Development Of S-band Wideband Tunable Receiver Front End

With the rapid development of the modern communication technique,the spectrum resources are increasingly limited.The tunable receiving system,as a technology that could help improve the utilization of spectrum resources,also has the ability to prevent interference with hostile signals,convert frequency or spread spectrum quickly to enhance the communication confidentiality in complex application environment such as electronic countermeasures and military communications.Besides,since the tunable receiving system has a variety of application scenarios,it has attracted extensive attention as well as become an important topic to carry research on in the communication field.In this thesis,the development of S-band wideband tunable receiving front-end is investigated,including the production and the test of the wideband preselected band-pass filters,wideband tunable filters and low noise amplifier components.The receiver frontend system indicators are analyzed and distributed.In addition,the difficulties and innovations of this designed system are described,namely the wide-band adjustment of the tunable filter and the harmonic suppression of the wideband preselected band-pass filter.In terms of the process designing wideband filters,a compact,multi-zero low-pass filter is proposed to suppress parasitic passbands and by cascading the step impedance resistance bandpass filter and the low-pass filter,a wide suppression broadband filter with an insertion loss less than 0.8 dB and good passband selectivity is produced,additionally,and the harmonic suppression range of which could reach 4 octaves.Then,the thesis briefly introduces the basic design theory of low noise amplifier followed by a detailed workflow of design with schematic diagram and layout simulation,produce,test and finally gets a low noise amplifier with operating frequency of 1.5GHz-4GHz,gain of 20.5dB and noise figure less than 1.6dB.Moreover,the thesis analyzes the structure of parallel coupled line loading varactor,which can be uesd to control the external quality factor creativly and solve the problem that the external quality factor is not controlled during the tuning process.On this basis,combined with the multi-mode resonant filter structure,two new broadband reconfigurable tunable filters are designed.One is a short-circuit parallel-coupled wideband tunable filter.The other is a cross-type parallel-coupled wideband tunable filter.Compared with other filters,the salient advantage of these two filters is that these two filters have wide tuning range and low insertion loss(<5dB),besides,they also have zero points outside the band.At last,the paper shows the result from the cascading test of the S-band wideband tunable receiving front-end system: it has an operating frequency from 1.8GHz to 3.65 GHz,a tuning range up to 66%,a noise figure less than 3dB,an 18.52 dB 1dB compression point and a 16.5±1dB gain with gain flatness.