Field programmable analog arrays (FPAAs)

Full-custom analog design of integrated circuits is time-consuming and their verification expensive. Many attempts have been made to apply rapid-prototyping techniques known from the digital domain to analog designs. The goal of the presented work is to develop an FPAA, which is suitable for reconfigurable implementation of analog continuous-time (CT) high-frequency filters on an integrated circuit. This would enable designers to immediately verify the structure and coefficient selection of a filter in hardware and provide a working prototype. When being used as a verification tool for system-level designers, only a prototype would be implemented on the FPAA and deliver the proof-of-concept. The knowledge gained would then be used to accomplish an integrated design for mass-production. Moreover, the FPAA structure could be used as reconfigurable hardware platform in itself, to achieve a filter which is adaptable in the field to varying requirements or environmental conditions.

The FPAA structure consists of a two-dimensional array of CABs, which include digitally configurable transconductors (differential transconductance amplifiers). The arrangement in a hexagonal layout allows reconfigurable routing of analog signals throughout the chip. Series and parallel connection as well as feedback of any order is provided by the structure. Every CAB has six branches connecting to the respective neighbor CABs and one for self-feedback. The massive parallel connections of both parasitic input capacitances as well as parasitic output capacitances at the input nodes of each CAB sum up to capacitances in an order of magnitude such that they are suitable as integrating capacitances for the filter upto unity-gain bandwidths of 200 MHz.

Richard：可编程的模拟器件，这倒是个新奇的东西。今天偶尔看到了一些“Reconfigurable Analog Hardware”的研究，包括：FGMOS(Floating Gate CMOS Circuits)，FPAAs(Filed Programmable Analog Arrays)，GAs(Filter Synthesis by Genetic Algorithms)。没有详细了解，目前工业界做FPAA的有：Anadigm，Lattice Semiconductor，SIDSA，Zetex等。将入FPAA可以成功应用的话，那么，在模拟电路中，原型验证就非常简单了，但是，模拟电路和工艺有较大的关系，不像数字电路容易验证。FPAA其实想法挺简单，模拟学数字，但是我觉得恐怕实现起来很困难。不知道以后会不会有可编程的射频/微波阵列？呵呵。