Local Microwave Research Articles

Active phase drift cancellation for optic-fiber frequency transfer using a photonic radio-frequency phase shifter.

We propose an active photonic phase drift cancellation scheme for frequency transfer over optical fiber based on a linear photonic RF phase shifter. The photonic RF phase shifter consists of a dual parallel Mach-Zehnder modulator and optical filter with the assistance of the local microwave signal. The phase drift induced by fiber transmission can be compensated by simply tuning the bias voltage of the modulator. The principle of the phase cancellation scheme based on the photonic phase shifter is demonstrated and validated experimentally by transferring a 0.5GHz reference signal over a 20km single-mode fiber with a root mean square jitter of less than 0.5ps.

Intravesical mitomycin C combined with local microwave hyperthermia in non-muscle-invasive bladder cancer with increased European Organization for Research and Treatment of Cancer (EORTC) score risk of recurrence and progression

To assess the activity of intravesical chemotherapy and local microwave hyperthermia (ICLMH) in increasing the disease-free interval (DFI) in patients with non-muscle-invasive bladder cancer (NMIBC) and treatment toxicity. Forty-two patients with a diagnosis of high-risk NMIBC, according to the European Organization for Research and Treatment of Cancer (EORTC) criteria, were treated with an intensive schedule of ICLMH using 40 mg mitomycin C. The treatment consisted of 4 weekly sessions, followed by 6 sessions delivered every 2 weeks, and by 4 monthly sessions, for a total of 14 sessions over 8 months. The DFIs before and after treatment were compared in each patient. The schedule was completed as planned by 32 patients (76.2 %). The percentage of disease-free patients the year before study was 14.9 % (95 % CI 5.5-28.8) versus 88.8 % (95 % CI 73.7-94.8) after ICLMH (p < 0.0001). Patient EORTC scores, multifocality, and tumour stage were all associated significantly and independently with a higher risk of recurrence after ICLMH treatment with HR of 41.1 (p = 0.01), 17.7 (p = 0.02), and 8.5 (p = 0.02), respectively. After a median follow-up of 38 months, 24 patients (57.1 %) did not show evidence of disease, whereas 13 patients (30.9 %) underwent disease recurrence and 5 patients (11.9 %) showed also stage progression. Toxicity consisted in grades 1 and 2 frequency, non-infectious cystitis, and haematuria. ICLMH significantly increases the DFI of NMIBC patients with high EORTC score for recurrence and progression. Toxicity of the intensive treatment schedule was generally mild.

Novel Applicators for Local Microwave Hyperthermia Based on Zeroth-Order Mode Resonator Metamaterial

It is demonstrated that a theory of zero-order mode resonator (ZOR) metamaterial (MTM) structure can be used for the development of a novel class of applicators for microwave thermotherapy, for example, for hyperthermia in cancer treatment or for physiotherapy. The main idea of creating such an applicator is to generate and radiate a plane electromagnetic (EM) wave into the treated biological tissue, at least in a certain extent. The main aim of this paper is to investigate whether an EM wave generated by ZOR MTM structure and emitted into the biological tissue can produce a homogeneous SAR distribution in the planes parallel to the applicator aperture and achieve a penetration depth approaching the theoretical limit represented by SAR distribution and penetration depth of an ideal EM plane wave. EM field distribution inside a virtual phantom of the treated region generated by the applicator that is based on the proposed ZOR MTM principle is investigated using a well-proven full-wave commercial simulation tool. The proposed applicator type shows both a low unwanted leaked electromagnetic field and a fairly homogeneous electric field in its aperture as well as in the virtual phantom of the treated region.

Linear and stable photonic radio frequency phase shifter based on a dual-parallel Mach–Zehnder modulator using a two-drive scheme

We theoretically and experimentally demonstrate a linear and stable photonic RF phase shifter based on a dual-parallel Mach-Zehnder modulator (DPMZM) using a two-drive scheme. To avoid the effect of the residual optical carrier and overcome the lowest frequency limit from the optical filter, a local microwave signal and a signal up-converted from the under-phase-shifted RF signal are applied to the two RF inputs of the DPMZM, respectively. A phase-shifted RF signal is generated by beating the two first-order upper sidebands located in the passband of the optical filter. A continuous and linear phase shift of more than 360° and power variation of less than ±0.15 dB at 1GHz are achieved by simply tuning the bias voltage of the modulator. A phase tuning bandwidth of more than 17MHz and phase drift of less than 0.5° within 2000s are also observed.

Observations of Ball-Lightning-Like Plasmoids Ejected from Silicon by Localized Microwaves.

