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A novel design of S-band based circularly polarized small satellite patch antenna is presented. It comprises three slots and an overall dimensions of 98 mm x 98 mm. The antenna has been designed for an impedance of 50 ohm and shows optimum performance for frequency range of 2.3 GHz to 2.5 GHz. Absolute gain observed is 7.8 dBi with main lobe at 20 normal to the antenna plane, making it close to unidirectional antenna. A diamond shaped patch with suitable location of coaxial feed allows the antenna to be circular polarized. Additionally, three identical slots were embedded in the radiating patch to obtain the high bandwidth compact antenna with right circular polarization. The variation of feed position allows switching between Left and Right Hand Circular Polarization (LHCP, RHCP) with 5.48 dBi gain. The S11 parameter was measured using Network Analyzer and similar results were obtained as software simulation output. The designed antenna is compatible with CubeSat configuration and hence can be used for various small satellite applications.

In recent years, development of various applications such as IoT and 5G has been carried out, and frequency tightness has occurred. Therefore, there is a demand for technological development beyond the quasi-millimeter wave band. we propose a microstrip antenna employing a square metal ring for quasi-millimeter wave applications. This antenna can improve and control absolute gain by using a square metal ring. It is clear that the gain can be controlled stepwise from 6.9 dBi to 9.5 dBi at 24GHz band by electromagnetic field analysis when the antenna employing square metal ring is configured to change the substrate thickness.

Detection of low-intensity light relies on the conversion of photons to photoelectrons, which are then multiplied and detected as an electrical signal. To measure the actual intensity of the light, one must know the factor by which the photoelectrons have been multiplied. To obtain this amplification factor, we have developed a procedure for estimating precisely the signal caused by a single photoelectron. The method utilizes the fact that the photoelectrons conform to a Poisson distribution. The average signal produced by a single photoelectron can then be estimated from the number of noise events, without requiring analysis of the distribution of the signal produced by a single photoelectron. The signal produced by one or more photoelectrons can be estimated experimentally without any assumptions. This technique, and an example of the analysis of a signal from a photomultiplier tube, are described in this study., Comment: 18 pages, 6 figures

This article examines a noval series-fed triangular microstrip ring resonator (TMRR) antenna array. Each radiating element is made up of a wavelength-long microstrip line with the two ends joined together to form an isosceles triangle. The antenna array is fed by an N-shaped microstrip feed line and excited by a coaxial feed probe. The operational mechanism of the proposed feed system in terms of its electrodynamics is examined with respect to its relative size occupancy, dispersion along the feed line, and the feed effect on the spatial orientation of the propagated radio waves. The size occupancy of the antenna array is 45 mm2 x 60 mm2 with a measured reflection coefficient S11 of -27.5 dB at a resonant frequency of 5.76 GHz. The simulated S11 is -29.2 dB at a resonant frequency of 5.8 GHz. The measured gain is roughly 10.46 dBi using the absolute gain method. The resulting antenna array is compact in size and exhibits reasonable performance in terms of gain, reflection coefficient, low mass/volume, and weight.

This paper presents high directive low cross-polarized 4 × 4 antenna array for Ku-band application. It consists of four 2 × 2 subarrays. The single element of the array is designed from the modified Baravelle’s spiral geometry, which resonates at 13.01 GHz. In 2 × 2 subarray, by introducing delay-feed line, the lower elements have a delay compared to upper elements. By using this scheme, a 4 × 4 array has been designed and achieved good side-lobe as well as grating lobe suppression. The feed network of the array is designed in such a manner, to make the structure compact in size and to get a highly directive beam pattern from it. Finally, experiments are carried out to verify the designed prototypes. Measured results show that the single element has a high gain of 9.82 dBi and impedance bandwidth of 6.42 % with a radiation efficiency of 88.70 % . The array gives an absolute gain of 18.40 dBi and impedance bandwidth of 6.78 % . The measured radiation efficiency of the array is 74.54 % . Both the antenna and array gives less than - 40 dB cross-polarization along the boresight ( θ = 0 ° ) direction. Experimental results show that the proposed antennas are suitable for Ku-band applications.

This paper presents millimeter-wave and terahertz double bow-tie slot antennas on a synthesized elliptical silicon lens. Two different antennas are designed to cover 0.1–0.3 and 0.2–0.6 THz, respectively. The double bow-tie slot antenna results in a wide impedance bandwidth and 78–97% Gaussian coupling efficiency over a 3:1 frequency range. A wideband coplanar-waveguide low-pass filter is designed using slow-wave techniques, and the measured filter response shows an S $_{21}$ < −25 dB over a 3:1 frequency range. Absolute gain measurements done at 100–300 GHz and 200–600 GHz confirm the wideband operation of this design. The double bow-tie slot antenna is intended to fill the gap between standard double-slot antennas and log periodic and sinuous antennas, with applications areas in radio astronomy and imaging systems.

