. . 

,-. . 

. I. - . 

. , - 3 

.. . - ?: .. 1-1 

: .,>,r , ., -' . -. -- -4:. . . 

..a. 

1 -. - %- . -, ;, -.-. ;*f:<;-;.+- :-- . -7. 

" ;-< - A.R.F. PRODUCTS - ING"?'.- -', .. . ! -i-x ,. 0; .. I '. . . .-:.A?->> . * ..--7c*,. - -+ 2- -. .i . - L 

ENGINEERS AND MANUFACTURERS OF PREGIS~PNPLEF~R~N~C EQUIPMENT , 

. >':...p.; 'L;;& !, ,-:a- + 2 

- "... *=.!<. :: .,.. $,?.--: ' - . ' ,. -..< x 

- -*?. -- .. -- . > -- ., - 

*-- .. - -.. ~;;$J.:,~+.;~>.f -: y:: - ', .;:, . . . .:*.- r. .: . - -, :* ?<: - :.; ., d 

, .: +,:.. -' 

-1 . . . 

NUMBER Nrn 

PERIOD ENDING -. 

30 SEPT, 1980 

MINE WIRELESS COMMhTNXCAZTION SYSm 

HQME OFFICE AND MANUFACTURING PUNT - RATON, NEW MEXICO 

RESEARCH AND DEVELOPMENT LABDRATORY - BOULDER, COLORADD 
A.R.F. PRODUCTS, INC. a Raton, New Mexico 

Boulder, Colorado 

NO. ?Q.l!i.9. ........ 

PAGE ............ 0 

DATE $9 .Sbpt... !?8.( 

ISSUE ............. 

DOCUNENT NO. 3015/9 

F10PXl ILY TEC HN ICAL LETTER REPOXT 

NUMBER NINE 

PERIOD ENDING 30 SEPT. 1980 

DEL'ELORGKT OF DEZIDNSTRATION 

l:ARD\JffiE FOR ?IEDIUM FREQUENCY 

MILE WIRELESS COM3IUKICATION SYSTEY 

PREPARED FOR 

W'ITED STATES DEI'AREENT OF TlE IYTEEIOR ' 

RLW3 OF MI?;ES 

4800 FORRES AiTNUE 

PIirSBLXGH, PA 15213 

I 

a 

, - 1 -;-'. 2 "p- i.r. BY : --- - 1 

Larry G. Stolarczyk, Sc.D. 

Director of Research 
A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

Boulder, Colorado 

NO. ?out, 9. .. 

PACE ........... OP 

DATE 30 S~P; >8Q . 

I 

.............. 

I 1, \.IlPJILESS ?IF CO?W.Ut;ICATTCiN SYSTEI',I (1 ISSUE 

I 

TABLE OF CO;;;E';'L~S 

Page 

EilECLPT7VE SLI?G 'fl.:'........................................... 1 

............................... 1 PROWSS A:ID STAT:.% (Pi'nSE I) 2 

1.0 INDUCED 'ROLI3Y WIRE SIGKALS.. .......................... 6 

1.1 1UNSYISS ION LII-T C"RTE:;T TO RECE IV ISG LOOI' A:;TE:3A 

SIGNAL LELEL TI'A:?S:-'EI: FUNCTION.. ...................... 13 

1.4 FREE SPACF: SPilERIUL PKOl'ArATIOt;. ...................... 16 

1,h.l Design of Coupled Resonator :.oop Antenna . . ,ietmrks.. ...................................... 33 

Appendix A 3 7 

Appendix B 3 S 

A.R.F. PRODUCTS, INC. 

Raton. Scw Mexico 

Boulder, Colorado 

NO. 391.5.. 9. ........ 

PAGE . 1. . 0 

DATE 30 Sept, I;S! 

ISSUE ............. 

TYPED I 

?:inin2 ?eseenrcL? 

?'ine Jieal t:~ and Safety Research 

for 

I'criod Endirg 30 Septer!her 1'180 

-- i-'F,O(;::A\' Wireless ."F Ca-mun ica t ion Sys te:.~ 

C S tllnii :. ':ol ton, .Tr. ("r- Patrick ::c;?r..) - 

~i. 3. 1 :levt.lopr~ent of de. ;ens Erst i )n '.rrdwnr;.'ft>r 

ricdi'ln ireq:~c::c:. I-.i::e wireless cd:u-i:lr:ic;ltiol~ s:.stc-.:. 

RECKED 1 

I 

'PROVED I 
A.R.F. PRODUCTS, INC. 

Katon, Sew Mexico 

Boulder, Colorado 

NC. . . Klj! .$. . . . . . . . 

PAGE . . .2. . . . . . . OE 

DATE .?Q..S.~.P~~.!

, 

TlTLE \JI RE1 ESS \T CO?C!1':;1 C"\ FION SYS 13:' 11 ISSUE . . . . . . . . . . . . 

I 

I 

TYPED 

HECKED 

1'I:OGRESS A:;D - STrl l"S (Pl,ASE I) 

Tile signal levels appenring at tile receiver f :+I) input terminal linve 

been determined for tile following signal transrnj ss ion nedirms: 

Tr nnsmis s ion n~ed i urn - 

':rollcy wire 

Transrliss ion mode 

Trnnsc:iss ion l inc (trolley wire to 

track separation of 3 meters) 

'C power dis tr i5rtt ion cnble Tra~lsniss ion 1 ine (conductor separation of 0.(1& meter) 

;'elep!ionc lines ?.. ~rnnsr~issi~m 1 ine (condilctor separation of G.04 i;~eter) 

Ccl lrtlar Coal sea:.^ :lode 

., :tie signc:l leveis ii:.;.e 'wen deter~.rintd for loop to loop via tile line 

(LLI,) conn\lnic;lt ians, :. well ns for 1 I I ct>,~r?.~:~i~ations links that rise 

pnssagewpy repenter s . Znssa~cwa\ repeaters are directly conncc ted to 

t!le tr,?ns::liss ion 1 ine to e:l!ia~~cc? t.~e call in,; range by s igiificantly 

increasing the s ignnl c.:rrent on tile trnrisziss ion line. 

.i~e cel lrll~r camnunlcat lox sys ten signal lc:.els !lave been dc terrnined 

by i~sing tile measured field strenzth tfotn fro[;; tile I1.S.B '.'. Collins 

(110 36602d) and ADL iiiO j4: 06~) repor ts 

Sear in mind tlirrt t!ie signal level estiintions have been made on tlie 

basis of a well beilavcd transmission line struct~rre, In practice, 

insertion and nissr;~ntch loss will degrade t:!e expectation. 
A.R.F. PRODUCTS, INC. 

Raton. Sew Mexico 

Boulder, Colorado 

/TITLE WIRELESS ?:F co?P!L!?:I CA~I~:; S'iS I%?\ 11 ISSUE . . . . . . . . . . . . . 

- 

I 

I 

< 

I This report adds to the current body of under,rorincl comunication system I 

I 

I dzsign knowledge by: 

I 

NO. .?91s,.(r. . . . . . 

PACE . .2. . . . . . . 0: 

DATE )V . ScR ... .1::4( 

* accurately defining (xeast~r ins) t!;e 12 dn S I!;PD sensitivity 

of the sys ter.1 recc ivcrs and t!~en s tn t in% tile equivalent rnagne t ic 

field strength (ifs) in uAlm; 

* showing tl~at when a passageway repeater is used in loop to loop 

via the line communication link tliat tile rcceived signal level 

dependence on line current is onl?~~tile first power of distance; and 

* maximizing t!le transinit mar,net ic -:o:.a,,:lt :i) is extrenely i!?portant in tlle desizn of tile transr:it nnte;lna network. 

Since t!:e 12 dB SI';AD sensitivity of t ~c reccivcr is known to be 

one (1) microvolt, t'le r..pgnetic field (;is) r2qltircd to produce t:ie 12 d3 

SI!:AD signal can be acct~rately detcri.~i~:e~I ,:lils tile Hs data can be used 

I 

I to correct tile Colli~is seam node range e::pec tation. At COO k!iz, !is ilas 

1 rt vnl~~c of -20 d7 re 1 uF/m, and dc-rac!c.s tc, -1 dii re lufilm at 60 k:,t 1 

'ilw received signal level (lV1) in a loop tc, loL)p \!is t!le linc corlmunica- 

\ 

t ion 1 ink has 3 t;l irJ power dependence or1 .i is t:,ilce t 2) as seen in t!lc 

following natl~e,:;nticnl represent at ion: 

5 is the sepnrntion distance of cond!lc tdrs in t11c transnission linc, 

I I and ARXR arc t!ie receiving loop anteqna :!~s i;n :araiietcrs. 

The signal level dependence on linc s:!rrc?nt and distance ik) is 

TYPED given by 

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A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

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NO. . .?0!j,.?. ...... 

PACE .. .f7. ....... 0' 

DATE ?o.sc?P.t:. .\?Q' 

........ 3'1TLE 1JTl:ELESS YF CO?C.I;'?;ICtlTION SYS I'E:! 

Since a passageway repeater can greatl:: increase line current, and the 

distant receiver signal level (VL) !ias only a first power dependence on 

1 distance (R) , t!ie " c a l l e d " t r a n s c e i v e r pat11 distance is greatly increased. 

The repeater will increase the "called" transceivcr distance from the 

transmission line by a factor of 2" over tile LLI. communication techniqi~e! 

;Ile passageway repeater also increases t!ie "calling" transceiver distance 

from the transmission line. Tile repeater receiver signal level has a 

second power dependence on distance. Tius till? "cnlling" range will not 

I I show t!ie dramatic iriprovement as seen in tile "called" range. 

TYPED 

HECKED 

'PROVED 

The sign21 level data presented in tilis report iras been noralalizcd by - 

a unit rna3net ic nioinent t 1 ampere - r:.eter2). Simply mu1 tiply t!le signal 

level data by tile actual transmit rioTllti>t (") to obtain (denormalize) 

the actual s i~nal level estimation. 

'i'he norlnalization met!~oci focuses attent ion on t!ic iaportance of the 

magnetic moment (:'). 11 strong factor in tile opti:-:ization of system performance is the ~axi~iization of for a qiven transi~iitter output power. 

'i'lte dependence of rnagnc t ic moment it:) on transrni t power (Po) and t!le 

series resistance IF ) of tile tuned loop antenna (ZL = Lj I>jQCk;T) is L 

3 ivcn by - 
FYPED 

IECKED 

A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

Boulder, Colorado 

NO. ,30151 9. ......... 

r PAGE .. .V ........ 01 

DATE .?o. Sep.t.0. .I?{ 

.............. 1 TITLE WIU1,ESS ?IF CON?IL?;ICtl'rlON SYSri'E?t II ISSUE 

I 

It is clear from the above equation tlint increasing power from 1 watt 

to 4 watts only increases t!te magnetic mor:~ent by a factor of two wit11 

RL held constant. ?: can be increased at any transnit power level by 

decreasing RL. However, t!iis optimization approacll is difficult because 

QCKT is constrained by the occupied bandwidt!~ of the narrow band F?i 

signal. 

