RF Electronics Chapter 5: Frequency Mixers Page 124
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
Figure 5.23. RF spectrum of a single diode mixer as an up-converter.
The RF output spectrum is shown in figure 5.23. From this spectrum, it can be seen that
the conversion loss, being the amplitude of the 100 MHz RF component due to the 5 MHz
IF signal is the same as for the down-converter. The components around 100 MHz show
a large 105 MHz LO component in the RF output, indicating only a 7+3.2 = 10.21 dB
LO-RF isolation. The LO spectral component at the RF port is larger than any of the
wanted components. The second harmonic components at 90 MHz and 110 MHz are
slightly asymmetrical. There are significant components at harmonics of the LO
frequency, which must be filtered out in most practical applications.
Figure 5.24. RF voltage for a single diode mixer as an up-converter.
The RF voltage waveforms can be determined using the Vtime measurement in a similar
manner as for the down-converter shown in figure 5.21. The results for the up-converter
are shown in figure 5.24 and are highly asymmetrical. The waveform is rich in harmonics
as can be seen from the spectrum of figure 5.23.
RF Electronics: Design and Simulation
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