Abstract
A low-profile axial mode helical type antenna that employs hollow copper tubing for the radiating element, a singular semi hollow dielectric support structure, low pitch angle and an improved/simplified parallel open wire impedance matching technique. This antenna has a wide radiating pattern as well as high forward gain and circular polarization. It is designed to work in the field of live entertainment including reception and transmission of wireless microphones, in-ear monitors, communications and cue control systems. It operates from 470-663 MHz.
Claims
1. A circularly polarized axial mode helical antenna assembly which comprises of; i. a circular polarization and forward gain, which further comprises a ground plane; ii. a singular semi solid dielectric support structure; iii. a hollow radiating helix element and; iv. a dielectric protective covering.
2. A circularly polarized axial mode helical antenna as in claim (1) wherein said singular semi hollow dielectric support structure is one piece of FDM 3D printed dielectric material.
3. A circularly polarized axial mode helical antenna as in claim (1), wherein said singular semi hollow dielectric support structure has an internal material density of 20%.
4. A circularly polarized axial mode helical antenna as in claim (1) wherein said ground plane is made of circular disk-shaped aluminum.
5. A circularly polarized axial mode helical antenna as in claim (1) wherein said circular disk-shaped aluminum ground plane dimensions consist of a diameter of 381 mm and a thickness of 3.175 mm.
6. A circularly polarized axial mode helical antenna as in claim (1) wherein said hollow radiating helix element has a pitch angle of 5.5 degrees.
7. A circularly polarized axial mode helical antenna as in claim (1) wherein said hollow radiating helix element further comprises of hollow copper tubing.
8. A circularly polarized axial mode helical antenna as in claim (1) wherein said hollow radiating helix element of further comprises of copper tubing with an exterior diameter of 6.35 mm.
9. A circularly polarized axial mode helical antenna as in claim (1) wherein said hollow radiating helix element and said copper tubing makes 3 complete turns.
10. A circularly polarized axial mode helical antenna as in claim (1) wherein said antenna assembly has an operating frequency of 470 to 663 MHz
11. A circularly polarized axial mode helical antenna having an open wire parallel feed point mechanism that is an intermediary connection between the connector terminal of the antenna and the hollow radiating helix element that serves as an impedance matching network for the circularly-polarized axial mode helical antenna, comprising; a section of solid copper wire where one end is attached to the beginning of the hollow radiating helix element, the other end connecting to the hollow radiating helix element approximately ¼ wavelength from the beginning of the hollow radiating helix element and the connection to the antennas connector terminal is done at a right angle section near the beginning of the open wire parallel feed point mechanism.
12. A circularly polarized axial mode helical antenna as in claim (11) wherein said open wire parallel feed point mechanism is a solid copper wire at 32.3% percent the size of the hollow radiating helix element it is parallel to.
13. A circularly polarized axial mode helical antenna as in claim (11), wherein said open wire parallel feed point mechanism and said solid copper wire is 140-145 mm in total length.
14. A circularly polarized axial mode helical antenna as in claim (11), wherein said solid copper wire has a 90-degree bend 10-15 mm from the beginning of the wire.
15. A circularly polarized axial mode helical antenna as in claim (11) wherein said solid copper wires 90-degree section is the only conductive element in the radiating structure to make direct contact with the antenna connector terminal.
16. A circularly polarized axial mode helical antenna as in claim (11) wherein said solid copper wire connects to the hollow radiating helix element in two places (at the beginning of the hollow radiating helix element and 115-120 mm from the beginning of the hollow radiating helix element).
17. A circularly polarized axial mode helical antenna of as in (11) wherein said solid copper wire can be moved closer or farther from the ground plane for fine impedance matching.
18. A circularly polarized axial mode helical antenna as in claim (11) wherein said solid copper wire can be moved closer or farther from hollow radiating helix element for fine impedance matching.
19. A circularly polarized axial mode helical antenna as in claim (11) wherein said solid copper wire is attached to the hollow radiating helix element by passing through the entirety of the hollow radiating helix element and soldered to the exterior of the hollow radiating helix element.
