CA1129086A - Interference canceling device for use in antenna system - Google Patents
Interference canceling device for use in antenna systemInfo
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- CA1129086A CA1129086A CA332,740A CA332740A CA1129086A CA 1129086 A CA1129086 A CA 1129086A CA 332740 A CA332740 A CA 332740A CA 1129086 A CA1129086 A CA 1129086A
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- antenna
- beam pattern
- combination
- antenna beam
- pattern
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Abstract
Abstract of the Disclosure The described system utilizes a pair of antenna beam patterns, one of which is adapted to provide the desired signal and all interfering signals, and the other of which is adapted to provide only the interfering signals. The patterns are then combined to produce substantially only the desired signal as the combined output.
Description
11~9~)86 Field of the Invention This inventi.on relates to communications systcms and, more particularly, to coT~unications systems in which simple, relatively inexpensive arrangements are utilized to automatically eliminate or reduce external interference.
Background of the Invcntion As is well known and understood, one of the major concerns of : .
designers of antenna system communication links is the elimination or reduction of external interference sources, such as jamming, self-interference, atmos-pheric noise, man-made noise, and acoustic noise. As is also well known, most of the arrangements which attempt to resolve these problcms of external inter-ference do so in a relatively complex manner, ortentimes utili~ing very large directional antennas and/or wi.th antennas h~vi.n~ llundretls" or cvell more, elements. This problem of external interference is especially prevalent in the area of mobile communications systems where omnitlirecti.onal antennas are employed, because of the large numbers of users operating in the same frequency band and because of multipath. Use of very large directional antennas in such ~ ;
mobile arena will be seen to be almost a physical impossi~ility, and an economic .
~.~ Z9~
l I lmpract1caltty, Summary of the Invent10n As w~ll become clear here~nafter, the ~nterference cancel1ng system of the present lnvent~on affords an operat10n wh1ch slmulate~ that of a d1rect10n-l al antenn~ ln ellmlnatlng, or reducing, external 1nterference sources, but w1th ; I slmple ~nd lnexpens1ve c1rcu1try, and w~th a small number of ~ntenna ele~ents (typlcally, anywheres from 2 to 8). In a f1rst embod~ment of the tnvent~on, orthogonal mult1plex1ng lt employed 1n con~unct~on w1th ~ notch ~ntenna to cancel Interference arrlvtng from all d~rect10ns exceDt over the narrow be~m ~ldth port10n forred wlth the notched antenna. As w111 be seen, 1n such ver-slon an almost omnldlrect1cnal antenna 1s ut11~zed w1th a narrow notch, or : nulled-out beamwldth,along ~1th a full omnidirect10nal antenna to enable 1m-plementat10n of the system w~th s1mple, small antennas. In A second embod1ment of the 1nvent10n, the ampl1tude 1n element separat10n of an array antenna are predeterm1ned to obta1n a steep slope 1n lts beam pattern, ~lth the output be-lng progresslvel~ phise shlfted and comblned to provlde a dupl1cate beam pat-tern for subsequent subtract10n so as to el1m1nate ~nterference from all d1-rectlons except over a srall anQular sector. In such Yers10n, the requlrement ~or orthogonally mult1plexln~ two channels through the rece1ver 1s obv1ated, so as to prov1de A further cost s~v1n~s.
Br1ef Descr1pt10n of the Drawln~
~hese and other features of the present 1nvent10n w111 be more read~ly understood from a conslder~t10n of the followlnq descript10n taken 1n connec-tlon ~lth the accompany1ng draw1ng ln wh1ch ¦ FIGURE l 1s a funct10nal block d1agram of a multtplexed lnterference I cancellng recelver system constr~cted ln accordance w1th the lnvent10n;
; I FIGURE 2 ls a s~mpllfled 111ustrat10n of an antenn~ pattern helpful 1n ~ an understand~ng of the block dlagram of FI~URE l:
' ~ -2-., l _ ,; . " ._ I!
