High-Order CCII-Based Mixed-Mode Uiversal Filter Che-Nog Lee Departmet of Computer ad Commuicatio Egieerig, Taipei Chegshih Uiversity of Sciece ad Techology, Taipei, Taiwa, R. O. C. Abstract This paper presets a ew high-order mixedmode (icludig voltage, curret, trasadmittace, ad trasimpedace modes) uiversal filter structure usig +1 secod-geeratio curret coveyors (CCIIs), grouded capacitors ad +2 resistors, which are the miimum umber of active compoet couts for realizig a th-order mixedmode uiversal filterig resposes (low-pass, high-pass, badpass, bad-reject, ad all-pass) from the same topology. May importat advatages are simultaeously achieved which are (i) usig oly CCIIs (with simpler implemetatio cofiguratio tha the differetial differece curret coveyors (DDCCs) ad fully differetial curret coveyors (FDCCIIs)), (ii) all grouded capacitors (attractive for itegratio), (iii) high output impedace for curret output (good for cascadability), (iv) o eed to impose compoet choice except the voltage ad trasadmittace all-pass respose, (v) o eed of ivertig-type iput sigals or double-type iput sigals for the use of special iput sigals, ad (vi) low sesitivity performace. H-Spice simulatio results cofirm the theory. Keywords Active filters, secod-geeratio curret coveyors, mixed-mode, high-order filter, uiversal filter. I. INTRODUCTION Over the last decade, may high-order voltage-mode or curret-mode filters have bee preseted i the literature [1-17]. From historical progress poit of view, we might ited to replace the traditioal voltage-mode circuits with the more precise curret-mode circuits. There might be a trasferrig period from voltage-mode to curret-mode world. The, the trasadmittace (i.e. iput as voltage ad output as curret) ad trasimpedace (i.e. iput as curret ad output as voltage) modes will be ivolved i that betwee voltage ad curret modes, ad therefore, play a very importat role i the special filterig applicatios where we eed to coect a voltage-mode circuit with a curret-mode circuit ad vice versa. Hece, i aalog sigal processig applicatios, we may be desirable to have active filter with iput currets or voltages ad output currets ad voltages, defied as mixed-mode filter. Therefore, the mixed-mode (icludig voltage, curret, trasadmittace, ad trasimpedace modes) circuits are worthy of researches ad preseted for the use of ay filterig requiremet which is compatible with moder microelectroic systems applicatios, such as cotrols ad voice ad data commuicatios, where cosideratio of size ad weight make the use of iductors prohibitive. Although may mixed-mode biquad filters have bee proposed, few high-order mixed-mode filters have bee preseted i the literature [15, 18-20]. I 2009, a th-order mixed-mode filter was proposed [19]. The filter structure [19] employs +2 operatioal trascoductace amplifiers (OTAs) ad grouded capacitors, which ca realize thorder mixed-mode (icludig voltage, curret, trasadmittace, ad trasimpedace modes) uiversal filterig resposes (low-pass, high-pass, bad-pass, badreject, ad all-pass) from the same topology. However, the structure [19] offers three followig disadvatages: (i) eed of extra ivertig amplifiers for realizig voltage ad trasadmittace modes allpass sigals, (ii) eed of the two same th iput curret (I ) for costructig curret output ad voltage output, ad (iii) icoveiet iput currets settigs for realizig curret ad trasimpedace modes highpass, badreject, ad allpass sigals. Therefore, i 2012, a ew th-order mixed-mode filter was proposed [20]. The structure, reported i [20], ca overcome the above three disadvatages but it eed to use +3 active elemets (i.e. OTAs) i additio to grouded capacitors. Although the th-order mixed-mode structure reported i [18] uses oly +1 active elemets (i.e. DDCCs) i additio to grouded capacitors ad +2 resistors, the DDCCs are more complex active elemets tha CCIIs. I 2009, a good high-order curret-mode ad trasimpedace-mode uiversal filter was proposed i [15]. The filter [15] employs oly +1 active elemets (i.e. multiple outputs CCIIs (MOCCIIs)) i additio to grouded capacitors ad +1 resistors but it ca ot be used i voltage ad trasadmittace modes. 32