20. A circularly polarized axial mode helical antenna of as in claim (11) wherein said hollow radiating helix element connects to right angle portion of solid copper wire at 16 mm above the ground plane.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1, is an exploded view containing an overview and all the parts involved in the entire antenna;
[0018] FIG. 2, is a side view of the antenna assembly minus the dielectric cover showing the impedance matching section and dimensional relationships of the antenna;
[0019] FIG. 3, is an expanded view of the impedance matching section from FIG. 2, showing details of the impedance matching section;
[0020] FIG. 4, is a cross section view showing the interior makeup of the dielectric support structure and the helix radiating element;
[0021] FIG. 5, is an exterior view of the completed antenna assembly;
[0022] FIG. 6, is a chart representing the impedance match for the antenna;
[0023] FIG. 7, is a graph representing the gain for the antenna.
DETAILED DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1, is an exploded view containing an overview of all the parts involved in the entire antenna. A winding of hollow copper tube with an exterior diameter of 6.35 mm forming a helix type shape can be seen in (104). This helix is the main radiating structure of the antenna. Its shape, which resembles 3 coils, or circles, is largely what creates the circular polarization of the antenna. The circumference of the coils, as well as the spacing between the coils, are important to the operating parameters of the antenna, therefore a dielectric support structure, (103), maintains the dimensional accuracy of the helix. The dielectric support structure (103) also serves as a non-conductive mount to suspend the helix perpendicularly above ground plane (101). Dielectric support structure (103) is attached to ground plane (101) through holes in ground plane (101) and dielectric support structure (103) using screws (109) and nuts (110). The ground plane (101) is 381 mm in diameter, 3.175 mm thick and is generally comprised of 5052 aluminum. The ground plane (101) is essential to the axial mode helical antenna and is largely what creates forward gain. Helix (104) and ground plane (101) are both connected to N type connector (102) which serves as the input/output terminal for the antenna assembly. N type connector (102) is mounted to ground plane (101) through holes in ground plane (101) using screws (107) and nuts (108). A dielectric cover (105) comprised of 3.175 mm thick extruded ABS plastic protects the helix (104), the dielectric support structure (103) and a portion of the type N connector (102). The dielectric cover (105) is attached to the ground plane (101) using a piece of edge trim (106) that overlaps ground plane (101) and dielectric cover (105) pushing them together throughout the outer circumference of ground plane (101) and dielectric cover (105). The edge trim (106) consists of a soft rubber exterior and a flexible metal interior that grabs components inside it to keep them firmly secured such as ground plane (101) and dielectric cover (105).
[0025] FIG. 2, is a side view of the antenna assembly, minus the dielectric cover, showing the impedance matching section and dimensional relationships of the antenna. A smaller wire running parallel to the first ¼ turn of the helix can be seen in (201), this is the parallel open wire impedance matching section and will be described in detail in further figures. The diameter of the helix “D” (205) is approximately 163 mm and corresponds to a circumference of 513 mm. These dimensions are directly related to the antennas operating range and puts the primary operating frequency of the antenna at 584 MHz. This was the center frequency for the United States UHF TV band of 470-698 MHz. However, this band has changed. The antenna is tuned using the parallel open wire impedance matching section (201) to an operating range of 470-663 MHz. The axial length of the helix “L” (206) is 150 mm and consists of 3 turns. This is the minimum number of turns to achieve circular polarization. The low number of turns combined with the axial length “L” (206) provide a more compact version of an axial mode helical antenna that achieves both a wide pattern and a high forward gain, which is usually inversely proportional where a wide pattern would equal a lower forward gain. This is possible by using a larger diameter conductor in the helix (104) and by using a pitch angle, “S” (204), much lower than specified by the classic helical formula of 12-14 degrees. The pitch angle, “S” (204), for the turns of helix (104) is 5.5 degrees. This makes the spacing between the turns of helix (104) 50 mm. Along with the electrical effects of a wide pattern with high gain, a 5.5-degree pitch angle, “S” (204), is how length “L” (206) can be as short as 150 mm while still containing 3 turns. This axial length is 40% smaller than a standard axial mode helical type antenna utilizing similar operational characteristics and does not detrimentally affect the antenna's electrical performance. Not generally used in all the antenna art, is the mounting block seen in (202). The mounting block (202) attaches to ground plane (101) and has a receptacle with 5/8-27 UNS threading to attach the antenna to common live entertainment mounting systems. To reduce weight for increased portability, openings (203) are added to the dielectric support structure (103).
