## 4 Conclusions and Future Trends  
Silicon-based MMW ICs look more promising to fit the requirements of mixed signal and SoC applications. However, for the applications of ultra low noise and high output power, III-V based technologies are still more popular than the Si-based technologies. The future trend of the MMW ICs tends to fit more sophisticated and strictly specifications with multi-features in a single chip or a single circuit component like LNA, PA, mixer, VCO and so on. For the MMW LNAs will be low dc power, low supply voltage, high gain, high linearity as well as low NF. In MMW PA development, especially for modern communication systems, linearity and output power becomes more important due to the requirements for high quality communication. The output power has to be increased without sacrificing too much linearity performance. The future trend of the development of MMW mixers will equip both mixed-multi-features and outstanding performances among wide operation bandwidth, high isolations, CG, linearity, lower dc power consumptions and compact chip size. MMW VCOs nowadays have to fit low supply voltage, wide tuning range, large output power with good phase noise performance. As for other MMW control circuits, the main concept is to replace the passive components with active ones. In this manor, the area will be significantly reduced with moderate trade-off between their performances. In order to fit those strictly specifications and multi-features in MMW ICs, digitally assisted techniques are developed to solve the emergences. For the future MMW PA designs, digitally assisted techniques incorporate 3-dimensional power combing structures may be useful. The MMW mixer might be designed to be programmable to alleviate the number of mixer for different narrow-bandwidth standards in a MMW system or a time-consuming project cycle of MMW IC designs. Likewise, digitally assisted MMW circuit will be a hot research topic in this decade. This can be solved by the digital compensation techniques in the IF path [120] or LO path. Similarly, self-healing circuits, which can detect, isolate, and repair their own faults produced by the process variations, incorporate with the MMW mixers will possibly become popular [219]. With the evolution of the communication systems, multi-features with digital control mechanism in a MMW VCO are essential. Except for the varactors, inductors or even transformers in a MMW VCO become tunable and thus, wide frequency tuning range and multi-band operation can be achieved without lowering the operation frequencies [172]. As for current MMW transceivers, it is possible to integrate the antenna, a medium-power amplifier, a transceiver, a frequency synthesizer, and baseband circuits into a single chip. Also, high-efficiency antenna is still needs to develop while implementing the transceiver in silicon based technologies. Thus, flip-chip design with LTCC will be essential for high performance antennas, multi-chip modules and the MMW ICs of high power dissipations in order to lower the temperature of the device junctions. Also, three-dimensional MMW ICs will worth further developments to achieve higher level of integrations particularly in SiGe and will find a various applications in MMW regime. To the author's best knowledge, some silicon-based MMICs emerge in the past few years, for instance, high performance 60 GHz wireless chipsets are available from Silicon Image for the application of a wireless, high-definition video and audio connection, with near-zero latency for wired-quality performance and reliability. These chipsets feature embedded on-chip antennae and proprietary beam-forming algorithms on the low-cost CMOS processes. In most challenging environments, these 60 GHz wirelessHD products still provide a robust wireless connection to support cable-like video connections [220]. Finally, the temperature-compensation for Si-based technologies might be an emerging issue, which needs to be solved.