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Philips Semiconductors B.V.
Low cost DECT Power Amplifier PH9 7005
Prelim in ary A pplication No te RNR-T4 5-97-M-0 931
Au th or
L.C. Colussi
Novemb er 2 1, 19 97 Discre te Se micon ducto rs Nijmege n Gerstwe g 2, 65 34 AE Nijme gen Th e Netherland s
Key words PA, DECT, DPO, BFG4 25W, BFG2 1W Abs trac t Ap plicatio n of n ew 5th gen eration discrete bipo la r RF tra nsistors facilitates d esign o f a low cost two-stage p owe r amp lifier fo r DECT syste ms, h aving a p owe r gain of 26 dB a nd an overall efficie ncy b ette r than 4 0%. The amp lifie r ope ra te s fr om a sing le supp ly volta ge, in clude s bias circuitry for loa d pow er ad ju stmen t an d on/off switch in g and is mou nted on a b ilayer p cb, requ irin g 10 x 20 mm . A descrip tion is given of the circu it desig n and the b oard layo ut, includ in g mea sureme nt results.
Philips Semiconductors B.V.
PH97005
Low cost DECT Power Amplifier
INTRODU CTION Th is n ote des crib es the ap pl ic atio n of two of th e new 5th gen er ation si li co n bi pol ar RF tr an si stor s i n SOT3 43R pl as ti c SMD p ack age i n a two-stage p owe r amp li fi er (PA ), des ig ned for u se i n DEC T cor dl es s te le pho ne sy stems . Th ese tra ns is to rs , man ufactur ed ac co rd ing to the ne w do ubl e- po ly proce ss, are cha ra cter is ed by the ir h ig h tran si ti on fr equ enc y (fT > 20 GH z) at lo w su ppl y voltag es , re sul tin g in a s upe ri or powe r ga in at mi crowav e fr eq uen ci es, usu al ly a fi el d de di cated to GaA s- dev ic es. Two l ay er s of p ol ysi l ic on ar e us ed: one for c ontac ting the b ase , yi el di ng a l ow ba se resi s tan ce a nd one to for m the e mitter , re su lti ng in a s te ep em itte r do pe pr ofi le an d an effecti ve em itter wi dth of 0 .5 m. A bu ri ed N-l aye r (c ol l ector ) is pl ace d wi th in a Psu bstr ate, wh ic h is con nec te d to the e mitter pa ck age l ea d, wh ic h ena bl es th e di e to b e pl ace d on the g rou nd pl an e, red uci ng e mitter i nd uctan ce an d th erm al resi s ta nce . Fi gu re 1 sh ows a cros s se ctio n of a do ubl e- po ly bur i ed la ye r tran si stor .
1 2 3 4 Fig u re 1 : Cro ss sectio n an d p acka g e of th e d ou b le -p o ly b u ried la yer RF t ra nsisto rs.
bas e e mitt er c ol le ct or e mitt er
Wi th o nl y two do ubl e- po ly tran si stor s a comp le te a mpl ifi er l i ne- up ca n be real i sed , offer in g 26 d Bm of o utput powe r wi th mo re tha n 26 dB po wer g ai n. Th e ampl i fi er req ui re s a si ngl e su ppl y voltag e of 3 .6 V a nd typi ca ll y ha s 44% effic ie ncy . The bi as in g c i rc ui try us es on ly o ne NPN tra ns is to r pai r , whi c h a ls o pe rfor ms lo ad po wer a dj ustme nt an d on/off s wi tc hi ng func ti on s. Th ank s to the l ow c ompo nen t co unt and s imp le ma tc hi ng ne tw ork s the en ti re a mpl ifi er ( in cl udi ng b ia s part) onl y mea su res 1 0 x 20 mm. As c ompa re d to a p rev i ous d emon stra ti on b oard, P H960 60 (Pre li mi nar y Ap pl ic atio n Note RNR-T4 5-96 -T-83 8) thi s on e offer s lowe r add iti ona l co mpo nent co unt, bu t is le ss s ui ta bl e fo r PHS a ppl i cati on. Th e mai n fe atur es of th e PA ar e: - l ow co mpon ent co unt - s mal l si ze - h ig h effi ci en cy - s in gl e sup pl y ope ra ti on
RNR-T45-97-M-0931
Philips Semiconductors B.V.
