Research On Automatic Gain Control And Power Control For CMOS Broadband Configurable Rf Transceiver

The trend of wireless communication applications to multi-mode compatibility raises new challenges to RF transceiver chip technology.Compared to dedicated narrowband RF transceiver chip,that with the versatility of broadband undoubtedly has a higher technical difficulty,as it requires system parameters such as work frequency,bandwidth,dynamic range,transmitting signal power,and modulation precision,can be flexibly configured on a wide range.In this paper,we study the CMOS broadband RF transceiver chip with frequency coverage from 70 MHz to 6 GHz,and signal bandwidth coverage from 200 kHz to 56 MHz,and it covers almost all communication protocols within the scope of the spectrum.It is a radio frequency transceiver chip with high performance,high integration and perfect agility.In this paper,we mainly research the technology of automatic gain control of receiver path and power control of transmitter path in the chip,which is key technology to transceiving performance.The automatic gain control technique is used to enlarge input dynamic range,stable output signal power,and reduce the dynamic range of latter circuit.In this paper,we start with system architecture and performance,calculate the system parameters closely related to the automatic gain control.After that,this paper puts forward an approximation method based on logarithmic space,collaborating with a lookup table.The novel method can change the gain of multiple modules at one time,and overcomes the drawbacks existing in traditional digital automatic gain control algorithm such as complex calculation process,small dynamic range,slow reaction,etc.In addition,the paper puts forward a configurable digital AGC algorithm which can meet different requirements for convergence time and output signal power range under different communication protocols.Utilizing the system parameters calculated ahead,the receiver model can be built with MATLAB/Simulink,and the proposed automatic gain control method is simulated.The results show that this kind of gain control method can effectively converge input signals of different power to a specified range.The gain control dynamic range is as large as 74 dB with minimum step of 1dB and maximum step of 18 dB.According to different parameters and the selection of control mode,convergence time spans from 36.063 us to 1.914 ms,and convergence error to reference power is less than 1.24 dB.The transmitting power control circuit is used to stabilize the signal power of the transmitter to a certain value,decease interference to adjacent channels result from too large signal power and decreasement of demodulation precision.In order to overcome the disadvantages of traditional power control,this paper proposes a more accurate digital power control method based on multiplexing receiver path while it doesn't work.The simulation results show that this new power control method has delay of 2us,dynamic range of 90 dB,and resolution of 0.25 dB.In addition,the proposed method achieves transmit power control with a digital method,and has advantages of simplification of the circuit design process,improvement of accuracy,reduction of circuit area,and larger working frequency range compared to analogy method.It has strong engineering practicability.