ELECTRONICALLY STEERABLE ARRAY

In many laser scan engines, mechanical inertia imposes a tradeoff between mirror diameter (mass) and scan speed (cycle time) and/or scan angle amplitude. Ultimately, this limits the field-of-view and/or scan speed in multiphoton and confocal imaging, laser-based manufacturing, and other applications. To push parameters past this inertia limit, we present a non-inertial (stationary) add-on unit that doubles the scan angle amplitude while preserving both the beam size and cycle time, thus doubling the étendue (optical invariant) and overall system throughput. We demonstrate its use in two-photon calcium imaging of neural activity in living mice. We also adapt the approach to present a phase-doubling unit that doubles the maximum range of phase modulators. Finally, we describe further variants, including generalizing the approach to Nx scan angle multiplication (N=2,3,4,…) with diffraction-limited performance across a wide scan angle range and over a broad wavelength bandwidth. These non-inertial scan angle multipliers (called Nisam2x, 3x,…) fundamentally break the inertia-imposed tether between scan speed and scan angle amplitude, enabling expanded capabilities of a range of technologies, including imaging, adaptive optics, sensing, marking, and manufacturing.

The ion source for the Spallation Neutron Source (SNS) is a radio-frequency, multicusp source designed to deliver H− beam pulses of 45 mA to the SNS accelerator, with a pulse length of 1 ms and a repetition rate of 60 Hz. In order to achieve this performance the source must operate with both high peak rf power, ∼45 kW, and high average rf power, ∼3 kW, over an operational run period of 3 weeks. The most critical source component in this respect is the plasma-immersed, porcelain coated rf antenna which can be susceptible to damage during high power operation. The DESY group has developed an external antenna configuration utilizing an Al2O3 plasma chamber which has demonstrated a very long operational period exceeding 25 000 h. Their source operates with peak rf powers comparable to the SNS source but with greatly reduced average rf powers, ∼50 W. In order to explore the applicability of this external antenna concept to high average power ion sources like the SNS source, we have performed thermal, mechanical, and electromagnetic analyses of the Al2O3 plasma chamber. This article discusses the final design which has resulted from these studies as well as estimates of the power limitations of such devices.

We report the synthesis and excited-state dynamics of a series of five bichromophoric light-harvesting antenna systems, which are capable of efficient harvesting of solar energy in the spectral range of 350-580 nm. These antenna systems have been synthesized in a modular fashion by the covalent attachment of blue light absorbing naphthalene monoimide energy donors (D1, D2, and D3) to green light absorbing perylene-3,4,9,10-tetracarboxylic acid derived energy acceptors, 1,7-perylene-3,4,9,10-tetracarboxylic tetrabutylester (A1), 1,7-perylene-3,4,9,10-tetracarboxylic monoimide dibutylester (A2), and 1,7-perylene-3,4,9,10-tetracarboxylic bisimide (A3). The energy donors have been linked at the 1,7-bay-positions of the perylene derivatives, thus leaving the peri positions free for further functionalization and device construction. A highly stable and rigid structure, with no electronic communication between the donor and acceptor components, has been realized via an all-aromatic non-conjugated phenoxy spacer between the constituent chromophores. The selection of donor naphthalene derivatives for attachment with perylene derivatives was based on the effective matching of their respective optical properties to achieve efficient excitation energy transfer (EET) by the Förster mechanism. A comprehensive study of the excited-state dynamics, in toluene, revealed quantitative and ultrafast (ca. 1 ps) intramolecular EET from donor naphthalene chromophores to the acceptor perylenes in all the studied systems. Electron transfer from the donor naphthalene chromophores to the acceptor perylenes has not been observed, not even for antenna systems in which this process is thermodynamically allowed. Due to the combination of an efficient and fast energy transfer along with broad absorption in the visible region, these antenna systems are promising materials for solar-to-electric and solar-to-fuel devices.