PH97005
Low cost DECT Power Amplifier
CHAR ACTER IS TIC S
(unless otherwise specified the operating frequency is 1. 89 GHz, the supply voltage is 3.6 V, the input power is 0 dBm and the period is 10 ms with a duty cycle of 1:8)
Pa rame te r Gener al para meters Su ppl y vo ltag e (Vs ) Con tr ol vol tage (Vc ) Fr eq uen cy rang e Ty pe of ope ra ti on So urc e an d l oa d im peda nc e Po wer g ai n (G p) Outpu t po wer (Po) Av g. s upp ly c ur re nt Effic ie ncy Inpu t VSWR Isol ati on (r ela tive t o in pu t po wer ) Sp uri ou s Le aka ge cu rren t in o ff- state Har mon ic s: 2nd 3 rd Lo ad mi sma tc h: Pr in te d ci rc ui t bo ard Di men si ons
Tab le 1:
Specifica tion 3.2 3 .6 4 .2 V on s ta te : 3.6 V off s ta te : 0 V 1.88 - 1.9 2 GHz pu ls ed 50 26 dB 26 dB m 11 mA 40% 2 :1 50 dB -6 0 dBc 10 A -3 0 dBm -3 0 dBm No de gr ada ti on FR4 b il ay er
(h = 0. 7; r= 4. 6; ta n = 0. 02 )
Ty pical
Condition
du ty c yc le 50% 26 .3 d B 26 .3 d Bm 44 % 57 d B Po = 26 dB m Po = 26 d Bm Po = 26 d Bm Vc = 0 V Vs = 3.2..4 .2 V VSWR 6 : 1, al l p has es Vc = 0 V
- 34 dBm - 13 dBm
Po = 26 d Bm, Vs 4.5 V VSWR 6 : 1, al l p has es
10 x 2 0 mm
(in clu din g bias circu it ry)
Cha ra cte ristics o f th e DE CT P A PH97 0 05 .
RNR-T45-97-M-0931
Philips Semiconductors B.V.
PH97005
Low cost DECT Power Amplifier
CIRCUIT DES CRIP TION Fi gu re 2 s hows c i rcu it di agr am of th e DECT PA i nc lu di ng bo th RF tr ans is to rs , match in g ci rc ui ts an d bi asi ng c ircu it. The ap pen di x con ta in s th e part l is t o f th e dem o b oard.
Vs
Vc R7 R4 Q3a R5 R2 Q3b R6 TL3 C4 TL8 TL7 R1 C1 RF in TL1 C2 Q1 C3 C5 C10 TL2 TL4 TL5 TL6 Q2 C11 RF out C6 R5 C8 C12 R3 C7 C9 C13
Fig u re 2 : Circu it d ia g ra m o f t he DECT PA d e mo bo a rd P H9 7 00 5 .
RF tra nsist or s Th e RF ch ain o f the PA c ons is ts o f two tran si stor s ta ges : a BFG425 W (Q1) wid eba nd tra nsi stor , op er atin g i n cla ss A an d a B FG21 W (Q2) , o peratin g in c la ss AB . In acc or dan ce wi th the a bov e se tti ngs the me asu re d sou rc e and l oad i mp edan ce s of b oth tra nsi stor s are gi ve n in tabl e 2.
Tr ans is tor BFG425 W
(V ce= 3. 6 V; Ic= 30 m A; f= 1. 89 G Hz)
Sourc e impeda nce (Zs) 12 + 0 .7 j 8 - 4 .5 j
Load impedanc e (Zl) 52 + 1 02 j 12 - 3.5 j
BFG21W
(V ce= 3. 6 V; Po= 26 d B m; f =1 .8 9 GHz)
Tab le 2 : S ou rce a n d lo ad imp ed a n ce s o f th e ap p lie d RF tr an sist or s.
Sma ll si gna l S- par ame te r da ta for the B FG42 5W as wel l a s la rg e si gna l Sp ic e par ame te rs o f bo th the BFG42 5W a nd the BFG21W are av ail ab le o n fl op py di sc . Th e RF tr an si stor s hav e tw o emi tter s lead s, wh ic h hav e to b e careful l y groun ded to en sure stab le o perati on and p erfo rma nce a cc ord in g to s pec ifi cati on. Typ ic al l y, the i ndu ctan ce of th e vi as h as to be kept b el ow 0.1 nH.