Single tuned loop antenna structures cannot be optimized to increase 

magnetic moment above 1.6 ampere - reter' (Po = 4 watts). However, a 

niultiple pole-zero loop antenna can be used to increase ?: above 1.6. 

Yl~ere exists a conccrrl t::at :.T signals in t!ic vicinity of a blasting 

area will create 'razariloi~s situations. l"le induced cc~rrent in blasting 

cable is estimated to be n c4axir.lm of 50b microa~peres- 
IhTZCED 1T.OLIEY WIRE SIGKALS 

The trolley wire and rail will 

in many underground mines. 

! 

I A.R.F. PRODUCTS, INC. 

i Raton, New Mexico I 

I Boulder, Colorado I 

I I TITL.E \*!I hELESS >IF CO?.DILTST CATION SI'STE?! 

be used 

NO. ?P.l.S.i'. 9. ......... 

PAGE .. .6. ....... 0'1 

DATE ?u. Sep.b. 19.8.Q 

ISSUE .............. 

the 

i 

comiunicat ion media 

TYPED 

HECKED 

In this section, the signal level indtlced on the trolley wire and in 

t!le input circuits of a distant receiver by B first nan-pack transmitter 

will be determined. 

The work of Albert '1. Sr:lith Jr. and the !'.S. R.E.1, Arthur D. Little, Inc. 

report (Contract So. 346045 -- Section i'i') will be used to determine 

t!ie signal levels. 

Y11e trolley wire s ig~al transniss ion medium ( two wire 1 ine approxin~at ton) 

I will be excited by a circular loop witli t!:e geometrical aligmer~t s!~own 

I in Figure 1.0, 

Figure 1.0 The Aligned Geonetry 
.............. TJTLE WIRELESS !.IF COkIPIlrNT CATION SYS 'TEM 

The pllysical distairce between the trolley wire and track is b in meters 

and the dfstance beltween the loop and t?~e l Lne is R in meters, 

A.R.F. PRODUCTS, INC. I 

Raton. New Mexico 

Boulder, Colorado 

The inducea voltage source (emf) in the tua wire line is given by 

TYPED 

HECKED ' 

PPRQ~~ED 

I 

appears in Figure 1.1. 

5 *:,+ 

- + 

NO. 30151:y.. ....... 

PAGE . .7.. ....... 01 

 DATE^ .$ep~, -1980. . 

Figure 1.1 EQL'IZ'N,E::T T?J.:!S?:ISSI(I?: LINE CIRCUIT 

FOP. I?"JIl:CED VOLTAGES Ahi C I;W:;TS 

The induced transmission line current is given by 

0.1, volt 

----. . = 250 uk 

The magnet LC field at the location of the receiving loop may be 

I calculated as the vectarfally resultant field (same geometry as the 

I transmitting side) of contribution of the hm conductors. The geometry 
A.R.F. PRODUCTS, INC 

Raton, New Mexico 

Boulder, Colorado 

NO. . ~Y.L>,, Y. . . . . . . . . . . 

PAGE . . .&. . . . . . . . OF 

DATE 30. Ssfl., !?&P. . . 

I 

jT!TLE I4 IREI.ESS NF COFM~!lCATIOB SYSW\( )I ISSUE . . . . . . .. . . . .... 

I 

I The rna~netic field conponcnt from each current nay be calculated from 

om Far; 

tenna i Ls give 

then 

tase sou rcc (I emf) ir eceiving loop 

3 

where AR is CIIE (meters-) of the rcceivinz loop antenna, 

NR is the number of turns in rhe rcce iving loop antenna, and 

H is the rnngnc t lc field s treng ti] f a~pcrc,'m tcr) computed .from 

Eq~~at ion (3) 

1 

Table A sd~ows the value of the timed loop ontentla voltage source (emf) 

for different operating frequcncics for c~c!~ unit of magnetic moment (H), 

Table d 

Rcccivinr: Antenna 1.oap Voltage lVt) 

7 T 

?I = 1 ampere-net~~r'; b = 3 mtcrs; N 7 turns; A = 0.2 meters'; 

Fscquenc y 

kliz 

60 

300 

600 

h 

meters 

roo0 

1eoo 

500 

For coapleteness , Tablc S shows the magnetic tiomnt fur different transmitter output power lcvcls. 
AsRsFb PRODUCTS, INC* a 

Raton, New Mexico 

Boulder, Colorado 

NO. . 3.Q15i9.. ....... 

PAGE .. I$. ....... OI 

DATE ZQ .Sept.. 1980 

! 

.............. TITLE WIRE1,ESS ?F COMML~dlCATION SYSTE?l ISSUE 

I 

I 

TYPED 

Table B 

Transmitter Flagnc t ic ?lament (,'.I) 

N = 7 turns; BW ; 10 kllz; RL = 4.7 ohms 

output PW~ Transmit Loop Current Magnetic Ft 

watts ampere 

omclnt ampere -meter 

1 0.46 0,81 

4 0.92 1,61 

Tile signal voltase (VR) available at receiver input terminals ia dependent 

upon the voltage transfer function 

of the tuned loop antcnna. 

1 The tuned loop antenna network is shown in Figure 1.2. 

KT:-C,,F* . 

-. I f",. ..1, \. 

Figure 1.2 TUNED LOCP AX'L'ESSA NETWORK 

Assuming that the antenna is tuned and matc!~ed, the current flowing in 

the loop antenna is given by 2 

VL (emf) i = ----------- 

where the input impedance of the network (3) is real and equal to the 

tuned resistance (RL : WL/QCKT) of the loop antenna. 

* Bear in mind that maxhizin~ t!le transmitter loop antenna nagnetic 

rnoment rcd:ices tl~c value of PI,. 
A.R.F. PRODUCTS, INC. 

