1 Using WaveVision 5 to Analyze the Low-IF Receiver Reference Design

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Using WaveVision 5 to Analyze the Low-IF Receiver

Reference Design

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Josh CarnesMark Rives

Data Conversion Systems

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© 2008 National Semiconductor Corporation

Outline

• WaveVision 5 Software

• WaveVision 5 Hardware

• ADC14DS105KARB

• WaveVision 5 + ADC14DS105KARB Demo

• Analog Bowl

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WaveVision 5 Software Overview

• Completely new non-Java-based GUI• Improved accuracy• New features

– Multiple plot windows– Multiple traces– Improved plot annotations– Continuous capture– Averaging– Signal generators– Exclusion masks– New window functions

• DLL manages the hardware interface so other software can easily access data from our evaluation boards

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WaveVision 5 SoftwareMultiple Windows

• Multiple windows can be used to capture data

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WaveVision 5 SoftwareMultiple Traces/Channels

• Multiple traces can be viewed on 4 different “channels”

• View performance of all channels simultaneously

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WaveVision 5 SoftwareThe New Math

• FFT routines based on the same Matlab code used internally by design and apps.– Interpolated fundamental location

• Improved harmonic location• Improved accuracy

– Cosine windows: 4, 6 and 11-term– Programmable number of harmonics observed– Programmable bin exclusion at DC, fundamental and

harmonics– User specified exclusion regions

• Phase noise removal• Spurious removal

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WaveVision 5 SoftwareOmitting Bins in Calculations

• Bin omissions remove the effects of DC offsets and windowing function lobes from calculations

Omit near HarmsOmit near Fund

Omit near DC

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WaveVision 5 SoftwareOmitting Bins in Calculations

• FFT exclusion areas allow the flexibility to define regions that are excluded from calculations

Phase Noise Exclusion

SNR without exclusion= 71.1 dBFS

SNR with exclusion= 73.3 dBFS

R-click

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WaveVision 5 SoftwareSpecifying Harmonics

• Specifying the harmonics (up to 25) controls the distortion contributions to the THD– Fractional interpolation gives improved location accuracy

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WaveVision 5 SoftwareWindowing Functions

• New family of windows yields more consistently accurate results• 4-term, 6-term, and 11-term Cosine windows• Very good sideband suppression

• Higher order gives more sideband suppression but larger main lobe

Window Side-lobe suppression

4-term 98 dB

6-term 153 dB

11-term 290 dB

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WaveVision 5 SoftwareSNR

• SNR is the sum of all FFT bins except:– DC– Fundamental– N Harmonics

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WaveVision 5 SoftwareSINAD

• SINAD is the sum of all FFT bins except:– DC– Fundamental

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WaveVision 5 SoftwareTHD

• THD is the sum of N Harmonics

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WaveVision 5 SoftwareSFDR

• SFDR is the difference between the fundamental and the next biggest signal in the FFT

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WaveVision 5 SoftwareSFDR Errors

• Sometimes signals near DC can appear as SFDR. Adjust the ‘Bins to omit at DC’ to correct.

Low frequency information near DC may affect the SFDR.

zoomed-in view

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WaveVision 5 SoftwareNoise Floor

• Integrated Noise Floor is SNR expressed in dBFS / Nyquist or all the noise integrated from DC to Nyquist

• Average Noise Floor is the SNR expressed in dBFS / bin and is roughly the displayed average noise level of the FFT

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WaveVision 5 SoftwareContinuous Capture

• Continuous capture allows observation of stimuli changes in near real-time

• Update rate dependent on # samples per capture• Future updates to WaveVision 5 capture board will

enhance speed/update rate• Continuous capture uses a lot of processor time, making

GUI less responsive

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WaveVision 5 SoftwareFFT Averaging

• Averaging can be enabled when continuous capture is active • Averaging smoothes the noise floor in the FFT, making small

signals easier to see

Averaging disabled Averaging enabled

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WaveVision 5 SoftwareAverage Noise Floor

• When using a windowing function, the observed average noise is higher than the calculated (correct) average noise

