US 3299428 A
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Description (OCR text may contain errors)
Jan. 17, 1967 P. TESSARI Ill 3,299,428
HORIZONTAL SEMIENCLOSED LOOP WITH CONDUCTIVE GROUND PLANE, HAVING VERTICAL WHIP EXTENDING FROM WITHIN LOOP ENCLOSURE Filed Sept. 11, 1964 2 Sheets-Sheet FIG- I INVENTOR LAWRENCE R TESSARI m ATTORNEY Jan. 17, 1967 L. P TESSARI in HORIZONTAL SEMIENCLOSED LOOP WITH CONDUGTIVE GROUND PLANE, HAVING VERTICAL WHIP EXTENDING FROM WITHIN LOOP ENCLOSURE Filed Sept. 11, 1964 2 Sheets-$heet 2 moi m m A R S O 5 T E m T a W R I. w 0 N w M A W A L ZZmPZ Y .rzwmum B 80 m9 m 0? .m. 0 -m+ 02nd UnitedStates Patent 3,299,428 HORIZONTAL SEMIENCLOSED LOOP WITH CON- DUCTIV E GROUND PLANE, HAVING VERTICAL WHIP EXTENDING FROM WITHIN LOOP EN CLOSURE Lawi'ence P. Tessari III, 5871 Pine,
Taylor, Mich. 48764 Filed Sept. 11, 1964, Ser. No. 395,956 9 Claims. (Cl. 343-743) This invention relates to an antenna particularly adapted to be used as both a transmitting and a receiving antenna for a mobile radio station operating in the general range of the higher frequency amateur bands, that is, from approximately 2 to 150 megacycles. It provides an especially compact configuration and presents a very high radiation efficiency with respect to more conventional antennas when employed within these bands.
Mobile antennas are usually low efficiency radiating devices. A center loaded whip, usually thought of as the most efficient mobile antenna, may be 30 db below a full sized reference dipole antenna in radiating efiiciency at a frequency of about 4 megacycles. This low efiiciency is partially due to the ground loss of the vehicle but a largepart of the inefficiency results from the necessity of employing antennas which are much smaller than required for a maximum efficiency and a consequent necessity to employ loading devices in the form of lumped constant coils and capacitors in order to electrically tune the antennas to the stations frequency. These lumped constants are negligibly efficient as radiators and constitute a major portion of the inefficiency of the mobile antennas. When lumped constants are necessarily employed it is desirable, when possible, toemploy capacitors rather than inductors because a theoretically perfect capacitor is much more easily achieved in practice than a theoretically perfect inductance.
I antenna is necessary to provide an exact tuning a capaci- Another problem associated with the mobile antennas configuration which may be employed for both transmitting and receiving on mobile equipment wherein little, if any, lumped loading constants must be employed, in which these lumped loading constants may be capacitors, and in which a DC. short to ground may be employed without reducing the antennas'transmission efficiency. The antenna is characterized by an extremely high radiating efiiciency relative to its dimensions, this efficiency appreciably exceeding other known mobile antenna configurations.
In a preferred embodiment of the invention, which will be subsequently disclosed in detail, the antenna takes the form of a wire ring having an opening along its length, disposed parallel to and slightly raised above some relatively large metallic surface of the automobile, such as the roof or the trunk lid, which acts as a ground plane. One of the ends of the ring connects to a radially extending connecting section which terminates at the center of the ring in a right angle bend, thereby forming a stub end which extends along the axis of the ring in a direction away from the plane of the ring. The other end of the ring is connected directly to the metallic surface thereby forming a DC. short to ground for the elimination of precipitation static during receiving. An input coaxial line from the transmitter receiver connects to the two open ends of the ring. In the event that some loading of this tor may be inserted between the right angle bend which joins the radial section to the axially extending section and the other side of the capacitor may be connected to the ground surface.
This antenna may be viewed as a directional discontinuity ring radiator combined with a whip antenna. The directional discontinuity ring radiator (DDRR) is described in CO Magazine, June 1964, pages 2831. It basically comprises an open ended loop disposed parallel to, and above, a metallic ground plane. This antenna exhibits a normally inductive impedance and it therefore neatly matches the normally capacitive impedance exhibited by a Whip antenna. By connecting them in the manner specified their capacitive and inductive impedances balance out so as to provide a primarily resistive impedance and a resultant high radiating efficiency. The relative positions of the antenna members in the inventive configuration are such as to provide reinforcement rather than interference between the radiated waves sections, adding to the high radiation eificiency.
