In PSpice simulation in digital filter transmission line design

Designers using Pspice simulation is mainly for analog circuits.

However, it can also be simulated digital filter. A digital filter main part is the delay element, Adder and multipliers. Adder and multiplier can use operational amplifier, delay element can be used a transmission lines to simulation. The transmission line in PSpice is a forgotten for a long time, it can realize the delayed a few seconds.

　　

For example, Figure 1 shows a second order of digital filters.

The filter's transfer function is:

Of these, H (z) is a digital filter transfer function, and variable z is the z-transform, but Ai is the transfer function of the denominator of the coefficient polynomials, Bi is the transfer function coefficient polynomials of molecules.

Use the filter design software can get the values of these coefficients (bibliography 1). Sampling frequency fS and transmission delay is t = 1/fS. For example, a band-pass digital filter with 900Hz to 1kHz of 3dB passband, sampling frequency for Butterworth characteristics analysis 6kHz, can have following transfer function:

At this point, transmission delay to 1/6000 = 166.67ms.

If you set for the transmission of additional 1 Ω impedance of Z, the transmission lines of argument for Z0 = 1 Ω, and t = 166.67ms. Figure 2 is PSpice circuit. VCVS (voltage-controlled voltage source) E1 and E2 emulation voltage follower, and E3 and E4 and VCVS and their connected resistor is simulation Adder. Figure 3 is the simulation results.