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The increment in the demand for high-frequency monolithic integrated circuits has driven the development of waveguide-to-microstrip transition that allow their characterization and integration with waveguide components. Unfortunately, some of these transitions currently feature a rather narrow bandwidth, especially when the substrate is inserted transversal to the propagation direction of the waveguide. Here we present a new design that overcomes this problem. The transisition was originally designed for a bandwidth of 33.5–60 GHz (extended V-Band) with the simulation results showing reflections below −19.5 dB in a fractional bandwidth of 55% and, moreover, can be scaled to other frequencies keeping good electrical characteristics. To validate the design we show the scaling, construction, and measurement in an extended Q-band (27–50 GHz) with the additional advantage of having a standard impedance of 50 Ω. The most novel feature is a staggered air cavity for the microstrip and planar probe, which generates return losses better than 20 dB in a fractional bandwidth of 53%.

In this article we present a miniaturized multiband metamaterial-based antenna for array applications, operating with good radiation performance over the LTE and UMTS uplinks within the 800–3000 MHz range. Each antenna element consists of a radiator and a metamaterial reflector. The former is a miniaturized Archimedean spiral antenna with an integrated matching line. The latter is placed 39 mm below the radiator and is shared among the multiple elements in the array application. The radiator is very compact, a square of 75 mm per side, equivalent to only 0.2 (0.75) times the free-space wavelength at 800 MHz (3000 MHz). The reflector is incorporated to achieve half-space radiation and is implemented with a novel multi-layered metamaterial structure to improve the radiation efficiency. The metamaterial, moreover, is used in a non-conventional way. In fact, we take advantage of its complete phase-response function, behaving, thus, as magnetic or electric conductor in different parts of the band. In this way, the in-phase reflection is not limited by the typical narrow bandwidth of artificial magnetic conductors. The measured S11 parameter is less than -8 dB and the simulated gain is greater than 4.2 dBi in a range exceeding the one covered by the UMTS and LTE uplinks. Furthermore, a 2×2 antenna array was also built. The reflections of each element are similar to those obtained in the single-element antenna.

Superconducting traveling-wave parametric amplifiers are a promising amplification technology suitable for applications in submillimeter astronomy. Their implementation relies on the use of Floquet transmission lines in order to create strong stopbands to suppress undesired harmonics. In the design process, amplitude equations are used to predict their gain, operation frequency, and bandwidth. However, usual amplitude equations do not take into account the real and imaginary parts of the dispersion and characteristic impedance that results from the use of Floquet lines, hindering reliable design. In order to overcome this limitation, we have used the multiple-scales method to include those effects. We demonstrate that complex dispersion and characteristic impedance have a stark effect on the transmission line's gain, even suppressing it completely in certain cases. The equations presented here can, thus, guide to a better design and understanding of the properties of this kind of amplifiers., 7 pages, 7 figures, submitted to IEEE Transactions on Applied Superconductivity

A spectral survey of methyl acetylene (CH3CCH) was conducted toward the hot molecular core/outflow G331.512-0.103. Our APEX observations allowed the detection of 41 uncontaminated rotational lines of CH3CCH in the frequency range between 172 and 356 GHz. Through an analysis under the local thermodynamic equilibrium assumption, by means of rotational diagrams, we determined T exc = 50 ± 1 K, N(CH3CCH) = (7.5 ± 0.4) × 1015 cm2, X[CH3CCH/H2] ≈ (0.8–2.8) × 10−8, and X[CH3CCH/CH3OH] ≈ 0.42 ± 0.05 for an extended emitting region (∼10″). The relative intensities of the K = 2 and K = 3 lines within a given K-ladder are strongly negatively correlated to the transitions’ upper J quantum number (r = −0.84). Pure rotational spectra of CH3CCH were simulated at different temperatures, in order to interpret this observation. The results indicate that the emission is characterized by a nonnegligible temperature gradient with upper and lower limits of ∼45 and ∼60 K, respectively. Moreover, the line widths and peak velocities show an overall strong correlation with their rest frequencies, suggesting that the warmer gas is also associated with stronger turbulence effects. The K = 0 transitions present a slightly different kinematic signature than the remaining lines, indicating that they might be tracing a different gas component. We speculate that this component is characterized by lower temperatures and therefore larger sizes. Moreover, we predict and discuss the temporal evolution of the CH3CCH abundance using a two-stage zero-dimensional model of the source constructed with the three-phase Nautilus gas-grain code.

