DESC:Form 2
The patent Act 1970
(39 of 1970)
AND
Patent Rules 2003
Complete Specification
(Sec 10 and Rule 13)

Title: Electrically small low band frequency independent Antenna
Applicant(s) Entuple Technologies Private Limited
Nationality India
Address # 2730, 80 Feet Road, HAL 3rd Stage Indiranagar,
Bengaluru - 560 038, Karnataka, India

The following specification particularly describes the invention and manner in which it is to be performed.

DESCRIPTION
FIELD OF INVENTION
[0001] The present invention relates to a Sinuous Antennas and more particularly to a method and system to develop an Electrically small low band frequency independent Antenna to reduce a payload and dimensions without compromising on RF performance.
RELATED ART
[0002] A sinuous antenna is a combination of a spiral antenna and a log-periodic antenna. This unique structure results in an antenna that provides broadband performance, is dual-polarized, has a high gain and is stable impedance with frequency. These types of antennas are used in direction finding systems, human health monitoring, electromagnetic pulse (EMP), close-in sensing systems such as ground penetrating radars (GPR), UWB applications such as high-precision indoor positioning and for various other applications.
[0003] These sinuous antennas belong to a larger category of frequency independent antennas that offer wideband performance in terms of all far field radiation parameters (Gain, Axial Ratio, Impedance Matching, Radiation Pattern etc). These antennas radiate on both sides of the radiating element. Hence, a cavity backing is used to make it unidirectional. A balanced input feed with appropriate phase amplitude distribution is required to excite sinuous arms to obtain a desired radiation performance.
[0004] The drawback of this conventional structure is its high payload capacity which makes the application of these antennas and VHF-UHF band challenging.
[0005] Hence, an effective and efficient sinuous antenna is required that reduces a payload and dimensions without compromising on RF performance.
SUMMARY
[0006] In one embodiment, a sinuous antenna 100 comprising: a four arms where its geometry comprises of a cell numbers, a growth rate, a angular width and inner and outer diameter to control a input impedance and a far field radiation performance of the antenna. Each arm of the sinuous antenna is excited by a signal of uniform amplitude and 0.5?? progressive phase difference; a balun (104 & 107) with a profiled microstrip lines to achieve a requisite electrical length in minimum footprint, simultaneously achieving the unbalanced to balanced mode transformation and impedance transformation and also provides a balanced feed lines to carry the guided waves ensuring optimal performance, corrective compensations required to be a balanced radiator; a feed network placed on the bottom PCB used to achieve a phase difference required between the sinuous arms where one port of the feed is connected to an RF signal generating source which divides the incoming signal into two equal amplitude orthogonal signals that are fed to the antenna arms through balun ensuring an optimal radiation performance in minimum footprint area; and an aluminum cavity to make antenna unidirectional radiator, wherein the sinuous antenna 100 reduces a payload and dimensions without compromising on RF performance.
[0007] Several aspects are described below, with reference to diagrams. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the present disclosure. One who skilled in the relevant art, however, will readily recognize that the present disclosure can be practiced without one or more of the specific details, or with other methods, etc. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the features of the present disclosure.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is a schematic view illustrating a sinuous antenna in an embodiment of the present disclosure.
[0009] FIG. 2A is a schematic view illustrating a four-arm sinuous antenna in an embodiment of the present disclosure.
[0010] FIG. 2B is a schematic view illustrating a balun of the sinuous antenna in an embodiment of the present disclosure.
[0011] FIG. 2C is a schematic view illustrating a feed network of the sinuous antenna in an embodiment of the present disclosure.
[0012] FIG. 2D is a schematic view illustrating a aluminum cavity of the sinuous antenna in an embodiment of the present disclosure.
[0013] FIG. 3A and FIG. 3B are images illustrating a VSWR and a Axial Ratio antenna performance in an embodiment of the present disclosure.
[0014] DETAILED DESCRIPTION OF THE PREFERRED EXAMPLES
[0015] FIG. 1 is a schematic view illustrating a sinuous antenna in an embodiment of the present disclosure. As shown in 100, is a sinuous antenna that reduce a payload and dimensions without compromising on RF performance It comprises of four arms where its geometry comprises of a cell numbers, a growth rate, a angular width and inner and outer diameter to control a input impedance and a far field radiation performance of the antenna. Each arm of the sinuous antenna is excited by a signal of uniform amplitude and 0.5?? progressive phase difference. A balun (104 & 107) that comprises a profiled microstrip lines to achieve a requisite electrical length in minimum footprint, simultaneously achieving the unbalanced to balanced mode transformation and impedance transformation. Also, provides a balanced feed lines to carry the guided waves ensuring optimal performance, corrective compensations required to be a balanced radiator. A feed network placed on the bottom PCB is used to achieve a phase difference required between the sinuous arms where one port of the feed is connected to an RF signal generating source. The feeding network divides the incoming signal into two equal amplitude orthogonal signals that are fed to the antenna arms through balun. The feeding network ensures an optimal radiation performance in minimum footprint area. An aluminum cavity is used to make antenna unidirectional radiator.
[0016] FIG. 2A is a schematic view illustrating a four-arm sinuous antenna in an embodiment of the present disclosure. As shown in 200, is an four arm sinuous antenna that comprises of four arms 202 where its geometry comprises of a cell numbers, a growth rate, a angular width and inner and outer diameter to control a input impedance and a far field radiation performance of the antenna. Each arm of the sinuous antenna is excited by a signal of uniform amplitude and 0.5?? progressive phase difference.