Ratoa, New Mesico 

Boulder, Colorado 

NO. .. .302$. 5 . 

PACE . .\0. ....... 0 

DATE .?? . Sept.. .!?; 

1 

............. 1 TI'S LE WIRELESS FIT CO>MUNGATION SYSTE?I 

i 

I 

The signal power dcliv~rcd to the input of the network (N) is 

For a matched 

:he recelver I 

signal pmr 

Lnput C 

dal ive 

!sa network (I 

cal to 

' the n~ 

plnnc 1 

IC ident 

INII _ 

and 1 u 

: power 

hence 

The receiver signal voltage (V ) can bc de ternfncd from Eqrtations (4) 

R 

fie receiver input signal voltage produccd by t!~c signals in Table A 

are sltown in TaSLc C. 
i A.R.F. PRODUCTS, INC. 

t Raton. Ncw Mex~co 

I 

I Boulder, Colorado 

NO. . .?Q1519. ...... 

PACE ... \ I ....... '0 

DATE ?Q . Sc PJ,. .IS18 

! ............. )'TITLE WIRELESS FlF COFi?IWICATIOK SYSTE?I I ISSUE I 

I 

Table C 

Receiver Input Signal (V ) R 

: 1 For each unit of magnetic moment, b = 3 meters 

r I Frequency I kllz 

6 0 

300 

600 

Receiver voltage 

PV 

2 7 

134 

270 

I It is interesting to note that the A.R,F. FX receiver achiever a SIN~ 

of 12 dB when the input signal voltage is 1 ul:. At 60 ktiz the communication system woald have a fade nargin of 29 dB. 

I Most of the U.S.B.M. measured data is given in terms of magnetic field 

strength H. Equation (11) can be used to determine receiver signal levels 

from the measure data. 

I The magnetic field required to aci~ieve t!:e 12 dB SINAD sensitivity is 

s iven in the table below. 

Table D 

>!apetic Field Strength (HS) required for 12 dB SIXAD 

Frequency 

kHz 

60 

. 300 

600 

It should be noted that t!re Collins report, "Propaqation of F?I Signals 

in Lhderground ?linesw (Contract HO 366026). defines the Collins mine 

I wireless radio sensitivity as .013 u A/?' at 520 kh. In view of Table 

D, the Collins sensitivity speculation is suspect. Appendix C (page 169) 
A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

Boulder, Colorado 

NO. . .3015r 9. ....... 

PAGE .. .\ 2 ...... O~ 

DATE .?O.Sie~.t.-..!? 

............. 1 TITLE WIRELESS MF COPUIUNTCATION SYSti'E>l 

I 

I of the Collins report develops equations identical to Equation (11). 

I I 

: 1 Because the A.R.F. receiver sensitivity (1' ) is olrcady known to bc 

I R S 

1 uV for a 12 dB SINAD, the calculation of llS is straight forward. I 

In the Collins case, 12 dB SIW sensitivitl. had to be calculated. 

Apparently an error has been made in tlieir Equntion (6). 

I In summarizing the results of this section, it is evident that voice 

quality communications can be es tahlished in loop-line-loop signal 

paths (see Tables C and D). The following relationship is useful in 

I estimating changes in loop- 1 ine - loop sy s tern performance. 

f2 

Eq:~at ion (12) provides tile following &use£ ul infomat ion: 

* the distant receiver signal levcl increases by VR pV (270 uY 

at 600 kllz) for cat!) unit increase in transmit magnetic nonent (!!); 

+: the transnission line current increases by 250 uA (at 60 kHz) 

for each tinit increase in transzit .-.agetic norrent ('1). From 

Eqrlations (1) and (3) t!~e line ctirrel?t increases with ttie first 

power of freq~~ency ; 

* tile signnl levcl (1.' ) increases witii t!~c second power of the r, operating frequency, 

* tho signal levcl (VR) increases wit11 tile trolley wire track 

separation distance (b) ; and 

;k the signal level decreases wit:; ti.e t'lird power of tlie distance 

(R) between t!lc trolley wire and tile loop antennas. 

I Bear in mind that the above analysis applies to a natc!~ed lossless 

transmission line. 
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Raton, Sew Mexico a 

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TITLE WJPELESS XF COPl~'L?~iUYION SYSEY 

I NO. . . ?QIS;.Y. . . . . . . . 

PAGE . .[3. . . . . . . . 'G 

I DATE ?@. Sep ter?, . .

 

ISSUE . . . . . . . . . . . . . 

' 1.1 'LM!:SEf ISSION LI:I CIIRE!:'; Tp I?ECE IVIXG LWI' A\.'iE:nA S IG3L LE1.'EI. TJAXSFER . 1 FLrNCTION (PASSAGE\JAY REPEATER) 

Eqilation (4) can be used to define the tumid loop antenna voltage (emf) i 

: I to line current transfer function as 

: I The received signal level increases with t!ie first power of frequency - - 

and decreases with the first power of distance (R). Kotlce t!~at in the 

loop-line-loop s ignel pat!) the signal level (VR) decreased with the 

third power of distance. 

A passageway repeater can be used to increase the callins distance from 

transmission 1 ine to the ~xhile transce ivcr. Tlic passageway repeater is 

s!lown in Figure 1.3. . - 

Figure 1.3 PASSACEiXY REPEATER 

T!:e passageway repeater will increase the line current to 

'20 ^Was 

i = ------. . = .447 anperes. 