Aims. With the aim of studying the physical properties of Galactic IR bubbles and to explore their impact in massive star formation, we present a study of the IR bubble S169, associated with the massive star forming region IRAS 12326-6245. Methods. We used CO(2-1),13CO(2-1), C18O(2-1), HCN(3-2), and HCO+ (3-2) line data obtained with the APEX telescope using the on-the-fly full sampling technique to study the properties of the molecular gas in the nebula and the IRAS source . To analyze the properties and distribution of the dust, we made use of images obtained from the IRAC-GLIMPSE, Herschel, and ATLASGAL archives. The properties of the ionized gas in the nebula were studied using radio continuum and Hα images obtained from the SUMSS survey and SuperCOSMOS database, respectively. In our search for stellar and protostellar objects in the region, we used point source calalogs obtained from the MSX, WISE, GLIMPSE, 2MASS, AAVSO, ASCC-2.5V3, and GAIA databases. Results. The new APEX observations allowed us to identify three molecular components, each one associated with different regions of the nebula, namely: at −39 km s−1 (component A), −25 km s−1 (component B), and −17 km s−1 (component C). Component A is shown to be the most dense and clumpy. Six molecular condensations (MC1 to MC6) were identified in this component, with MC3 (the densest and more massive one) being the molecular counterpart of IRAS 12326-6245. For this source, we estimated an H2 column density up to 8×1023 cm−2 . An LTE analysis of the high density tracer lines HCO+ (3-2) and HCN(3-2) on this source, assuming 50 and 150 K, respectively, indicates column densities of N(HCO+) = (5.2 ± 0.1) × 1013 cm−2 and N(HCN) = (1.9 ± 0.5) × 1014 cm−2. To explain the morphology and velocity of components A, B, and C , we propose a simple model consisting of a partially complete semisphere-like structure expanding at ∼ 12 km s−1. The introduction of this model has led to a discussion about the distance to both S169 and IRAS 12326-6245, which was estimated to be ∼ 2 kpc. Several candidate YSOs were identified, projected mostly onto the molecular condensations MC3, MC4, and MC5, which indicates that the star-formation process is very active at the borders of the nebula. A comparison between observable and modeled parameters was not enough to discern whether the collect-and-collapse mechanism is acting at the edge of S169. However, other processes such as radiative-driven implosion or even a combination of both mechanisms, namely, collect-and-collapse and radiative-driven implosion, could be acting simultaneously in the region., Instituto de Astrofísica de La Plata

The SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium) survey used the APEX telescope to map 84 deg^2 of the Galactic plane between l = -60 deg and l = +31 deg in several molecular transitions, including 13CO(2-1) and C18O(2-1), thus probing the moderately dense (~10^3 cm^-3) component of the interstellar medium. With an angular resolution of 30'' and a typical 1-sigma sensitivity of 0.8-1.0 K at 0.25 km/s velocity resolution, it gives access to a wide range of structures, from individual star-forming clumps to giant molecular clouds and complexes. The coverage includes a good fraction of the first and fourth Galactic quadrants, allowing us to constrain the large scale distribution of cold molecular gas in the inner Galaxy. In this paper we provide an updated overview of the full survey and the data reduction procedures used. We also assess the quality of these data and describe the data products that are being made publicly available as part of this first data release (DR1). We present integrated maps and position-velocity maps of the molecular gas and use these to investigate the correlation between the molecular gas and the large scale structural features of the Milky Way such as the spiral arms, Galactic bar and Galactic centre. We find that approximately 60 per cent of the molecular gas is associated with the spiral arms and these appear as strong intensity peaks in the derived Galactocentric distribution. We also find strong peaks in intensity at specific longitudes that correspond to the Galactic centre and well known star forming complexes, revealing that the 13CO emission is concentrated in a small number of complexes rather than evenly distributed along spiral arms., MNRAS, in press

We use the 13CO(2-1) emission from the SEDIGISM high-resolution spectral-line survey of the inner Galaxy, to extract the molecular cloud population with a large dynamic range in spatial scales, using the SCIMES algorithm. This work compiles a cloud catalogue with a total of 10663 molecular clouds, 10300 of which we were able to assign distances and compute physical properties. We study some of the global properties of clouds using a science sample, consisting of 6664 well resolved sources and for which the distance estimates are reliable. In particular, we compare the scaling relations retrieved from SEDIGISM to those of other surveys, and we explore the properties of clouds with and without high-mass star formation. Our results suggest that there is no single global property of a cloud that determines its ability to form massive stars, although we find combined trends of increasing mass, size, surface density and velocity dispersion for the sub-sample of clouds with ongoing high-mass star formation. We then isolate the most extreme clouds in the SEDIGISM sample (i.e. clouds in the tails of the distributions) to look at their overall Galactic distribution, in search for hints of environmental effects. We find that, for most properties, the Galactic distribution of the most extreme clouds is only marginally different to that of the global cloud population. The Galactic distribution of the largest clouds, the turbulent clouds and the high-mass star-forming clouds are those that deviate most significantly from the global cloud population. We also find that the least dynamically active clouds (with low velocity dispersion or low virial parameter) are situated further afield, mostly in the least populated areas. However, we suspect that part of these trends may be affected by some observational biases, and thus require further follow up work in order to be confirmed., 25 pages (+ appendices, 15 pages), 26 figures, MNRAS

We report experimental values of the complex dielectric permittivity of a wide variety of engineering polymers. Measurements were done using the filling waveguide method at Q-band (30–50 GHz), being representative of the values over the millimeter wave regime. This method has a high accuracy, providing excellent wide-bandwidth characterization. Measured samples include the most common engineering materials as polyamide, polyethylene, polytetrafluoroethylene, polyoxymethylene, polylactic acid, phenol formaldehyde resin, polypropylene, polyvinyl chloride, acrylonitrile butadiene styrene, polyphenyle sulfide, and polyether ether ketone. Results are comprehensive and represent an important contribution to the technical literature which lacks of material measurements at these frequencies. Of particular interest are samples of 3D printed materials and high performance polymers, that will probably find new and novel applications in the field of microwave components and antennas for the millimeter wave band.

Using APEX-1 and APEX-2 observations, we have detected and studied the rotational lines of the HC₃N molecule (cyanoacetylene) in the powerful outflow/hot molecular core G331.512−0.103. We identified 31 rotational lines at J levels between 24 and 39; 17 of them in the ground vibrational state v = 0 (9 lines corresponding to the main C isotopologue and 8 lines corresponding to the ¹³C isotopologues), and 14 in the lowest vibrationally excited state v₇ = 1. Using local thermodynamic equilibrium (LTE)-based population diagrams for the beam-diluted v = 0 transitions, we determined Texc = 85 ± 4 K and N(HC₃N) = (6.9 ± 0.8) × 10¹⁴ cm⁻², while for the beam-diluted v₇ = 1 transitions we obtained Texc= 89 ± 10 K and N(HC₃N) = (2 ± 1) × 10¹⁵ cm⁻². Non-LTE calculations using H₂ collision rates indicate that the HC3N emission is in good agreement with LTE-based results. From the non-LTE method, we estimated Tkin ≃90 K, n(H₂) ≃ 2 × 10⁷ cm⁻³ for a central core of 6 arcsec in size. A vibrational temperature in the range from 130 to 145 K was also determined, values which are very likely lower limits. Our results suggest that rotational transitions are thermalized, while infrared radiative pumping processes are probably more efficient than collisions in exciting the molecule to the vibrationally excited state v₇ = 1. Abundance ratios derived under LTE conditions for the ¹³C isotopologues suggest that the main formation pathway of HC₃N is C₂H₂ + CN → HC₃N + H., Instituto Argentino de Radioastronomía, Facultad de Ciencias Astronómicas y Geofísicas

We present the design, implementation, and characterization of the optics of ALMA Band 1, the lowest frequency band in the most advanced radio astronomical telescope. Band 1 covers the broad frequency range from 35 to 50 GHz, with the goal of minor degradation up to 52 GHz. This is, up to now, the largest fractional bandwidth of all ALMA bands. Since the optics is the first subsystem of any receiver, low noise figure and maximum aperture efficiency are fundamental for best sensitivity. However, a conjunction of several factors (small cryostat apertures, mechanical constraints, and cost limitations) makes extremely challenging to achieve these goals. To overcome these problems, the optics presented here includes two innovative solutions, a compact optimized-profile corrugated horn and a modified Fresnel lens. The horn profile was optimized for optimum performance and easy fabrication by a single-piece manufacturing process in a lathe. In this way, manufacturability is eased when compared with traditional fabrication methods. To minimize the noise contribution of the optics, a one-step zoned lens was designed. Its parameters were carefully optimized to maximize the frequency coverage and reduce losses. The optical assembly reported here fully complies with ALMA specifications.

Carbon-bearing molecules, particularly CO, have been widely used as tracers of molecular gas in the interstellar medium (ISM). In this work, we aim to study the properties of molecules in diffuse, cold environments, where CO tends to be under-abundant and/or sub-thermally excited. We performed one of the most sensitive (down to $\mathrm{��_{rms}^{CO} \sim 0.002}$ and $\mathrm{��_{rms}^{HCO^+} \sim 0.0008}$) sub-millimeter molecular absorption line observations towards 13 continuum sources with the ALMA. CO absorption was detected in diffuse ISM down to $\mathrm{A_v< 0.32\,mag}$ and \hcop was down to $\mathrm{A_v < 0.2\,mag}$, where atomic gas and dark molecular gas (DMG) starts to dominate. Multiple transitions measured in absorption toward 3C454.3 allow for a direct determination of excitation temperatures $\mathrm{T_{ex}}$ of 4.1\,K and 2.7\,K, for CO and for \hcop, respectively, which are close to the cosmic microwave background (CMB) and provide explanation for their being undercounted in emission surveys. A stronger linear correlation was found between $\mathrm{N_{HCO^+}}$ and $\mathrm{N_{H_2}}$ (Pearson correlation coefficient P $\sim$ 0.93) than that of $\mathrm{N_{CO}}$ and $\mathrm{N_{H_2}}$ (P $\sim$ 0.33), suggesting \hcop\ being a better tracer of H$_2$ than CO in diffuse gas. The derived CO-to-\h2 conversion factor (the CO X-factor) of (14 $\pm$ 3) $\times$ 10$^{20}$ cm$^{-2}$ (K \kms)$^{-1}$ is approximately 6 times larger than the average value found in the Milky Way.

The moisture content of wood is an important parameter for wood technology. Material mechanical resistance, cracking and resistance to fungi attack are dependent on this quantity. In this article we present the development of a moisture content measuring system for wood samples. The system measures the microwave propagation at 35–45 GHz using a free space collimated beam. Measured quantities are the phase delay and attenuation constant for both polarizations, parallel and perpendicular to wood fibers. This features depends strongly on moisture content, density, and fibers growth direction. Based on laboratory measurements we have obtained a relation between the average humidity of a set of woods and the measured propagation constants data. The proposed setup shows a first approach for a fast, contactless and reliable moisture level meter, which could be operated remotely in industrial environments. In this work we present our preliminary results including the microwave system design, the theoretical analysis of microwave propagation in wood, and the first experimental measurements.

This paper shows three microstrip metamaterial-inspired antennas (MMIAs) for the 2.4 GHz band, using a wavelength scaling and parametric sweep as main design guidelines. Interesting properties such as: high radiation efficiency, maximum total gain enhancement, ultra wideband operation and size reduction are achieved in these devices. Methodology proven to give good radiation properties to MMIAs made on general purpose substrates like FR4.

