Key Techniques Of Shortwave Receiver Front-end Linearization

Electromagnetic interference is more serious, requiring higher receiver linearity. The absolute bandwidth of the shortwave is small, the interference is more serious. This paper studies shortwave receiver link budget and the linearity of the module.Analyzing Linearity and noise in the process of gain variation, and design the IF module program to achieve high linearity, low noise.Compare the characteristics of PIN switch and the FET switch. Select the FET switch, and analyze the reasons for the linearity worsening in short-wave band, improve linearity by increasing the bias resistor. The measured TOI of22pre-selection filters and digitally controlled attenuator is greater than30dBm and37dBm.For amplifier, balance and feed forward are the most effective linearization method. All of these two approaches were theoretically analyzed and simulated by ADS to compare the linearity of the amplifier using the linearization method or not. To use ATF531P8, combined with the balance and the feed-forward method, the output third-order and second-order intercept point were improved by lOdB, and36dB, and prove the linearization effect of the feed-forward and balanced method.The linearity of the Schottky diode and FET mixer principle, as well as the single-ended structure and double-balanced structure were studied. Selected resistive FET double-balanced structure, using FET array PE4140designed the mixer. Optimize the local oscillator port balun and RF-IF port balun through experiments. Conversion loss is less than6dB, input third-order intercept point is greater than32dBm with the LO drive power of19dBmAnalysis of the linear test problems that need attention, then design linear test components.