Abstract
Measurement results of the signals emanating from both IF and LO ports of a double balanced mixer are presented, and, thus, it is shown that the linearization of the output in a down-converting mixer by the summation of the IF signal and the signal emanating from the LO or RF port is feasible. Feedforward-based architectures for the linearization of down-conversion mixers are introduced that exploit this phenomenon, and linearity performance results of the frequency translation of both two-tone and TETRA-modulated signals are presented. This technique employs only a single mixer and hence overcomes the complexity of other mixer linearization schemes. The overall processing gain of the system is limited by the level of wanted signal present in the error signal.
Highlights
Intermodulation Distortion (IMD), caused by odd-order nonlinearities, falls close to the required signal and is impracticable to remove by filtering
Of most concern with double-balanced diode mixers is third-order intermodulation distortion (3IMD) as this is the greatest contributor to the reduction in system dynamic range
In standard techniques for the linearization of mixers [1, 2] a second frequency translation step is required to ensure that the signal to be linearized and the error signal are both at the same frequency
Summary
Intermodulation Distortion (IMD), caused by odd-order nonlinearities, falls close to the required signal and is impracticable to remove by filtering. Of most concern with double-balanced diode mixers is third-order intermodulation distortion (3IMD) as this is the greatest contributor to the reduction in system dynamic range If this would be a problem within a system, a higher LO power mixer would be chosen to increase the linearity of the process. The mixer is a generator of distortion (i.e., it may be considered as the source of the undesired nonlinear output), and so the balance of the distortion energy observed at the three ports is not the same as that of the wanted signal This leads to different signal-to-distortion levels of the IF signal appearing at the IF, LO, and RF ports and, a mixer linearization scheme without the use of a second mixer is feasible. Energy, nor formed by the application of a model of the mixer nonlinear performance
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