Patent Application
20150077302
1. Field of the Invention
The present application relates to antennas for electromagnetic radiation.
2. Description of Prior Art
Conventional antennas are, e.g., 0.5λ (λ=wavelength) long. There is, therefore, a need of shorter antennas that still have acceptable electromagnetic properties.
The emission of E & M from antennas is discussed in U.S. Pat. No. 5,155,495 which discloses a Crossed field antenna and in U.S. Pat. No. 5,495,259 which discloses a compact parametric antenna. It is desirable to have small compact size antenna for the 1 kHz to 900 Mhz frequency range.
The salient feature of the proposed invention is an antenna construction suitable for transmitting 1 kHz to 1 GHz E & M radiation from an oscillator using a small antenna of length 1 cm to 1 meter size formed of an array of magnetic and dielectric particles of nm to mm range sizes in a polymer host to effectively function as λ/2 size antenna with antenna sizes of a few cm to meters.
The random walk and hopping of EM energy waves among nm to mm particles [see
L
eff
L
2/2ltr (1)
where L is the physical size of the antenna, ltr is the transport scattering random walk length between particles, and the effective length of the antenna is Leff=2.
The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein:
The elongate core 101 is generally cylindrical and shown as a uniform cylinder having a round cross-section and in the form of a tube or rod defining an axis A. The core length L is selected to be within the range RF/HF and formed of any suitable material such as a polymer, liquid, glass and ceramic. The dimension L and the nature, number and concentration of particles is selected to accommodate frequencies from 1 KHzx to 900 MHz by selecting particle sizes within the range of 1 mm to μm size with a nominal size of 100 nm in size. To accommodate a wider range of frequencies a mixture of particles of nm and μm sizes may be used.
Any particles may be used that have high values of μ and ε. Thus, the following materials are examples of particle materials that can be used: barium-ferrite, strontium-ferrite, lanthanum strontium ferrite, copper-iron oxide, lithium iron (III) oxide, nickel zinc iron oxide, copper zinc iron oxide.
The random walk scattering and hopping of E & M radiation (107) is shown in
The transport mean free path ltr defined as the distance in which a photon is fully randomized (forgets its original direction of motion) after numerous scattering events, as illustrated schematically, in
<ltr>=Σls{circumflex over (n)}, (2)
where {circumflex over (n)} represents the vector displacement of a photon in turbid media. Written explicitly,
<ltr>=<ls+ls cos θ+ls cos2θ+ls cos3θ+. . . +ls cosnθ+. . . >
<ltr>=ls/(1−<cos θ>)=ls/(1−g), (3)
One also defines the reduced scattering coefficient,
μs′μs(1−g)=(ltr)−1. (4)
The parameters lu, ls, μa, and μs are intrinsic properties of the material medium and are given by
l
s=μs−1=(Nσs)−1, and la=μa−1, (6)
where N is the volume concentration of particles, and σs and σa are the scattering cross section and absorption cross section, respectively.
The intensity of snake light is found, from experiments, to follow the equation;
I
s(Δt)=A exp[−bz/ltr], (7)
in time interval Δt, where b is a parameter that depends on Δt, and has an average value of 0.8. The snake light is portion of the photons that arrive before multiple-scattered diffusive photons and after the ballistic component
The values of g, ls and ltr depend on particle size and are calculated using Mie scattering theory. The g factor greatly depends on wavelength, especially when particle size is less than 1 μm, which is close to the wavelengths of 0.527 μm and 1.054 μm. For Intralipid-10% suspension with an average particle diameter of ˜0.5 nm, the values of g will be ˜0.9 and ˜0.6 for 0.527 μm and 1.054 μm, respectively.
At larger particle diameters, g oscillates around 0.85 with a deviation of ˜5% for the wavelength of 1.054 nm. Due to the wavelength dependence, there is smaller difference between ltr and ls for particles with smaller diameter. When the diameter increases, the difference increases. When diameter is more than 3 μm, the difference in values of both lt and ls increases for the two wavelengths.
Table 1 shows the effective smaller or reduced length of antenna 10, showing the frequency f, λ and λ/2 and the size L of the antenna for typical frequencies ranging from 3 Mhz to 3 Ghz for effective half wavelength operation.
where L=length of antenna, Leff=λ/2, and ltr is the transport random walk transport length: Leff=L2/2ltr
The above-described embodiments are given as illustrative examples only. It will be readily appreciated that many deviations may be made from the specific embodiments disclosed in this specification without departing from the invention. Accordingly, the scope of the invention is to be determined by the claims below rather than being limited to the specifically described embodiments above.
| Number | Date | Country | |
|---|---|---|---|
| 61802910 | Mar 2013 | US |