A simple UWB microstrip monopole antenna with reconfigurable multi band function is presented. Reconfigurability is achieved by using multiple switches to control the length of different printed stubs. Reflection coefficient, radiation patterns and gain measurements are presented to verify the simulations. Finally the total efficiency of the antenna is characterized and it is compared to the total efficiency of the original UWB antenna.

This paper discusses smart antennas for space-borne synthetic aperture radar (SAR). First, some recent development in smart antennas for space-borne SAR is reviewed. Then, the paper presents a low-cost space-borne SAR system using digital beam forming on receive. The smart antenna system is also discussed, and some results are shown. The antenna system, consisting of a parabolic reflector and multi-feed array, is designed and optimized for dual-band dual-polarized digital beam-forming performance. The operating frequencies are at X and Ka bands with the center frequency of 9.6 and 35.75 GHz, respectively. The stacked dipoles and square patches with parasitic elements are employed as the feed elements at X and Ka bands. Dual-band antenna arrays are combined in the same aperture, which not only reduce the aperture of the feed array, but also coincide the center of dual-band feed arrays.

This paper presents a design approach of Doherty amplifier, which is based on optimizing the average power efficiency instead of peak power efficiency by adjusting the offset lines located in the branches of the carrier and the peak amplifier. The back-off point of the Doherty amplifier, which can be shifted by tuning the offset lines, should be optimized according to the power probability distribution of the modulated signal so as to achieve the maximum average power efficiency. A Doherty amplifier is designed using Freescale's MRF281S 4-W LDMOS FETs and the test signal is a TD-SCDMA signal at 2017.5MHz. The validation result of the Doherty amplifier show that the average power efficiency is 31.2 % at 9dB back-off point. The power efficiency enhances 4.2% and 3.9%, respectively, comparing with 27% at the 6dB back-off point and 27.3% at the 13 dB back-off point.

A novel approach to wide-band antenna gain measurement is presented in this article, offering practical solutions to address the challenges posed by traditional measurement methods. The proposed system enhances efficiency, reduces complexity, and improves accuracy, making it a valuable tool for antenna testing in research and industry settings. A discussion of the challenges and complexities involved in measuring the specifications of manufactured antennas is made. We are particularly focusing on wide-band antenna gain measurement. It highlights the need for special equipment and expertise to conduct these tests effectively, especially for wide-band antennas. The proposed automated measurement system aims to simplify and streamline the gain measurement process by remotely driving the necessary instruments and reducing the complexity of the measurement mechanism. The novelty of this new automated measurement system can be divided into two branches. The first branch improves the standard approach of wide-band antenna gain measurement. The second branch modifies the structure of the software of the traditional remote access applications by mixing the operational instructions of the instrument with the direct SCPI commands. The resulting software has the ability to remotely drive many instruments synchronically, reducing the number of experienced people needed to complete the measurement process.

This systematic review explores recent advancements in antenna and rectifier systems for radio frequency (RF) energy harvesting within the gigahertz frequency range, aiming to support the development of sustainable and efficient low-power electronic applications. Conducted under the PRISMA methodology, our review filtered 2465 initial records down to 80 relevant studies, addressing three research questions focused on antenna design, operating frequency bands, and rectifier configurations. Key variables such as antenna type, resonant frequency, gain, efficiency, bandwidth, and physical dimensions were examined. Antenna designs including fractal, spiral, bow-tie, slot, and rectangular structures were analyzed, with fractal antennas showing the highest efficiency, while array antennas exhibited lower performance despite their compact dimensions. Frequency band analysis indicated a predominance of 2.4 GHz and 5.8 GHz applications. Evaluation of substrate materials such as FR4, Rogers, RT Duroid, textiles, and unconventional composites highlighted their impact on performance optimization. Rectifier systems including Schottky, full-wave, half-wave, microwave, multi-step, and single-step designs were assessed, with Schottky rectifiers demonstrating the highest energy conversion efficiency. Additionally, correlation analyses using boxplots explored the relationships among antenna area, efficiency, operating frequency, and gain across design variables. The findings identify current trends and design considerations crucial for enhancing RF energy harvesting technologies.