RNR-T45-97-M-0931
Philips Semiconductors B.V.
PH97005
Low cost DECT Power Amplifier
Impedanc e matc hing Th e imp eda nce ma tc hi ng pa rt con si sts of th ree s epa ra te s ecti ons : the inpu t, th e in te rs ta ge an d the ou tp ut ma tc hi ng ne two rk s. The pu rp ose o f thes e networ ks is to en abl e th e RF tran si stor s to gi ve o ptimu m p erfo rma nce w ith re spe ct to po wer g ai n, o utput powe r an d effi ci en cy. Fortuna te ly , the imped anc e le vel s of th e app li ed do ubl e- po ly tran si stor s are n ot e xc epti ona ll y hi gh o r lo w, s o they 'r e ra th er e asy to ma tc h. Dec ou pl in g i s d one by usi ng c apa ci to rs C1 , C4 , C6, C8, C 11 an d C12, whi ch a re seri es r eso nan t at 1.9 GHz. C apa ci to rs C7 (wi th res is to r R3 ) and C 9 are u sed to su ppr es s lo w fre que ncy i ns ta bi li ty.
At th e inp ut s i de sh unt cap aci tor C2 a nd se ri es tra nsmi ss io n li ne TL1 matc h the 5 0 sou rc e to the ba se of Q1. B ase res is to r R1 is us ed fo r bi as in g and ha s no effect on match in g.
input Q1
TL1
C2
Fig . 3a : In pu t mat ching .
Be twe en the co ll ec to r of Q1 and the b ase o f Q2 match in g is d one b y se ri es tra nsm is si on lin e TL2 , sh unt ca pac itor C3 and s er ie s tr an smi ss io n li ne s TL4 a nd TL 6. B oth s hu nt c apa ci to rs C3 a nd C5 (par tly ) co mpen sa te the influ enc e of b ia s stubs TL3 a nd TL5 , whi c h are b oth sho rter th an a qua rter wave le ngth.
input Q2
TL5/C5 TL3 output Q1 C3 TL2
TL4/TL6
Fig . 3b : In te rsta ge m at ch ing .
Th e outpu t match i s do ne by s er ie s tr an smi ss io n li ne TL 7 and s hun t ca pac itor C10. Aga in thi s ca pac itor al so co mpen sa te s th e in fl uen ce o f bi as s tu b TL6 .
TL7 output Q2
C10
Fig . 3c: Ou tp ut ma tch in g .
RNR-T45-97-M-0931
Philips Semiconductors B.V.
PH97005
Low cost DECT Power Amplifier
Biasing Th e bi asi ng p art of the P A is c enter ed a rou nd a du al NP N trans is tor, Q3 a and b . Th e ci rc ui t offer s a te mperatur e com pen sated b ia s vol tage for b oth th e fi r st a nd the se con d RF stag es. Unl i ke the pr ev io us de mo bo ard P H960 60, th e ci rc ui t is acti va ted w hen Vc is h ig h, wh ic h is be yon d 2.4 V. The bi as o utput v ol tage for the fi rs t stag e is a l i ttl e hi gher th an for the s eco nd stag e. D ue to s er ie s re si stor R 1, the fis t sta ge is curre nt d ri ve n and o perates i n cl as s A. The se con d stage i s d ri ven b y at the k nee v ol tage (0.7 V) an d ope ra te s in c la ss AB . Se ri es resi s to r R2 pr otec ts Q 2 from th ermal run away .
The cur re nt de sign of the P A does n't include any me asures to re duc e adjac ent c hannel power due to s witching tr ans ie nt s. The slope of the RF puls e can be too s te ep and has to be r elaxe d to c omply to the a ppr ova l specif ic ation. This c an be done by pla cing a ca pac itor at the base of Q3a . Ex per ime ntal inv est igation has s hown that a 10 nF c apa citor approximat ely offer s a 20 dB impr ove ment of the adja cent channel power .
Rec ommendat ions for use
Fi gu re 4 s hows h ow the PA sh oul d be c onn ected .
Q1 C3 TL2 C4 TL1 TL4 TL7 C2 C7 R3 R1 R5 R4 TL3 C6 TL5 C8 R2 C13 C9 C10 TL8 TL6 C5 Q2
Q3 R6 C1 R7
C12 C11
RF in
RF out
pulse (active high)
GND
3.6V supply
Fig u re 4 : S ch e ma tic vie w of th e PA co n ne ction s.
