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Mobile network operating costs are driving the requirement for increased infrastructure efficiency, particularly in the final stage RF power amplifier. The venerable Chireix outphasing architecture proposed in 1936 by Henry Chireix has been updated with Gallium Nitride HEMT transistors operating in class E, and shown to deliver class leading efficiency.
To amplify weak signals received by the antenna in communication systems, low noise amplifiers (LNAs) are deployed. LNAs are used in various applications such as GPS receivers, wireless data systems, satellite communications, cellular handsets, radio systems, etc.
RF transmitters are an essential part of modern communications. Designed and assembled from core RF components, RF transmitters have many different forms and applications. We often think of RF transmitters in wireless communications, but the concept applies equally to wired applications such as cable television.
This artice is the second half of a detailed discussion of noise factor for modern RF radio receivers. In Part 1 we discussed the general concept of noise figure and how it is used to convey noise-performance requirements by product definers and circuit designers. It is also used to predict the overall sensitivity of receiver systems. We also presented calculations for a cascaded receiver. In this continuation article we focus on the Y-factor measurement as it applies to mixers. We state which measurement is applicable to the cascade equations derived in Part 1. We also explore some variations of the measurement method the could be used to obtain an approximation to the SSB noise figure of a mixer.
System Noise-Figure Analysis for Modern Radio Receivers: Part 1, Calculations for a Cascaded Receiver
This article ties together the fundamenal definition of noise figure, equation-based analysis of cascade blocks involving mixers, and typical lab techniques for measuring noise figure. In this Part 1 we show how the cascaded noise figure equation is modified by the presence of one or mixers and we derive the applicable equations for a number of popular downconversion architectures. We continue this discussion in Part 2 of this series where we describe the Y-factor method of noise-figure measurement. In Part 2 we focus on the case of a mixer as the device under test in order to identify appropriate measurement methods for mixer noise figures that can be validly applied using the cascade equations derived in Part 1.