. !
l I FIGURES 3 and 4 are s1mpllfied 111ustrat~ons of an alternative antenna ! pattern and resultant beam processln~ appllcable to a mod1ficatlon of the ln-terference cancel;n~ system of FIGlIRE l;
ll FIGURE 5 i5 a functional block dlaar~m of an 1nterference cancel1na antenna system constructed 1n accordance wlth the ~nventlon: and FIGURE 6 ls a slmpllfled 111ustratlon of the resoltant antenna ~eam process1ng applicable to the lnterference cancelinn antenna system of FIGlIRE S
., .
Deta11ed Descr~ptlon of the Drawin~
~; lO The lnterference canceltnq system sho~m ln FTr~lJRE l ellmlnates, or reduces 1nterference 1n a transm~sslon l~nk hy ut~ lnn ortho~onal multiplex-in~ 1n conjunctlon w1th a notch antenna (i.e., an antenna which has a sln~le ¦ deep nu11 over a small angular beam w1dth), The inset alonnside Flr~llQE l represents the beam pattern of an almost omn~d~rectlollal antenna ln havlng a narrow notch or nulled-out beamw1dth, 1n wh1ch "~" represents the des1red s19-nal recelved and "I ", "I ", "I ",........ "~ " represents external 1nterference~ l 2 3 n ; slgnals. The output of the notch antenna lO (channel ~) ls nrthoqonally multl-plexed w1th the output of an omnldirectional antenna 12 (channel B), wlth the multlplexin~ belnq of tlme, frequency or space methnd sn lonn as the slgnals ~ 20 From the antennas 10, 12 are rendered non-lnterferln~ wlth each other. The ii;~, output from the multlplexer 14 is then ampl1fle~ in a recel~er lfi, and then ~, separated in a de-multlplexer 18, A subtractor 2n is emploved, to one lnput of whlch is provlded the output of de-multlplexer l~ wh~ch cnrresponds to the ; channel B s19nal, as compr1s1n~ the des1red 1nformation, plus all of the 1nter-fering si~nals from the external sources. nn the other hand, hy rotat1n~ the ; notch antenna 10 (or electronically scanninq lt) unt11 lts notch 1s po1nt1n~
1n the dlrect10n of the desired siqnal (as shown ln the ~nset), then the output ;~ from the de-multlplexer 18 whlch corresponds to the channel A sl~nal would con-ta1n all of the 1nterferln~ s1gnals, but not the deslred slnnal. Thls second output prov1des a col)erent and correlated rF~11ca of all the ~nterference j 3 I . ` .
' ' I ll~,9~
- Ij l I assoc1ated wlth the sl~nal enter;n~ the omni~lrectiona1 antenna l~, and ls prov1ded as the other ~nPut to the subtractor 2n. Rv ~ncludinq ~mpl1tude and phase adjust~ng c1rcu1ts 22, 24 1n this second branch, to account for any 1n-herent d1fferences ~n ga~n and del~y 1n the two ortho~onal channels, the de-1 mult1plexed output from the notch antenna lO can he directlv suhtracted from ¦¦ the de-mult/plexed output from the omn~d~rect10nAl antenna 12 to yleld a ¦ totally 1nterference free si~nal.
