scholarly journals 3.29. Radio recombination lines from starburst galaxies

1998 ◽  
Vol 184 ◽  
pp. 147-148
Author(s):  
K.R. Anantharamaiah
Keyword(s):  
Millimeter Wave ◽  
Dynamic Range ◽  
Starburst Galaxies ◽  
Aperture Synthesis ◽  
Emission Region ◽  
Full Extent ◽  
Radio Recombination Lines

Starburst activity is often heavily obscured by dust. To see through the dust and measure the full extent, power and dynamics of the starburst, we are surveying hydrogen radio recombination lines (RRLs) from famous nearby starburst galaxies. Exploiting the improved sensitivity and dynamic range of aperture synthesis arrays such as the VLA and the AT and millimeter-wave telescopes such as SEST and the IRAM-30m telescope, we have searched for RRLs in about 25 starburst galaxies. RRLs have been detected in 14 galaxies. The observations were made variously at 1.4, 4.9, 8.4, 86, 135 and 232 GHz (Anantharamaiah et al 1993, Zhao et al 1996, 1997, Phookun et al 1997). Table 1 summarizes the observations. In all the cases the detected line originates in the nuclear starburst region and the emission region is resolved with a beam of 1–3″.

scholarly journals Radio Recombination Lines from Starburst Galaxies: High and Low Density Ionized Gas

2002 ◽  
Vol 199 ◽  
pp. 243-244
Author(s):  
N.R. Mohan ◽  
K.R. Anantharamaiah ◽  
W.M. Goss
Keyword(s):  
Flux Density ◽  
Hii Regions ◽  
Starburst Galaxies ◽  
High Density ◽  
The Other ◽  
Low Density ◽  
Ionized Gas ◽  
Density Measurements ◽  
Radio Recombination Lines ◽  
Upper Limits

Radio recombination lines (RRL) at 8 GHz and 15 GHz detected from four starburst galaxies are shown to arise in compact high density HII regions, which are undetectable below ∼4 GHz. Detection of an RRL at 1.4 GHz towards one galaxy and upper limits in the other three are consistent with the presence of an equal amount of low density diffuse gas. Continuum flux density measurements using the GMRT will be important in constraining the properties of the diffuse gas.

scholarly journals Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization

2009 ◽  
Vol 80 (10) ◽  
pp. 103504 ◽  
Author(s):  
D. J. Thoen ◽  
W. A. Bongers ◽  
E. Westerhof ◽  
J. W. Oosterbeek ◽  
M. R. de Baar ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Millimeter Wave ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Spectral Diagnostics ◽  
High Dynamic

scholarly journals Practical Hybrid Beamforming for Millimeter Wave Massive MIMO Full Duplex with Limited Dynamic Range

2021 ◽  
Author(s):  
Chandan Kumar Sheemar ◽  
Christo Kurisummoottil Thomas ◽  
Dirk Slock
Keyword(s):  
Millimeter Wave ◽  
Massive Mimo ◽  
Dynamic Range ◽  
Full Duplex ◽  
Noise Model ◽  
Noise Variance ◽  
Power Constraints ◽  
Half Duplex ◽  
Hybrid Beamforming ◽  
Weighted Sum Rate

Full-Duplex (FD) communication can revolutionize wireless communications as it doubles spectral efficiency and offers numerous other advantages over a half-duplex (HD) system. In this paper, we present a novel and practical joint hybrid beamforming (HYBF) and combining scheme for millimeter-wave (mmWave) massive MIMO FD system for weighted sum-rate (WSR) maximization with multi-antenna HD uplink and downlink users with non-ideal hardware.<br>Moreover, we present a novel interference and self-interference (SI) aware optimal power allocation scheme for the optimal beamforming directions. The analog processing stage is assumed to be quantized, and both the unit-modulus and unconstrained cases are considered.<br>Moreover, compared to the traditional sum-power constraints, the proposed algorithm is designed under the joint sum-power and the practical per-antenna power constraints. To model the non-ideal hardware of a hybrid FD transceiver, we extend the traditional limited dynamic range (LDR) noise model to mmWave. Our HYBF design relies on alternating optimization based on the minorization-maximization method. <br>We investigate the maximum achievable gain of a hybrid FD system with different levels of the LDR noise variance and with different numbers of radio-frequency (RF) chains over a HD system. Simulation results show that the mmWave massive MIMO FD systems can significantly outperform the fully digital HD systems with only a few RF chains if the LDR noise generated from the limited number of RF chains available is low. If the LDR noise variance dominates, FD communication with HYBF results to be disadvantageous than a HD system. <br>

scholarly journals 1-Bit/2-Level Analog-to-Digital Conversion Based on Comparator and FPGA for Aperture Synthesis Passive Millimeter-Wave Imager

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 51933-51939 ◽  
Author(s):  
Xiangzhou Guo ◽  
Ghulam Mehdi ◽  
Muhammad Asif ◽  
Anyong Hu ◽  
Jungang Miao
Keyword(s):  
Millimeter Wave ◽  
Aperture Synthesis ◽  
Digital Conversion ◽  
Analog To Digital ◽  
Analog To Digital Conversion
Sign in / Sign up

Export Citation Format

Share Document