RF Electronics Chapter 5: Frequency Mixers Page 155
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
Figure 5.73 180 Hybrid DBM used for up-conversion.
At present companies like Analog Devices, produce commercial core and wire mixers for
RF frequencies up to 20 GHz. For designs up to 20 GHz, commercial transformer based
DBMs are smaller and cheaper than the designs shown in figures 5.53 to 5.73.
Transmission line based, balanced and double balanced mixer designs can operate above
20 GHz and show that as long as the RF, LO and IF signals are combined correctly, a
frequency mixer with a low conversion loss and a clean spectrum will result. The design
techniques shown in figures 5.53 to 5.73 can be implemented in LTCC, silicon or gallium
arsenide. They can form the basis for MMIC DBM designs, described near the end of this
chapter.
Figure 5.74. Marchand Hybrid DBM used for up-conversion.
Active Single Transistor Mixer
Figure 5.75 shows the Low_Power_Mixer [12], which is an active single diode mixer
from the Cadence AWR DE mixer examples. This example also shows how Conversion
Loss or Gain, Gain Compression and other mixer parameters can be determined using
MWO. An active single transistor mixer has a similar spectral performance to a passive
single diode mixer, but has a conversion gain. The mixer of figure 5.75 has a conversion
gain of more than 10 dB. Active single transistor mixers are used in many consumer
devices like radio and TV receivers. It is possible to improve the mixing performance by
using two transistors in a push-push amplifier configuration and thus produce an active
balanced mixer.
RF Electronics: Design and Simulation
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