Little is known about how high-mass stars form. Around 30\% of the young high-mass stars in the Galaxy are observed at the edges of ionized (HII) regions. Therefore these are places of choice to study the earliest stages of high-mass star formation, especially towards the most massive condensations. High-spatial resolution observations in the millimeter range might reveal how these stars form and how they assemble their mass. We want to study the fragmentation process down to the 0.01~pc scale in the most massive condensation observed at the south-western edge of the HII region RCW~120 where the most massive Herschel cores ($\sim$124~$M_{\odot}$ in average) could form high-mass stars. Using ALMA 3~mm continuum observations towards the densest and most massive millimetric condensation (Condensation 1) of RCW~120, we used the getimages and getsources algorithms to extract the sources detected with ALMA and obtained their physical parameters. The fragmentation of the hersche cores is discussed through their Jeans mass to understand the properties of the future stars. We extracted 18 fragments from the ALMA continuum observation at 3~mm towards 8 cores detected with Herschel, whose mass and deconvolved size range from 2~$M_{\odot}$ to 32~$M_{\odot}$ and from 1.6~mpc to 28.8~mpc, respectively. The low degree of fragmentation observed, regarding to the thermal Jeans fragmentation, suggests that the observed fragmentation is inconsistent with ideal gravitational fragmentation and other ingredients such as turbulence or magnetic fields should be added in order to explain it. Finally, the range of fragments' mass indicates that the densest condensation of RCW~120 is a favourable place for the formation of high-mass stars with the presence of a probable UCHII region associated with the 27~$M_{\odot}$ Fragment 1 of Core 2., 7 pages, 4 figures

Spectral line surveys reveal rich molecular reservoirs in G331.512-0.103, a compact radio source in the center of an energetic molecular outflow. In this first work, we analyse the physical conditions of the source by means of CH$_3$OH and CH$_3$CN. The observations were performed with the APEX telescope. Six different system configurations were defined to cover most of the band within (292-356) GHz; as a consequence we detected a forest of lines towards the central core. A total of 70 lines of $A/E$-CH$_3$OH and $A/E$-CH$_3$CN were analysed, including torsionally excited transitions of CH$_3$OH ($\nu_t$=1). In a search for all the isotopologues, we identified transitions of $^{13}$CH$_3$OH. The physical conditions were derived considering collisional and radiative processes. We found common temperatures for each $A$ and $E$ symmetry of CH$_3$OH and CH$_3$CN; the derived column densities indicate an $A/E$ equilibrated ratio for both tracers. The results reveal that CH$_3$CN and CH$_3$OH trace a hot and cold component with $T_k \sim$ 141 K and $T_k \sim$ 74 K, respectively. In agreement with previous ALMA observations, the models show that the emission region is compact ($\lesssim$ 5.5 arcsec) with gas density $n$(H$_2$)=(0.7-1) $\times$ 10$^7$ cm$^{-3}$. The CH$_3$OH/CH$_3$CN abundance ratio and the evidences for pre-biotic and complex organic molecules suggest a rich and active chemistry towards G331.512-0.103., Comment: 15 pages, 7 figures, 7 tables. Accepted for publication in The Astrophysical Journal

Dual sideband (2SB) receivers are well suited for the spectral observation of complex astronomical signals over a wide frequency range. They are extensively used in radio astronomy, their main advantages being to avoid spectral confusion and to diminish effective system temperature by a factor two with respect to double sideband (DSB) receivers. Using available millimeter-wave analog technology, wideband 2SB receivers generally obtain sideband rejections ratios (SRR) of 10-15dB, insufficient for a number of astronomical applications. We report here the design and implementation of an FPGA-based sideband separating FFT spectrometer. A 4GHz analog front end was built to test the design and measure sideband rejection. The setup uses a 2SB front end architecture, except that the mixer outputs are directly digitized before the IF hybrid, using two 8bits ADCs sampling at 1GSPS. The IF hybrid is implemented on the FPGA together with a set of calibration vectors that, properly chosen, compensate for the analog front end amplitude and phase imbalances. The calibrated receiver exhibits a sideband rejection ratio in excess of 40dB for the entire 2GHz RF bandwidth., Comment: 7pp

The Atacama Large Millimeter/Sub-millimeter Array (ALMA) is currently the largest (sub-)mm wave telescope in the world and will be used for astronomical observations in all atmospheric windows from 35 to 950 GHz when completed. The ALMA band 1 (35–50 GHz) receiver will be used for the longest wavelength observations with ALMA. Because of the longer wavelength, the size of optics and waveguide components will be larger than for other ALMA bands. In addition, all components will be placed inside the ALMA cryostat in each antenna, which will impose severe mechanical constraints on the size and position of receiver optics components. Due to these constraints, the designs of the corrugated feed horn and lens optics are highly optimized to comply with the stringent ALMA optical requirements. In this paper, we perform several tolerance analyses to check the impact of fabrication errors in such an optimized design. Secondly, we analyze the effects of operating this optics inside the ALMA cryostat, in particular the effects of having the cryostat IR filters placed next to the band 1 feed horn aperture, with the consequent near-field effects. Finally, we report on beam measurements performed on the first three ALMA band 1 receivers inside test cryostats, which satisfy ALMA specifications. In these measurements, we can clearly observe the effects of fabrication tolerances and IR filter effects on prototype receiver performance.

