CA2057947A1

CA2057947A1 - Method and apparatus for broadband electromagnetic energy coupling

Info

Publication number: CA2057947A1
Application number: CA 2057947
Authority: CA
Inventors: Bibhas R. De; Michael A. Nelson
Original assignee: Individual
Current assignee: Chevron USA Inc
Priority date: 1990-12-20
Filing date: 1991-12-18
Publication date: 1992-06-21
Also published as: GB9126811D0; FR2674439A1; GB2251080A; DE4142348A1

Abstract

ABSTRACT OF THE DISCLOSURE

A method and apparatus measures dielectric properties over a broad range of frequencies. The functions of various conductivity and dielectric constant measuring devices are combined in a single tool. A measuring tool includes novel transmitting and receiving antennas. Electromagnetic energy flows to a transmitting antenna. A stripline adapter permits transmission to a stripline having a metallic central strip. A strip face is bent at approximately right angles, and has a length that is compatible with the desired frequency coverage. A ground plane extends from the stripline adapter to the right angle bend, and a void exists between the center strip and the ground plane. A dielectric is positioned to nearly fill the void. The antennas are positioned so that the strip face lies flush with the tool face, to permit electromagnetic energy to be transmitted into and out of the material to be analyzed. An enclosure comprised of four metallic walls surrounds the stripline, and is in electrical contact with the ground plane and the stripline adapter. The invention permits an analysis of the fluids in mammal tissue, and can be used in cancer therapy by hyperthermia.

Description

20579~7 01METHOD ~ND APPARATUS FOR BROADE3AND E~ECTRO~IAG1~15TIC
02ENERGY COUP~NG

04FIELD OF TE~E ~NVENTION
_ OS
06 The present invention relates g~nerally to th~
07 electromagnetic coupling and analy~l~. More ~peci~ically, 08 thls invention provide~ an antenna which can co~bine th~
og function~ of various resistivity and ~ielectrlc con~tant device~ into a single tool, capabl~ of operating ov~r a wide 11 range of frequencies. It i~ particularly u~eful i~ the 12 field of medical technology.

14 BACKGROUND OF TH~ ~NV~NTSON

16 In the field of medical technology, lt i~ well knon~ that 17 electromagnetic en~rgy i~ u~eful ~n variou~ type~ of 18 dlagno~es and treatments. For example, recent ~ta~irtic~
19 show that pulmonary and cardiopulmonary di~ea~es ar~
re~ponsibl- for more than three ~ on ho~p~tal a~ isfiion~
21 and 30,000 death~ every year in the United States.
22 Pulmonary abnor~litieA are virtually alway~ as~oc1~eed w~th 23 change~ ln lunq w~ter content or distributlon. Mo~t workers 24 agre~ that the~ no single, nond~tructiv~ ~ctbod availablo to detoct accurately early change~ in lung 26 water content.

28 For a elinlcally u~eful techniquo, it 18 deslrabl~ to detect early ch~nge~ ~n both thc extr~vascular lung wat-r, which ~trongly r~flect~ mo~t pul~onary abnor~alitie~, and the 31 intravascula~ compartment. Recently, the U80 of the 32 electromagnetic ~ethods to detect changes in lung ~ter 33 content have shown promi~ing initial result~, particularly 34 for detecting small variat~ons in water content.

2 ~ 7 01 Particularly at microwave frequencies, changes in the 02 dielectric properties of tissue are closely related to the 03 amount of water present. Electromagnetic techniques, 04 therefore, basically utilize changQs in th~ permittivity and oS conductivity of the lung region to detect change~ in lung 06 water content. This method has the advantag~ of u~ing 07 highly penetrating electromaqnetic signals rather than 08 ultrasonic signals which are both highly attenuated and og di~pcr~d in the lung. Furthermore, electro~agn~tic techn~ques hav~ the potential or continuous monitoring of 11 patients in intensive care units, such as those ~ith heart 12 failurc or extensive burns.

14 U.S. Patent No. 4,240,445 issued to ~skand~r et al. and i6 incorporated hereln by re~erence for all purposes. Iskander 16 teache~ a method of coupling electrom~gnetio ~norgy into a 17 material such a~ tissue, to mea~uro water content.
18 Measuring lung water content is an especially u6eful 19 application. ~owever, I~kander'8 device i~ ~o lasge that only a few antenna~ can b~ place on th~ che~t, and the 21 ant0nna cannot be de~cribed a6 a po1~t ~ource. Also, the 22 electrie f~ld vanishe~ at some di~tanc~ fro~ th~ ~ntenna, 23 as the electric field~ ln th~ t~o parallol -~lots are 2~ oppositely dir~ct~d. Furth~r~ore, ~ res~tor is included in the antenna, which d$ssipate4 much of the el~ctro~agnetic 26 energy ln the antenna itself and introduce~ a limitation in 27 th~ power handling capability of th~ ant~nna. Additional 2~ pr~or wor~ includess M. F. Iskander and C. H. Durney 29 (1980): "Electro~gnet$c Technigue~ for Medlcal Diagno~is:
A Reviewn, Proceeding~ of ~EEE, vol. 68, no. 1. and 31 M. F. Iskander et al ~1982): nTwo-dimensional Technique to 32 Calculate the EM Power Deposition Pattern in tho Buaan 33 ~odyn, Journal of Microwave Power, vol. 1~, no. 3. There is 34 thus a need for a device that is compact enough to permit ~3~7 01 placing of many antennas forming an array on a ches~ to 02 obtain a well-defined image of the chest cavity, a device 03 that has an antenna that can be mathematically de~cribed as 04 a point source, and one which does not suffer fro~
05 cancellation of the electric field at a certain distance.

