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Proceedings ArticleDOI

Millimeter-wave wireless power transfer technology for space applications

16 Dec 2008-pp 1-4

Abstract: Technologies enabling the development of compact systems for wireless transfer of power through radio frequency waves (RF) continue to be important for future space based systems. For example, for lunar surface operation, wireless power transfer technology enables rapid on-demand transmission of power to loads (robotic systems, habitats, and others) and eliminates the need for establishing a traditional power grid. A typical wireless power receiver consists of an array of rectenna elements. Each rectenna element consists of an antenna together with a high speed diode and a storage capacitor configured in a highly tuned narrowband circuit for this purpose. The conversion of the microwave energy into DC in this fashion is almost instantaneous. Using a high power rectenna array in concert with a fast charging high performance battery can enable charging of the battery at very short time with a large power burst and discharge of it at a lower rate for an extended operation time for remote electronic assets. We have designed and fabricated a novel T-Slot antenna coupled rectenna array at 94 GHz for demonstrating efficient wireless power transfer in this frequency band. Assembly and testing of these devices are under progress now, and are showing great promise.
Topics: Rectenna (73%), Wireless power transfer (64%), Antenna (radio) (55%), Radio frequency (53%), Wireless (52%)

Summary (2 min read)

Introduction

  • Two main factors that determine the physical size of a rectenna based microwave power conversion system are the frequency of the RF transmission and power capacity.
  • At higher frequencies, the size of the antenna elements in the array is small resulting in a smaller form factor for the system.
  • This network is fabricated over the slot array using additional layers SiO2 and Au which act as the dielectric and metal layers for the microstrip lines.
  • This power density is 30 times better than high efficiency solar arrays with power density of 40 mW per square centimeter [3].

Slot Antenna Array Design

  • A highly desirable solution to the efficient wireless power transfer would be to fabricate monolithic array of antenna-coupled detectors on a planar substrate [4].
  • This does not preclude their use in large arrays; however, manufacturing and assembly of such arrays are not straight forward.
  • Fig. 1 shows the general concept for the dual-polarized slot array antenna.
  • The key features of the design are the slot length (L), slot width (W), and the slot separation (S) as shown in Fig.
  • 1. Since the substrate is relatively thick and there are no coupling lenses, it is very important to keep the slot separation distance such that not to excite grating lobes within the frequency band of interest.

Differential RF to DC Converting Circuit

  • It consists of bypass capacitors, matching networks, diode rectifier, a blocking low pass filter, and a DC storage capacitor.
  • The circuit receives differential RF signal from two slots of the antenna that are offset by 180 degrees from each other.
  • Critical issues of this circuit are the losses across the transmission lines, turn-on voltage of the diode, and the speed of the rectifier – all of which ultimately impact the sensitivity and conversion efficiency of the rectenna.
  • To minimize the transmission line losses, in their design as shown in Fig. 3, the authors used a combination of thick SiO2 dielectric and gold as conductor to make the transmission lines and the capacitors on the T-slot antenna substrate.
  • GaAs Schottky barrier diodes (SBD), such as the one in Fig. 3 , are most commonly used for rectenna rectifier circuits.

Power Management

  • Efficient wireless power transfer technology requires efficient power management approach which provides modular and scalability of the power transfer receiver design.
  • Additional functions specific to the power management section is “peak power tracking” (PPT) that guarantees the stability of the power systems.
  • This is because similar to solar arrays, at any given time, operating the wireless power receiver at power levels below the peak power will cause the collapse of the voltage across the rectenna array.
  • There are several options the authors are considering for realizing the power management section: (i) it can be developed using plain CMOS technology, (ii) could be combined with the high speed Schottky barrier diode and integrated using SiGe BiCMOS technology, or (iii) it can be combined with GaAs Schottky diode and integrated using GaAs fabrication processing.
  • While using the first option produces the least complex power system design, the second option provides us with the least complex path for wafer scale 3-D integration, which is the ultimate aim of this endeavor.

Discussions

  • The authors have designed and fabricated a novel T-Slot antenna coupled rectenna array at 94 GHz for demonstrating efficient wireless power transfer in this frequency band.
  • Assembly and testing of these devices are under progress now, and are showing great promise.

