A. Lehto

The Odin satellite - I. Radiometer design and test

The Sub-millimetre and Millimetre Radiometer (SMR) is the main instrument on the Swedish, Canadian, Finnish and French spacecraft Odin. It consists of a 1.1 metre diameter telescope with four tuneable heterodyne receivers covering the ranges 486-504 GHz and 541-581 GHz, and one fixed at 118.75 GHz together with backends that provide spectral resolution from 150 kHz to 1 MHz. This Letter describes the Odin radiometer, its operation and performance with the data processing and calibration described in Paper II.

Measurement of the Odin telescope at 119 GHz with a hologram-type CATR

Development work of a 119 GHz compact antenna test range (CATR), based on a 2.4 m/spl times/2.0 m hologram and its application on the Odin telescope tests are described. The hologram element comprises seven parts, which are fabricated using silk-screen printing techniques. Comparison between the theoretical and the measured quiet-zone fields of the hologram CATR is made, which demonstrates the correctness of the analysis method and also the importance of high quality physical joints between the hologram parts. The CATR has been successfully used in the measurement of a 1.1-m offset reflector antenna onboard the Odin spacecraft. The measured and calculated antenna radiation patterns are in good agreement in the main beam region. The effects of the imperfections in the quiet-zone field and in the aperture field of the antenna on the measurement results are simulated.

A high-gain 58-GHz box-horn array antenna with suppressed grating lobes

A low-profile high-gain antenna array of box horns for the frequency band 57.2-58.2 GHz is presented. The antenna consists of 256 radiating elements divided into two subgroups of 128 elements fed by a rectangular waveguide feed network. The radiating elements are fed in parallel and the waveguides are connected with T-junctions. The matching of the T-junctions is improved with a matching pin and a splitter. Because of the waveguide feed network, the element spacing is larger than one wavelength, which causes grating lobes. The grating lobes and sidelobes in the H-plane have been suppressed by the use of a combination of subarrays, a special characteristic of the box horn, and an array amplitude tapering. The measured sidelobe levels in the H-plane are below -30 dB at angles larger than 8/spl deg/ from boresight. A gain higher than 35.7 dBi and a return loss higher than 14.4 dB have been measured for the antenna over the band 57.2-58.2 GHz.

A large planar 39-GHz antenna array of waveguide-fed horns

A planar antenna in which box horns are used as radiating elements is described. The feed network is built by connecting rectangular waveguides with T-junctions. The matching of the T-junctions is improved by using rounded splitters and matching pins in the junctions. The radiating element has been designed to cancel out the grating lobe. The grating lobe is due to an element spacing larger than one wavelength. The highest sidelobes are at least 31 dB below the main beam in the H-plane and 16 dB in the E-plane. A gain of 37 dBi has been achieved at 39.2 GHz. These results demonstrate the feasibility of this antenna for applications requiring high gain at millimeter wavelengths.

Simple broadband dual-polarized aperture-coupled microstrip antenna

This paper presents a simple broadband dual-polarized microstrip antenna with only three layers. The input impedance bandwidth (VSWR<2) of 25% is achieved with the double resonance technique, in which the resonant frequencies of the patch and the coupling slot are tuned near to each other. Proper positioning of the coupling slots and the use of a thin, medium permittivity substrate results in high isolation (>40 dB) between the ports and thus acceptable cross polarization (better than -20 dB). The geometry, return loss, and the isolation of a single antenna element and the radiation pattern of a four-element linear array are presented. These antennas were designed for the European DBS-band 10.70-12.75 GHz.

A new method for correcting phase errors caused by flexing of cables in antenna measurements

A simple method for correcting phase errors due to flexing of cables in an antenna measurement setup is introduced. The method that makes it possible to measure the phase error in the cable is described, and the error is removed numerically from the antenna measurement results. The method has been verified with experimental measurements at 10 GHz. The measurements show that the accuracy of the phase correction is limited by the accuracy of the phase measurement device in the system. >

Accurate millimeter wave antenna phase pattern measurements using the differential phase method with three power meters

The novel differential phase measurement method has been demonstrated at millimeter waves using three power meters instead of a phase-sensitive measurement device. Compared to conventional antenna phase measurement methods, the differential phase method provides several advantages. This method requires no rotary joints or flexible cables. Phase-locking of the oscillators is not necessary. It is shown that the phase measurement device can be replaced by three power dividers and three power meters or detectors. The phase patterns measured with three power meters agree well with the measurements carried out using an antenna measurement receiver as well as with the theory. >

Matching of a rectangular waveguide T junction with unequal power division

Matching of a rectangular waveguide T junction with two matching posts and a splitter is proposed. An unequal power division is realized without a phase difference between the output ports. A return loss more than 30 dB over the frequency range 37.0–39.5 GHz can be achieved according to simulations. Measurements show a return loss larger than 18 dB.

A 38 GHz Horn Antenna Array

A planar antenna array of box horns for the frequency range 37.0-39.5 GHz was designed and tested. Low sidelobes in the H-plane have been realized by combining two box horn arrays shifted sideways. The radiating elements are fed in parallel through a waveguide feed network, where improved T-junctions are used as power dividers. A 64-element antenna array has been built. According to the measurements, a sidelobe level of ¿35 dB in the H-plane at an angle of 36° from the main beam, a gain of 30.4 dBi, and a return loss higher than 16.9 dB have been achieved over the band 37.0-39.5 GHz.

Embedding impedance of a millimeter wave Schottky mixer: Scaled model measurements and computer simulations

Using scaled model measurements at 2.5–12 GHz the embedding network of a 3 mm Schottky diode mixer has been developed. The noise performance of a cryogenic millimeter wave receiver was simulated by computer applying the developed equivalent circuit and diode parameters. The effects of impedance match at the fundamental frequency as well as at harmonic frequencies were studied. Also the effect of diode I-V-curve steepness was studied. The calculated results were compared with the experimental noise performance.