CA2196667A1 - Nonsquinting end-fed quadrifilar helical antenna - Google Patents
Nonsquinting end-fed quadrifilar helical antennaInfo
- Publication number
- CA2196667A1 CA2196667A1 CA002196667A CA2196667A CA2196667A1 CA 2196667 A1 CA2196667 A1 CA 2196667A1 CA 002196667 A CA002196667 A CA 002196667A CA 2196667 A CA2196667 A CA 2196667A CA 2196667 A1 CA2196667 A1 CA 2196667A1
- Authority
- CA
- Canada
- Prior art keywords
- nonsquinting
- helical antenna
- antenna
- fed
- helix
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q11/00—Electrically-long antennas having dimensions more than twice the shortest operating wavelength and consisting of conductive active radiating elements
- H01Q11/02—Non-resonant antennas, e.g. travelling-wave antenna
- H01Q11/08—Helical antennas
Abstract
Each conductor of the antenna is fed with a successively delayed phase representation of the input signal to optimize transmission characteristics.
Each of the conductors is separated into a number Z of discrete conductor portions by Z-1 capacitive discontinuities. The addition of the capacitive discontinuities results in the formation of an antenna array. The end result of the antenna array is a quadrifilar helical antenna which is nonsquinting (radiates in a given direction independently of frequency).
Each of the conductors is separated into a number Z of discrete conductor portions by Z-1 capacitive discontinuities. The addition of the capacitive discontinuities results in the formation of an antenna array. The end result of the antenna array is a quadrifilar helical antenna which is nonsquinting (radiates in a given direction independently of frequency).
Description
~ WO96/07216 ' , 2 1 9 6 6 6 7 r~
NONSUJLNllN~ END-FED QUADRIFILAR ~E~ICAB A~TENNA
BACKGROUND OF T~E INVENT~ON
(l) Field of the invention The present invention relates to helical antennas.
More particularly the invention pertains to end-fed nons~ui~ting guadrifilar helical antennas. This application:is related to ~nr~n~i n~ ~application Attorney Docket No. W.E. ~8,520, filed concurrently, which is hereby incorporated by reference.
NONSUJLNllN~ END-FED QUADRIFILAR ~E~ICAB A~TENNA
BACKGROUND OF T~E INVENT~ON
(l) Field of the invention The present invention relates to helical antennas.
More particularly the invention pertains to end-fed nons~ui~ting guadrifilar helical antennas. This application:is related to ~nr~n~i n~ ~application Attorney Docket No. W.E. ~8,520, filed concurrently, which is hereby incorporated by reference.
(2) Description of the related art In general ~Lelical antennas are widely known. They typically comprise single or multiple conductors wound around a mast into a helical shape. =Each conductor has a feed and~a far end, with one end designated as a feed end to accept antenna input. The far e~d may be left as an l~ open circuit, or~in the case of multiple cnn~nrtnr6 (multifilar) the far ends may be ~nnn~t~ (short circuited) together.
When the diameter of a helical antenna is small in comparison to the wavelength of the signal to be tranemittea, the transmitted wave radiates in a radial mode in an omnidirectional pattern (when the phase on the helices i8 set to do so). Energy travels with negligible SllBSTITUTE SHEET (RULE 26) WO96/07216 2 1 9 6 6 6 7 J ~ ,r'~
radiation from the feed end the length of.the helix to the far end, is reflected from either a short or open cir~uit and radiates on return toward the feed end. The radial mode antenna is most readily used as a backfire device, meaning the omnidirectional pattern tends to be directed toward the end that radiates first. However, by adju6ting the pitch of the helices, the beam may be scanned through wide ang~es all the way from the normal to endfire (away from the feed end in the instant invention) direction.
The pointing angle of the radiation pattern of an end-fed antenna changes with frequency (squints) with the higher (and lower) frequencies ra~;At;nr away from the feed end at an angle of ~0 (radians) from the midband frequency F, where (l) ~o = ~F/F
with ~F equal to the difference in xert~ between the midband frequency F and the higher (or lower) frequency.
This squint with frequency is undesirable as it tends to result in beams pointing in different directions (one for transmit, one for receive~ when a helical antenna is used in a fully duplexed wideband communication system.
SUMMARY OF THE INVE~TION
~ rC~r~;nrly, it ig a general purpose and object of the present invention to provide an improved quadrifilar ~1; rAl antenna. It is a further object that the ~ WO96/07216 2 1 9 6 6 6 7 r~ - ?
quadrifilar helical antenna provide specific radiation patterns within specific frequency ranges.
The features and advantages of the present invention include even power distribution along the entire length of the antenna resulting in increased power output for a given input, beampointing independent of the ire~uency to be transmitted, a narrower beam with higher gain allowing more energy to be transmitted in~the direction of its ;ntPn~P~ receiver resulting in more~efficient power transmission, and allowing the 6ame antenna to exhibit optimum gain characteristics on a (different) receiving frequency without retuning or adjustment when switching between tr~nr~;t and receive modes.