07 A dielectric transm$tting and mea~uring devic~ can also be 08 used to heat an interior portion o~ a mammalian body to og de~troy or reduce the size of tumors. Tumor reduction therapy, or cancer therapy by hyperth~rmia, co~bined with 11 radiation or drugs is known in the art to either stop or 12 slow down the growth o cancer cells, or cau~e the death of 13 the cancer cells. (Se~, for example, Streff~r, C., ~Cancer 14 Therapy by Hyperther~ia and Radiation", Urban and Schwarzenberg, Munich, F.~.G., 1980 and Detbylefs~n, L.A.
16 (Edltor), "The Thlrd International Sy~posium: Cancer 17 Therapy by Hypcrthermia, Drugs and Radlation, Colorado State 18 University, Ft. Collin~, U.S.A., 1980.) one such devic~ i~ disclo~ed by J. Scheiblich ~t al.
21 "R~iofreguency-Induced Hyperthermla in the Pro~taten, 22 Journal of Mlcrowav~ Power, vol. 17, no. 3, 1982, Otta~a, 23 Canada. Sche$blich et al's d~vice wor~ only at 24 singl~ fr~quency.
26 ~ propagating ~loctromagnetic wave ha~ two fund~ental 27 charactori~tic~, a~plitud- and phase. ~y comparing the 28 amplitudo and pha~e of an electromagnctic wave aE it passes 29 receivers, propag~tion characteri~tics of the probed ~edium may be studied, Measurem~nt of these two charactetistics 31 may b~ used to deter~ine th~ dielectric con~tant and 32 the conductivity of th~ media through which the waY~
33 ~8 propag~ted.

2 ~ 4 7 01 However, no one tool in the prior art is capable of probing 02 or coupling energy into a material over a broad b~nd of 03 frequencies. It is therefore advantageou~ to exten~ the 04 frequency range.

06 ~he largest hurdle to developing such a broadband dielectric 07 tool has been the lack of a suitable broadband antenna that 08 can couple electromagnetic energy to and fro~ ~ material, 09 and that i8 compact enough to fit within the oonf$nes o~
a tool.

12 ~ho prior work i5 limited in the atte~pt~ at electromagnetic 13 coupling, analysis, and treat~ent, in that no suitable 14 c~ngle antenna elemont has been designed which can couple electrom~gnetic energy into a material, suzh as na~mal 16 tissue, over a broad range of frequencie~, that i~ also 17 suficiently compact and is capablè of handling high power 18 levels. There i8 therefore a need for a d~vice and a method 19 for use in such broadband applicat~ons.

21 SVMMARY OF 'rHE ~NVENI'ION

23 The present invent$on 18 6urprislngly ~uccessful in 24 providing a method and apparatus for co~bining the functions o~ v~riou~ conductivity and dielectric constant device~ and 26 electro~agnetic energy coupling device~ into ~ single 27 devica, capable of oporating over a w~d~ rang~ of 2~ frequenci~. It is especially useful in medlcal 29 technology applicatlon~.

31 A measuring or electro~agnetic coupling tool, having a tool 32 face, also has a nov~l transmitting an~enna and a novel 33 rece~v~ny antenna~ Electro~agnetio energy i~ trans~itted to 34 a transmitting antenna. A stripline adapter permit6 the r 2~7~7 01 energy to flow to a striplins having a metallic central 02 strip. A strip face of the central strip is bent at 03 approximately right angles, and has a height that is 04 compatible with desired frequency coverage.

06 A ground plane extends ~rom the stripline adapter to the 07 right angle bend, so that a distal end of the central strip 08 extend~ away from it, and a void is created between the 09 center strip and the ground plane.

11 A dielectric is positioned to nearly fill the void. The 12 dielectric is comprised of a material h~ving a very high 13 dielectric constant and a very low energy lo~. The 14 transmitting antenna is positioned 30 that the ground plane 15 i8 fixedly connected to the measuring tool, ~nd the strip 16 face lies flu6h with th~ tool face, so that electromagnetic 17 energy can be transmitted into the material to be analyzed.

19 An enclosure surroundlng the strlpline i8 compr~sed of four metallic walls which ar~ po~itioned ln electrical contact 21 with the ground plane and the 6tripline adapter, so that the 22 strlp fac~ i5 ne~rly c~ntered in the open~ng created by the 23 walls znd the ground plane.

A loss-les~, non-conduct~ng material fllls in any remaining 26 open ~pa~ in-the enclosure, so that the non-conductinq 27 materi~l form~ an add~tional wall that i8 really flat with ~8 the strip face.

3~ A receiving antenn~ i8 co~prised in essentially the same 31 manner a~ the transaitting antenna, and is position~d in the 3a tool 80 that it can re~eive the electromagnetic energy which 33 has traveled through the ma~erial being probed. A means for 2~7~7 01 monitoring the received energy detects the phase and 02 the amplitude.

