As we have seen, designing L-C lowpass filters from the lowpass prototype involves only scaling of the resistance and cutoff frequency of the prototype by simple multiplication and division. The transfer characteristics of the prototype are exactly retained and no special realization difficulties are introduced. The design of other structures, such as highpass, bandpass and bandstop filters, require transformation in addition to the scaling. These transformations naturally modify the attributes of the prototype and may introduce severe realization difficulties, especially for bandpass and bandstop structures. The 'ideal' transformation does not exist, and it becomes necessary to consider alternative transformations and how they relate to specific filter requirements and applications. This chapter considers a number of network transformations and equivalences.

Chapter Contents:

• 4.1 Highpass Transformation
• 4.2 Conventional Bandpass Transformation
• 4.3 Bandstop Transformation
• 4.4 Narrowband Bandpass Transformations
• 4.5 Top-C Coupled, Parallel Resonator
• 4.6 Top-L Coupled, Parallel Resonator
• 4.7 Shunt-C Coupled, Series Resonator
• 4.8 Tubular Structure
• 4.9 Elliptic Bandpass Transforms
• 4.10 Conventional Elliptic Bandpass
• 4.11 Zig-Zag (Minimum Inductor) Elliptic BP
• 4.12 Bandpass Transform Distortion
• 4.13 Arithmetic Transformation
• 4.14 Blinchikoff Flat-Delay Bandpass
• 4.15 Pi/Tee Exact Equivalent Networks
• 4.16 Exact Dipole Equivalent Networks
• 4.17 Norton Transforms
• 4.18 Identical-Inductor Zig-Zag
• 4.19 Approximate Equivalent Networks
• 4.20 Impedance and Admittance Inverters
• 4.21 Richard's Transform
• 4.22 Kuroda Identities
• 4.23 Prototype k and q Values
• 4.24 References

Inspec keywords: band-pass filters; electric resistance; band-stop filters; low-pass filters

Other keywords: L-C lowpass filter; bandpass filter; lowpass prototype; transfer characteristics; cutoff frequency; highpass filter; network transformation; multiplication; filter requirement; division; bandstop filter; bandpass structure; filter design; bandstop structure; resistance

Subjects: Filters and other networks