These obiects of the present invention are ac~o~pli.qhPfl by providing an end-fed quadrifilar helical antenna. Each conductor of the antenna is fed with a 6uccessively delayed phase representation of the input signal to optimize tran6mission characteristics. Each of the conductors is separated into a number Z of discrete r~nrlnrtnr portions by Z-1 capacitive disco~tinuities. The addition of the capacitive dis~nt;nn;ties results in the formation of an antenna array. The end result of the antenna array is a quadrifilar helical antenna which is nonsquinting and ha6 the further features and advantages as described above.
WO96/07~16 2 1 9 6 6 6 7 P~ IIL~ _ 9. 9 ~
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a typical single r~nrt~r helical antenna.
Figure 2a illustrates the normal radiation mode of a typical helical antenna.
Figure 2b illustrates the axial radiation mode of a typical helical antenna. ~ :
Figure 2c illustrates the radial radiation mode of a typical helical antenna.
Figure 3 illustrates the geometry of a typical helical antenna.
Figure 4a illustrates a top view of a r~uadrifilar h~l;r~l antenna of the present inve~tion.
Eigure 4b_il1ustrates a side view of a r~uadrifilar helical antenna of the presen~ invention.
Figure 4c illustrates a representation of an unwound r~uadrifilar helical antenna ~f the present invention.:
Figure 4d illustrates an isometric view of a conductor of a typical helical antenna.
Figure 4e illustrates a capacitive discontinuity between the conductive portions of a r~uadrifilar helical antenna of the present invention.
Figure 4f illustrates an unwound ~ua~drifilar helical antenna in embodiment of the present invention.
Figure 5 illustrates a ~ n pattern of the antenna of the present invention with an input at 1545 ~ Wo96107216 2 1 q 6 6 6 7 r~ E[9!o Mhz Figure 6 illustrates a radiation pattern of the antenna of the present invention with an input at 1660 Mhz Figure 7 illustrates a current distribution along the antenna of the present invention with an input at 1545 Mhz.
Figure 8 illustrates the phase of the current along the length of the antenna of the present invention with an input at 1545 Mhz.
Figure 5 illustrates an inpu~ feed phase distribution network to the quadrifilar helical antenna of the present invention.
DETAILED DESCRIPTION
An antenna is usually defined as the structure associated with the region of transition between a guided wave and a free space wave, and vice versa. On tr~n~ sion, an antenna accepts energy from a transmission line and radiates it into space, and on reception, an antenna gathers energy from an ;n~ n~ wave and transmits it down a tr~n~ n line.
~ Fig. 1 illustrates a typical single conductor helical antenna (helix). A helix can radiate in many modes. A
helix comprises a single conductor o~ multiple conductors wound into a helical shape. As energy is fed into the WO96/07216 ' ~ ' 2 1 9 6 6 6 7 . ~ s . ~
feed end of a rrn~llrt~r, the conductor acts as a transmission line to conduct the energy to the far end where it i8 then reflected back toward the feed end. Upon initial reflection, the conductor then acts as an antenna to radiate the energy from the conductor. The amount of radiation per unit length of conductor decreases exponential as the energy i9 conducted away from the reflective ~far) end In other words, most of the radiation is emitted from the~far end o~ the antenna after reflection while very little is emitted from the near (or feed) end.
The normal mode of r~ t;nn of a helica~ antenna, illustrated in Fig. 2a, yield~ rr~ t]~n broadside (normal) to the helix axi~ and occurs when the helix~
diameter is small with respec~ to transmitted wavelength.
The axial mode, illustrated in Fig. 2~, provides maximum radiation along the helix axis and occurs when the helix circumference is of the order of one wavelength.
The radial mode, illustrated in Fig. 2c, results in a conical beam pattern and occurs when the circumference of the helix is much smaller than a wavelength. The angle of radiation 0 of the beam pattern of a typical helical antenna is a function of the number of turns per unit length of the r~n~nrt~r of the helix for a given freriuency~
The helical anterna parameter~ are illustrated in Fig. 3 and are defined as follows: ~
~ W0 96r~72l6 2 1 9 6 6 6 7 ~ JS - ?
D = diameter of helix (center to center) C = circumference of helix = ~D
S = spacing between turns (center to center) = pitch angle = tan~1(S/~D) N = number of turns L = axial length of helix = NS
d = diameter of helix cnn~llrtnr l = length of one turn = [(~D)~ + Sl]l/Z
Further background material may be found in Antenna Engineering ~andbook, Second Edition, McGraw-~ill, 1984, especial~y chapter 13, entitled "~elical Ant~nn~r", whose subject matter is hereby incorporated by reference.
The preferred : ~n~;m~nt for a nonsquinting scanning helix is illustrated in Fig. 4. Figure 4a illustrates a top view of the mast 412 with each of the four conductors 414, 416, 418 and 420 of the quadrifilar helix equally distributed about the magt. Additionally, each nrn~llrtnr is separated in phase by 90 degrees, with the first nnn~llrtnr 414~at 0 degreeg, gecond,ccnductor 416 at -90 degrees, third conductor 418 at -180 degrees and fourth nnn~llrtr,r 420 at -270 degrees.