Context: The bulk of the Molecular gas in the Central Molecular Zone (CMZ) of the Galactic center region shows warm kinetic temperatures, ranging from $>20$ K in the coldest and densest regions (n$\sim 10^{4-5}$ cm$^{-3}$) up to more than 100 K for densities of about n$\sim 10^3$ cm$^{-3}$. Recently, a more diffuse, hotter ($n \sim 100$ cm$^{-3}$, $T\sim 250$ K) gas component was discovered through absorption observations of H$_3^+$. This component may be widespread in the Galactic center, and low density gas detectable in absorption may be present even outside the CMZ along sightlines crossing the extended bulge of the Galaxy. Aims: We aim to observe and characterize diffuse and low density gas using observations of 3-mm molecular transitions seen in absorption. Methods: Using the Atacama Large (sub)Millimeter Array (ALMA) we observed the absorption against the quasar J1744-312, which is located towards the Galactic bulge region at $(l,b)=(-2{^\circ}.13,-1{^\circ}.0)$, but outside the main molecular complexes. Results: ALMA observations in absorption against the J1744-312 quasar reveal a rich and complex chemistry in low density molecular and presumably diffuse clouds. We detected three velocity components, at $\sim $ 0, $-153$, and $-192$ km s$^{-1}$. The component at $\sim 0$ km s$^{-1}$ could represent gas in the Galactic disk while the velocity components at $-153$, and $-192$ km s$^{-1}$ likely originate from the Galactic bulge. We detected 12 molecules in the survey, but only 7 in the Galactic bulge gas., Accepted for publication in A&A

The Atacama Large Millimeter/submillimeter Array(ALMA) Band 1 receiver covers the 35-50 GHz frequency band. Development of prototype receivers, including the key components and subsystems has been completed and two sets of prototype receivers were fully tested. We will provide an overview of the ALMA Band 1 science goals, and its requirements and design for use on the ALMA. The receiver development status will also be discussed and the infrastructure, integration, evaluation of fully-assembled band 1 receiver system will be covered. Finally, a discussion of the technical and management challenges encountered will be presented.

Field Programmable Gate Arrays (FPGAs) capacity and Analog to Digital Converters (ADCs) speed have largely increased in the last decade. Nowadays we can find one million or more logic blocks (slices) as well as several thousand arithmetic units (ALUs/DSP) available on a single FPGA chip. We can also commercially procure ADC chips reaching 10 GSPS, with 8 bits resolution or more. This unprecedented power of computing hardware has allowed the digitalization of signal processes traditionally performed by analog components. In radio astronomy, the clearest example has been the development of digital sideband separating receivers which, by replacing the IF hybrid and calibrating the system imbalances, have exhibited a sideband rejection above 40dB; this is 20 to 30dB higher than traditional analog sideband separating (2SB) receivers. In Rodriguez et al.,1 and Finger et al.,2 we have demonstrated very high digital sideband separation at 3mm and 1mm wavelengths, using laboratory setups. We here show the first implementation of such technique with a 3mm receiver integrated into a telescope, where the calibration was performed by quasi-optical injection of the test tone in front of the Cassegrain antenna. We also reported progress in digital polarization synthesis, particularly in the implementation of a calibrated Digital Ortho-Mode Transducer (DOMT) based on the Morgan et al. proof of concept.3 They showed off- line synthesis of polarization with isolation higher than 40dB. We plan to implement a digital polarimeter in a real-time FPGA-based (ROACH-2) platform, to show ultra-pure polarization isolation in a non-stop integrating spectrometer.

Here we describe the status of the upgrade program that is being performed to modernize the Southern 1.2m Wave Telescope. The Telescope was built during early ´80 to complete the first Galactic survey of Molecular Clouds in the CO(1-0) line. After a fruitful operation in CTIO the telescope was relocated to the Universidad de Chile, Cerro Calan Observatory. The new site has an altitude of 850m and allows observations in the millimeter range throughout the year. The telescope was upgraded, including a new building to house operations, new control system, and new receiver and back-end technologies. The new front end is a sideband-separating receiver based on a HEMT amplifier and sub-harmonic mixers. It is cooled with Liquid Nitrogen to diminish its noise temperature. The back-end is a digital spectrometer, based on the Reconfigurable Open Architecture Computing Hardware (ROACH). The new spectrometer includes IF hybridization capabilities to avoid analog hybrids and, therefore, improve the sideband rejection ratio of the receiver.

The ALMA telescope is one of the largest on-ground astronomical projects in the world. It will perform astronomical observations in all the atmospheric windows from 35 to 950 GHz when completed. The ALMA band 1 (35–52 GHz) receiver is in an advanced development state and production may start soon. As for other bands, the receiver is enclosed in a cryostat, where electronics are cooled down for minimum noise temperature operation. However, in the case of band 1, components are large in comparison with cryostat dimensions and aperture sizes. This makes that the best receiver optics designs have the corrugated feed horn very close to the cryostat infrared (IR) filters. This paper discusses the effects of the IR filters on the performance of the ALMA band 1 receiver optics.