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Millimeter-Wave Wireless Power Transfer Technology for Space
Applications
Goutam Chattopadhyay, Harish Manohara, Mohammad Mojarradi, Tuan Vo, Hadi Mojarradi,
Sam Bae, Neville Marzwell
California Institute of Technology, USA
Introduction
Technologies enabling the development of compact systems for wireless transfer of power
through radio frequency waves (RF) continue to be important for future space based systems.
For example, for lunar surface operation, wireless power transfer technology enables rapid
on-demand transmission of power to loads (robotic systems, habitats, and others) and
eliminates the need for establishing a traditional power grid. A typical wireless power
receiver consists of an array of rectenna elements. Each rectenna element consists of an
antenna together with a high speed diode and a storage capacitor configured in a highly tuned
narrowband circuit for this purpose. The conversion of the microwave energy into DC in this
fashion is almost instantaneous. Using a high power rectenna array in concert with a fast
charging high performance battery can enable charging of the battery at very short time with
a large power burst and discharge of it at a lower rate for an extended operation time for
remote electronic assets.
Two main factors that determine the physical size of a rectenna based microwave power
conversion system are the frequency of the RF transmission and power capacity. At higher
frequencies, the size of the antenna elements in the array is small resulting in a smaller form
factor for the system. The smaller form factor of the higher frequency wireless power
receiver makes them more attractive for space systems; however, higher frequency systems
have to deal with (i) availability of high frequency power conversion components, (ii) higher
atmospheric loss, and (iii) overall efficiency in antenna arrays and the power conversion
network. Different groups have proposed feedhorn based imaging arrays at W-band [1].
Though feedhorns have excellent performance, their mass, size, and expense make them
unsuitable for large arrays.
In this paper we present a new compact, scalable, and low cost technology for efficient
receiving of power using RF waves at 94 GHz. This technology employs a highly innovative
array of slot antennas that is integrated on substrate composed of gold (Au), silicon (Si), and
silicon dioxide (SiO
2
) layers [2]. The length of the slots and spacing between them are
optimized for a highly efficient beam through a 3-D electromagnetic simulation process.
Antenna simulation results shows a good beam profile with very low side lobe levels and
better than 93% antenna efficiency. Moreover, in this design architecture, the slots can be
placed very close to each other enabling the integration of 20 X 20 slot array in an area that is
slightly larger than one square centimeter. The RF to DC conversion of the power is done
differentially by a very small network that is located adjacent to each individual slot. This
network consists of a coupling electrode, bypass capacitors, matching transmission line,
rectifier, a low pass filter, and a DC storage capacitor. This network is fabricated over the slot
array using additional layers SiO
2
and Au which act as the dielectric and metal layers for the
microstrip lines. Optimizing the losses for this network is achieved through iterative circuit
simulations which factors in the thickness of the layers. Simulation results suggest that this
technology is capable of realizing overall conversion efficiencies that are better than 72% and
energy densities as high as 1.2W per square centimeter. This power density is 30 times better
than high efficiency solar arrays with power density of 40 mW per square centimeter [3].
978-1-4244-2642-3/08/$25.00 ©2008 IEEE

