Design Of Passive Intermodulation Reflected Test Instrument And Realization For GSM System

Reducing the power of passive intermodulation produced by the communication equipments will improve the sensitivity of the receiver and increase the capacity and stability of communication systems. The test of passive intermodulation is an important component in the work of reducing passive intermodulation products of communication systems. Based on the frequency bands of GSM system, this dissertation designs the passive intermodulation reflected test instrument,which meets all the demands of this issue. The essence of this issue can be concluded as follows.Firstly, this dissertation proposes the overall designing of intermodulation test system; describes the working principles; adopts S3C2440 and AD4350 as the main control chip and frequency synthesizer respectively; selects Embedded Windows CE 6.0 System as its application software development platform.Secondly, the detailed designs of the hardware are carried out. The first part is the main controller design, which includes the power module, interface module and network module. The second part is the carrier signals circuit design, which includes the frequency synthesizer circuit, the power attenuation circuit and the carrier detection circuit. The last part is spectrum analysis module design, which includes mixer circuit, IF amplifier and IF detector circuit.Thirdly, the software modules are designed, including LCD driver and intermodulation application software development. The application software is divided into hardware interface module, start module, parameter configuration module, database module, database module, and data processing and displaying module. The software design three test modules, including the fixed frequency test, the frequency sweep test and the time-domain test. The synchronous execution of the data processing, the interface displaying and the other related processes is ultimately realized.Finally, the experiments based on the reflected passive intermodulation test system for GSM are conducted. All the test data meet the system indicators of passive intermodulation with excellent steady-state performance and dynamic performance.