= 100 ohms 

I'YPED 

Ylus the passageway repeater will enable cormunicat ions over significantly 

greater distances from the trolley wire line, 
A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

Boulder, Colorado 

1 NO. . .JUC>r Y.. . . . . . I PAGE . . .I4.. . . . . . OE 

I 

i \41 REIESS :.LT CO?!FlLh'lCATION SYSX?! 11 ISSUE . . . . . . . . . . . . . . 

I 

HECKED 

The passageway repeater increased tlie line current above the loop-lfneloop comunication case by 

0.447 ampere 

System Gain = -.-- - - . . . . . 

250 u Ampere 

Equation (13) sl\ows that the antenna voltage decreases by 6 dB for each 

doubling of range. *e listening range would increase by a factor of 21i. 

As a transmiss ion 1 ine receiver, the passageway repeater can be modeled 

,; cL, '. . as follows: l* .. 2- ' 71.- J..y 

v " ; \ '3 8-I l; 

Figure 1.4 PASSAGEWAY EEi'EATER 

Tlie 1ine:current con be es tinated to be 

The received signal level (VR) is given b: 

where T is the catching network transfer function. 

5c Estircated it111 wave rectification noike (i,O L' p-p on trolley wire) 

360 ?iz signal : 100 kliz, 248 ur'; 300 kiiz, 27.4 uV; 506 kliz, 9.9 u\'. 
A.R.F. PRODUCTS, INC. 

Raton, Sew Mexico I NO. . .3015i'9. . . . . . . . . 

PACE . .I5 . . . . . . . 61 

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TITLE WIRELESS MJ? CO!.PIUNICASION SYSTEM 

Equation (1) can be used to estimate changes in'system performance with 

changes in f, b, and R. 

DATE ?O. SW.~. *. .198C 

ISSUE . . . . . . . . . . . . . . 

I = 8.25 mV 

I Equations (1) and (2) can he used to estbate tile induced current in 

At 60 kl!z, the received signal level becomes 

tr 

0 

I blasting cables. Eqtlation (1) s!lows that t!ic induced current in a 

for each unit of magnetic noment (R = 1.5 meters, b = 3 meters). 

I blasting cable is dependent upon the cond~ctor spacing, distance to the 

transni t loop, nagne t ic nonent and freq:~cncy. 

Asstclin~ t!~e worst case, tile indi~ced current beconies 

= 502 microamperes. 

( It is believed tiiat this level of induced line c!~rrent is below the 

blasting ti~reshold. 

1.3 COLTLI!:G TO AC PO\EI: LI!;ES A:n> Ol'IER S?'AI,L CO?X)'_lCTOR SPACING S'lR'XTLRES 

T~ED I The loop-line-loop signal level for b = 0.04 meters conductor spacing 

is shown below. 
A.R.F. PRODUCTS, INC. 

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: 1 TITLE WIPSLESS -IF COEIEIIJSI CATION SYSTE?! 

I NO. .191519. . . . . . . . 

PACE . ./6. . . . . . . .' ( 

H DATE 39.Sep.t.. .19l 

ISSUE . . . . . . . . . . . . . 

Table E 

Receiver Input Signal fVR) 

:I For each unit of magnetic moment b = .04 meter 

Frequency 

kHz 

60 

300 

600 

Receiver Voltage 

uV 

0.36 

1.79 

3.6 

Above 300 kHz, AC power lines and other small conductor spacing structures i I 

will provide a suitable transmission medium. As was the case with. 

trolley wire, passageway repeaters will increase the system performance. 

1.4 FREE SPACE SPlERICAL PROPACATION 

Two geometries will be cons idered-the "aligned case" where only 4 

a (complex) exists and the "coplanar case" fiere only lf, exists. 

Intermediate directions create elliptic polarization where both and 

- 

]Ie exist. Then tlie magnitude of the major axis may be computed, which, 

with suitable orientation of the receiving loop, will give the best emf 

in the receiving loop, This complication will not be considered in this 

'YPED 

~ECKED 

analysis. The loop geometry is shown below. 2 

SOYGCE 

LGCP Figure 1.5 UjOP GEO?CETRY 

-1 

PROVED 

hc 
A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

, Boulder, Colorado 

NO. ... .3015i4 ..... 

PAGE ... I?. ...... 01 

DATE 30. ScP.t:. .1?R 

ISSUE .............. 

I The vector represerltation of the magnetic fields^^ are given by I - 1 

...... 1 ! 8 = 90' 

I i (19) 

p (~r)~ (~r)~] sin@=l 

I and ! - 

A 4fit i j 

- - -- - .. 17 8 = oO 

+ --.-3-" (20) * (Br) i cos8=1 i 

*("ihese components are calculated in the receiving situation shown 

w!~ere their respective maxima occur.) 

Values of the independent variable: have been deternined for the communication system and are shown in the following tables. 

PAFA'E TEFG 

Frequency kHz 

60 

5 00 

700 

r Rr 3 

meters radians H r 

I 

FIELD C0FIPO:;ENTS 1:: uA/m 

" (At 60 ki!z) 
r Br - 2 

meters radians Hr k? PrI liel 

(At 500 kl!z) 

10 .lo5 157.2 + J 16.5 77.74 + j 8.25 158 78.1 

100 1.05 ,157 + j .I65 -.008 + j .083 .227 .083 

500 5.25 .001 + j .006 -.Oli + j .03 .007 .017 

I 

I i A.R.F. PRODUCTS, INCo 

i Raton, New Mexico 

! Boulder, Colorado 

TITLE WIRELESS :.T COE.MINICATION SYSE31 

i 

(At 700 kliz) 

100 1466 .I59 + j .233 .09 + j .12 0.282 0.148 

NO. .?VC?i .y. ......... 

PACE .. !.? ....... OI 

DATE 39. SBC, .198( 

ISSUE .............. 

