Crawford Hill Research Articles

New Measurements of Fine‐Scale CMB Polarization Power Spectra from CAPMAP at Both 40 and 90 GHz

We present new measurements of the cosmic microwave background (CMB) polarization from the final season of the Cosmic Anisotropy Polarization MAPper (CAPMAP). The data set was obtained in winter 2004-2005 with the 7 m antenna in Crawford Hill, New Jersey, from 12 W-band (84-100 GHz) and 4 Q-band (36-45 GHz) correlation polarimeters with 3.3' and 6.5' beamsizes, respectively. After selection criteria were applied, 956 (939) hours of data survived for analysis of W-band (Q-band) data. Two independent and complementary pipelines produced results in excellent agreement with each other. A broad suite of null tests as well as extensive simulations showed that systematic errors were minimal, and a comparison of the W-band and Q-band sky maps revealed no contamination from galactic foregrounds. We report the E-mode and B-mode power spectra in 7 bands in the range 200 < l < 3000, extending the range of previous measurements to higher l. The E-mode spectrum, which is detected at 11 sigma significance, is in agreement with cosmological predictions and with previous work at other frequencies and angular resolutions. The BB power spectrum provides one of the best limits to date on B-mode power at 4.8 uK^2 (95% confidence).

The CAPMAP instrument and its first season

I describe here the new Cosmic Anisotropy Polarization MAPer (CAPMAP) instrument, which performed its first season of observing between February and April 2003 from the Crawford Hill 7-m antenna in NJ. CAPMAP is based on the design for the PIQUE instrument, but has better sensitivity and superior angular resolution.

The Ku-band polarization identifier

The Ku-band polarization identifier (KUPID) will integrate a very low noise 12–18 GHz, correlation polarimeter onto the Crawford Hill seven meter, millimeter-wave antenna. The primary components of the polarimeter will be built at the University of Miami and other key components, including the microwave horn and data acquisition system will be built at the University of Chicago and Princeton University. This project will measure the Q and U Stokes parameters in regions near the north celestial pole, in regions of low galactic contamination, and in regions near the galactic plane. The KUPID survey experiment makes use of many of the techniques employed in the Princeton IQU experiment (PIQUE) that was developed by the members of this collaboration to detect CMB polarization at shorter wavelengths. The KUPID experiment will be constructed in parallel and on the same timescale as the CAPMAP experiment (see Barkats, this volume) which is the follow-on experiment to PIQUE. KUPID will observe on the Crawford Hill antenna from late spring until early autumn, while CAPMAP will observe during the lower water vapor months of late autumn until early spring.

Effect of antenna polarization on the capacity of a multiple element system in an indoor environment

We analyze the behavior of a multiple element antenna system in an indoor environment based on the measurements taken in the Lucent Bell Labs building in Crawford Hill, NJ, with a system of 12 transmitters and 15 receivers. In particular, we investigate the capacity behavior with respect to the polarization of the transmitting/receiving elements and the distance between the transmitting and the receiving arrays. The analysis of the power rolloff versus distance clearly demonstrates the different propagation characteristics of the horizontally versus the vertically polarized electric fields. Under strong line-of-sight (LOS) conditions (hallway environment), the power of the horizontally polarized waves falls off faster with distance than that of the vertically polarized fields. Also, the cross-polarization coupling is about -15 dB. Under nonline-of-sight (NLOS) conditions (labs), both polarizations display similar rolloff behavior with distance and the cross-polarization coupling is about 0 dB. There is a power loss of at least 15 dB under NLOS conditions relative to LOS conditions. The average received signal power affects the system capacity. In the hallway, horizontally polarized systems achieve lower capacities than their vertically polarized counterparts. Also the achievable capacity in the labs is much lower than that in the hallway, because of the lower average received power. The comparison of single polarization systems to hybrid polarization systems shows that combined polarization systems perform better in terms of achievable capacity. Therefore, there lies an advantage in using both electric field polarizations. However, under strong LOS conditions the channel itself inherently limits the capacity behavior of the system.