04 In another embodiment of this invention, broadband 05 measurements are taken to determine the quanti~y of a fluid 06 in a material, such as water in a lung.

08 It le one object of thi~ invention that electro~agnetic og energy ls trans~itted and received over a w$de frequency range, specifically from a few KHz to a few G~z. A commonly Il used frequency range is fro~ 2 R~z to 4 GHz.

13 The tool may further comprise a pad, which ~u~3tantially 14 conforms to thc surfac~ of the ma~l tls~u~, and hold~ the antennas. At lea~t one tranEmitting antenna i~ n~ce~sary.
16 No receiving antenna i8 n~cessary, although a plurality of 17 each 1~ often d~sirable.

19 The above and other embodiments, ob~ects, advantages, and zO features of the lnventlon will become mor~ r~adlly 21 apparent f~o~ th~ following detailed de~oriptlon of the 22 invention, which i~ provided in conn~ctlon with the ~3 accompanying drawing~.

D~:SCRIPTION OF THE DRAW~NGS

27 Flgure 1 1~ a ~ch~tic, ~ectional vi~w of thc inventlve 28 deviec po3~tioned ad~acent to mammal ti sue.

Figure 2 show~ a top, front, and side view of the novel 31 trans~itting antenna.

33 Figure 2A is the sa~e view as Figure 2, further illustrating 34 ~he enclosing ~etalllc walla.

2 ~ ~ 7 ~ 4 7 01 Figure 3 shows an antenna mounted on a tool face.

03 Figure 4 shows three graphs of transmission and return loss 04 as a function of frequency.

06 Figure S i8 a graph of transmission and return lsss as a 07 function of frequency, for low frequencies.

09 Figure 6 shows four graphs of ttme-dom~in tran~ission measurements at various distance fro~ a ~etal reflector 11 plate ln a brine.

~ 3 DETA~ED D~:SCRIPTION O~ THE ~NVISNT~ON

In accordance with the present invention, a neu l~proved 16 method and apparDtus for coupllng electro~agnetic ~n~rgy 17 into a material for determining the nature of various 18 materials and the fluids contained there~n and to induce 19 hyperthermia, u~ing a broadband ~easuring apparatus, has been developed.

22 Referrlng to the drawings, a fir~t ~bodi~nt of th~
23 in~entlve broadband tool 101 i8 ~hown ln r~gur~ 1, 24 position~d around a portion of a ~am~al body ~uch a~ a chest cav~ty 103. A m~an8 such as a belt moun~ 109 po~itions tool 26 faoe 111 n~ar th~ ma~l skin 104, such that tr~n~mitt~ng 27 antanna~ ~uch as Tl and T2 and receivin~ ant~nna~ ~uch as Rl 28 and R2 are po~ltioned touching the skin sur~ace of 104. The 29 tool fac~ lll is de~ined as the surfa~ of the b~lt mount 109 contaln~ng ~he ap~rture plan~ of the antennas, and 31 is preferably a continuou~ metall~c surface. The belt 32 mount 109 may b~ mado of any suitabl~ flexible ~at~rial that 33 ean be ctrapped around the portion of in~ere~t o~ the ~ammal 01 body. A conducting compound such a~ a conducting grease may 02 be applied at the interface 113 bet~een th~ tool face 111 03 and the skin surface 104 to improve coupli~g betwe~n the 04 antennas and the che~t cavity 103.

06 The region of the mam~l body to be inve~tigated ~ay not be 07 electrically homogeneous. In the ch~t oav~ty 103 for 08 example, there are organ~ such as th~ heart 105, th~ lung 09 region 106, the vQrtebra 107, and ther- ~y also b~ ~
10 tu~or 108. It i~ often deslrable to ~nalyz~ or treat 11 selected portions of suoh a cavity 103.

13 An analysis of the chest cavity 103, for exa~ple, can be 14 done by a dielcctric lmaging of tb~ c~vity. Thi~ i 8 don~ by transmltting electromagn~t$c energy at a ~ult~ble freguency 16 across th~ che~t cavity 103 froo a tran~-itting antenna such 17 as ~1, and receiving this energy ~t a r~c~iving antenna such 18 as Rn. In this way the phas~ and tbe amplitude of the 19 propagated electromagnetic w~ve for th~ path TlRn (shown in da~hed line) is deter~lned. Since ther~ ca~ b~ a 21 multiplicity of tran~mitting antenna~ Tn and a multiplicity 22 of rccelving ~ntenn~ Rn, ~ ~ultipl~clty of ~uch paths 23 crisscrossing the entire che~t cavity can b~ ~tudl~d. From 2~ this information, using well known t~chniq~e~, a dislectric image of th~ ch~t cavity can b~ generat~d. Such an image 26 display~ th~ v~riou3 organs in the ca~ity, and wb~n ~uitably 27 made, can r~vcal th~ presenco of tu~or loa. The dl~lectric 28 propertie~, and thus a dielectric i~age, can be deter~lned 29 as a function of po~ition within the ma~erial being probed.
Since diel~ctric i~agc is very s2ns~tive to tho pre~ence of 31 water, it can al80 give an a sess~ent of th~ lung water 32 content; C~. nMicrowavc Methods of Mea~uring Change~ ln Lung 33 Water~, by M. F. I~kander and C. H. Durney, Journa} of 34 Microwave Power, vol. 1~(3), 1983, p. 265.

