International Journal of Computer Theory and Engineering, Vol. 4, No. 1, February 01 The Cacode and Cacaded Technique LNA at 5.8Hz Uing T-Matching Network for WiMAX Application Abu Bakar Ibrahim, Abdul Rani Othman, Mohd Nor Huain, and Mohammad Syahrir Johal Abtract Thi project preent the cacode and cacaded technique LNA at 5.8Hz uing T-matching network applicable for worldwide interoperability for microwave acce (WIMAX) application. The amplifier ue FHX76L Low Noie SuperHEMT FET. The LNA deigned ued T-matching network coniting of lump element reactive element at the input and the output terminal. The cacode and cacaded low noie amplifier (LNA) produced gain of 5.4dB and noie figure (NF) at 1.3dB. The input reflection (S 11 ) and output return lo (S ) are -19.71dB and -10.07dB repectively. The bandwidth of the amplifier i more than 1.4Hz. The input enitivity i compliant with the IEEE 80.16 tandard. Index Term Cacode-cacade LNA, radio frequency, T-matching network I. INTRODUCTION The modern wirele communication ytem demand high data rate and high mobility performance during the lat few year [1]. Worldwide interoperability for microwave acce (WiMAX), which i hort for Worldwide Interoperability for Microwave Acce, i a novel wirele communication technology. It i an attractive technology due to the high tranmitting peed (up to 70Mbp) and long tranmitting ditance (up to 30 mile). The ytem bae on IEEE 80.16 tandard and ue everal band (.3-.7 Hz, 3.4-3.6 Hz and 5.1-5.8Hz) to tranmit data. The deign of the front-end low noie amplifier (LNA) i one of the challenge in radio frequency (RF) receiver, which need to provide good input impedance match, enough power gain and low noie figure (NF) within the required band []. Many high gain amplifier topologie have been propoed a a way to atify the requirement for low power diipation a well a good performance. The cacode with cacaded technique to produce reult in a higher bandwidth and gain, due to the increae in the output impedance, a well a better iolation between the input and output port [3], [4]. Mot of the ingle tage LNA device in the review could only around 0 db gain. It wa propoed that the low noie amplifier hould have a gain of at leat 30 db [5]. By taking conideration the extenion of communication ditance of up to 50 km [5]. A budgeted high gain of LNA will enure a good ignal to noie eparation for further amplification. For thi gain of 50 db, a cacode with cacaded amplifier i introduced for the low noie amplifier a how in Fig. 1. Cacode Cacaded Fig. 1. Cacode and cacaded LNA II. THEORETICAL ASECTS Baically, deigning an amplifier, the input and output matching network are conider to achieve the required tability, mall ignal gain, and bandwidth. Super high frequency amplifier i a typical active circuit ued to amplify the amplitude of RF ignal. Baic concept and conideration in deign of uper high frequency amplifier i preented in thi paper. The LNA deigned, the formula and equation were referred to [6]. Fig., how a typical ingle-tage amplifier including input/output matching network. Fig.. Typical amplifier deign The baic concept of high frequency amplifier deign i to match input/output of a tranitor at high frequencie uing S-parameter frequency characteritic at a pecific DC-bia point with ource impedance and load impedance. Input/output matching circuit i eential to reduce the unwanted reflection of ignal and to improve efficiency of the tranmiion from ource to load [6], [7]. A. ower ain Several power gain were defined in order to undertand operation of uper high frequency amplifier, a hown in Fig. 3, power gain of -port circuit network with power impedance or load impedance at power amplifier repreented with cattering coefficient are claified into Operating ower ain, Tranducer ower ain and Available ower ain [6], [7]. Manucript received October 4, 011; revied January 10, 01. The author are with Univeriti Teknikal Malayia Melaka, Malayia (e-mail: rani@utem.edu.my). Fig. 3. I/O circuit of -port network 93