5 - Beamformers

본 논문에서는 상용 초고주파 MEMS 스위치를 이용하여 세 개의 주파수 대역에서 재구성 동작이 가능한 주파수 재구성 능동 배열 안테나 시스템(Reconfigurable Active Array Antenna System: RAA System)을 제안하였다. MEMS 스위치는 삽입 손실 및 선형성 특성이 우수하고 격리도가 높아 주파수 재구성 시스템 구현 시, 재구성을 위한 스위치로 인한 성능 열화가 거의 없다는 장점이 있다. 제안된 주파수 재구성 능동 배열 안테나 시스템은 간단한 구조의 임피던스 매칭 회로(Reconfigurable impedance Matching Circuit: RMC)를 갖는 주파수 재구성 증폭기(Reconfigurable Front-end Amplifier: RFA)가 집적화 되어 있으며, 안테나 방사체(Reconfigurable Antenna Element: RAE)와 재구성 제어 보드(Reconfiguration Control Board: RCB)로 구성되어 있다. 본 논문에서 제안한 RAA 시스템은 850 MHz, 1.9 GHz, 3.4 GHz의 세 개 주파수로 재구성되어 동작하며, 안테나 방사체는 <TEX>$2{\times}2$</TEX> 배열을 가지고 각각의 방사체는 광대역 다이폴 형태를 갖는다. 제작된 RAA 시스템은 실험을 통하여 그 타당성을 확인하였다. In this paper, a novel frequency reconfigurable active array antenna(RAA) system, which can be reconfigurable for three reconfigurable frequency bands, is proposed by using commercial RF MEMS switches. The MEMS switch shows excellent insertion loss, linearity, as well as isolation. So, the system performance degradation of the reconfigurable system by using MEMS switches can be minimized. The proposed frequency reconfigurable active antenna system is consisted with the noble frequency reconfigurable front-end amplifiers(RFA) with the simple reconfigurable impedance matching circuits(RMC), reconfigurable antenna elements(RAE), as well as a reconfiguration control board(RCB) for MEMS switch control. The proposed RAA system can be reconfigurable for three frequency bands, 850 MHz, 1.9 GHz, and 3.4 GHz, with <TEX>$2{\times}2$</TEX> array of the RAE having broadband printed dipole antenna topology. The validity of the proposed RFA as well as RAA is also presented with the experimental results of the fabricated systems.

A Microstrip antennas have specific characteristics such as a low profile, low volume, little power consumption, concentration, and easy manufacture. Due to these capabilities, Microstrip antennas can overcome rising wireless communication requirements such as high gain, high power, high performance and low losses. Since it can be printed directly onto a circuit board, microstrip antennas are becoming more common. Cell phones are increasingly utilizing microstrip antennas. Antenna designs proposed in literature are on big in size. The antenna structure's operating bandwidth should be greater than the structures suggested in the literature sample. Usually, the antenna structure's fractional bandwidth should be greater than 100%. The structure's total dimensions should be as minimal as possible. The structure's total measurements will be 25x25x1.5 mm3. The antenna system should be able to radiate more signals thus minimizing losses caused by surface waves. The structure's targeted radiation efficiency should be greater than 50%. The structure must be fabricated on a low-cost FR4 substrate that is commercially available in lower cost. The proposed work aimed at improving the efficiency of the microstrip antenna would be ideal for Wi-Fi, WiMAX, WLAN, and other UWB wireless networking applications.

