US 3745581 A
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Description (OCR text may contain errors)
DUAL BAND FOLDING ANTENNA BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to folding antenna structures and in particular to a dual band, folding television antenna wherein the antenna elements also form a part of the folding mechanism.
2. Description of the Prior Art Various forms of folding antenna structures have been proposed and typically employ either a plurality of antenna elements which must be individually extended and collapsed by hand or are provided with various linkages to facilitate extending and retracting the antenna elements. It is further typicalthat these folding antenna structures are adapted to receive a single band of radio frequency signals.
SUMMARY OF THE INVENTION The invention in its broader aspects is a* folding antenna structure adapted to receive radio frequency signals, distributed over two distinct and separate frequency bands, typically in the VHF and UHF television bands. The antenna elements of themselves comprise a major portion of the antenna folding mechanism. To this end, the antenna structure comprises first and second elongated booms which are disposed in adjacent, parallel relationship, and means coupling the booms together for relative sliding movement. A first antenna element which is adapted to receive a first band of radio frequency signals is pivotably coupled to the first boom and a second antenna element adapted to receive a second band of radio frequency signals is pivotably coupled between the second boom and the first antenna element between the ends thereof. Relative movement of one boom with respect to the other effects extension and retraction of both the first and second antenna elements between a retracted and a fully or partially extended position.
It is therefore an object of the invention to provide a folding antenna structure adapted to receive two separate and distinct bands of radio frequency signals.
It is another object of the invention to provide such an antenna structure wherein the antenna elements form a major portion of the antenna folding structure.
It is still another object of the invention to provide a folding antenna wherein the extension of the elements thereof can be controlled toeffect tuning of the antenna for optimum reception of predetermined ones of the frequencies in the radio frequency bands.
It is still another object of the invention to provide a folding antenna structure which includes means for positively locking the elements of the antenna structure in an extended or retracted position.
It is yet another object of the invention to provide a folding antenna structure which is economical to produce.
BRIEF DESCRIPTION OF THE DRAWINGS I The above-mentioned and other features and objects of this invention and the manner of obtaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a fragmentary perspective view of a folding antenna in accordance with the invention shown in its retracted position;
FIG. 2 is a perspective view of the full antenna structure shown in an extended position;
FIG. 3 is a fragmentary perspective view showing details of the boom-coupling means; and
FIG. 4 is a side plan view of the antenna structure.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings there is illustrated a dual band, folding antenna 10 which comprises a first elongated boom 12 having a rectangular cross-section. A plurality of spaced coupling elements 14 are fixedly secured to boom 12 with suitable rivets or threaded fasteners as at 16 (FIG. 3). Elements 14 are preferably made of a dielectric material and include a channel portion 18 having a rectangular notch 20 therein and a cap portion 22 which is secured to the upper ends of element 18 closing notch 20.
A second elongated boom 26 has a cross-section complementary to the cross-section of notches 20 in elements 14 and is slidably received therein in parallel spaced-apart relationship to first boom 12. By reason of this sliding coupling, lower boom 12 can be moved longitudinally with respect'to boom 26 whereby coupling elements 14 will be caused to move as indicated by arrow 28 from the solid line positions to the dotted line positions as at 14a as shown in FlGS. 2 and 4.
A plurality of hinge blocks 30 are fixedly secured to second boom 26 in longitudinally spaced-apart relationship by means of suitable rivets or. threaded fasteners as at 32. Each hinge block 30 is provided with a pair of outwardly extending wing portions 33 to each of which is pivotably coupled a suitable antenna element 34 by means of a threaded fastener 36. While only six antenna elements 34 are shown, the antenna elements 34 are conventional dipole elements and may vary in number and be arranged in any suitable array and adapted to receive radio frequency signals of a first predetermined radio frequency band typically the VHF television band. Preferably, the antenna elements 34 are provided in pairs and the array is laterally symmetrical with respect to first boom 12.
A plurality of second antenna elements 38 are provided having one end thereof pivotably and electrically coupled to elements 34 at a point between the ends of the latter, again, by means of suitable threaded fasteners as at 40. The opposite ends of second elements 38 are pivotably connected to but electrically isolated from coupling elements 14, preferably by means of threaded fasteners 41 which are also used to secure the cap 22 to channel portion 18' of the coupling elements 14. It can be observed that antenna elements 38 are provided in pairs and thateach antenna element is itself a dipole. Each of antenna elements 38 is of the same length and the array is adapted to receive radio frequency signals in a second radio frequency band different from the first mentioned radio frequency band, the second band typically being the UI-IF television band.
