| The lives of the people have been covered by the digital TV business more broadly and deeply owing to the rapid development of the satellite digital set-top box industry.As the receiving front end of the set-top box,LNB is also advancing towards high performance and miniaturization on its own development path.Power management is the basis for the normal realization of the function of the entire LNB RF system,with the increasing upgrading of the system,the requirements continue to improve.Therefore,the research of LNB system power management technologies is of great significance.This paper focuses on three key technologies for specificity in power management of LNB system.The main content can be summarized as follows:1.Based on the charge pump,technologies related to the generation of negative power supplies is researched.The ripple characteristics and stability of the negative charge pump system under typical control technologies were studied,thus a high-stability low-ripple control scheme is proposed;the feedback circuit structure of the charge pump system is improved,and a high linearity error amplifier and low-offset bandgap reference are designed,through which the output accuracy and integration of the system are improved;the characteristics of the conventional clock generation circuit were studied,and an improved oscillator structure is proposed,which not only reduces the occupied area,but also improves the stability of the output frequency.Furthermore,the power consumption is reduced through the adjustable design of the oscillation amplitude.2.Technologies related to tone detection is researched.The bandwidth characteristics of the op amps under different compensation structures were studied,so that the-3d B bandwidth of the improved structure is extended by about 130 times,and an integrated band-pass filter circuit is designed;the characteristics of the traditional window comparator window construction technology were studied,two complementary improvement schemes of composite input type constant window formation and current control type window formation are proposed;based on the constant transconductance rail-to-rail amplifier,an open-loop comparator with a maximum transmission delay of less than 33 ns and a power supply current of only 75μA was designed.By replacing the external resistance with transistors,the hysteresis characteristic is achieved as well as the circuit area is optimized;based on the basic urn on and turn off process of power switch transistors,a driver with non-overlapping time output signal is designed.3.Technologies related to LNA DC bias is studied.Taking the DC bias of Ga As HEMT LNA transistor as an example,the characteristics of traditional bias technology were studied,and a highly reliable bias scheme is proposed.Combined with the negative power generation technology,the independence of gate and drain bias voltage supply is realized,and the best DC operating points of the biased transistors are ensured.It also has transient fault protection against overcurrent and negative power overload or short circuits.4.Based on the 0.18μm BCD process,the Cadence platform and Spectre tools were used to simulate and verify the application circuit of the researched technologies and the layout was drawn.The simulation results show that all indicators have reached the target requirements of the research and design. |
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