaying a reasonable match between the simulation and measurement performances, in this way validating the suggested concept.

Multi-resonant open-access microcavity arrays for light matter interaction.

We report the realisation of a high-finesse open-access cavity array, tailored towards the creation of multiple coherent light-matter interfaces within a compact environment. We describe the key technical developments put in place to fabricate such a system, comprising the creation of tapered pyramidal substrates and an in-house laser machining setup. Cavities made from these mirrors are characterised, by laser spectroscopy, to possess similar optical properties to state-of-the-art fibre-tip cavities, but offer a compelling route towards improved performance, even when used to support only a single mode. The implementation of a 2×2 cavity array and the independent frequency tuning between three neighbouring sites are demonstrated.

Reconfigurable Full-Metal Circularly-Polarized Cavity-Backed Slot Antenna and Array With Frequency and Polarization Agility

In this brief, reconfigurable circularly-polarized (CP) cavity-backed slot antenna (CBSA) and antenna array with frequency and polarization agility are proposed. Two degenerate modes TE101 and TE011 are respectively perturbed by the metal posts along y-axis (named as MP-1) and x-axis (named as MP-2), and independent frequency tuning is obtained. Then, two crossed slots are placed on the top wall to radiate the electromagnetic energy of TE101 and TE011 modes, respectively. In this context, circular polarization can be realized by setting different lengths of MP-1 and MP-2. Besides, reconfigurable polarization between left-hand and right-hand circular polarization can be realized by exchanging the lengths of MP-1 and MP-2. Meanwhile, reconfigurable operating frequency can be realized by simultaneously increasing or decreasing the lengths of MP-1 and MP-2. In addition, a reconfigurable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4{\times }4$ </tex-math></inline-formula> CP array without introducing power dividers and without increasing the number of tuning metal posts is further investigated. Finally, the reconfigurable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4{\times }4$ </tex-math></inline-formula> CP array is fabricated and tested. Reconfigurable frequency, reconfigurable polarization, high total efficiency, and stable radiation pattern are simultaneously obtained. Good agreement between measured and simulated results well validates the proposed design concept.

A Compact SIW Cavity-Backed Self-Multiplexing Antenna for Hexa-Band Operation

In this communication a compact planar-fed substrate integrated waveguide (SIW)-based self-multiplexing (SM) antenna for hexa-band operation is proposed for the first time. Six different patches with planar <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\Omega $ </tex-math></inline-formula> feed lines are designed and attached to the top side of the rectangular SIW cavity. The antenna operates at six different frequencies (5.33, 5.76, 6.31, 6.86, 7.34, and 7.8 GHz) simultaneously. The antenna attains 4.5, 4.94, 4.9, 5.12, 6.12, and 6.6 dBi peak gain at respective resonant frequencies. Port relocation, stepped patches, and additional vias are exploited to maintain isolation (>23 dB) between any two ports. The front-to-back ratios (FTBRs) are between 10 and 20 dB and Co-pol to Cross-pol ratios are between 10 and 29 dB. The design supports single-variable independent frequency tuning for all six patches and eligible for wide range of applications. The proposed design is fabricated and results are validated through measurement. The antenna is suitable for planar microwave devices.

Narrowband photon pairs with independent frequency tuning for quantum light-matter interactions.

We describe a cavity-enhanced spontaneous parametric down-conversion (CE-SPDC) source for narrowband photon pairs with filters designed such that 97.7% of the correlated photons are in a single mode of 4.3(4) MHz bandwidth. Type-II phase matching, a tuneable-birefringence resonator, MHz-resolution pump tuning, and tuneable Fabry-Perot filters are used to achieve independent signal and idler tuning. We map the CE-SPDC spectrum using difference frequency generation to precisely locate the emission clusters, demonstrate CE-SPDC driven atomic spectroscopy, and measure a contribution from unwanted modes of 7.7%. The generated photon pairs efficiently interact with neutral rubidium, a well-developed system for quantum networking and quantum simulation. The techniques are readily extensible to other material systems.

