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One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 •
FEATURES
Direct conversion transmit chain
Tx radio using 5 chips
Dual AD9862 MxFE, 14-bit DAC, 128 MSPS, with
programmable full-scale current
3 GHz quadrature modulator ADL5373
2.7 GHz VGA ADL5330 with 50 dB of power control range
4 GHz fractional-N synthesizer ADF4153
3 GHz RMS power detector AD8362
Supports 10 MHz channel bandwidth with 1024-subcarriers
OFDM
Supports QPSK, 16 QAM, and 64 QAM OFDMA
Transmitter output power: 13 dBm maximum, CW
EVM 64 QAM OFDM: 1.2% @ −3 dBm output
Transmitter noise at 20 MHz offset: −142.5 dBm/Hz @ −1 dBm
Precise output rms power control
Dual-supply operation: 5 V @ 380 mA, 3.3 V @ 165 mA
APPLICATIONS
WiBro/WiMAX 5 V CPE and base stations
A 2.4 GHz WiMAX Direct Conversion Transmitter
by Cecile Masse and Qui Luu
RF VGA
ADL5330
AD8362
RMS POWER
DETECTOR
Rev. B | Page 1 of 16
APPLICATION NOTE
IQ MODULATOR
ADL5373
0°
90°
FRACTIONAL-N
SYNTHESIZER
ADF4153
Figure 1. Direct Conversion Transmitter
AN-826
www.analog.com
AD9860/AD9862
MxFE
ADC
ADC
DAC
DAC
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Table of Contents
Related Manuals for Analog Devices AN-826
Summary of Contents for Analog Devices AN-826
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Page 1: Features
AN-826 APPLICATION NOTE One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com A 2.4 GHz WiMAX Direct Conversion Transmitter by Cecile Masse and Qui Luu FEATURES Direct conversion transmit chain... -
Page 2: Table Of Contents
AN-826 TABLE OF CONTENTS Features ....................1 The VGA and the Interface to the IQ Modulator .....9 Applications ..................1 RMS Power Detection ............... 10 Introduction ..................3 Overall System Performance ............ 12 ... -
Page 3: Introduction
AD9860/AD9862 The purpose of this application note is to demonstrate the MxFE Analog Devices, Inc. WiMAX 5 V transmit signal chain for applications extending up to 2.7 GHz. As the wireless communication industry moves toward higher RF frequencies, and higher data rates through wider modula-... -
Page 4: Analog Baseband Signal Generation
AN-826 ANALOG BASEBAND SIGNAL GENERATION avoided using the interpolation filters, available within the DAC. While the input data rate to the DAC remains the same, The Tx DAC is one of the most critical components in this the interpolation filters increase the sampling frequency of the signal chain because it needs to provide the closest to ideal DACs. -
Page 5: Iq Modulator
AN-826 to be applied at the connecting point of R1 and R2 to maintain IQ MODULATOR the 500 mV of dc bias level. Note that with this lower full-scale Modulator AC Drive Level current, the ac dynamic performance of the DAC degrades by The I and Q inputs of the modulator should be driven about 2 dB. - Page 6 AN-826 Similarly, the AD9862 DACs allow dc offset correction voltages to achieve LO leakage suppression. –10 I and Q amplitude mismatch correction is achieved by current scaling. There is both a fine and coarse gain control (Register 14 –20 and Register 15) to adjust the full-scale output current of either Tx channel independently.
- Page 7 AN-826 Finding the IQ Modulator Optimum Operating Point At the first frequency offset (ACP1), as the power level drops, more backoff from the compression and third-order intercept Optimum output level for the modulator can be determined by point helps reduce the signal distortion and improve ACPR measuring the upconverted signal distortion in the frequency performance.
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Page 8: The Lo Synthesizer
AN-826 THE LO SYNTHESIZER For fast loops, spurs are less attenuated because they fall inside the loop bandwidth. In low spur mode, dither is enabled. This One local oscillator (LO) is required for this direct conversion randomizes the fractional quantization noise so it looks like architecture. -
Page 9: The Vga And The Interface To The Iq Modulator
AN-826 Lock Time Figure 14 shows the closed-loop phase noise performance of this PLL. PLL lock time can be critical in the following scenarios: The VCO is a Sirenza VCO190-2350T(Y), with a tuning sensi- • In HFDD systems where both frequency duplex and time tivity of 35 MHz/V typical. -
Page 10: Rms Power Detection
AN-826 120nH 120nH IBBP ADL5373 ADL5330 100pF 100pF IQ MOD RF VGA IBBN VOUT INLO OPHI RF OUTPUT DIFFERENTIAL I/Q BASEBAND INPUTS QBBP INHI OPLO QBBN 100pF 100pF ETC1-1-13 LOIP LOIN 100pF GAIN CONTROL LO OUTPUT 100pF ETC1-1-13 Figure 15. IQ Modulator and RF VGA Interfaces ADL5373 is designed to drive a 50 Ω... - Page 11 AN-826 Temperature Compensation Figure 17 shows the power detection error with CLPF = 1 μF To improve the measurement accuracy of the AD8362 over and VTG = 0.625 V. temperature at 2.35 GHz, a simple temperature compensation scheme can be used. It helps correct for the drift of the detector intercept point of the V = f(Pin) characteristic.
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Page 12: Overall System Performance
AN-826 The fractional-N PLL used for this reference design has a phase error due to phase noise of 0.35° and only degrades the overall system EVM by 0.2%. +85°C For these characterizations, the IQ modulator output power level was set around its optimum power level at −14 dBm. Then +85°C... -
Page 13: Typical Performance Characteristics
AN-826 TYPICAL PERFORMANCE CHARACTERISTICS VPS1 = 5 V for the ADL5373, ADL5330, and AD8362 components. VPS2 = 3.3 V for ADF4153 and AD9860/AD9862. Radio frequency band: 2.3 GHz to 2.4 GHz. –10 –20 –5 –30 –15 –40 CHANNEL EDGE @ 5.45MHz –5... - Page 14 AN-826 –1 BPSK QPSK 1/2 QPSK 3/4 –2 16QAM 3/4 64QAM 1/2 –3 –50 –40 –30 –20 –10 –60 –55 –50 –45 –40 –35 –30 –25 –20 –15 –10 –5 TRANSMITTER OUTPUT POWER LEVEL (dBm) INPUT POWER (dBm) Figure 29. RMS Power Detector Response and Detection Error vs. Tx Signal Figure 27.
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Page 15: Summary Of Measured Performance
AN-826 SUMMARY OF MEASURED PERFORMANCE VPS1 = 5 V (ADL5373, ADL5330, and AD8362). VPS2 = 3.3 V (ADF4153, AD9860/AD9862 DAC). Radio frequency band: 2.3 GHz to 2.4 GHz. Signal bandwidth = 10 MHz. QPSK, 16 QAM, and 64 QAM, 256-subcarriers OFDM modulation. -
Page 16: Bill Of Materials For Major Components
Analog Devices, Inc. EVAL-ADF4153EB1 AD8362 RMS responding power detector Analog Devices, Inc. AD8362- EVALZ ©2005–2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. AN05790-0-9/07(B) Rev. B | Page 16 of 16...
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