A compact CPW-fed metamaterial (MTM)-inspired zeroth-order resonating (ZOR) antenna is presented with backed ground plane. Such MTM antenna consists of thin conducting line and a bow-tie shaped patch connected to CPW feed. The proposed structure shows compact size with radiating element dimensions of $0.095{{\lambda }_{\text{o}}} \times 0.042{{\lambda }_{\text{o}}} \times 0.013{{\lambda }_{o}}$ by introducing ground plane at bottom. As an advantage, resonant frequency is shifted toward left which corresponds to 57.9% miniaturization area with respect to the proposed antenna without backed plane (resonating at 3.7 GHz). The proposed MTM antenna exhibits zeroth-order resonance (ZOR) at 2.4 GHz and has an impedance bandwidth ( ${S11} .) of 25.4%. The proposed structure shows good radiation characteristics with simulated absolute gain of 1.59 dBi and simulated radiation efficiency of 91.5% throughout the operating bandwidth. Now for extending the bandwidth and shifting the resonant frequency to be operated in WiMAX band (3.5–3.57 GHz), electromagnetic band gap (EBG) structures are loaded in upper ground plane. This antenna shows an impedance bandwidth of 54.2% and resonates at 3.3 GHz. The radiation patterns are consistent throughout the working band. The prototype structures have been fabricated and experimentally validated. The designed antennas are suitable for use in LTE, WLAN, and WiMAX (2.5/3.5 GHz).

A low-profile tightly coupled phased array antenna with the characteristics of 3:1 bandwidth and $\mathbf{\pm 45^{\circ}scan}$ has been proposed in this paper. The array element consists of three layers of Duroid 5880 substrates and a couple of dipole arms. The novelty of the design is the loaded cross-shaped patch which is employed to avoid the common-mode resonance when unbalanced feeding the balanced dipoles. The obtained results confirm that, the array with 7mm spacing can operate from 7 to 21 GHz with VSWR $\leq 2.5$ for 45°scan in both E-and H-planes. The absolute gain of embedded central element pattern is less than 0.6dB compared with the ideal gain, indicating low loss and good efficiency. It is also worth mentioning that, the whole thickness of the antenna is around 4.5mm, which means it is suitable for conformal platforms.

In this paper, based on rigid-flex printed circuit board (PCB), a compact solution of Antenna-in-Package (AiP) including RF transmitter and microstrip passive phased antenna array is demonstrated. Apart from the landing of two connectors, the size shrinks down to 35 mm × 32 mm. RF transmitter works at the band of 26.2 GHz to 27.2 GHz, with conversion gain of 13 dB and rejection ratio up to 17.5 dBc. The 1 × 4 microstrip passive phased antenna array integrating 4 × 4 Butler Matrix achieves four scanning angles which are -10°, 30°, -30° and 10° with 20° half power beam width (HPBW), and simulated absolute gain is 13.51 dBi, 12.31 dBi, 12.23 dBi and 13.26 dBi respectively. Minor deviation on scanning angles from simulation data is observed in the testing due to measurement and manufacturing tolerance. However, among operating bandwidth, HPBW, main-to-side lobe ratio and the difference between two scanning angles when port 1, 4 and port 2, 3 are excited respectively are in good agreement with simulation results

This paper presents a super wide-band planar monopole slot antenna for 5G mobile communication bands from 22.97-35.04 GHz. The proposed antenna has a planar slot with a stepped monopole structure at its center that is fed through a Coplanar waveguide. The antenna has a peak gain of 5.7 dBi and radiation efficiency greater than 98%. The proposed antenna has a size of 8×8 mm 2 . An 8-element array configuration of the antenna provides maximum absolute gain of 14.9 dBi. The antenna array has an overall size of 8×64 mm 2 . Radiation patterns of the array has 3dB beam-width of as narrow as 9.2 degrees with side lobe level of -13.1 dB. The large bandwidth, high gain and small size of this antenna makes it a potential candidate for future 5G mobile phones and millimeter-wave communications.

