Sage-Tips

What is direct form realization?

In general, a direct form realization refers to a structure where the coefficients of the transfer function appear directly as Gain blocks. The direct form II realization method is presented as using the minimal number of delay elements, which is equal to n, the order of the transfer function denominator.

What is the reason for direct form II is called as canonical structure?

The direct form 2 implementation is called the canonical form, because it uses the minimal amount of delays, adders and multipliers, yielding in the same transfer function as the direct form 1 implementation.

What is realization in signal processing?

DIGITAL SIGNAL PROCESSING. Page 4. A realization is canonic if the realization uses minimum number of delay units. Two realizations are equivalent if they have the same transfer function.

What is a direct form structure?

The IIR Direct Form structures usually require few mathematical operations. However, the sensitivity to finite word length effects limits the use of this form in fixed-point implementations. Use the IIR Cascaded Second-Order Sections Form structures to alleviate finite word length effects.

What is direct form realization of FIR filter?

The FIR Direct Form Transposed structure is the alternate direct form implementation for FIR filters. However, in the FIR Direct Form structure, the word length of the delays equals that of the input signal x[n]. In the FIR Direct Form Transposed structure, the word length of the delays equals that of the accumulator.

What is the difference between direct form I and direct form II?

Direct Form I uses twice as many delay elements (even though these filters compute the same result) – it takes more memory to represent the state of the filter. Direct Form II uses less delay elements, but may be more like to cause arithmetic overflow in a fixed point implementation when v(n) is included.

What is the difference between direct form 1 and direct form 2?

Cascading direct form II sections results in N delay elements for filters of order N. Cascading direct form I sections results in N + 2 delay elements, since the delay elements of the input of any section (except the first section) are redundant with the delay elements of the output of the preceding section.

What is realization of digital filters?

Realization involves converting a given transfer function, H(z), into a suitable filter structure that is generally depicted using block or flow diagrams and shows the computational procedure for implementing the digital filter.

What is the main disadvantage of direct form Realisation?

8. What is the main disadvantage of direct form-I realization? The direct form realization is extremely sensitive to parameter quantization.

What is the difference between digital signal and discrete time signal?

A discrete time signal which is not quantized can take any value in the given range (i.e. infinite options for the amplitude) where as a digital signal can take any value from a predefined finite set of amplitudes. The digital signal can take any value out of these N values only ( and not just any value).

How many multipliers are required in direct form realization of FIR filter if the system order is n?

Explanation: From the direct form-I realization of the IIR filter, if M and N are the orders of numerator and denominator of rational system function respectively, then M+N+1 multiplications are required.

In very general terms, Direct Form I has advantages for fixed point implementations, and Direct Form II has advantages for floating point implementations. Both have stability problems for higher order filters. Both are equivalent for nonrecursive filters.

What is the advantage of transposed direct form II structure?

An advantage of the transposed direct-form II structure (depicted in Fig. 9.4) is that the zeros effectively precede the poles in series order. As mentioned above, in many digital filters design, the poles by themselves give a large gain at some frequencies, and the zeros often provide compensating attenuation.

What is the second order case of direct form II?

This new combined structure is called “direct form II” [ 60, p. 153-155]. The second-order case is shown in Fig. 9.2. It specifies exactly the same digital filter as shown in Fig. 9.1 in the case of infinite-precision numerical computations.

What is the difference between the DF-I and DF-II delay structures?

In other words, the DF-II structure, which is canonical with respect to delay, may require just as much or more memory as the DF-I structure, even though the DF-I uses twice as many addressable delay elements for the filter state memory. The remaining two direct forms are obtained by formally transposing direct-forms I and II [ 60, p. 155].