New Configurations for RF/Microwave Filters

Transcription

1 New Configurations for RF/Microwave Filters Presented by: Jeremy Fejfar Applications Engineer CST of America, Inc. 1 Sep-06

2 Outline Introduction Conventional Filter Theory Need for Folded Transmission Lines Single-level Folded line Bandstop and Lowpass Filters Multi-level Folded line Bandstop and Lowpass Filters Advantages of Folded Line Filters Conclusions 2 Sep-06

3 Introduction The explosive growth in miniature wireless communication hardware drives the need for miniaturization Increasing role of embedded passives Off-chip and On-chip applications Novel filter configurations desired Focus on Bandstop and Lowpass filters 3 Sep-06

4 Typical Receiver Architecture Antenna Mixer LNA LPF/ BSF QD A/D LO 4 Sep-06

5 Conventional Design Methodology: Limiting Factors < 1 GHz Typically Lumped Configurations > 10 GHz Typically Distributed Configurations Lower RF, microwave frequencies (1-10 GHz) Large component footprints Stub loaded filters extremely narrow or wide line widths impractical for physical implementation 5 Sep-06

6 Folded Filter Methodology Folding the transmission lines yields a more compact footprint Common design methodology for both bandstop and lowpass filters Conventional filter theory still applicable in the first phase of the design 6 Sep-06

7 Folded Line Examples Conventional stub loaded Conventional gap coupled Single-level folded line Single-level folded line Conventional gap coupled Multi-level folded line 7 Sep-06

8 Network Representation for Single Level Folded Line Filters 2N 2N port network [ Y ] Y Y A B = YB Y A [ Y ] [ M T ] [ coth( l )] [ Y ] [ M = γ ] 1 A v k diag k diag v [ Y ] [ M T ] [ csch( l )] [ Y ] [ M = γ ] 1 B v k diag k diag v [ Y ] [ M ] 1 [ Y ][ M ] k v SH v V 1 Sub N.W V 2N N-coupled transmission lines S 2Nx2N Sub N.W Sub N.W [ Y ] = [ G] + jω[ C] ;[ Z ] = [ R] + jω[ L] SH S Reduced 2-port scattering matrix 8 Sep-06

9 Folded Line Filter Section Sub-network Three-coupled transmission line 9 Sep-06

10 Filter Design Procedure Conventional stub loaded filter 10 Sep-06

11 Single Level Folded Line Bandstop Filters (Example #1) Initial design of stubloaded bandstop filter Specifications N=3, f 0 =1.5 GHz Maximally flat amplitude response (Butterworth) =0.2 & 0.3 Microstrip realization ε r =2.2, h=31mil Design equations for N=3 terminating impedances OC shunt stub impedances connecting line impedances prototype element values bandstop edge frequencies 11 Sep-06

12 Characteristic Impedances for Various Bandstop Filter Sections N=3, Maximally flat response, f 0 =1.5 GHz 50Ω microstrip line w = 98 mil 365.7Ω microstrip line w = 0.1 mil 258 Ω microstrip line w = 1 mil (1/2 ounce copper, 0.7 mil) 12 Sep-06

13 Design Flow for the Folded Line Bandstop Filters (Single-Level) Section 1 Section 2 Section 3 Section 1 Section 3 Section Sep-06

14 Bandstop Filter Comparison ( = 0.2) Conventional Folded Microstrip realization ε r =2.2, h=31mil Conventional stub-loaded filter measured 2948 sq mm Folded line filter measured 767 sq mm!! Please note the aspect ratio for conventional -> printing artifact ->line widths are too small to be shown accurately 14 Sep-06

15 Footprint & Critical Conductor Width Comparison =0.2 Conventional Bandstop Folded line Bandstop Smallest normalized width (w/h) (0.099 mil) 0.26 (8.06 mil) Overall footprint 2948 sq mm 767 sq mm Footprint comparison 100 % 26 % 15 Sep-06

16 Filter Response S 11 S 21 S 11 (Conventional filter theoretical) S 11 (Folded filter theoretical) S 11 (Folded filter MWS 2006 ) S 21 (Conventional filter theoretical) S 21 (Folded filter theoretical) S 21 (Folded filter MWS 2006 ) 16 Sep-06

17 Bandstop Filter Comparison ( = 0.3) Conventional Folded Microstrip realization ε r =2.2, h=31mil Conventional stub-loaded filter measured 2948 sq mm Folded line filter measured 1015 sq mm!! Please note the aspect ratio for conventional -> printing artifact ->line widths are too small to be shown accurately 17 Sep-06

