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RF Electronics Chapter 5: Frequency Mixers Page 129 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. Figure 5.29 shows the performance of the balanced mixer as an up-converter. The relationship between the spectral components and LO and IF frequencies are shown in table 5.1. It can be seen that a near ideal frequency mixer performance is obtained, with all the unwanted components more than 40 dB below the wanted components. This is good enough for practical applications. The 3IM components increase 3 dB for every 1 dB increase in the RF and IF levels. The RF level can thus be varied to obtain the specified 3IM performance, thereby maximising IF signal and the dynamic range. The LO feed- through at the RF port can be minimised by adding a very small DC signal to the IF port and adjusting that DC signal to cancel the LO signal at the RF port. This cancellation is temperature dependent, since the diode characteristics change slightly with temperature. Figure 5.30 shows the RF voltage for the balanced mixer. These waveforms resemble the ideal multiplier waveforms shown in figure 5.10. The results from the simulation closely agree with those obtained in practice. There are however still some IF components present, which are due to the limited RF-IF isolation caused by the diplexer. The Double Balanced mixer overcomes those limitations. Figure 5.30. RF voltage for a balanced diode mixer as an up-converter. Double Balanced Mixer The Double balanced mixer (DBM), together with the active mixers are the dominant frequency mixers used in non-consumer oriented transmitters and receivers. There are several companies making DBMs, Mini-Circuits is one of the largest of these. Mini- Circuits produce more than 350 different DBMs. Table 5.2 shows a small selection of those. To allow the table to fit, the some parameters have been omitted. Typically the LO frequency range is the same as the RF frequency range, the maximum IF frequency is the same as the RF maximum frequency and the minimum IF frequency is DC. There are many different packages styles available as can be seen from table 5.2. Surface mount packages are now more popular and cheaper. The packages with BNC or SMA connectors are much more expensive. Most of the available DBMs use Core and Wire RF Electronics: Design and Simulation 129 www.cadence.com/go/awr