In pul se d con di ti on a t no min al s upp ly v ol ta ge an d outpu t po wer l ev el , the load c an be mi sma tc hed (VSWR 6 : 1, al l ph ase s) wi thou t da mage . Th e PA ca n a ls o be op erated in CW, bu t on ly w hen the ou tp ut i s prop er ly ma tc hed wi th 50 . Whe n a mis matche d lo ad is app li ed w hen the am pli fie r is ope ra te d in CW, th is wi l l ca us e da mage o f the fin al s ta ge.
RNR-T45-97-M-0931
Philips Semiconductors B.V.
PH97005
Low cost DECT Power Amplifier
BOAR D LAYOUT Fi gu re 5 s hows the l ay out of the P CB, wh ic h has th e fol l owi ng p rop erti es : type : FR 4 b il ay er (ba cks i de gr oun d) h = 0.71 mm t = 3 5 m (Cu c la ddi ng , no t co ated) r = 4.6 tan = 0.02
Q1 C3 TL2 C4 TL1 TL4 TL7 C2 C7 R3 R4 TL3 TL5 TL8 C9 C10 R1 R5 C13 TL6 C5 Q2
C6
C8
R2
Q3 R6 C1 R7
C12
C11
Fig u re 5 : L ayo u t o f th e DE CT P A d e mo b oa rd .
Al l r es is to rs a nd ca pac itor s us ed ar e Phi l ip s 060 3 SMD ty pe s. Ap pen di x A con ta in s th e part l i st of th e demo b oard. The po si ti on o f co mpo nen ts C2 , C3 , C5 an d C10 is criti cal . Th e artwo rk fi le i s av ai la bl e on flo ppy d is c (DX F fo rma t).
RNR-T45-97-M-0931
Philips Semiconductors B.V.
PH97005
Low cost DECT Power Amplifier
MEAS UREME NT RESULTS Measurements under pulsed conditions, with a 10 ms period and a duty cycle of 1:8.
.
Gain and Efficiency vs. Pout
27
30 28 100 80
Gain and Efficiency vs. frequency
50
26 24 G( 22 20 10 15 20 Pout (dBm) 25 Gp 30
60 40 Eff ( 20 0 Eff
26 Gp (
45 Eff
25 1.86
1.89 freq (GHz) Gp
40 1.92 Eff
Figure 6a: f = 1.89 GHz; Vs = 3.6 V; V c = 3.6 V.
Figure 6b: Vs = 3.6 V; Pin = 0 dBm; V c = 3.6 V.
Gain and Efficiency vs. supply voltag
27 50
40 20 0
Gain and Efficiency vs. control voltag
100 80 60 40 20 0 3.6 Gp Eff
26 G(
45 Eff (
-20 Gp ( -40 -60 0 0.6 1.2 1.8 Vc (V) 2.4 3 Eff (
25 3.2
3.4
3.6 Vs (V)
3.8
4 Gp
40 4.2 Eff
Figure 6c: f = 1.89 GHz; P in = 0 dBm; V c = 3.6 V. dBm.
Figure 6d: f = 1.89 GHz; Vs = 3.6 V; P in = 0
RNR-T45-97-M-0931
Philips Semiconductors B.V.
PH97005
Low cost DECT Power Amplifier
APP ENDIX
Pa rt l i st D ECT PA de mo bo ard P H970 05
Res i stor s R1 R2 R3 R4 R5 R6 R7
C1 56 0 56 10 22 0 82 33 0 1K C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12
8.2p 1.8p 1.8p 8.2p 3.3p 8.2p 10 n 8.2p 1n 2.7p 8.2p 8.2p 1n
Tr an smi ss ion l i nes TL 1 L = 6.5 mm W = 0.45 mm TL 2 L = 3.0 mm W = 0.15 mm TL 3 L = 7.5 mm W = 0.15 mm TL 4 L = 2.0 mm W = 1.15 mm TL 5 L = 7.5 mm W = 0.15 mm TL 6 L = 2.0 mm W = 1.15 mm TL 7 L = 5.0 mm W = 0.45 mm TL 8 L = 6.5 mm W = 0.15 mm
C13
Tr an si stor s Q1 Q2 Q3
BFG425 W BFG21W PUMX 1
Cap ac itor s
RNR-T45-97-M-0931

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