Research And Implementation Of Frequency Converter For Broadband Ad-hoc Network

Microwave and millimeter wave plays an important role in the information transmission of modern science and technology society.At the same time,the ad-hoc network communication system is gradually emerging.Each terminal in ad-hoc network has two functions of host and router,which can realize the networking and convenience of information transmission.Because the signal needs to be processed in baseband and transmitted in higher frequency,there is the problem of up and down conversion.The transceiver system is one of the important links of information transmission.Based on this,this paper develops a Ku band time division duplex up and down conversion transceiver channel,which can mix the low-frequency signal to the higher frequency band for transmission,at the same time,it can receive the high-frequency signal to the lower frequency band for processing.The following work is carried out for the frequency conversion transceiver system.First of all,the target of the project is to up-convert 1GHz signal of-20 d Bm to 14GHz～16GHz of 20 d Bm for transmission.At the same time,it can receive RF signal in Ku band of-5d Bm and down-convert it to 1GHz.After analysis,the link scheme of two frequency conversion is determined.The 1GHz signal is first converted to 4GHz,and then mixed with the local oscillator signal of 10 GHz ～ 12 GHz to 14 GHz ～ 16 GHz.The project uses the SPDT Switch to complete the up and down selection switch.Then,the filter needed in the project is designed and simulated.In this paper,four filters are designed,which are 4GHz sector low-pass filter,4GHz interdigital band-pass filter,14GHz～16GHz interdigital band-pass filter and 14GHz～16GHz Substrate Integrated Waveguide(SIW)filter,respectively.In this project,the fast design wizard function of wasp-net is used to complete the design process of the SIW filter,which improves the design efficiency.The test results of 14GHz～16GHz SIW filter meet the design requirements.Finally,the details of the up and down conversion transceiver link budget are designed and simulated.The details are adjusted until the link budget results meet the requirements of the subject.The specific block diagram of the system is determined and the converter is fabricated.The software consists the PC side program and firmware of microcontroller unit,and then the physical measurement is carried out.The measurement result shows that in the up conversion link,the output power is above 19.2d Bm in the frequency range of14GHz～16GHz,the flatness is 3d B,and the output third-order intermodulation intercept point is about 30 d Bm.When the output frequency is 15 GHz,the phase noise is-86.12 d Bc /Hz@10KHz.The test results of down conversion link shows that the output power is above-9.7d Bm with the input frequency range is 14GHz～16GHz of-5d Bm.The flatness is 2.8d B,and the output third-order intermodulation intercept point is about 8d Bm.When the output frequency is 1GHz,the phase noise is-92.5 d Bc/Hz@10KHz with the input frequency is15 GHz.The mirror frequency rejection of 6GHz～8GHz with the input power is-5d Bm is about 88 d Bc.Within the allowable error range of the experimental environment,the test results of the up and down conversion system meet the design requirements and it is suitable for engineering realization.