The exact dimensions and configuration of the inventive antenna are dependent upon the maximum dimensions imposed by the physical configuration of its mounting and the frequency on which it is used. It has been found that the developed length of the antenna should equal the full quarter wave length. This is, of course, not possible at the lower frequencies and the capacitor, preferably variable, must be used as a tuning element.
It is therefore seen to be a primary object of the present invention to provide a mobile antenna which consists of a circular open-ended radiating element mounted in ahorizontal plane a short distance above an electrical ground plane and having one of its ends connected to a generally radial segment which is, in turn, connected to an axially extending whip section.
Other objects, advantages, and applications of the present invention will be made apparent by the following detailed description of the preferred embodiment of the invention. The description makes reference to the accompanying drawing, in which: FIGURE 1 is a perspective view of an antenna formed in accordance with the present invention: and FIGURE 2 is a graph radiating power versus frequency for the antenna of the preferred embodiment, 2. standard dipole antenna, a whip antenna, and a DDRR antenna.
Referring to the drawing, the disclosed embodiment of the present invention is preferably used on an automobile or other mobile vehicle and is mounted in proximity to a generally horizontal sheet metal section of that vehicle, indicated at 10, which may constitute a section of the roof or the trunk lid thereof. Supported above the surface 10, which acts as an electrical ground plane, is a ring 12 formed of wire, preferably having a circular configuration. The ring 12 is not quite closed. The ring 12 is supported above the ground plane 10 on a number of insulators 14 which are spaced at regular intervals about the ring. The two open ends each lead into right angle connecting sections. One connecting section 14 extends radially inward to the center of the antenna. The radially extending section 15 connects toand is formed integrally with a whip section 18 which joins the section 16 at a right angle bend at the center of the ring 12 and extends axially away from the plane of the ring. The extreme end of the whip section 18 may be provided with a ball for decorative purposes and for minimizing corona discharge.
The other end of the ring 12 terminates in a short connecting section 22 which extends perpendicularly from the plane of the ring and makes contact With the metallic ground plane 10. The end of the section 20 may be soldered or otherwise electrically connected to the metallic plane. I
The antenna makes connection with a transmitter and receiver through a lead-in line 24, which preferably takes the form of a coaxial cable. One of the wires of the cable 26 is connected to the ring 12 immediately adjacent the joinder with the connecting section 20 and the other cable lead 28 is connected to the ground plane.
The developed length of the antenna may be made equal to one quarter of the wave length of the operating frequency. When this is not possible, the antenna must be tuned to the operating frequency by a capacitor 30 which connects electrically to the right angle bend between the connecting section 15 and the whip section 18 and also to the metallic ground plane 10. The capacitor 30 may also serve as a support for the whip section. The capacitor 30 may be fixed or variable in order to adjust to various operating frequencies.
In contrast to a conventional DDRR antenna, wherein the developed length of the ring must be at least a quarter wave length in order to obtain natural resonance, in the present invention the developed length of the entire antenna, including the ring 12, the connecting section 16, and the Whip 18, may be included in determining the resonant length. Thus, the present antenna may have an appreciably smaller diameter than an equivalent DDRR antenna, and as has been noted, its overall radiation efficiency is higher. The ratio between the diameter of the ring 12 and the length of the whip antenna whip section 18 is dependent upon the physical configuration. Normally the diameter 12 will be made equal to or slightly smaller than the length of the whip. This re sults in a compact and stable configuration.
It should be recognized that the configuration of various embodiments of the present invention need not be identical with that of the preferred embodiment: that is, the ring 12 need not be absolutely circular, although noncircular configurations do not result in increased efiiciency: the whip section 18 need not be exactly in center and it would be possible to use a conducting section other than wire for the connecting section 15. Other variations may be made within the spirit of the following claims.
FIGURE 2 is a graph of the radiation efiiciencies of a number of antennas, including an embodiment of the present invention, plotted as a function of frequency. On the chart the vertical parameter is radiated power ratios taken with respect to a full sized dipole. For purposes of preparing this graph a DDRR antenna, a whip antenna, and an embodiment to the present invention, each tuned to 28 megacycles, were employed. It should be noted that the present antenna was less efiicient than the DDRR antenna but much more efficient than the whip antenna below approximately 4 megacycles. Between 4 megacycles and approximately 8 megacycles the present antenna was more efficient than either a DDRR or a whip. Above approximately 8 megacycles the whip became slightly more efficient than the present antenna although the present antenna was much more efiicient than the DDRR. The antenna of the present invention thus exhibited a relatively good gain over a wider band width than either the DDRR or a whip antenna.