This paper presents experimental characterization of plasmoids (fireballs) obtained by directing localized microwave power (<1 kW at 2.45 GHz) onto a silicon-based substrate in a microwave cavity. The plasmoid emerges up from the hotspot created in the solid substrate into the air within the microwave cavity. The experimental diagnostics employed for the fireball characterization in this study include measurements of microwave scattering, optical spectroscopy, small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Various characteristics of these plasmoids as dusty plasma are drawn by a theoretical analysis of the experimental observations. Aggregations of dust particles within the plasmoid are detected at nanometer and micrometer scales by both in-situ SAXS and ex-situ SEM measurements. The resemblance of these plasmoids to the natural ball-lightning (BL) phenomenon is discussed with regard to silicon nano-particle clustering and formation of slowly-oxidized silicon micro-spheres within the BL. Potential applications and practical derivatives of this study (e.g., direct conversion of solids to powders, material identification by breakdown spectroscopy (MIBS), thermite ignition, and combustion) are discussed.

Morphological changes during Geren carcinoma after cryoablation, a local microwave hyperthermia and their combination

A morphological and morphometric study of Guerin carcinoma after cryoablation, local microwave hyperthermia and their combination was performed. Combined exposure was associated with decreased adhesion of tumor cells, increasing the area of necrotic tissue and more expressed angionecrosis compared with independent use of cryoablation or microwave hyperthermia. The results suggest a more expressed degradation of the Guerin carcinoma tumor tissue by the combined use of low temperatures and microwave hyperthermia.

Нові підходи до корекції гіперактивності сечового міхура

The article analyzes the causes of hyperactive detrusory contractions, considered etiopathogenesis and treatment of patients with overactive bladder syndrome (OBS). Two groups of patients with overactive bladder syndrome were examined, analyzed etiology, pathogenesis and treatment. A new method for increasing the threshold sensitivity of spinal centers under the OBS by using the local lesions of the mucous membrane of the bladder by electrical coagulation or local microwave hyperthermia of the prostate are proposed. The high efficiency of these methods in dealing with OBS is shown.

Microwave ablation devices for interventional oncology

Microwave ablation is one of the several options in the ablation armamentarium for the treatment of malignancy, offering several potential benefits when compared with other ablation, radiation, surgical and medical treatment modalities. The basic microwave system consists of the generator, power distribution system and antennas. Often under image (computed tomography or ultrasound) guidance, a needle-like antenna is inserted percutaneously into the tumor, where local microwave electromagnetic radiation is emitted from the probe’s active tip, producing frictional tissue heating, capable of causing cell death by coagulation necrosis. Half of the microwave ablation systems use a 915 MHz generator and the other half use a 2450 MHz generator. To date, there are no completed clinical trials comparing microwave devices head-to-head. Prospective comparisons of microwave technology with other treatment alternatives, as well as head-to-head comparison with each microwave device, is needed if this promising field will garner more widespread support and use in the oncology community.

External application of Natrii sulfas and Radix et Rhizoma Rhei powders after local microwave treatment of incision fat liquefaction

External application of Natrii sulfas and Radix et Rhizoma Rhei powders after local microwave treatment of incision fat liquefaction

Non-contact characterization of printed resistors

In this work we demonstrate the use of a high resolution non-contact scanning microwave microscope for characterization of printed resistors. The resonant microwave probe operates at a frequency of 5.73 GHz and it is based on a dielectric resonator coupled to a gold-coated tungsten tip with radius of 200 μm protruding from a cavity wall. Direct print additive manufacturing was used to produce the resistive films. Non-contact measurements of the resonant frequency fr and quality factor Q of the resonant microwave probe at a standoff distance of 20 μm were performed. Quality factor images were obtained over a scan area of 160 μm × 1670 μm in steps of 10 μm. Measurements reveal that Q varies from 214 to 233 over the studied region. In this work, variations in Q are associated with non-uniformities on the resistor surface. The quality factor of the probe was also acquired as a function of the tip-sample distance and measured data was fitted to a polynomial equation. We converted Q images to sheet resistance images using the polynomial equation and the material resistivity (400 Ω/sq/mil). Using the proposed approach, we found that the average sheet resistance over the scan area is Rs = 1027 W/sq and that Rs variations up to 662 Ω/sq, due to non-uniformities in the resistor's thickness, were detected by the microwave microscope. The localized microwave characterization capability demonstrated by the non-contact microscope could be of interest for defect detection in printed microwave circuits.