; I me voltage source in tlle receiving loop can be evaluated from 

I 

HECKED 

PPROVED 

F =, applicable 

_ . *-___ . 

r 

dB 

I 2 

I where H applicable is tile component of 11 wilfch tl~reads the loop in a 

direction nomal to its plane (time magnitude). 

By using Equations (LC) and (21), t!le value of receiver terminal voltases 

have been conputed and shown in the following table. 

Table F 

Receiver Input Signal (ITR) 

For each unit of magnetic moment RL = 4.7 ohms 

Distance Frcqilenc y 

meters k!lz 

Input Signal Voltage (uV) 

A1 igned Coplanar 

Tile table indicates that loop-loop comunicat ions may exceed LOO meters. 

Further, (all system parameters being equa1)the range increases with 

operating frequency. 
A.R.F. PRODUCTS, INC. 

Raton, Xew Mexico 

Boulder, Colorado 

NO. 3, .... 

PAGE .. I9 ....... 0 

DATE . 3.0 .Sc p t . . 12 

I ............. "TITLE WIRELESS COFIMUNICATION SYSTE?~ ISSUE 

I 

1 

1.5 COFMLNICATION SYSTE?I PERFORMANCE . By using prior U. S. R,M. mine comunications research data, the operating 

range and fade margins along the signalling paths can be determined. 

The maximum theoretical communication range (rm) at a given operating 

frequency can be determined by comparing the expected or measured signal 

level with either the measured or theoretical noise level. 

1 for the determination of the noise floor in a comunication system. The 

data applies in the "vicinity of several different locations in the mine." 

I At other locations, the noise signals are attenuated by tile appropriate 

propagat ion mechanism. I - - - - 

. . -. . -- - - 

The 12 dB SIWD sensitivity (Hs in dB re 1 d,n) ciiarocterisiic of the 

3 I A1 receiver (N=7. A=O. 2 m-) has been included on the measured noise data 

(ADL HO 346045) sllown on Figure 73. Figure 73 shows that in the vicinity 

of the noise sources, the ~ine generated noise will dominate the receiver 

1 

signal processing networks. Assuming that transnission line signal 

I propagation also exists in the vicinity. the expected signal level has 

also been included (;.1=1). The data shows t!lat LLI. communications will 

greater than 100 kFz. Tile data shows t!lat a noise operated squelch 

. . 

TYPED 

;HEcKED 

receiver design would be troublesome in many mine locat ions. The average 

mine noise representation provided by ADL (N-4-20 I.og10 (filG)) has bccn 
Planed Noise Levels Normalized to 12kHz Bandwidth - Measured with 1kHt 

\nstrumen:a;ion 9andwidth 

- - - Ven~cal Field Component 

- . - vertical Component - "Quiet Time" 

Horizontal Field Component 

McElroy Mine - Conrinuous Miner Section and Nearby Rail Haulagemy 

+. w Near end of rail haulage line 

e Near intersection of rail hauiaaeway and conveyor belt 

$ Near operating continuous mining machine 

r Near section power distribution center 

FIGURE 73 REPRESENTATIVE RMS MAGNETIC FIELD NOISE LEVELS 

MEASURED IN THE McELROY COAL MINE 

9 8 

-

b 

-30 - 

-40 , - tL R€CE\\I €R . t . N%7 

-50 , A= 0.2 MeTQr3 

-60 

-70 

- - - 

1 I 1 1 I 1 I I 1 1 * 

; 10 20 30 50 100 200 300 500 1,000 2,000 5.000 10,000 

Frequency in kHz 

Soure: r\iatior;at Bureau of S;andards (Ae?on NaSIR 74-389, June 1974) 
TYPED 

I the noise expected in an average mine. It should be noted that the 

A.R.F. PRODUCTS, INC. 

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TITLE WIRELESS b1F CO~DlLXICATION SYS?'E!I 

noise signal exhibits a l/f dependency (6 d~ per octave change). 

The signal levels appearing at other locations in the mine appear in 

the Colliris report (110 366028). 

1 

included to sl~ow that the P!cElroy noise data is about 10 dB less t5an 

i 

Representative data from the Collins report has been included for a 

NO. ... ?!.!?,.'I.. .... 

PACE . 21.. ...... 0: 

DATE ?.? .See!:. l?E 

ISSUE ............. 

range analysis purposes. By including the A1 receiver sensitivity (Hs) 

point on the appropriate signal character is t ic , the operating range can 

1 be determined (H=2.5). The appended Figr~re 26 shows that the range at 

I 

485 kHz will exceed 300 meters in the Robinson Run mine. Also, the A1 

receiver sensitivity may be better than the sensitivity of the "survey" 

receiver. That data may show that mine generated noise dominated the 

I 

survey receiver. Figure 2-10 seems to indicate that the survey receiver 

I has a slightly better sensitivity. The d~t3 also sliows that the mine 

generated noise is quite low in t!~c measuring location. 

The measured signal data (T.Cory) indicates that the minimum operating 

ranse of a cellular repeater will exceed 100 meters in a conductor-free 

I area. By coupling to trailing cables and other conductors, the expected 

comnunication ranse will cover the working areas of the mine. 

NNNNN 

I Sf I r 

YYYYX 
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The magnetic moment is defined as (Fi) 

M = NAI- x 

i ! Boulder, Colorado 

IT iTLE WIFS?I,ESS FF CO?l?!tKICATION SYSTE>I 

where Po is the transmitter output parer in watts, and 

DATE 39 . Se~f ,. .\9.80 

ISSUE . . . . . . . . . . . . . . 

% is the series resistance of a single tuned loop antenna. 