In this work we present a Q-band waveguide orthomode transducer (OMT) based on a dual ridge structure. It was designed to be used in astronomical projects were an excellent broad-band performance is mandatory. Of particular interest is the case of ALMA Band 1 (originally set at 31-45 GHz) project which will need several OMTs with outstanding performance and demonstrated manufacturability. By using a symmetrical structure, low cross-polar level and good input matching are achieved over a broad bandwidth (37 %). The proposed design incorporates an octagonal mode converter which allows the unit to be directly mated with the horn avoiding cross-polar issues at the interface. The OMT was designed to have a compact configuration and easiness of fabrication, both crucial features in projects where several units (up to 70) have to be constructed.

Observations of interstellar dust are often used as a proxy for total gas column density $N_\mathrm{H}$. By comparing $\textit{Planck}$ thermal dust data (Release 1.2) and new dust reddening maps from Pan-STARRS 1 and 2MASS (Green et al. 2018), with accurate (opacity-corrected) HI column densities and newly-published OH data from the Arecibo Millennium survey and 21-SPONGE, we confirm linear correlations between dust optical depth $\tau_{353}$, reddening $E(B{-}V)$ and the total proton column density $N_\mathrm{H}$ in the range (1$-$30)$\times$10$^{20}$cm$^{-2}$, along sightlines with no molecular gas detections in emission. We derive an $N_\mathrm{H}$/$E(B{-}V)$ ratio of (9.4$\pm$1.6)$\times$10$^{21}$cm$^{-2}$mag$^{-1}$ for purely atomic sightlines at $|b|$$>$5$^{\circ}$, which is 60$\%$ higher than the canonical value of Bohlin et al. (1978). We report a $\sim$40$\%$ increase in opacity $\sigma_{353}$=$\tau_{353}$/$N_\mathrm{H}$, when moving from the low column density ($N_\mathrm{H}$$$5$\times$10$^{20}$cm$^{-2}$) regime, and suggest that this rise is due to the evolution of dust grains in the atomic ISM. Failure to account for HI opacity can cause an additional apparent rise in $\sigma_{353}$, of the order of a further $\sim$20$\%$. We estimate molecular hydrogen column densities $N_{\mathrm{H}_{2}}$ from our derived linear relations, and hence derive the OH/H$_2$ abundance ratio of $X_\mathrm{OH}$$\sim$1$\times$10$^{-7}$ for all molecular sightlines. Our results show no evidence of systematic trends in OH abundance with $N_{\mathrm{H}_{2}}$ in the range $N_{\mathrm{H}_{2}}$$\sim$(0.1$-$10)$\times$10$^{21}$cm$^{-2}$. This suggests that OH may be used as a reliable proxy for H$_2$ in this range, which includes sightlines with both CO-dark and CO-bright gas., Comment: The revised manuscript is accepted for publication in The Astrophysical Journal

Measurements of microwave attenuation at room temperature and 4.2 K have been performed on some conductors commonly used in receiver input circuits. The reduction in loss on cooling is substantial, particularly for copper and plated gold, both of which showed a factor of 3 loss reduction. Copper passivated with benzotriazole shows the same loss as without passivation. The residual resistivity ratio between room temperature and 4.2 K, deduced from the measurements using the classical skin effect formula, was smaller than the measured DC value to a degree consistent with conduction in the extreme anomalous skin effect regime at cryogenic temperatures. The measurements were made in the 5-10 GHz range. The materials tested were: aluminum alloys 1100-T6 and 6061-O, C101 copper, benzotriazole treated C101 copper, and brass plated with electroformed copper, Pur-A-Gold 125-Au soft gold, and BDT200 bright gold., Comment: 9 pages

Deep spectral-line surveys in the mm and sub-mm range can detect thousands of lines per band uncovering the rich chemistry of molecular clouds, star forming regions and circumstellar envelopes, among others objects. The ability to study the faintest features of spectroscopic observation is, nevertheless, limited by a number of factors. The most important are the source complexity (line density), limited spectral resolution and insufficient sideband (image) rejection (SRR). Dual Sideband (2SB) millimeter receivers separate upper and lower sideband rejecting the unwanted image by about 15 dB, but they are difficult to build and, until now, only feasible up to about 500 GHz (equivalent to ALMA Band 8). For example ALMA Bands 9 (602-720 GHz) and 10 (787-950 GHz) are currently DSB receivers. Aims: This article reports the implementation of an ALMA Band 9 2SB prototype receiver that makes use of a new technique called calibrated digital sideband separation. The new method promises to ease the manufacturing of 2SB receivers, dramatically increase sideband rejection and allow 2SB instruments at the high frequencies currently covered only by Double Sideband (DSB) or bolometric detectors. Methods: We made use of a Field Programmable Gate Array (FPGA) and fast Analog to Digital Converters (ADCs) to measure and calibrate the receiver's front end phase and amplitude imbalances to achieve sideband separation beyond the possibilities of purely analog receivers. The technique could in principle allow the operation of 2SB receivers even when only imbalanced front ends can be built, particularly at very high frequencies. Results: This digital 2SB receiver shows an average sideband rejection of 45.9 dB while small portions of the band drop below 40 dB. The performance is 27 dB (a factor of 500) better than the average performance of the proof-of-concept Band 9 purely-analog 2SB prototype receiver., 5 pages

Bond-wire antennas (BWAs) are an attractive concept for integrated radio front-ends at millimetre-wave frequencies, but have a relatively narrow radiation pattern that makes them less attractive for many applications. In this paper, a circular BWA array antenna concept is presented that has a broad and omnidirectional radiation pattern. The relationship between array geometry and the shape of the gain pattern has been extensively explored through a series of parametric simulations. A prototype was built and measured in order to verify simulation results. The main suggested cause for a difference between simulated and measured data are inaccuracies in the design and manufacturing process of the feed network.