Microwave assisted resonant domain wall nucleation in permalloy nanowires

We have designed a system to study microwave assisted domain wall nucleation in permalloy nanowires. We find a substantial decrease in the nucleation field when microwave fields are applied, in comparison to pulse fields. A clear resonance peak is observed in the frequency dependence of the nucleation field, which coincides with the uniform mode ferromagnetic resonance frequency. Owing to the well-defined nucleation process, the switching field distribution is small in contrast to previous reports. Our results show that localized microwave field provides an efficient tool for injecting domain walls into magnetic nanowires.

Localized Rapid Heating by Low-Power Solid-State Microwave Drill

This paper presents a theoretical and experimental study of a locally induced microwave-heating effect implemented by a low-power transistor-based microwave drill. A coupled thermal-electromagnetic model shows that the thermal-runaway instability can be excited also by relatively low microwave power, in the range ~ 10-100 W, hence by solid-state sources rather than magnetrons. Local melting then occurs in a millimeter scale within seconds in various materials, such as glass, ceramics, basalts, and plastics. The experimental device employs an LDMOS transistor in an oscillator scheme, feeding a miniature microwave-drill applicator. The experimental results verify the rapid heating effect, similarly to the theoretical model. These findings may lead to various material-processing applications of local microwave heating implemented by solid-state devices, including local melting (for surface treatments, chemical reactions, joining, etc.), delicate drilling (e.g., of bones in orthopedic operations), local evaporation, ignition, and plasma ejection (e.g., in microwave-induced breakdown spectroscopy (MIBS) for material identification).

Thermite powder ignition by localized microwaves

This paper presents a new method to ignite pure thermite powder by low-power microwaves (∼100W). In this method, the microwave energy is supplied locally to the powder. It creates a confined hotspot, and initiates a self-propagating combustion in the entire powder volume. The coupled thermal–electromagnetic interaction evolved within the powder prior to its ignition is simulated theoretically, taking into account the powder’s temperature-dependent parameters. The simulation results show a thermal-runaway instability and localized heating within a confined hotspot, induced mostly by the microwave’s electric-field component. The experimental setup employs accordingly an open-end applicator implemented by a miniature solid-state microwave-drill device inserted into the thermite powder as a local igniter. The experimental results show ignition within ∼3s at 2.1-GHz, 100-W microwave injection, in agreement with the theoretical model. The dependence of the minimal microwave power on the exposure time required to reach combustion is identified. Practical aspects and potential applications of this mechanism, such as rust conversion, energy production, and propulsion are indicated.

Effects of Local Microwave Diathermy on Shoulder Pain and Function in Patients With Rotator Cuff Tendinopathy in Comparison to Subacromial Corticosteroid Injections: A Single-Blind Randomized Trial

Single-blind randomized clinical trial, with a follow-up of 24 weeks. To determine the effects of hyperthermia via localized microwave diathermy on pain and disability in comparison to subacromial corticosteroid injections in patients with rotator cuff tendinopathy. Hyperthermia improves symptoms and function in several painful musculoskeletal disorders. However, the effects of microwave diathermy in rotator cuff tendinopathy have not yet been established. Ninety-two patients with rotator cuff tendinopathy and pain lasting for at least 3 months were recruited from the outpatient clinic of the Department of Orthopaedics and Traumatology, University Hospital, Rome, Italy. Participants were randomly allocated to either local microwave diathermy or subacromial corticosteroids. The primary outcome measure was the short form of the Disabilities of the Arm, Shoulder and Hand Questionnaire (QuickDASH). Secondary outcome measures were the Constant-Murley shoulder outcome score and a visual analog scale for pain assessment. At the end of treatment and at follow-up, both treatment groups experienced improvements in all outcome measures relative to baseline values. Changes over time in QuickDASH, Constant-Murley, and visual analog scale scores were not different between treatment arms. In patients with rotator cuff tendinopathy, the effects of localized microwave diathermy on disability, shoulder function, and pain are equivalent to those elicited by subacromial corticosteroid injections.

MICROWAVE CONTRAST IMAGING OF BREAST TISSUE FROM LOCAL VELOCITY ESTIMATION

This paper proposes a new method to display microwave images of breast tissue, based on estimation of local microwave velocity from time of ∞ight measurements. Its computational demands are low compared with tomography. It has two major components: 1) the estimation of the travel time of microwaves across the tissue between a set of antennae using a wavelet decomposition, and 2) the estimation of the microwave velocity fleld from the set of travel times using a low dimensional set of radial basis functions to model local velocity. The technique is evaluated in 2-D on clinical MR-based numerical breast phantoms incorporated in Finite-Difierence Time-Domain simulations. The basis functions, used with a regularisation scheme to improve numerical stability, reduce the dimensionality of the inverse problem for computational e-ciency and also to improve the robustness to error in velocity estimation. The results support previously published flndings that the wavelet transform is suitable for robust measurement of time of ∞ight even in clinically signiflcant simulations, and shows that the velocity contrast images can be constructed so difierent regions of breast tissue type can be distinguished. In particular, the presence of a tumour is clearly detected, demonstrating the potential of this approach for breast screening. Keywords: Biomedical signal processing; Microwave imaging; Image reconstruction.