I 

; 1.6 ZlAGNETIC ?IOF!ENT 

The problem of maximizing the magnetic moment for a given transmitter 

output pmr (Po) is carried out by increasing N and decreasing RL. 

Thc geometry of the loop antenna (nan-pack) has limited the loop area 

2 {A) to range betwen 0.2 and 0.25 meters . An N turn loop produces 

a loop inductance (I.) of 80 microhenrys (ADL HO 346045 page 58). The 

series resistance of a single tuned loop antenna is 

t3L 

RL = -- (23) 

QCK T 

where QCi:T is the ratio of center frequency to 3 dB bandwidth (fo/BW). 

In a single tuned loop antenna network 

where QU fs tlic 'unloaded QU of the inductor (L). 

unloaded QU of greater than 80 can be achieved wfth an N=8 antenna 

inductor. At 60 k;!z, the series resistance (Rt) is 0.38 ohm. Using 

equation (22), t!ie magnetic monent (?I) for a four (4) watt transmitter is 

2 = 5.19 ampere-meter -* 

I *Note: This maximum magnetic moment is based upon the realizable QU of 

I the loop antenna s truc tr~re. 
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Y NO. . . .<V+S. 7. . . . . . . 

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I 

;TITLE WIPXLESS w CO~+IUNICATION SYSTEM I rssm . . . . . . . . . . . . . . 

The 3 dB transmission bandwidth of the maximum magnetic moment loop is 

60,000 P ,... I 750 He. 

80 

This loop antenna would not be useful because the transrnitsion bandvidth 

I is too narrow to accomodate the occupied bandwidth of the modulated FM 

I ihecurrentdesigipracticetstodegradethe QU ofthesingletuned 

I loop by artificially adding dissipation loss(resistance) to the loop 

circuit. The QU must be degraded to prod~lce a 3 dB transmission 

bandwidth (A f) of 10,000 Hz. 

60,000 Hz 

---- = 6 (maximum). 

10,000 112 

I As a result of the F?f occupied bandwidth constraint, RL must be increased 

to 5.0 ohms thereby degrading M to 

1 = 8 (.2)jT 

- 2 1.43 ampere-meter . A 

The minimum intrinsically safe resistance (RL) for a 4 watt transmitter is 

2.5 ) 4 = 1.638 ohms. 
A.R.F. PRODUCTS, INC 

Raton, h'ew Mexico 

NU. . .-'.V?-tc 4.. . . . . . . 

PAGE . .2 . . . . . . 0 

Boulder, Colorado 11 DATE . .30.~ep.t. .ll 

I 

i WIRELESS MF CO~lMUtiTCATION SYSTEM 11 Is$uE . . . . . . . . . . . . . 

I 

The artificial increase in resistance (R ) requires three times as much 

L 

transmitter output power to achieve the maximum safe magnetic moment. 

I order (series tuned) filter netuork 

. Irc 

0 

WL 

QU QCKT =- (26) 

R~ 

Therefore, there exists no possibility of maximizing H given BIJ, N 

A feasible solution to the magnetic moment optimization problem is to 

use a second order (or higher order) loop antenna network. In a first 

I and L (i.e. too many constraints). 

I In a higher order (n) lossless purely reactive quadripole network 

I (n 2 2), the transmission bandwidth of the network is independent of the 

unloaded QU of the network elements.* As a result, there exists a 1. 

feasible means of holding BW invariant over a reasonable range of Rt, * 

The higher order loop antenna structures can be designed using the 

I insertion loss synthes js procedure of Darlington. In the synthesis 

* In practice, tile transoiission banMdth is dependent on the unloaded QU. 
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Raton, New Mexico PACE . .;.I. ...... 0: 

delivered to the load plane resistance ( \) . 31e network has the 

property of an impedance matching network. The qrtadripole network is 

? bilateral and useful as both a transmitting and receiving antenna 

Boulder, Colorado 

ITLE WIRELESS MF COM?!UNICATION SYSTE2I 

Quadripole networks can be designed wf tlr different termination ratios 

(r - RS/RL). Later in the actual design of the second order loop antenna 

it will be obvious that 

% - 1.63 ohms, 

RL = 50 ohms, and. 

r 1.63150 = 0.03 . In the filter design problem the voltage socrce will represent the 

source voltage (VL) in the tuned loop (see Fi sure 1.2). Tllus part of 

the second order filter must hCwe the usual loop topology, 

DATE 30. Sept, .I981 

ISSUE ............. 

I 

where the circulating loop current C flows in a resonant circuit. The 

8 

'In the insertfon loss method, power is sourced from the generator ard 

energy stored in the inductor is given by 

E = % L i ik and (27) 

the energy dissipated per cycle is lost in RL and given by * 
A.R.F. PRODUCTS, INC. 

Raton, New Merim 

Boulder, Colorado 

...... I . ...... 

NO. .'t'i-', 7.. 

PAGE .?. .8 OI 

DATE ??. S?P.'*. ,I?$( 

The quality factor Q of this part of tl~c network is 

E 

Q =- 

Pd 

I 

\TITLE WIRELESS HF C0bllIU;iTCATION SY STE?I 

If the nehwrk topology can be realized as a second order passband f flter, 

I ISSUE .............. 

the 

! 

tsansf er cha: as sI~m in the following figure. 

- Cf 

-Lu 4 

z 

3 

3 -r 4.--- 

3 'I! 
A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

Boulder, Colorado * 

......... 

....... 

NU. .:'~+zr /. 

PAGE .3). 01 1 DATE 30. Be~.t., .!98( 

I 

In the following section, a mesh coupled resonator filter will be used 

to design the second order antenna network. 

bandwidth can be as wide as 10 to 15 % of Fo. 

