Active Frequency Filters with High Attenuation Rate

Transcription

1 Active Frequency Filters with High Attenuation Rate High Performance Second Generation Current Conveyor Vratislav Michal Geoffroy Klisnick, Gérard Sou, Michel Redon, Jiří Sedláček DTEEE - Brno University of Technology (Brno, Czech Republic) LGEP-Supélec L2E UPMC (Paris, France) ISCAS - Paris, June 2 nd 21

2 Motivation CCII- biquadratic section High-performance CCII 3/16 I. Motivation

3 Motivation CCII- biquadratic section High-performance CCII 3/16 Real-world frequency filters Non-ideal passive components: f,q inaccuracy, higher order effects, can be compensated [*] Non-ideal active components f,q inaccuracy, DC offset, attenuation N [db] db/dec f Z 4 log F -4dB/dec 2dB/dec db/dec triple zero double zero Parasitic zeros can not be compensated by predistortion [**] F Effect of parasitic zeros in the AC response of frequency filter f Z [*] Geffe, P. R., IEEE Trans., Vol. CAS-23, pp.45-55, 1976 [**] Schmid, H. Moschytz, G.S, Circuits and Systems, vol.1, 1998, p

4 Motivation CCII- biquadratic section High-performance CCII 4/16 High-order filters Cascade realization db 2 nd order ( s+ a1 Ω1) ( s +Ω ) 1 2 Ω2 2 a2 s + b2 s+ c2 Ω2 Q2 2 Ω 2 2 s + s+ω2 Q2 2 Ω 2 n an s + bn s+ c Ω 2 n Qn 2 Ω n 2 s + s+ωn Qn -2 db -4 db 4 th order 6 th order Non-cascade (FNDR realization) 2 LM741 f (a.u.) f z 1 2π GBW 2π C R Using low quality active block require high filter order to attain high attenuation rate [*] V. Michal et al. Non-ideal performance of active biquadratic filter blocks. Speto int conference (26) [**] V. Michal et al. Active filters based on goal-directed lossy RLC prototypes, Speto int conference (26)

5 Motivation CCII- biquadratic section High-performance CCII 5/16 Example: real Sallen-Key filter -2 LP Sallen-Key biquad [*] -4 I C Parasitic zero occurs at : f Z = 1 2π GBW 3 2π R RCC parasitic transfer zeros in the stopband [*] Sallen.R.P-Key.E.I., Circuit Theory. Vol

6 Motivation CCII- biquadratic section High-performance CCII 6/16 Real Sallen-Key: parasitic zero removal f Z (2) 1 2 π A ω CR 1 P OUT reduced order of the root, only R out and C 1 contribute to the frequency Higher attenuation Improved Type II Sallen-Key f 4 log f Z1 Z Comparison of v OUT1 and v OUT Impedance level (C 1 )scaling V. Michal et al. Low-pass biquadratic filters with high suppression rate, Electronics Letters, Volume 45, Issue 12, p (29)

7 Motivation CCII- biquadratic section High-performance CCII 7/16 III.1 CCII biquadratic section

8 Motivation CCII- biquadratic section High-performance CCII 8/16 Proposed solutions Removal of the parasitic zeros ensures constant -4dB roll-off off Division of the frequency band in two regions: Region up to f, where the DC transfer and resonance gain are ensured by the active element Stop-band region, where the high attenuation is ensured by the passive RC filter Design rules: Interruption of direct signal way, Passive filters containing grounded capacitors Adopted solution: topological transformation of circuits presented in [*] [*] Liu, S-I., Tsao,H-W; Wu,J., Tsay, J-H. "Realizations of the single CCII biquads with high input impedance", IEEE Symposium on Circuits and Systems, 1991.

9 Motivation CCII- biquadratic section High-performance CCII 9/16 New biquadratic section CCII- f = 2π 1 RRCC R CC 1 R Q = = R C 1 1+ C2 2 R1 C1= C2-2 CCII- low-pass biquadratic section with eliminated parasitic transfer zero Stop band behavior (single pole model of CCII): 2 Ω H() s = 2 2 ( s + s Ω Q +Ω ) ( ωp A + s) ( 1 ) A ( ωp +α + s) measured AC response of 1MHz 4 th order LP filter V. Michal et al. Low-pass biquadratic filters with high suppression rate, Electronics Letters, Volume 45, Issue 12, p (29)

10 Motivation CCII- biquadratic section High-performance CCII 1/16 Summary of achieved features 2 F : 1.5M 5M 1M 2M 5M The attenuation is only limited by signal leakage N [db] Does not depend on the f -2 Using low-performance voltage buffer is allowed -4 2 nd cascade FDNR LP Direct connection to the DAC input -6 1k 5 1M 1 6 1M 7 1M 8 5M f [Hz] Attenuation floor independent of the f. comparison with lossy R-FDNR biquad [*] price and power consumption are reduced [*] Martinek, P. Radioelek, 26

11 Motivation CCII- biquadratic section High-performance CCII 11/16 III.2 High performance CCII current conveyor

12 Motivation CCII- biquadratic section High-performance CCII 12/16 CCII- with very low output resistance voltage buffer r out vout 2 r2 + 1 = = i r g + r r g g + g out 2 mf 1 2 mo m m Design of low-r out CCIIsimplified small signal model 2 r g 1 mo g m Hassan O. et al, Circuit and Systems II, Vol. 49 (22)

13 Motivation CCII- biquadratic section High-performance CCII 13/16 Performances: state-of of-the-art R out [Ω] 1 2Ω Simulated Measured 2.5Ω 8.3Ω mΩ V DD +/- 2.5V Quiescence current 11 ma Port X,Z voltage swing +/- 1.5 V Port X,Z driving capacity +/- 2 ma Port Z DC impedance ~7.5 MΩ Port X offset voltage 2.7 mv Port Z offset current 2.25 µa -3dB AC transfer Y X ~11 MHz Summary of achieved performances.1 1 1k 3 1k 4 1k 5 1 1M 6 1M 7 1M 8 f [Hz] Recently published results on UVC [*]: terminal 1kHz 1MHz 1MHz z+ 2.1Ω 1Ω 89Ω z-.9ω 8.2Ω 76kΩ [*] Minarcik,M., Vrba,K. ICN'7

14 Motivation CCII- biquadratic section High-performance CCII 14/16 Experimental result: 1.5MHz LPF 5 th order LP filter (Butterworth) using new CCII biquadratic sections Characteristic of 1.5 MHz 5 th order LP filter

15 Motivation CCII- biquadratic section High-performance CCII 15/16 Test Facility

16 Motivation CCII- biquadratic section High-performance CCII 16/16 Thank you DTEEE - Brno University of Technology (Brno, Czech Republic) LGEP-Supéléc L2E UPMC (Paris, France)