Bell Labs Had Role in EDFA Development

The interesting recent article on Bell Labs, Lucent Technologies (Physics Today, Physics Today 0031-9228 54 10 2001 26 https://doi.org/10.1063/1.1420546. October 2001, page 26 ), omitted an important detail. Although the article lists some of Bell Labs’ major achievements, including optical solitons, it does not mention erbium-doped fiber amplifiers (EDFAs). Despite their usefulness in improving our understanding of fiber nonlinearities and of new ways to exploit them, solitons have had only a limited impact on optical communications applications. EDFAs, however, have been key to enabling wavelength-division multiplexing technologies, broadband optical networks, and terabits-per-second terrestrial and undersea communications.EDFAs were developed simultaneously at Southampton University and at Bell Labs, according to Herwig Kogelnik. 1 1. N. Savage, IEEE Spectrum 38 (June 2001), p. 43. https://doi.org/10.1109/6.925266 His testimony is authoritative because he directed one of the two Bell Labs facilities in Crawford Hill, New Jersey, where the group of early EDFA investigators worked (1986–1990). The Crawford Hill investigations and demonstrations led to a rapid technology transfer to the Labs’ submarine-link department in Holmdel, New Jersey, and to several other development sites thereafter. (Research on solitons also benefited greatly from the transfer!) That transfer was the culmination of 20 years of fiber-optic research at Bell Labs and probably represents one of the company’s greatest success stories.For my contribution to this early work, I received, jointly with the University of Southampton’s David N. Payne, the 1998 Benjamin Franklin Medal in Engineering. Yet, for unexplained reasons, Bell Labs never claimed its contribution to the invention and early development of EDFAs, despite their tremendous impact on technology and business. Such an anomaly, or memory erasure, shows that historical accuracy, even in famed institutions, can become secondary to internal rivalries (“not started in my department”) or marketing simplifications (“EDFAs have always been there”). True, practically all the early EDFA investigators have left the Labs, and the submarine group established its own company. But could this evolution justify censorship in Bell Labs’ history? The Labs should be proud of having been on the forefront of another technology revolution, thanks to the vision and risk-taking stance of both investigators and managers of Crawford Hill.I recommend the National Academy of Sciences Web site, http://www4.nationalacademies.org/beyond/beyonddiscovery.nsf, which lists, under the Modern Communications menu item, pages titled “Basic Research Remains Vital” and “The Development of Lasers and Fiber-Optics—A Chronology of Selected Events.” Those state that Southampton University and Bell Labs discovered and developed “practical and effective” EDFAs.REFERENCESSection:ChooseTop of pageREFERENCES <<1. N. Savage, IEEE Spectrum 38 (June 2001), p. 43. https://doi.org/10.1109/6.925266 , Google ScholarCrossref© 2002 American Institute of Physics.

Propagation measurements for fixed wireless loops (FWL) in a suburban region with foliage and terrain blockages

We present the results of propagation measurements at 2.485 GHz for fixed wireless loops. Path loss measurements were performed and characterized at 43 subscriber locations around a base station antenna located on top of Crawford Hill in Holmdel, NJ. This suburban location is characterized by rolling hills, foliage, and terrain blockages. Temporal and horizontal motion path loss fluctuations were found to be uncorrelated, each characterized by a different Ricean distribution. Lower r.m.s. delay spreads were obtained with directive subscriber antennas than with omni-directional antennas. No substantial gain loss (less than 2 dB) of subscribers' directive antennas was observed. The effects of trees, with foliage, surrounding the base station upon the path loss and the ratio of scattered power to specular power are also examined. The distance exponent of path loss versus distance (about 1.5) was observed to be less than free-space. Diffraction loss from hilltop trees, shadowing the base station, are suspected to be the cause. This loss decreases as the remote moves further away and comes out of the shadow. Scattered power from directions other than line-of-sight was observed to be as high as one half of the specular contribution when tree scattering near the base station was significant.

Initial estimation of communication efficiency of indoor wireless channels

We report theoretical/numerical estimation of ultimate limits of bandwidth efficient delivery of high bit-rate digital signals indoors. Specifically, we analyze the Crawford Hill Bell Laboratories building. Single omni transmit and receive antennas are assumed. The signals incur attenuation and distortion due to multipath and at high bit-rates this frequency selectivity causes ISI. Moreover, there is impairment by gaussian noise. Transmit power and bandwidth constraints limit communications efficiency. We illustrate this limiting of efficiency in examples assuming 5.2 GHz carrier, 10 MHz bandwidth and up to 1 W transmitted power. The experimentally based WiSE ray-tracing tool models the channels from a base on the ceiling to workspaces in various rooms. Movement within a workspace causes channel changes. Computing the probability distribution of capacity shows substantial capacity for the omni-omni case with 10 MHz bandwidth for 100 mW transmitted. For the most distant offices, for at least 95% of the area in a workspace, we obtain 3.6 bps/Hz. We also examine diversity methods, illustrating substantial gains with nth order optimum combining (OC(n)):OC(2) improves capacity by over 35% in rooms where capacity is the lowest while OC(4) improves it 70%. We put the results in a pragmatic perspective by highlighting the bit-rates achievable with decision feedback equalization

Atmospheric emission measurements of attenuation by microwave radiometer at 19.4 GHz

