RFIC_Lecture_Note_No1_p1-p12 (RF front-end)

RFIC_Lecture_Note_No1_p1-p12 (RF front-end) - ECE695F RFIC...

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ECE695F RFIC Prof. S. Mohammadi Radio Frequency Integrated Circuits Modulation Modulator Demodulator Channel Baseband Signal Detected Signal Transmitter Receiver Modulation Varying certain parameter of a carrier according to the baseband signal * Assume a sinusoidal carrier ] ) ( cos[ ) ( ) ( t t t a t c θ ω χ + = Amplitude modulation (AM) : carrier baseband ] cos[ ) ( ) ( + = t t a t x c varies according to Baseband AM Signal )] ( 1 [ ) ( t mx A t a BB c + = Carrier frequency Amplitude Modulation index Baseband signal In frequency domain baseband carrier c c 0 0 c c 0 - 1 -
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ECE695F RFIC Prof. S. Mohammadi Detection of AM AM Low Pass Filter baseband t c ω cos Local oscillator how to generate exactly the same amplitute For small modulation indexes 0 ) ( 1 > + t mx BB You can use a simple leaky peak detector for detection baseband AM Phase and Frequency Modulation (PM), (FM) PM: )] ( cos[ ) ( t mx t A t x BB C C + = m: phase modulation index FM: ] ) ( cos[ ) ( dt t x m t A t x t BB C C + = m: frequency modulation index excess frequency: dt d θ - 2 -
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ECE695F RFIC Prof. S. Mohammadi Difference b/w PM & FM if at t x BB = ) ( Ramp input PM Signal: ] ) cos[( ) ( t A t x C C α ω + = Shift in carrier frequency if a t x BB = ) ( Step input FM Signal: ] ) cos[( ) ( t A t x C C + = Shift in carrier frequency ) ( t x BB PM Signal FM Signal - 3 -
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ECE695F RFIC Prof. S. Mohammadi A voltage controlled oscillator (VCO) is a simple frequency modulator ) ( t x BB FM FM demodulator: C R Digital Modulation Similar to AM, PM, and FM digital modulations are called: Amplitude Shift Keying (ASK) Phase Shift Keying (PSK) Frequency Shift Keying (FSK) f 1 f 2 you can have binary and M-ary signalling Example: Quadrature modulation: QPSK - 4 -
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ECE695F RFIC Prof. S. Mohammadi Cellular System: available spectrum: e.g. 25MHz around 900MHz For 100000 users at the same time
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RFIC_Lecture_Note_No1_p1-p12 (RF front-end) - ECE695F RFIC...

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