A mafor advanta~e of th1s FIGlIRE I emhod1ment w111 be seen to be that all 1nterference enterin~ the antenna l~ wh1ch is outslde of the notched beam 1s vlrtually el1m1nated w~thout requ~r~nn any complex adapt1ve processing, or requ1r1ng a lar~e complex narrow beam ~ntenna. Th1s makes the FlGllRE 1 system des1rable for mob~le commun1cat10ns usa~e, and for sm~11, ll~htwel~ht, tactlcal communlcat10ns equ1pment. -As wlll ~e readilv apparent to those sk111ed ln the art, the notch antenna lO of FIGURE l represents the ma1n ele~ent 1n the 1nterference can-; cel1ng system there descrlbed, and 1ntroduces d1fferent re(~ulrements for oper-at10n than are normally encountered 1n typ1cal antenna des19n. For example, lnstead of be1n~ concerned w1th a des~gn whtch forms a d~rectlve beam hav~n~
low s1delobes, or des1gn1ng an adapt1ve system hav~nq several movable nulls, the antenna eng~neer lts here concerned w1th prov1d1n~ a f1xed pattern wh1ch conta~ns un~fonm recept10n 1n all dtrect10ns, except for that 1n which the normal beam slot po1nts. Add1ttonally, to be effect1ve, the antenna des1gn needs a slope 1n the p~ttern developed, at the potnt of the null, and to be as steep a 510pe as ts pract1cal. Such A requ/red ~attern 1s /llustrat1vely ~25 shown ln FIGURE 2.
General deslgn procedures for prov1d1n~ an array antenna hav1n~ the type of pattern shown In FIGIIRE 2 are descr1bed 1n my tJn1ted States Patents No. 3,130,410 and No. 3,605,106. As noted there1n, such patterns are made up of products and/or sums of 5~n r funct10ns, and can be ~ch1eved by controll1nc ~30 ~ both the lltudes and spdc1nns of array antennd elements. As a result, the ';
`'; _ _ :. :
. ~
)8~
-slope of a null in an antenna beam pattern can be made steep, either by pro-viding one or more ~Sin mx]y ~erms or by appropriate amplitude and phase con-Sin x trols when summing several [Sin mx~ functions using sub-arrays. Further ex-Sin xplanation can be had by referring to these patents, as well as to the article "Coded-Linear-Array Antenna", published in Volume 39, No. 2, of Electrical Communications Magazine.
An alternative version of a notch antenna that could be used with the FIGURE 1 canceling system is one having a steep slope, but with a somewhat wider nulled beamwidth, as shown in Figure 3. With this version, the antenna pattern can be electronically scanned to provide a second received beam which is angularly displaced by a small amount. The two beams 30, 32 (FIGURE 4) could then be positioned so that the desired signal "S" lies near the edge of one receiving beam, e.g. 30, while being nulled out of the second receiving ; beam, 32. Although this alternative scheme continues to null out the inter-ference sources Il, I2, ....... I , it does introduce a second sector (sector B) which is vulnerable to interferences. However, the beam width of sector A, wherein the desired signal S is being received, (and therefore, sector B) can -` be made very small. Such an alternative approach might be useful where it is found more practical to design an array antenna with a steeper slope and wider notch beamwidth than as illustrated in Figure 2.
The functional block diagram of Figure 5 is intended for use with a second embodiment of the invention in which cancelation of the interference is ; provided at radio frequencies directly at the antenna elements themselves, and `~ without the need for orthogonally multiplexing two channels. A significant savings in cost will be seen to result, and again follows in part, from the ; ability to predetermine the amplitude and element separations of an array antenna so as to obtain a steep slope and a narrow beam slot. The antenna elements are here represented by the reference numerals 100, 200, 300, ..... N, with each having its signal output being applied to an adder 50 by means of ~'~
., .
.9g; ~,~
l ~ amplltude and ph~se control clrcu~ts K , K , K , ..... K . A second adder 60 1s employed, to the lnputs of ~hlch are recelved the outputs of the a~pl1tude and phase control c1rcu1ts, but proqressively phase shlfted by clrcu1ts ~,
Background of the Invcntion As is well known and understood, one of the major concerns of : .
designers of antenna system communication links is the elimination or reduction of external interference sources, such as jamming, self-interference, atmos-pheric noise, man-made noise, and acoustic noise. As is also well known, most of the arrangements which attempt to resolve these problcms of external inter-ference do so in a relatively complex manner, ortentimes utili~ing very large directional antennas and/or wi.th antennas h~vi.n~ llundretls" or cvell more, elements. This problem of external interference is especially prevalent in the area of mobile communications systems where omnitlirecti.onal antennas are employed, because of the large numbers of users operating in the same frequency band and because of multipath. Use of very large directional antennas in such ~ ;
mobile arena will be seen to be almost a physical impossi~ility, and an economic .
