The Development Of Broadband Amplification Link With Amplitude Equalization

With the rapid development of radar technology, the constant emerging of new radar system, and the in-depth application of advanced technology in radar development, the radar reconnaissance environment is becoming more and more complex. In order to adapt to the complex electromagnetic reconnaissance environment, the reconnaissance receiver is expected to cover the entire range of electronic warfare frequency domain to capture different types of radar signals. Thus, it is an inevitable trend to develop a wideband, anti-interference ability radar reconnaissance in the electronic information warfare. As the core module of wideband radar reconnaissance, broadband amplification link with amplitude equalization, which restricts the overall performance level of wideband radar reconnaissance plays a decisive role in electronic information warfare. The core components of the link contain broadband low-noise amplifier and wideband filter, in detail, broadband low-noise amplifier determines the overall system’s noise figure, sensitivity as well as dynamic range, and the wideband filter is able to improve the system’s anti-jamming capability.Based on the research about the prototype structure of the series and parallel negative feedback, this paper improved the amplifier’s gain flatness, input and output VSWR and stability, for the microstrip line’s length on the series negative feedback was revised and the inductor on the parallel negative feedback loop was replaced with the high impedance line. With the traditional T and π-type matching circuit abandoned and broadband matching analytical theory taken, a novel low-Q microstrip cross-matched circuit was put forward to expand the matching bandwidth of amplifier. Meanwhile, a π-type amplitude equalizer network by using the resistor in series with the inductor to the ground was adopted to improve the low-noise amplifier’s output gain flatness. At last, through research and study, that broadband equalization low noise amplifier’s physical size was 36mm×32mm×15mm, and the gain, noise figure, return loss as well as output power 1dB compression point was 21 ± 0.5dB, lower than 1.85 dB, better than 9dB, as well as greater than 10 dBm, on the condition that this amplifer’s frequency was between 1.5GHz-5.5GHz.This paper accomplished the wideband multi-mode filter using the structure of interdigital coupled line feed multimode resonator. On the basis of the conventional circuit structure, the defected ground structure(DGS) and the shorted stub were embedded to change the electromagnetic distribution of the interdigital coupled lines, therefore enhanced the coupling strength of the interdigital coupled lines and broadened the bandwidth of the filter. Meanwhile, the structures of circuit such as the stepped impedance resonator(SIR) and the folded open stepped impedance resonator(SIS) were loaded to introduce the transmission zero, thus improving the filter’s sideband roll-off characteristics. At last, through research and study, that wideband 7 mode filter with interdigital coupled line loading shorted stub’s circuit size was 43.6mm×9.8mm, and the insertion loss, return loss, as well as band rejection was less than 2.5dB, better than 15 dB, as well as greater than 45 dB, on the condition that this filter’s frequency was between 1.2GHz-5.15GHz(expected design passband was 1.5GHz-5.5GHz, and the measure passband of filter offset toward low frequency).Amplitude equalizer broadband amplification link basically achieved the desired target though the final study, whose gain within passband, band rejection and the input and output VSWR was 20 ± 1dB, greater than 45 dB and less than 2.