Used In Research And Design Of Broadband Systems, Reconfigurable Analog Baseband Circuit

With the development of wireless communication system, RF integrated circuit put a higher and higher requirement on the analog baseband circuit. On the one hand, since the bandwith of analog baseband partially determines the velocity of signal transmission in a RF system, it should meet the bandwith requirement; on the other hand, the wide band analog baseband circuit should reach the performance in the large range of bandwith which is much tougher than the case of its narrow bandwith counterpart. Compared to narrow ones, the circuit designers have to make more efforts to achieve the same noise or linearity performance simply because of the degradation of circuit transmission characteristic such as loopgain and of different structure that should be used when the circuit is working in a high frequency range. All the above discussion shows a greater challenge in the wide band analog baseband circuit design.Since the analog baseband circuit is generall composed of a low pass filter (LPF) and a variable gain amplifier (VGA), this thesis starts from unit cell circuit. It analyze several LPF architectures which is suitable for wide band application and concludes the advantages and disadvantages among them and finally confirm the optimized realization. In order to make the circuit insensitive to process and temperature parameters, the self adjust calibration circuit is embedded. The two kinds of calibration circuit (analog and digital) are analyzed and a digital calibration circuit is design and simulated for the wide band LPF application. When it comes to VGA, despite the realization, the thesis also puts forward a method to prominently optimize the linearity when the continuous adjusting VGA is in its low gain condition.Whereafter the thesis analyze the realization of analog baseband circuit in RF transmitter and receiver from a systematic perspective which include the confirmation of systematic performance target (taking ultra wide band as an example), choice of architectures, simulating the model of LPF. In the RF transmitter and receiver, the LPF adopts the chebychev approximation and the OTA-C architecture for the consideration of out band attenuation, power consumption and high frequency applications. In the RF receiver, the VGA makes use of linearity boosting source degeration architecture to achieve the performance target of the chain in the RF receiver. The LPF absorbs the frequency tuning fuction to be reconfigurable between Wimedia and Chinese Standards.Moreover, the thesis also discuss the design method of some assistant circuits include the common mode stability circuit in Nauta architecture, the influence the dc offset cancellation and common mode feedback have on the VGA gains, the linearity issues in the biquad architecture. In addition to the design method,optimized realizations are also proposed.