| Summary: | 碩士 === 長庚大學 === 電子工程研究所 === 95 === Broadband systems have traditionally employed TWDA, as they have been extensively investigated and firmly established as being reliable and robust devices that can be realized in MIC and MMIC technologies. This device has become very popular due to its excellent bandwidth performance. This is possible because the input and output capacitances of the active devices are absorbed in the distributed structures The resulting amplifier also exhibits very low sensitivities in process variations when realized in MMIC technology and is relatively easy to design and simulate.
The gain performance of a single-stage traveling wave amplifier comprising of two MESFET devices is limited to 8 to 9 dB. This is due to the gate and drain line attenuation that limits the number of FET devices in a distributed amplifier configuration. In other words, there are a certain number of devices that maximizes the gain per FET used. The limitation on the number of devices at high frequencies is mainly due to the attenuation on the gate line. The attenuation on the lines also reduces the bandwidth with an increase in the number of FETs.
The interest in microwave techniques for communication systems has grown immensely over recent years, and the performance of microwave active and passive circuits for wireless systems technology has become extremely advanced. One of the most critical active circuits employed in systems applications is the microwave amplifier. Because it is a highly versatile circuit function, it has always been the first to benefit from developments in the device and semiconductor technologies. Amplifiers with extremely wide bandwidths with good performance have been successfully realized in the past 2 decades in hybrid and monolithic technologies hence, the subject of amplifiers has been firmly established in the fields of microwave, optical communication, instrumentation, and EW.
Broadband amplifiers find many applications such as instrumentation, electronic warfare and broadband optical communication. Distributed amplifiers (DAs) were widely used for realizing broadband amplifiers in GaAs hybrid and MMIC technologies [l-4]. Recently, DAs in CMOS process were also reported because of the advantages of low cost and integration ability with base band circuits [5-10]. The improvement in efficiency demands is primarily driven by the next generation of multioctave systems, such as high-data-rate fiber-optic links and EW.
In this paper, a 3~24 GHz distributed amplifier was designed by three-stages architecture and fabricated by using TSMC 0.18um 1P6M CMOS standard process.
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