Research And Design Of 100MHz Analog Baseband Chain For Wideband Wireless Communication Transmitter

In this thesis,A analog baseband is designed for wideband wireless communication transmitter.The analog baseband consists of three crucial parts,which are channel selection filter,programmable gain amplifier(PGA)and DC offset cancellation circuit(DCOC).Based on the structure of direct up conversion transmitter,design goals of the analog baseband and the three crucial parts are determined in this thesis,and the design of channel selection filter,PGA and DCOC is completed.The channel selection filter is designed with sixth-order Chebyshev Active-RC low-pass filter in which three Sallen-Key biquadratic cells are cascaded.The cut-off frequency of the filter is adjusted by capacitor banks.The Sallen-Key biquadratic cell is composed of two-stage fully-differential operational amplifier with two pair of inputs.One pair of inputs are used to constitute filter,and another pair of inputs are used to constitute unit gain negative feedback.The stability optimization technology is used in first-stage cascode load of operational amplifier to improve the stability condition when operational amplifier is closed loop.The programmable gain amplifier can be divided into attenuation stage and amplification stage.Attenuation stage is realized by the ? type resistance network,and amplification stage is based on adjustable source degeneration resistor PGA.Considering the tradeoff between linearity and gain in the traditional adjustable source degeneration resistor PGA,a transconductance enhanced technology is applied to PGA to improve gain and linearity.The low-pass negative-feedback DC-offset cancellation technology is used in this thesis.The low pass filter in negative feedback path is designed with first-order RC filter in which the large capacitance is achieved by Miller effect.The output stage of DCOC is composed of four transconductance amplifiers.Two transconductance amplifiers outflow current which flows on feedback resistors to produces a voltage on the resistors for DC-offset cancellation,and other two transconductance amplifiers inflow current.Considering the influence of the layout on the circuit performance,the flow chart and the basic principles of the layout design is discussed in this thesis,and the matching principles are analyzed emphatically.According to the above principles,the layout design of analog baseband circuit is completed.The analog baseband is implemented in TSMC 0.13?m CMOS process,and it is verified through post simulation.The post simulation results show that the power consumption of analog baseband is less than 22mW from a 1.2V supply voltage,the analog baseband can operate successfully at cutoff frequency of 100MHz,130MHz and 170MHz,and the proposed analog baseband obtains a-18dB to 30dB linear-in-decibel gain range with ldB gain step.From the post simulation results,we can conclude that the designed analog baseband works well in high frequency and provides sufficient gain control range,which can be implemented in wireless transmitter.