International audience; Avalanche fluctuations set a limit to the energy and position resolutions that can be reached by gaseous detectors. This paper presents a method based on a laser test-bench to measure the absolute gain and the relative gain variance of a Micro-Pattern Gaseous Detector from its single-electron response. A Micromegas detector was operated with three binary gas mixtures, composed of 5% isobutane as a quencher, with argon, neon or helium, at atmospheric pressure. The anode signals were read out by low-noise, high-gain Cremat CR-110 charge preamplifiers to enable single-electron detection down to gain of 5× 103 for the first time. The argon mixture shows the lowest gain at a given amplification field together with the lowest breakdown limit, which is at a gain of 2×104 an order of magnitude lower than that of neon or helium. For each gas, the relative gain variance f is almost unchanged in the range of amplification field studied. It was found that f is twice higher (f~0.6) in argon than in the two other mixtures. This hierarchy of gain and relative gain variance agrees with predictions of analytic models, based on gas ionisation yields, and a Monte-Carlo model included in the simulation software Magboltz version 10.1.

High performance stability of the ATLAS Tile calorimeter is achieved with a set of calibration procedures. One step of the calibration procedure is based on measurements of the response stability to laser excitation of the photomultipliers (PMTs) that are used to readout the calorimeter cells. A facility to study in lab the PMT stability response is operating in the PISA-INFN laboratories since 2015. Goals of the tests in lab are to study the time evolution of the PMT response to reproduce and to understand the origin of the response drifts seen with the PMT mounted on the Tile calorimeter in its normal operation during LHC run I and run II. A new statistical approach was developed to measure the drift of the absolute gain. This approach was applied to both the ATLAS laser calibration data and to the data collected in the Pisa local laboratory. The preliminary results from these two studies are discussed.

We will report on the setup and calibration of the instrumentation for sFLASH. The sFLASH experiment is a measurement of the air fluorescence from ∼10$^{21}$ eV artificial air showers developed in an alumina target by an electron beam provided from End Station A of the Stanford Linear Accelerator Center (SLAC). sFLASH employs Photomultiplier tubes (PMTs) to detect the fluorescence photons and an Integrating Charge Transformer (ICT) to measure the beam current. The PMTs are positioned ~10m perpendicular to shower axis are used to measure the air fluorescence photons. The absolute gain of the PMTs was measured using CRAYS at the Institute of Cosmic-Ray Research, Japan. CRAYS is a PMT photo-gain calibration system consisting of a vessel containing nitrogen gas and a 14μJ nitrogen (337.1 nm) laser. The gain of each PMT was monitored during the course of the experiment using a YAP pulser (YAlO: Ce + $^{241}$Am) potted into an ultraviolet optical filter attached to the surface of the PMT window. We expect to achieve an overall experimental uncertainty of ~6%. The ICT (Bergoz) consists of 20 turns of coil to measure the beam current. In the sFLASH experiment we set it ~1 m away from beam exit to measure the beam current just prior to entering the target material. The ICT was calibrated with 2 ns pulse generator at Jet Propulsion Laboratory. The calibration uncertainty of the ICT is ~1%.

A practical method is proposed for complete gain measurement in distributed feedback (DFB) laser diodes. It is non-destructive and does not require any reference device. It includes the whole range of continuous gain values, from its minimum to threshold, passing through the transparency condition. The method requires a single absolute gain measurement for calibration. An example is reported for a DFB preserving Fabry–Perot multi-modes in the sub-threshold regime.

A stacked microstrip antenna with shorting plates and slits is proposed as a broadband dual-band antenna. By shorting the upper patch to the lower patch at two apexes of the diagonal of the square patch, the bandwidths (for VSWR ≤2) at the two frequency bands are enhanced and the absolute gain at the high-elevation angles at the higher-frequency band is improved. Moreover, the cross polarisation in H plane at the higher-frequency band is reduced by inserting the slits on the lower patch conductor. The proposed antenna radiates to the high-elevation angles at the two frequency bands. The measured bandwidths (for VSWR ≤2) with an absolute gain at thetas=0°≥4 dBi are 19.1 and 18.7% at the lower and higher-frequency bands, respectively.

We propose a novel 3-D absolute gain pattern measurement method using 1-D circular near-field to far-field transformation (1-D CNFFFT) for elongated antennas such as base-station antennas. By combining a few 1-D cut plane patterns and the far-field optimal sampling interpolation (OSI) expansion, we can obtain the 3-D absolute gain pattern. In experiment for a base station antenna at 2 GHz band, we demonstrate that the 3-D absolute gain pattern measured by the propose method agrees well with the 3-D pattern measured by the conventional cylindrical near-field scanning.

