Q channel rf filter ir filter if filter gaas or

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Q channel RF filter IR filter IF filter GaAs or Bipolar Bipolar CMOS 39 n Conventional RF receiver u GaAs or Bipolar for RF and IF stage u CMOS for baseband circuit
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IF Signal Conversion Bandpass modulation instead of lowpass modulation. IF Bandpass DSM Digital demodulation I channel Q channel 40 n n In general, limited by CMOS circuit speed of ADC.
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Bandpass Oversampling Converter n Bandpass for IF signal 41
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Bandpass Oversampling Converter Noise-shaping Band pass filter 42 f c f c D = f f OSR S 2 n The oversampling ratio for a bandpass converter is equal to the ratio of the sampling rate, f s , to two times the width of the narrowband filter, . Δ 2f
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Bandpass Oversampling Converter ( ) 1 2 + = z z z H 1MHz 4 f s = 1MHz 4 f s = 4MHz f s = 4MHz f s = kHz 1 f 0 0 = kHz 1 f 0 = D /2 f s /2 f s dc 0 2f Z-plane ---zero dc D f Z-plane ---zero H(z) 1 1 (z) N TF + = 1 + = z (z) N 2 43 200 2f f OSR (a) 0 s = = 200 2f f OSR (b) s = = Δ H(z) y(n) Quantizer u(n) - 1 Z - 1 Z - - n 9dB/octave improvement <Noise-transfer-function Zeros > 1 2 + + z z TF
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Linearity of Two-Level Converters n Three periodic patterns ( V1 and V2 are volt. ) 1 ± ( ) 2 } ..... 1, 1, 1, 1, 1, 1, 1, 1, { : 0 0 1 A A T V a + = ® - - - - ( ) 3 2 } ..... 1, 1, 1, 1, 1, 1, 1, 1, 1, { : 3 1 0 1 A A T V b + = ® - - - ( ) 3 2 } ..... 1, 1, 1, 1, 1, 1, 1, 1, 1, { : 3 1 0 1 A A T V c + = ® - - - - - - - 44 V2 V1 1 -1 1 1 1 -1 -1 Ideal Binary symbol 1 A 0 A 1 A 0 A 1 A 0 A 1 A Area for symbol
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Nonlinearity for Typical Case ( ) ( ) 2 2 , ..... } 1 , 1 , 1 , 1 { : 0 2 1 2 1 0 1 d d d d + + = + + + = ® - - t V A A t V a d ( ) ( ) 3 3 2 , ..... } 1 , 1 , 1 { : 3 1 2 1 2 1 0 1 d d d d + + = + + + = ® - t V A A t V b e ( ) ( ) 2 , ..... } 1 , 1 , 1 { : 3 1 2 1 2 1 0 1 d d d d + + = + + + = ® - - - t V A A t V 45 3 3 c f V2 V1 1 -1 1 1 1 -1 -1 Ideal Typical Binary Area for symbol 1 1 A d + 2 0 A d + 1 A 0 A 1 1 A d + 2 0 A d + 1 1 A d +
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Momoryless Coding for Linearity V2 Ideal Typical n Memoryless coding scheme by Return-to-Zero. 46 V1 1 -1 1 1 1 -1 -1 Binary Area for symbol 1 A 0 A 1 A 0 A 1 A 0 A 1 A
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Idle Tones and Dithering n Idle Tones ( ) 16 f S Þ - - - - - - = } ..... 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, { n y ( ) 3 f S Þ - - - = } 1, ..... 1, 1, 1, 1, 1, 1, 1, 1, { n y 47 y(n) Dither signal u(n) H(z) Quantizer n Dithering
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Opamp Gain n Finite opamp gain n Infinite opamp gain 2 f + - + - OUT C 2 1 f C 1 V in < Switch-capacitor integrator > ( ) ö æ ( ) ( ) ( ) 1 1 2 1 - ÷ ÷ ø ö ç ç è æ - = = z C C z V z V z H i O 48 ( ) ( ) 1 1 1 2 1 2 1 - ÷ ÷ ø ö ç ç è æ + ÷ ÷ ø ç ç è - = = A C C z C C z V z V z H i O ( ) A z z 1 1 1 - = Þ = p 2 A 1 f f S 0 > p OSR A > n If f 0 is below where the quantization noise flattens out, then we are not obtaining any further noise-shaping benefits.
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Multi-Bit Oversampling Converter n Dynamic element matching 3-bit D/A converter C C oder er 49 C C C C C C b 1 b 2 b 3 Thermometer-type deco Eight-line randomize Analog output
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Example of Third-Order Modulator ( ) z NTF 3 1 - = /2 π ω = n NTF: Third-order Butterworth high-pass configuration n Passband edge = fs / 20 n Peak gain = 1.37 (to satisfy Lee s rule of thumb.) 50 ( ) z D ( ) 5321 . 0 9294 . 1 3741 . 2 1 2 3 3 - + - - = z z z z NTF 1 j j - -1 π ω = Butterworth poles Three zeros at 0 = ω
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Find H(z) from NTF x(n) y(n) u(n) H(z) - e(n) ( ) 5321 . 0 9294 . 1 3741 . 2 1 2 3 3 - + - - = z z z z NTF n From previous analysis 51 H(z) 1 1 E(z) Y(z) NTF(z) + = = ( ) ( ) ( ) z NTF z NTF z H - = 1 ( ) ( ) (1) 1 4679 . 0 0706 . 1 6259 . 0
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