~.~ Z9~
l I lmpract1caltty, Summary of the Invent10n As w~ll become clear here~nafter, the ~nterference cancel1ng system of the present lnvent~on affords an operat10n wh1ch slmulate~ that of a d1rect10n-l al antenn~ ln ellmlnatlng, or reducing, external 1nterference sources, but w1th ; I slmple ~nd lnexpens1ve c1rcu1try, and w~th a small number of ~ntenna ele~ents (typlcally, anywheres from 2 to 8). In a f1rst embod~ment of the tnvent~on, orthogonal mult1plex1ng lt employed 1n con~unct~on w1th ~ notch ~ntenna to cancel Interference arrlvtng from all d~rect10ns exceDt over the narrow be~m ~ldth port10n forred wlth the notched antenna. As w111 be seen, 1n such ver-slon an almost omnldlrect1cnal antenna 1s ut11~zed w1th a narrow notch, or : nulled-out beamwldth,along ~1th a full omnidirect10nal antenna to enable 1m-plementat10n of the system w~th s1mple, small antennas. In A second embod1ment of the 1nvent10n, the ampl1tude 1n element separat10n of an array antenna are predeterm1ned to obta1n a steep slope 1n lts beam pattern, ~lth the output be-lng progresslvel~ phise shlfted and comblned to provlde a dupl1cate beam pat-tern for subsequent subtract10n so as to el1m1nate ~nterference from all d1-rectlons except over a srall anQular sector. In such Yers10n, the requlrement ~or orthogonally mult1plexln~ two channels through the rece1ver 1s obv1ated, so as to prov1de A further cost s~v1n~s.
Br1ef Descr1pt10n of the Drawln~
~hese and other features of the present 1nvent10n w111 be more read~ly understood from a conslder~t10n of the followlnq descript10n taken 1n connec-tlon ~lth the accompany1ng draw1ng ln wh1ch ¦ FIGURE l 1s a funct10nal block d1agram of a multtplexed lnterference I cancellng recelver system constr~cted ln accordance w1th the lnvent10n;
; I FIGURE 2 ls a s~mpllfled 111ustrat10n of an antenn~ pattern helpful 1n ~ an understand~ng of the block dlagram of FI~URE l:
' ~ -2-., l _ ,; . " ._ I!
. !
l I FIGURES 3 and 4 are s1mpllfied 111ustrat~ons of an alternative antenna ! pattern and resultant beam processln~ appllcable to a mod1ficatlon of the ln-terference cancel;n~ system of FIGlIRE l;
ll FIGURE 5 i5 a functional block dlaar~m of an 1nterference cancel1na antenna system constructed 1n accordance wlth the ~nventlon: and FIGURE 6 ls a slmpllfled 111ustratlon of the resoltant antenna ~eam process1ng applicable to the lnterference cancelinn antenna system of FIGlIRE S
., .
