3.2.3 Dynamic Range

Chapter 3.2.3 Dynamic Range

Radio Frequency Integrated Circuit Design Second Edition Book
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Radio Frequency Integrated Circuit Design Second Edition Book

  • 54 System Level Architecture and Design ConsiderationsIn general, the IIP2 of cascaded stages will be given by: =+++ …112IIP2IIP2 _1IIP2 _ 2IIP2 _ 311vvvAA Avvvv (3.26)3.2.3  Dynamic RangeSo far, we have discussed noise and linearity in circuits. Noise determines how small a signal a receiver can handle, while linearity determines how large a signal a receiver can handle. If operation up to the 1-dB compression point is allowed (for about 10% distortion, or IM3 is about -20 dB with respect to the desired output), then the dy-namic range is from the minimum detectable signal to this point. This is illustrated in Figure 3.10. In this figure, intermodulation components are above the minimum detectable signal for Pin > -32 dBm, for which Pout = -23 dBm. Thus, for any Pout between the minimum detectable signal of -105 dBm and -23 dBm, no intermodula-tion components can be seen, the so called spurious free dynamic range is 82 dB.Example 3.3: Determining Dynamic RangeIn Example 3.1 we determined the sensitivity of a receiver system. Figure 3.11 shows this receiver again with the linearity of the mixer and LNA specified. Deter-mine the dynamic range of this receiver.Figure 3.10  Plot of input output power of fundamental and IM3 versus input power showing dynamic range.