International Journal of Computer Theory and Engineering, Vol. 4, No. 1, February 01 B. Operating ower ain Operating power gain i the ratio of power ( L ) delivered to the load (Z L ) to power ( in ) upplied to -port network. ower delivered to the load i the difference between the power reflected at the output port and the input power, and power upplied to -port network i the difference between the input power at the input port and the reflected power. Therefore, Operating ower ain i repreented by where, in indicate reflection coefficient of load at the input port of -port network and i reflection coefficient of power upplied to the input port. C. Tranducer ower ain Tranducer ower ain i the ratio of av (1), maximum power available from ource to, power delivered to the load. A maximum power i obtained when input impedance of circuit network i equal to conjugate complex number of power impedance, if in =, tranducer power gain i repreented by T ower delivered to the load ower Available from the ource L S1 (1 S )(1 L ) (1 S )(1 S ) ( S S ) av 11 S L 1 1 S L L indicate load reflection coefficient. where, D. Available ower ain Available ower ain, available from the ource, to L av () A i the ratio of, power, power available from - port network, that i, avn A. ower gain i avn when = in * A av avn. Therefore Available ower ain i given by: ower available from the amplifier ower available from the ource (3) S S avn 1 S 1 S 1 av 1 11 S 1 L That i, the above formula indicate power gain when input and output are matched [7]. E. Noie Figure Signal and noie applied to the input port of amplifier were amplified by the gain of the amplifier and noie of amplifier itelf i added to the output. Therefore, SNR (Signal to Noie Ratio) of the output port i maller than that of the input port. The ratio of SNR of input port to that of output port i referred to a noie figure and i larger than 1 db. Typically, noie figure of -port tranitor ha a minimum value at the pecified admittance given by formula: RN F Fmin Y Y (4) S For low noie tranitor, manufacture uually provide F, R, Y N min by frequencie. N defined by formula for deired noie figure: N F Fmin 1 S 4 RN / Z0 1 F. Condition for Matching The cattering coefficient of tranitor were determined. The only flexibility permitted to the deigner i the input/output matching circuit. The input circuit hould match to the ource and the output circuit hould match to the load in order to deliver maximum power to the load. After tability of active device i demand, input/output matching circuit hould be deigned o that reflection coefficient of each port i correlated with conjugate complex number a given below [8]: S S (5) (6) * 1 1 S OUT L S (7) 1 S11 S The noie figure of the firt tage of the receiver overrule noie figure of the whole ytem. To get minimum noie figure uing tranitor, power reflection coefficient hould match with and load reflection coefficient hould match with * out = (8) S S L S * 1 1 out 1S11 III. DESIN OF LNA Low noie amplifier ha been deign baed on the -parameter were obtained from calculation and imulation uing ADS. The S-parameter for each LNA how in TABLE I and TABLE II. TABLE I: S-ARAMETERS OF CASCODE LNA Freq/dB S 11 S 1 S 1 S 5.8Hz 0.71 0.065 8.994 0.37 Angle -86.54 33.878 178.66-10.456 TABLE II: S-ARAMETERS OF SINLE LNA Freq/dB S 11 S 1 S 1 S 5.8HZ 0.637 0.040.873 0.536 Angle -89.645 9.157 86.557-4.058 The overall performance of the low noie amplifier i determined by calculating the tranducer gain T, noie figure F and the input and output tanding wave ratio, VSWR IN and VSWR OUT. The imum, Γ and Γ L were (9) 94
