Research And Design Of S-band RF Transceiver Module For Airborne Communication

In order to adapt to the engineering application of the airborne radio frequency wireless communication system,the heterodyne s-band radio frequency transceiver module is widely used in this platform,which is characterized by small size,light weight,high integration and low power consumption.Secondly,the application of s-band transceiver module is mature and reliable.In this paper,the s-band heterodyne receiver and heterodyne transmitter are taken as the basic principle framework,add the frequency synthesis technology of phase-locked loop,designed and implemented miniaturized s-band transceiver module.The equipment studied in this article is mainly used for communication between the airborne and the ground.The receiving frequency coverage ranges from 2025MHz to 2120MHz,the transmission frequency coverage ranges from 2200MHz to 2300MHz,the channel bandwidth is 6.2MHz,the group delay fluctuation is less than 3ns,and the receiving dynamic range more than 70dB.The main work is design of overall scheme,select the device,link gain allocation,the design of local oscillator circuit and AGC circuit and system coordination.The main design difficulties are as follows:the dynamic range of the gain of the receiving channel is large.If a multi-stage numerically controlled attenuator and amplifier are used,it will pose a challenge to the miniaturization design.The small group delay fluctuations limit the range of filter selection.With a size of×60×20mm~3,there are many functional circuits that need to be implemented,the PCB layout and isolation requirements are relatively high;The transmit and receive channels use FDD frequency division duplexing.Power distribution and low-power design are also design difficulties.In this paper,in the design of receiving channel,in order to achieve a large dynamic range of the design of the receiving channel,a VGA amplifier is selected for implementation at the IF processing end.The advantages are low IF frequency and large gain.Using two stages can achieve a dynamic range of up to 90dB.By separating the cavity between the two-stage amplifier,the self-excitation of the AGC amplifier is effectively avoided.In order to achieve small group delay fluctuations in the channel band,the RF filter and the first IF filter use the one-piece dielectric filter,and the70MHz and 140MHz IF filters use the LC bandpass filter.Appropriately increase the bandwidth of the filter to reduce the group delay fluctuation within the 6.2MHz channel bandwidth.In the design of the whole power supply,a switching regulated power supply is selected to improve the overall use efficiency.At the same time,in order to avoid the impact of the switching frequency on the circuit,the output of the switching power supply is connected in series with a multi-line regulator.In the layout design of the PCB,the receiving channel and the transmitting channel are respectively arranged on two PCBs,and they are installed back-to-back.The power and control connection lines are implemented by pairing silver-plated copper wires.and the inner part of the channel is isolated by the way of integral partition.The final system test shows that the receiving dynamic range is as high as 85dB,and the in-band group delay fluctuation is less than2ns.All functional indicators and performance indicators meet the system requirements.