Attenuation measurements on an Earth space path are presented using a passive microwave radiometer operating at 19.4 GHz in the emission mode. Attenuation measured under clear weather showed variation between 0.2 to 1.1 dB, whereas for cloud conditions attenuation as high as 1.0 dB have been recorded. Attenuation measurements for rain events have been correlated with rainfall rate using a fast-response 10 seconds opto-electronic rain gauge. The values of attenuation versus rainfall rate varied between A (dB)=0.01+0.18 R(mm/h) at the minimum and A (dB)=0.01+0.25 R(mm/h) at the maximum, showing considerable variability in the values of attenuation from year to year. The attenuation statistics for different seasons have also been computed and they show considerable changes from season to season-the largest attenuation in excess of 10 dB recorded in July-August-September, whereas minimum attenuation in excess of 2 dB recorded in December-March for nearly two years of data. Comparison of measurements made over New Delhi with those reported elsewhere show that for 0.02% of time attenuation values lie between those of Slough, England, and Crawford Hill, NJ. The concept of effective path length has been discussed based on the relationship between effective path length and the rain rate.

A theoretical model for radio signal attenuation inside buildings

A theoretical model is proposed for predicting path loss inside buildings. The theory involves a waveguide model of the indoor environment which permits a rigorous modal solution similar to that developed by Mahmoud and Wait (1974) for propagation in tunnels. Comparisons of the theory with the measurements made by Arnold, Murray and Cox (1989) at the AT&T Laboratories building in Crawford Hill, NJ, show general agreement.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Bell Laboratories H I survey

We present a galactic survey which to date consists of 73,000 positions covering −5° < l < 122°, −1° < b < 1° , observed in the J=1 → 0 line of 13CO to an rms noise level of 0.15 K in 0.68 km s−1 channels, using the 7 m antenna at Crawford Hill. It is shown that the internal velocity dispersions of molecular clouds tend to vary inversely with galactocentric radius.

Broadband Gigabit Research and the LuckyNet Testbed

This paper describes the motivation, architecture, initial applications, and objectives for LuckyNet, an AT&T Bell Labs gigabit research network. Building upon the B-ISDN infrastructure of SONET transport and the ATM packet protocol, LuckyNet will provide a fertile testbed for investigating: broadband applications, network architectures, gigabit packet switches and LANs, high-throughput protocols and interfaces, and network services and operations (including addressing, routing, signaling, control and security).LuckyNet is a heterogeneous network that has as one of its major objectives the demonstration that diverse classes of user traffic (i.e., video, voice, data, and image), as well as control and management information can efficiently utilize a single ATM infrastructure. Another goal is to provide users with gigabit-per-second network access. Initial applications provide 155 Mbps access and include video conferencing, document retrievaL low-latency processor-sharing, and Ethernet interconnection. We expect that this will be followed by FDDI interconnection and multimedia conferencing, with the long-range goal of identifying and supporting gigabit-per-second applications. Extensions to other locations and interworking with NREN sites (e.g., AT&T Bell Labs XUNET II) are anticipated. The network already links the Holmdel and Crawford Hill Laboratories (via optical fiber) and the Crawford Hill and Murray Hill Laboratories (via microwave radio) at 2.5 Gbps.

Molecules in Galaxies: Results from Bell Laboratories

AbstractA decade of galaxy observations at the Crawford Hill 7 m antenna are summarized. Significant results include the mapping of spiral arms in CO, the demonstration that gas in many spiral galaxies is roughly half atomic and half molecular, the detection of extragalactic HCO+, CS, 13CO and C18O, and the observation of molecular material in the halo of M82.

Molecular Line Observations of the Galactic Center Region

A decade of galactic center observations at the Crawford Hill 7 m antenna is summarized. The galactic center region contains several hundred high-mass, high-density molecular clouds with physical properties very different from clouds in the outer galactic disk. There is also a considerable amount of molecular gas not bound into clouds, but sheared by differential rotation into a molecular inter-cloud medium not seen elsewhere in the Galaxy. These observations can be explained by a combination of the tidal density limit and the virial theorem. The distribution of emission on the sky and in velocity suggests that most of the dense gas is confined to a 500 pc long ridge of emission which may be a dust lane along the central bar.

1970 Fiber optics: Low-loss fibers, reliable lasers, and millimeter-wave research joined to create optical communication

Charles Burrus, a millimeter-wave diode expert, and three dozen other millimeter-waveguide investigators, sat expectantly in the Bell Laboratories' conference room at the Crawford Hill Laboratory in Holmdel, N.J. It was mid-1963. Microwave division leader Stewart E. Miller stood up and announced that the research group would be redirecting its efforts from millimeter-wave guides to guided-wave optical communications, and that people should finish all pending projects and then set about re-equipping the laboratory. “We went into optics by fiat,” Burrus recalled.

