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Stability criterion for a class of fixed-point digital filters using two’s
complement arithmetic
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Tao Shen
⇑
, Zhugang Yuan
School of Control Science and Engineering, University of Jinan, Jinan 250022, China
article info
Keywords:
Stability
Digital filters
Nonlinear systems
Finite word length effect
abstract
A new stability criterion for a class of digital filters using two’s complement arithmetic is
presented. The effectiveness of the obtained results is shown by using a numerical
example.
Ó 2012 Elsevier Inc. All rights reserved.
1. Introduction
The word length reductions have the effect of inserting nonlinearities (quantization and overflow nonlinearities) [1–3].
The nonlinearities may lead to instability. The limit cycle phenomenon, which is a characteristic of nonlinear systems
may possibly occur in the system if the system parameters are not chosen properly [4]. Hence, various models of digital fil-
ters have been considered in the literature. The stability of such filters when the overflow arithmetic is of the saturation type
(saturation nonlinearity) has been investigated extensively [4–13]. These include a class of digital filters involving single
nonlinearity [4–8] and a class of state-space digital filters involving multiple nonlinearities [2,9–13]. It is well known that
the hardware implementation of saturation arithmetic adder is more expensive than that of two’s complement arithmetic
adder [14]. So, it is worth investigating the stability of digital filters using two’s complement arithmetic. Some results about
this topic have been proposed in [15–19]. In this paper, a class of digital filters involving single overflow nonlinearity, imple-
mented with fixed-point arithmetic, is considered. The system is given by
GðzÞ¼h
1
z
n
þ h
2
z
ðn1Þ
þþh
n
z
1
yðrÞ¼output of GðzÞ
f ðyðrÞÞ ¼ input of GðzÞ
9
>
=
>
;
: ð1Þ
The nonlinearity characterized by
f ðyðrÞÞ ¼ yðrÞ ; if jyðrÞj 6 1
jf ðyðrÞÞj 6 1; if jyðrÞj > 1
ð2Þ
is under consideration. It is assumed that the effects of quantization are negligible. Eq. (2) includes, among others, two’s
complement overflow arithmetic [1–3].
A state-space representation of the system (1) and (2) can be obtained by setting x
i
ðrÞ¼f ðyðr þ i 1ÞÞ; i ¼ 1; ...; n, which
yields
0096-3003/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/j.amc.2012.10.064
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This work was partially supported by the National Natural Science Foundation of China under Grant No. 61102113 and the Natural Science Foundation
of Shandong Province, China under Grant No. ZR2010FL017. The material in this paper was not presented at any conference.
⇑
Corresponding author.
E-mail address: shentao28@163.com (T. Shen).
Applied Mathematics and Computation 219 (2013) 4880–4883
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Applied Mathematics and Computation
journal homepage: www.elsevier.com/locate/amc