[0026] FIG. 3, is an expanded view of the impedance matching section from FIG. 2a, showing details of the impedance matching section, where the parallel open wire impedance matching section (201) is created using a solid copper wire approximately 32.2% the size of the hollow copper tube used in the helix (104). For the frequency ranges involved with this antenna of 470-663 MHz, the parallel open wire impedance matching section (201) is made from 12 AWG solid copper wire. The 12 AWG solid copper wire from the parallel open wire impedance matching section (201) is electrically connected to the Type N connector (102) at terminal (208) at a 90-degree section 15 mm from the beginning of the 12 AWG solid copper wire that makes up the parallel open wire impedance matching section (201). One side of the 12 AWG solid copper wire from the parallel open wire impedance matching section (201) connects to the helix (104) through a hole at the beginning of the helix seen at (209) and then soldered into place. The other side of the 12 AWG solid copper wire from the parallel open wire impedance matching section (201) connects to the helix (104) through a hole 115 mm from hole (209) as seen in (210). The 12 AWG solid copper wire from the parallel open wire impedance matching section (201) that passes through hole (210) is then soldered into place. The 12 AWG solid copper wire from the parallel open wire impedance matching section (201) can then be bent closer or farther from the ground plane (101) for fine tuning of the impedance match. The 12 AWG solid copper wire from the parallel open wire impedance matching section (201) can also be bent closer or farther from the helix (104) for fine tuning of the impedance match. Through this fine tuning the impedance match can achieve an average reflected power of approximately 1% through the operational range of the antenna of 470-663 MHz
[0027] FIG. 4, is a cross section view showing the interior makeup of the dielectric support structure and the helix radiating element, one can see that the helix (104) is a hollow copper tube. The hollow copper tubing of helix (104) has an exterior diameter of 6.35 mm referenced in (301). The thickness of the hollow copper tubing from helix (104) is approximately 91 mm references in (302). These dimensions are important to the antenna's operation. In general, the larger the element of an antenna, the greater the operational bandwidth. However, radio waves, like the ones that will be radiated from an antenna, are an alternating current. It is well known that alternating currents, especially at higher frequency, experience something called skin effect. This is where the AC current only flows on the outer most diameter of the conductor it is passing through. The hollow copper tubing of helix (104) has a large enough exterior diameter of 6.35 mm as seen in (301) to maintain a large operating bandwidth and impedance match, and because of the skin effect, the 91 mm thickness of (302) is enough conductive material to make helix (104) an exceptional radiating element. Thus, the benefit of a large operating bandwidth and impedance match is achieved by the outer diameter of Helix (104) without adding excessive weight due to helix (104) being comprised of hollow copper tubing aiding in portability. The interior of dielectric support structure (103) can be seen in (303) to be a semi hollow structure with a 20% interior material density. It is made of PLA+ type plastic and printed as one piece from an FDM type 3d printer. The semi hollow interior of dielectric support structure (103) seen in (303) gives the benefit of a reduced relative permittivity compared to a solid dielectric support structure of the same size. This reduced relative permittivity means that the dielectric support structure (103) introduces minimal dielectric loss to the radio waves traveling through helix (104). In contrast, a high relative permittivity can reduce the overall gain of the antenna. Thus, the semi hollow interior of dielectric support structure (103) seen in (303) helps maintain the antennas high forward gain, even though the antenna has a wide radiating pattern. The external thickness of dielectric support structure (103) as seen in (304) is approximately 6.96 mm providing a large enough structure to adequately support the size of the helix (104) and maintain its dimensional accuracy.
[0028] In FIG. 5, an exterior view of the completed antenna assembly is disclosed. One can see a representation of the completed antenna (401), where dielectric cover (105), not shown, as it is now part of (401), is in place covering the antenna assembly and attached to ground plane (101), not shown as is covered, with edge trim (106). Also not shown is mounting block (202) on the back side of the assembly.
[0029] In FIG. 6, a chart representing the impedance match for the antenna, we can see that the horizontal line representing the percent reflected power over frequency stays under 1% for the majority of the antenna's operating bandwidth. This equates to a calculated average reflected power of 1% throughout the antennas operating bandwidth. What has been shown fully in the description and drawings is an improved and shortened axial mode helical type antenna with a superior impedance match achieving an average reflected power of 1% through the antenna's bandwidth.