Deta11ed Descr~ptlon of the Drawin~
~; lO The lnterference canceltnq system sho~m ln FTr~lJRE l ellmlnates, or reduces 1nterference 1n a transm~sslon l~nk hy ut~ lnn ortho~onal multiplex-in~ 1n conjunctlon w1th a notch antenna (i.e., an antenna which has a sln~le ¦ deep nu11 over a small angular beam w1dth), The inset alonnside Flr~llQE l represents the beam pattern of an almost omn~d~rectlollal antenna ln havlng a narrow notch or nulled-out beamw1dth, 1n wh1ch "~" represents the des1red s19-nal recelved and "I ", "I ", "I ",........ "~ " represents external 1nterference~ l 2 3 n ; slgnals. The output of the notch antenna lO (channel ~) ls nrthoqonally multl-plexed w1th the output of an omnldirectional antenna 12 (channel B), wlth the multlplexin~ belnq of tlme, frequency or space methnd sn lonn as the slgnals ~ 20 From the antennas 10, 12 are rendered non-lnterferln~ wlth each other. The ii;~, output from the multlplexer 14 is then ampl1fle~ in a recel~er lfi, and then ~, separated in a de-multlplexer 18, A subtractor 2n is emploved, to one lnput of whlch is provlded the output of de-multlplexer l~ wh~ch cnrresponds to the ; channel B s19nal, as compr1s1n~ the des1red 1nformation, plus all of the 1nter-fering si~nals from the external sources. nn the other hand, hy rotat1n~ the ; notch antenna 10 (or electronically scanninq lt) unt11 lts notch 1s po1nt1n~
1n the dlrect10n of the desired siqnal (as shown ln the ~nset), then the output ;~ from the de-multlplexer 18 whlch corresponds to the channel A sl~nal would con-ta1n all of the 1nterferln~ s1gnals, but not the deslred slnnal. Thls second output prov1des a col)erent and correlated rF~11ca of all the ~nterference j 3 I . ` .
' ' I ll~,9~
- Ij l I assoc1ated wlth the sl~nal enter;n~ the omni~lrectiona1 antenna l~, and ls prov1ded as the other ~nPut to the subtractor 2n. Rv ~ncludinq ~mpl1tude and phase adjust~ng c1rcu1ts 22, 24 1n this second branch, to account for any 1n-herent d1fferences ~n ga~n and del~y 1n the two ortho~onal channels, the de-1 mult1plexed output from the notch antenna lO can he directlv suhtracted from ¦¦ the de-mult/plexed output from the omn~d~rect10nAl antenna 12 to yleld a ¦ totally 1nterference free si~nal.
A mafor advanta~e of th1s FIGlIRE I emhod1ment w111 be seen to be that all 1nterference enterin~ the antenna l~ wh1ch is outslde of the notched beam 1s vlrtually el1m1nated w~thout requ~r~nn any complex adapt1ve processing, or requ1r1ng a lar~e complex narrow beam ~ntenna. Th1s makes the FlGllRE 1 system des1rable for mob~le commun1cat10ns usa~e, and for sm~11, ll~htwel~ht, tactlcal communlcat10ns equ1pment. -As wlll ~e readilv apparent to those sk111ed ln the art, the notch antenna lO of FIGURE l represents the ma1n ele~ent 1n the 1nterference can-; cel1ng system there descrlbed, and 1ntroduces d1fferent re(~ulrements for oper-at10n than are normally encountered 1n typ1cal antenna des19n. For example, lnstead of be1n~ concerned w1th a des~gn whtch forms a d~rectlve beam hav~n~
low s1delobes, or des1gn1ng an adapt1ve system hav~nq several movable nulls, the antenna eng~neer lts here concerned w1th prov1d1n~ a f1xed pattern wh1ch conta~ns un~fonm recept10n 1n all dtrect10ns, except for that 1n which the normal beam slot po1nts. Add1ttonally, to be effect1ve, the antenna des1gn needs a slope 1n the p~ttern developed, at the potnt of the null, and to be as steep a 510pe as ts pract1cal. Such A requ/red ~attern 1s /llustrat1vely ~25 shown ln FIGURE 2.
General deslgn procedures for prov1d1n~ an array antenna hav1n~ the type of pattern shown In FIGIIRE 2 are descr1bed 1n my tJn1ted States Patents No. 3,130,410 and No. 3,605,106. As noted there1n, such patterns are made up of products and/or sums of 5~n r funct10ns, and can be ~ch1eved by controll1nc ~30 ~ both the lltudes and spdc1nns of array antennd elements. As a result, the ';
`'; _ _ :. :
. ~
)8~
-slope of a null in an antenna beam pattern can be made steep, either by pro-viding one or more ~Sin mx]y ~erms or by appropriate amplitude and phase con-Sin x trols when summing several [Sin mx~ functions using sub-arrays. Further ex-Sin xplanation can be had by referring to these patents, as well as to the article "Coded-Linear-Array Antenna", published in Volume 39, No. 2, of Electrical Communications Magazine.
