A Low Noise and Broadband LNA Used Series and Parallel Feedback for Ku-Band Application
vi, 50 p.
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The broadband LNA (Low Noise Amplifier) is designed and fabricated for ku-band application. The LNA of high frequency demanded for high gain and low noise figure. Because high frequency signals entered into directly the input of LNA and the impedance of LNA input was treated seriously. The impedance of LNA input influences on noise figure, oscillation, and return loss. An active device is used HEMT (High Electron Mobility Transistor) that it has a low noise figure and good performance in high frequency. Bias structure used the double bias type of negative voltage in gate part and positive voltage in drain part. Designed LNA is implemented on teflon the substrate of a dielectric constant of 2.52, the conductor thickness of 0.018 mm and the substrate height of 0.54 mm. For design specifications, series and parallels feedback methods were used that it was obtained improved result better than specifications. Then fabricated LNA was connected with matching circuit in cascade form. Fabricated LNA has noise 0.8 dB, the gain of 22.5 dB, the input and out return loss of 13.2 dB, 19.6 dB, the flatness and broadband of ±0.5 dB at the desired frequency range (11.2~12.7 GHz) and the output power of 13.5 dBm at 1 dB gain compression point.