Therefore, this leads to prospective research work: ivestigatig ad developig a high-order mixed-mode (icludig voltage, curret, trasadmittace, ad trasimpedace modes) uiversal filter structure usig reduced umber (o more tha +1) of active compoets which have the simpler structure tha DDCC. I this paper, the proposed high-order mixed-mode uiversal filter uses oly +1 CCIIs (with the simpler structure tha DDCC), i additio to grouded capacitors ad +2 resistors, which ca realize th-order voltage, curret, trasadmittace, ad trasimpedace modes uiversal filterig resposes (lowpass, high-pass, bad-pass, bad-reject, ad all-pass) from the same topology. It should be oted that up util ow, o previous papers have reported a high-order CCII-based mixed-mode uiversal filter. Moreover, the proposed highorder mixed-mode circuit does ot eed the two same th iput curret (I ) for costructig curret output ad voltage output ad also does ot eed extra ivertig-type or double-type amplifiers for special iput sigals. Furthermore, the ew proposed structure provides more coveiet iput curret settigs tha [19] for realizig curret ad trasimpedace modes highpass, badreject, ad allpass sigals. For example, the ew structure uses a sigle curret iput sigal istead of same curret iput sigals [19] for realizig the th-order high-pass filter respose. Therefore, the proposed circuit also ca overcome the above three disadvatages. With respect to the refereces [19, 20], the proposed structure uses less umber of active compoets. With respect to the referece [18], the proposed circuit uses the active compoets with simpler structure. With respect to the referece [15], the proposed circuit ot oly realizes high-order curret-mode ad trasimpedace-mode uiversal filterig resposes but also achieves high-order voltage ad trasadmittace modes uiversal filterig resposes. II. HIGH-ORDER CCII-BASED MIXED-MODE FILTER Figure 1 shows the proposed mixed-mode th-order uiversal filter structure where I, I -1, I -2,, I 2, I 1, I 0 are the filter iput currets ad V, V -1, V -2,, V 2, V 1, V 0 are the filter iput voltages whose settig determie the filter fuctios as show later, I out ad V out are the filter curret output ad voltage output, respectively. The choice of the subscript +/- of the output termial Z +/- i the CCII() depeds o a eve/odd order of the high-order filter, respectively. Usig stadard otatio, the port relatios of a CCII ca be characterized by I Y = 0, V X = V Y ad I Z ± = ± I X. The multiple curret outputs of CCII() ca be simply recostructed usig curret mirrors. Moreover, all curret outputs have very high output impedace. 33 Routie circuit aalysis for Figure 1 yields the followig trasfer fuctios: V Figure 1. Proposed mixed-mode th-order uiversal filter structure. out ad I out i which Nv( s) N ( s) i (1) G D( ) 1 s Nv( s) N ( s) i (2) D( s) i i 1 aigiv is Nv( s) (3) i0