The dependency of planar folded slot antenna characteristics fabricated on alumina substrates over the temperature range of 25 to 400 C are presented. The 3.575 GHz antenna is fed by a 20 mm long, 50 CPW line (S = 130 and W = 60 μm), and there is no ground plane on the back side of the substrate. An on-wafer TRL calibration was used to deembed the CPW feed line for return loss measurements and to measure the increase in the effective dielectric constant and attenuation of the CPW lines as a function of temperature. The measured antenna characteristics show that the resonant frequency varies by less than 1%, the minimum return loss increases from 11 to 16 dB, the quality factor increases from 25.5 to 44.75, and the gain decreases by 1 dBi as temperature is increased from 25 C to 400 C. Finally, the effect of the measurement test setup on the measured radiation patterns is discussed.

A method is presented for the simultaneous measurement of the absolute gain of antennas in solution and the dielectric properties of the solution. The principle and formulation are based on a modified Friis transmission formula. This three-antenna method is applied to gain measurement of printed dipole antennas in solution, and demonstrated through comparison with calculated results to be an accurate method for the measurement of both antenna gain and solution dielectric properties.

Simulation is an indispensable means of designing antennas, especially when the evaluation of the antenna characteristics using theoretical analysis is complex or not very accurate. This work proposes an open-ended image nonradiative dielectric (NRD) guide antenna and presents its characteristics obtained using the finite-difference time-domain (FDTD) method. The key features of the FDTD implementation are discussed, particularly the simple and convenient approximate three dimensional modeling of the coaxial feed cable and the excitation probe that were used. The characteristics of the antenna that were determined are the return loss and absolute gain frequency characteristics and the E- and H-plane radiation patterns. Experimental results are used to verify the characteristics obtained using FDTD and are found to be in good agreement.

The primary spectrometer of the cold time-of-flight instrument IN5 at the ILL has been upgraded over the last 2 years. After commissioning in spring 2003 the absolute gain in flux when compared to the former spectrometer setting has been measured by gold-foil activation. Within standard configuration, namely, an incident wavelength of λ=5 A and chopper speeds chosen such that they correspond to identical energy resolution (δE≃100 μeV ) and time frame, the flux has been found an order of magnitude higher on the upgraded instrument. Apart from the gain in flux the new spectrometer allows to work with appreciably improved resolution (up to a factor 2) at identical wavelength.

The phase dynamics that occur in bulk InGaAsP-InP semiconductor optical amplifiers (SOAs) in response to picosecond pulse excitations at 10 and 40 GHz are studied experimentally and numerically for various amplifier lengths. The time dependencies of the phase changes and of the absolute gain of the amplifier are measured simultaneously. The total phase shifts induced by 1.5-ps pulses at 10 GHz are higher than /spl pi/ in SOAs with active region lengths between 0.5 and 2 mm and exceed 2/spl pi/ in a 1.5-mm-long amplifier. Phase shifts above /spl pi/ are measured at 40 GHz in 1.5- and 2-mm-long SOAs. The dependence of the total phase shift on the amplifier bias current and length and on pump pulse energy is investigated. Numerical simulations based on a comprehensive time-domain SOA model allow us to confirm the experimental results for a wide range of amplifier parameters. In particular, SOAs with lengths up to 5 mm have been modeled, and the calculations suggest that the maximum phase shifts occur in amplifiers of approximately 2-mm length. The phase dynamics measurements are illustrated at the example of an optical time division multiplexing add-drop multiplexer, based on a SLALOM switch, gated by 10- or 40-GHz control pulses. We find that simultaneous good dropping and clearing is possible if the length and the operating conditions of the SOA in the switch are chosen such as to induce a full /spl pi/ phase shift.

A new approach to wide scan-angle antennas at millimeter-wave frequencies is introduced with special focus on ease of manufacturing and reliability. The system is composed of planar feed antennas (tapered-slot antennas), which are positioned around a homogeneous spherical Teflon lens. Beam scanning can be achieved by switching between the antenna elements. The spherical-lens system is analyzed through a combined ray-optics/diffraction method. It is found that a maximum efficiency of 50%-55% can be achieved using Teflon, Rexolite, or quartz lenses. The efficiency includes taper, spillover, and reflection loss. Calculations also indicate that the maximum lens diameter is 30-40 /spl lambda//sub 0/, which results in a maximum directivity of 39.5-42 dB. Measurements done on a single-element feed and a 5-cm Teflon lens agree very well with theory and result in a 3-dB beamwidth of 5.5/spl deg/ and better than -20-dB sidelobe levels at 77 GHz. Absolute gain measurements show a system efficiency of 46%-48% (including dielectric loss). A 23- and 33-element antenna array with a scan angle of /spl plusmn/90/spl deg/ and a -3.5- and -6-dB crossover, respectively, in the far-field patterns was also demonstrated. The 23-element array resulted in virtually no gain loss over the entire 90/spl deg/ scan angle. This represents, to our knowledge, the first wide scan-angle antenna at millimeter-wave frequencies.

