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Microwave Mixer Design
Published in Mike Golio, Commercial Wireless Circuits and Components Handbook, 2018
At the beginning of the 20th century, RF detectors were crude, consisting of a semiconductor crystal contacted by a fine wire (“whisker”), which had to be adjusted periodically so that the detector would keep functioning. With the advent of the triode, a significant improvement in receiver sensitivity was obtained by adding amplification in front of and after the detector. A real advance in performance came with the invention by Edwin Armstrong of the super regenerative receiver. Armstrong was also the first to use a vacuum tube as a frequency converter (mixer) to shift the frequency of an incoming signal to an intermediate frequency (IF), where it could be amplified and detected with good selectivity. The superheterodyne receiver, which is the major advance in receiver architecture to date, is still employed in virtually every receiving system.
Project 7: AM Receivers
Published in Thad B. Welch, Cameron H.G. Wright, Michael G. Morrow, ® to C with the TMS320C6x DSPs, 2016
Thad B. Welch, Cameron H.G. Wright, Michael G. Morrow
Having made all of these observations, actual AM radios typically use a frequency selective, intermediate frequency (IF) stage prior to the envelope detector. This type of system is called a “superheterodyne receiver” or simply a “superhet.” The IF-based system provides significant end-to-end gain without amplifier instability/oscillation, as well as providing for much better isolation of the desired frequency channel from any adjacent channels. Better channel isolation is accomplished by the use of a high performance IF filter which then allows the use of lower performance (i.e., less expensive) RF and audio frequency filters.
Mixer signal processing
Published in Geoff Lewis, Communications Technology Handbook, 2013
This technique involves the introduction of two signals into a nonlinear circuit with square law characteristics, so that harmonics and intermodulation are deliberately generated. Often diodes are used for this purpose, but field effect devices (FETs) have a more nearly square law mutual characteristic. This then allows some particular product of mixing to be extracted using a filter network. The concept forms the basis of the superheterodyne receiver and the frequency translation process is shown in Fig. 21.1.
A reconfigurable wireless superheterodyne receiver for multi-standard communication systems
Published in International Journal of Electronics, 2023
Qing Wang, Yongle Wu, Yue Qi, Weimin Wang
At present, there are many mainstream wireless receiver architectures for communication equipment. Such as superheterodyne receiver architecture (Dan et al., 2019), zero intermediate frequency (zero-IF) receiver architecture (T. Wang et al., 2019), and low intermediate frequency (low-IF) receiver architecture (Zhang et al., 2018). Among them, the superheterodyne receiver architecture is widely used in wireless communication systems. The superheterodyne receiver has many advantages, such as excellent frequency selection characteristics, good interference suppression, and a large dynamic range. The zero-IF receiver is simple and easily integrated, but noise and linearity are not as good as the superheterodyne receiver. The cost of the low-IF receiver is high because it needs a high-performance Analog-to-Digital Converter. According to our design requirements, we finally choose the superheterodyne structure to form the proposed receiver.