Slot Antenna Array Design
A highly desirable solution to the efficient wireless power transfer would be to fabricate
monolithic array of antenna-coupled detectors on a planar substrate [4]. However, most
planar antenna designs produce broad beam patterns, and therefore require substrate lenses or
micro-machined horns for efficient coupling to the incoming beam [5]. This does not
preclude their use in large arrays; however, manufacturing and assembly of such arrays are
not straight forward. For this work we came up with a novel dual-polarization planar T-slot
antenna array which produces quite a narrow beam with no additional optical coupling
elements. The output from the antenna array is two thin-film microstrip lines, one for each
polarization, which can be efficiently coupled to Schottky diode detectors and associated
circuits to produce a single pixel in an wireless RF to DC power transfer focal plane array.
Fig. 1 shows the general concept for the dual-polarized slot array antenna. The antenna is
fabricated on a 550 um thick high dielectric silicon substrate (
r
= 11.8) which is illuminated
through substrate side to take advantage of the stronger antenna response on the dielectric
side [6]. We also used a quarter wave thick quartz anti-reflection coating on the silicon
substrate. The key features of the design are the slot length (L), slot width (W), and the slot
separation (S) as shown in Fig. 1. Since the substrate is relatively thick and there are no
coupling lenses, it is very important to keep the slot separation distance such that not to excite
grating lobes within the frequency band of interest. The antenna was designed and simulated
using Ansoft’s High Frequency Structure Simulator (HFSS) – a 3D electromagnetic solver.
The slots are used at their second resonance, and the impedance at the second resonance was
approximately 22 Ohm. Fig. 2 shows the radiation pattern and the E- and H-plane cuts for the
antenna pattern.
Differential RF to DC Converting Circuit
The differential RF to DC conversion circuit is shown in Fig. 3 (left). It consists of bypass
capacitors, matching networks, diode rectifier, a blocking low pass filter, and a DC storage
capacitor. The circuit receives differential RF signal from two slots of the antenna that are
offset by 180 degrees from each other. A rectenna element is defined as the combination of
this circuit and the pair of the slot antennas. The matched network enables conjugate
matching the antenna impedance to the diode impedance for the optimum power transfer. The
rectifier breaks the symmetry of the RF signal and the combination of the low pass filter and
DC capacitor collects the DC component of the RF voltage across the rectifier.
Critical issues of this circuit are the losses across the transmission lines, turn-on voltage of
the diode, and the speed of the rectifier – all of which ultimately impact the sensitivity and
conversion efficiency of the rectenna. To minimize the transmission line losses, in our design
as shown in Fig. 3, we used a combination of thick SiO
2
dielectric and gold as conductor to
make the transmission lines and the capacitors on the T-slot antenna substrate.
GaAs Schottky barrier diodes (SBD), such as the one in Fig. 3 (right), are most commonly
used for rectenna rectifier circuits. However zero barrier diodes with very low turn on voltage
have gained popularity as a new type of diodes that enable higher sensitivity and enhance
efficiency for the W-band rectenna circuits and terahertz imaging applications at the lower
end of the power spectrum [7]. At the same time Si Schottky barrier diodes are catching up
with the GaAs diodes in terms of speed and performance, at least in the 100 GHz frequency
range. There are two main advantages of using Si based SBD’s; (i) they are available as an
device element in many high speed SiGe BICMOS process technologies from various
foundries and (ii) they can be added to the rectenna through 3-D integration. Hence, same Si
technology used for integration of the rectifiers can also be easily used for integration of the

other housekeeping electronics for the wireless power transfer receiver including the power
distribution as discussed in the next section.
Power Management
Efficient wireless power transfer technology requires efficient power management approach
which provides modular and scalability of the power transfer receiver design. Power
management section regulates the output voltage of receiver tile. Additional functions
specific to the power management section is “peak power tracking” (PPT) that guarantees the
stability of the power systems. This is because similar to solar arrays, at any given time,
operating the wireless power receiver at power levels below the peak power will cause the
collapse of the voltage across the rectenna array. To prevent this, the PPT circuit constantly
measures the peak power of the rectenna (as a function of the RF input power) and allows the
rectenna array to only operate at power levels that are below or equal to its peak power
delivery capability.
There are several options we are considering for realizing the power management section: (i)
it can be developed using plain CMOS technology, (ii) could be combined with the high
speed Schottky barrier diode and integrated using SiGe BiCMOS technology, or (iii) it can be
combined with GaAs Schottky diode and integrated using GaAs fabrication processing.
While using the first option produces the least complex power system design, the second
option provides us with the least complex path for wafer scale 3-D integration, which is the
ultimate aim of this endeavor.
Discussions
We have designed and fabricated a novel T-Slot antenna coupled rectenna array at 94 GHz
for demonstrating efficient wireless power transfer in this frequency band. Assembly and
testing of these devices are under progress now, and are showing great promise.
References
[1] G. M. Rebeiz, D. P. Kasilingam, Y. Guo, P. A. Stimson, and D. B. Rutledge, “Monolithic Millimeter-Wave Two-
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[7] E. R. Brown, A. C. Young, J. Zimmerman, H. Kazemi, and A. C. Gossard, “Advances in Schottky Rectifier
Performance,” IEEE Microwave Magazine, pp. 54-59, June 2007.

