| Summary: | 碩士 === 國立中正大學 === 電機工程研究所 === 107 === The main purpose of this thesis is to design an automatic gain control circuit (AGC), and to integrate it into the system of transmitter for S-band. In view of the output signal of this system which is needed to up convert from BF to RF, the super heterodyne framework is a useful way to achieve it. That is because using one mixer to direct up conversion would cause some problems in this system, such as lacking in its gain or output power. Moreover, the characteristic of elements in the system might be worsen due to frequency response. Therefore, this AGC is manufactured in 700 MHz which is IF of this system.
In addition to stabilizing and adjusting output power, this AGC also allows to be controlled by external circuits, such as ADC and switch. By them, it is able to change function between revising output power and locking gain which is memorized by ADC at any time.
All circuits in this thesis are made in TSMC CMOS 0.18 um process. And the chip size without pads is 247.06×132.20 um2, the size of external control circuit ADC is 483.46×329.94 um2. According to the specification required and simulation results, the dymanic input power range is from -16 dBm to -10 dBm, the output power range is from -16 dBm to 4 dBm (20 dB), and the gain control range is 30 dB. Furthermore, the settle time of this AGC loop is less than 0.2 us, and it would increase 0.15 us to stabilize if using ADC and switch to control. Finally, the total chip is under 3.3 V power supply and 7.38 mA current flow, which means total power consumption is 24.35mW.
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