A Compact Frequency-Reconfigurable Antenna With Independent Tuning for Hand-Held Wireless Devices

This communication presents the design of a compact loop antenna with independent frequency tuning. The proposed antenna consists of a feed line fed by a $50~\Omega $ coaxial probe and four resonating arms on the adjacent sides of the feed line. The two outer resonating arms are directly coupled to the feed line and the other two inner resonating arms are coupled to the outer arms. The proposed antenna has a footprint of 25 mm $\times 10$ mm $\times0.2$ mm. The designed antenna operates at 0.9, 2.4, 3.5, and 5.5 GHz. Each of these bands is individually tuned using varactor diodes. Thus, the aggregation of these tunable bands provides wide bandwidth. The impedance bandwidth and percentage bandwidth of the antenna are 270/1000/400/700 MHz and 33%/47.6%/11%/12.7%, respectively. Furthermore, the gain and efficiency of the antenna are 1.7/1.3/2.1/2 dBi and 60%/63%/65%/69%, respectively. The prototype antenna is fabricated and tested. The measured impedance and radiation characteristics of the antenna are in good correlation with the simulation results.

Highly Reconfigurable Dual-Band Coupler With Independently Tunable Operating Frequencies

To support different standards simultaneously within a wireless communication system, research on dual-/multi-band components has been conducted extensively. However, the operating frequencies of existing works are usually fixed resulting in a low flexibility. To solve this problem, a highly reconfigurable coupler whose two operating frequencies can be controlled independently is proposed for the first time in this paper. Based on the analysis of a basic configuration, the conditions for realizing the desired independent frequency tuning can be obtained. To realize this unique property, varactors loaded coupled line sections are introduced on a conventional branch line coupler. Owing to the symmetrical structure of the proposed coupler, explicit theoretical analysis can be conducted. For demonstration, two reconfigurable couplers are designed, fabricated, and measured. The first coupler can provide frequency tunability from 3.4 to 4.2 GHz at the upper band with the lower band fixed at 2.4 GHz. The other one can not only provide a tunable frequency from 1.3 to 1.6 GHz at the lower band with the higher band fixed at 3.4 GHz, but also give a tunable higher band from 2.9 to 3.4 GHz with the lower band fixed at 1.55 GHz. The measured results agree well with the simulated results, validating the proposed design methodologies.

Design of a compact triple band antenna with independent frequency tuning for MIMO applications

In this article, a planar, low profile microstrip line-fed triple band multiple input multiple output (MIMO) antenna is presented for WiMax (2.5/3.5/5.5 GHz)/WLAN (2.4/3.6/5.8 GHz) applications simultaneously. The single element of the MIMO antenna consists of (i) a rectangular split ring resonator (SRR), (ii) a stepped impedance resonator (SIR) inside the SRR and (iii) a slot on the SIR. Each of the resonators generates its own individual band and each band is independently tunable. The antenna exhibits three operating bands at 2.35-2.85 GHz, 3.25-3.90 GHz and 5.45-5.65 GHz. Four antenna elements are used to design the proposed MIMO antenna. The simulated results are observed and reported in terms of S-parameters, gain, radiation patterns, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL) and total active reflection coefficient. ECC and CCL are within the acceptable range defined for 4G and 5G application standards. To validate the simulation results a prototype structure is fabricated and the measured results are compared with those obtained from the simulation.

Design of a compact quad‐band antenna with independent frequency tuning

A compact, planar, low profile microstrip line-fed quad-band antenna is presented with operating frequencies at 2.5/3.6/5.5/7.5 GHz. The antenna consists of a rectangular split-ring resonator (SRR), a stepped impedance resonator (SIR) inside the ring, a slot on the SIR and a pair of SRRs either side of the matching network. Each of the resonators generates its own individual band which is independently tunable. The antenna is compact in size having dimensions 0.10λ0 × 0.13λ0. The radiation patterns are omnidirectional and bilateral in the H-plane and the E-plane, respectively, at all the resonance frequencies. The simulated results are observed and reported in terms of S-parameters, gain and radiation patterns. A prototype structure is fabricated and the measured results are compared with those obtained from the simulation.

Unidirectional Dual-Band Stacked Patch Antenna With Independent Frequency Reconfiguration

A novel dual-band frequency-reconfigurable stacked patch antenna is presented. The antenna comprises two stacked square patches. Each patch is divided into two rectangular portions by a gap, and a pair of varactor diodes is introduced to bridge the gap. By changing the reverse bias voltages across the two pairs of varactor diodes, the antenna can operate at dual frequency bands with independent frequency tuning. A fully functional prototype is fabricated and characterized. It exhibits a continuously dual frequency-tunable characteristic, from 1.68 to 1.93 GHz for the low band and from 2.11 to 2.51 GHz for the high band. Well-controlled unidirectional radiation patterns are achieved at all operating frequencies. To the best knowledge of the authors, this is the first dual-band reconfigurable patch antenna with an independent frequency tuning ability. The dual-band frequency selective feature makes the antenna potentially suitable for future wireless communication systems, such as cognitive radio.