An alternative version of a notch antenna that could be used with the FIGURE 1 canceling system is one having a steep slope, but with a somewhat wider nulled beamwidth, as shown in Figure 3. With this version, the antenna pattern can be electronically scanned to provide a second received beam which is angularly displaced by a small amount. The two beams 30, 32 (FIGURE 4) could then be positioned so that the desired signal "S" lies near the edge of one receiving beam, e.g. 30, while being nulled out of the second receiving ; beam, 32. Although this alternative scheme continues to null out the inter-ference sources Il, I2, ....... I , it does introduce a second sector (sector B) which is vulnerable to interferences. However, the beam width of sector A, wherein the desired signal S is being received, (and therefore, sector B) can -` be made very small. Such an alternative approach might be useful where it is found more practical to design an array antenna with a steeper slope and wider notch beamwidth than as illustrated in Figure 2.
The functional block diagram of Figure 5 is intended for use with a second embodiment of the invention in which cancelation of the interference is ; provided at radio frequencies directly at the antenna elements themselves, and `~ without the need for orthogonally multiplexing two channels. A significant savings in cost will be seen to result, and again follows in part, from the ; ability to predetermine the amplitude and element separations of an array antenna so as to obtain a steep slope and a narrow beam slot. The antenna elements are here represented by the reference numerals 100, 200, 300, ..... N, with each having its signal output being applied to an adder 50 by means of ~'~
., .
.9g; ~,~
l ~ amplltude and ph~se control clrcu~ts K , K , K , ..... K . A second adder 60 1s employed, to the lnputs of ~hlch are recelved the outputs of the a~pl1tude and phase control c1rcu1ts, but proqressively phase shlfted by clrcu1ts ~,
2 0, 3 p,.,.... n 0. The result of thls comblnat~on ~s to Drov~de a dupl1cate beam pattern from the adder 60 whlch is scanned by the s~ll dnqular seqments, p, as comp~red to the output of the adder 50. ~he two adder outputs are then : coupled to an antenna pattern canceler 70, whereln the output of the scanned pattern ls 11near1y subtracted from the or1~1nal notch beam p~ttern to provlde a substant~ally complete cancelat~on of the Interference, w~th the resultant ~lO s1gnal then be1ng pro~1ded atrece1ver 72.
In hctuallty, the subtract~on ls not ~ complete one, as can be seen from the resultant beam process1ngs of FlGlJRE 6. ~he rece~ved notch antenna beam pattern ls shown as 80, whlle the scanned notch ~ntenna pattern ls shown as B2. As ln the lllustrat~on of FIGtJRE 4, Interference ~s not com~letely can-celed 1n the two, small angular sectors A and B. As ~111 be apprec~ated, If : the notch 1n the antenna pattern 1s sufflclently narrow, then, If omnld1rect10n .
al antenna elements are utll1~ed, lt would only beco~e necessary to use the center element as the second lnput to the pattern canceler ~n. To quaranty . that the 1nterference from both adders 50, 6n would be ex~ctly ~n phase, ln-dependent of the d1rect10n of arr1v~1 of the 1nterfer~nq slqnals, e1ther the progress~ve phase sh1ft should be svmmetr1cal ahout such center element, or the a compos1te 1n1tlal beam pattern should be phase shlfted by (n ~. As ~lth the conf1guratlon of FlGURE l~ the construct~on accordlng to th1s embodlment of th 1nventlon could be ut~ ed to large advantAge ln any commun1catlons 11nk ~here .25 1t 1s des1rable, or necessary, to ellm1nate or reduce external 1nterference, . such as from a ~ammer, ~tmospher1c nolse, man-made nolse, etc. Anv quant1ty of such 1nterferlng sources that enter the antenna from outs1de the overlapped . narro~ beam sectors would thus be s1multaneously el1mlnated, ~lthout the re-qu1rement of any complex adapt~ve process1na belnq needed.
