Functional circuits are a group of combinational logic circuits which may be utilized for certain tasks and with specific planning. Decoders, multiplexers, and demultiplexers are all functional circuits that come in useful when creating complex systems. Quantum-dot cellular automata (QCA) is a flourishing technology that would be so practical in the field of computational digital circuits in terms of its advantages such as low energy consumption. This paper proposes various quaternary 1:4 decoders (enabling decoder, active-high and active-low decoders). Then, 4:1 multiplexer and 1:4 demultiplexer were architectured using the proposed 1:4 decoder. In the following, a quaternary to the binary converter (a 4-valued digit to a 2-bits circuit) is designed regarding the validated proposed structures. All designs were simulated and verified by QCASim. The total area used for the decoder, multiplexer, demultiplexer, and quaternary to the binary converter are 0.01, 0.19, 0.03, 0.13 μm². The complexity and delay are 30, 387, 88, 214 and 0.5, 3.25, 1, 2 respectively. This work gets compared to CMOS and carbon nanotube field-effect transistor articles. Furthermore, the proposed 4:1 quaternary QCA multiplexer got compared with the binary QCA multiplexers. The comparison results show that our proposed designs are efficient in terms of having a low delay, area, and complexity.

功能电路是一组组合逻辑电路，可用于某些任务并经过特定规划。解码器、多路复用器和解多路复用器都是在创建复杂系统时有用的功能电路。量子点元胞自动机（QCA）是一项蓬勃发展的技术，由于其低能耗等优点，在计算数字电路领域将非常实用。本文提出了各种四进制 1:4 解码器（使能解码器、高电平有效和低电平有效解码器）。然后，使用所提出的 1:4 解码器构建 4:1 复用器和 1:4 解复用器。下面，根据经过验证的建议结构设计了四进制到二进制转换器（4 值数字到 2 位电路）。所有设计均由 QCASim 进行仿真和验证。用于解码器、复用器、解复用器和四进制到二进制转换器的总面积为0.01、0.19、0.03、0.13μm ²。复杂度和延迟分别为30、387、88、214和0.5、3.25、1、2。这项工作与 CMOS 和碳纳米管场效应晶体管文章进行了比较。此外，还将所提出的 4:1 四进制 QCA 多路复用器与二进制 QCA 多路复用器进行了比较。比较结果表明，我们提出的设计在低延迟、低面积和低复杂性方面是有效的。