2~7~7 01 Note that althouqh the antennas have been labeled as either 02 transmitting or receiving antennas, any given antenna can 03 serve either function.

05 The broadband capability of th~ antennas is an ~dvaneage in 06 the above applications for the following rea~on~:
07 structures (e.g., heart, tu~or) of different size~ require 08 different frequencie~ for their best definition in th~
og image; highly lossy region~ such as fluids ~y reguire employment of relatively low freguencies so that th~
11 electromagnetic losses are acceptable; in ti~e-do~in 12 application, simultaneous inform~tion at a ~ultiplic~ty 13 f frequencies can be developed.

In the trestment mode, it is desirable to reduce o~
16 ellmin~t~ the tumor 108 by hyperther~la, i.e., by 17 selectively heating only the tumor region 108 to a high 18 temporature. ~hus, by selecting a suitable group o~
19 antennas to tr~nsmit, one can select~vely deposit electromagnetic energy in the reglon of th~ tu~o~ 1~8; Cf.
21 "Two-dimensicnal Technique to Calculate th~ E~ Po~er 22 Deposition Pattern in tho Humnn Body~, by M. F. i~zder, 23 P. F. Turner, J. B. Du80w and J. Rao, Journal o~ Micro~av~
24 Pow~r, v~l. 17(3), 19~2, p. 175.
~5 26 The broadband capability of the antenna~ ~ 5 ~n advantag~ in 27 the abov~ application because for a given situ~tion, one c~n 2B select the fr~gu~ncy that simultaneou~ly produco~ th~
29 optimum depo~ition of power and localization of th~ beating using known technlques.

32 An exa~ple of the inventive trans~itting antenna 15~ is 33 shown in Figure 2. A coaxial connectin~ means, such as ~7~7 01 coaxial connector 151 is electrically conneeted to a 02 stripline adapter 153 which is capable of transmitting 03 electromagnetic energy from the coaxial connector 151 to a 04 stripline section with metall~c central strip 155. An 05 especially useful stripline adapter is a model No.
06 3070-1404-lD designed by Omni-Sp~ctra, or other types of 07 microwave stripline adapters. Other types of tran~is~ion 08 means may be utilized to transmit electromagnetic energy to 09 the antenna. For example, a strip transmisslon line may be electrically connected to the stripline section having the 11 metallic central strip 155. As a com~ercial 12 coaxial-to-stripl~ne transition means has been utilized, the 13 d$menslons included herein reflect thi~ mean~. One 14 knowledgeable in the art would realize that the dimens~ons ~ay be altered to change frequency coverag~
16 and to fine-tune performance.

18 Metallic center strip 155 has a front end 157, a flat strip 19 body 159, a flat strip face 161, and a distal end 163. The front end 1~7 18 electrically connected to the e~ter 21 conductor 169 of the striplin~ adapter 153. Solder i~ a 22 particularly useful connecting means. Flat strlp body 159 23 may al~o be tapered to eom0 to a point at front ~nd 157 to 24 provido a s~ooth electrical tran~$tlon betw~en th~ center conductor 169 and the center strip 155. Th~ strlp face 161 26 i8 b~nt at app~oximately right angl~s to strip body 159, and 27 ha~ a helght that i~ mea~ured from the right angle bend to 28 di~ta~ end 163. The height is compatible with th~ desired 29 frequency cover~ge. The longer the helght, the ~ore lower frequ¢ncy coverag~ is allowed. A ~" height permit~ a 31 frequency rang~ of approximately 2 KHz ~ 1 GHz. A Sm~
32 he$ght extends the upper frequency limit to approximately 33 2 GHz. An upward frequency limit of 4 GHz is attainable as ~7~3~7 o1 well. The metailic center strip 15S can be made of any 02 metal. Copper, brass, or aluminum are especially useful.

, 04 A ground plane 165 extends fro~ stripline adapter 153 to the right angle bend in the center strip 155, so that the distal 06 end 163 extends away from the ground plane 165 and so that a 07 void exists between the center strip lSS and the ground 08 plane 165. Ground plane 165 ls comprised o~ a ~etal.
Commerclal grade stainle s steel ls particularly useful. ~t is desirable to keep the ground plane and center ~tr~p a~
11 short at pos~ible, to permlt the appar~tus to re~ain a~
12 compact as po~sible and to allow the use of a~ many antennas 13 as possible.

lS The vold between the ~round plane 165 and th~ center 16 str$p 155 ~8 largely f$11ed wlth a dielectric 167. The 17 dielectr~c 167 should have a very h1gh dielectric constant 18 and a very low 1055. 3y loss, w~ mean the dissipation of 19 energy. The dlelectric 167 can be a cera~ic di~lectric, and comprised of mat~r~al such as ~ariu~ Tltanate or ~ad 21 2irconate T~tanate. A cryst~lline dielectric may also be 22 used, although ~ore exp~ns~v~. The thicknes~ of th~
23 dlelectrlc 167 i~ deter~ln~d by th~ ~tr~pl~n~ ~d~pter 153 24 used. The d~electric 167 acts to m~k~ the c~paeltanc~ of the center str~p 155 very large.

