Tunable Bandpass 4th Order SC Sigma-delta Modulator with Novel Architecture

Transcription

1 Reent dvanes in Eletrial and omputer Enineerin Tunable andpass th Order S Simadelta Modulator with Novel rhiteture JEUNG KIM, MWOONG LEE, KISNG JUNG, SUNGHUL LEE, SEONGIK HO The epartment of Eletronis Enineerin honbuk National University G UKJONG JEONJU JEONUK REULI OF KORE Korea Eletronis Tehnoloy Institute kimjaebun@hanmail.net, minwoon@jbnu.a.kr, kszexes@jbnu.a.kr, siho@jbnu.a.kr bstrat: Tunable S(Swithed apaitor) bandpass ΣΔ(Simaelta) modulator used in wireless system reeiver ours a sinal attenuation aordin to tunin of enter frequeny in sinal bandwidth. In this paper, tunable bandpass th order S bandpass ΣΔ modulator with novel arhiteture is proposed for rejetion of sinal attenuation in sinal bandwidth. The onventional arhiteture uses a ten variable oeffiient values for rejetion of sinal redution in the modulator. ut the proposed arhiteture only use a two variable oeffiient values for rejetion of sinal attenuation in the modulator. lso, an adder and omparator is replaed with a omparator havin inputs in the modulator. Therefore, the onventional arhiteture has one more OM. The proposed modulator was desined in.8 um MOS tehnoloy. The resolution of the modulator within khz bandwidth and MHz samplin frequeny under.7 MHz, MHz and. MHz intermediate frequeny are over bit. KeyWords: Simadelta modulator, andpass, Tunable, ΣΔ modulator Introdution ΣΔ (nalo to iital onverter) is divided into lowpass ΣΔ and bandpass ΣΔ. The lowpass ΣΔ is data onverter with low bandwidth and hihresolution. This is mainly used to onvert the analo sinal into a diital sinal from the sensor. The bandpass ΣΔ used to onvert the data from the wireless system reeiver.[] Fi. (a) is the wireless system reeiver usin bandpass ΣΔ of ommon Superheterodyne. This reeiver use variable loal osillator and bandpass ΣΔ with a fixed enter frequeny but reeiver of Fi. (b) use a loal osillator with a fixed frequeny and a bandpass ΣΔ with a tunable enter frequeny. Therefore, in Fi. (a) the osillator desin is diffiult and problems our by nonlinear of osillator beause the loal osillator with tunable frequeny. On the other hand, in Fi. (b) osillator desin is easy beause of only the loal osillator with a fixed frequeny. In addition, to minimize the problems aused by the osillator an improve the reliability of the system. This bandpass ΣΔ onsists bandpass ΣΔ modulator and eimation parts. s shown in Fi., wireless system reeiver is used S ΣΔ modulator of bandpass ΣΔ. STF (Sinal Transfer Funtion) of modulator has the shape of the bandpass filter. Thereby auses the sinal attenuation within the sinal band. The onventional arhiteture requires the value of the oeffiients in order to determine enter frequeny in the sinal band.[] In addition, the sinal attenuation should be removed in order to keep the STF ain of the modulator is always. This has the disadvantae to adjust value of the oeffiients. Therefore, this paper proposed the Tunable bandpass th order S ΣΔ modulator with novel arhiteture what easy to adjust the enter frequeny in order to overome the disadvantae. In the proposed arhiteture, the sinal attenuation an be eliminated by adjustin the value of the oeffiients. nd dder and omparator are desined as omparator with the inputs. This derease the number of OM used in the iruit than the onventional arhiteture. This paper is oranized as follows. In setion, in order to remove the sinal attenuation propose the Tunable bandpass th order S ΣΔ modulator with the novel arhiteture. nd in setion, the proposed arhiteture was desined at Tr. Level. In setion, proposed Tunable bandpass th order S ΣΔ modulator was simulated by.8um MOS proess parameter, and onsiderin about the ISN:

2 operation feature. Setion was suested the onlusion. (a) (b) Fi. (a) typial radio reeiver with a bandpass ΣΔ. (b) possible radio reeiver with a bandpass ΣΔ with a tunable enter frequeny. The proposed modulator Fi. is a onventional arhiteture of Fi. usin a disrete sinal interator. This ontrol zero point by adjustin the value of the oeffiient of and, thereby the enter frequeny of the S bandpass ΣΔ modulator is tunable. The enter frequeny of the S bandpass ΣΔ modulator is tunable by adjustin the values of and in the onventional arhiteture. eq. () is equation about the enter frequeny Fi. lok diaram of the onventional tunable arhiteture p tan,,,,,,, f () The enter frequeny of S bandpass ΣΔ modulator an be adjusted by, oeffiients. ut the ain for the STF should be always in order to the sinal attenuation is removed. To do this, ten oeffiient values suh as,,,,,,,,,, et. should be adjusted. The other hand, enter frequeny of the proposed arhiteture an be adjusted only two oeffiients and the ain of STF an be always. STF () ( ) ( ) ( ) ( ) NTF () Fi. lok diaram of the proposed th order bandpass ΣΔ modulator Fi. is lok diaram of the proposed th order bandpass ΣΔ modulator, eq. () is STF of the proposed arhiteture and eq. () is NTF (Noise Transfer Funtion). s shown of the eq. (). When the and of NTF is ontrolled, zero point of the proposed arhiteture is shifted and as a result of this, enter frequeny also haned. Reent dvanes in Eletrial and omputer Enineerin ISN:

3 Reent dvanes in Eletrial and omputer Enineerin In STF of eq. (), ain of the STF is beame and removed the sinal attenuation as the ondition of,, and. Table oeffiient values of the proposed Tunable th order bandpass ΣΔ modulator.7 MHz MHz. MHz Table is oeffiients of proposed iruit. When the and beome, enter frequeny of modulator is.7 MHz and when the and beome, enter frequeny is MHz. When the and beome, enter frequeny is. MHz. Table is ompare with the onventional arhiteture and proposed arhiteture when usin the enter frequeny of Tunable S bandpass ΣΔ modulator. In proposed arhiteture, oeffiients are required in order to iruit implement in Fi., and oeffiients are required in table. The oeffiients are not remark, so the number of oeffiient has a ap. The onventional arhiteture is variable for oeffiients in order to ontrol the S bandpass ΣΔ modulator, and oeffiients are variable in order to remove the sinal attenuation. lso in Fi. adder part is desined by usin the OM, however adder of proposed arhiteture is usin the OM beause of the omparator that havin inputs in Fi.. Table omparison of the iruit implementation on the onventional arhiteture and proposed arhiteture # Of all the oeff. needed to implement the iruit # Of the oeff. needed to ontrol f # Of the ap. needed to ontrol f # Of the ap. needed to remove the sinal attenuation # Of the oeff. needed to remove the sinal attenuation # Of the OM needed to implement the iruit # Of the lok needed to implement the iruit f is a enter frequeny. * onventional arhiteture[] roposed arhitetur e The proposed arhiteture is variable for oeffiients in order to ontrol the enter frequeny of S bandpass ΣΔ modulator, no apaitors are variable in order to remove. iruit esription The iruit of the Tunable th order S bandpass ΣΔ modulator that usin the proposed arhiteture is as in the Fi.. esined iruit is onsist of resonator and bit omparator, and use the basi nonoverlappin lok and is desined. Fi. iruit of the proposed arhiteture ISN:

4 Reent dvanes in Eletrial and omputer Enineerin Eq. () is a numerial formula of bit omparator with inputs. Transfer the numerial formula is as followin eq. (). This mean, addin and ompare sinal. In other words, when desin the adder of Fi., instead of not desin iruit by usin OM. dder and omparator is desined by usin bit omparator with inputs. Therefore, the iruit was desined by adder of Fi. and bit omparator with inputs. ( V V ) ( V V ) > VREF REF () (a) S when enter frequeny is MHz V VREF > V VREF () Fi. is nonoverlappin lok what used in the iruit in the Fi., Table is the feature of O M what used in the interator. Fi. Used lok in the iruit Table erformane of folded asade OM Gain d Unity Gain Frequeny 7 MHz hase Marin 7 Slew Rate V/µs Load apaitane pf Simulation Simulation was used by.8um MOS proess parameter, and desined on ondition of samplin frequeny MHz, enter frequeny.7 MHz, MHz,. MHz and bandwidth khz in respetively. Table is operation feature above ondition, the result of S simulation is Fi.. Table erformane of proposed th order S bandpass ΣΔ modulator f.7 MHz MHz. MHz f s MHz MHz MHz andwidth khz khz khz SNR.8 d 8. d. d ynami Rane d 7 d d ower onsumption 8. mw 8. mw 8. mw f is a samplin frequeny. * s (b) S when enter frequeny is. MHz Fi. Results of S (ower Spetral ensity) simulation The proposed th order S bandpass ΣΔ modulator that adjustable the enter frequeny is shown the feature when the enter frequeny is.7, and. MHz, the SNR (Sinal to Noise Rate) is.8, 8. and. d respetively. The enter frequeny of the th order S bandpass ΣΔ modulator was haned by oeffiients of and from.7 MHz to. MHz. SNR have around same property, even hane the enter frequeny. onlusion This paper is proposed Tunable bandpass th order S ΣΔ modulator with novel arhiteture removed the sinal attenuation. The roposed arhiteture and onventional arhiteture of the same thin an be adjusted the enter frequeny by the value of the oeffiients. The onventional arhiteture should ontrol the value of the oeffiients in order to remove sinal attenuation. ut the proposed arhiteture has no oeffiients that are variable in order to remove sinal attenuation. ordin to this, proposed arhiteture has the fewer number of apaitor than onventional arhiteture. dder and omparator what usin in the modulator is omplemented as one iruit. s a result, iruit desin is easy ompared to the onventional arhiteture beause of one less O ISN:

5 Reent dvanes in Eletrial and omputer Enineerin M but exat mathin of the apaitors are required beause the enter frequeny of modulator was haned by and oeffiients. When samplin frequeny is MHz and sinal bandwidth is khz, the proposed tunable bandpass th Order S ΣΔ Modulator with Novel rhiteture have resolution reater than or equal to bit in respetive enter frequeny. The proposed arhiteture an onvert data effetively in wireless systems of Superheterodyne method usin low bandwidth enter frequeny beause of the easy enter frequeny adjustment as well as to remove the sinal attenuation. KNOWLEGMENT This work was sponsored by ETRI SWSo R& enter, Human Resoure evelopment rojet, and the seond stae of rain Korea. Referenes: [] G.Yin and W. Sansen, " hihfrequeny and hihresolution fourth order simadelta / onverter in imos tehnoloy" IEEE J. Solid State iruits, vol.9, pp. 878, u. 99. [] G.Yin and W. Sansen, " hihfrequeny and hihresolution fourthorder simadelta / onverter in imos tehnoloy" IEEE J. Solid State iruits, vol.9, pp. 878, u. 99. [] M.. ElNozahi, M. essouky, and H. F. Raai, "Tunable bandpass sima delta modulators" in ro. th IEEE Int. Midwest Symp. iruits and Systems,, pp. 9. [] Kentaro Yamamoto, nthony han arusone, and Franis. awson, eltasima Modulator With a Widely rorammable enter Frequeny and 8d eak SNR, IEEE Journal of solidstate iruits, vol., no. 8, UGUST 8 ISN: