tailieunhanh - Digital Filters Part 5

Tham khảo tài liệu 'digital filters part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Common features of analog sampled-data and digital filters design 71 Direct description of SI cell can be applied in case of special program for idealized SI circuit analysis. Direct matrix representation of SI cell from Fig. 5 for switching in phase 1 and also in phase 2 has the following expressions in case of circuit switched in two phases. V Vc V11 V Ii1 gm 0 I1 0 z 1 2 gm Ii2 1 2 z gm 0 for 1 I12 0 gm for 2 14 where I12 Io2 for circuit switched in phase 1 and I1j 101 for circuit switched in phase 2. Now the currents are used instead of charges - it is a case of modified node voltages method applied for circuit switched in two phases. In our case the circuit contains only one nongrounded node. It means the matrix has only 2 X 2 dimension. The memory effect is here described by current source controlled by voltage in phase 1 and phase 2 with non zero transfer transconductance from one phase to the other as can be seen from the above mentioned matrix form. Presented procedure leads to the simple and easy description of SI structures and their effective analysis in both symbolic and numerical form. 4. Basic SI-biquad structures This part intends to discuss some aspects of the digital prototype approach in sampled-data biquads design. It is important to say that many applications of SI technique in sampled-data filter design published from the nineties are mostly based on a two-integrator structure in the case of biquads or operational simulation of LC-prototype - see . Toumazou et al. 1993 . But the principle of SI-circuit operation is rather similar to the digital ones so there arises possibility to use a digital prototype for SI-filter design. The first and second direct forms of the 2nd-order digital filter were chosen as the prototypes. Firstly the design using SI memory cells was considered in this case the final circuit should preserve the dominant features of the prototype. As a generalization of this approach the replacement of the memory cells in the .