Lect16_Receiver Arch (I)

Lect16_Receiver Arch (I) - ECE 620 Introduction to RF...

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ECE 620 Introduction to RF Integrated Circuits Prof. Waleed Khalil Lecture Receivers Architecture (I) 16 1
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Outline RF Filtering Heterodyne Receivers Intermediate Frequency 2
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Selectivity vs. Sensitivity In RF, it is impossible to select the desired low power channel from nearby high power in-band and out-of-band interferers ??? Ratio of channel freq. to bandwidth is very high ultrahigh Q filters EX. GSM: f c = 1900 MHz, BW= 200 kHz Q= 9500 Need highly tunable filters to select channels across the desired band Selectivity vs. sensitivity tradeoff A tunable high selectivity filter requires multiple filtering elements (stages) Highly lossy Directly impacts receiver NF Sensitivity degradation 3 BW f Q c = f c BW In-band Interf. Out-of-band Interf. = Desired Channel BPF LNA
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Frequency Downconversion Use band-select filter to reject high power out-of-band interferers Out-of-band interferes can be higher than P 1dB of LNA LNA gain compression Cascaded NF degradation Filter Q still relatively high Use off-chip surface acoustic wave (SAW) filter instead of on-chip RC filter
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This note was uploaded on 11/21/2011 for the course ECE 620 taught by Professor Khalil during the Fall '11 term at Ohio State.

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Lect16_Receiver Arch (I) - ECE 620 Introduction to RF...

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