The finite-difference time-domain (FDTD) method is considered a versatile and efficient tool for the solution of Maxwell's equations in complex structures for any time dependence. We show an antenna feed model suitable for performance evaluation of a cavity-backed slot antenna using the FDTD technique. The gap voltage and the coaxial feed models are examined, and their input characteristics and absolute gains are compared. Analytical results show that the input characteristics are estimated with fewer time steps for the coaxial model than for the conventional gap voltage model. Furthermore, we show how to calculate absolute gains and radiation patterns using the coaxial model and a sinusoidal voltage source at the desired frequency. The computed results of the absolute gain converge after the fifteenth period of the voltage source for the coaxial model and are in good agreement with the experimental results. On the other hand, the absolute gain is observed to fluctuate when the gap voltage model is used. The performance evaluation and comparison reveals that the coaxial model is an appropriate feed model for use in the analysis of the performance of the cavity-backed slot antenna using the FDTD technique. The good agreement of the FDTD results with the experimental measurements demonstrates the effectiveness of the model and the method proposed.

The authors investigated the impact of replacing BGO by lutetium oxyorthosilicate (LSO) in the fabrication of the EXACT HR PLUS position encoding detector for PET. A detailed Monte Carlo simulation was used to track the interactions of energetic photons in the volume of the block as well as to treat the generation and propagation of scintillation light through its geometry. The simulation also accounts for LSO's non-proportional scintillation response, the bulk attenuation to its own scintillation and the noise contribution from the amplification of photoelectrons in the readout units. The model predicts that the increased photostatistics available in LSO compared to BGO leads to improvements by up to a factor five in the peak-to-valley ratios of the position response of the block to a uniform flood of 511 keV photons. For the crystals located along the diagonal, and considering events in a window of 350 to 650 keV, the position encoding accuracy is found to vary from 69% to 88% representing an absolute gain of at most 8% over its BGO precursor. With peak photoelectron counts of 678 to 2024, the energy resolution of the same crystals is found to vary from 14% to 9%.

MicroStrip Gas Counters (MSGCS) with strip patterns on bare and coated borosilicate glass as well as MicroGap Counters (MGCs) have been irradiated with 5.4 keV X-rays to investigate their high rate capability and ageing behaviour. The application of semiconductive coatings under the strips of MSGCs results in an improved short- and long-term gain stability in comparison to counters with uncoated borosilicate substrates, for count rates up to 105 Hz/mm2. However, the absolute gain of a coated detector is significantly smaller than that of a conventional one. The MGC has high-rate characteristics, as good as those for coated MSGCs. Results on the ageing of MSGCs on coated and uncoated glass, and of the MGC, are presented.

Uncertainty in absolute gain and crosstalk factors are the primary sources of error in dual-channel radar measurements. A full two-port calibration technique compensates for the errors introduced due to an imperfect antenna system and improves the isolation between orthogonal polarization channels as long as the observed cross section is above the equivalent system noise cross section. A novel technique for calibrating a dual-polarized network analyzer-based scatterometer system is discussed. Rigorous two-port S-parameter representation is used to describe absolute gain and crosstalk characteristics. Validity of the crosstalk correction is demonstrated by measuring the point target scattering matrix. Correction factors are obtained by measuring the S-parameters of trihedral and dihedral comer reflectors of known sizes. Results of absolute gain of the antenna system are verified using independent test target cross section measurements.

The High Resolution Fly's Eye Experiment (HiRes) measures cosmic rays from 1017 eV to beyond 1020 eV by the atmospheric fluorescence light produced in their cascade showers. The light is detected with photomultiplier tubes (PMTs). The full HiRes project proposes to use about 30000 PMTs in two sites. More than four thousand tubes are already in operation. Accurate calibrations of the absolute sensitivity of the PMTs are essential to this experiment. We have developed at the University of Utah a facility to calibrate the absolute gain and quantum efficiency of the tubes to the accuracy of better than three percent. This facility has proved to be capable of testing a large number of photomultiplier tubes efficiently and economically. In addition, it can be used to map the gain and the quantum efficiency of a PMT as a function of where the incident photons hit the tube's window. Although this facility is developed for HiRes, it is applicable to other experiments that utilise PMTs. We shall describe in this report the operation principles, the apparatus and some typical results.

In this paper, the design of a dual band quadrifilar helical antenna (QHA) is proposed for the radio beacon receiver in the application of the ground station of the low earth orbit (LEO) satellite. The new configuration of the QHA is proposed to achieve the dual operating frequencies (150 MHz and 400 MHz), which it is the combination of two bifilar helical antennas (BHA). The proposed antenna possess the hemispherical radiation pattern, dual-band operation, circular polarization and 2.2 dBic absolute gain. The simulation results are shown to demonstrate the antenna performance.

