T. Hirvonen

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 dielectrics at 100 GHz with an open resonator connected to a network analyzer

A high-Q hemispherical open resonator is connected to an automatic network analyzer to enable precise and fast determination of the permittivity and loss tangent of low-loss dielectric materials at 100 GHz. Both scalar theory and vector theory with a frequency variation method are used to determine the dielectric properties of low-loss materials which are used in quasioptical components, for example in fusion reactor windows and tenses for millimeter-wave receivers. The uncertainty of the measurement is 0.02% to 0.04% for /spl epsi//sub r/(/spl epsiv//sub r//spl ges/2) and 6-40/spl times/10/sup -6/ for tan /spl delta/(10/sup -4//spl les/tan /spl delta//spl les/10/sup -3/).

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.

Numerical modeling of a nonuniform grating with FDTD

The need for a numerical analysis of a nonuniform grating arises from antenna testing facilities. A hologram type of compact antenna test range (CATR) is a recently proposed method for antenna testing at millimeter wavelengths. Simulations of the quiet-zone field are done with a two-dimensional finite-difference–time domain method (FDTD), combined with an exact near-field aperture integration method [physical optics (PO)].

Lens-Type Compact Antenna Test Range at MM-Waves

A lens-type compact antenna test range (CATR) has been studied both theoretically and experimentally. For a lens with low dielectric constant ¿r, the surface accuracy requirement is much less stringent than for a reflector. An experimental CATR with a shaped polyethylene (¿r, = 2.32) lens was made at 110 GHz. In order to make the amplitude ripple in the quiet zone small, the use of saw tooth serrations around the lens was studied. Theoretically the quiet zone field is exellent (peak to peak ripple 0.27 dB). Preliminary measured values are promising (peak to peak ripple 2.0 dB).

Measurement of a Novel 40 GHz Planar Antenna using Planar Near-field Scanning Techniques and a Hologram CATR

Planar near-field scanning and a hologram type of compact antenna test range (CATR) are used to determine the radiation characteristics of a novel 40 GHz planar antenna. The results are compared with those obtained from a far-field measurement. The near-field scanning method works very well, and as a result, a complete three dimensional radiation pattern is obtained as well as the aperture distribution of the antenna under test (AUT). The same antenna was also measured with a hologram CATR. Despite the fact that the used hologram CATR had a design error making the quiet-zone too small, it was demonstrated that the hologram CATR method is feasible at long millimeter wavelengths.

Performance analysis of a submillimeter wave hologram CATR

A hologram is a planar, transmission type of collimating component. Performance of a submillimeter wave hologram type of compact antenna test range (CATR) is studied with a combined analysis of a physical optics (PO) and a finite difference time domain (FDTD) method at 500 GHz. Main focus is on the fabrication errors, the feed positioning errors, and the frequency and polarization dependence of the hologram structure. The effect of planarity errors is discussed.

Optimization of a submillimeter wave hologram CATR

The optimization of a submillimeter wave hologram type of compact antenna test range (CATR) is studied with a combined analysis of an exact near-field aperture integration (physical optics) and a finite difference time domain (FDTD) method at 500 GHz. The effect of altering the feed horn radiation pattern is discussed.

Hologram as the collimating element in a compact antenna test range at millimeter wavelengths

A compact antenna test range (CATR) has a great potential for testing electrically large antennas. However, the application of conventional reflector type CATRs becomes increasingly difficult, though not impossible, above 100 GHz due to the tight surface accuracy requirements for the reflectors. A CATR based on a planar hologram has been studied to overcome the problems incurred by the use of reflectors with insufficient surface accuracy. This paper summarizes the recent results obtained for a hologram CATR at Helsinki University of Technology.

Development of a test method for the Odin satellite 1.1 m antenna at 119 and 500 GHz

An idea of a hologram compact antenna test range (CATR) at millimeter wavelengths was introduced in 1992. Now this method is being developed towards a CATR which is planned to be used to test the 1.1 m antenna of the Odin satellite at 119 and 500 GHz. The feasibility of the method has been demonstrated at 119 GHz with a hologram of 0.55 m in diameter: a quiet zone with an amplitude and phase ripple of less than 1 dB and 10/spl deg/, respectively, has been achieved.