الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
The maximum gain (GP.maJ occurs only at point where rs = r;: and
rL = r;ut also the minimum noise figure (NFmin) occurs only at point where rs = ropt. These two points cannot, in general, be obtained simultaneously so the trade-off is made to select a point which gives the required gain with acceptable noise.
The maximum gain of the implemented circuit occurs at 2.06 GHz frequency which deviates 0.06 GHz from the central point of 2 GHz at which the matching circuits are designed which means that the gain of LNA circuit is very sensitive to the lengths of transmission lines used in matching circuits.
This deviation may occur due to small variation in the lengths of transmission lines during fabrication of the circuit.
~ Comparing the experimental results with that of simulated results, it is obvious that:
The gain (Gp) is decreased by 2.55 dB and the noise figure(NF) is increased by 0.04 dB. This deviation may occur due to on ~r -more of the following reasons:
• The resident losses in cable connections and coaxial connectors.
• The tolerance in microstrip and transistor parameters.
• The imperfect calibration of measuring devices.
• The variation of transistor temperature during measurements.
)0 The circuit is sensitive for positive and negative variations of micro strip lengths of matching circuits. The positive variation has a great effect on the operating power gain and considerable effect on the noise figure.
• The 20% of positive variation of TL4 (the open stub of output matching circuit) decreases the operating power gain by 9 dB and increases the noise figure by 0.052 dB.
• The 20% of positive variation of TL2 (the open stub of input . matching circuit) increases the noise figure by 0.176 dB and decreases the operating power gain by 0.31 dB. br On the other-hand the negative variation of length has a small effect on the noise figure and considerable effect on the operating power gain.
• The 20% of negative variation of TL3 (the series T.L of output matching circuit) decreases the operating power gain by 3.28 dB and while the noise figure is constant.