Patent Grant
9912064
The present invention is in the technical field of radio communications. More particularly, the present invention is in the technical field of antenna design.
A dipole antenna is the simplest form of radio antenna. It consists of two electrically-conductive elements positioned such that passing radio waves cause a voltage differential between the two elements.
In the case of radio signal reception, this voltage differential, however small, is passed through a feed line to a radio frequency (RF) receiver where it is converted into audio, video, text or other content.
In the case of transmission, an oscillating voltage differential is generated by a radio transmitter and passed to the antenna by way of a feed line, creating radio waves in space.
Dipole antennas may be “balanced”, having two elements of equal lengths with a feed point in the center. Or they may be “end-fed” with one element making up nearly the entire length of the antenna, with the feed point at or near the very end of the configuration. In reality, this type of antenna may be constructed with the feed point at any point between the end points with an impedance matching transformer used just below the feed point.
This type of antenna may be linear, with the two elements occupying a single line in space (or nearly a single line). Or they may be placed in an “inverted V” configuration with the feed point elevated above the two end points. Indeed, there are many serviceable configurations of a dipole antenna.
Changes to the position of the feed point and/or the configuration of the elements may cause a change or imbalance in the overall electrical impedance of the antenna. (Impedance is a combination of inductance, capacitance, and resistance and is measured in Ohms, signified by the capital Greek letter, Omega.)
Differences between the impedance of the antenna and the required impedance of the attached radio device are mitigated by the use of an “impedance matching transformer”.
A dipole antenna of a given overall length is most effective at receiving or emitting radio waves whose wavelength is TWICE the overall length of the antenna (with a correction applied for different element materials and insulations). In the case of reception, this ratio of antenna length to wavelength produces the maximum voltage differential across the elements. Conversely, during transmission, this ratio produces the maximum amplitude of radio wave for a given voltage differential applied to the antenna.
The impedance of a fixed-length dipole antenna changes across the frequency spectrum. The impedance of an antenna of length L may be 50 Ohms at 14.050 MHz, but may be 5 Ohms at 14.450 MHz.
Likewise, the standing wave ratio (SWR) of an given-length antenna will change across the frequency spectrum, changing the antenna efficiency as frequency changes while length is held constant.
Therefore, for a given frequency or frequency band, a specific overall length of dipole antenna is highly preferable for maximum efficiency.
An external antenna tuner may be used to compensate for an antenna that is not ideally matched to the frequency in use, however, this tuner cannot make an inefficient antenna ideally efficient, it can only make the antenna usable (such as not to damage radio equipment).
Ideally, for maximum radiating efficiency, with or without the use of an antenna tuner, the overall length of the dipole antenna is at or near ½ the wavelength of the frequency in use.
Traditionally, there have been two methods for creating dipole antennas suitable for multiple bands: telescoping and the use of traps.
Telescoping antenna elements are highly familiar in the form of the typical home TV rabbit-ear antennas. This device, however, becomes cumbersome and difficult to sustain at longer wavelengths—imagine a rabbit-ear antenna where each element telescopes out to 10 meters.
For longer HF applications, traps have been traditionally used. A trap is essentially a small inductor-capacitor circuit which has a fix resonant frequency which falls between the two bands it separates. The result is a fixed-length antenna which approaches maximum efficiency on multiple bands. (The costs of this solution are financial, inconvenience and in weight.)
The present invention is a novel antenna construction technique which can be applied, as an improvement, to a variety of existing antenna designs which uses rigid or flexible wire segments which can be attached or detached quickly and easily using low-loss, electrically conductive, quick connect/disconnect connectors paired with a securing device such as, but not limited to, a standard o-ring or Zip-Strip, to alter the overall length of the antenna elements to make the antenna highly efficient on a variety of frequencies or frequency bands—OR—to quickly reconfigure the feed-point location along the same antenna.
This design is lighter in weight, cost effective and convenient when compared to fixed-length antennas, telescopic antennas or antennas using traps.
