Silicon Substrate Lens Research Articles

A Self-adapting Pixel Antenna - Substrate Lens System for Infrared Frequencies

In this work, we propose a concentrator lens - antenna arrangement, potentially suitable for infrared sensing and energy harvesting rectenna systems. The structure consists of a pixel antenna, self-adapting for the direction of the incident infrared radiation, and a concentrator lens, both optimized for the mid-infrared spectrum. The silicon substrate lens is situated above the pixel antenna, enabling the concentration of the incident light on the antenna; silicon was chosen due to its transparency in the IR spectrum. We examine how various parameters of the lens, in conjunction with the different states of the pixel antenna, affects the performance of the system. The simulations show that the gain of the arrangement increases considerably in correlation with the radius of the lens. The results suggest that the energy conversion efficiency of infrared rectenna systems can be enhanced by several orders of magnitude with the utilization of the proposed arrangement.

A High-Sensitivity AlGaN/GaN HEMT Terahertz Detector With Integrated Broadband Bow-Tie Antenna

Many emerging applications in the terahertz (THz) frequency range demand highly sensitive, broadband detectors for room-temperature operation. Field-effect transistors with integrated antennas for THz detection (TeraFETs) have proven to meet these requirements, at the same time offering great potential for scalability, high-speed operation, and functional integrability. In this contribution, we report on an optimized field-effect transistor with integrated broadband bow-tie antenna for THz detection (bow-tie TeraFET) and compare the detector's performance to other state-of-the-art broadband THz detector technologies. Implemented in a recently developed AlGaN/GaN MMIC process, the presented TeraFET shows a more than twice performance improvement compared to previously fabricated AlGaN/GaN-HEMT-based TeraFETs. The detector design is the result of detailed modeling of the plasma-wave-based detection principle embedded in a full-device detector model to account for power coupling of the THz radiation to the intrinsic gated FET channel. The model considers parasitic circuit elements as well as the high-frequency impedance of the integrated broadband antenna, and also includes optical losses from a silicon substrate lens. Calibrated characterization measurements have been performed at room temperature between 490 and 645 GHz, where we find values of the optical (total beam power referenced) noise-equivalent power of 25 and ${\text{31 pW}}/\surd{\text{Hz}}$ at 504 and 600 GHz, respectively, in good agreement with simulation results. We then show the broadband detection capability of our AlGaN/GaN detectors in the range from 0.2 to 1.2 THz and compare the TeraFETs’ signal-to-noise ratio to that of a Golay cell and a photomixer. Finally, we demonstrate an imaging application in reflection geometry at 504 GHz and determine a dynamic range of >40 dB.

THz-TDS using a photoconductive free-space linear tapered slot antenna transmitter.

A near-field edge-coupled photoconductive free-space linear tapered slot antenna has been constructed as a planar alternative to the standard photoconductive switch coupled to a silicon substrate lens. The temporal response along the optical axis is investigated to ensure the structure itself does not introduce pulse distortion which would fundamentally limit the usefulness of the structure. Experimental results show that a 1.6 THz bandwidth with a ≈50dB dynamic range is achievable with the new structure which is comparable to our reference experiment with a standard silicon substrate lens. The investigated structure has the added benefit of a potential substantial physical size reduction and can also be used to excite waveguides in the near-field.

A 15–50-GHz Quasi-Optical Scalar Network Analyzer Scalable to Terahertz Frequencies

A 15-50-GHz two-port quasi-optical scalar network analyzer consisting of a transmitter and receiver built in a planar technology is presented. The network analyzer is based on a Schottky-diode multiplier and mixer integrated inside a planar antenna and fed differentially by a coplanar waveguide transmission line. The antenna is placed on an extended hemispherical high-resistivity silicon substrate lens. The local oscillator signal is swept from 3 to 5 GHz and high-order harmonic mixing in both the up- and down-conversion mode is used to realize the RF bandwidth. The network analyzer has a dynamic range of >;50 dB in a 1-kHz bandwidth, and was successfully used to measure frequency-selective surfaces with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =20, 30, and 40 GHz and a second-order bandpass response. Furthermore, the system was built with circuits and components for easy scaling to millimeter-wave frequencies, which is the primary motivation for this work.

Fabrication and Characterization of Quasi-Optical Terahertz Nanorectifiers with Integrated Antennas

We are developing microelectronic terahertz rectifiers by scaling down the dimensions of GaAs Schottky diodes and field-effect transistors to the sub-micron range, and by investigating the effect of on-chip parasitic capacitances on the square-law power detection signal. For broadband operation at THz frequencies the terahertz oscillating signal is fed to the device by integrated lithographic planar antennas, suitably coupled to a silicon substrate lens. Such room-temperature THz detectors can be fabricated in arrays and naturally provide picosecond response time, suitable for detection of coherent THz radiation produced by single electron bunches in accelerators.