Fig. 4b illustrates a two dimensional representation of the 4 cnn~n~trrs 414, 416, 418, 420 used in the preferred embodiment wound afflund mast 412. In the preferred embodiment, the optimum frequency of the antenna is within the L band. This optimal configuration is achieved by using 4-6 inches per turn and a scan angle WO96/07216 2 1 9 6 6 67 l~ 9!'~ ~
between 15 and 58 degrees. Other freriuency ranges are achievable those skilled in the art through minor adjustments.
Fig. 4c illustrates the 4 rnn~nrtnr~ 414, 416, 418, 420 in a functional manner as if they were straightened.
In the preferred embodiment, capacitors 422a-d, 424a-d, 426a-d and 428a-d are placed eriuidistant along each conductor 414, 416, 418 a~d 420, effectively separating each conductor into 4 eriual portions. In the preferred embodiment, the length of each portion is 7.5 inches and the values of each capacitor are erluivalent at 1.5 pF.
The number of cnn~l-rt~r portions may vary from 2 to Z, where Z i8 a positive whole number. The number of capacitors may vary between 1 and Z-l.
The arrows of Fig. 4c represent energy transmission from one conductor segment to the next, for example~414d to the next segment 414c across capacitive disront;nn;ty 426a. Energy is partially transmitted and partially reflected along each segment. As capacitance~is increased, more energy is applied to the~~ollowing section. When a suitable value is reached, the gain is maximized and er~ual to that of an ant nna without capacitive ~;4rnnt;nll;tie6~ but without the sriui~t The addition of capacitive disrnnt;nll;ties 422a-d acts to separate each of thp~l;r~ into an array of helical antenna elements. As each unbroken element tends to radiate most of its energy at the end closest to~the wog61a7216 ~ 1 96667 P~ e~
h~g;nn;nr; (or point of reflection) of current, breaking up the rnn~llrtors and the adding of capacitive discrntinll;ties to form an array of helical antennas results in a~ antenna array with even power distribution.
An even power distribution provides a more efficient antenna with higher gain that emits more power per unit of input power. ~
Fig. 4d illustrates an isometric view of flat conductor 12. The figure is not drawn to scale as d is lC much greater than h.
Fig. 4e illustrates the capacitive disrrnt;nnity 422a-d of Fig. 4c. Only single discontinuity 422a is referenced for clarity in the following explanation. In the preferred embodiment, all capacitive disrnnt;nllities at one junction are equ-ivalent. ~nn~nctnr 414 is split into at least 2 portions 414a, 414b with a gap 444 between the portions. A dielectric material 442 such as mylar or TPX is then applied as a ~'bridge" over top of and connected to both portions. A r--t~ll;r tape 440 made from, for example, copper or other suitable material, is then used to hold the dielectric to the two portions thus resulting in a capacitive effect between the two portions.
Another embodiment of the present invention incIudes the helix separated into two portions by a capacitive disrrntinnity with the conductor fed by inputs from both ends. The spacing of the capacitive discrnt;nl~;ty in this example is approximately two-thirds the distance from the Wo96107216 ' ' 2 1 9 6 6 6 7 P~
bottom end of the r~n~nrtr,r Fig. 4f illustrates an embodiment for the situation when a r1uadri~ilar helix is separated into two portions (Y
- 2 and N = 4). In this embodiment of the invention, four capacitive discnnt;nn~ties e1ual to 0.3 Pf capacitors 428a-d are used to separate eachrof the four rr~nrt~r8 432, 434, 436 and 438 into two er~ual portions. The feed end accepts the four inputs, with each successive input separated in phase by 90 degrees from the previous input.
The four r~n~lrtors 432, 434, 436 and 438 are r~nn~ct~ at the far end 440 through four ;n~nrtnrs 430a-d, whlch in this embodiment have erluivalent values of 0.03 ~H.
It should be pointed out-that while each separate portion of the helix radiates at an er~uivalent power level and does sr~uint, the overall effect_ior the helix array is for the pattern to be constant at a given angle ~ and thus to be nonsr1uinting.
The angle of propagation ~ for the antenna as a whole iB a function of the sin~l of the phase between the elements and the distance between the windings.
A helix of conductors uninterrupted by capacitive discrnt;nn;ties radiates at an angle proportional to=l/A
(which is er~uivalent to~radiating at an angle proportional to frer1uency), while the antenna of the present invention radiates at an angle independent of frer~uency (or wavelength A) and is thus nonsr1uinting. It does 80 because the array factor of the shorter elements (formed ~ WO96107216 ' ' 2 1 9 6 6 6 7 r~
by the capacitive discontinuities) is fixed in space and dominates. It is fixed in space because there is sufficient phase length in each wrapped helix transmission line to operate as a corporate divider.