In a second order tuned loop antenna, the loop tuning will not be criti- 

-k 

'0 

One advantage of the second order loop antenna is that the transmission 

* r 

Scanning transceivers with 8uf ficiently close operating frequencies will 

% 

4 

PC 

not require automatic tuning antenna structures. 

cal as in the first order loop case. T!lc antenna will also provide more 

discrimination loss against mine noise, and out of band signal. 

A disadvantage of this antenna is that it requires nore circuit elements. 

When automatic tuning is required, a rnininum of four circuit elements 

I 

must be switched, maximizing the loop antenna transmit magnetic moment, 

also increasing the pre forrnance of the receiving antenna. 

A.R.F. PRODUCTS, INC. 

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NO. . 3L)L>/.y. ........ 

? Q, PAGE . .-.,.. ...... Of 1 DATE 30 .S'?l?tr!~8

.............. TITLE WIREI.ESS MF CO?MWICATTON SYSTEhl 

1.6.1 Design of Cor~pled Resonator Loop Antenna Networks 

A coupled resonator antenna network can be designed from the low-pass 

- - 

prototype model with normalized element values (R . L1, C2, ... RL). s 

The prototype network is shown below. 

Figure 1.6 SECONI) OmER - LOW PASS PROTOTYPE NETWORK 

(Special Case with R, = 0) 

The synthes ized lowpass prc tptype element values arc: 

- 

C2 = 0.707, and 

This particular prototype network will match a voltage source (zero 

source resistance) to a ~iven value of load resistance (RL). The design 

approach assumes that loop antenna is operating as a receiver with an 

induced voltage source V (emf). 

Ihe transformation of the prototype circuit parameters to the mesh 

coupled resonator filter creates a pass band filter shown below. 
TYPED 

i 

I A.ReFe PRODUCTS, INC 

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Boulder, Colorado 

jTITLE WIRELESS kfF COMPlUNTCATION SYSTEM 

Figure 1.7 MESH COUPLED RESONA'I'OR FILTER NE'IWORK 

The mesh coupling capacitor is C12. 

IlV. . 2.b.44,. ... 

PAGE .. n -^ .'1. ...... OF 

.............. DATE 30 Sept. 1980 

ISSUE ............... 

Coupled resonators arc popular in filter design because the actual filter 

element values can be chosen in the design process, By way of contrast, 

in the synthesis of t!le low pass prototype, tile element values are the 

result of a continued fraction expansion; hence, are not selectable. 

. R 

0 

The principal design equations for the mesi~ capacitor coupled structure 

R\ cs\ L2 5, 

RN 

are shown in thc table below, 

Table CI 

Yesh Capac itor Design Equations 

Au= 3 dB bandwidth 

L1 = antenna inductance (80 ull) 
A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

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ITITIX I WIRELESS 1F CO?ClL?iICATION SYSTM 

7 

I I 

I Tlie value of C is 

. I 

s 2 1 

CT = - .I25 uf eel$ L* 

then 

. ....... 2 - PAGE d. C 

DATE 30 .SepF,. 19. 

The antenna network is shown in Figure 1 .a. 

ISSUE ............. 

Figure 1.8 !ZSlI COUPLED A\:YE:CiA XE'IWORK 

(BW = 10,000 Hz, fo = 60,000 Hz) 

The series resistance of the tuned loop circuit is . 5 
A.R.F. PRODUCTS, INC. 

Raton, New Mexico 

NO. . .iVl>r Y.. . . . . . 

PAGE . .3 3 . . . . . . I 

Table A-1 

Loop Antenna Parame ters 

I Boulder, Colorado 

I 

r TITLE WIRELESS ?tF CO?DfUNICATION SYSTEM 

i 

I 

I $1 Frequency in kHz Q for RW Turns L uH R ohms 

DATE .3Q.Sep.c.. .I 

ISSUE . . . . . . . . . . . . 

0 Asswnption: 

0 Loop area (bandolier) .25m x .8m = .2m2 

# 2 

i L% 2.5AN (ulf) 

1 

i APPE:mIX A 
A.R.F. PRODUCTS, INC. 

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Boulder, Colorado . I NU. . .4VC>/J.. . . . . . 

PACE . ..35 . . . . . 

DATE .3Q. Seat. .l 

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;TITLE WIRELESS >F COFP~LNICATION SYSTM ISSUE . . . . . . . . . . . . 

I 

APPENDIX B 

DISCKT?IIMTION LOSS Ah?) BANDEDGE FREQLENCIES 

FOR A 

FIRST A:v9 SECOh?) ORDER TUNED LOOP ANlENNA 

4 

Table B-1 

Center Frequency (fo) 60 kHz 

B andw id t h ( BWCK T) 10 kHz 

Bandwidth . . Bandedge Frequency in kHz . Discriminatfon loss 

BWD L %I n-1 n-2 

BIJ~~ T 55207 65207 3 3 
! 

I A.R.F. PRODUCTS, INC. NU. . .'I"':'! .'. . . . . 

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PACE . . .?7. . . . . . .. t 

i 

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I 1 TITLE WT IXLESS FfF C0?'2.1Llh1ICATI0N SY STEY 

DATE 1 ssm 

Table B-2 

DISCRPII NATION LOSS Ahm BANDEDGE FMQUENCZES 

FOR A 

FIRST AND SECO?lIl ORDER TLWED LOOP ANTENllA 

Center Frcquqncy (f,) 600 klIz 

Bandwidth (BWCKT) 60 kliz 

Bandw id t h Bandedge Frequency in kHz Discr hination loss 

n=l nu2 

3 3 

6.9 12.: 

9.9 19.: 

14.5 25.1