The Bell Laboratories CO Survey: Star Formation in Spiral Arms

We present a galactic survey which to date consists of 47,000 positions covering −3° &lt; l &lt; 122°, −1° &lt; b &lt; 1°, observed in the J= 1→ 0 line of 13CO to an rms noise level of 0.15 K in 0.68 km s−1 channels, using the 7 m antenna at Crawford Hill. Maps made from the survey data show a clear difference between spiral arm and interarm regions. The signature of spiral structure on kiloparsec scales is the presence in galactic survey data of voids in l, b, v space which contain many times fewer Giant Molecular Clouds (GMCs) than do adjacent regions of similar size. The difference between arm and interarm regions in the inner galaxy is manifested only in the GMCs — small clouds are present throughout. These results are based on catalogs of clouds and their estimated sizes in 13CO. We suggest that GMCs are formed as interstellar gas enters a spiral arm, and that they break up into small molecular or atomic clouds as the gas leaves the arm.

Comparison of measured cross‐polarization isolation and discrimination for rain and ice on a 19‐GHz space‐earth path

Rain and ice in a radio path can couple power from a wave transmitted with a given polarization into the orthogonal polarization. At any point along a path, the ratio of the cross‐polarized signal component to the copolarized signal component is defined as depolarization or as cross‐polarization discrimination. Cross‐polarization isolation is the ratio of the cross‐polarized signal component from one transmitted polarization to the copolarized signal component for the orthogonal transmitted polarization. The two signal components that determine cross‐polarization isolation are received on the same polarization. In contrast, the two signal components that determine cross‐polarization discrimination are received on orthogonal polarizations. Conventional single‐polarization propagation experiments can only measure cross‐polarization discrimination. However, cross‐polarization isolation is the quantity that limits the performance of dual‐polarized communication systems. Simultaneous measurements of copolarized and cross‐polarized signal components for two orthogonal linear polarizations were made at Crawford Hill, New Jersey, by using polarization‐switched 19‐GHz beacons on COMSTAR satellites. Data from this experiment are used to show that instantaneous values of cross‐polarization discrimination and cross‐polarization isolation are equal. This is the first known experimental demonstration of this equality for a space‐earth propagation path.

Local Contributions to the 0.6 keV Diffuse X-Ray Background

The intensity of the X-ray background between 0.5 and 1.0 keV has surprisingly little dependence on galactic latitude. Possible mechanisms for the production of these X-rays include extragalactic emission and emission from dM stars, both of which should be strongly dependent on galactic latitude, and diffuse emission from hot gas (T ≃ 3 x 106 K) surrounding the Sun. These mechanisms can be distinguished by the presence or absence of absorption by gas within a few hundred parsecs of the Sun. We use X-ray data from the HEA0-1 LED detectors and HI data from the recent Crawford Hill 21 cm survey to place limits on the 0.6 keV intensity originating within 300 pc of the Sun in the general direction of (l,b) = (150°, -30°).

An imaging beam waveguide feed

A pseudo-frequency-independent beam waveguide feed has been designed and built to accommodate a new liquid-helium-cooled millimeter wave radio astronomy receiver in the side cab of the Crawford Hill 7-m antenna. This enables the antenna to be tilted without tilting the liquid-filled receiver. Comparison with the old vertex-cab feed indicates very little measured transmission loss through the beam waveguide. The frequency independence is based upon the Fresnel zone imaging principle. Design procedures and practical bandwidth limitations are explained. An explicit expression for the third-order term of an offset reflector surface clarifies the approximation of a lens by an offset reflector.

Rain attenuation and depolarization over an earth-space path at 12 GHz: Experimental results using the CTS beacon

Measurements of attenuation and depolarization, primarily due to rain, of the 12-GHz communication technology satellite (CTS) beacon have been made at Crawford Hill, Holmdel, NJ. The measurement system used a 6-m aperture, fully steerable, horn reflector antenna fitted with a dual-sense circular polarized feed. The amplitudes of the copolarized and cross-polarized signal components were measured with a two-branch, stable, narrowband, frequency tracking receiver. Measured data for a 3 1/2 year period beginning April 1976 show significant year-to-year variation in copolarized rain attenuation. For example, at a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">27\deg</tex> path elevation angle, the time over which a 10 dB attenuation was exceeded varied between 47 and 120 min/year. The depolarization showed a decrease with increasing copolarized rain attenuation and lower path elevation angle. At an attenuation of 10 dB and an elevation angle of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">27\deg</tex> , a median depolization level of -15 dB were measured. This decreased to -13 dB at a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9\deg</tex> elevation angle for the same attenuation.

Gain of corrugated conical horns

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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30.8 \pm 0.16 dB</tex> . 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.