The Research Of A L-band Miniaturizd RF Front-end

No matter in civil fields or military fields,the wireless electronic communication system and radar system all have developed rapidly,of which,the L band RF receiver is used more and more.The RF receiver has the function of signal filter,amplitude magnify and up-conversion or down-conversion,as the function of the wireless electronic communication system and radar system is more and more,the performance is more and more strong,they need the receivers have more function and stronger performance,and as the development of semiconductor and micro-electronic technique and digital signal proceeding technique,the main technical index of receivers,as higher linearity,higher sensitivity,larger dynamic range and stronger anti-jamming capability are much and more stricter,and the RF engineers are always trying their best to realize miniaturization and low power consumption of receivers.Firstly,introduced some types of frequently-used receiver RF front end,such as:the superheterodyne receiver,the zero-IF receiver,the low IF receiver,the anti-image receiver and the digital IF receiver and so on,discussed their merits and demerits and the methods to improve them detailly,especially introduced the superheterodyne receiver RF front end,and then introduced the main technical parameters of the receiver RF front end;Then,based on the topological structure of superheterodyne receiver RF front end of twice conversion,combine with the characteristics of electronic device,the module's structure and the EMC principle,designed a L-band miniaturization of the receiver RF front end which has two receiving and emissive channels and with the function of up or down conversion,smoothing and amplification,of which,the receiving channel has the function of automatic gain control.Through debugging,the receiver RF front end has good technical index,miniaturized characteristic and low power;Then,introduced the function,type,theory and main technical parameter of automatic gain control(AGC)cell and logarithmic amplifier.Then based on chip AD8309,designed a logarithmic amplifier with four channels,through debugging and testing,the technical index is good.At last,discussed three methods of automatic gain control which based on two-stage AD8367 chip,three control methods are added on them which are control voltage outside the chip,demodulation voltage in the chip and demodulation voltage out of the chip,and designed a AGC brassboard test circuit on the PCB,and then obtained the corresponding test data and conclusion.