A 3 to 5 GHz UWB SiGe BiCMOS Low Noise Amplifier

Transcription

1 ETIT 7 th International Conerence: ciences o Electronic, Technologies o Inormation and Telecommunications March 5-9, 7 TUNIIA A 3 to 5 GHz UWB ige Bi Low Noise Ampliier Farid Touati*, Mourad Loulou**, and Mohammad Bouzid** *Department o Electrical and Computer Engineering ultan Qaboos Uniersity (QU) Al-Khod, Muscat, Oman touati@squ.edu.om **Laboratoire de l Electronique et des Technologies de l Inormation National Engineering chool o ax, Tunisia mourad.loulou@enis.rnu.tn bouzid.med@tunet.tn Abstract: Ultra-wideband low-noise ampliiers (UWB operating in the low-requency band (3. 5 GHz) o UWB spectrum are presented. The designs consist o a cascode ampliier with wideband input matching techniques based on LC-ladder ilters or shunt-eedback both combined with inductie peaking. Implemented with a ige Bi process, the LNAs gie. db gain, better than - db input matching, and a return loss less than -3 db, while consuming mw under.5 V supply. The eedback LNA gies a better lat noise igure o.5 db and an input IP3 o -6 db at 5 GHz. Key words: LNA, Ultra wideband technology, wideband matching, shunt-eedback. INTODUCTION Although the ultra-wideband (UWB) standard (IEEE.5.3a [] [] has not been completely deined, there has been an increasing interest in the lowrequency band (3.-5 GHz) o the UWB allocated requency range (3.-.6 GHz). A major proposal proposes that data rates o up to - Mb/s can be obtained using the low-requency band alone. This requency band has been allocated or the deelopment o the irst-generation UWB systems (> Mb/s) targeting low-power wireless multimedia applications and high-perormance PC peripherals oer a short distance up to m. o ar, wideband designs are dominated by three dierent topologies: the distributed ampliiers, resistie shunt-eedback, and recently the LC-ladder ilter matching. Two major drawbacks o the distributed ampliiers is that they tend to consume large dc power due to the distributed multiple stages and are not optimized or low noise [3] []. The resistie shunt-eedback broadens the working requency in terms o input impedance matching, gain, and linearity [5] [6]. Also, it reduces the circuit sensitiity to external actors such as biasing, process tolerances, and temperature. Howeer, in narrow-band systems the eedback resistance must be small to match 5 Ω, hence degrading the noise igure. The LC-ladder match gies good wideband perormance with low dc power [7] []. Howeer, the reactie elements used in such systems tend to occupy large chip area and degrade the noise igure in case o on-chip implementation. This paper presents low-noise, low-power, and good linearity ige Bi ampliiers and compares the perormance characteristics o the shunt-eedback and LC-ladder ilter matching techniques in the UWB GHz band. The bipolar deice was chosen because o its higher maximum aailable gain (MAG) and the ease to obtain an unconditional stability oer a wide bandwidth owing to its lower impedance.. Design Using LC-Ladder Filter Matching The proposed topology, shown in Fig., uses a cascode ampliier embedded in a bandpass LC ilter or input matching oer the passband. - -