We report measurements of dynamic range, gain profile and absolute gain of three second-generation image intensifiers under pulsed illumination. One electrostatically focused (Mullard 1330) and two proximity focused (Varo 9732 and Photek microchannel plate 140) image intensifiers have been characterized. The dynamic ranges were found to be 240, 560, and 400 for the Mullard, Varo, and Photek tubes, respectively, for all gain settings. At a microchannel plate bias voltage of 900 V the radiant gain for these tubes is 4*103, 3*104, and 2*103, respectively. The sensitivity and dynamic range of the charge-coupled device camera recording system were found to be superior to that of conventional highspeed film (Kodak TMAX).

The finite difference time domain (FDTD) technique is a popular method for analyzing electromagnetic scattering, radiation, and penetration problems. Several authors have recently applied the FDTD method to antenna radiation problems. To date, the antenna structures considered have been wire and conical monopole antennas, rectangular waveguides, pyramidal horn antennas, and microstrip antennas. Results from these analysis have been in the form of normalized field patterns and no results showing absolute gain have been presented. The article demonstrates the first staircased application of the FDTD method to the analysis of radiation from circular waveguides and other shaped-end radiators. Results of absolute gain versus angle are shown for a straight-cut circular waveguide and for two different shaped-end radiators. All FDTD analyses are full three-dimensional computations and are compared in each case with measured data. >

Absolute gain and radiation efficiency are calculated using the finite-difference-time-domain (FDTD) method. The method described utilizes pulsed excitation, so that wideband results are available from a single FDTD computation. The approach is demonstrated for a simple wire antenna geometry, and is validated by comparison with results obtained using the method of moments. >

The antenna under consideration is a five-turn Archimedean rectangular two-arm wire spiral antenna, which is 46 x 15.7cm in size is presented in this paper. It is placed in the x-y plane. There are two ports (one per arm) located at the center. Normally, a two-arm spiral antenna cannot practically radiate spiral mode 2, as it requires the two-ports at the center to be excited in phase (i.e. an unbalanced feed), but it can be simulated using a method of moments code (MoM) without any problems. All simulation results are obtained using an MoM code. The goal is to produce the best possible horizontally polarized omnidirectional pattern. The reader should note that all gain values cited in this section do not include mismatch losses. Absolute gain, which includes matching networks, will be presented at the conference.

As shown in Chapter 5. for plane rectilinear near-field scanning, probe pattern characterisation errors contribute to the overall facility error budget as a singular mapping. Essentially then, this means that an error in the probe pattern at a particular direction in space will correspond to a similar error at that angle being introduced into any antenna pattern that has been corrected with this data. Furthermore, this can potentially constitute one of the largest and most repeatable, measurement uncertainties. Thus it is clear that in order to obtain reliable measurements, the electromagnetic (EM) properties of the near-field probe must be known very accurately indeed. Throughout this work, it has been assumed that relative measurements are taken, that is, without reference to absolute gain. If an absolute gain is required, then it is assumed that a substitution method is used employing a calibrated gain standard in order that the measurements can be correctly normalized. The importance of this for the characterisation of the near-field probe is that if the same probe and probe pattern used to correct the measurement of the antennas under test (AUTs) and the standard gain horn (SGH) then the gain of the probe will be unimportant. Thus, within this chapter, characterisation of the gain of the probe is not discussed and the gain of the probe will be normalized to unity for convenience. This chapter briefly describes the properties that are desirable in a near-field probe before proceeding to describe methods for obtaining and then using reliable probe pattern data.

The Pierre Auger Observatory is a hybrid detector to measure ultra-high energy cosmic rays by an array of 1600 surface detectors and 24 fluorescence telescopes. Every night the response of the telescopes to light from a LED source, distributed through fibers and illuminating the camera, is measured. This relative calibration monitors the response of each pixel and the time stability. The absolute calibration is one way to perform an end-to-end calibration including effects of the UV filter transmittance, losses at the corrector ring elements, mirror reflectivity, shadowing effects of the camera, light collection efficiency, photomultiplier tube (PMT) gain, and the response of the analog and digital electronics. The absolute gain of each PMT is obtained from the variance of the recorded signals and taking into account the single photoelectron resolution (SER) and the bandwidth of the analog electronics. Thus, the knowledge of the SER and the quality parameters of the optics allow us to calculate the sensitivity piece by piece and to cross-check the absolute calibration. This work presents the results of measurements of the single photoelectron spectra recorded on site with our standard setup. The results are consistent with the Monte Carlo simulations of the multiplication processes at each dynode.