We present the very first detection of N2H+J = (1 – 0) and CH3OH(2k−1k) line emission on 5″ scales in the circumnuclear disk (CND) around Sgr A*. The emission matches the position and shape of the dark clouds in the near-infrared. Our findings suggest that these molecular clouds in the eastern CND are significantly colder and denser than the rest of the CND, and partially shocked. The research on these dark clouds will contribute to understanding the processes of star formation close to a supermassive black hole.

Radio Frequency Interference (RFI) is a growing concern in the radio astronomy community. Single-dish telescopes are particularly susceptible to RFI. Several methods have been developed to cope with RF-polluted environments, based on flagging, excision, and real-time blanking, among others. All these methods produce some degree of data loss or require assumptions to be made on the astronomical signal. We report the development of a real-time, digital adaptive filter implemented on a Field Programmable Gate Array (FPGA) capable of processing 4096 spectral channels in a 1 GHz of instantaneous bandwidth. The filter is able to cancel a broad range of interference signals and quickly adapt to changes on the RFI source, minimizing the data loss without any assumption on the astronomical or interfering signal properties. The speed of convergence (for a decrease to a 1%) was measured to be 208.1 us for a broadband noise-like RFI signal and 125.5 us for a multiple-carrier RFI signal recorded at the FAST radio telescope., Comment: 7 pages

Sideband-separating receivers are usually preferred in the presence of high atmospheric noise. However, one of the most important figures of merit for this kind of receiver, the sideband ratio, is still low and typically around 10 dB. This is because keeping low amplitude and phase imbalances over large RF and IF frequencies is extremely difficult. However, by introducing a digital back-end that mimics the performance of an IF-hybrid, such imbalances can be calibrated out. We have recently presented a digital sideband-separating receiver, working at the W band, that can achieve sideband ratios well above 35 dB. Here we extend this work by demonstrating that it can also be applied to receivers that incorporate a second down-conversion stage with the same performance.

The prototype cartridges for ALMA Band-1 receivers have been developed, based on the key components developed in ALMA Band-1 consortium laboratories. The prototype cartridges for each receiver consist of two parts, cold cartridge assembly and warm cartridge assembly. The cold cartridge assembly (CCA) consists of horn antenna, orthomode transducer and a pair of 35-52 GHz cold low-noise amplifiers, the amplified signals of both polarizations are transmitted to warm cartridge assembly by long waveguide sections. In warm cartridge assembly (WCA), two major modules incorporated, down-converter assembly including warm low-noise amplifier, high-pass filter, mixer and 4-12 GHz IF amplifier, and local oscillator based on a 31-40 GHz YIG-tunes oscillator. The frequency range is based on the upper sideband scheme. Based on the measured performance of the key components, the expected noise performance of the receiver will be 26-33K.

Due to its advantages over other configurations, sideband-separating receivers are usually preferred for radio astronomy, particularly in the presence of high atmospheric noise. However, even with all the advances that have been made in recent years in the field of receiver technology, one of the most important figures of merit for this kind of receiver, the sideband rejection ratio, is still relatively low and typically around 10 to 20 dB. This is because keeping low amplitude and phase imbalances over large RF and IF bands is extremely difficult. In order to overcome this problem, it has been suggested that by introducing a digital back-end that mimics the performance of an IF-hybrid, such imbalances can be calibrated out. Until now, this has been demonstrated only at very low RF frequencies (below 4 GHz). Here, for the first time, we demonstrate that this technique can be applied at higher frequencies. We have implemented a sideband-separating receiver with a calibrated digital IF-hybrid spectrometer for the 3 mm band, and have demonstrated that, even in the presence of large imbalances of individual components, sideband ratios above 35 dB can be obtained in the entire RF band.

A fast moving infrared excess source (G2) which is widely interpreted as a core-less gas and dust cloud approaches Sagittarius A* (SgrA*) on a presumably elliptical orbit. VLT K_s-band and Keck K'-band data result in clear continuum identifications and proper motions of this about 19m Dusty S-cluster Object (DSO). In 2002-2007 it is confused with the star S63, but free of confusion again since 2007. Its near-infrared (NIR) colors and a comparison to other sources in the field speak in favor of the DSO being an IR excess star with photospheric continuum emission at 2 microns than a core-less gas and dust cloud. We also find very compact L'-band emission ($, Comment: 4 pages, 2 figures, Proc. of a Conf. on IAU Symposium No.303: The GC: Feeding and Feedback in a Normal Galactic Nucleus 2013 September 30 - October 4, Santa Fe New Mexico (USA)

In this paper we describe the status of an upgrading program that it is being carried out to modernize the front and back ends of the Southern 1.2-m mm-Wave Telescope to cover eciently the band from 86 to 115 GHz. On the one hand, the new front end will have a sideband-separating conguration to suppress the image band noise. This front end will use one low noise amplier and two Schottky diodes for down conversion. On the other hand, we are developing a modern digital spectrometer, based on the Recongurable Open Architecture Computing Hardware (ROACH), to ease the operation and improve the spectral resolution up to a factor of 4. Moreover, the spectrometer will include IF hybridization capabilities to avoid analog hybrids and, therefore, improve the sideband rejection ratio of the receiver.

