A Wideband Low-Noise Downconversion Mixer with Positive-Negative Feedbacks

Transcription

1 th ranian Conferene on letrial ngineering (C ) May 5-7 Tehran ran A Wideband Low-Noise Downonversion Mixer with Positive-Negative Feedbaks Hadi Naderian Ahmad Hakimi and Masoud Movahhedi 3 letrial ngineering Department Shahid Bahonar University of Kerman Kerman ran hnaderian@engukair hakimi@mailukair 3 movahhedi@ieeeorg Abstrat- This paper presents a wideband low-noise mixer in CMOS 3-um tehnology that operates between -5 GHz The mixer has a Gilbert ell onfiguration that employs broadband low-noise transondutors designed using the negative-positive feedbak tehnique used in low-noise amplifier designs This method allows broadband input mathing The urrent-bleeding tehnique is also used so that a high onversion gain an be ahieved Simulation results show exellent noise and gain performane aross the frequeny span with an average double-sideband noise figure of 9 db and a onversion gain of 55 db t has a third-order intermodulation interept point of - 87 dbm at 5 GHz Current Bleeding Ciruit Keywords- Wideband low-noise urrent bleeding noise anellation feedbak NTRODUCTON Ative mixers based on the Gilbert ell onfiguration often exhibit a large amount of noise This leads to strit requirements for the noise figure (NF) of the low-noise amplifier (LNA) preeding the mixer suh that a partiular signal-to-noise ratio an be ahieved This usually requires at least one very low-noise LNA that has enough gain and noise performane to mitigate the noise added by the mixer Power onsumption is also a problem as the LNA NF dereases when larger transistors are used However these requirements an be muh relaxed or the LNA an be removed if the mixer NF is low enough The Gilbert ell mixer has been widely used in integrated iruit (C) design even though it exhibits moderate noise However its NF an be drastially redued by ombining the LNA and mixer into a single omponent Narrowband low-noise mixers have been proposed in other works []-[4] where the transondutors were replaed by indutive-degenerated LNAs To onvert a Gilbert ell into a wideband low-noise mixer the transondutors must be wideband in terms of NF gain and input mathing Many broadband and UWB LNAs have been proposed [5]-[7] n [5] an ative feedbak approah was used to ahieve broadband mathing and gain The iruits in [6] and [7] use filters to ahieve broadband input mathing and low noise performane Another broadband LNA design method is the noise-anelling tehnique [8] whih has been used for mixer in [9] A ommon-gate (CG) LNA has been widely investigated beause it features superior bandwidth linearity stability and Figure Mathing Network Ciruit Blok diagram of proposed mixer iruit robustness to PVT variations ompared to a ommon-soure (CS) topology [] n spite of these advantages the dependene of gain and NF on the restrited transondutane (gm) makes this topology unsuitable for various wireless appliations The input impedane of a CG LNA is simplified as /gm and the noise fator is inversely proportional to gm [] n order to ahieve high gain and low NF gm should be inreased whih deteriorates the 5n input impedane mathing for a onventional CG LNA n this paper to ahieve high gain and low NF without sarifiing bandwidth linearity and power onsumption a differential gm-boosted CG transondutors with a positivenegative feedbak tehnique is proposed The proposed mixer with output buffers delivers a maximum onversion gain of 55 db a minimum NF of 6 db an P3 of -87 dbm and 44mW power onsumption //$3\ 6