Transport Properties of YBa2Cu3O7 Josephson Junctions at THz Frequencies

Abstract For application in a THz scanning microscope we employ Josephson junctions from the high-temperature superconductor YBa2Cu3O7 on a so called Josephson cantilever to measure the local microwave power density in the half space above a device under test. The Josephson junctions are prepared by pulsed laser deposition and argon ion etching on symmetric LaAlO3 30 ∘ -bicrystal substrates. To achieve high sensitivity at THz frequencies, a high I c R n product is required. Therefore, the Josephson junctions are operated on a cryo-cooler at low temperature of about 36 K under vacuum conditions. The high frequency characterization is accomplished in the near field of a Gaussian far infrared gas laser beam optically pumped by a CO2 laser. We use strong emission lines of formic acid at 762 GHz and 1.2 THz for the investigations and report on the electrical transport properties determined from the current-voltage characteristics of the Josephson junctions under influence of external magnetic field and far-infrared radiation.

Detachment of a Microwave-Excited Plasmoid From Molten Glass

The evolution of a plasmoid (fireball) ejected by localized microwaves from a solid substrate is presented. The plasmoid is first fed by the substrate material (glass in this case) through a plasma column, which is detached from the substrate, and then evolves as a stable fireball buoyant in the air atmosphere. The experimental characterization of these fireballs is presented, and their resemblance to the ball lightning in nature is indicated.

Short-term effects of local microwave hyperthermia on pain and function in patients with mild to moderate carpal tunnel syndrome: a double blind randomized sham-controlled trial

Objective: To determine the short-term effects of local microwave hyperthermia on pain and function in patients with mild to moderate idiopathic carpal tunnel syndrome. Design: Double-blind randomized sham-controlled trial. Setting: Outpatient clinic of the Department of Physical Medicine and Rehabilitation, University Hospital. Participants: Twenty-two patients with idiopathic carpal tunnel syndrome, 12 of whom had bilateral involvement, for a total of 34 wrists, divided into two groups: a hyperthermia active treatment group (number of wrists = 17) and a sham-controlled group (number of wrists = 17). Intervention: Six sessions, two per week, of either hyperthermia or sham treatment were provided over a period of three weeks. Main measures: Visual analogue scale, Levine–Boston Self-Assessment Questionnaire (part I: evaluation of pain intensity; part II: evaluation of functional status) and neurophysiological assessments, were determined at baseline and at the end of the treatment. Results: The hyperthermia group experienced a significant improvement in pain (visual analogue scale: P = 0.002; Levine–Boston part I: P < 0.0001) and functional status (Levine–Boston part II: P = 0.002) relative to baseline. No improvements in pain intensity or functionality were observed in the sham-treated group. Changes in pain severity between baseline and the end of treatment were larger in the hyperthermia group than in the sham-controlled group (Δ visual analogue scale P = 0.004; Δ Levine–Boston part I: P = 0.009). No differences either intra or between groups were observed for median nerve conduction velocity. Conclusion: Hyperthermia provides short-term improvements in pain and function in patients with mild to moderate carpal tunnel syndrome.

Rapid internal bubble formation in a microwave heated polymer observed in real-time by X-ray scattering

A combined study of small-angle and wide-angle X-ray scattering (SAXS/WAXS) of the melting of a nylon-6 sample by localized microwave radiation has shown that this method can reveal the presence of bubbles forming and disappearing rapidly in real time in the interior of the sample due to its thermal decomposition.

Breakdown spectroscopy induced by localized microwaves for material identification

AbstractThis letter introduces a localized microwave technique for direct excitation of solid materials for the sake of their identification by atomic emission spectroscopy. The microwave energy is concentrated on the material surface by a microwave‐drill type applicator. The evolved ∼1‐mm3 hotspot is slightly evaporated and excited as plasma. An optical spectrometer measures the atomic emission spectrum, hence enabling the material identification as in the known laser‐induced breakdown spectroscopy (LIBS) technique. The experimental results demonstrate the conceptual feasibility of the localized microwave‐induced breakdown spectroscopy as a low‐cost substitute for the laser‐based LIBS for material identification in scenarios in which a direct contact with the material to be identified and its slight destruction are permitted. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2281–2283, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26272