An Efficient Single-Layer Crossing Based 4-Bit Shift Register Using QCA
In co-planar QCA fabrication, QCA wire crossing is a challenging task as defects appear to be inherent due to two cell types in single layout structure. In this paper, a compact 2:1 multiplexer is presented which occupies a minimum area in QCA technology.
- PDF / 855,378 Bytes
- 11 Pages / 439.37 x 666.142 pts Page_size
- 88 Downloads / 210 Views
Abstract In co-planar QCA fabrication, QCA wire crossing is a challenging task as defects appear to be inherent due to two cell types in single layout structure. In this paper, a compact 2:1 multiplexer is presented which occupies a minimum area in QCA technology. This work also showcases a successful implementation and simulation of 4:1 multiplexer, level trigger D flip-flop and 4-bit shift register using QCADesigner tool. The 4:1 multiplexer and shift register are more robust and enjoy single-layer wire crossing, which requires only one type of cells. The comparison results show superiority of the proposed designs over the previous designs in terms of complexity and delay. Keywords QCA
Shift register Multiplexer D flip-flop
1 Introduction Quantum dot cellular automata (QCA) based devices are going to replace CMOS based devices for its potential improvements. Various QCA-based structures are explored in [1–8]. QCA architectures for flip-flops and multiplexers have been presented in [9–15] as these are essential blocks of various digital systems. But most structures are not robust and vulnerable to fabrication defects due to wire crossing between the QCA components. This work presents, a robust 4-bit shift registers using optimal multiplexer and D flip-flop modules. T.N. Sasamal (&) U. Ghanekar Department of Electronics & Communication, NIT Kurukshetra, Kurukshetra, India e-mail: [email protected] U. Ghanekar e-mail: [email protected] A.K. Singh Department of Computer Applications, NIT Kurukshetra, Kurukshetra, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2018 R.K. Choudhary et al. (eds.), Advanced Computing and Communication Technologies, Advances in Intelligent Systems and Computing 562, https://doi.org/10.1007/978-981-10-4603-2_30
315
316
T.N. Sasamal et al.
The paper is organized as follows. Section 2 presents a review on QCA. In Sect. 3, optimal design and detailed analysis of basic structures, such as multiplexer and D flip-flop are given, followed by implementation of an efficient 4-bit shift register in Sect. 4. Simulated results and comparative analysis are addressed in Sect. 5. Finally, conclusions are given in Sect. 6.
2 Preliminaries 2.1
QCA Cell and Gates
A QCA cell is a quantum well, which has four quantum dots located at four corners of a square. Two injected electrons are free to occupy any of the four dots based on Coulomb repulsion among them. These two electrons position at the two corners due to repulsion and yield two possible polarizations as shown in Fig. 1. By applying proper clocks, electrons are able to tunnel through the inter dot barrier by electrons interaction. Any digital circuits can be made of a combination single QCA cell. In QCA circuits, majority gates and inverters are the basic building blocks. Two possible implementations for an inverter are shown in Fig. 1c, d. QCA layout of a 3-input majority gate is depicted in Fig. 1e. A 3-input majority gate can be represented as MV(a, b, c) = ab + bc + ca. By fixing one of the inputs t
Data Loading...