27 The conat~uction o~ th~ antennA i5 comploted by ~nclosing 2~ the cent~r strlp 155 by met~llic w~115 181, 182, 183, and 29 184, wh~ch contact the ground planc 165 and th~ adapter 153 electrically, as shown in Figure 2A. The walls add rlgidity 31 and prev~nt le~ag~ 3~ the electromagnetlc radiatio~. The 32 strip face 161 i8 approxi~ately cen~ered in the r~c~angular 33 opening created by the edge3 of the walls and the ~dge of 34 the ground plane 165. Thus, the dl~tance betwe~n an edge of ~ t7 01 the strip face 161 and the adjacent edge of a wall is 02 substantially the thickness of the d$electric 167. The 03 entire void space in the antenna enclosed by the walls, 04 including the set back 168 at the dielectric edge, is filled 05 with a loss-less, non-conducting material such as a mixture 06 f epoxy and alumina which sets hard, seals the antenna, and 07 makes it more rugged.

og The ground plane 165 and the walls 181, 182, 183, and 1~4 are fixedly connected to an electromagnetic coupling or 11 analyzing tool as seen in Figure 3. The strip face 161 is 12 positioned to lie flush with the tool face 171 (whlch is the 13 sa~e as the tool face 111 of Figure 1), so that the 14 transmitting antenn~ 150 can transmit electro~agnetic energy into a material such as mammal tis~u~. A conductive 16 6ubstance, known in the art, i 8 usually placed on the 17 outside of the mammal ticsue, to permit a suff$cient flow of 18 eloctromagnetic en~rgy into the tlssu~. Void space 173 is 19 filled with a loss-less~ non-conducting m~terial such as an epoxy-aluminum compound. The ground plane 165 and the walls 21 181, 182, and 1~3 connect to th~ tool fac~.

23 A receiving ele~tromagnetic antenna is comprised in 24 essentially the same manner as the transmittinq antenna, and is positloned in th~ tool in th~ same manner as the 26 transmitting antenna, so that the receiving antenn~ can 27 receive the electromagnetic ener~y whlch has t~av~led 28 through the ~aterial that is analyzed.

The pre~ent invention is especially useful in the field of 31 microwave diagnostics of fluid conten~ and flu~d quantlty.
32 For example, the apparatus can coupl~ electromagnetic energy 33 into ~ammal tiSBUe. The electromagnetic energy can be 34 monitored to provide an indication sf th~ amount ~nd 2 ~ ~i 7 ~ ~ 7 01 distribution of a fluid, such as water, in~ide the mammal 02 tissue. One particularly useful applic~tion is to measure 0~ the water content in a lung. The present apparatus is very 04 compact, and therefore requlres a much smaller skin contact 05 area. AlSo, many antennas can be placed on a ehest cavity, 06 to obtain a well defined image of the chest cavity. The inventive antennas can be ~athematlcally d~scribed as a 08 point source, thus making analysis of the data easier. A
0~ conductive 6ubstance should bc pl~ced on thc outsid~ of the chest cavity, to permit a ~ufficient flow of electro~agnetic 11 energy into the chest cavity.

13 The prior art (Iskander et al.) has the drawbac~ that the 14 electric field vanishes ~t so~e distanc~ froa th~ tool face, since the fields in the two parallel ~lots ar~ oppositely 16 directed. No such cancellation occurs with the present 17 invention. Furthermore, the incorporat~on of a resi tor in 18 Iskander et al's antenna introduces a powcr limit~tion.

In another embodiment, the pre~ent inventio~ ca~ be used in 21 the field of microwave hyperth~r~ia. Th~ ~pparatus can 22 couple electrom~gnetic energy into the interior portion of a 23 mammal, so th~t the electromagnetic energy i3 focu~ed to 24 he~t and thereby reduc~ the size of or destroy a tu~or.
Tumor reduction therapy or cancer therapy, by hyperthermia, 26 co~bined with radiation or drugs is known in the art to 27 eith~r stop or slow down the growth of cancer c~ , or 28 cau~ th~ de~th of the cancer cells.
2g The present invention has the advan~age over the prior art 31 that many frequeneies can be selected. B~caus~ there is no 32 limitation to the power handling capability in the inventive 33 antenna, the present invention is particularly suited for 34 depositing microwave power into a locali~ed area inside a .3 ~ 7 01 mammal, such as a human. Either a single antenna or an 02 array of antennas could be used.

04 In yet another embodiment, the apparatus can be iDplanted 05 inside the body of a mammal, and used as a radio frequen~y 06 antenna. Either a single antenna or an array of ~ntennas 07 could be used. As the inventive antenna c~n be ad~ very 08 small (as small as approxim~tely 10 m~ long and 09 approx~mately 5 mm high), it is particularly ~uitDbl~ to this application. As the antenna get~ smaller, the 11 frequency coverase shifts to higher frequencles. The 12 apparatus can be constructed with a comm~rcial ~cro-coaxial 13 connector. However, smaller devices can be oonEtructed 14 through the use of a custo~ized coaxial connector~
16 The apparatus can operate in the frequency domain~ u~ing a 17 single frequency, multiple frequencies ~such as 18 simultaneous, selectable, or time-multiplex~d fo~ example~, 19 or swept frequency techniques. Or, th~ apparatu~ can operate ln the time domain, usin~ pulse~ of a wid~ variety 21 of shapes, widths, rise and fall times, etc. Whe~ thc 22 pulses are transformed to the frequency do~ain, eit~er 23 electronically using a spectrum analyze~, oe nus~ric~lly 24 using mathe~atical ~ransfor~s, the sam~ infor~at~on i5 obtained as would be given by a frequency do~ai~ tool.

