Patent Application
20080036667
Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:
Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer.
The invention described by this disclosure is a new form of antenna: a Transmission Line Resonant Loop antenna. Resonance is established by looping a transmission line back on itself as in a ring type of arrangement. This avoids having to reflect the energy back on itself as in reflective resonator. In a reflective resonator, at the point of reflection there is either a high electric field (caused by high voltage in a high impedance reflection, such as at the tip of a whip antenna) or a high magnetic field (caused by high current in a low impedance reflection). This antenna, not depending on reflection, has reduced localized electric and magnetic fields.
There is shown in
Loop antenna 14 includes tuning bar 16 as one leg and line 60 is another leg. One end 32 of loop antenna 14 is connected to the end 30 of center conductor 20; the other end 34 is connected to the reference terminal 36 of excitation source 38. The signal terminal 40 of excitation source 38 is connected to end 28 of center conductor 20 through line 58. Tuning bar 16 connects to ends 24, 26 of shield conductor 22, at 42, 44. Its connection to shield conductor 22 defines the length of coaxial cable 18, in this case λ/2. The position of tuning bar 16 sets this length and is used to tune transmission line resonator 12. Good results for a 170 MHz resonator have been obtained with an excitation of approximately 10 volts and 200 ma. The radiation loop area 46 is defined by loop 14. While transmission line resonator 12 provides the resonator function it operates virtually independent of the presence, proximity or absence of a ground plane or conductor. This is so because the shield conductor 22 acts as the self contained ground plane which has a predetermined and fixed effect on the transmission line resonator. This greatly reduces the effect of any conductors in the area.
In operation, excitation source 38 provides an input excitation signal 50 at end 28 and a reference excitation signal 52 at end 34, which changes polarity (direction) each half cycle. Correspondingly, the increased resonant currents 54, 56 flow in opposite directions to currents 50, 52, respectively, changing direction each half cycle.
The λ/2 transmission line resonates to produce high impedance voltages shown as + at 28 and − at 30 in
The preferred orientation to nearby conductors (such as the chassis of a vehicle) is such that the shorting bar side of the antenna faces the nearby conductors. The voltages at the ends of the center conductor 28, 30 are isolated from nearby conductors by the presence of shield conductor 22, resulting in less detuning. Another advantage of coaxial cable 18 is that it can be configured in an indirect, convoluted path such as a coil or helix 18a,
This invention is not limited to any particular construction. For example, the transmission line resonator 12b,
Comparing
Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments.
In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant can not be expected to describe certain insubstantial substitutes for any claim element amended.
Other embodiments will occur to those skilled in the art and are within the following claims.