~ ~h11e there have been descr~bed ~hat are cons1dered to be 111ustrat1ve -h-. ., '. I . ",~
., , , ~
,90~ ~1 l ~ embod~ments of the present 1nvent10n, it w111 he read11y apparent to those sk111ed ln the art that mod1f1catlons may be made wlthout depart1ng from the scope of the taach~nqs here1n of prov1d1nn 1nterference charaCter1st1cs com-l mensurate w1th a d~rect10nal antenna hav1nq a very narrow beam, but of sub-¦ stant1ally reduced sl~e -- analys~s show1nq that s1~n~f~cant 1mProvements can ¦¦ be atta1ned w1th Just a patr of antenna elements, and that substant1al ~m-provement results w1th no more than the employ~ent of R such elements. Bes~des be1ng easler to bu~ld, and 1mmensely cheaper, the 1nterference cancel1nq sys- ¦tems of the present 1nvent10n enable operat10n to cont~nue even at the lo~er l frequenc1es where otherwlse very larqe d1rect10nal antennas arr requ1red. ~lth¦
the 1nventlon, ~t becomes but ~ s1mple matter to incorporate the systems 1n ~ ¦mob11e envlronment, as the physical constr~1nts no lonqer pre~ent employment of the ant nna system on a mov~ng motor vehicle.
;~,.,'' ' :`'' ,.:~ .
~20 ':~
`",' . I
`~ 25 ,' ' . ,.
,:. i . .' 3o , 7_ '~' I
In hctuallty, the subtract~on ls not ~ complete one, as can be seen from the resultant beam process1ngs of FlGlJRE 6. ~he rece~ved notch antenna beam pattern ls shown as 80, whlle the scanned notch ~ntenna pattern ls shown as B2. As ln the lllustrat~on of FIGtJRE 4, Interference ~s not com~letely can-celed 1n the two, small angular sectors A and B. As ~111 be apprec~ated, If : the notch 1n the antenna pattern 1s sufflclently narrow, then, If omnld1rect10n .
al antenna elements are utll1~ed, lt would only beco~e necessary to use the center element as the second lnput to the pattern canceler ~n. To quaranty . that the 1nterference from both adders 50, 6n would be ex~ctly ~n phase, ln-dependent of the d1rect10n of arr1v~1 of the 1nterfer~nq slqnals, e1ther the progress~ve phase sh1ft should be svmmetr1cal ahout such center element, or the a compos1te 1n1tlal beam pattern should be phase shlfted by (n ~. As ~lth the conf1guratlon of FlGURE l~ the construct~on accordlng to th1s embodlment of th 1nventlon could be ut~ ed to large advantAge ln any commun1catlons 11nk ~here .25 1t 1s des1rable, or necessary, to ellm1nate or reduce external 1nterference, . such as from a ~ammer, ~tmospher1c nolse, man-made nolse, etc. Anv quant1ty of such 1nterferlng sources that enter the antenna from outs1de the overlapped . narro~ beam sectors would thus be s1multaneously el1mlnated, ~lthout the re-qu1rement of any complex adapt~ve process1na belnq needed.
~ ~h11e there have been descr~bed ~hat are cons1dered to be 111ustrat1ve -h-. ., '. I . ",~
., , , ~
,90~ ~1 l ~ embod~ments of the present 1nvent10n, it w111 he read11y apparent to those sk111ed ln the art that mod1f1catlons may be made wlthout depart1ng from the scope of the taach~nqs here1n of prov1d1nn 1nterference charaCter1st1cs com-l mensurate w1th a d~rect10nal antenna hav1nq a very narrow beam, but of sub-¦ stant1ally reduced sl~e -- analys~s show1nq that s1~n~f~cant 1mProvements can ¦¦ be atta1ned w1th Just a patr of antenna elements, and that substant1al ~m-provement results w1th no more than the employ~ent of R such elements. Bes~des be1ng easler to bu~ld, and 1mmensely cheaper, the 1nterference cancel1nq sys- ¦tems of the present 1nvent10n enable operat10n to cont~nue even at the lo~er l frequenc1es where otherwlse very larqe d1rect10nal antennas arr requ1red. ~lth¦
the 1nventlon, ~t becomes but ~ s1mple matter to incorporate the systems 1n ~ ¦mob11e envlronment, as the physical constr~1nts no lonqer pre~ent employment of the ant nna system on a mov~ng motor vehicle.