• The difference is window gain in dB• To place the fundamental peak at the proper power level, the

entire spectrum is normalized by the window gain, causing an upward shift in the average noise floor

Observed average noise

Calculated average noise

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Outline



• ADC14DS105KARB


• Analog Bowl

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WaveVision 5 Hardware Features

• Transfers data rapidly at high-speed with USB 2.0(USB1.1 compatible)

• Provides jumperless plug-and-play configuration• Supports a wide variety of ADC Evaluation Boards

including many WaveVision4 compatible evaluation boards

• Fast data capture – 36 parallel CMOS signals at up to 100 MHz (DDR mode)– 28 parallel LVDS pairs at up to 375 MHz (DDR mode)– 12 differential serial pairs in dual-lane CDF at up to 400 MHz

(DDR mode)• Base memory capable of storing 64k, 16-bit wide samples• DUT control through SPI interface

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WaveVision 5 HardwareBlock Diagram

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WaveVision 5 HardwarePCB Photo

High High Speed Speed

LVDS I/OLVDS I/O

CMOS + CMOS + Low Speed Low Speed LVDS I/OLVDS I/OPower Power

InputInput

Power Power SwitchSwitch

USB 2.0USB 2.0

Fu

ture

bu

sH

M-Z

d

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Outline



• ADC14DS105KARB


• Analog Bowl

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Near-Zero IF Receiver Requirements

• 3G Wireless Receiver– ADC Sample Rate 92.16 Msps– Input Frequency < 40 MHz– Input Signal Bandwidth < 20 MHz– > 70 dB SNR– > 80 dB SFDR– Dual ADC for Quadrature (I/Q) Processing

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ADC14DS105KARB Near-Zero IF Receiver Reference Board

ADC14DS105

LMK02000

LMH6552

Reference Osc VCXO

Chan A

LMH6552

SD1_A

SD0_A

+

LowpassFilter

Fc ≈ 35 MHz

LowpassFilter

Fc ≈ 35 MHz

SD1_B

SD0_B

Chan B

LocalOscillator

LNA

Low IF Reference Board

90

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Amplifier + ADC Circuit Implementation

127

+

-

LMH6552

V+

V-

22pF

127

-

+

100

100

274

274

ADC14DS105

VCOM

14-Bit 105 MSPS

620nH

620nH

6850

0.1uF

68

VIN

ZIN = 50

FS = 100 MHz

CLK

• A low pass filter after the amplifier:– Attenuates alias images– Reduces broadband noise from the amplifier

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Anti-Alias / Noise Filter Response

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

0 10 20 30 40 50 60

Input Frequency (MHz)

Ou

tpu

t F

un

da

me

nta

l A

mp

litu

de

(d

BF

S)

ChanA

ChanB

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ADC14DS105 Dual 14-bit105 MSPS ADC

Features• Clock Duty-Cycle Stabilizer• Single 3.0V or 3.3V Power

Supply• Output Data Format

– Single or dual lane LVDS for each channel with shared Clock and Frame signals

• Serial Control Interface• Over-range Outputs• Differential Inputs• Internal Voltage Reference• 1 GHz Full Power Bandwidth• 60-pin LLP package (9mm x

9mm)

Key Performance Metrics

• Resolution: 14 bits• Conversion rate: 105 MSPS

Specifications @ Fin = 10MHz• SNR 73.0 dBFS• SFDR 88 dBFS• SINAD 72.8 dBFS

Specifications @ Fin = 240MHz• SNR 70.5 dBFS• SFDR 83 dBFS• SINAD 70.0 dBFS

• Power consumption– Normal Operation: 1W (typ)

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ADC14DS105 + LMH6552 Output Spectrum

Fin = 20 MHzFs = 100 MSPS

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ADC14DS105 KARB Performance vs. Fin

70

75

80

85

90

95

0 5 10 15 20 25 30

Input Frequency (MHz)

Ma

gn

itu

de

(d

BF

S)

SNR ChanA

SFDR ChanA

SNR ChanB

SFDR Chan B

Fs = 100 MSPS

E

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ADC14DS105KARB Near-Zero IF Receiver Reference Board

Reference Oscillator

VCXO

LMK02000

LMH6552

LMH6552

ADC14DS105

700Mbps Serial

Interface

+/- 5V Power

LMK02000 Programming

Header

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Outline



• ADC14DS105KARB


• Analog Bowl

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ADC Test Environment

Analog Signal Generator, Agilent 8644or equiv.

ADC14DS105KARB Evaluation Board

bandpass filter

WaveVision 5BoardPower

Splitter

Linear Power Supply

-5VDC +5VDC

Switching supply NOT recommended

Ensure that SPI_EN jumper is installed when using WaveVision board

The jumper setting for OF/DCS must match the data

configuration selected in WaveVision unless SPI mode

is enabled

WaveVision power switch

USB connectorSMA(f)

12 VDC power supply connector

Adapter

115 / 230 VAC

LMK02000 programming header

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ADC Test EnvironmentLive Demo

• Lab Setup

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Reference Board Setup Notes

Align ArrowsPlace JP1 on main board to provide power to PIC board

Switch 1 = OFFSwitch 2 = OFF

• The PIC board is used to program the LMK02000

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Outline



• ADC14DS105KARB


• Analog Bowl

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Which of the following is a good use of the WaveVision 5 software exclusion areas

A. B. C. D.

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Reference Design

A. Completely excluding all noise from a region of the spectrum in calculations

B. Estimating the processing gain of a digital filter

C. Removing phase noise from the SNR

D. Excluding harmonic tones from the THD

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A. 4-term Cosine windowB. 6-term Cosine windowC. 11-term Cosine windowD. They all have the same

suppression

Which windowing function gives the most sideband suppression

A. B. C. D.

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Reference Design

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A. It reduces the noise floorB. It smoothes the noise floorC. It creates a perfect power

spectral densityD. It uncovers all the

harmonics

What is a benefit of FFT averaging in the WaveVision 5 software

A. B. C. D.

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Reference Design

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A. No differenceB. The windowing function

gain in dBC. 3 dBD. 6 dB

In the WaveVision 5 software, what is the difference between the observed and calculated average noise?

A. B. C. D.

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A. Sampling clock = 100 MHzB. SNR = 67 dBC. SFDR = 82 dBD. Input signal bandwidth = 40

MHz

Which specification is not sufficient for a 3G Wireless receiver?

A. B. C. D.

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A. Harmonics are found at incorrect locations

B. Increased THDC. Increased SNRD. Increased SINAD

What is the disadvantage of setting the # of harmonics too low in the WaveVision 5 software:

A. B. C. D.

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A. The filter attenuates alias images for all input frequencies in the passband

B. The filter attenuates harmonics for all input frequencies in the passband

C. The filter reduces broadband noise from the amplifier

D. The filter reduces switching kickback from the ADC into the amplifier

Which of these is not a purpose of including a LP filter between the amplifier and ADC on the ADC14DS105KARB board?

A. B. C. D.

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A. Quantization noise from the ADC

B. Thermal noise from the ADC

C. Thermal noise from the Amplifier

D. Jitter from the clock

When the input amplitude is small (-20dBFS), the SNR performance of the ADC14DS105KARB board is limited mostly by what?

A. B. C. D.

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A. The ratio of the fundamental power [dB] to the largest spurious tone [dB]

B. The difference of the full scale power [dB] to the largest harmonic tone [dB]

C. The difference between the full scale power [dB] and the largest spurious tone [dB]

D. The difference between the fundamental power [dB] and the largest harmonic tone [dB]

In units of dBFS, the SFDR is defined as what?:

A. B. C. D.

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A. The USB interfaceB. Sample sizeC. CPU speedD. Cypress firmwareE. All of the above

What may limit the update rate for continuous capture:

A. B. C. D. E.

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Team Scores

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Documents

1 Using WaveVision 5 to Analyze the Low-IF Receiver Reference Design