Wideband active mixer with high gain and low noise figure
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This work presents active double-balanced down converter mixer with some modification. Gilbert topology provide overall good gain and LO-RF isolation. It has poor noise figure performance. It is narrow band in terms of conversion gain, noise figure and input matching. So noise cancelling transconductor is presented which lower noise figure of first stage. With this technique, noise from input matching network can be eliminated and noise figure from rest of circuit can be minimized. To provide current requirement of transconductor stage and to increase overall gain of mixer circuit current-bleeding circuit is used. Inductive peaking technique is used to make active mixer wideband in terms of parameters i.e. gain, noise-figure, third order input-intercept point, isolation and input-reflection coefficient. This circuit is implemented using MOSFET 0.25 ?m technology. It achieves conversion gain of 18.0 to 22.9 dB, noise figure of 2.6 to 3.5 dB, third order input-intercept point is 6 dBm over a frequency range 1.0 to 6.2 GHz. LO-RF isolation is more than 77 dB and input-reflection coefficient is better than -10.7 dB in the entire frequency range. Mixer consumes 10.2 mA current from 2.5 V supply.
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