International Journal of Computer Theory and Engineering, Vol. 4, No. 1, February 01 obtained a Γ = 17.354 + j50.13 and Γ L = 79.913-j7.304 for ingle LNA. While, Γ = 1 + j48.881 and Γ L = 79.913- j7.304 for cacode Low noie amplifier. TABLE III: LNA ARAMETERS Item Component of Matching Cacode LNA Single LNA L 1 6.14 nh 3.661 nh L.4 nh 0.8799 nh L 3 1.55 nh 3.60 nh L 4 1.6 nh 0.88 nh C 1 0.315 pf 0.5 pf C 49.9fF Fig. 4. The chematic circuit for cacode LNA Fig. 4 how, the complete chematic circuit of 5.8 Hz a cacode Low noie amplifier. The method employed here i inductive ource degeneration. Thi degeneration inductor enable more flexibility in matching the input tage to 50Ω. It alo influence the gain of LNA. Cacoding tranitor i ued to reduce the interaction of the gate-drain capacitance C gd of lower tranitor. To increae flexibility and reduce the cope of poibilitie the gate of cacoding tranitor i aigned a maximum voltage by connecting it to V DD. The paive element in the input matching network are L 1, L and C 1.While; the paive element in the output matching network are L 3, L 4 and C. Combination of L S and L will tune the input to the deired frequency [4]. The cacoding tranitor conit of an inductor L D, it called peaking tructure to enhance gain and bandwidth [9]. Thi tranitor alo improve the revere iolation and lower miller effect [10]-[13]. Fig. 5 how the completed chematic circuit of 5.8 Hz a ingle LNA. It alo ued ource degeneration topology and an inductor L wa inerted to provide the deired input reitance and to improve the tability of amplifier. The paive element in the input matching network are L 1, L and C 1. While; element L 3 and L 4 are paive element in the output network. For high gain amplification everal amplifier are cacaded in erie [11]. It can be deigned a one unit or all amplifier are matched to 50Ω and connected in erie. A T-matching network i ued to match the input impedance. Uing Smith Chart matching technique, the component value are hown in TABLE III. To achieve the targeted overall gain of 50dB; it i decided to deign cacode and cacaded technique. IV. SIMULATION RESULT TABLE IV how the -parameter output for comparion of LNA. It i imulated uing Advanced Deign Sytem (ADS). The imulation recorded that the amplifier gain S 1 i 53.4 db. The input inertion lo S 11 i -4.3dB, overall noie figure (NF) i 1.dB and the output inertion lo S i -3.86dB.The reflection lo S 1 i -6.6dB. Thee value were within the deign pecification and were accepted. The output S-parameter are hown in Fig. 6a, 6b and 6c. Fig. 6a. S-parameter for cacode LNA Fig. 6b. S-parameter for cacaded Fig. 6c. S-parameter for cacode and cacaded TABLE IV: COMARISON OF OUTUT LNA Fig. 5. The chematic circuit for ingle LNA S-arameter S 11 S 1 S 1 S NF (k) (db) Cacode LNA -18.9 -.1 19.5-0.0 1. 1.0 Cacaded LNA -.5-40.4 34-37.6 0.76 1.9 Cacode and Cacaded LNA -4.3-6.6 53.4-3.86 1.0 1.59 TABLE V: S-ARAMETERS MEASURED 95
International Journal of Computer Theory and Engineering, Vol. 4, No. 1, February 01 S arameter Targeted Meaured Input Reflection S 11 db <-10 db -19.71 Return Lo S 1 db <-10 db -65.7 Forward tranfer S 1 db >50 db 5.4 Output ReflectionS db <-10 db -10.07 NF db <3 db 1.3 BW MHz >1000 140 V. MEASUREMENT Referring to the meaurement etup hown in Fig. 7, the S parameter of the amplifier; wherea S 11, S 1, S 1 and S are meaured uing the network analyzer. The gain of the amplifier i meaured uing the etup in Fig. 8. The noie figure value and 3dB bandwidth were obtained from the etup in Fig. 9. Before recording all meaurement, a tandard procedure of calibration i conducted to enure that the meaurement tool were calibrated. Fig. 7. Setup for device under tet meaurement uing network analyzer required S 1 obtained i le than -65.7 db. The related meaured gain S 1 for the LNA amplifier i 5.4 db meaured uing the etup in Figure 6. The noie figure value obtained from etup in Figure 8 i 1.37 db which complied with the targeted value of le 3 db. The ue of T lump reactive element and microtrip line matching technique at the input of the LNA contribute the bet performance for the amplifier [9]. Thi matching technique wa ued to provide high-loaded Q factor for better enitivity and thu minimized the noie figure. The element of T-network were realized in the form of lump reactive element and microtrip line impedance. The 3 db bandwidth for the amplifier i meaured uing etup Fig. 7. The 3dB bandwidth obtained i 1.4 Hz compliant with targeted reult of more than 1 Hz. The meaured parameter for the LNA were alo compliant with the equation (1) to (9) uing MathCAD