63 research outputs found
A Low-Cost L-Band Line Amplifier (Rev. 1)
This report documents the design of a low-cost L-band line amplifier. The description presented here is complete, although the design is a minor revision to a design previous reported in [1]. The change is a reduction in size and a modification to the enclosure to reduce cost. The cost of the new design is about $44 each in small quantities. Although this unit is intended to be used in conjunction with the LNA described in [2], it may also be useful in other applications. Specifically, this unit provides a 9 VDC bias through the RF input jack which can be used to power the LNA described in [2]. The intended configuration is for the line amplifier to be located within a few feet of the LNA, and used to drive a long section (e.g., 100 ft.) of coaxial cable. The completed line amplifier is shown in Figure 1 and its specifications are summarized in Figures 2, 3, and 4. Figure 5 shows a schematic of the line amplifier, with a parts list given in Figure 6. Components L1 and C1 form a bias-tee, setting the DC voltage at the input jack to 9 VDC, thereby powering the connected LNA. This part of the circuit also forms a high-pass filter with cutoff at about 200 MHz, which contibutes to the suppression of strong VHF-band interference, such as FM broadcast radio. MMIC amplifiers U1 and U2 provide gain and also serve to buffer the stripline bandpass filter, FL1. Figure 7 shows the assembled circuit on its printed circuit board (PCB). FL1 is a 3-finger interdigital bandpass filter which was designed through a process of trial-and-error using the āSonnet ā electromagnetic modeling software by Sonne
Digital Receiver for Microwave Radiometry
A receiver proposed for use in L-band microwave radiometry (for measuring soil moisture and sea salinity) would utilize digital signal processing to suppress interfering signals. Heretofore, radio frequency interference has made it necessary to limit such radiometry to a frequency band about 20 MHz wide, centered at .1,413 MHz. The suppression of interference in the proposed receiver would make it possible to expand the frequency band to a width of 100 MHz, thereby making it possible to obtain greater sensitivity and accuracy in measuring moisture and salinit
GBTrans: A commensal search for radio pulses with the Green Bank twenty metre telescope
We describe GBTrans, a real-time search system designed to find fast radio
bursts (FRBs) using the 20-m radio telescope at the Green Bank Observatory. The
telescope has been part of the Skynet educational program since 2015. We give
details of the observing system and report on the non-detection of FRBs from a
total observing time of 503 days. Single pulses from four known pulsars were
detected as part of the commensal observing. The system is sensitive enough to
detect approximately half of all currently known FRBs and we estimate that our
survey probed redshifts out to about 0.3 corresponding to an effective survey
volume of around 124,000~Mpc. Modeling the FRB rate as a function of
fluence, , as a power law with , we constrain the index at the 90% confidence level. We discuss the implications of this result
in the context of constraints from other FRB surveys.Comment: 7 pages, 6 figure
The Radio Sky at Meter Wavelengths: m-Mode Analysis Imaging with the Owens Valley Long Wavelength Array
A host of new low-frequency radio telescopes seek to measure the 21-cm
transition of neutral hydrogen from the early universe. These telescopes have
the potential to directly probe star and galaxy formation at redshifts , but are limited by the dynamic range they can achieve
against foreground sources of low-frequency radio emission. Consequently, there
is a growing demand for modern, high-fidelity maps of the sky at frequencies
below 200 MHz for use in foreground modeling and removal. We describe a new
widefield imaging technique for drift-scanning interferometers,
Tikhonov-regularized -mode analysis imaging. This technique constructs
images of the entire sky in a single synthesis imaging step with exact
treatment of widefield effects. We describe how the CLEAN algorithm can be
adapted to deconvolve maps generated by -mode analysis imaging. We
demonstrate Tikhonov-regularized -mode analysis imaging using the Owens
Valley Long Wavelength Array (OVRO-LWA) by generating 8 new maps of the sky
north of with 15 arcmin angular resolution, at frequencies
evenly spaced between 36.528 MHz and 73.152 MHz, and 800 mJy/beam thermal
noise. These maps are a 10-fold improvement in angular resolution over existing
full-sky maps at comparable frequencies, which have angular resolutions . Each map is constructed exclusively from interferometric observations
and does not represent the globally averaged sky brightness. Future
improvements will incorporate total power radiometry, improved thermal noise,
and improved angular resolution -- due to the planned expansion of the OVRO-LWA
to 2.6 km baselines. These maps serve as a first step on the path to the use of
more sophisticated foreground filters in 21-cm cosmology incorporating the
measured angular and frequency structure of all foreground contaminants.Comment: 27 pages, 18 figure
Transient Pulses from Exploding Primordial Black Holes as a Signature of an Extra Dimension
An evaporating black hole in the presence of an extra spatial dimension would
undergo an explosive phase of evaporation. We show that such an event,
involving a primordial black hole, can produce a detectable, distinguishable
electromagnetic pulse, signaling the existence of an extra dimension of size
m. We derive a generic relationship between the
Lorentz factor of a pulse-producing "fireball" and the TeV energy scale. For an
ordinary toroidally compactified extra dimension, transient radio-pulse
searches probe the electroweak energy scale (0.1 TeV), enabling
comparison with the Large Hadron Collider.Comment: 11 pages, 1 figure; references added; typos corrected; clarifying
remarks added near the end of section
The Radio Sky at Meter Wavelengths: m-mode Analysis Imaging with the OVRO-LWA
A host of new low-frequency radio telescopes seek to measure the 21 cm transition of neutral hydrogen from the early universe. These telescopes have the potential to directly probe star and galaxy formation at redshifts 20 ā³ z ā³ 7 but are limited by the dynamic range they can achieve against foreground sources of low-frequency radio emission. Consequently, there is a growing demand for modern, high-fidelity maps of the sky at frequencies below 200 MHz for use in foreground modeling and removal. We describe a new wide-field imaging technique for drift-scanning interferometers: Tikhonov-regularized m-mode analysis imaging. This technique constructs images of the entire sky in a single synthesis imaging step with exact treatment of wide-field effects. We describe how the CLEAN algorithm can be adapted to deconvolve maps generated by m-mode analysis imaging. We demonstrate Tikhonov-regularized m-mode analysis imaging using the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) by generating eight new maps of the sky north of Ī“ = ā30Ā° with 15' angular resolution at frequencies evenly spaced between 36.528 and 73.152 MHz and ~800 mJy beam^(ā1) thermal noise. These maps are a 10-fold improvement in angular resolution over existing full-sky maps at comparable frequencies, which have angular resolutions ā„2Ā°. Each map is constructed exclusively from interferometric observations and does not represent the globally averaged sky brightness. Future improvements will incorporate total power radiometry, improved thermal noise, and improved angular resolution due to the planned expansion of the OVRO-LWA to 2.6 km baselines. These maps serve as a first step on the path to the use of more sophisticated foreground filters in 21 cm cosmology incorporating the measured angular and frequency structure of all foreground contaminants
Glioma Through the Looking GLASS: Molecular Evolution of Diffuse Gliomas and the Glioma Longitudinal AnalySiS Consortium
Adult diffuse gliomas are a diverse group of brain neoplasms that inflict a high emotional toll on patients and their families. The Cancer Genome Atlas (TCGA) and similar projects have provided a comprehensive understanding of the somatic alterations and molecular subtypes of glioma at diagnosis. However, gliomas undergo significant cellular and molecular evolution during disease progression. We review the current knowledge on the genomic and epigenetic abnormalities in primary tumors and after disease recurrence, highlight the gaps in the literature, and elaborate on the need for a new multi-institutional effort to bridge these knowledge gaps and how the Glioma Longitudinal AnalySiS Consortium (GLASS) aims to systemically catalog the longitudinal changes in gliomas. The GLASS initiative will provide essential insights into the evolution of glioma toward a lethal phenotype, with the potential to reveal targetable vulnerabilities, and ultimately, improved outcomes for a patient population in need
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