i i 1 aiiis N ( s) (4) i i0 i D( s) 1 ais (5) i0 where a C i i1 (6) k a k Ci G j for k 1,2,3,..., 1 (7) i1 jk1 a0 G j (8) j1 From equatio (1)-(8), the high-order mixed-mode uiversal filter trasfer fuctios are obtaied accordig to iput voltage or curret coditios as follows. Part I: If I = I -1 = I -2 = = I 2 = I 1 = I 0 = 0, the followig th-order voltage-mode ad trasadmittacemode filter resposes ca be obtaied as below. (i) Highpass: V = V i, ad all the other iput voltages are zero (grouded). (ii) Lowpass: V 0 = V i, ad all the other iput voltages are zero (grouded). (iii) badpass: If is eve, the V (/2) = V i, whilst all the other iput voltages are zero (grouded). If is odd, the the iput curret V i is applied to either V (-1)/2 or V (+1)/2, whilst all the other iput voltages are zero (grouded). (iv) Bad-reject: V = V 0 = V i, ad all the other iput voltages are zero (grouded). (v) All-pass: V = V -1 = V -2 = = V 2 = V 1 = V 0 = V i ad G = G -1 = = G 1 = G 0 Part II: If V = V -1 = V -2 = = V 2 = V 1 = V 0 = 0, the followig th-order curret-mode ad trasimpedacemode filter resposes ca be obtaied as below. (i) Highpass: I = I i, ad all the other iput currets are zero. (ii) Lowpass: I 0 = I i, ad all the other iput currets are zero. (iii) badpass: If is eve, the I (/2) = I i, whilst all the other iput currets are zero. If is odd, the the iput curret I i is applied to either I (-1)/2 or I (+1)/2, whilst all the other iput currets are zero. (iv) Bad-reject: I = I 0 = I i, ad all the other iput currets are zero. (v) All-pass: I = I -1 = I -2 = = I 2 = I 1 = I 0 = I i. Note that there are o critical compoet-matchig coditios or cacellatio costraits i the desig except the trascoductace/voltage allpass respose. Moreover, the structure does ot eed ivertig-type iput curret sigals or double-type amplifier for realizig ay filter trasfer fuctios ad also does ot eed to chage the etwork topology. Observig all of the coefficiets i D(s) (i.e., a i,), because a cosists of the product of all capacitaces,, a -i cosists of the product of -i capacitaces ad i coductaces, ad a 0 cosists of the product of all coductaces, all filterig parameters produced from the coefficiet i the deomiator are orthogoally cotrollable. I additio to this advatage, the coefficiet sesitivity to each capacitace or each coductace is easily calculated ad equal to 0 or 1, both of which are low. To illustrate the proposed mixed-mode high-order filter structure, Figure 2 shows a sixth-order trasadmittace-mode ad voltage-mode highpass filter. Figure 3 shows a sixth-order curret-mode ad trasimpedace-mode badpass filter. Figure 4 shows a sixth-order trasadmittace-mode ad voltage-mode lowpass filter. 34
Figure 2. Proposed sixth-order trasadmittace-mode ad voltagemode high-pass filter structure. Figure 3. Proposed sixth-order curret-mode ad trasimpedacemode bad-pass filter structure. 35
III. H-SPICE SIMULATIONS A CMOS implemetatio of the CCII± is show i Figure 5 [21] with the NMOS trasistor aspect ratios (W/L=5μm/1μm) ad PMOS trasistor aspect ratios (W/L=10μm/1μm). Note that the multiple curret outputs of CCII applyig the realizatio of curret replicas are very simple. To verify the theoretical aalysis of the high-order mixed-mode uiversal filters, the H-SPICE simulatios, usig the TSMC 0.25μm process for the proposed circuits of Figure 1, were performed with the compoet values: (i) R 0 = R 1 = = R 6 = R 7 = 10kΩ, ad C 1 = C 2 = = C 5 = C 6 = 5pF for the sixth-order high-pass, low-pass, bad-pass, ad bad-reject filters of the Figure 1, leadig to a ceter frequecy of f 0 = 3.183MHz, ad (ii) C 1 = C 2 = C 3 = 5pF, R 1 = 20kΩ, R 2 = 10kΩ, ad R 3 = 5kΩ for the third-order allpass filter of the Figure 1, leadig to a ceter frequecy of f 0 = 3.183MHz. Their supply voltages are V DD =-Vss = 1.25V, V b1 = -0.3V, ad V b2 = -0.6V. Figure 6 presets the simulated sixth-order lowpass, badpass, highpass, ad bad-reject amplitude-frequecy resposes of the proposed voltage-mode (VM) ad trasadmittace-mode (TAM) filters with the ormalized trasadmittace magitude = 20 log 10000I out / V i db due to R 7 =10 kω. Figure 7 presets the simulated third-order all-pass phase ad amplitudefrequecy resposes of the proposed curret-mode (CM) ad trasimpedace-mode (TIM) filters with the ormalized trasimpedaces magitude = 20 log V out / 10000 I i db due to R 7 =10 kω. Although ot icluded i this paper, it ca be show that the other simulated results are very similar to the above simulated results. As ca be see, there is a close agreemet betwee theory ad simulatio. Figure 4. Proposed sixth-order trasadmittace-mode ad voltagemode low-pass filter structure. 36