2 CRCUT DSDRPTON The proposed wideband low-noise mixer blok diagram is shown in Fig The mixer based on the Gilbert ell topology with some modifiations The mixer is omprised of four building bloks: positive-negative feedbak transondutors peaking indutors urrent bleeding and swithing pairs A detailed design analysis of the positive-negative feedbak transondutors blok is provided first followed by a desription of eah blok A Positive-Negative Feedbak Transondutors The proposed topology shown in Fig onsists of rossoupled apaitors in negative and PMOS transistors in positive feedbak branhes in a differential CG onfiguration The differential signals flow to the soures of the NMOS transistors and are also ross-oupled to the gates of the opposite NMOS transistors through apaitors whih results in a shunt-series negative feedbak path [3] The outputs of the NMOS transistors are oupled to the soures of the opposite NMOS transistors reating a shunt-shunt positive feedbak loop The input impedane is obtained as Z N = --- gmmn ( +A NG )( - A pos) using input shunt-negative and shunt-positive feedbak theory [4] ANG whih is approximately given by C/(C+Cgs) is almost unity Positive feedbak is equivalent to gmmprl an be variated from to for an arbitrary hoie of gmmp required to ahieve an input mathing ondition The output impedane is given by Z'OUT is the impedane without feedbak and exluding ZL While Apos is inreased the output impedane as well as gmmn for the input mathing an be inreased ( ) Figure 3 Two-pole series peaking network [9] n this arhiteture the effetive transondutane (GM) is given as Z N - ---'-'----- gmmn (+A NG ) gmm' Rs +Z N With the help of gm boosting through the apaitor rossoupling (CCC) negative feedbak GM is the same as the NMOS transondutane itself As a result the voltage gain (=GM*ZOUT) an be high with relatively low power onsumption through the large ZOUT and large GM Obtaining high gain and low power onsumption without the onstraint of the input mathing in the proposed CG onfiguration is attrative but the stability needs to be investigated in suh a high-gain transondutor design The NF of the iruit an be omputed onsidering thermal hannel noise and load noise n this ase [5] F = + y ( l-a POS ) + R L gmmp S a( l +A NG ) a Rs +-(-APOS) RL Where y is the MOS transistor thermal noise oeffiient a is defined as the ratio of gmmn to the zero-bias drain ondutane gdo' The seond term represents the hannel noise ontribution of gmmn whih an be greatly redued through ANG as well as Apos The hannel noise of MN flows to the gate and soure of an opposite MN with the same phase through C and the positive path respetively Thus the ombination of positive feedbak and the negative feedbak loop ontributes to hannel-noise anellation The third and fourth terms show the noise indued by Mp in the positive feedbak path and the load respetively The noise due to Mp an be dereased by using small gmmp and the load noise is redued by Apos (3) (4) Figure Simplified blok diagram of transondutor B ndutive Peaking The mixer bandwidth an be signifiantly affeted by the large output apaitane from transondutors as well as from the bleeding iruit and swithing pairs ndutive peaking an be used for bandwidth extension Series peaking is used in this design and the peaking indutors are plaed between the swithing pairs and the transondutors as shown in Fig To understand the operation of these indutors a simplified iruit is shown in Fig 3 when only one of the swithes is on Preeding the mixer ore is the transondutors whih an be approximated by a voltage-ontrolled urrent soure; COU is the olletive output apaitane from the transondutor and the 7

3 urrent bleeding tehnique is implemented by using two PMOSFTs to redue the bias urrent of the LO swithes [6] T T Figure 4 PMOS bleeding iruit bleeding iruit; RL is the mixer load resistor assuming there is no loss through the swith and the tail apaitane of the off swith is negligible ompared to the load resistor The basi theory of indutive peaking an be explained with Fig 3 and the step response magine the iruit without the indutor the rise time at the output is about RC if the rise time is defined to be the elapsed time between %-9% of the final output voltage value To derease the harge time ie inrease the bandwidth the indutor is used At t=o there is a sudden step hange in the urrent soure The high impedane of the indutor deouples the resistor from the apaitor whih means all the urrent goes