A third advantage is the quick and easy conversion from center-fed to end-fed (or to a variety of feed point positions). Segments of the antenna may be quickly and easily rearranged such that the feed point is at or near the end of the antenna and an impedance matching transformer may be applied. This quickly and easily converts the antenna from a balanced dipole to an end-fed dipole—a conversion which is difficult or impossible when using fixed-length wire, wire with traps or telescopic antennas.
As mentioned above, this antenna design feature may be applied to a variety of existing antenna designs such as, but not limited to center-fed dipole antennas, end-fed dipole antennas, inverted-V dipoles, Eyring (ELPA) antennas (which is essentially an array of dipole antennas), and others.
The improvement presented here is particularly relevant to the Eyring (ELPA) antenna and other tactical antennas, where stealth, speed and radiation efficiency are high-priority attributes of the application.
We believe this methodology will yield a performance improvement over the traditional Eyring design where elements are trimmed by taking up wire onto a (plastic) spool which creates both inductance and capacitance to electrically alter the length of the element. Since capacitance and inductance in an antenna can be mutually cancelling and inductance at the end of an antenna leg yields sub-optimal efficiency, we believe our improvement would yield a performance increase.
We also believe this methodology, when applied to the Eyring (ELPA) antenna will yield improved speed and stealth, and therefore reduced risk to human life by allowing the user to re-tune the antenna by simply removing a fixed, pre-measured length of antenna element rather than pacing out and spooling up a length of antenna wire for each of the four legs.
The invention described here is an antenna created in rigid or flexible (coilable) wire segments which can be attached or detached quickly and easily with electrically conductive, quick connect/disconnect connectors to alter the overall length of the antenna to make it highly efficient on a variety of frequencies or frequency bands.
This design is lighter in weight, cost effective and convenient when compared to fixed-length antennas, telescopic antennas or antennas using traps.
A third advantage is the quick and easy conversion from center-fed to end-fed (or to a variety of feed point positions). Segments of the antenna may be quickly and easily rearranged such that the feed point is at or near the end of the antenna and an impedance matching transformer may be applied. This quickly and easily converts the antenna from a balanced dipole to an end-fed dipole—a conversion which is difficult or impossible when using fixed-length wire, wire with traps or telescopic antennas.
A user who is communicating on 10 meter band using segment “A”, may switch to 15 meter band simply by snapping in place one or more additional wire segments (segment “B”) onto the end of their antenna. This additional segment would be trimmed such that, when combined with segment “A”, the overall antenna length is optimal for 15 meter band frequencies.
A user is hiking/camping cross-country. At site A, they are camped among tall trees and user has his antenna configured as center-fed with segments in place for efficiency on the 20 meter band. The next day, user hikes 10 miles to a site where there is only 1 tree and no other tall structures. User unsnaps his feed point from the middle of the antenna and snaps together the two polar segments of the antenna. She then quickly snaps her feed point onto the one end of the antenna and snaps a terminal connector (non-element, rope loop for hanging) on to the other feed point connector. User throws a weighted pilot string high up tree, connects rope and other terminal connector to other end of antenna and pulls one end of antenna high up into tree. The lower end of antenna is connected (insulated or not) to a spike in ground away from the tree. The result is a sloping end-fed dipole antenna.
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Two feed lines are connected to splitter 6 in the middle of the antenna field. The feed point connectors 7 divide the two conductors of each feed line and pass them in different directions to quick connect/disconnect connectors 1. Next are the segments for Band A, 2, which, in turn connect with connector 1 to the segments 3, which, in combination with segment 2 are trimmed for Band B. This scheme is continued through element segment 5, which, in concert with all preceding segments is trimmed for maximum efficiency on Band n.
This novel construction of the ELPA using our technique stands in contrast to the traditional method of trimming (tuning) an ELPA antenna which is to coil excess element wire onto spools which would remain attached at the end of each leg of the antenna. We believe our novel methodology yields increased performance do to the removal of the coils of wire on plastic spools which imply both large inductance and significant capacitance added at the end of each leg of the antenna.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2998604 | Seeley | Aug 1961 | A |
| Number | Date | Country | |
|---|---|---|---|
| 20170033456 A1 | Feb 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62231132 | Jun 2015 | US |