The lowest spectroscopic band devised for the Atacama Large Millimeter Array (ALMA), the so-called Band 1, covers the frequency range from 31 to 45 GHz. This band was not implemented during the rst construction phase of the telescope, but will be included during a second ALMA development phase. During the past 4 years our group has been working on the development of technology to cover this band, complying with the demanding ALMA specications. Among the most burdensome challenges are the stringent specications on noise temperature, the large required bandwidth, and the limited space available for this receiver within the ALMA cryostat. In this paper we present some of the technologies we have developed, including the design of key components like horn, lens, ortho-mode transducer, and low noise ampliers. We also present an evaluation of third-party components which can be used in the receiver. The work is used to present a preliminary layout of the Band 1 receiver.

We propose a one-dimensional lattice model, inspired by population dynamics interaction. The model combines a variable coupling range with the Allee effect. The system is capable of exhibiting pattern formation that is similar to what occurs in similar continuous models for population dynamics. However, the formation features are quite different; in this case the pattern emerges from a disorder state via intermittence. We analytically estimated the selected wavelength of the formed pattern and numerically studied fluctuations around the mean wavelength. We also comment on the relationship between intermittence and the edge of chaos as well as sensitivity to initial conditions. Next, we present an analytical prediction of the influence of the world size on the intermittent regime which is in good agreement with the numerical observations. Moreover, the last calculation provided us an alternative way to compute the pattern wavelength. Finally, we discuss the continuous limit of our lattice model.

We have mapped the Orion-A Giant Molecular Cloud in the CO (J=4-3) line with the Tsukuba 30-cm submillimeter telescope.The map covered a 7.125 deg^2 area with a 9' resolution, including main components of the cloud such as Orion Nebula, OMC-2/3, and L1641-N. The most intense emission was detected toward the Orion KL region. The integrated intensity ratio between CO (J=4-3) and CO (J=1-0) was derived using data from the Columbia-Univ. de Chile CO survey, which was carried out with a comparable angular resolution. The ratio was r_{4-3/1-0} ~ 0.2 in the southern region of the cloud and 0.4-0.8 at star forming regions. We found a trend that the ratio shows higher value at edges of the cloud. In particular the ratio at the north-eastern edge of the cloud at (l, b) = (208.375 deg, -19.0 deg) shows the specific highest value of 1.1. The physical condition of the molecular gas in the cloud was estimated by non-LTE calculation. The result indicates that the kinetic temperature has a gradient from north (Tkin=80 K) to south (20 K). The estimation shows that the gas associated with the edge of the cloud is warm (Tkin~60 K), dense (n_{H_2}~10^4 cm^{-3}), and optically thin, which may be explained by heating and sweeping of interstellar materials from OB clusters., 12 pages, 11 figures; Accepted for publication in PASJ

We have extended the modified formalism of Sheng, Xing, and Wang@J. Phys.: Condens. Matter11 L299 ~1999!# to allow the calculation of the conductivity of a thin metallic film bounded by a rough fractal surface. We utilized the so-called k-correlation model proposed by Palasantzas and Barnas @Phys. Rev. B 48, 14 472 ~1993!; 56, 7726 ~1997!#, to describe the height-height autocorrelation function corresponding to a self-affine roughness. This extension permits the calculation of the conductivity of the film as a function of the r.m.s. roughness amplitude d, of the lateral correlation length j, of the mean free path in the bulk l, and of the roughness exponent H. We found that the degree of surface irregularity, represented by the roughness exponent H characterizing the surface, does influence the conductivity of the film, as first discovered by Palasantzas and Barnas. However, this influence manifests itself for large bulk mean free paths l’1000 nm and for large correlation lengths j’5 nm, in which case the conductivity of the film for H51 exceeds by about 30% the conductivity for H50.2, an effect which is smaller than that reported by Palasantzas and Barnas. For correlation lengths j below 1 nm and mean free paths l’100 nm, the influence of the roughness exponent H on the conductivity is reduced to below 10%, and for smaller mean free paths and correlation lengths the conductivity becomes insensitive to H. We also found that Mathiessen’s rule is severily violated in the case of thin metallic films. The resistivity of the film coincides roughly with the surface-limited resistivity only in the case of ultrathin films t,5 nm. For thicker films 100 nm.t.5 nm, the resistivity of the film exceeds by some 20 to 30 % the value dictated by Mathiessen’s rule. And conversely, the apparent surface-induced resistivity estimated assuming the validity of Mathiessen’s rule, exceeds by nearly one order of magnitude the true surfaceinduced resistivity, except in the case of ultrathin films t, 5n m.

The Band-1 receiver front-end cartridges for Atacama Large Millimeter Array, which covered 35–50 GHz frequency range, are now in preproduction stage. For the first three preproduction cartridges, the measured receiver noise temperature is less than 16–31K for any combination of the inband RF and LO frequencies. The measured gain flatness, even with the limitation of the optical window of the cryostat and the broadband matching of the cryogenic amplifiers, is typically lower than 5 dB over any 2GHz window. Extracted aperture beam efficiency is typically higher than 80% over the full frequency range. The crosstalk over the orthogonal channel is lower than −63 dB. For the suppression of the unwanted lower sideband, the imaged band suppression is higher than 20 dB for the worst case and around 30 dB typically.