phase(degree) magitude(db) magitude(db) Iteratioal Joural of Emergig Techology ad Advaced Egieerig -20-40 -60-80 -100-120 -140 Figure 5. CMOS implemetatio of the CCII±. 0 10 6 10 7 frequecy(hz) Figure 6. Amplitude-frequecy resposes of the proposed ormalized TAM ad VM sixth-order filterig sigals (, simulated highpass; *, simulated lowpass; Δ, simulated badpass;, simulated badreject; ad,theoretical curve ). 200 100 0-100 -200-300 -400 10 4 10 5 10 6 10 7 frequecy(hz) Figure 7. Phase ad amplitude frequecy resposes of the proposed ormalized TIM ad CM third-order all-pass sigals (*, simulated phase;, simulated amplitude; ad,theoretical curve). 20 10 0-10 -20-30 -40 IV. CONCLUSIONS Usig oly +1 CCIIs, grouded capacitors, ad +2 resistors, a mixed-mode uiversal high-order filter is preseted which ca realize th-order lowpass, highpass, badpass, bad-reject, ad allpass resposes. Moreover, the proposed high-order circuit offers the followig advatages: the miimum active compoets, usig grouded capacitors attractive for itegratio, high output impedace good for cascadability, o eed to chage the filter topology, o compoet-value costraits except the trasadmittace/voltage allpass respose, o eed of ivertig or double-type amplifiers for special iput sigals, ad low active ad passive sesitivities. As far as active compoets is cocered, the proposed th-order mixedmode uiversal filter usig +1 CCIIs is the miimum active compoets. H-Spice simulatios cofirm the theoretical predictios. Ackowledgemets The author would like to thak the Miistry of Sciece ad Techology (formerly Natioal Sciece Coucil) of Taiwa, R. O. C. The Miistry of Sciece ad Techology, Taiwa, R. O. C. supported this work uder grat umber NSC 102-2221-E-149-004-. REFERENCES [1] C. M. Chag, ad B. M. Al-Hashimi, Aalytical sythesis of curret-mode high-order OTA-C filters, IEEE Tras. Circuits Syst. I: Fudam. Theory Appl., vol. 50, o. 9, pp. 1188-1192, 2003. [2] C. M. Chag, B. M. Al-Hashimi, Y. Su, ad J. N. Ross, New highorder filter structures usig sigle-eded-iput OTAs ad grouded capacitors, IEEE Tras. Circuits Syst. II: Exp. Briefs, vol. 51, o. 9, pp. 458-463, 2004 [3] C. M. Chag, C. L. Hou, W. Y. Chug, J. W. Horg, ad C. K. Tu, Aalytical sythesis of high-order sigle-iput OTA-grouded C all-pass ad bad-reject filter structures, IEEE Tras. Circuits Syst. I: Regular Papers, vol. 53, o. 3, pp. 489-498, 2006. [4] C. M. Chag, Aalytical sythesis of the digitally programmable voltage-mode OTA-C uiversal biquad, IEEE Tras. Circuits Syst. II: Exp. Briefs, vol. 53, o. 8, pp. 607-611, 2006 [5] S. H. Tu, C. M. Chag, N. J. Ross, ad M. N. S. Swamy, Aalytical sythesis of curret-mode high-order sigle-eded-iput OTA ad equal-capacitor elliptic filter structures with the miimum umber of compoets, IEEE Trasactios o Circuits ad Systems-Part I: Regular Papers, vol. 54, o. 10, pp.2195-2210, 2007. [6] C. M. Chag, A. M. Solima, ad M.N.S. Swamy, Aalytical sythesis of low-sesitivity high-order voltage-mode DDCC ad FDCCII-grouded R ad C all-pass filter structures, IEEE Trasactios o Circuits ad Systems-Part I: Regular Papers, vol. 54, o. 7, pp. 1430-1443, 2007. [7] C. M. Chag, ad M. N. S. Swamy, Aalytical sythesis ad compariso of voltage-mode th-order OTA-C uiversal filter structures, Iteratioal Joural of Circuit Theory ad Applicatios, vol. 40, o. 5, pp. 421-454, 2012. 37
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