The present antenna may of course be employed in fixed as well as mobile situations.
Having thus described my invention, I claim:
1. An antenna, comprising: a planar metal section generally disposed in the horizontal plane: an elongated conductive section disposed above said metallic plane, bent into a semienclosed configuration lying in the horizontal plane: a straight elongated whip section extending in the vertical direction from a point within said semienclosed configuration away from said planar section: and a conductive connecting section joining one end of said semienclosed configuration to the end of said whip section which is within said semienclosed section.
2. An antenna, comprising: a metallic ground plane disposed in the horizontal plane: an elongated conductive and within the enclosure of such section in a direction away from the ground plane: and a conductive connecting section joining one end of said semienclosed section to the end of the whip within the plane of said section.
3. An antenna operative to be connected to a transmitter-receiver by means of a two wire lead-in cable, comprising: a metallic ground plane: an elongated conductive section bent into a configuration which is closed but for a relatively short gap between the ends thereof disposed parallel to and separated from said ground plane: an elongated whip section extending in a direction perpendicular to said ground plane from a point within the plane of said semienclosed section and within the enclosure thereof in a direction away from the ground plane: a first connecting section joining one end of said semienclosed section to the end of the whip within the plane of said semienclosed section: a second connecting section joining the other end of said semienclosed section to said ground plane, said second connecting section extending perpendicular to the ground plane: and connections between one end of said semienclosed section, the ground plane, and the two wires of said lead-in.
4. The structure of claim 3 wherein the developed length of the semienclosed section, the first connecting section, and the whip is approximately equal to one quarter wave length of the operating frequency of the antenna.
5. An antenna operative to be connected to a transmitter-receiver by a two connector lead-in, comprising: a metallic ground plane: an elongated conductive section bent into a semienclosed configuration with its two ends separated from one another by a distance which is small compared to the developed length of said section, said section being disposed parallel to and separated from said ground plane: a whip section extending perpendicularly to said ground plane from a point within the plane and the enclosure of said semienclosed section in a direction away from the ground plane: a first conductive section connecting a point on the semienclosed section adjacent to one of the ends thereof to the end of said whip which is in the plane of said semienclosed section: a second conductive section connecting a point adjacent to the other end of said semienclosed section to the ground plane, said second conductive section extending perpendicularly to the ground plane: a lumped impedance connected between the ground plane and a termination of the whip within the plane of the semienclosed section: and connections between the two ends of the lead-in and'two points on the semienclosed section.
6. The structure of the last claim 5 wherein the lumped impedance is a capacitor.
7. The structure of claim 5 wherein the lumped impedance is a variable capacitor.
8. An antenna operative to be connected to a transmitter-receiver by a two conductor cable, comprising: a metallic ground plane: an elongated conductor section bent into a semicircular configuration with its two ends slightly separated from one another: a plurality of insulators supporting said semicircular section parallel to the ground plane and separated from it: an elongated whip section extending from a point within the plane of said semicircular section perpendicular to such plane away from the ground plane: a first conductive connecting section joining one end of said semicircular section to the end of the whip within the plane of said semicircular secton: a second conductive connecting section joining the other end of said semicircular section to the ground plane: and connections between the two wires of the lead-in to points on the circular section.
9. An antenna operative to be used in connection with a transmitter-receiver to which it is connected by a two conductor cable, and operative to be disposed in relation to a metallic ground plane which may form a section of a supporting vehicle, comprising: a conductive section bent in a semicircular configuration: a plurality of insulators supporting said semicircular section above and parallel to said ground plane: an elongated Whip section extending from a point within said semicircular section in a direction perpendicular to and away from said ground plane: a first conductive section connecting one end of said semicircular section to the end of the whip which is disposed within the plane enclosed by said semicircular section: a second conductive connecting section adjoining the other end of said circular section to the ground plane: a capacitor connected between the ground plane and the end of the whip which is within the plane of said semicircular section: and connections between the ends of 3,151,328 9/1964 Boyer 343744 3,235,871 2/1966 Smith et al. 343-872 FOREIGN PATENTS 938,921 2/ 1956 Germany.
OTHER REFERENCES Boyer, Hula-Hoop Antennas, ElectronicsJanuary 11, 1963. Pages 44-46 relied on.
15 HERMAN KARL SAALBACH, Primary Examiner.
R. F. HUNT, Assistant Examiner.