Tunable 4-Pole Dual-Notch Filters for Cognitive Radios and Carrier Aggregation Systems

This paper presents 4-pole tunable dual-notch filters with independent frequency tuning for each notch response based on a stub-loaded resonator with asymmetrical loading capacitances. The resonator is designed based on lumped notch filters, and is folded on a three-layer $\varepsilon_{\bf r} = 3.55$ board for compact filter size. Frequency tuning is achieved using silicon varactor diodes. The first filter (Filter A) results in measured rejection of 47–53/49–52 dB at 0.71–1.01/1.10–1.45 GHz. The second filter (Filter B) shows rejection levels of 42–48/34–39 dB at 0.76–1.05/1.80–2.12 GHz. Also, tuning in one band has virtually no effect on the other band, showing high isolation between the two notches. Application areas are in cognitive radios and carrier aggregation systems with two transmit frequencies.

Stub‐loaded bent monopole antenna with independent frequency tuning capability for compact wireless USB dongles

AbstractIn this article, compact monopole antenna with independent resonant frequency tuning capability is proposed.The antenna radiating patch consists of a simple, bent monopole element and an open stub. The bent monopole acts as a main radiator in 2.5 GHz band, whereas the open stub serves in 5.5 GHz band. A prototype of the proposed antenna was fabricated, and the reflection and radiation characteristics were measured to validate the antenna performances. Measured impedance bandwidths (VSWR &lt; 2) exhibits dual‐broadband resonances, which are 2.08–3.02 GHz (lower band) and 5.13–6.15 GHz (upper band), corresponding to 36.9 and 18.1%, respectively. Therefore, VSWR bandwidth of the proposed design covers not only the WiBro, WiMAX, Bluetooth, 2.4 GHz WLAN, S‐DMB, but also the 5.2/5.8 GHz WLAN services. The peak gain was 5.76 dBi. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2548–2552, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27159

Frequency adjustable microstrip annular ring patch antenna with multi-band characteristics

This study introduces a frequency-tunable dual-band microstrip annular ring patch antenna design for wireless local area network (2.45 GHz) and Worldwide Interoperability for Microwave Access (3.5 GHz) applications. The proposed antenna produces realisable gain higher than 5 dBi and return loss better than 10 dB for the stated applications. The antenna design consists of an annular ring patch loaded with a slot or gap. This loaded ring excites higher-order modes around the dominant mode (TM11) of the annular ring thus making this design capable of dual-band operation. This design is realised on a 1.57 mm thick polytetrafluoroethylene substrate using a coaxial probe feed. In this study, a novel technique for independent frequency tuning has also been introduced by cutting grooves on the periphery of the ring at the desired locations. Furthermore, the design capability of multi-band operation (2.45 GHz/3.5 GHz/5.5 GHz) has also been explained in the later part of the study. Antenna operation has been verified with the help of two commercially available EM solvers (CST Microwave Studio and Ansoft HFSS Designer) and measurements. A close agreement has been found between the simulated and the measured results.

A Differential Dual-Polarized Cavity-Backed Microstrip Patch Antenna With Independent Frequency Tuning

A dual-polarized cavity-backed microstrip patch antenna has been demonstrated with independent tuning of both polarizations from 0.6 GHz to ~1.0 GHz using varactor diodes (1.2-5.4 pF). The 10-dB impedance bandwidth varies from 0.9% to 1.8% over that range. Differential coaxial feeds and the placement of the tuning varactors in the appropriate symmetry planes are employed to achieve a differential-mode port-to-port isolation of >28 dB over the tuning range. Accordingly, the cross-polarization level is <; -20 dB at broadside. The antenna is 100 × 100 × 6.4 mm3 and is fabricated on a dielectric substrate (er = 2.2). The feed point and matching circuit for an impedance match to 50 Ω are determined using the transmission line model. This model underestimates the sensitivity of the resonance frequency to the loading capacitance, but leads to a good initial design. To the authors' knowledge, this is the first dual-polarized antenna with independent tuning over a 1.7:1 bandwidth and single-sided radiation.

A Tunable Quadrature Oscillator with Only TransconductanceElements and Grounded Capacitors

A novel quadrature oscillator is realised with only transconductance elements (TEs) and grounded capacitors. The realised quadrature oscillator uses only two inverting and two non‐inverting transconductance elements, along with two grounded capacitors. The quadrature oscillator enjoys the attractive features of low component count, independent frequency tuning and suitability for integration in MOS technology.