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High Sensitivity RadioReceiver Design
Webinar
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Panelists
Bobby Matinpour Marketing Manager, Wireless Infrastructure Solutions
Scott Kulchycki Marketing Manager, High Speed Signal Path
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Objectives
Discuss Base Station Market Trends & NeedsReview Radio Receiver BasicsDescribe Receiver Architectures & Trade-OffsDescribe the High-IF Receiver Requirements
RF & IF blocks, anti-aliasing filter, and the ADCDemonstrate an Example Using Nationals Portfolio
ADC16DV160, LMH6517, and LMK04000Call to Action
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Base Station Market Trends & Needs
Network Efficiency More user channels in a given radio
Lower Total Cost of Ownership Infrastructure hardware, deployment and operation
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Base Station Market Trends & Needs
Flexible & High Capacity Base Stations Multi-Carrier
Enable higher capacity per radio Multi-Standard
Flexible deployment along with legacy infrastructure Streamlined development & maintenance
Wideband Enable higher capacity per radio Flexible deployment along with legacy infrastructure Streamlined development & maintenance
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Radio Receiver Basics
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Radio Receiver Overview
Function Translate RF signal to lower frequency digital bits
Wireless Markets & Applications Cellular Base Stations & Repeaters Point-to-Point RF & Microwave Links Microwave Backhaul
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Radio Receiver Figure of Merit
Receiver Sensitivity Normal (non-Blocking) Condition
How small of a signal can the receiver detect and process Most critical receiver performance metric is Noise Figure
Blocking Condition How small of a signal can the receiver detect and process in the
presence of a strong interferer (source closer to antenna)
Most critical receiver performance metric is Linearity
Strong
Interferer
Signal
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Receiver Architectures
Homodyne (Direct Conversion) Directly converting RF to baseband quadrature signals
Simple but difficult to get high performance
Heterodyne Converting RF to low-frequency IF using single or multipledown-conversion stages
Complex but yields the best performance
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Homodyne (Direct Conversion) Receiver
AdvantagesAll IF filtering in baseband No image rejection filters
Disadvantages Needs stringent I & Q channel phase & amplitude balance LO is in-band and can radiate through antenna DC offsets and 2nd order intermodulation are now in-band
DVGAAnti-Aliasing
FilterQuadrature
Mixer
RF FilterLNA
LO
90
ADC
AntennaFilter
Q-channel
I-channel
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Heterodyne Receiver
Advantages Multiple stages of filtering allows for high performance DC offsets and 2nd order intermodulation are now out of band
Disadvantages Requires multiple filtering stages (more complex) Frequency planning is much more complex
IF Filter Chain DVGAAnti-Aliasing
FilterMixerRF FilterLNA
LO
ADCAntenna
Filter
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Filtering in Heterodyne Receivers
signal
RFLO
interfererimage
in-band
blocker
RF Filtering Image band Mixer two-two spurs (2xLO 2xRF) Out-of-band blockers & interferers
High-IF Example
mixer 2-2 spur
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Filtering in Heterodyne Receivers
signal
RFLO
interfererimage
IF
in-band
blocker2nd harmonic of
In-band blocker
signal
in-band blocker
interferer
RF Filtering Image band Mixer two-two spurs (2xLO 2xRF) Out-of-band blockers & interferers
IF Filtering (no more filtering on 2-2 spur & image)
Remaining out-of-band blockers & interferers
Harmonics of the in-band blocker Wide-band noise High-IF Example
mixer 2-2 spur
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Filtering in Heterodyne Receivers
signal
RF
interfererimage
in-band
blocker
RF Filtering Image band Out-of-band blockers & interferers Mixer two-two spurs (2xLO 2xRF)
IF Filtering (no more filtering on 2-2 spur & image)
Remaining out-of-band blockers & interferers
Harmonics of the in-band blocker Wide-band noise Low-IF Example
LOmixer 2-2 spur
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Filtering in Heterodyne Receivers
signal
RF
interferer
IF
in-band
blocker2nd harmonic of
In-band blocker
signal
in-band blocker
interferer
RF Filtering Image band Out-of-band blockers & interferers Mixer two-two spurs (2xLO 2xRF)
IF Filtering (no more filtering on 2-2 spur & image)
Remaining out-of-band blockers & interferers
Harmonics of the in-band blocker Wide-band noise Low-IF Example
image
mixer 2-2 spurLO
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Frequency Planning for a High-IF Receiver
Filtering RF filtering simplifies with higher IF
Image & Mixer 2-2 spurs are further away from the desired signal IF filtering simplifies with higher sample rate & IF
Lower-order filter required
Amps & Converters Data converters perform better at lower IF & sample rates
Better SNR & SFDR Amplifiers perform better at lower IF frequency
Lower Noise & Better Linearity
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IF Filtering Selecting a Sampling Rate
Desired signal
fS/2 fS 3fS/2 2fS
fS/2 fS 3fS/2
Signal will alias
in-band on sampling
Increase
Sampling RateDecreased slope
Relaxed filter requirements
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IF Filtering Selecting an IF
Amplifier HD2 Distortion
Amplifier HD2 Distortion
Increase IF
Decreased slope
Relaxed filter requirements
Desired signal
In-band blocker
Signal will alias
in-band on sampling
fS 3fS/2 2fS
fS2fS 3fSfS/2
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Multi-Carrier Multi-Standard
20-MHz Receiver Example
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Multi-Carrier Receiver Design Example
Requirements (including Multi-Carrier GSM) Sensitivity in 200-kHz bandwidth
-104 dBm under normal condition (no margin) -92 dBm under blocking condition
-16 dBm in-band & out-of band blockers Require 9-dB Carrier-to-Noise-and-Interference Ratio
Frequency Plan ADC Sample Rate = 76.8 or 153.6 Msps IF centered at middle of Nyquist zone
Chose 3rd Nyquist zone (192-MHz) to simplify anti-aliasing filter
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Multi-Carrier Receiver Design Example
Noise & Gain Calculations Under Normal Condition
Noise Thermal Noise Floor = -174 dBm + 10 x log(200e+3) = -121 dBm Maximum Noise Figure = -121 dBm + 9 dB - 104 dBm = 8 dB
Gain No limitation; need to make sure to not saturate any stages
Under Blocking Condition Noise
Not a critical spec since limitation is the blocker Gain
Maximum gain is set by blocker & ADC full-scale (~4-dBm) Rx Gain = 0 dBm (4-dB back-off from FS) (-16 dBm) = 16 dB
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Multi-Carrier Receiver Design Example
IF Filter Chain DVGAAnti-Aliasing
FilterMixerRF FilterLNA
LO
ADCAntenna
Filter
-16 dBm 0 dBm
-92 dBm -76 dBm
Gain = 16 dB
NF = ? dBSignal
Blocker
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Design Example: RF Front-End
IF Filter Chain DVGAMixerRF FilterLNA ADCAntenna
Filter
GNF
OP1dB
-1 dB1 dB
16 dB0.8 dB
14 dBm
-1 dB1 dB
-7.5 dB7.5 dB
8 dBm
Anti-AliasingFilter
LO
Cascaded Noise Factor:
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Design Example: Blocking Condition
IF Filter Chain DVGAMixerRF FilterLNA ADCAntenna
Filter
0 dB9 dB
-5 dB5 dB
? dB? dB
? dBm
?
Anti-AliasingFilter
Cascaded Noise Factor:
GNF
OP1dB
-1 dB1 dB
16 dB0.8 dB
14 dBm
-1 dB1 dB
-7.5 dB7.5 dB
8 dBm
LO
GNF
OP1dB
-20 dB20 dB
20 dB5.5 dB
20 dBm
-20 dB20 dB
20 dB5.5 dB
20 dBm
DVGA Gain RangeBlocking Condition = 16 - 1.5 = 14.5
Normal Condition = -1.5 + DVGA max gain
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Design Example: Blocking Condition
IF Filter Chain DVGAMixerRF FilterLNA ADCAntenna
Filter
GNF
OP1dBOut
-1 dB1 dB
-17 dBm
16 dB0.8 dB
14 dBm-1 dBm
-1 dB1 dB
-2 dBm
-7.5 dB7.5 dB
8 dBm-9.5 dBm
0 dB9 dB
-9.5 dBm
-5 dB5 dB
0 dBm
14.5 dB12 dB
15 dBm5 dBm
?
Anti-AliasingFilter
4-dB back-offfrom fullscale
GNF
OP1dBOut
-20 dB20 dB
-9.5 dBm
20 dB5.5 dB
20 dBm10.5 dBm
-20 dB20 dB
-9.5 dBm
20 dB5.5 dB
20 dBm10.5 dBm
Tracing the BlockerStay 10-dB below P1dB at all times
LO
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Design Example: Normal Condition
IF Filter Chain DVGAMixerRF FilterLNA ADCAntennaFilter
22 dB5.5 dB ?
Anti-AliasingFilter
Cascaded Noise Factor:
0 dB9 dB
-5 dB5 dB
GNF
-1 dB1 dB
16 dB0.8 dB
-1 dB1 dB
-7.5 dB7.5 dB
LO
Max Gain
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Design Example: Normal Condition
IF Filter Chain DVGAMixerRF FilterLNA ADCAntennaFilter
GNF
-1 dB1 dB
16 dB0.8 dB
-1 dB1 dB
-7.5 dB7.5 dB
0 dB9 dB
-4 dB4 dB
22 dB5.5 dB
Gain overall = 23.5 dB
NF overall < 8 dB ADC NF = 27.5
?
LMH651
7
Anti-AliasingFilter
ADC Noise Density = -174 dBm/Hz + 27.5 dB - 3.5-dB margin = -150 dBm/Hz
-150 + 79 = -71 dBm/76.8MHz (156.3 Msps) SNR = 75-dB FS
LOADC1
6DV160
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Design Summary
Review of the Numbers Sensitivity
Meet -104 dBm under normal condition (with 3.5-dB margin) Simulation confirms -107.2 dBm
Meet -92 dBm under blocking condition (with 4-dB margin) Simulation confirms -95.5 dBm
Nationals High-IF Receive Sub-System LMH6517, ADC16DV160, and LMK04000
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High IF Receiver Sub-System
Solution using LMH6517+ADC16DV160+LMK04000 Accelerate design of multi-carrier multi-standard receivers
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Call to Action
Go to Nationals website for more information ADC16DV160: http://www.national.com/pf/DC/ADC16DV160.html LMH6517: http://www.national.com/mpf/LM/LMH6517.html LMK04000: http://www.national.com/pf/LM/LMK04000.html
Check on High-IF Sub-System Board (Late Sept) View other webinars such as Clock & Timing Webinar on
PowerWise Design University
Download & examine Wireless Communications Brochure:http://www.national.com/vcm/NSC_Content/Files/en_US/
Documents/national_comms_infrastructure.pdf
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Contact Information
Bobby Matinpour Marketing Manager, Wireless Infrastructure Solutions Email: [email protected] Desk: (408) 721- 7235
Mobile: (408) 332 - 4321
Scott Kulchycki Marketing Manager, High Speed Signal Path Email: [email protected] Desk: (408) 721- 5851 Mobile: (408) 832 - 9391
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2009 National Semiconductor Corporation