Figures
Fig. 1: Schematic diagram of the slot antenna array showing the slots for one pixel. Slot length “L” and the distance “d” sets
the slot separation distance “S”. The cross-section of the pixel geometry is shown on top left. The figure in the middle shows
the mask layout, and the figure on right shows a photograph of the fabricated T-slot antenna array.
Fig. 2: Simulated E- and H-plane cut of the radiation pattern of the T-slot array antenna (left) and the 3-D radiation pattern of
the array (right).
Fig. 3: RF to DC differential conversion circuit where using a single diode and using appropriate level shifting circuit, higher
efficiency is achieved (left), and photograph of a GaAs Schottky diode fabricated at our laboratory at JPL (right). Similar
diode is being used for our circuit.
Citations
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Journal ArticleDOI
Xiao Lu1, Ping Wang2, Dusit Niyato2, Dong In Kim3  +1 moreInstitutions (4)
Abstract: Wireless charging is a technology of transmitting power through an air gap to electrical devices for the purpose of energy replenishment. The recent progress in wireless charging techniques and development of commercial products have provided a promising alternative way to address the energy bottleneck of conventionally portable battery-powered devices. However, the incorporation of wireless charging into the existing wireless communication systems also brings along a series of challenging issues with regard to implementation, scheduling, and power management. In this paper, we present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications. In particular, with regard to network applications, we review the static charger scheduling strategies, mobile charger dispatch strategies and wireless charger deployment strategies. Additionally, we discuss open issues and challenges in implementing wireless charging technologies. Finally, we envision some practical future network applications of wireless charging.

610 citations


Journal ArticleDOI
Abstract: Wireless power transfer (WPT) concept offers users the freedom from annoying wires, and allowing seamless powering and charging of portable devices in an unburdened mode. Since Nikola Tesla׳s early experiment, the WPT technology has observed the remarkable technological advancement on transmission methods which previously deemed unfeasible. This review paper outlines recent research activities on wireless power technology covering the history, the basic principle of magnetic resonant coupling, and early works on resonant coupled WPT. The two fundamental concepts of power transmission, the maximum power transfer and maximum energy efficiency principles, are summarized in terms of their energy efficiency and transmission distance capabilities. This paper also reviews the comparative study between coupled-mode theory (CMT) and reflected load theory (RLT) in case of analyzing the power transmission model of conventional 2-coil resonant coupled WPT with frequency splitting modes. The study shows that circuit-based RLT provides accurate results as CMT while predicting the average power transmission efficiency in steady-state analysis and is more convenient. This paper explains the effectiveness of advance 4-coil resonant coupled system adopting maximum power transfer principle in extending the operating range of WPT with better power transmission. Various efficiency enhancement techniques for resonant coupled WPT including system with multiple receivers are demonstrated in this paper. The review implies that the adaptive impedance matching using LC circuits is more prolific in practical terms to improve the efficiency of coupled coils. Moreover, the benefits of resonant coupled WPT, its implementation in both consumer and non-consumer applications, and the commercial journey of WPT along with the safety consideration to human exposure issues are also addressed in this paper.

158 citations


Journal ArticleDOI
Huy Hoang1, Seunggyu Lee1, Young-Su Kim1, Yunho Choi1  +1 moreInstitutions (1)
05 Jul 2012
TL;DR: An adaptive technique to enhance the efficiency of magnetic resonance based wireless power transfer system for future portable consumer electronics is presented and it is found that the technique is also effective in case of multiple receiving coils.
Abstract: This paper presents an adaptive technique to enhance the efficiency of magnetic resonance based wireless power transfer system for future portable consumer electronics. In order to transfer energy to mobile devices, asymmetric coupling resonators with larger sizes of coils in a transmitter than those in a receiver are exploited. By changing a coupling coefficient between coils only in the transmitting side, the system performance increases significantly. An experiment setup has been developed, and the S21 parameter has been measured showing 3.3 dB improvement of system using the adaptive technique at a distance of 65 cm. An important finding is that the technique is also effective in case of multiple receiving coils. The measured performance was improved by roughly 1 dB with the use of the adaptive technique.