Thin-film high-temperature superconductors (HTS) have found use in many different applications since their discovery in 1986. Their popularity is due in great put to the advances in deposition technology, which has provided high-quality films on a variety of substrates. For the most part, the primary advantage of using superconducting materials in antenna systems is the reduction of the loss associated with transmission line matching circuits, filters, and feed networks particularly at microwave and millimeter-wave frequencies where ohmic losses begin to significantly affect the system's performance. For large antenna arrays with long, elaborate corporate feed networks, the use of HTS transmission lines can substantially increase the gain of the antenna arrays. The efficiency of the individual microstrip patch antennas is limited by the power dissipated by ohmic losses in the patch element and ground plane, the dielectric loss in the supporting substrate, and the undesirable excitation of surface-wave radiation. Because the surface-wave excitation increases with increasing substrate thickness and permittivity, the substrate upon which the microstrip antenna is patterned is typically electrically thin (less than 0.01/spl lambda//sub 0/). Unfortunately, there is a substantial decrease in the radiation efficiency on thin substrates, which is due to the conductor and dielectric loss. These losses can be significantly reduced by constructing the antenna from thin films of HTS materials on low-loss substrates. We summarize our efforts in investigating the properties of superconducting microstrip patch antennas.

Satellite communication (SATCOM) on-the-move applications require low-cost compact antenna arrays to enable mobile users to track the satellites. Full-duplex operation requires efficient diplexers that satisfy stringent requirements in a compact footprint to enable tight integration within the antenna system. In this contribution, substrate-integrated-waveguide technology is leveraged to design a single-layer third-order diplexer filter based on a dual-mode cavity. Simulations and measurements demonstrate that the diplexer enables full-duplex operation for Ku-band SATCOM on-the-move systems, effectively separating the [11.7-12.75] GHz downlink (Rx) band from the [13.75-14.50] GHz uplink (Tx) band, yielding an isolation larger than 20 dB and an insertion loss below 3.7 dB over a fractional bandwidth (FBW) of 8.6% in Rx and 5.3% in Tx.

ABSTRACTIn this paper, a design procedure of a compact broadband microstrip diplexer working on the Very High Frequency (VHF)/Ultrahigh Frequency (UHF) band is proposed. The diplexer consists of a fourth‐order Butterworth Low‐Pass Filter (LPF) and a sixth‐order elliptic High‐Pass Filter (HPF). The two filters are located on two substrates with a common ground. A microstrip‐to‐coaxial structure is utilized to transmit the power flow between the two substrates. For miniaturization, the utilized ideal capacitors and inductors are realized by the commercial lumped‐element capacitors and the curved microstrip line sections, respectively. All the middle design and rapid optimization processes from the schematic simulation by Advanced Design System (ADS) to the circuit simulation by CST STUDIO SUITE (CST) are given in the article. A prototype is fabricated and measured. The testing results are consistent with the simulation. The diplexer can operate at 225–775 and 880–2500 MHz. The insertion losses are 0.8 ± 0.3 and 0.9 ± 0.4 dB in the two working bandwidths. The isolation bandwidth of −20 dB level is as small as 105 MHz. The roll‐off is also sharp that the related bandwidths corresponding to the attenuation level −3 to −20d B are 90 and 30 MHz to the high and low bands, respectively. Besides, the return loss and isolation are larger than 10 and 20 dB approximately. The diplexer has a volume of 0.065 λg × 0.156 λg @775 MHz, which can be utilized to feed the miniaturized broadband VHF/UHF antenna system.

For Reflector Antenna (Prime focus/ Cassegrain) is very important to know its overall antenna efficiency (the combination of aperture, spillover, feed efficiency), system temperature, and Sensitivity (in terms of G/Tsys). It is very difficult to Design a feed that has proper radiation pattern that gives good overall efficiency and minimum ground temperature, similarly for the receiver chain it is very difficult to get proper combination that gives minimum receiver temperature. For all this difficulty in the Reflector antenna we design and developed a software named RASCAL (Reflector Antenna Sensitivity CALculator). This software gives a quick response to the feed designer go or no go means the feed is suitable for the specific reflector similarly for RF engineer it will suggest that what are combinations will give lower receiver temperature. This software primarily used Radio Astronomy Instrumentation purpose, but this can be used in metrological as well as in RADAR engineering.