Figs. 5 and 6 illustrate the beam elevation pattern of the omnidir~rtir,n~l helix with signal inputs at 1545 and 1660 Mhz respectively. Upon inspection, it is evident that both patterns have a maximum at about 15 degrees above the horizon and are thus nonsr~uinting. The outer pattern is righthand circular polarization and the inner pattern is the cross polarized left hand component.
Figs~. 7 and 8 illustrate current magnitude and phase along the lenyth of the helix when a signal at 1545 Mhz is input to the antenna. Fig. 7 further illustrates local current peaks at elements 15, 30 and 45. Flements 1 - 60 are shown in the plots. It should be noted that for antenna analysis purposes, the entire antenna conductor length is viewed as a number of discrete smaller ~l~mrnt~
(lengths). In this example the thirty inch long antenna is viewed as sixty smaller elements. In this example, if the cr,n~nrtr~ is separated into 4 portions by three uniformly placed capacitive discontinuities, then the capacitors are placed at the fifteenth/ thirtieth and forty-fifth ~l~m~ntc.
The phase difference is introduced by connecting a single feed 910 into a phasing network 900 with a single input 912 and four outputs 914, 916, 918 and 920 as WO96/07216 ' 2 1 9 6 6 6 7 1 ~ c -~ ~
illustrated in ~ig. 9. The signal path 922 f~om the input 910 is isolated and sent through separate tr~nrm;qF.;on lines of predetermined length in order to introduce the proper phase delay in 90 degree increments before connection to each o~_the ~our respective outputs 914, 916, 918 and 920 which are in~turn c~nnPrt~ to the four conductors 414, 416, 418 and 420 of the quadrifilar helix.
It will be understood that when discussing an antenna, its properties are usually describsd with respect to tr~nF~iCc; ~n or r~ t'~n emission However, it is well known from the reciprocity theorem that the directional pattern of a receiving antenna is l~ntir~l to its directional pattern as a transmitting antenna provided that no non-linear devices are used. Thus, no diSt;nrt;~n need be made between the transmitting and recsiving functions of a given antenna in either the claims of the present invention or the general analysis of radiation characteristics However, this does not mean that antenna current=distributions are equivalent on transmission and reception.
It will be further understood that various changes in the details, steps, materials, aLL~ny_msl~t of parts, which have been herein described and illustrated in~order o ~pl~;n the nature of the invsntion, may be made by those skilled in the art within the principle and scope of the invention as expressed in the claims.
When the diameter of a helical antenna is small in comparison to the wavelength of the signal to be tranemittea, the transmitted wave radiates in a radial mode in an omnidirectional pattern (when the phase on the helices i8 set to do so). Energy travels with negligible SllBSTITUTE SHEET (RULE 26) WO96/07216 2 1 9 6 6 6 7 J ~ ,r'~
radiation from the feed end the length of.the helix to the far end, is reflected from either a short or open cir~uit and radiates on return toward the feed end. The radial mode antenna is most readily used as a backfire device, meaning the omnidirectional pattern tends to be directed toward the end that radiates first. However, by adju6ting the pitch of the helices, the beam may be scanned through wide ang~es all the way from the normal to endfire (away from the feed end in the instant invention) direction.
The pointing angle of the radiation pattern of an end-fed antenna changes with frequency (squints) with the higher (and lower) frequencies ra~;At;nr away from the feed end at an angle of ~0 (radians) from the midband frequency F, where (l) ~o = ~F/F
with ~F equal to the difference in xert~ between the midband frequency F and the higher (or lower) frequency.
This squint with frequency is undesirable as it tends to result in beams pointing in different directions (one for transmit, one for receive~ when a helical antenna is used in a fully duplexed wideband communication system.
SUMMARY OF THE INVE~TION
~ rC~r~;nrly, it ig a general purpose and object of the present invention to provide an improved quadrifilar ~1; rAl antenna. It is a further object that the ~ WO96/07216 2 1 9 6 6 6 7 r~ - ?
quadrifilar helical antenna provide specific radiation patterns within specific frequency ranges.
The features and advantages of the present invention include even power distribution along the entire length of the antenna resulting in increased power output for a given input, beampointing independent of the ire~uency to be transmitted, a narrower beam with higher gain allowing more energy to be transmitted in~the direction of its ;ntPn~P~ receiver resulting in more~efficient power transmission, and allowing the 6ame antenna to exhibit optimum gain characteristics on a (different) receiving frequency without retuning or adjustment when switching between tr~nr~;t and receive modes.
These obiects of the present invention are ac~o~pli.qhPfl by providing an end-fed quadrifilar helical antenna. Each conductor of the antenna is fed with a 6uccessively delayed phase representation of the input signal to optimize tran6mission characteristics. Each of the conductors is separated into a number Z of discrete r~nrlnrtnr portions by Z-1 capacitive disco~tinuities. The addition of the capacitive dis~nt;nn;ties results in the formation of an antenna array. The end result of the antenna array is a quadrifilar helical antenna which is nonsquinting and ha6 the further features and advantages as described above.
