A Multi-Frequency Band Design And Implementation Of Loop Control Circuit

Communication takes voice,image and data as media to transmit information to the other party through optical or electric signals.With the progress and development of science and technology,communication is more and more integrated into our work and life.In order to ensure the stability and reliability of communication quality,we usually use the loop control circuit to realize the power control of power amplifier.However,the loop control circuit in domestic transmitting units has such characteristics as narrow working frequency range,narrow RF AGC range,large loss of receiving channel,low isolation between transceiver channels and slow transceiver switching time.In this paper,based on the above deficiencies,a multi-frequency loop control circuit is designed,which can solve the above problems and disadvantages.The total charge of the intrinsic layer of the PIN diode is mainly generated by bias current.When working in the RF band,the PIN diode will present a linear resistance,which is determined by the DC bias.The resistance value in forward bias is very small,close to short circuit.Reverse bias has a high resistance,close to open circuit.The quality factor Q is the ratio of inductive XL to its equivalent resistance.The higher the Q value of the coil,the smaller the loss of the loop.Based on the theoretical basis,this paper designs the RF AGC circuit and SPDT switch circuit,and through related experimental studies and analysis of experimental results,obtaines the connection between the on resistance R_S,junction capacitance C?and Q value and the insertion loss of the receiving channel and the isolation degree of the transceiver channel.In this paper,based on the above theoretical research and experimental results analysis,according to the function and the control circuit to achieve multiband loop index requirements,adopts the modular design thinking,it can be divided into the power supply circuit,control circuit,detection control circuit,VHF,UHF power control loop,RF AGC circuit,eight parts such as SPDT switch circuit and interface circuit design.Then according to the requirements of reliability,environmental adaptability and electromagnetic compatibility,PCB layout,wiring,welding process of components,anti-vibration and impact design.The multi-band loop control circuit designed in this paper has realized the power control and power drop protection functions of the power amplifier.After the performance tests at room temperature,low temperature and high temperature,the functions and indicators meet the requirements of"HKPA150160800 power amplifier specification",and makes full preparations for the next step of the whole machine joint test with customers.