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Journal ArticleDOI
Alessandra Costanzo1, Diego Masotti1Institutions (1)
TL;DR: This work envisions the future world as an Internet of Things/Internet of Everything in terms of both a consumer IoT/IoE and the Industrial IoT (interconnectedness to improve business-to-business services, mainly through machineto-machine interactions).
Abstract: We are surrounded in our daily lives by a multitude of small, relatively inexpensive computing devices, many equipped with communication and sensing features. From these has evolved the concept of "pervasive intelligence" [1], [2], a basis from we can envision our future world as an Internet of Things/Internet of Everything (IoT/IoE), in terms of both a consumer IoT/IoE (interconnected devices within an individual's environment) and the Industrial IoT (interconnectedness to improve business-to-business services, mainly through machineto-machine interactions) [3].

63 citations


Cites background from "Millimeter-wave wireless power tran..."

  • ...May 2017 127 massive arrays at high frequencies (>30 GHz); otherwise, the dimension of the radiating structure becomes incompatible with the application....

    [...]

  • ...Wireless Powering Figures of Merit Wireless delivery of power can adopt two radically different mechanisms: • exploiting far-field RF sources for so-called far-field WPT (FF-WPT), where the involved frequencies are in the microwave (300 MHz–30 GHz) [20], [21] or millimeter-wave (30–300 GHz) [22], [23] ranges • exploiting the near (or reactive) field provided by closely located sources in the low-frequency (LF; 30–300 kHz) [24] or high-frequency (HF; 3–30 MHz) [25] ranges for so-called near-field WPT (NF-WPT)....

    [...]

  • ...A further step forward is provided in [8], [55], where an original radiating subsystem, consisting of a single-port antenna on paper substrate, is able to both communicate and scavenge energy by resorting to the European low UWB band (3.1– 4.8 GHz) and the low UHF band (868 MHz), res pectively....

    [...]

  • ...Wireless delivery of power can adopt two radically different mechanisms: • exploiting far-field RF sources for so-called far-field WPT (FF-WPT), where the involved frequencies are in the microwave (300 MHz–30 GHz) [20], [21] or millimeter-wave (30–300 GHz) [22], [23] ranges • exploiting the near (or reactive) field provided by closely located sources in the low-frequency (LF; 30–300 kHz) [24] or high-frequency (HF; 3–30 MHz) [25] ranges for so-called near-field WPT (NF-WPT)....

    [...]

  • ...In Figure 11(a), a slotted UHF dipole (operating at 868 MHz) is obtained from the ground plane of the UWB monopole [52]; in Figure 11(b), the UWB antenna and UHF monopole (operating at 2.4 GHz) share the same substrate layer [53]....

    [...]


Journal ArticleDOI
Xiao Lu1, Ping Wang2, Dusit Niyato2, Dong In Kim3  +1 moreInstitutions (4)
TL;DR: This paper presents a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications, and discusses open issues and challenges in implementing wireless charging technologies.
Abstract: Wireless charging is a technology of transmitting power through an air gap to electrical devices for the purpose of energy replenishment. The recent progress in wireless charging techniques and development of commercial products have provided a promising alternative way to address the energy bottleneck of conventionally portable battery-powered devices. However, the incorporation of wireless charging into the existing wireless communication systems also brings along a series of challenging issues with regard to implementation, scheduling, and power management. In this article, we present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications. In particular, with regard to network applications, we review the mobile charger dispatch strategies, static charger scheduling strategies and wireless charger deployment strategies. Additionally, we discuss open issues and challenges in implementing wireless charging technologies. Finally, we envision some practical future network applications of wireless charging.

40 citations


Cites background from "Millimeter-wave wireless power tran..."

  • ...Moreover, frequency is a key factor that affects the physical size of a rectenna based microwave power conversion system [354]....

    [...]


References
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399 citations


"Millimeter-wave wireless power tran..." refers background in this paper

  • ...However, most planar antenna designs produce broad beam patterns, and therefore require substrate lenses or micro-machined horns for efficient coupling to the incoming beam [5]....

    [...]


