| In recent years,with the development of 5G communication technology,5G millimeter wave band has become the focus of future mobile communication construction with its advantages of high capacity,large bandwidth and low delay.Under the background of the gradual popularization of 5G communication,experiments,tests and researches of all kinds of 5G millimeter wave frequency bands are flourishing,and the test scenes are gradually complicated.Vector network analyzer(VNA)is the core measuring instrument for the research and development of millimeter wave devices and equipment.It plays an important role in the development of millimeter wave technology.Therefore,the development of 5G mm band vector network spread spectrum module not only realizes the low cost spread spectrum of the old vector network analyzer,but also increases the versatility and flexibility of the instrument,which has high economic value and engineering practical value.In this paper,the advantages and disadvantages of several kinds of traditional vector network analyzer spread spectrum schemes are analyzed at first.Based on these advantages and disadvantages,a dual-channel vector network analyzer spread spectrum scheme is used in this paper.The spread spectrum scheme realizes the measurement of all dual-port S parameters,so that the low-frequency vector network analyzer has the measurement capability of 5G mm band.Then the system planning and index allocation were carried out.The IF input of the spread spectrum module is 2.5～8GHz,and the IF signal is up-converted to RF(26.5～32GHz)through the mixer and filtering,and the RF signal reaches the device under test through two directional couplers and amplifiers.After being reflected by the device,the reflected signal is converted down the same link to the VNA input terminal.The local oscillator input signal is 12 GHz,and 13 d Bm input power is provided through the frequency multiplier to drive the mixer to work normally.Then,the passive and active components of spread spectrum components are developed and implemented,and the design idea of integration and miniaturization is adopted.The miniaturization of SIW directional couplers was developed by using the Substrate Integrated Waveguide(SIW)structure,compared with the physical dimensions of several couplers with different coupling degrees.According to the measured results of the coupler,the operating frequency band of the coupler is 26.5～32GHz,the through loss is better than 2.5d B,the typical value of the coupling is 6.7d B,and the directivity is better than 19.2d B.Considering the miniaturized structure of the filter,SIW double-layer crosscoupled structure is used to complete the design of SIW bandpass filter.The working frequency of the filter is 26.5～32GHz,and the actual transmission zero is 24.3GHz and32.2GHz.The insertion loss is better than 2d B,and the return loss is better than 10 d B.Then the low pass filter and power divider are developed.The hybrid integrated circuit of MMIC chip is used to realize active components such as mixers,amplifiers and frequency doublers in spread spectrum module.Finally,the integrated design of the active and passive devices is carried out,and the miniaturization design is completed through reasonable layout and processing measurement.Vector network analyzer and signal source are used to test the spread spectrum module.The test results show that the test results of most frequency points in26.5～32GHz are close to the real value,basically meet the requirements of spread spectrum. |