With the antenna assembly 10 in the position as illustrated in FIG. 1, it will now be apparent that as the first boom 12 is moved to the left as indicated by arrows 28 with respect to boom 26, coupling elements 14 will also move to the left as indicated by arrows 42. Correspondingly, the movement of the elements 14 will cause the 3. ends of second antenna elements 38 affixed thereto to move leftwardly (as viewed in FIGS. 1 and 2) and, correspondingly, because of the pivotable connection between second antenna elements 38 and first antenna elements 34, both antenna elements 38 and 34 will be caused to pivot outwardly as indicated by arrows 44, 46, respectively. Progressive movement of first boom 12 with respect to scond boom 26 will therefore result in progressive extension of antenna elements 34, and second antenna elements 38 from their retracted position as illustrated in FIG. 1 to an intermediate extended position as indicated in solid lines of FIG. 2 and, ultimately, to a fully extended position as indicated in dotted lines in FIG. 2.
To provide a means for mounting the antenna on a suitable supporting mast (not shown) and also to provide a means for positively locking the antenna in its extended or retracted positions, there are provided first and second U-bolt clamp assemblies 50 and 52 (FIGS. 2 and 3 only). Assembly 50 includes a channel-shaped bracket 54 and U-bolt 56 and is secured in fixed position on second boom 26 in conventional fashion, the bracket 54 receiving boom 26 and the U-bolt 56 passing through holes in both boom 26 and bracket 54 to receive nuts thereon. First boom 12 is provided with a plurality of pairs of holes 58a, 58b, and 580, and clamp assembly 52, like clamp assembly 50, is provided with a bracket 60 and U-bolt 62 which is secured through a selected pair of holes 58a, 58b, or 580. It can now be seen that if clamp assembly 52 is secured to first boom assembly 12 by means of holes 58c, it will be in registry with clamp assembly 50 when antenna elements 34 and 38 are in their partially extended position as indicated in solid lines in FIG. 2. With clamp assemblies 50, 52, thus disposed in registry, a mast (not shown) is received therethrough and the nuts on the U-bolts 56, 62, tightened in conventional manner. Thus the boom assembly is not only positively secured to the mast but also, the first and second boom assemblies 12 and 26, respectively, are positively locked against relative movement. It will further be apparent that if clamp assembly 52 is secured to first boom 12 by means of holes 58a, or 58b, and first boom 12 moved until clamp assembly 52 is again in registry with clamp assembly 50, the clamp assemblies 50, 52, will again provide a means for locking the booms 12 and 14 against relative movement but with antenna elements 34, and 38 in different positions.
To provide the necessary electrical connections between the individual antenna elements 34, 38, there are provided a plurality pf electrical connecting links 66 which extend between each longitudinally adjacent and laterally opposite pair of threaded fasteners 36. Connecting links 66 are made from a suitable stiff and electrically conductive wire and the ends thereof are formed as by bending to have eyelets as at 68 which are retained beneath the nuts 70 of fasteners 36 and in electrical contact with antenna elements 34. Additional connecting links 66, particularly shown as 33 in FIG. 2, may be used in combination with additional dipoles 34, 38 in the same manner as shown for the other dipoles and links if a larger array is desired.
An appropriate pair of threaded fasteners 41 extend downwardly through one coupling element 14 and are fitted with suitable nuts 72 to provide a means for electrically connecting the ends of a transmission line 74 (see FIG. 2) to the antenna elements in conventional manner.