into harging the apaitor Therefore the rise time dereases and hene the bandwidth is enhaned The gain of the mixer is maximized by fast swithing similar to a square wave The turn-on voltage for the swithing pairs is proportional to their overdrive voltage and it needs to be low to ensure fast swithing By having a lower overdrive voltage the size of the load resistors an be inreased to ahieve an even higher gain SMULATON RSULTS The mixer was designed using TSMC's CMOS 3-flm tehnology Simulation was run using Advaned Design System (ADS) software The mixer is designed to operate between -5 GHz with a loal osator (LO) power of dbm Quality fator of peaking indutors and input indutors has been set to 4 and respetively For all simulation results the F is always kept at a onstant 5 MHz while the RF and LO frequenies are being hanged together with the LO being 5 MHz lower than the RF io 5 :s! ' X:-- - ro CJ - ' a o ---J Withl peaking ndudtors Without Peaking 'nduitors RF Frequeny (GHz) Figure 6 Conversion gain of the mixer 6 Figure 5 Complete iruit shemati of the proposed mixer iruit CD :s! (() (f) L Z ' RF Frequeny (GHz) L j / / C Swithing Pairs and Current Bleeding Figure 7 DSB Noise Figure simulation result n general inreasing the bias urrent of the RF transondutane stage makes higher gain and better linearity possible but a larger LO swithing urrent auses voltage headroom issue Therefore as shown in Fig 4 the stati Two soure-follower buffers were used to ombine the differential F signal into a single-ended output 8

4 TABL T COMPARSON OF WDBAND DOWN-CONVRTRS WTH THS WORK Parameters This Work [7J CMOS Tehnology _3 urn 3 urn RF Bandwidth (GHz) Conversion Gain (db) NF DSB(dB) P3 (dbm) LO-to-RF solation (db) 88 N/ A Voltage Supply (V) Power Consumption (m W) [9J 3 urn [l8j [l9j 65 nm 9 nm (Voltage) (SSB) -7 N/ A N/ A N/ A CD - Q; -4 (L :::l B- -6 :::l -8 --' V # /7 Pt -87dV - / y F oult -/ M3lt '' o nput Power (dbm) Figure 8 Output powers of th F and the M3 produt with the inpur at 5 GHz (/) (/) J ::l Q) lr '5 Q V 3 / V V p RF Frequeny (GHz) Figure nput mathing of the mixer 9 The onversion gain of the mixer is measured aross the input frequeny ranging from to 5 GHz The input RF power was kept at -4 dbm Fig 6 shows the onversion gain simulated results This plot also inludes the simulated result without the peaking indutors The importane of the peaking indutors an be learly seen in this plot where there is a muh sharper gain roll off ompared to the simulated result with peaking - -4 ' -6!!! La to F solt on La to F sol lion _ T-T-r-r-r-r-r-r-i-r 3 4 Figure LO Frequeny (GHz) 9 Port-to-Port isolations versus LO frequeny When haraterizing the noise performane of a mixer either the double- or single-sideband NF an be used [3] Fig 7 shows the simulated double-sideband NF of the mixer versus til CJ g (J o ---' ' - - r - ' ' ' F FreQUjCY = 5 MHz f-ro-reqyeny--5-!phz - ' o 5 LO Power (dbm) Figure Conversion gain versus LO power input frequeny The iruit has a low and relatively flat NF aross bandwidth The minimum value of NF is 6 db at 65 GHz and the maximum is 39 db at 5 GHz The third-order intermodulation interept point (P3) of the mixers was simulated To simulate the P3 a two-tone signal separated by MHz was used Shown in Fig 8 is the simulated F and third-order intermodulation (M3) output powers with the input RF frequeny at 5 GHz The extrapolated P3 was - 87 dbm The LO-to-RF port-to-port isolation and LO-to-F port-toport isolation were simulated Sine the LO is 5 MHz lower - 9