27 A prototypc tool was constructed, with the inventiv~
~8 antenn~s. The tool consists of one transmitting and one 2g receiving antenna, the distance between the~ bei~g variable.

31 An acceptable dielectric antenna ~ust meet the following 32 criteria:

2 ~ 1 7 01 (i~ It must be able to couple sufficient energy into 02 and from the material at its operating frequency 03 to allow probing of the material;

05 ~ii) This probing energy must penetrate into the 06 material, rather than clinging to the ~urface of 07 the tool (i.e., it must trav~l as a freely 08 propagating wave rather than a surface wave guided 09 along the tool face).

11 In the present instance, the above two conditions must hold 12 over the entire range of the frequency of op~rat~on.

14 The first of the above criter~a i8 ~ested by mea~uring the return los~ for th~ tran6mltting antenna, and th*
16 transmi~slon 108s from the trans~ltting to the receiving 17 antenna - both a6 a function of frequency. These 18 measurements are shown in Figure 4 where the tool i8 placed l9 in air and again~t br~ne of conductivity 0.5 mho/~ (to rep~esent a biologioal medium). The return loss curve in 21 brine shows that sufficient energy is entering the brine 22 over the frequeacy r~nge of the measuring devic~
23 (Hewlett-Pack~rd HP~505A Network Analyzer; 500 K~z -24 1300 MHZ) to pormit probing. The tran~$sslon logs ~hows that sufficient energy i5 being received at the r~ceiving 26 antenna to permit measurements.

28 Measurements were made by using another ~easuring device 29 (~P3577~ Network Analyz~; SHZ - 200 MHz) to test the low frequency li~lt~tion o the antenna. The re~ult~ are shown 31 in Figure 5, showing that the low frequency limitation is 32 a~out 5 KHz. The improved return loss performance in ~he 33 200 MHz region (a~ Figur~ 4) results fro~ a drylng tcuring) 34 of the epoxy alumina fil}ing between measur~ent~.

7 ~ ~ 7 01 Figure 6 shows time-domain transmission measurements at 02 various distances (d) to a metal reflector plate in the 03 brine. The change in amplitude of the received pulse as a 04 function of the distance of the metallic refleetor shows 05 that the energy has penetrated into the brine out ~o the 06 location of the plate.

oa While a preferred embodi~ent of the invention ha~ been og described and illustrated, it ~hould be appar~nt th~t ~any modification~ can be made thereto without dep~rting fro~ the 11 spirit or scope of the invention. Accordingly, the 12 invention is not li~ited by the foregoing de~cr~ptlon~ but 13 is only limited by the s~ope of the clai~s appended hereto.

1~

Claims

1. Apparatus for coupling electromagnetic energy into materials comprising a measuring tool having a tool face, said measuring tool further comprising an electromagnetic transmitting antenna, said transmitting antenna further comprising:
(a) a coaxial cable connecting means and means to transmit electromagnetic energy therethrough;
(b) a stripline adapter capable of transmitting electromagnetic energy from said coaxial cable connecting means to a stripline having a metallic central strip, said center strip having a front end, a flat strip body, a flat strip face, and a distal end, said front end electrically connected to a center conductor of said stripline adapter, said strip face bent a approximately right angles to said strip body and having a height measured from said right angle bend to said distal end that is compatible with a desired frequency coverage;
(c) a ground plane which extends from said stripline adapter to said right angle bend, so that said distal end extends away from said ground plane and so that a void exists between said center strip and said ground plane;
(d) a dielectric largely filling said void, said dielectric comprised of a material having a very high dielectric constant and a very low energy loss, so that said transmitting antenna is positioned so that said ground plane is fixedly connected to said measuring tool and said strip face is positioned to lie flush with said tool face so that said transmitting antenna can transmit electromagnetic energy into said material;

(e) an enclosure surrounding said stripline comprising four metallic walls, said walls positioned in electrical contact with said ground plane and said stripline adapter, so that said strip face is nearly centered in the opening created by said walls and said ground plane;

(f) a loss-less, non-conducting material which fills in any remaining open space in said enclosure so that said non-conducting material forms an additional wall that is nearly flat with said strip face;

(g) said receiving electromagnetic antenna comprised in essentially the same manner as said transmitting antenna, said receiving antenna positioned in said measuring tool in the same manner as said transmitting antenna, so that said receiving antenna can receive said electromagnetic energy which has traveled through said material;
and (h) means for monitoring the amplitude and the phase of said received electromagnetic energy.

2. Apparatus as recited in Claim 1 further comprising a means for positioning said tool face near said material.

3. Apparatus as recited in Claim 1 wherein said electromagnetic energy is focused to heat and thereby reduce the size of a tumor in a mammal.

4. Apparatus as recited in Claim 1 wherein said electromagnetic energy is focused to heat and thereby destroy a tumor in a mammal.