18 Footprint & Critical Conductor Width Comparison =0.3 Conventional Bandstop Folded line Bandstop Smallest normalized width (w/h) (0.99 mil) 0.5 (15.5 mil) Overall footprint 2948 sq mm 1015 sq mm Footprint comparison 100 % 34 % 18 Sep-06

19 Fabricated Folded Line Bandstop Filter Microstrip Realization ε r =2.2, h=31 mil RT Duroid Sep-06

20 Folded Line Bandstop Filter Response S 11 S11 (db) S 21 Freq (GHz) S 11 (Folded filter theoretical) S 11 (Measurement) S 11 (Folded filter MWS 2006 ) 20 Sep-06

21 Folded Line Bandstop Filter Response (Cont d) S21 (db) Freq (GHz) S 21 (Folded filter theoretical) S 21 (Measurement) S 21 (Folded filter MWS 2006 ) 21 Sep-06

22 Folded Line Bandstop Filter Response (Cont d) Re-entry characteristics Re-entry characteristics similar to conventional filters but higher frequencies are shifted due to increased coupling Sep-06

23 Folded Line Bandstop Filter Response (Cont d) Re-entry characteristics Re-entry characteristics similar to conventional filters but higher frequencies are shifted due to increased coupling Sep-06

24 Single Level Folded Line Lowpass Filters (Example #2) Initial design of stubloaded lowpass filter Specifications N=3, f c =1.5 GHz Maximally flat response (Butterworth) Microstrip platform ε r =2.2, h=31mil Lumped-element prototype Richard s transformations Unit elements Kuroda s identities Impedance scaling Frequency scaling Z A and Z B = Z (j = 1 to n) = j Z (j = 2 to n) = 1j Terminating impedances = OC shunt stub impedances = Connecting line impedances 24 Sep-06

25 Characteristic Impedances for Various Lowpass Filter Sections Z A (Ω) Z 1 (Ω) Z 12 (Ω) Z 2 (Ω) Z 23 (Ω) Z 3 (Ω) Z B (Ω) N=3,Maximally flat response, f c =1.5 GHz 50Ω microstrip line w = 98 mil 25 Ω microstrip line w =243 mil (6.17 mm ) (1/2 ounce copper, 0.7 mil) 25 Sep-06

26 Design Flow for the Folded Line Lowpass Filters (Single-Level) Section 1 Section 2 Section 3 Section 1 Section 3 Section Sep-06

27 Lowpass Filter Comparison Conventional Folded Microstrip realization ε r =2.2, h=31mil Conventional stub-loaded filter measured 755 sq mm Folded line filter measured 535 sq mm!! 27 Sep-06

28 Footprint & Critical Conductor Width Comparison f c =1.5 GHz Conventional Lowpass Folded line Lowpass Largest normalized width (w/h) 7.9 (244.9 mil) 3.63 (112.5 mil) Overall footprint 755 sq mm 535 sq mm Footprint comparison 100 % 71 % 28 Sep-06

29 Fabricated Folded Line Lowpass Filter Microstrip Realization ε r =2.2, h=31 mil RT Duroid Sep-06

30 Folded Line Lowpass Filter Response S11 (db) Freq (GHz) S 11 (Folded filter theoretical) S 11 (Measurement) S 11 (Folded filter MWS 2006 ) 30 Sep-06

31 Folded Line Lowpass Filter Response (Cont d) S21 (db) Freq (GHz) S 11 (Folded filter theoretical) S 11 (Measurement) S 11 (Folded filter MWS 2006 ) 31 Sep-06

32 Multi Level Transmission Line Models Cross-sectional View Top metallization layer ε r =2.2 h=62 mil ε r =2.2 h=62 mil ε r =2.2 h=62 mil Via ε r =2.2 h=31 mil ε r =2.2 h=31 mil ε r =2.2 h=62 mil Bottom metallization layer Ground plane Ground planes hidden Stripline Realization Microstrip Realization 32 Sep-06

33 Importance of the Ground Plane (BTB Microstrip Realization) Isolates the top and bottom metallization layers More practical via dimensions Less prone to alignment errors 33 Sep-06

34 A Back-to-Back Microstrip Geometry Hole in ground plane Top metallization layer Through hole via 3D View Ground plane Bottom metallization layer 34 Sep-06

35 Network Representation for Multi Level Folded Line Filters V 1 Sub N.W N-coupled transmission lines S 2Nx2N N-through ground vias S 2Nx2N N-coupled transmission lines S 2Nx2N V 2N Top metallization layer Bottom metallization layer Sub N.W Sub N.W 2N x 2N port networks Cascade of three separate networks Reduced 2-port scattering matrix 35 Sep-06

