Double-folded Slot Research Articles

Spectral Characteristics of the Double-Folded Slot Antennas with Cold-Electron Bolometers for the 220/240 GHz Channels of the LSPE Instrument

We present the results of the experimental and theoretical study of the resonant properties and noise of a single cell of a receiving system based on cold-electron bolometers (CEB) with a double-folded slot antenna and coplanar lines. The system was designed to receive signals at 220/240 GHz frequencies with a 5% bandwidth. In measurements, we used the samples of the double-folded slot antennas with slot lengths of 162 um and coplanar line lengths from 185 to 360 um. Measurements of the resonance properties of CEB located at 0.3 K cryostat plate were carried out using a generator based on a high-temperature YBCO Josephson junction located inside the same cryostat at 4 K plate. This arrangement made it possible to obtain smooth amplitude-frequency characteristics with a clearly defined peak of a 15–21 GHz bandwidth at different frequencies. Based on these results, 2-D array of double-folded slot antennas with CEBs as 220/240 GHz LSPE channel prototype was calculated.The absorption efficiency of the array has reached 81% and 77% for 220 and 240 GHz channels, respectively.

Impedance bandwidth improvement for microstrip-fed slot antennas using short-circuited termination

In this paper, the impedance bandwidth of microstrip-fed slot antennas is improved by using short-circuited termination as compared to open-circuited termination. The bandwidth improvements for simple slot, single-folded slot, and double-folded slot antennas, respectively, are demonstrated. The 10-dB return loss bandwidth of 29% is attained for the double-folded slot antenna fed by a short-circuited microstrip line. The measured far-field patterns are stable across the passband, which makes it a good candidate for UWB application. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 67–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20726

Experimental characterisation of 38 GHz micromachined GaAs receiver

The experimental characterisation of a 38 GHz micromachined GaAs receiver is presented. The structure monolithically integrates a double-folded slot antenna and a Schottky diode on the same GaAs thin membrane. The measurements demonstrate that this approach has the potential for innovative circuit architecture development.

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 90-100 GHz double-folded slot antenna

A double-folded slot antenna (DFS) has been designed, fabricated, and tested at 90-100 GHz. The antenna shows a very wideband impedance around 20 /spl Omega/ from 85 to 110 GHz. The low impedance is compatible with superconductor-insulator-superconductor (SIS) junctions, Schottky diodes or high electron mobility transistor (HEMT) amplifiers, which require a low impedance at millimeter wave frequencies. The antenna is placed on a dielectric lens to synthesize a semi-infinite substrate and realize high-directivity patterns. The measured radiation patterns agree very well with theoretical calculations and demonstrate symmetric main beams and sidelobe levels below -15 db over a 10% bandwidth. The double folded slot antenna is an attractive candidate for low-cost wideband millimeter-wave monolithic microwave integrated circuits (MMIC) front ends.

Single and double folded-slot antennas on semi-infinite substrates

Design guidelines are presented for single and double folded-slot (DFS) antennas on a dielectric half-space. The DFS antenna consists of two folded-slot elements which are separated by a half-wavelength and are fed from one side using a coplanar waveguide transmission line. A space-domain integral equation technique, based on the free-space Green's function, has been used to compute the resonant circumference and self- and mutual impedances of single folded-slots on various substrates. In addition, the input impedance and radiation patterns of DFS designs are included. Specific examples are shown for air, quartz, and silicon substrates, and measured data for DFS antennas on air and silicon substrates is provided to validate the calculated results.