5 en ro 5 5 /' / -5 / / - / V /' ) )Ll4 ; F Frequeny (MHz) RF Frquen<fY = -5 rr LO FrjqUenr = i GiZ Figure Simulation results of F bandwidth than the RF the isolation was simulated from 75 GHz to 75 GHz Fig 9 shows the simulated mixer ports isolation Fig shows the input return loss The simulation results of onversion gain versus LO input power is shown in Fig whih shown that dbm LO power is optimum value for this iruit The simulation of F bandwidth is shown in Fig that shows 3-dB bandwidth of onversion gain at the F port is about 7 MHz The mixer ore draws a total urrent of 354 rna and buffers draws 56 rna from a -V supply Table shows a omparison between this work and reently published broadband down-onverters in CMOS The mixer outperforms others in terms of noise performane while st having a omparable gain Their iruit strutures are also different This work and [9] have a urrent reuse struture whereas [8] is a LNA Mixer TA in asade and [9] is a folded mixer with a folded low-noise transondutor V CONCLUSON A double-balaned Gilbert-type mixer based on the positive-negative feedbak tehnique was designed using a 3-um CMOS proess overing the frequeny band between and 5 GHz The noise-anelling tehnique allows broadband input mathing and noise anellation at the same time Together with the urrent-bleeding tehnique a high onversion gain was also ahieved Moreover parasiti apaitanes anellation was done by adding an extra indutor between swithing and transondutane stages to obtain better NF and gain performane The iruit exhibits 9 db average noise figure while the mixer ore drawing only 354 rna form a l-v supply RFRNCS [] H Sjoland A Karimi-Sanjaani and A Abidi A merged CMOS LNA and mixer for a WCDMA reeiver J Solid-State Ciruits vo38 no 6 pp l45-5 Jun 3 3 [] Sahi L Bietti S rba L Tee P Vilmerati and R Castello A 5mW 7 khz lf orner diret onversion CMOS reeiver in Pro Custom Tntegr Ciruits Conf Sep 3 pp [3] T-A Phan -W Kim M-S Kang S-G Lee and C-D Su A high performane CMOS diret down onversion mixer for UWB system rc Trans letron vol 88-C no pp 36-3 De 5 [4] A Lisidini A Mazzanti R Tonietto L Vandi P Andreani and RCastello Single-stage low-power quadrature RF reeiver front-end: The LMV ell J Solid-State Ciruits vol 4 no pp83-84 De 6 [5] S Andersson C Svenson and O Drugge Wideband LNA for a multi standard wireless reeiver in 8 _m CMOS in Pro 9th ULSolid-State Ciruits Con Sep 3 pp [6] A Bevilaqua and A Niknejad An ultrawideband CMOS low-noise amplifier for 3l-O6-GHz wireless reeivers J Solid StateCiruits vol 39 no pp De 4 [7] A Bevilaqua C Sandner A Gerosa and A Neviani A fully integrated differential CMOS LNA for 3-5-GHz ultrawideband wireless reeivers Mirow Wireless Compon Lett vol 6 no 3 pp34-36 Mar 6 [8] F Bruoleri Klumperink and B Nauta Wide-band CMOS lownoise amplifier exploiting thermal noise aneling J Solid StateCiruits vol 39 no pp 75-8 Feb 4 [9] Stanley S K Ho and Carlos Saavedra A CMOS Broadband Low Noise Mixer With Noise Canellation Transations On Mirowave Theory And Tehniques VoL 58 No 5 May [] H Darabi and A A Abidi A 45mW 9MHz CMOS Reeiver for Wireless Paging J Solid-State Ciruits vol 35 no 8 pp Aug [] X Guan A Hajimiri A 4GHz CMOS Front-nd J Solid State Ciruits vo39 issue pp Feb 4 [] Sanghyun Woo Woonyun Kim Chang-Ho Lee Kyutae LimJoy Laskar A 36mW Differential Common-Gate CMOS LNA with Positive Negative Feedbak nternational Solid-State Ciruits Conferene Session / Rf Building Blok 9 [3] W Zhuo X Li Shekhar S H K mbabi J P de Gyvez D JAllstot and Sanhez-Sinenio A Capaitor Cross-Coupled Common-Gate Low-Noise Amplifier Journal of Transations on Ciruits and Systems De 5 no pp [4] Paul R Gray Paul J Hurst Stephen H Lewis Robert G Meyer Analysis and Design of Analog Tntegrated Ciruits 5th dition John Wiley & Sons May 9 O [5] A Lisidini et a Analysis and Design of Contigurable LNAs in Feedbak Common-Gate Topologies Trans Ciruits and Systems- vol 55 no 8 pp Aug8 [6] H Darabi and Chiu A noise anellation tehnique in ative-rf CMOS mixers in Tnt Solid-State Ciruits Conf 5 pp Session 9 [7] S Jeong-Bae K Jong-Ha S Hyuk and Y Tae-Yeoul A Low-Power and High-Gain Mixer for UWB Systems Mirowave and Wireless Components Letters vol 8 pp [8] S Lee J Bergervoet K Harish D Leenaerts R Roovers R van de Beek and G van der Weide A broadband reeive hain in 65 nm CMOS in Tnt Solid-State Ciruits Conf Teh Dig Feb 7 pp 48-6 [9] A Amer Hegazi and H F Ragaie A 9-nm wideband merged CMOS LNA and mixer exploiting noise anellation J Solid State Ciruits vol 4 no pp Feb 7