WO96/07~16 2 1 9 6 6 6 7 P~ IIL~ _ 9. 9 ~
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a typical single r~nrt~r helical antenna.
Figure 2a illustrates the normal radiation mode of a typical helical antenna.
Figure 2b illustrates the axial radiation mode of a typical helical antenna. ~ :
Figure 2c illustrates the radial radiation mode of a typical helical antenna.
Figure 3 illustrates the geometry of a typical helical antenna.
Figure 4a illustrates a top view of a r~uadrifilar h~l;r~l antenna of the present inve~tion.
Eigure 4b_il1ustrates a side view of a r~uadrifilar helical antenna of the presen~ invention.
Figure 4c illustrates a representation of an unwound r~uadrifilar helical antenna ~f the present invention.:
Figure 4d illustrates an isometric view of a conductor of a typical helical antenna.
Figure 4e illustrates a capacitive discontinuity between the conductive portions of a r~uadrifilar helical antenna of the present invention.
Figure 4f illustrates an unwound ~ua~drifilar helical antenna in embodiment of the present invention.
Figure 5 illustrates a ~ n pattern of the antenna of the present invention with an input at 1545 ~ Wo96107216 2 1 q 6 6 6 7 r~ E[9!o Mhz Figure 6 illustrates a radiation pattern of the antenna of the present invention with an input at 1660 Mhz Figure 7 illustrates a current distribution along the antenna of the present invention with an input at 1545 Mhz.
Figure 8 illustrates the phase of the current along the length of the antenna of the present invention with an input at 1545 Mhz.
Figure 5 illustrates an inpu~ feed phase distribution network to the quadrifilar helical antenna of the present invention.
DETAILED DESCRIPTION
An antenna is usually defined as the structure associated with the region of transition between a guided wave and a free space wave, and vice versa. On tr~n~ sion, an antenna accepts energy from a transmission line and radiates it into space, and on reception, an antenna gathers energy from an ;n~ n~ wave and transmits it down a tr~n~ n line.
~ Fig. 1 illustrates a typical single conductor helical antenna (helix). A helix can radiate in many modes. A
helix comprises a single conductor o~ multiple conductors wound into a helical shape. As energy is fed into the WO96/07216 ' ~ ' 2 1 9 6 6 6 7 . ~ s . ~
feed end of a rrn~llrt~r, the conductor acts as a transmission line to conduct the energy to the far end where it i8 then reflected back toward the feed end. Upon initial reflection, the conductor then acts as an antenna to radiate the energy from the conductor. The amount of radiation per unit length of conductor decreases exponential as the energy i9 conducted away from the reflective ~far) end In other words, most of the radiation is emitted from the~far end o~ the antenna after reflection while very little is emitted from the near (or feed) end.
The normal mode of r~ t;nn of a helica~ antenna, illustrated in Fig. 2a, yield~ rr~ t]~n broadside (normal) to the helix axi~ and occurs when the helix~
diameter is small with respec~ to transmitted wavelength.
The axial mode, illustrated in Fig. 2~, provides maximum radiation along the helix axis and occurs when the helix circumference is of the order of one wavelength.
The radial mode, illustrated in Fig. 2c, results in a conical beam pattern and occurs when the circumference of the helix is much smaller than a wavelength. The angle of radiation 0 of the beam pattern of a typical helical antenna is a function of the number of turns per unit length of the r~n~nrt~r of the helix for a given freriuency~
The helical anterna parameter~ are illustrated in Fig. 3 and are defined as follows: ~
~ W0 96r~72l6 2 1 9 6 6 6 7 ~ JS - ?
D = diameter of helix (center to center) C = circumference of helix = ~D
S = spacing between turns (center to center) = pitch angle = tan~1(S/~D) N = number of turns L = axial length of helix = NS
d = diameter of helix cnn~llrtnr l = length of one turn = [(~D)~ + Sl]l/Z
Further background material may be found in Antenna Engineering ~andbook, Second Edition, McGraw-~ill, 1984, especial~y chapter 13, entitled "~elical Ant~nn~r", whose subject matter is hereby incorporated by reference.
The preferred : ~n~;m~nt for a nonsquinting scanning helix is illustrated in Fig. 4. Figure 4a illustrates a top view of the mast 412 with each of the four conductors 414, 416, 418 and 420 of the quadrifilar helix equally distributed about the magt. Additionally, each nrn~llrtnr is separated in phase by 90 degrees, with the first nnn~llrtnr 414~at 0 degreeg, gecond,ccnductor 416 at -90 degrees, third conductor 418 at -180 degrees and fourth nnn~llrtr,r 420 at -270 degrees.
Fig. 4b illustrates a two dimensional representation of the 4 cnn~n~trrs 414, 416, 418, 420 used in the preferred embodiment wound afflund mast 412. In the preferred embodiment, the optimum frequency of the antenna is within the L band. This optimal configuration is achieved by using 4-6 inches per turn and a scan angle WO96/07216 2 1 9 6 6 67 l~ 9!'~ ~
between 15 and 58 degrees. Other freriuency ranges are achievable those skilled in the art through minor adjustments.
