Research And Implementation Of Millimeter Wave Portable Terminal Communication Device

Nowadays,on the premise of ensuring the reliability of the communication system,reducing the size and weight of the system and improving its portability are the mainstream development trends of portable communication systems,which has been a research hotspot for scholars.The electronic components in the millimeter-wave frequency band are small,thus conducive to the miniaturization of the system.Moreover,the research of millimeter-wave communication is of great significance for future wireless communications,and it is one of the most important development directions of wireless mobile communications.In this context,a portable terminal communication device for point-to-multipoint communication which operates across 38?40GHz frequencies is studied and realized herein.Firstly,the commonly used structure of transceivers are carefully compared and their advantages and disadvantages are discussed,among which the system adopts superheterdyne structure.So as to reduce the overall size and improve the portability of the system,the baseband and radio frequency modules are arranged on two PCB which are connected through Board-to-board connectors.Secondly,according to the design index of the system,the transmitting and receiving links of the system are simulated and the key module circuit is designed.A simplified millimeterwave frequency conversion structure without amplifiers and filters is designed.Compared with the classic millimeter-wave frequency conversion structure,the simplified structure involves fewer components,thus effectively reduces the power consumption and the size of system,therefore,improves the portability of the system.In order to suppress spurs generated by the system after the frequency conversion such as the image frequency and local oscillator leakage,a 38?40GHz integrated waveguide band pass filter is designed and fabricated.Then,a small omnidirectional antenna with omnidirectional radiation based on printed dipoles in the azimuth plane is designed and implemented.The measured results show that the return loss of the antenna is less than-16 d B from 38 to 40 GHz and the out-of-roundness of the radiation pattern of the azimuth plane at 38 GHz,39GHz and 40 GHz is about 3d B.Finally,the designed millimeter wave portable terminal communication machine is realized.The size is 80mm*64mm*24mmwith the total mass less than 600 g,ensures the portability of the system.A test of the system is carried out.The EVM of the transmission modulation of the BPSK signal with a symbol rate of 20 Msps is 12.62% at 38.54 GHz,and the adjacent channel rejection ratio is 29.7d Bc.The receiving test shows that the demodulation EVM of the BPSK signal with a symbol rate of 20 Msps is 14.75%,and the system receiving noise figure is 11.83 d B.Lastly,the phenomenon that appeared during the system test is analyzed and a reasonable explanation is given.The test results show that the designed portable communication system can meet the design requirements.