Browsing by Subject "Balanced amplifiers"

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Gain variation and noise figure degradation in balanced amplifiers
    (2017-07) Coşkun, Akif Alperen
    Although using balanced amplifiers in modern wireless communication systems has many advantages, the output and the noise response of the balanced ampli- fiers may vary from the expected value considerably due to the imperfections in the amplifier and the divider/combiner sections. First, we analyze the variation in the total gain of the balanced amplifiers using 2-way 0ff power dividers and 90ff couplers. In this context, mathematical analyses are made and analytical expressions are obtained to compare the two topologies. Analytical expressions show that the uncertainty in the total gain is more if the 90ff coupler is used in the balanced structure as opposed to a 2-way 0ff power divider for the same return loss/isolation values. Then, we present exact and approximate analytical results for the noise figure and noise parameters of the balanced amplifier in divider topology by using the noise waves. By the help of the noise wave approach, the output noise powers generated by each element in the balanced amplifier are derived. Y-parameters are used to determine the noise waves and the correlation matrix of the divider whereas the noise parameters are used to write the noise waves of the amplifier. Balanced amplifiers suffer in the noise figure performance in comparison to a stand-alone amplifier even with an ideal input divider. The noise parameters degrade further with an imperfect divider. Not only the nonzero return loss and the isolation but also the ohmic loss, amplitude and phase imbalances are considered. Besides, non-zero optimal source impedance affects the noise parameters of the balanced amplifier. Measurement results are also presented as a verification.
  • Thumbnail Image
    ItemOpen Access
    Noise figure degradation in balanced amplifiers
    (Institute of Electrical and Electronics Engineers Inc., 2017) Coskun, A. A.; Atalar, Abdullah
    Balanced amplifiers suffer from the noise figure performance in comparison with a stand-alone amplifier even with an ideal input divider. The noise parameters degrade further with an imperfect divider. We present exact and approximate analytical results for the noise figure and noise parameters of the balanced amplifier in divider topology. Measurement results are also presented as a verification.
  • Thumbnail Image
    ItemOpen Access
    Noise figure of a balanced amplifier
    (Institute of Electrical and Electronics Engineers, 2018) Coskun, A. A.; Atalar, Abdullah
    Noise figure expression of a balanced amplifier built with lossy divider and combiner and two imperfectly noise-matched component amplifiers is derived analytically using the method of noise waves in terms of the noise parameters of the amplifiers. We present analytical expressions for the three noise parameters of the balanced amplifier. We show that a low-noise amplifier optimized to be used as a stand-alone amplifier is not the optimum choice for the component amplifiers of a balanced amplifier. The derived expressions can be used to choose or optimize the component amplifiers.