5. Apparatus as recited in Claim 1 wherein said antennas are positioned on a belt-mounted device.

6. Apparatus as recited in Claim 1, further comprising a plurality of receiving antennas.

7. Apparatus as recited in Claim 6 further comprising a plurality of transmitting antennas.

8. Apparatus as recited in Claim 7 wherein said materials are mammal tissue and water.

9. Apparatus as recited in Claim 1, wherein broadband measurements are taken to determine said dielectric properties as a function of position within said material.

10. An apparatus for coupling electromagnetic energy to determine the quantity of a fluid in a material, said apparatus having a tool face and further comprising a first electromagnetic transmitting antenna, said first transmitting antenna further comprising:

(a) a coaxial cable connecting means and means to transmit electromagnetic energy therethrough;

(b) a stripline adapter capable of transmitting electromagnetic energy from said coaxial cable connecting means to a stripline having a metallic central strip, said center strip having a front end, a flat strip body, a flat strip face, and a distal end, said front end electrically connected to a center conductor of said stripline adapter, said strip face bent at approximately right angles to said strip body and having a height measured from said right angle bend to said distal end that is compatible with a desired frequency coverage;

(c) a ground plane which extends from said stripline adapter to said right angle bend, so that said distal end extends away from said ground plane and so that a void exists between said center strip and said ground plane;

(d) a dielectric filling most of said void, said dielectric composed of a material having a very high dielectric constant and a very low energy loss, so that said first transmitting antenna is positioned so that said ground plane is fixedly connected to said logging tool and said strip face is positioned to lie flush with said tool face so that said first transmitting antenna can transmit electromagnetic energy into said material;

(e) an enclosure surrounding said stripline comprising four metallic walls, said walls positioned in electrical contact with said ground plane and said stripline adapter, so that said strip face is nearly centered in the opening created by said walls and said ground plane;

(f) a loss-less, non-conducting material which fills in any remaining open space in said enclosure so that said non-conducting material forms an additional wall that is nearly flat with said strip face;

(g) said receiving electromagnetic antenna comprised in essentially the same manner as said transmitting antenna, said receiving antenna positioned in said apparatus in the same manner as said transmitting antenna, so that said receiving antenna can receive said electromagnetic energy which has traveled through said material; and (h) means for monitoring the amplitude and the phase of said electromagnetic energy, so that the quantity of said fluid can be determined.

11. Apparatus as recited in Claim 1 or 10 wherein said transmitting antenna transmits and said receiving antenna receives electromagnetic energy over a frequency range of 2 KHz to 4 GHz.

12. Apparatus is recited in Claim 1 or 10 wherein said transmitting antenna can alternately function as a receiving antenna and said receiving antenna can alternately function as a transmitting antenna.

13. Apparatus as recited in Claim 12 further comprising a belt-mount, said belt-mount substantially conforming to the outside of a mammal tissue and holding said transmitting and receiving antennas.

14. Apparatus as recited in Claim 13 further comprising a plurality of receiving antennas.

15. Apparatus as recited in Claim 14 further comprising a plurality of transmitting antennas.

16. Apparatus as recited in Claim 10 wherein said fluids are water.

17. Apparatus as recited in Claim 1 or 10 wherein said ground plane is no greater than 10 mm in length.

18. Apparatus as recited in Claim 1 or 10 wherein said strip face has a height that is no greater than 5 mm.

19. Apparatus as recited in Claim 1 or 10 wherein said electromagnetic energy is monitored to provide an indication of the amount and distribution of a fluid inside mammal tissue.

20. Apparatus as recited in Claim 1 or 10 wherein no receiving antenna is incorporated.

21. Apparatus as recited in Claim 1 or 10 wherein said apparatus is implanted inside a mammal, as a radio frequency antenna.

22. Apparatus as recited in Claim 21 wherein said apparatus does not incorporate a receiving antenna.

23. Apparatus as recited in Claim 1 or 10 wherein a strip transmission line is electrically connected to said stripline, so that electromagnetic energy can be transmitted thereto.

24. Apparatus as recited in Claim 10 wherein said nature of said fluid is determined as a function of position in said material.

25. Method for coupling electromagnetic energy into materials comprising the steps of:

forming a measuring tool having a tool face, an electromagnetic transmitting antenna and a receiving antenna, said transmitting antenna further comprising:

(a) a coaxial cable connecting means and means to transmit electromagnetic energy therethrough;

(b) a stripline adapter capable of transmitting electromagnetic energy from said coaxial cable connecting means to a stripline having a metallic central strip, said center strip having a front end, a flat strip body, a flat strip face, and a distal end, said front end electrically connected to a center conductor of said stripline adapter, said strip face bent at approximately right angles to said strip body and having a height measured from said right angle bend to said distal end that is compatible with a desired frequency coverage;

(c) a ground plane which extends from said stripline adapter to said right angle bend, so that said distal end extends away from said ground plane and so that a void exists between said center strip and said ground plane;

(d) a dielectric largely filling said void, said dielectric comprised of a material having a very high dielectric constant and a very low energy loss, so that said transmitting antenna is positioned so that said ground plane is fixedly connected to said measuring tool and said strip face is positioned to lie flush with said tool face so that said transmitting antenna can transmit electromagnetic energy into said material;

(e) an enclosure surrounding said stripline comprising four metallic walls, said walls positioned in electrical contact with said ground plane and said stripline adapter, so that said strip face is nearly centered in the opening created by said walls and said ground plane;

(f) a loss-less, non-conducting material which fills in any remaining open space in said enclosure so that said non-conducting material forms an additional wall that is nearly flat with said strip face;

(g) said receiving antenna comprised in essentially the same manner as said transmitting antenna, and positioned in said measuring tool in the same manner as said transmitting antenna, so that said receiving antenna receives said electromagnetic energy which has traveled through said material;

interconnecting said measuring tool with a means for monitoring said electromagnetic energy whereby said dielectric properties can be measured; and interconnecting said measuring tool with a source of electromagnetic energy.