From the above descriptions of the operations of the folding antenna assembly, it is now further apparent that the first and second booms l2 and 26 can be moved relative to one another to any desired extent thereby effecting movement or extension of antenna elements 34 and 38 to any desired degree. The degree of extension of antenna elements 34 and 38, and correspondingly the effective electrical dipole length of the elements 34 and 38 can also be controlled by selectively controlling the degree of relative movement of the booms 12 and 26. Further, since the receiving efficiency of the antenna for a particular frequency will be affected by the effective electrical dipole length of the antenna elements 34 or 38, the selective adjustment of the positions of the boom 12 and 26 provides a means for tuning the antenna for maximum receiving efficiency at a particular, predetermined frequency. For example, the antenna assembly can be selectively turned to a particular frequency to receive a preferred or a weak signal and simultaneously is capable of receiving the entire band of frequencies for which it is designed. l
The antenna elements 34 and 38 themselves form a major portion of the folding linkage or folding mechanism of the invention thereby obviating the need for extraneous linkages and equipment.
In a working embodiment of the invention, the following dimensions were used:
second elements 38, length 4% inches, diameter )4:
first boom 12, 1 inch square second boom 26, 1 inch square connecting links 66, length 10% inches, diameter 6 inch While there have been described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.
What is claimed is:
1. For use in a dual band forming antenna, a structure comprising first and second elongated booms disposed in adjacent, parallel relationship, means coupling said booms together for relative longitudinal movement, a first pair of antenna elements disposed in spaced endto-end relationship adapted to receive a first band of radio frequency signals, second means for pivotably coupling an end of each of said first element mutually insulated from each other to said first boom for movement between retracted and extended positions, a second pair of antenna elements each shorter than a first antenna element adapted to receive a second band of radio frequency signals, each said second element having said one end thereof pivotably and electrically coupled to a respective one of said first elements between the ends and equidistant from the pivoted end thereof and its opposite end pivotably coupled to said second boom for movement between retracted and extended positions, the opposite ends of said second elements being end-to-end mutually insulated from each other and said second boom, whereby movement of one of said booms with respect to the other produces simultaneous movement of said first and said second antenna elements between said retracted and extended positions, and means for electrically connecting a transmission line to said first and second elements.
2. The combination of claim 1 wherein said first means includes a collar of dielectric material, said second antenna element being connected at said opposite end to said collar.
3. The combination of claim 2 wherein said collar is fixedly secured to said second boom and includes an opening extending therethrough, said first boom being slidably received in said opening.
4. The combination of claim 1 wherein said second means includes a hinge block of dielectric material fixedly secured to said first boom.
5. The combination of claim l-wherein said first band of frequencies is the VHF television band and said second band of frequencies is the UHF television band.
6. The combination of claim 1 further comprising means for locking said first and second booms against relative movement.
7. The combination of claim 6 wherein said locking means includes a first U-bolt clamp fixedly secured to one of said booms and a second U-bolt clamp selectively, movably secured to the other of said first and second booms.
8. The combination of claim 7 wherein said first and second U-bolt clamps are further adapted to clampingly engage an antenna mast. I
9. The combination of claim 8 wherein said boom includes a plurality of pairs of'holestherein in longitudinally spaced-apart relationship, said second clamp being received in one pair of said holes and disposed in registry with said first clamp when said first element is in said extended position and secured in a different pair I of said holes and in registry with said first clamp when said antenna element is in said retracted position, re-
10. The combination of claim 5 wherein there are pluarlity of pairs of said first elements spacedlongitudinally of said booms arranged in a first laterally symmetrical antenna array and a plurality of pairs of said second elements arranged in a second laterally symmetrical antenna array, said first and second elements being elongated dipoles, said first elements being longer than said second elements, transmission line connecting means including a plurality of'electrical connecting links each of which is connected between the proximal end of a predetermined one of said first elements and the proximal end of the laterally opposite one of the next longitudinally adjacent pair of said first elements.
11. Th'eantenna of claim 10 wherein said first antenna elements have a length at least two times the length of said second elements.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Paten No- 3.745.581 Dated July 10-. 1972 Inventorw$ Lynn L. Lockwood It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as"s hown'below:
Column 2, Line 48, before "having" insert --each---, Column 3, Line 52, change "pf" to --of---;
In The Claims.
Claim 1, Column 4, Line 1, change "forming" to --folding--,
Claim 10, Column 6, Line 2, change "plurai:ity" to plurality-.
Signed and sealed this l2th da y of February 1974.
Attesting Officer Ci. MARSHALL DANN Commissioner of Patents FORM P0405!) (10-69) uscMM.Dc 503154,, I 0.5. wvnunrn mum's mac: 1m o-uo-na