36 Composite Geometry 3D View Overhead View 36 Sep-06

37 Via Model Extraction Hole in ground plane Through hole via R L Port 1 de-embed point Ground plane C C Port 2 de-embed point Closed form design equations L(w)= *exp( *w ) nh C(w)= *exp(0.2564*w ) pf R(w)= *exp(1.6083*w ) Ω Diameter of the via = ½ width of the strip Diameter of the antipad = 0.4 mm + diameter of the via 37 Sep-06

38 Via R, L, C Vs. Line Width L (nh), C (pf), R (ohms) C L R Line width w (mm) MWS 2006 Closed form equations 38 Sep-06

39 Design Procedure for Multilevel Bandstop and Lowpass Filters Conventional stub loaded filter Single level folded line filter 39 Sep-06

40 Multi Level Folded Line Bandstop Filters (Example #3) Initial design specifications of stub-loaded bandstop filter N=3, f 0 =1.5 GHz Maximally flat response (Butterworth) =0.3 BTB microstrip realization ε r =2.2, h=31mil for both dielectric layers 40 Sep-06

41 Bandstop Filter Comparison ( =0.3) Fold Line Single Layer Multi-Layer BTB microstrip platform ε r =2.2,h=31mil for both dielectric layers Conventional stub-loaded filter measured 2948 sq mm Folded line filter measured 532 sq mm!! 41 Sep-06

42 3D View of the Multilevel Folded Line Bandstop Filter Top metallization layer Bottom metallization layer Ground plane and dielectrics are hidden for better visibility 42 Sep-06

43 Footprint & Critical Conductor Width Comparison =0.3 Conventional Bandstop Single Level Folded Line Bandstop Multi Level Folded Line Bandstop Smallest normalized width (w/h) (0.99 mil) 0.5 (15.5 mil) 0.4 (12.4 mil) Overall footprint 2948 sq mm 1015 sq mm 532 sq mm Footprint comparison 100 % 34 % 18 % 43 Sep-06

44 Fabricated Folded Line Bandstop Filter Top metallization layer BTB Microstrip Realization ε r =2.2 h=31 mil ε r =2.2 h=31 mil RT Duroid 5880 Bottom metallization layer 44 Sep-06

45 Folded Line Bandstop Filter Response S11(dB) Freq (GHz) S 11 (Folded filter theoretical) S 11 (Measurement) S 11 (Folded filter MWS 2006 ) 45 Sep-06

46 Folded Line Bandstop Filter Response (Cont d) S21(dB) Freq (GHz) S 21 (Folded filter theoretical) S 21 (Measurement) S 21 (Folded filter MWS 2006 ) 46 Sep-06

47 Multi Level Folded Line Lowpass Filters (Example #4) Initial design specifications of stub-loaded lowpass filter N=3, f c =1.5 GHz Maximally flat response (Butterworth) BTB microstrip platform ε r =2.2, h=31mil for both dielectric layers 47 Sep-06

48 New Lowpass Filter Configuration Fold Line Single Layer Multi-Layer BTB microstrip realization ε r =2.2, h=31mil for both dielectric layers Conventional stub-loaded filter measured 755 sq mm Folded line filter measured 235 sq mm!! 48 Sep-06

49 3D View of the Multilevel Folded Line Lowpass Filter Top metallization layer Bottom metallization layer Ground plane and dielectrics are hidden for better visibility 49 Sep-06

50 Footprint & Critical Conductor Width Comparison f c =1.5 GHz Conventional Lowpass Single Level Folded Line Lowpass Multi Level Folded Line Lowpass Largest normalized width (w/h) 7.9 (244.9 mil) 3.63 (112.5 mil) 3.21 (99.5 mil) Overall footprint 755 sq mm 535 sq mm 235 sq mm Footprint comparison 100 % 71 % 31 % 50 Sep-06

51 Fabricated Folded Line Lowpass Filter Top metallization layer BTB Microstrip Realization ε r =2.2 h=31 mil ε r =2.2 h=31 mil RT Duroid 5880 Bottom metallization layer 51 Sep-06

52 Folded Line Lowpass Filter Response S11 (db) Freq (GHz) S 11 (Folded filter theoretical) S 11 (Measurement) S 11 (Folded filter MWS 2006 ) 52 Sep-06

53 Folded Line Lowpass Filter Response (Cont d) S21 (db) Freq (GHz) S 21 (Folded filter theoretical) S 21 (Measurement) S 21 (Folded filter MWS 2006 ) 53 Sep-06

54 Advantage Summary of Folded Topologies Uses a common design methodology for both bandstop and lowpass filters More compact footprints than conventional More feasible physical dimensions (i.e. aspect ratio) for a practical implementation Embedded ground plane aids in the design of multi level filters Equivalent electrical performance to that of the conventional filters Host of embedded passive and RFIC applications in the 1-10 GHz range 54 Sep-06