A low-profile omnidirectional zeroth-order resonator (ZOR) antenna based on a mushroom structure is proposed in this paper. The mushroom structure as a transmission line has negative, zero, and positive propagation constant depending on its operation frequency. Zeroth-order resonance, of which length is independent of the physical length, is naturally presented. In particular, mushroom ZOR antenna generates a uniform vertical electric field against ground plane, so that it omnidirectionally radiates in a horizontal plane. The operation frequency, absolute gain, and gain variations for omnidirectional radiation of the designed prototype are 7.8 GHz, 3.1 dBi, and 2.05 dBi, respectively. Details of the antenna design and the simulated results are discussed

Non-uniform designs for Erbium doped waveguide amplifiers (EDWA) and Yb: Er co-doped waveguide amplifiers (YEDWA) were presented based on the standard rate equations including six Er energy levels and two Yb energy levels. Numerical results were shown that the design of the non-uniform EDWA operated by gain value get a gain improvement of 110.3% than uniform one, and designs of non-uniform EDWA and YEDWA operated by pump efficiency get gain improvements of 21.03% and 10.17% than uniform ones, even get gain improvements of 2.25% and 7.26% than the absolute gain maximum of uniform EDWA and YEDWA, respectively. The optimization of population inversion in 4 I 11/2 could be demonstrated by the photoluminescence (PL) enhancement observed in cascaded Er doped glass measurement at room temperature.

The absolute gain of a corrugated horn which is designed as a 100-GHz gain standard for the Crawford Hill 7-Meter offset reflector has been calculated and measured. The measured gain is determined from "three horn" transmission measurements. The other two horns are a TRG Model W869 corrugated horn and a dual mode horn. Correction factors were computed from the near field power transmission formula. The measured gain of the gain standard is 30.8 \pm 0.16 dB . Comparison between measured and calculated gains indicate very low ohmic loss in a corrugated horn. The condition of maximum gain for a given length has been found to be a half wavelength phase deviation in the horn aperture. Calculated gain data as well as near field correction factors for two identical corrugated conical horns are given here as reference information.

Purcell's image method for measuring the absolute gain of an antenna is particularly attractive for small test antennas. The method is simple to use and utilizes only one antenna with a reflecting plane to provide an image for the receiving antenna. However, the method provides accurate results only if the antenna is matched to its waveguide. In this paper, a waveguide junction analysis is developed to determine the gain of an antenna under mismatched condition. Absolute gain measurements for two standard gain horn antennas have been carried out. Experimental results agree closely with published data.

The CMS-HF forward calorimeter has specific requirements for the construction and the operation of the detector. The phototubes suggested by several manufacturers were tested and Hamamatsu R7525HA photomultiplier tube conformed best to these requirements. About 2000 PMTs were needed in the HF calorimeter. The timing, dark current, and relative gain values of these 2000 phototubes were measured and organized into a database. Single photoelectron spectrum resolution, absolute gain versus high voltage, and the lifetime were measured on a small sample. Except a few phototubes with unacceptably high dark currents, all the tubes were well within the specifications.

The authors present a novel design for a low-sidelobe microstrip antenna array and feed network at C-band (6 GHz). The array consists of 10 rectangular patch elements. A -30-dB sidelobe Chebyshev weighting function was used to produce a tapered aperture illumination. The implementation of the tapered weighting function was carried out by using branch-line couplers in the corporate feed. Experimental results show that a -25-dB sidelobe level was achieved in this design with an absolute gain of 18.2 dB, an efficiency of 80% and a cross polarization of -16 dB. >

The authors introduce a novel antenna measurement procedure that uses a wideband polarimetric RCS (radar cross-section) measurement system, together with a special antenna description, appropriate to this technique. A complete set of antenna parameters including input impedance, polarimetric gain, polarization decoupling, and scattering properties is obtained. All parameters can be determined with a single measurement setup, no RF line is necessary, and no standard gain antennas are needed for absolute gain measurements. Using the scattering matrix approach and knowing all the components of the matrix, it is possible to describe the antenna behavior when it is terminated with any desired load. Because the measurements are taken over a very broad frequency range, specifications for frequency bandwidth can be made in terms of input impedance as well as in terms of gain, polarization, or cross-polarization properties. >

In VHF and UHF bands, antenna patterns for short range airborne communications are required to be omni-directional. Contributions from reflections and diffractions from the airframe usually distort the primary radiation patterns of antennas mounted on airframes. Moreover, these diffractions and reflections become increasingly important as the frequency of operation increases. Therefore, for this type of application, an antenna performance simulated without the airframe is not an accurate representation. In this study, an accurate and versatile finite element method (FEM) based on the discretization of Helmholtz's equation has been developed to analyze VHF and UHF antennas mounted on helicopter airframes, parts of which may include composite material and anisotropies. The FEM code was implemented with linear edge-based tetrahedral elements and first/second-order Absorbing Boundary Conditions. Possible material anisotropies in the computational domain are accounted for by using a permittivity and a permeability tensor. Radiation characteristics are predicted for absolute gain, spatial field distribution, input impedance and return loss, and then compared with measurements for verification.