Fig. 4c illustrates the 4 rnn~nrtnr~ 414, 416, 418, 420 in a functional manner as if they were straightened.
In the preferred embodiment, capacitors 422a-d, 424a-d, 426a-d and 428a-d are placed eriuidistant along each conductor 414, 416, 418 a~d 420, effectively separating each conductor into 4 eriual portions. In the preferred embodiment, the length of each portion is 7.5 inches and the values of each capacitor are erluivalent at 1.5 pF.
The number of cnn~l-rt~r portions may vary from 2 to Z, where Z i8 a positive whole number. The number of capacitors may vary between 1 and Z-l.
The arrows of Fig. 4c represent energy transmission from one conductor segment to the next, for example~414d to the next segment 414c across capacitive disront;nn;ty 426a. Energy is partially transmitted and partially reflected along each segment. As capacitance~is increased, more energy is applied to the~~ollowing section. When a suitable value is reached, the gain is maximized and er~ual to that of an ant nna without capacitive ~;4rnnt;nll;tie6~ but without the sriui~t The addition of capacitive disrnnt;nll;ties 422a-d acts to separate each of thp~l;r~ into an array of helical antenna elements. As each unbroken element tends to radiate most of its energy at the end closest to~the wog61a7216 ~ 1 96667 P~ e~
h~g;nn;nr; (or point of reflection) of current, breaking up the rnn~llrtors and the adding of capacitive discrntinll;ties to form an array of helical antennas results in a~ antenna array with even power distribution.
An even power distribution provides a more efficient antenna with higher gain that emits more power per unit of input power. ~
Fig. 4d illustrates an isometric view of flat conductor 12. The figure is not drawn to scale as d is lC much greater than h.
Fig. 4e illustrates the capacitive disrrnt;nnity 422a-d of Fig. 4c. Only single discontinuity 422a is referenced for clarity in the following explanation. In the preferred embodiment, all capacitive disrnnt;nllities at one junction are equ-ivalent. ~nn~nctnr 414 is split into at least 2 portions 414a, 414b with a gap 444 between the portions. A dielectric material 442 such as mylar or TPX is then applied as a ~'bridge" over top of and connected to both portions. A r--t~ll;r tape 440 made from, for example, copper or other suitable material, is then used to hold the dielectric to the two portions thus resulting in a capacitive effect between the two portions.
Another embodiment of the present invention incIudes the helix separated into two portions by a capacitive disrrntinnity with the conductor fed by inputs from both ends. The spacing of the capacitive discrnt;nl~;ty in this example is approximately two-thirds the distance from the Wo96107216 ' ' 2 1 9 6 6 6 7 P~
bottom end of the r~n~nrtr,r Fig. 4f illustrates an embodiment for the situation when a r1uadri~ilar helix is separated into two portions (Y
- 2 and N = 4). In this embodiment of the invention, four capacitive discnnt;nn~ties e1ual to 0.3 Pf capacitors 428a-d are used to separate eachrof the four rr~nrt~r8 432, 434, 436 and 438 into two er~ual portions. The feed end accepts the four inputs, with each successive input separated in phase by 90 degrees from the previous input.
The four r~n~lrtors 432, 434, 436 and 438 are r~nn~ct~ at the far end 440 through four ;n~nrtnrs 430a-d, whlch in this embodiment have erluivalent values of 0.03 ~H.
It should be pointed out-that while each separate portion of the helix radiates at an er~uivalent power level and does sr~uint, the overall effect_ior the helix array is for the pattern to be constant at a given angle ~ and thus to be nonsr1uinting.
The angle of propagation ~ for the antenna as a whole iB a function of the sin~l of the phase between the elements and the distance between the windings.
A helix of conductors uninterrupted by capacitive discrnt;nn;ties radiates at an angle proportional to=l/A
(which is er~uivalent to~radiating at an angle proportional to frer1uency), while the antenna of the present invention radiates at an angle independent of frer~uency (or wavelength A) and is thus nonsr1uinting. It does 80 because the array factor of the shorter elements (formed ~ WO96107216 ' ' 2 1 9 6 6 6 7 r~
by the capacitive discontinuities) is fixed in space and dominates. It is fixed in space because there is sufficient phase length in each wrapped helix transmission line to operate as a corporate divider.
Figs. 5 and 6 illustrate the beam elevation pattern of the omnidir~rtir,n~l helix with signal inputs at 1545 and 1660 Mhz respectively. Upon inspection, it is evident that both patterns have a maximum at about 15 degrees above the horizon and are thus nonsr~uinting. The outer pattern is righthand circular polarization and the inner pattern is the cross polarized left hand component.