2 ETIT7 (in db); and and noise igure (in db). imulation results hae been obtained or a 7GHz T ige Bi process. +.j +j +j 3 GHz 5 GHz Figure. chematic o a wideband ampliier using LC-Ladder ilter matching. Here, the matching circuit elements are chosen [] so that Lm and wl C m and w U Le () wu and the cuto o requency π LC o the denominator o the put impedance must be pushed beyond 5 GHz. Also, this will ensure that nonlinear phase shit and thus nonlat group delay due to peaking does not occur in-band. Figures, 3, and show the simulated results o the ampliier, respectiely, the smith chart o ; the,, and Ct () w where w L and w U are the lower and upper requencies o the input bandpass ilter, which embeds the total capacitance C t C π +C p between base and emitter, the emitter-degenerating inductance Le, and the resistance w T L e is the designed to equal the source resistance (5Ω) oer the entire bandwidth o resonance w U -w L. The oltage gain o the ampliier was deried as g m W ( s) Zcd ( s) (3) in sct + sc + s LC L L + s where gm is the transconductance o Q, W(s) the transer unction o the bandpass ilter equals oer the bandpass, C the total capacitance at the collector o Q, and Z cd (s) is the ratio o the current entering the base o Q oer the current entering the bandpass ilter at the input (IN), which is equal to.5 oer the bandpass. In (3), the irst term is the current gain o Q at high requency, the product o the irst three terms is the put current, that is, the collector o Q and so o Q assuming an ideal operation o the cascode, and the last term is the put impedance at the put node. The inductor L compensates the roll-o with requency o put current by adding a zero at /πl. Thereore, in order to obtain a lat response oer 3.-5 GHz at the put both the zero due to L -.j -j Figure. imulated traces o LNA using LC- Ladder ilter matching.,, [db] j Figure 3. imulated input/put return loss and reerse isolation o LNA using LC-Ladder ilter matching. [db] Figure. imulated power gain and noise igure o LNA using LC-Ladder ilter matching. The power gain is db with a maximum o ab 9 db at around the center requency or GHz. This is due to the better matching around this requency as it is clear in Figs. and 3. Howeer, the noise igure achieed here is around.5 db, which is not as low as expected. In contrary to FET cascode, the condition or optimum gain is dierent rom that o the 6 NF [db] - -

3 ETIT7 minimum noise igure, imposing a tradeo between gain and noise perormance. As can be seen in Fig. 3, the simulated input return loss () is higher than 7 db oer 3-5 GHz. The put return loss () is higher than 5 db due to the cascode. The reerse isolation is better than -7 db, which is good. The inductors L e. nh and L b. nh can be absorbed as a part o the package parasitics during implementation. The inductor L m.7 nh can be realized with a transmission line. The dc power consumed is mw under.5 V supply. The ollet stability actor, decreasing with requency, was always aboe due to a careul design o the peaking inductor L, which may cause instability.. Design Using hunt-feedback Figure 5 shows a schematic o the proposed LNA with a resistie shunt-eedback. The inductor L e is added or simultaneous noise and input matching and L b or the impedance matching between the source resistance and the input o the LNA. The emitter inductance (L e ) plays the role o a series eedback and hence shits the input impedance to higher alues. This low inductance o ab. nh is realizable with a transmission line, hence sparing additional areas or on-ship spiral inductor. -.j +.j +j 5 GHz 3 GHz Figure 6. imulated traces o LNA using resistie shunt-eedback.,, [db] j +j -j Figure 7. imulated input/put return loss and reerse isolation o LNA using resistie shunteedback. 6 [db] 6 NF [db] Figure 5. chematic o a wideband ampliier using resistie shunt-eedback. Figure. imulated power gain and noise igure o LNA using resistie shunt-eedback. Figures 6, 7, and show the -parameters o the LNA. It is clear rom Figs. 6 and 7 that the eedback allowed a better impedance matching oer 3-5 GHz. The Miller eedback resistor at the input reduces the quality actor o the input resonating matching network, hence widening the input match around the center requency o GHz [3]. The eedback resistance 3. kω here is high enough to not degrade the noise igure while widening enough the impedance matching. hunt-eedback or cascode topologies may not be appropriate or the ull UWB range (i.e GHz). Using this technique or wider range would require a signiicant decrease in in order to lower the quality actor suiciently, which - 3 -