Novel gain control of the absolute gain of a gain-clamped sampled grating laser amplifier has been demonstrated. Up to 12 dB of control of the gain level of a gain-clamped SOA has been achieved.

The China Dark Matter Experiment (CDEX) Collaboration will carry out a direct search for weakly interacting massive particles with germanium detectors. Liquid argon will be utilized as an anti-Compton and cooling material for the germanium detectors. A low-background and large-area photomultiplier tube (PMT) immersed in liquid argon will be used to read out the light signal from the argon. In this paper we carry out a careful evaluation on the performance of the PMT operating at both room and cryogenic temperatures. Based on the single photoelectron response model, the absolute gain and resolution of the PMT were measured. This has laid a foundation for PMT selection, calibration and signal analysis in the forthcoming CDEX experiments., 5 pages, 8 figures

White noise techniques are used to compare the two photoreceptor sub-types in blowfly retina, the short visual fibres (R1-6) that code achromatic contrast, and the long visual fibres (R7 and R8) that together code wavelength distribution and polarisation plane. Measurements of signal and noise spectra and contrast gain, taken across a broad intensity range, permit a detailed comparison of coding efficiency under natural conditions of illumination. As a function of excitation (effective photons per photoreceptor per second; h upsilon/rec per s), adaptive changes in the long and short visual fibres are similar, suggesting that post-rhodopsin their phototransduction cascades are identical. Under identical natural daylight conditions (photons per cm2 per second; h upsilon/cm2 per s) short visual fibres catch more photons, thus operating with a higher signal to noise ratio and faster response, to consistently outperform the long visual fibres. Long visual fibres compensate for their poor quantum catch by having a higher absolute gain (mV/h upsilon) which at low light intensities enables them to achieve a level of contrast gain (mV/unit contrast) similar to the short visual fibres. Differences in signal to noise ratios are related to known differences in photoreceptor structure and synaptic frequency among visual interneurons. The principles of matching sensitivity and synapse number to quantum catch described here could explain analogous differences between chromatic and achromatic pathways in mammalian and amphibian retinas.

A simple but robust LED based light detector gain monitoring system capable of measuring gain to within a sensitivity of a fraction of a percent is presented. The absolute gain of the detector and its electronics can be measured with a systematic error from a fraction to a few percent depending on the photon-to-photon gain fluctuations. The method, based on intrinsic light and detector properties, does not require stringent mechanical or optical tolerances.

Theory and measurements are presented for stimulated Brillouin gain spectroscopy in anisotropic media. The coupling between arbitrary pump and Stokes waves and the corresponding acoustic wave is formulated in terms of the elastic displacement vector and the photoelastic tensor. A propagation equation that fully includes transient effects is obtained for the Stokes wave. In the limit of small-signal gains this propagation equation can be solved analytically, yielding expressions that relate experimentally accessible quantities to material properties. Absolute Brillouin steady-state gain coefficients, linewidths, and frequency shifts are thereby determined in a number of optical materials at 532 nm. The Brillouin gain coefficient for fused silica is measured by three techniques, providing the reference for absolute gain measurements. Quantitative agreement is found between theory and experiment for transient effects on stimulated Brillouin scattering.

We report what is to our knowledge the first high-resolution Brillouin gain spectrum in a solid. Resonances corresponding to longitudinal (compressional) and transverse (shear) acoustic waves in fused silica are observed with good resolution and a high signal-to-noise ratio. Absolute gain coefficients, linewidths, and Brillouin frequency shifts are measured. The agreement with previously measured values is good.

A General Extrapolation Technique which corrects for the effects of ground reflections in absolute gain measurements is described. It utilizes the Extrapolation Method developed at NBS which, in its present form, utilizes only amplitude versus distance data. However, for broadbeam antennas such as those encountered below 1 GHz, ground reflections may produce unwanted oscillations in the amplitude versus distance data. Hence the data are not amenable to the curve-fitting procedure of the Extrapolation Method. This problem can be overcome by including phase versus distance information to reduce the effects of ground reflections.