Figs~. 7 and 8 illustrate current magnitude and phase along the lenyth of the helix when a signal at 1545 Mhz is input to the antenna. Fig. 7 further illustrates local current peaks at elements 15, 30 and 45. Flements 1 - 60 are shown in the plots. It should be noted that for antenna analysis purposes, the entire antenna conductor length is viewed as a number of discrete smaller ~l~mrnt~
(lengths). In this example the thirty inch long antenna is viewed as sixty smaller elements. In this example, if the cr,n~nrtr~ is separated into 4 portions by three uniformly placed capacitive discontinuities, then the capacitors are placed at the fifteenth/ thirtieth and forty-fifth ~l~m~ntc.
The phase difference is introduced by connecting a single feed 910 into a phasing network 900 with a single input 912 and four outputs 914, 916, 918 and 920 as WO96/07216 ' 2 1 9 6 6 6 7 1 ~ c -~ ~
illustrated in ~ig. 9. The signal path 922 f~om the input 910 is isolated and sent through separate tr~nrm;qF.;on lines of predetermined length in order to introduce the proper phase delay in 90 degree increments before connection to each o~_the ~our respective outputs 914, 916, 918 and 920 which are in~turn c~nnPrt~ to the four conductors 414, 416, 418 and 420 of the quadrifilar helix.
It will be understood that when discussing an antenna, its properties are usually describsd with respect to tr~nF~iCc; ~n or r~ t'~n emission However, it is well known from the reciprocity theorem that the directional pattern of a receiving antenna is l~ntir~l to its directional pattern as a transmitting antenna provided that no non-linear devices are used. Thus, no diSt;nrt;~n need be made between the transmitting and recsiving functions of a given antenna in either the claims of the present invention or the general analysis of radiation characteristics However, this does not mean that antenna current=distributions are equivalent on transmission and reception.
It will be further understood that various changes in the details, steps, materials, aLL~ny_msl~t of parts, which have been herein described and illustrated in~order o ~pl~;n the nature of the invsntion, may be made by those skilled in the art within the principle and scope of the invention as expressed in the claims.
Claims (11)
1. A nonsquinting end-fed helical antenna comprising:
a central mast;
a plurality of N conductive helices disposed about said mast:
each of said conductive helices having an input to accept a signal to be transmitted;
a plurality of capacitive discontinuities placed in series along each helix at a predetermined spacing, separating each helix into Z multiple sections.
a central mast;
a plurality of N conductive helices disposed about said mast:
each of said conductive helices having an input to accept a signal to be transmitted;
a plurality of capacitive discontinuities placed in series along each helix at a predetermined spacing, separating each helix into Z multiple sections.
2. The nonsquinting end-fed helical antenna as in claim 1 wherein each of said capacitors are substantially equal in value.
3. The nonsquinting end-fed helical antenna as in claim 1 wherein each of said capacitors are substantially unequal in value.
4. The nonsquinting end-fed helical antenna as in claim 1 wherein each of said multiple sections are substantially equal in length.
5. The nonsquinting end-fed helical antenna as in claim 1 further comprising inductors, each inductor having two leads, connected in series to each of said helices, wherein each of said inductors has one end connected to a single conductor and each of the other inductor ends connected together.
6. The nonsquinting end-fed helical antenna as in claim 1 further comprising phasing means with a single input and a plurality of N outputs, each output connected to a single helix, and said single input connected to a signal source, for introducing a phase difference of a signal to be transmitted to said N helices.
7. The nonsquinting end-fed helical antenna as in claim 6 wherein the phase difference between the N helices is 360/N degrees.
