Logarithmic Spiral Antenna Research Articles

A broad-band low-noise SIS receiver for submillimeter astronomy

A quasi-optical heterodyne receiver using a Pb-alloy superconductor-insulator-superconductor (SIS) tunnel junction as the detector and a planar logarithmic spiral antenna for the RF coupling is described, and its performance is compared with the predicted performance of a theoretical model. Noise measurements were made in the laboratory at frequencies between 115 GHz and 761 GHz, yielding double-sideband noise temperatures ranging from 33 K to 1100 K. The receiver has also been used for astronomical spectroscopy on the Caltech Submillimeter Observatory (Mauna Kea, Hawaii) at 115, 230, 345, and 492 GHz. >

Range-testing a conical logarithmic spiral antenna for a dual-polarized riometer

The off-axis axial ratios and the radiation patterns of conical log spiral models have been examined experimentally at a single frequency with the objective of finding a circularly polarized antenna of small physical height, suitable for use in decametric dual-polarized riometers. Truncation of a narrow-cone-angle spiral produced rapid axial-ratio degradation below 0.75 \lambda height in tests performed at 960 MHz. A wide-cone-angle configuration was found, however, with all the characteristics desired, particularly axial ratio \cong 1.25 out to 50\deg zenith angle, with height only 0.16 \lambda .

A log-spiral antenna with selectable polarization

It is possible to obtain polarization diversity from one multiple arm logarithmic-spiral antenna. The log-spiral antenna with more than 2 arms can be excited by a single hybrid matrix connected to the antenna terminals at the origin of the antenna geometry, and operated such that currents flow on the arms with phase progression away from the origin and reflected currents flow back along the arms with phase progression toward the origin. These two components of current radiate fields of opposite sense of essentially circular polarization.

The logarithmic spiral in a single-aperture multimode antenna system

The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> -arm logarithmic spiral antenna having <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> distinct terminals may be considered as an ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n-1</tex> )-port antenna. It may be operated simultaneously in ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n-1</tex> )independent balanced modes. By varying the relative excitation of these modes it is possible to produce a variety of patterns that have applications to direction finding, tracking, and homing over a broad range of frequencies. It is particularly easy to obtain useful results in this manner because of some unique properties of the logarithmic spiral. The basic relations between mode excitation and the related fields of these multiarm antennas are reviewed together with some properties that are characteristic of the log-spiral geometry. Multimode single-aperture systems, such as those using a relatively simple hybrid matrix to synthesize multiple beams tilted from the axis of the antenna, are discussed. These tilted beams can be conically scanned about the axis of the antenna by a simple phase shift within the excitation matrix.

Phase velocity on a conical two-armed logarithmic foil-type spiral antenna

From an experimental investigation of the foil-type kind of a conical, logarithmic spiral antenna, the relative phase velocity along the antenna arm as a function of the cone angle has been found. It is probable that a reduction of the antenna length by one half can be achieved by using a special dielectric loading.

Radiation patterns of the logarithmic spiral antenna on an elliptical cone

Radiation patterns of the logarithmic spiral antenna on an elliptical cone

A Note on the Difference Between Equiangular and Archimedes Spiral Antennas (Correspondence)

There seems to exist in the literature considerable confusion about the various types of spiral antennas, their characteristics, and their bandwidth capabilities. One evidence of this confusion appeared in a paper by Bower and Wolfe, in which they state that the Archimedes spiral antenna can be specified in terms of angles and hence belongs in the class of "frequency--independent antennas. "Frequency--independent antennas are relatively new; in fact, until 1955 there was no evidence that a "frequency-independent" antenna did, indeed, exist. Therefore, it would appear appropriate to delineate the characteristics and the terminology of the antennas involved. Perhaps this brief report of some recent work at the University of Illinois Antenna Laboratory will aid in pointing up the differences in operation of the logarithmic (i.e., equiangular) and Archimedean spiral antennas.