Terahertz Direct Detection in ${\hbox{YBa}}_{2}{\hbox{Cu}}_{3}{\hbox{O}}_{7}$ Microbolometers

A high sensitivity broadband terahertz direct detector based on YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> high-Tc superconductor microbolometers is presented. At 77 K, the responsivity of the spiral antenna-integrated microbolometers (1.5 μm ×1.5 μm) is 190 V/W, referenced to the input of the silicon substrate lens, across the frequency range of 330 GHz-1.63 THz in a single device. The response time is approximately 300 ps. Using a room temperature readout, we measure an optical noise equivalent power (NEP) of 20 pW/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sup> (readout noise limited) for modulation frequencies ranging from 500 Hz to 100 kHz.

A 220 GHz Single-Chip Receiver MMIC With Integrated Antenna

This letter presents the design and characterization of a 220 GHz microstrip single-chip receiver monolithic microwave integrated circuit (MMIC) with an integrated antenna in a 0.1 mum GaAs metamorphic high electron mobility transistor technology. The receiver MMIC consists of a novel slot-square substrate lens feed antenna, a three-stage low noise amplifier, and a sub-harmonically pumped resistive mixer. The receiver MMIC is mounted on a 12 mm silicon substrate lens which focuses the radiation from the calibration loads to the on-chip antenna through an opening in the backside metallization of the MMIC. The double sideband noise figure of this quasioptical receiver is as low as 8.4 dB (1750 K) at 220 GHz including the losses in the antenna and in the lens. To the best of the authors' knowledge, this work demonstrates the highest integration level versus operating frequency for a MMIC ever published, regardless of technology.

A V-band quasi-optical GaAs HEMT monolithic integrated antenna and receiver front end

A single-chip monolithic integrated V-band folded-slot antenna with two Schottky-barrier diodes and a local oscillator source is developed as a quasi-optical receiver for the first time. The monolithic microwave integrated circuit consists of a voltage-controlled oscillator (VCO), a coplanar waveguide (CPW)-to-slotline transition, a low-pass filter, a folded-slot antenna, and a 180/spl deg/ single balanced mixer. The chip is fabricated based on the 0.15-/spl mu/m GaAs high electron-mobility transistor technology and the overall chip size is 3/spl times/1.5 mm/sup 2/. A finite-difference time-domain method solver is also developed for analyzing the embedded impedance characteristics of the folded-slot antenna to design the mixer. The chip is placed on an extended hemispherical silicon substrate lens to be a quasi-optical receiver. The performance of the receiver is verified by experimental measurements. The VCO has achieved a tuning range from 61.9 to 62.5 GHz and approximately 9.3-dBm output power. The CPW-to-slotline transition has bandwidth from 50 to 70 GHz. The mixer results in 15-dB single-sideband conversion loss and the receiving patterns of the IF power are also measured.

A 140-170-GHz low-noise uniplanar subharmonic Schottky receiver

A 150-GHz Schottky diode subharmonic receiver based on a coplanar-waveguide-fed double-folded-slot (DFS) antenna is presented in this paper. The DFS antenna is placed on an extended hemispherical high-resistivity silicon substrate lens to achieve a high directivity and a high coupling to a Gaussian beam efficiency. The uniplanar receiver results in a 12/spl plusmn/0.5-dB measured double-sideband conversion loss at 144-152 GHz for a 8-10 mW local-oscillator power at 77 GHz, and has a wide-hand /spl les/13-dB conversion loss over 30 GHz of bandwidth (140-170 GHz). The measured conversion loss includes silicon lens absorption and reflection losses, as well as IF mismatch losses. The applications are in new small aperture (7.5-cm lenses) collision-avoidance radars at 150 GHz.

A uniplanar 90-GHz Schottky-diode millimeter-wave receiver

A 90 GHz Schottky-diode receiver based on a double slot antenna fed by a coplanar-waveguide (CPW) transmission line is presented. The double slot antenna is placed on an extended hemispherical high-resistivity silicon substrate lens. The uniplanar receiver results in a 9.3/spl plusmn/0.3 dB measured SSB conversion loss at 88-90 GHz including antenna and IF circuit losses and a 1-dB loss due to the use of a nonoptimal matching cap layer at the silicon lens-air interface. The calculated conversion loss agrees very well with the RF measurements. The uniplanar double-slot antenna receiver is very small, less than 1.1/spl times/4 mm including the RF/IF filter, and is compatible with monolithic two- and three-terminal devices on GaAs substrates. The application areas are in millimeter-wave receivers for automotive systems, communication systems, and radiometric linear imaging arrays.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A monolithic 250 GHz Schottky-diode receiver

A 250 GHz monolithic Schottky-diode receiver based on a double-slot antenna is presented. The double-slot antenna is placed on an extended hemispherical high-resistivity silicon substrate lens. The measured DSB conversion loss and noise temperature at 258 GHz are 7.8/spl plusmn/0.3 dB and 1600/spl plusmn/100K for the antenna-mixer, respectively. A nonoptimal polyethylene /spl lambda//sub d//4 matching-cap layer for the silicon lens improves the conversion loss and noise temperature by 1 dB, and another 0.7 dB improvement could be obtained with the use of a more optimal matching cap layer. The uniplanar double-slot antenna receiver is less than 0.3/spl times/1 mm in size including the IF filter and represents the first fully monolithic 250 GHz receiver to date. The measured performance is within 2-3 dB of the best 200/sup +/ GHz waveguide receivers using planar Schottky diodes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>