[0017] FIG. 2B is a schematic view illustrating a balun of the sinuous antenna in an embodiment of the present disclosure. As shown in 210, a balun that comprises a profiled microstrip lines to achieve a requisite electrical length in minimum footprint, simultaneously achieving the unbalanced to balanced mode transformation and impedance transformation. Also, provides a balanced feed lines to carry the guided waves ensuring optimal performance, corrective compensations required to be a balanced radiator.
[0018] FIG. 2C is a schematic view illustrating a feed network of the sinuous antenna in an embodiment of the present disclosure. As shown in 220, a feed network placed on the bottom PCB is used to achieve a phase difference required between the sinuous arms where one port of the feed is connected to an RF signal generating source. The feeding network divides the incoming signal into two equal amplitude orthogonal signals that are fed to the antenna arms through balun. The feeding network ensures an optimal radiation performance in minimum footprint area.
[0019] FIG. 2D is a schematic view illustrating a aluminum cavity of the sinuous antenna in an embodiment of the present disclosure. As shown in 230, is an aluminum cavity is used to make antenna unidirectional radiator.
[0020] FIG. 3A and FIG. 3B are images illustrating a VSWR and a Axial Ratio antenna performance in an embodiment of the present disclosure. As shown in 300 and 301, depicts the VSWR and a Axial Ratio antenna performance.
[0021] In an embodiment, with the rapid growth of wireless communications and associated demand for high data-rates, many upcoming antennas has to be a ultra-wideband (UWB). A single antenna is certainly a most attractive solution to handling the large bandwidth requirements. Thus, designing such an antenna that is concurrently of low-profile is necessary for mounting on a variety of grounds and airborne vehicles for miniaturizing and widening its bandwidth.
[0022] In an embodiment, the antennas designed to operate at VHF band usually need aggressive miniaturization because their desirable size is small relative to operating wavelengths. Therefore, designing VHF antennas is strongly linked to designing electrically small antennas. Electrically small antennas are well known to excite only the lowest spherical modes in the far-field region, which leads to fundamental difficulties in making them meet all practical requirements such as gain, VSWR, bandwidth, and radiation pattern. Furthermore, as most VHF antennas operate on ground planes or platforms, they have to be separated by a sufficient distance for efficient radiation. This is the fundamental reason why VHF antennas are obtrusive. There has been many attempts in the conventionally to improve VHF antennas through various antenna miniaturization techniques. Those attempts are attractive on their own; however, they did not consider the property of being low-profile. Besides, there have been a lot of antenna miniaturization techniques to shrink antenna size. However, the size of the antenna they deal with is not electrically small enough and they only considered from UHF band to a few GHz. Hence there is no such a novel antenna that features extremely being low-profile at VHF band.
[0023] In an embodiment, when an antenna is electrically small, it is also difficult to widen its operating bandwidth. There is no single definition of bandwidth for all types of antennas. The quality factor Q is inversely proportional to VSWR fractional bandwidth through some mathematical derivations. Therefore, it can be concluded that small Q values has to be achieved to maximize the bandwidth for antennas operating at VHF band.
[0024] In an embodiment, a radiation from any antenna requires a radiating element to correspond to some particular multiple of its radiation wavelength. Thus, a perimeter of the radiating elements corresponds to this wavelength where for circular arcs this multiple is given by the inverse of ?? (0.33). The antenna dimension at the highest operating wavelength has been reduced to 0.17 the radiating wavelength. Therefore, the payload of the antennas has been reduced. In order to ensure optimal performance, corrective compensations has been made in balun and feed network to ensure optimal radiation performance in minimum footprint area.
[0025] While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present disclosure should not be limited by any of the above- discussed embodiments, but should be defined only in accordance with the following claims and their equivalents.
,CLAIMS:CLAIMS
I/We Claim,
1. A sinuous antenna 100 comprising:
a four arms where its geometry comprises of a cell numbers, a growth rate, a angular width and inner and outer diameter to control a input impedance and a far field radiation performance of the antenna. Each arm of the sinuous antenna is excited by a signal of uniform amplitude and 0.5?? progressive phase difference;
a balun (104 & 107) with a profiled microstrip lines to achieve a requisite electrical length in minimum footprint, simultaneously achieving the unbalanced to balanced mode transformation and impedance transformation and also provides a balanced feed lines to carry the guided waves ensuring optimal performance, corrective compensations required to be a balanced radiator;
a feed network placed on the bottom PCB used to achieve a phase difference required between the sinuous arms where one port of the feed is connected to an RF signal generating source which divides the incoming signal into two equal amplitude orthogonal signals that are fed to the antenna arms through balun ensuring an optimal radiation performance in minimum footprint area; and
an aluminum cavity to make antenna unidirectional radiator,
wherein the sinuous antenna 100 reduces a payload and dimensions without compromising on RF performance.
2. The sinuous antenna 100 of claim 1, a perimeter of the radiating elements of the antenna corresponds to this wavelength where for circular arcs this multiple is given by the inverse of ?? (0.33).
3. The sinuous antenna 100 of claim 1, the antenna dimension at the highest operating wavelength has been reduced to 0.17 the radiating wavelength. Therefore, the payload of the antennas has been reduced.
4. Method, system and apparatus providing one or more features as described in the paragraphs of this specification.

Date: 19-01-2023 Signature………………………
OMPRAKASH S.N
Agent for Applicant, IN/PA -1095