Journal ArticleDOI
Gabriel M. Rebeiz1, Dayalan P. Kasilingam1, Yong Guo1, P.A. Stimson1  +1 moreInstitutions (1)
Abstract: A monolithic two-dimensional horn imaging array has been fabricated for millimeter wavelengths. In this configuration, a dipole is suspended in an etched pyramidal cavity on a 1- mu m silicon-oxynitride membrane. This approach leaves room for low-frequency connections and processing electronics. The theoretical pattern is calculated by approximating the horn structure by a cascade of rectangular-waveguide sections. The boundary conditions are matched at each of the waveguide sections and at the aperture of the horn. Patterns at 93 and 242 GHz agree well with theory. Horn aperture efficiencies of 44+or-4%, including mismatch and resistive losses, have been measured. A detailed breakdown of the losses is presented. The coupling efficiency to various f-number imaging systems is investigated, and a coupling efficiency of 24% for an f0.7 imaging system (including spillover, taper, mismatch and resistive losses) has been measured. Possible application areas include imaging arrays for remote sensing, plasma diagnostics, radiometry and superconducting tunnel-junction receivers for radio astronomy. >

149 citations


"Millimeter-wave wireless power tran..." refers background in this paper

  • ...However zero barrier diodes with very low turn on voltage have gained popularity as a new type of diodes that enable higher sensitivity and enhance efficiency for the W-band rectenna circuits and terahertz imaging applications at the lower end of the power spectrum [7]....

    [...]

  • ...Different groups have proposed feedhorn based imaging arrays at W-band [1]....

    [...]


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15 Sep 2000
Abstract: This paper describes a trade study between state-of-the-art, commercially-available very high-efficiency III-V multi-junction solar cells and advanced high-efficiency silicon cells at the bare cell and panel levels. The solar cell technologies in this comparison will be high-efficiency rad-hard 3-mil Si, dual-junction InGaP/GaAs (on Ge), and triple-junction InGaP/GaAs/Ge, with the beginning-of-life (BOL) efficiencies of 17%, 23%, and 26%, respectively. Two different 'typical orbits are considered: geosyncronous (GEO) and low-Earth (LEO) orbits. It is assumed that the end-of-life (EOL) conditions for GEO and LEO are equivalent to degradation due to 1-MeV electrons at 5E14 and 1E15 e/cm/sup 2/, respectively. Parameters critical to conventional rigid solar arrays such as specific power/mass (W/Kg), specific mass/area (Kg/m/sup 2/), specific power/area (W/m/sup 2/), and normalized end-of-life (EOL) $/W are compared for these cell technologies.

60 citations


"Millimeter-wave wireless power tran..." refers background in this paper

  • ...This power density is 30 times better than high efficiency solar arrays with power density of 40 mW per square centimeter [3]....

    [...]


Journal ArticleDOI
Elliott R. Brown1, Adam Young1, Jeramy D. Zimmerman1, H. Kazemi  +1 moreInstitutions (1)
Abstract: In conclusion, heteroepitaxial technology has delivered a new device building block for the microwave and millimeter-wave toolbox - a single-crystal Schottky barrier diode made from a lattice matched combination of a semimetal (ErAs) and a semiconductor (InAlGaAs). This article has demonstrated how sensitive such a Schottky diode can be as a room-temperature zero-bias rectifier up to W band and addressed the fundamental device and impedance matching issues when coupled to a planar antenna in a quasi-optical package. As might be expected, the new Schottky diodes also display a very low degree of 1/f noise when used in applications that require bias or large signals, such as frequency mixers and multipliers (Young et al., 2006)

34 citations


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  • ...However zero barrier diodes with very low turn on voltage have gained popularity as a new type of diodes that enable higher sensitivity and enhance efficiency for the W-band rectenna circuits and terahertz imaging applications at the lower end of the power spectrum [ 7 ]....

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Proceedings ArticleDOI
08 Mar 2002
Abstract: We present a design for a multipixel, multiband (100 GHz, 200 GHz and 400 GHz) submillimeter instrument: SAMBA (Superconducting Antenna-coupled, Multi-frequency, Bolometric Array). SAMBA uses slot antenna coupled bolometers and microstrip filters. The concept allows for a much more compact, multiband imager compared to a comparable feedhorn-coupled bolometric system. SAMBA incorporates an array of slot antennas, superconducting transmission lines, a wide band multiplexer and superconducting transition edge bolometers. The transition-edge film measures the millimeter-wave power deposited in the resistor that terminates the transmission line.

21 citations


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  • ...A highly desirable solution to the efficient wireless power transfer would be to fabricate monolithic array of antenna-coupled detectors on a planar substrate [4]....

    [...]