4 ETIT7 would in turn degrade the noise actor. The power gain achieed is ab.3 db with a noise igure as low as.5 db, input return loss better than - db, put return loss higher than 5 db. The reerse isolation is better than -3 db. The inductors L e. nh and L b. nh can both be realized with a transmission line. The dc power consumed is mw under.5 V supply. The ollet stability actor was always aboe 3. We tried also to beneit rom the irtues o both wideband techniques studied aboe by studying an ampliier using simultaneously the LC-ladder ilter matching and resistie shunt-eedback. This has not improed signiicantly the LNA wideband characteristics. In this case, the oltage gain becomes in g sc m t W ( s) Z cd ( s) L + s + + ( // ) ( // ) L + s C + s ( // ) () The cuto requency o the last term in () becomes o, hence pushed to higher ( // ) π LC L C alues compared with the case o LC-ladder matching with eedback. This would latten more the put response. Howeer, to obtain a signiicant lattening, must be set low enough, degrading hence noise perormance o the LNA. Oerall, the shunt-eedback topology gies a better perormance oer 3-5 GHz. Table compares the results o the three topologies. Table. Comparison o Wideband i LNA Perormances o Dierent Techniques. e. Feedba ck LC-Matching Feedback & LC- Matching (db).3±.±.5.±. NF (db) (db) < - < -7 < - (db) < -5 < -5 < -5 (db) < -3 < -7 < -3 Pdc (mw)...6 ICP (dbm) GHz ICP (dbm) GHz IIP3 (dbm) GHz IIP3 3 GHz Table compares the results o the shunt-eedback topology o this work with recently reported works. Table. Comparison o Feedback LNA With ecently Published Designs. e. [3] [] [5] [6] [7] [] [9] This work 3-dB BW (GHz) Gain (db) NF (db) (db) < -9 < - < - < -7. < < -7 < - (db) < -5 (db) < -3 Pdc (mw) IIP3 (dbm) GHz ICP (dbm) GHz Topology hunt FB with inductie degeneration Technology. µm Distributed. µm Feedback.5 µm Feedback (dierential). µm LC-ilter based. µm LC-ilter based. µm ige Bi - 5 GHz Distributed.6 µm hunt FB with inductie degeneration ige HBT Year

5 ETIT7 3. Conclusion Wideband low-noise ampliiers using dierent wideband techniques optimized or the lowerrequency band (3-5 GHz) o UWB systems are presented. The ampliiers topology adopts the LCladder ilter matching and/or conentional resistie shunt-eedback, embedding a HBT cascode ampliier. These techniques hae allowed a good input matching. A superior oerall perormance is obtained with the shunt-eedback technique oer 3-5 GHz. The simulated result or this topology shows more than db o power gain, a higher than -9 db o input return loss, an put return loss bigger than -5 db, a reerse isolation better than -3 db, and an input third-order intercept o -6 db, while dissipating mw rom a.5 V supply. The noise igure stays as low as.5 db oer all 3-5 GHz. The proposed resistie shunteedback LNA shows adantages in oerall perormance, compared to other recently published wideband topologies. [7] A. Beilacqua and A. M. Niknejad, An ultrawideband LNA or 3. to.6 GHz wireless receier, IEEE ICC Dig. Tech. Papers,, pp [] A. Ismail and A. Abidi, A 3 to GHz LNA using a wideband LC-ladder matching network, IEEE ICC Dig. Tech. Papers,, pp [9] T. K, Nguyen et al., low noise ampliier design optimization techniques, IEEE Trans. Microwae Theory Tech., ol. 5, no. 5, pp. 33-, May. ACKNOWLEDGMENT The authors wish to thank the Tunisian Ministry o cientiic esearch Technology and Deelopment o competencies or its support and grant in the rame o the program o cooperation with the Tunisian researchers abroad. EFEENCE [] Multi-band OFDM Physical Layer Proposal, IEEE P.5 Working Group or Wireless Personal Area Networks (WPANs), 367r5P_5_TG3a-Multi-band-OFDN-CFP- Presentation.ppt. [] Xtremepectrum CFP Presentation, IEEE P.5 Working Group or Wireless Personal Area Networks (WPANs), 367r5P_5_TG3a-Xtremepectrum-CFP- Presentation.ppt. [3] C. W. Kim, M.. Kang, P. T. Anh, H. T. Kim, and. G. Lee, An Ultra-Wideband Low Noise Ampliier or 3-5 GHz UWB ystem, IEEE Journal o olid-tate Circuits, ol., no., 5, pp []. C. Liu, K. L. Deng, and H. Wang, A.6- GHz broadband distributed amplier, Proc. IEEE adio Frequency Integrated Circuits (FIC) ymp., June -, 3, pp [5] F. Bruccolori, E. A. M. Klumperink, and B. Nauta, Noise canceling I wideband LNA s, IEEE ICC Dig. Tech. Papers, ol., Feb., pp [6]. Andersson, C. ensson, and O. Drugge, Wideband LNA or a multistandard wireless receier in. µm, Proc. ECIC, ep. 3, pp