26. Method as recited in Claim 25 further comprising a means for positioning said tool face near said material.

27. Method as recited in Claim 25 wherein said electromagnetic energy is focused to heat and thereby reduce the size of a tumor in a mammal.

28. Method as recited in Claim 25 wherein said electromagnetic energy is focused to heat and thereby destroy a tumor in a mammal.

29. Method as recited in Claim 25 wherein said antennas are positioned on a belt-mount device.

30. Method as recited in Claim 25 further comprising a plurality of receiving antennas.

31. Method as recited in Claim 30 further comprising a plurality of transmitting antennas.

32. Method as recited in Claim 31 wherein said materials having dissimilar dielectric properties are mammal tissue and water.

33. Method as recited in Claim 25 wherein said broadband measurements are taken to determine said dielectric properties as a function of position within said material.

34. Method for coupling electromagnetic energy to determine the quality of a fluid in a material, comprising the steps of:

forming an apparatus having a tool face, an electromagnetic transmitting antenna, and a receiving antenna, said transmitting antenna further comprising:

(a) a coaxial cable connecting means and means to transmit electromagnetic energy therethrough;

(b) a stripline adapter capable of transmitting electromagnetic energy from said coaxial cable connecting means to a stripline having a metallic central strip, said center strip having a front end, a flat strip body, a flat strip face, and a distal end, said front end electrically connected to a center conductor of said stripline adapter, said strip face bent at approximately right angles to said strip body and having a height measured from said right angle bend to said distal end that is compatible with a desired frequency coverage;

(c) a ground plane which extends from said stripline adapter to said right angle bend, so that said distal end extends away from said ground plane and so that a void exists between said center strip and said ground plane;

(d) a dielectric largely filling said void, said dielectric comprised of a material having a very high dielectric constant and a very low energy loss, so that said transmitting antenna is positioned so that said ground plane is fixedly connected to said measuring tool and said strip face is positioned to lie flush with said tool face so that said transmitting antenna can transmit electromagnetic energy into said material;

(e) an enclosure surrounding said stripline comprising four metallic walls, said walls positioned in electrical contact with said ground plane and said stripline adapter, so that said strip face is nearly centered in the opening created by said walls and said ground plane;

(f) a loss-less, non-conducting material which fills in any remaining open space in said enclosure so that said non-conducting material forms an additional wall that is nearly flat with said strip face;

(g) said receiving antenna comprised in essentially the same manner as said transmitting antenna, and positioned in said apparatus in the same manner as said transmitting antenna, so that said receiving antenna receives said electromagnetic energy which has traveled through said material;

interconnecting said measuring tool with a means for monitoring said electromagnetic energy whereby said nature of said fluid can be determined; and interconnecting said apparatus with a source of electromagnetic energy.

35. Method as recited in Claim 31 or 40 wherein said transmitting antenna transmits and said receiving antenna receives electromagnetic energy over a frequency range of 2 KHz to 4 GHz.

36. Method as recited in Claim 25 or 34 wherein said transmitting antenna can alternately function as a receiving antenna and said receiving antenna can alternately function as a transmitting antenna.

37. Method as recited in Claim 36 further comprising a belt-mount, said belt-mount substantially conforming to the outside of a mammal tissue and holding said transmitting and receiving antennas.

38. Method as recited in Claim 37 further comprising a plurality of receiving antennas.

39. Method as recited in Claim 38 further comprising a plurality of transmitting antennas.

40. Method as recited in Claim 39 wherein some of said antennas are positioned on said tool face and some antennas are positioned on said belt-mount.

41. Method as recited in Claim 34 wherein said fluids are water.

42. Method as recited in Claim 25 or 34 wherein said ground plane is no greater than 10 mm in length.

43. Method as recited in Claim 25 or 34 wherein said strip face has a height that is no greater than 5 mm.

44. Method as recited in Claim 25 or 34 wherein said electromagnetic energy is monitored to provide an indication of the amount and distribution of a fluid inside mammal tissue.

45. Method as recited in Claim 25 or 34 wherein no receiving antenna is incorporated.

46. Method as recited in Claim 25 or 34 wherein said apparatus is implanted inside a mammal, as a radio frequency antenna.

47. Method as recited in Claim 46 wherein said apparatus does not incorporate a receiving antenna.

48. Method as recited in Claim 25 or 34 wherein a strip transmission line is electrically connected to said stripline, so that electromagnetic energy can be transmitted thereto.

49. Method as recited in Claim 40 wherein said quantity of said fluid is determined as a function of position within said material.