US3623109A

US3623109A - Yagi-type multiband antenna having one element parasitic in one frequency band and driven in another frequency band

Info

Publication number: US3623109A
Application number: US693381A
Authority: US
Inventors: Klaus Neumann
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-12-26
Filing date: 1967-12-26
Publication date: 1971-11-23
Anticipated expiration: 1988-11-23

Abstract

A Yagi-type multiband antenna including a driven element, a director and a reflector as parasitic elements in which a feeder between one of the parasitic elements and the transmitter may be switched on for making this one parasitic element operable as driven element of a two-element antenna system.

Description

United States Patent [72] Inventor Klaus Neumann 2,703,840 3/1955 Carmichael 343/832 Am Klosterberg13,6 67 St., Ittgbert (Saar), 2,268,640 1/1942 Brown 343/819 66mm 3.175.219 3/1965 Wernick et a1. 343/815 X [21] Appl. No. 693,381 3,176,298 3/1965 Nettles 343/722 Filed 1967 FOREIGN PATENTS [451 Paemed "M33197! 906,636 9/1962 Great Britain 343/749 OTHER REFERENCES [54] YAGl-TYPE MULTIBAND ANTENNA HAVING NE Mitchell, R. H., Three-Band Interlaced Beams," CQ,

ELEMENT PARASITIC IN ONE FREQUENCY Nov., 1968, PP- 102- 103, 130, 148 BAND AND DRIVEN lN ANOTHER FREQUENCY A.R.R.L., Compact 3-Band Parasitic Beam," The BAND A.R.R.L. Antenna Book, Chapt. 12, pp. 272- 274, The Amer- 3 Claims, 1 Drawing Fig. ican Radio Relay League, lnc., 1960 [52] US. Cl 343/722, Primary Examiner-Herman Karl Saalbach 34 /72 3/8l5, 34 I 43/8 2, 34 /376 Assislanl Examiner-Wm. H. Punter [51] Int. Cl H0lq 21/12, Azmmey-John J. Dennemeyer "HOIq 21/30 [50] Field of Search 343/722-730,

315-3 9 335-337 7 749-752, ABSTRACT: A Yagi-type multiband antenna including a 700 TV, 332 driven element, a director and a reflector as parasitic elements in which a feeder between one of the parasitic elements and [56] References Cited the transmitter may be switched on for making this one UNITED STATES PATENTS parasitic element operable as driven element of a two-element 2,640,933 6/1953 Spindler 343/832 x amen System- [6 12 9 DE 9 B 3 0 A OJZSX, 4

A -mzst, 5 1 /7 2 10 77 YAGI-TYPE MULTHBAND ANTENNA HAVING ONE ELEMENT PARASHTKC IN ONE FREQUENCY BAND AND DRIVEN TN ANOTHER FREQUENCY BAND The invention relates to a Yagi-type multiband antenna having at least two parasitic elements for different resonance frequencies for which the resonance is customarily produced by inserting different wave traps inside the elements. As a rule, one does not employ a greater number than three frequencies and these frequencies have a maximum magnitude proportion of about 1:2. If one employs for example a three-element antenna it would constitute only a compromise arrangement in relation to its antenna gain because the spacings between the elements can be designed at best only for one resonance frequency. This arrangement is therefore frequently improved by inserting a separate reflector for the highest resonance frequency.

It is naturally also possible to provide additional driven elements. For this purpose the available length of the antenna boom is always important and this in turn depends on the spacing reflector-director for the lowest resonance frequency. This spacing is on the average about 0.25-0.35 wavelength A.

It is an object of the invention to provide a Yagi-type multiband antenna having at least two parasitic elements without requiring an extension of the antenna boom and without additional driven elements to make this antenna resonant for additional transmitted or received frequencies. Accordingly it is proposed that at least one parasitic element may be operated as driven element for an additional resonance frequency associated with the distance between this particular element and a second parasitic element while the feeder of the former driven element is disconnected. The invention makes use of an element spacing between parasitic elements which has not been used so far and provides thereby without extension of the antenna boom and without additional driven elements a new antenna system which is operated at the particular additional resonance frequency for which the available element spacing promises an optimum antenna gain.

Since the element spacing between two parasitic elements is usually larger than the distance from one of these elements to the driven element for the original frequencies, the additional resonance frequency will in most instances be lower than the frequency for which the multiband antenna was originally designed. This is the case for example when-starting from a three element antenna-the two outer parasitic elements may be operated as a two-element antenna. Thus especially for a frequency which is lower by a harmonic interval than the lowest frequency of the three element arrangement with a 0.25 parasitic element spacing, a combination driven element-director with about 0.125 A offers an optimum gain. One should choose a two-element arrangement as driven elementreflector as soon as this distance lies-between 0.15 to 0.2 A.

It will be understood that the elements used for a two-element arrangement are made resonant for the additional lower resonance frequency. This is accomplished in the simplest manner by an actual or an electrical extension of the elements with the addition of new wave traps for the lowest resonance frequency of the three element arrangement, but there are also other equivalent means which come within the scope of this invention.

it is also important to make sure that the parasitic element which is used as driven element in the two-element arrangement and which is appropriately fed over a y-rnatch, is not damped or detuned by matching devices or the like in its function as reflector or director for the other frequencies of the three-element arrangement due to the feeder. The feeder of the parasitic element which is inserted as driven eiement according to the invention, is therefore appropriately designed for a short-circuiting at the feed point, which is also true for a parasitic element, which is split for feeding purposes,

The objects and advantages of the multiband antenna according to the invention will become more apparent from the following detailed description in combination with the accompanying drawing showing an embodiment of the invention for purposes of illustration.

in the drawing the invention is illustrated on the basis of a three-element antenna. The three elements consist of the driven element 1 having a driven element length S,,,, of the reflector 2 having a reflector length R and of the director 3 having a director length D,,,. The element spacings A are 0.125 A. The three elements are fixed to a horizontal antenna boom 4 so that the direction of the main lobe is in the direction of arrow B.

The three-element multiband antenna is assumed to be tuned for the 20m amateur band for a resonance frequency of l4l50 kHz. Normally the three elements are made resonant for additional frequencies by inserting wave traps in the illuswave traps. In the interest of a tion these additional wave traps are not illustrated and the three-element antenna shown is resonant only for the given frequency.

According to the invention the large spacing A between the reflector 2 and the director 3 is employed to obtain an additional lower resonance frequency equivalent A2 without requiring an extension of the antenna boom 4. For this purpose one of the

parasitic elements

2 and 3, in the embodiment shown the reflector 2, is employed as a driving element in that a coaxial feeder 6 is connected to it for the lower frequency and this is done most appropriately over the illustrate -y-match since the reflector 2 is normally a straight through pipe. To prevent that this additional feeder has harmful effects for the normal three element operation this feeder may be short-circuited by means of a switch 7 in the feed point.

During normal operation the feeder 5 leading to the driving element 1 is connected through a changeover switch 13 to the transmitter 14. in the other switch position the transmitter 14 operates on the parasitic element 2 with a frequency which offers for the fixed spacing A to the other parasitic element 3 an optimum gain.

In the two-element operation according to the invention employing the reflector 2 as driving element the director 3 becomes the director. The driving element 1 does not interfere because it is out of resonance. For the additional frequency of the two-element operation the spacings R and D of the two

elements

2 and 3 are not resonant. The new frequency is derived from the element spacing A when this spacing is equated with the value 0.125 72 which is favorable for a driving element-director system. In the illustrated example an additional lower resonance frequency of about 7075 kHz. is ob tained for which the thus obtained driving element 2 as well as the director 3 must be made resonant by extensions to the dimensions 8,, and D respectively. To provide this several possibilities'exist. The simplest one is to bring the element lengths to the resonance lengths S and D respectively by insertion of wave traps 8 for the element 3 and wave traps 10 for the element 2. In this case these elements would have to become approximately twice as long as the original length D and R for the basic three-element configuration for the 20 meter band. For this reason it seams appropriate for mechanical reasons to electrically extend at least in part the element length for the two element operation by

inductance coils

9 and 1! respectively.

it is obvious that the two element arrangement for 7075 kHz. or the 40m-band can be made resonant for additional adjacent frequency ranges by inserting additional wave traps or by equivalent means.

What is claimed is:

l. A Yagi-type multiband antenna comprising at least two parasitic elements and one driven clement adapted to operate at one resonance frequency. and an electrical switch, at least one of said parasitic elements being controlled by said switch for operation in one switch condition as a parasitic element at said one resonance frequency and for operation in the other switch condition as a driven element at an additional resonance frequency. the fixed spacing between the drivable parasitic element and at least one remaining parasitic element being such as to effect optimum antenna gain at said additional resonance frequency.

2. A Yagi-type multiband antenna comprising:

A. first and second parasitic elements each tuned for different resonance frequencies,

B. one driven element, said first parasitic element being parasitic at one frequency and in addition being operable as a driven element at a second frequency, and

C. switching means selectively operable to make electrical connections to the three elements to connect said driven element and said first and second parasitic elements to act as a three-element antenna at one resonant frequency or alternatively to connect said first parasitic element for operation as a driven element to form, in cooperation with the second said parasitic element. a two-element antenna at a second resonant frequency. said first parasitic element being of such length and construction as to reflect and reinforce the wave radiated by the one driven element without substantially changing the phase of the radiated wave 3. A Yagi-type multiband antenna according to claim 2, wherein the feeder leading to said drivable parasitic element may be short circuited in the feed point.

t i i i

Claims

1. A Yagi-type multiband antenna comprising at least two parasitic elements and one driven element adapted to operate at one resonance frequency, and an electrical switch, at least one of said parasitic elements being controlled by said switch for operation in one switch condition as a parasitic element at said one resonance frequency and for operation in the other switch condition as a driven element at an additional resonance frequency, the fixed spacing between the drivable parasitic element and at least one remaining parasitic element being such as to effect optimum antenna gain at said additional resonance frequency.

2. A Yagi-type multiband antenna comprising: A. first and second parasitic elements each tuned for different resonance frequencies, B. one driven element, said first parasitic element being parasitic at one frequency and in addition being operable as a driven element at a second frequency, and C. switching means selectively operable to make electrical connections to the three elements to connect said driven element and said first and second parasitic elements to act as a three-element antenna at one resonant frequency or alternatively to connect said first parasitic element for operation as a driven element to form, in cooperation with the second said parasitic element, a two-element antenna at a second resonant frequency, said first parasitic element being of such length and construction as to reflect and reinforce the wave radiated by the one driven element without substantially changing the phase of the radiated wave.

3. A Yagi-type multiband antenna according to claim 2, wherein the feeder leading to said drivable parasitic element may be short-circuited in the feed point.