Joakim Johansson

The diagonal horn as a sub-millimeter wave antenna

The far-field radiation pattern of a diagonal horn has been calculated by aperture integration. The radiation patterns for a 4*4 diagonal horn array, measured at 100 GHz, agree very well with theoretical predictions. The aperture electric field was also expanded into Gauss-Hermite modes. The results indicate that the fraction of the power radiated into the fundamental Gaussian mode is about 84%. About 10% of the power is radiated in the cross-polarized component. >

Tapered slotline antennas at 802 GHz

Broken linearly tapered endfire slotline antennas (BLTSAs) were fabricated on 1.7- mu m thin SiO/sub 2/-Si/sub 3/N/sub 4/ dielectric membranes. Antenna patterns in the E-, H-, and D-planes were measured at 802 GHz. The -10 dB beamwidths were found to be approximately 40 degrees in all planes, with side lobe levels below -11 dB (-19 dB in the E-plane). The cross-polarized peaks in the D-plane were 8 dB below the copolarized peak. A theoretical model for calculating the E- and H-plane patterns of tapered slotline antenna 10 is extended to include the co- and cross-polarized D-planes. Measured and calculated patterns show good agreement. >

Slotline Antennas for Millimeter and Submillimeter Wavelengths

Two types of tapered slotline antennas (TSA) have been studied. One type, which requires a fairly thin substrate, gives a radiation pattern of high gaussicity. For submillimeter wave-lengths, where the substrate is difficult to thin down, a sandwich type with thick substrate and superstrate has been studied. The radiation patterns for the sandwiched antenna are substantially improved when an elliptical lens is added.

Optically controlled spatial modulation of (sub-)millimeter waves using nipi-doped semiconductors

The use of a molecular beam epitaxy engineered InGaAs/GaAs semiconductor structure to quasioptically modulate a millimeter wave Gaussian beam using an optical control signal has been demonstrated. The RF transmission is modulated spatially by the optically generated excess carrier density. Low optical intensities are sufficient due to the long recombination lifetime achieved in the nipi-doped structure used. A modulation depth of more than 15 dB in transmission mode has been obtained at 100 GHz. Modulation has been measured up to 5 THz using a Fourier transform spectrometer. >

Computer generated phase holograms (kinoforms) for millimeter and submillimeter wavelengths

Computer generated Fourier transform phase holograms, known as kinoforms, have been synthesized, manufactured and their performance evaluated at a wavelength of 3 mm (100 GHz). The kinoforms were synthesized to give a prescribed far-field intensity distribution and manufactured by milling the computed kinoform surface relief into a Teflon plate, using a numerically controlled milling machine. The measured diffraction efficiencies exceed 50 percent. Millimeter-wave kinoforms can be used in various quasi-optical applications,e.g. distributing a local oscillator signal to an array of detector elements in heterodyne receivers.

Slot Line Components for Millimeter Wave and Sub-Millimeter Wave Integrated Circuits

Measurements of radiation losses from a few slot line components on high-epsilon (around 11) materials are presented, including short circuits, open circuits, and lambda-quarter filters. Also covered are losses via surface modes, and tapered slot antenna radiation patterns. Measured wavelengths are given for slot lines on substrates of dielectric constants 10.5 and 11. A wideband slot line to microstrip transition is presented.

Integrated Slot Line Antenna with SIS Mixer for Focal Plane Imaging Applications

Recently, the possibility of constructing millimeter wave imaging array receivers for use in radio astronomy has excited much interest, In this paper, we present results obtained to date in efforts to design a prototype imaging receiver for operation at 100 GHz.