Administrative Project Discussions report submission on Frid Dec 4th make appointment via sign up sheet Student presentations Dec 3rd Dec 8th Office hours 567 Cory Tues Dec 8th 4 to 5pm Wed Dec 9th 10 to 11am Questions can also be asked via email EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 1 EE247 Lecture 26 Bandpass modulators ADC figures of merit Term project student presentations Examples of systems utilizing analog digital interface circuitry not part of final exam Acknowledgements EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 2 Bandpass Modulator vIN Resonator dOUT DAC Replace the integrator in 1st order lowpass with a resonator 2nd order bandpass EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 3 Bandpass Modulator Example 6th Order Measured output for a bandpass prior to digital filtering Quantization Noise Input Sinusoid Key Point NTF notch type shape STF bandpass shape Ref Paolo Cusinato et al A 3 3 V CMOS 10 7 MHz Sixth Order Bandpass Modulator with 74 dB Dynamic Range JSSCC VOL 36 NO 4 APRIL 2001 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 4 Bandpass Characteristics Oversampling ratio defined as fs 2B where B signal bandwidth Typically sampling frequency is chosen to be fs 4xfcenter where fcenter bandpass filter center frequency STF has a bandpass shape while NTF has a notch or band reject shape To achieve same resolution as lowpass need twice as many integrators EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 5 Bandpass Modulator Dynamic Range As a Function of Modulator Order K K 6 21dB Octave K 4 15dB Octave K 2 9dB Octave Bandpass resolution for order K is the same as lowpass resolution with order L K 2 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 6 Example Sixth Order Bandpass Modulator Simulated noise transfer function Simulated signal transfer function Ref Paolo Cusinato et al A 3 3 V CMOS 10 7 MHz Sixth Order Bandpass Modulator with 74 dB Dynamic Range JSSCC VOL 36 NO 4 APRIL 2001 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 7 Example Sixth Order Bandpass Modulator Features Measured Performance Summary fs 4xfcenter B OSR fs 2B Ref Paolo Cusinato et al A 3 3 V CMOS 10 7 MHz Sixth Order Bandpass Modulator with 74 dB Dynamic Range JSSCC VOL 36 NO 4 APRIL 2001 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 8 Summary Oversampled ADCs Noise shaping utilized to reduce baseband quantization noise power Reduced precision requirement for analog building blocks compared to Nyquist rate converters Relaxed transition band requirements for analog anti aliasing filters due to oversampling Takes advantage of low cost low power digital filtering Speed is traded for resolution Typically used for lower frequency applications compared to Nyquist rate ADCs EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 9 ADC Figures of Merit Objective Want to compare performance of different ADCs Can use FOM to combine several performance metrics to get one single number What are reasonable FOM for ADCs EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 10 ADC Figures of Merit FOM 1 f s 2 ENOB This FOM suggests that adding a bit to an ADC is just as hard as doubling its bandwidth Is this a good assumption Ref R H Walden Analog to digital converter survey and analysis IEEE J Selected Areas Comm April 1999 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 11 Survey Data 1bit Octave Ref R H Walden Analog to digital converter survey and analysis IEEE J Selected Areas Comm April 1999 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 12 ADC Figures of Merit FOM 2 Power f s 2 ENOB J conv Sometimes inverse of this metric is used In typical circuits power speed FOM2 captures this tradeoff correctly How about power vs ENOB One more bit 2x in power Ref R H Walden Analog to digital converter survey and analysis IEEE J Selected Areas Comm April 1999 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 13 ADC Figures of Merit One more bit means 6dB SNR 4x less noise power 4x larger C Power Gm C increases 4x Even worse Flash ADC Extra bit means 2x number of comparators Each of them needs double precision Transistor area 4x Current 4x to keep same current density Net result Power increases 8x EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 14 ADC Figures of Merit FOM2 seems not quite appropriate but somehow still standard in literature papers Tends to work because Not all power in an ADC is noise limited E g Digital power biasing circuits etc Avoid comparing different resolution ADCs using FOM2 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 15 ADC Figures of Merit FOM 3 Power Speed Compare only power of ADCs with approximately same ENOB Useful numbers 10b 9 ENOB ADCs 1 mW MSample sec Note the ISSCC 05 example 0 33mW MS sec 12b 11 ENOB ADCs 4 mW MSample sec EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 16 10 Bit ADC Power Speed Yoshioko ISSCC 05 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 17 12 Bit ADC Power Speed Loloee ESSIRC 2002 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 18 Material Covered in EE247 Filters Continuous time filters Biquads ladder type filters Opamp RC Opamp MOSFET C gm C filters Automatic frequency tuning Switched capacitor SC filters Data Converters D A converter architectures A D converter Nyquist rate ADC Flash Interpolating Folding Pipeline ADCs Self calibration techniques Oversampled converters EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 19 E E Circuit Courses vs Frequency Range RF Band 500kHz 100GHz IF Band 455kHz AM Radio 10 7MHz 80MHz FM Radio Cellular Phone 100MHz Baseband DC 500MHz EE240 EE247 EE242 EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 20 Systems Including Analog Digital Interface Circuitry Not Included in Final Exam Wireline communications Telephone related DSL ISDN CODEC Television circuitry Cable modems TV tuners Ethernet 10 1Gigabit 10 100BaseT Wireless Cellular telephone CDMA Analog GSM Wireless LAN Blue tooth 802 11a b g Radio analog digital Television Disk drives Fiber optic systems EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 21 Wireline Communications Telephone Based EECS 247 Lecture 26 Bandpass Oversampled ADCs Systems 2009 Page 22 Data Transmission Over Existing Twisted Pair Phone Lines Backbone Digital
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