analyi. VII. CONCLUSION A low noie amplifier ha been imulated and developed uccefully with IEEE tandard 80.16 WiMAX. It i oberved that the imulated and experiment reult have not much different. It oberved that the gain of the imulated analyi i 53.4 db and the experimental value i 5.4 db. It i important to take note when deigning the amplifier to match the amplifier circuit. The 5.8Hz LNA ha been developed uccefully and the circuit cab contributed to the front end receiver at the decribed frequency. For better performance in gain of the amplifier, it can be achieved by increaing the number of tage to improve the gain and noie figure of the deign [11]. Higher gain would expand the coverage or communication ditance. Fig. 8. Frequency repone meaurement etup for device under tet. Fig. 9. Meaurement etup for device under tet for noie figure VI. RESULT The reult for LNA RF front-end module i preented in Table V. From the tabulated value, the S 11 parameter meaured i -19.71 db. Thi i -9.71 db le than targeted value which i better and acceptable. S meaured i -10.07 db which i le than targeted and acceptable. The return lo REFERENCES [1] C. W. Chang and Z.-M. Lin, A 1V 14.6dB ain LNA for WIMAX - 6Hz Application, IEEE roceeding, 009. [] R.-L. Wang, S.-C. Chen, C.-L. Huang, C.-H. Lie, and Y.-S. Lin, -6Hz Current-Reued LNA With Tranformer-type Inductor, IEEE roceeding, 008. [3] Leon, M. A.. Lorenzo and M. T.. De., Comparion of LNA Topology for Wimax Application in a Standard 90-nm CMOS roce, 1th International Conference on Computer Modelling and Simulation, pp. 64-647, 01. [4] M. ozar, David. Microwave and RF Wirele Sytem. Third Avenue, N.Y.John Wiley & Son, in 001. [5] onzalez, uillermo. Microwave Tranitor Amplifier. 1996. [6] A. R. Othman, A. H. Hamidon, J. T. H Ting, and M. F. Mutaffa, High ain Cacaded Low Noie Amplifier Uing T-Matching Network, 4 th ISBC 010. [7] Weber, W. Wang and Robert. Deign of a CMOS Low Noie Amplifier (LNA) at 5.8Hz and it Senitivity Analyi, 11 th NASA Sympoium 003. [8] IEEE Computer Society and IEEE Microwave Theory Technique and Society. art 16 Air Interface for Fix Broadband Wirele Sytem, IEEE Standard vol. 80, no. 16. 004 [9] D. Ayadi, S. Rodriguez, M. Loulou, and M. Imail, Sytem Level Deign of Radio Frequency Receiver for IEEE 80.16 Standard, IEEE roceeding, 009. [10] R. C.-H. Li. RF Circuit Deign, 009. [11] I. J. Bahl. Fundamental of RF and Microwave Tranitor Amplifier, 009. [1]. Bhartia and I. Bahl, Microwave Solid State Circuit Deign, nd Edition, J Wiley, 003. [13] A. Baihya,.. Sahu, and M. K. Nakar. A High ain Low Noie Amplifier for 0.9 6Hz Wirele Application, IEEE roceeding, 011. 96
International Journal of Computer Theory and Engineering, Vol. 4, No. 1, February 01 Abu Bakar Ibrahim received the B.S degree in electrical engineering and mater degree from Univerity of Technology Malayia in 1998 and 000 repectively. Currently i working toward the h.d. degree in development of low noie amplifier front-end receiver for wirele application at the Univeriti Teknikal Malayia Melaka. Email: abupp@gmail.com Mohd Nor Huain received B.S in electrical and Electronic Engineering from Univerity of Strathclyde and mater degree in electronic communication from Univerity of Eex England. He received h.d. in ical and waveguide from Univerity of Bath England and now he joined Univeriti Teknikal Malayia Melaka. Email:drmohdnor@utem.edu.my Abdul Rani Othman received B.eng in electrical and Electronic from Univerity of Strathclyde and mater degree in electrical and electronic from Univerity Technology of Malayia. He received h.d. in RF front-end receiver for wirele application from Univerity of Teknikal Malayia Melaka and now he joined Univeriti Teknikal Malayia Melaka. Email: rani@utem.edu.my Mohammad Syahrir Johal received B.S in electrical Engineering from Univerity of Wetern Ontario and mater degree in electrical engineering from Univerity Technology of Malayia. Now he joined Univeriti Teknikal Malayia Melaka. Hi reearch interet include propagation wirele digital communication.email: yahrir@utem.edu.my 97