# Archimedean spiral

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Related to Archimedean spiral: Logarithmic spiral

## Archimedean spiral

[¦är·kə¦mēd·ē·ən ′spī·rəl]
(mathematics)
A plane curve whose equation in polar coordinates (r, θ) is rm = am θ, where a and m are a positive or negative integer.
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By optimizing all the aforementioned parameters on a 50 mm dia., simple Archimedean spiral antenna, the gain and axial ratio at 2 GHz were still -6 dBi (<-5 dBi) and 5dB (>3dB) while the VSWR was<2:1 throughout the band.
An approach based on the Archimedean spiral is proposed to generate OAM carrying beams in the RF regime.
Figure 10(a) displays the acoustic maps obtained for an Archimedean spiral array and (b) shows those obtained for a star array for a frequency range extending from 500 to 4000 Hz, inclusive.
where [beta] = arctan(-[[theta].sub.2]/[gamma]) is a tangent angle of the Archimedean spiral gear, [gamma] is a reduction gear ratio of the secondary motor, and a = [mu]R = R[[theta].sub.2]/2[pi] is a distance from the pivot point to the joint center.
Handzic started with Archimedean spirals and logarithmic spirals.
Round spiral antennas are generally designed by using Archimedean spiral geometries which have linear growth rates and frequency independent radiative characteristics.
However, all of the Archimedean spiral antennas referred to above cannot eliminate the restraint of the feed balun, in which the structure increases the height of the antenna profile and the complexity of the antenna.
"A two-arm Archimedean spiral antenna with bent ends", IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC), p 535-8, (2012).
The spiral antenna has a two-armed Archimedean spiral with four numbers of turn.
In [1], Aczel and Alsina defined the following n-spiral function F(a, [theta]) and discuss the conditions under which an n-spiral function is the Archimedean spiral a[theta].
It's a perfect fit to an Archimedean spiral: what you get when material streams at a constant speed from a source spinning at a constant rate, such as water from a lawn sprinkler.

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