;~,.,'' ' :`'' ,.:~ .
~20 ':~
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`~ 25 ,' ' . ,.
,:. i . .' 3o , 7_ '~' I
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a signal communications system:
first means for generating a single first antenna beam pattern to provide a signal return from a desired signal source accompanied by all unde-sired interference returns arriving from a plurality of interference sources from any direction except for a narrow sector;
second means for generating a single second antenna beam pattern to provide from all of said interference sources a coherent correlated replica of all of said undesired interference returns provided by said first antenna beam pattern unaccompanied by said desired signal source; and third means coupled to said first and second means for subtracting the returns provided by said first and second antenna beam patterns to produce substantially only said desired signal return as an output of said system.
first means for generating a single first antenna beam pattern to provide a signal return from a desired signal source accompanied by all unde-sired interference returns arriving from a plurality of interference sources from any direction except for a narrow sector;
second means for generating a single second antenna beam pattern to provide from all of said interference sources a coherent correlated replica of all of said undesired interference returns provided by said first antenna beam pattern unaccompanied by said desired signal source; and third means coupled to said first and second means for subtracting the returns provided by said first and second antenna beam patterns to produce substantially only said desired signal return as an output of said system.
2. The combination of claim 1 wherein said first means includes an omnidirectional antenna, and wherein said second means includes an antenna with the beam pattern having a single notch pointing in the direction of said desired source.
3. The combination of claim 2 further including multichannel signal processing circuits for said provided returns disposed between both said first and second means and said third means, at least one of said channels including amplitude and phaze adjusting means to control the relative gain and delay characteristics of said signal processing circuits.
4. The combination of claim 2 wherein said notch beam pattern has a narrow nulled beamwidth of steep slope.
5. The combination of Claim 1 wherein said first means includes an array antenna having elements predeterminedly selected as to amplitude and element separation to produce in combination said first antenna beam pattern having a steep slope and with a narrow beam slot, and wherein said second means introduces prede-termined progressive phase shifts in the elements of said array antenna to produce said second antenna beam pattern which is a duplicate of said first antenna pattern except angularly displace therefrom.
6. The combination of Claim 5 wherein said elements of said array antenna include amplitude adjusting means and the out-puts of said amplitude adjusting means are combined in a first adder, and wherein the amplitude adjusting means are connected to corresponding phase shifters and the outputs of said phase shifters are combined in a second adder, and wherein said third subtracting means responds to the outputs of said first and second adders.
7. The combination of Claim 5 wherein said first antenna beam pattern and the second displaced antenna beam patterns have relatively narrow non-overlapping sectors, the phase shift for said elements being selected to that the desired signal return arrives within one of said non-overlapping sectors.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US97001778A | 1978-12-18 | 1978-12-18 | |
| US970,017 | 1978-12-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1129086A true CA1129086A (en) | 1982-08-03 |
Family
ID=25516309
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA332,740A Expired CA1129086A (en) | 1978-12-18 | 1979-07-25 | Interference canceling device for use in antenna system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1129086A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4638318A (en) * | 1983-08-26 | 1987-01-20 | The United States Of America As Represented By The Secretary Of The Army | Small angular beamwidth antenna system |
-
1979
- 1979-07-25 CA CA332,740A patent/CA1129086A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4638318A (en) * | 1983-08-26 | 1987-01-20 | The United States Of America As Represented By The Secretary Of The Army | Small angular beamwidth antenna system |
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