8. The nonsquinting end-fed helical antenna as in claim 7 wherein N is equal to 4.
9. The nonsquinting end-fed helical antenna as in claim 1 wherein Z = 2.
10. The nonsquinting end-fed helical antenna as in claim 1 wherein Z = 4.
11. The nonsquinting end-fed helical antenna as in claim 1 wherein each of said capacitive discontinuities is formed by physically separating a conductor into separate portions to form a gap between the portions and placing a dielectric across the gap connecting the portions and covering the dielectric with conductive tape.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US29719294A | 1994-08-26 | 1994-08-26 | |
| US08/297,192 | 1994-08-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2196667A1 true CA2196667A1 (en) | 1996-03-07 |
Family
ID=23145244
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002196667A Abandoned CA2196667A1 (en) | 1994-08-26 | 1995-07-27 | Nonsquinting end-fed quadrifilar helical antenna |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5721557A (en) |
| EP (1) | EP0777920B1 (en) |
| AU (1) | AU691022B2 (en) |
| CA (1) | CA2196667A1 (en) |
| WO (1) | WO1996007216A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6664938B2 (en) | 2002-03-01 | 2003-12-16 | Ems Technologies Canada, Ltd. | Pentagonal helical antenna array |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2322011A (en) * | 1997-02-04 | 1998-08-12 | Ico Services Ltd | Antenna and fabrication method |
| US6204810B1 (en) | 1997-05-09 | 2001-03-20 | Smith Technology Development, Llc | Communications system |
| SE514546C2 (en) * | 1998-05-18 | 2001-03-12 | Allgon Ab | An antenna system and a radio communication device comprising an antenna system |
| US6166709A (en) * | 1999-07-12 | 2000-12-26 | Harris Corporation | Broad beam monofilar helical antenna for circularly polarized radio waves |
| US6407720B1 (en) * | 1999-07-19 | 2002-06-18 | The United States Of America As Represented By The Secretary Of The Navy | Capacitively loaded quadrifilar helix antenna |
| US6765541B1 (en) * | 2000-04-24 | 2004-07-20 | The United States Of America As Represented By The Secretary Of The Navy | Capacitatively shunted quadrifilar helix antenna |
| JP3841100B2 (en) * | 2004-07-06 | 2006-11-01 | セイコーエプソン株式会社 | Electronic device and wireless communication terminal |
| CN100410983C (en) * | 2005-07-01 | 2008-08-13 | 台达电子工业股份有限公司 | Displaying apparatus and restoring method when turn-on there is abnormality |
| US8106846B2 (en) * | 2009-05-01 | 2012-01-31 | Applied Wireless Identifications Group, Inc. | Compact circular polarized antenna |
| US8618998B2 (en) | 2009-07-21 | 2013-12-31 | Applied Wireless Identifications Group, Inc. | Compact circular polarized antenna with cavity for additional devices |
| US10079433B2 (en) | 2014-10-20 | 2018-09-18 | Ruag Space Ab | Multifilar helix antenna |
| US10483631B2 (en) | 2016-09-26 | 2019-11-19 | The Mitre Corporation | Decoupled concentric helix antenna |
| US10424836B2 (en) * | 2016-09-26 | 2019-09-24 | The Mitre Corporation | Horizon nulling helix antenna |
Family Cites Families (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA593647A (en) * | 1960-03-01 | J. Heath Frederick | Helical antenna feed system | |
| NL76969C (en) * | 1950-05-03 | |||
| US2985878A (en) * | 1952-02-13 | 1961-05-23 | Gen Electric | Wound antenna with conductive support |
| GB980873A (en) * | 1961-05-17 | 1965-01-20 | Telefunken Patent | Improvements in or relating to unipole and dipole aerial systems |
| US3427624A (en) * | 1966-07-13 | 1969-02-11 | Northrop Corp | Low profile antenna having horizontal tunable top loading member |
| CH499888A (en) * | 1967-12-15 | 1970-11-30 | Onera (Off Nat Aerospatiale) | Helically wound single conductor antenna of reduced dimensions, and method for its manufacture |
| US3568205A (en) * | 1968-02-12 | 1971-03-02 | Goodyear Aerospace Corp | Novel helical antenna |
| US3946397A (en) * | 1974-12-16 | 1976-03-23 | Motorola, Inc. | Inductor or antenna arrangement with integral series resonating capacitors |
| GB1524210A (en) * | 1975-12-31 | 1978-09-06 | Marconi Co Ltd | Radio antennae |
| US4011567A (en) * | 1976-01-28 | 1977-03-08 | Rca Corporation | Circularly polarized, broadside firing, multihelical antenna |
| GB1547136A (en) * | 1978-02-07 | 1979-06-06 | Marconi Co Ltd | Radio antennae |
| SU1083265A1 (en) * | 1982-12-14 | 1984-03-30 | Минское Высшее Инженерное Зенитное Ракетное Училище Противовоздушной Обороны | Helical aerial |
| US4554554A (en) * | 1983-09-02 | 1985-11-19 | The United States Of America As Represented By The Secretary Of The Navy | Quadrifilar helix antenna tuning using pin diodes |
| US5032950A (en) * | 1989-12-20 | 1991-07-16 | Electronic Concepts, Inc. | Cuffed tape wrap and fill wound capacitor |
| US5343173A (en) * | 1991-06-28 | 1994-08-30 | Mesc Electronic Systems, Inc. | Phase shifting network and antenna and method |
| SG46259A1 (en) * | 1993-01-29 | 1998-02-20 | Motorola Inc | Antenna assembly for radio circuit and method thereof |
| US5371650A (en) * | 1994-02-15 | 1994-12-06 | Electronic Concepts, Inc. | Hermetically sealed capacitor and method for making the same |
-
1995
- 1995-07-27 EP EP95928184A patent/EP0777920B1/en not_active Expired - Lifetime
- 1995-07-27 WO PCT/US1995/009560 patent/WO1996007216A1/en active IP Right Grant
- 1995-07-27 CA CA002196667A patent/CA2196667A1/en not_active Abandoned
- 1995-07-27 AU AU32039/95A patent/AU691022B2/en not_active Ceased
-
1996
- 1996-04-26 US US08/639,338 patent/US5721557A/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6664938B2 (en) | 2002-03-01 | 2003-12-16 | Ems Technologies Canada, Ltd. | Pentagonal helical antenna array |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0777920A1 (en) | 1997-06-11 |
| AU691022B2 (en) | 1998-05-07 |
| AU3203995A (en) | 1996-03-22 |
| US5721557A (en) | 1998-02-24 |
| WO1996007216A1 (en) | 1996-03-07 |
| EP0777920B1 (en) | 1998-09-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |