US3235868A

US3235868A - Zig-zag uhf antenna with four square diamond-shaped portions and quarter wave stubs

Info

Publication number: US3235868A
Application number: US222050A
Authority: US
Inventors: Donald H Wells
Original assignee: ANTENNACRAFT CO
Current assignee: ANTENNACRAFT CO
Priority date: 1962-09-07
Filing date: 1962-09-07
Publication date: 1966-02-15
Anticipated expiration: 1983-02-15

Description

Feb. 15, 1966 D. H. WELLS 3,235,868

ZIG-ZAG UHF ANTENNA WITH FOUR SQUARE DIAMOND-SHAPED PORTIONS AND QUARTER WAVE STUBS Filed Sept. 7, 1962 l VHF ANTENNA IN VENTOR fimaZd/Z 772149 ATTORNEYS United States Patent Iowa Filed Sept. 7, 1962, Ser. No. 222,050 2 Claims. (Cl. 343-727) This invention relates to antennas and more particularly to an ultra high frequency driven element systems which may be coupled directly to a very high frequency antenna system with little or no loss.

In the television antenna art it is desirable to have an antenna system which will function over several bands of frequencies. These bands are in what is commonly termed the very high frequency or VHF range with a low band (channels 2 to 6) covering from 45 to 88 megacycles and a high band (channels 7 to 13) covering from 174 to 216 megacycles, and an ultra high frequency or UHF band (channels 14 to 83) covering from 470 to 890 megacycles.

It has become highly desirable to design an antenna which will receive all of these bands. However, in designing an antenna with this in mind, a problem presents itself, in that a number of driven elements must be used and the driven elements for the VHF bands may adversely affect the operation of the driven elements for the UHF band and likewise the driven elements for the UHF band may adversely affect operation of the driven elements for the VHF band.

It is therefore the object of this invention to provide an antenna system which will function properly over the UHF band and isolate itself so as to not adversely affect the operation of the VHF portion of the antenna system.

Another object of this invention is to provide a UHF- VHF antenna system that will function properly over the UHF band and isolate itself so as to not adversely affect the operation of the VHF portion of the antenna system, and is simple and inexpensive to manufacture.

Another object of this invention is to provide an antenna system which will give substantial gain over the UHF band and isolate itself so as to not adversely affect the operation of the VHF portion of the antenna system.

Another object of this invention is to provide an antenna system which may be added to an existing VHF installation, to provide UHF reception, without impairing the performance of the existing VHF system.

Further objects and advantages of this invention will become apparent from the following detail description taken in conjunction with the accompanying drawing illustrating a preferred embodiment of the invention.

In the drawing:

FIGURE 1 is a diagrammatic view of a UHF drivenelement assembly and isolation network embodying the present invention;

FIGURE 2 is a diagrammatic illustration of the UHF antenna assembly coupled with a single VHF antenna array;

FIGURE 3 is a diagrammatic illustration of the UHF antenna assembly coupled with two VHF antenna arrays; and

FIGURE 4 is a perspective view of the UHF antenna assembly associated with VHF antenna arrays and a collinear reflector system.

Referring to the drawing, wherein like reference characters designate corresponding parts throughout the several figures, the UHF antenna assembly of the present invention is indicated generally by the reference character 10 and comprises a continuous wire array formed basically of a pair of zig-zag shaped conductors 11, 12 to be arranged in a vertical plane and located symmetrically on opposite sides of a medial vertical axis defining the vertical center of the array. The conductors '11, 12 are shaped to provide one

quarter wave legs

13, 14, 15, 16, r17, 18, 19 and 20 and .13, 14, v15, 16', 17, 18, 13 and 20, respectively, along the length thereof, the legs lying at an angle of approximately 45 to the vertical and being alternately inclined outwardly from the center of the assembly and then inwardly toward the center thereby providing angles of about at each bend of the conductors which define the .legs. Since the conductors 11, .12 are symmetrically arranged on opposite sides of the vertical center axis, the conductors provide an array having the appearance of a vertically aligned series of four square diamond-shaped portions. The

inner angles

21, 22, 23, 24 and 25 and 21', 22', 23, 24' and 25' of the conductors 1'1, 12 at the inner ends of the quarter wave legs nearest the vertical center of the array are spaced closely adjacent to each other and are supported by suitable insulators 26 by which the UHF antenna assembly may be mounted on a mast or other suitable support. The outer angles remote from the center are identified by

reference characters

27, 28, 29 and 30 and 27', 2-8', 29' and 30. Parallel one

quarter wave stubs

31, 31 and 32, 32 are secured to the conductors 11, 12 at the upper and

lower end points

21, 21' and 25, 25', respectively, and one quarter wave stubs 33, 3 3' and 34, 34', the outer ends of which are designated 35 project outwardly in opposite directions in aligned pairs from

points

27, 27 and 30, 30.

Points

21, 21' and 23, 23 and 25,25 form the terminal points of the UHF antenna assembly. The signal is coupled from the antenna to the receiver by a transmission line 36 coupled to terminal points 23, 23'. The length of the legs 1-3 to 20 and 13 to 20, to function properly at the UHF band frequency, are approximately seven inches, although this may be varied more or less to favor a higher or lower portion of the band. The length of the quarter wave stubs 31 to 34 and 31 to 34 are six inches to give optimum isolation overthe entire UHF band.

The electrical properties of the antenna system are such that there is high impedance at the frequency across the open ends of one quarter wave stubs 3'1, 31. This reflects back a low impedance to points 21, 21' and continuing on, reflects a high impedance to points 27, 27 A high impedance at the UHF frequency exists at the open ends of stubs 33, 33'. This reflects a low impedance at point 27, 27'. Thus there is an impedance rnis-match created at

point

27, 27 at the UHF frequencies and the UHF currents of one quarter wave stub 33, or antenna legs 14, for example, looking in

direction

35, 27, 21 or 22, 27, 21, will see a low impedance current meeting a high impedance load at point 27 and thus effective isolation is obtained in these directions. The UHF currents flowing from point 2 1 in

direction

21, 27, 35 will see a high impedance current meeting a low impedance load at points 27 and effective isolation at the UHF frequencies is thus obtained in these directions. As point 2 1 is a low impedance point at the UHF frequency, a short circuit or a transmission line to a VHF antenna may be connected to point 21 without detuning the antenna at the UHF frequencies. As the antenna is symmetrical, the above-described electrical properties apply to the lower section of the system.

FIGURE 2 shows the antenna system as it is used in conjunction with a VHF all channel antenna array, indicated by the reference character 37, which is connected to the UHF antenna by transmission line 38 connected at points 21, 21'. An electrical connection 39 is placed across terminal point 25, 25'. At the VHF frequencies the section of the antenna 10 from

terminal points

23, 23 to terminal point 21, 21' appears as a section of trans mission line. At the VHF frequencies, channels 2-6, the section of antenna -10 from

terminal point

23, 26 to

terminal point

25, 25 appears as a one quarter wave shorted stub which reflects back high impedance to terminal point 23, 23' giving effective isolation at these frequencies. At the VHF frequencies, channels 7 to 13, the section of antenna 10 from terminal point 23, 23' to terminal point 25, 25' appears as a three quarter wave shorted stub which reflects a high impedance at

terminal point

23, 23 giving eifective isolation at these frequencies. Thus the antenna system as shown in FIGURE 2 will receive all three television bands with little or no loss at any frequency.

FIGURE 3 shows another arrangement which may be used where it is desirable to obtain additional gain at the VHF frequencies or where it is desirable to orient the

VHF antennas

37 and 40 so as to more effectively receive signals from television stations which are not in line. In this embodiment, the second VHF antenna 40 is coupled to terminal point 25, 25' by transmission line 41.

In using the UHF antenna system as shown in either FIGURES 1, 2 or 3, it may be desirable to use reflectors or directors to increase the gain at the UHF frequency. An example of these reflectors and directors is shown in FIGURE 4 in the form of colinear array elements 42 disposed behind the antenna 10 in alignment with the outer angles 27-30, 27'30.

While but one preferred example of the present invention has been particularly shown and described, it is apparent that various modifications may he made therein within the spirit and scope of the invention, and it is desired, therefore, that only such limitations be placed on the invention as are imposed by the prior art and set forth in the appended claims.

What is claimed is:

*1. An antenna for reception of signals over the ultra high frequency band adapted to be intercoupled with one or more VHF antennas comprising an array to be arranged in a vertical plane including a pair of laterally spaced, vertically extending zig-Zag shaped conductor elements arranged symmetrically on opposite sides of a reference axis at the vertical center of the array, said conductor elements each providing a series of substantially one quarter wave legs for frequencies in the UHF band connected end-to-end and extending in alternately outwardly and inwardly inclining relation between upper and lower connecting terminal points at the top and bottom of the conductor elements for connection to at least one VHF antenna, the conductor elements defining a vertically aligned series of four square diamond-shaped portions wherein the angles of said zig-zag conduct-or element nearest the reference axis are spaced close together, said pair of conductor elements having outlet terminal points at a pair of corresponding angles thereof located substantially midway of the height thereof, quarter Wa've stub means for UHF frequencies connected to said connecting terminal points and to points on said conductor elements spaced one section inwardly from said connecting terminal points to effectively isolate the array with respect to frequencies over the UHF band and cause the array to appear as a section of transmission line .to frequencies over the VHF band.

2. An antenna for reception of signals over the ultra high frequency band adapted to be intercoupled with one or more VHF antennas comprising an array to be arranged in a vertical plane including a pair of laterally spaced, vertically extending zig-zag shaped conductor elements arranged symmetrically on opposite sides of a reference axis at the vertical center of the array, said conductor elements each providing a series of substantially one quarter wave legs for frequencies in the UHF band connected end-to-end and extending in alternately outwardly and inwardly inclining relation between upper and lower connecting terminal points at the top and bottom of the conductor elements for connection to at least one VHF antenna, the conductor elements defining a vertically aligned series of four square diamond-shaped portions wherein the angles of said Zig-zag conductor element nearest the reference axis are spaced close together, said pairof conductor elements having outlet terminal points at a pair of corresponding angles thereof located substantially midway of the height thereof, parallel quarter wave stub pairs connected to said .upper and lower connecting terminal points and colinear quarter wave stu b elements connected to angles of said conductors spaced one leg from said connecting terminal points reflecting a short circuit at said connecting points toward said output terminal points and impedance mismatch at the juncture of said colinear elements with said conductor elements effecting electrical self-isolation of the array at frequencies in the UHF band from any VHF antennas connected thereto and causing the array to appear as a section of transmission line to frequencies in the VHF band.

References Cited by the Examiner UNITED STATES PATENTS 2,856,604 10/ 1958 Wirtan en 343806 2,888,678 5/1959 Weiss 343814 2,918,672 12/1959 Hoverman 343806 2,928,007 D1960 Carpenter 343-806 3,148,371 9/1964 Hoverman 343--806 FOREIGN PATENTS 974,560 2/ 1951 France.

HERMAN SAALBACH, Primary Examiner.

Claims

1. AN ANTENNA FOR RECEPTION OF SIGNALS OVER THE ULTRA HIGH FREQUENCY BAND ADAPTED TO BE INTERCOUPLED WITH ONE OR MORE VHF ANTENNAS COMPRISING AN ARRAY TO BE ARRANGED IN A VERTICAL PLANE INCLUDING A PAIR OF LATERALLY SPACED, VERTICALLY EXTENDING ZIG-ZAG SHAPED CONDUCTOR ELEMENTS ARRANGED SYMMETRICALLY ON OPPOSITE SIDES OF A REFERENCE AXIS AT THE VERTICAL CENTER OF THE ARRAY, SAID CONDUCTOR ELEMENTS EACH PROVIDING A SERIES OF SUBSTANTIALLY ONE QUARTER WAVE LEGS FOR FREQUENCIES IN THE UHF BAND CONNECTED END-TO-END AND EXTENDING IN ALTERNATELY OUTWARDLY AND INWARDLY INCLINING RELATION BETWEEN UPPER AND LOWER CONNECTING TERMINAL POINTS AT THE TOP AND BOTTOM OF THE CONDUCTOR ELEMENTS FOR CONNECTION TO AT LEAST ONE VHF ANTENNA, THE CONDUCTOR ELEMENTS DEFINING A