AD8346

300 MHz to 1000 MHz Quadrature Modulator ADL5370 FEATURES Output frequency range: 300 MHz to 1000 MHz Modulation bandwidth: >500 MHz (3 dB) 1 dB output compression: 11 dBm @ 450 MHz Noise floor: −160 dBm/Hz Sideband suppression: −41 dBc @ 450 MHz Carrier feedthrough: −50 dBm @ 450 MHz Single supply: 4.75 V to 5.25 V 24-lead LFCSP_VQ package FUNCTIONAL BLOCK DIAGRAM IBBP IBBN LOIP LOIN QUADRATURE PHASE SPLITTER VOUT QBBN QBBP 06117-001 APPLICATIONS Cellular communication systems at 450 MHz CDMA2000/GSM WiMAX/broadband wireless access systems Cable communication equipment Satellite modems Figure 1. GENERAL DESCRIPTION The ADL5370 is the first in the fixed-gain quadrature modulator (F-MOD) family designed for use from 300 MHz to 1000 MHz. Its excellent phase accuracy and amplitude balance enable high performance intermediate frequency or direct radio frequency modulation for communication systems. The ADL5370 provides a greater than 500 MHz, 3 dB baseband bandwidth, making it ideally suited for use in broadband zero IF or low IF-to-RF applications and in broadband digital predistortion transmitters. The ADL5370 accepts two differential baseband inputs and a single-ended LO and generates a single-ended 50 Ω output. The ADL5370 is fabricated using the Analog Devices, Inc. advanced silicon-germanium bipolar process. It is available in a 24-lead, exposed-paddle, Pb-free, LFCSP_VQ package. Performance is specified over a −40°C to +85°C temperature range. A Pb-free evaluation board is available. Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2006 Analog Devices, Inc. All rights reserved. ADL5370 TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 ESD Caution.................................................................................. 4 Pin Configuration and Function Descriptions............................. 5 Theory of Operation ...................................................................... 10 Circuit Description..................................................................... 10 Basic Connections .......................................................................... 11 Optimization ............................................................................... 12 Applications Information .............................................................. 13 DAC Modulator Interfacing ..................................................... 13 Limiting the AC Swing .............................................................. 13 Filtering........................................................................................ 13 Using the AD9779 Auxiliary DAC for Carrier Feedthrough Nulling ......................................................................................... 14 GSM Operation .......................................................................... 14 LO Generation Using PLLs ....................................................... 15 Evaluation Board ............................................................................ 16 Characterization Setup .................................................................. 17 Outline Dimensions ....................................................................... 19 Ordering Guide .......................................................................... 19 REVISION HISTORY 10/06—Revision 0: Initial Version Rev. 0 | Page 2 of 20 ADL5370 SPECIFICATIONS VS = 5 V; TA = 25°C; LO = 0 dBm 1 single-ended; baseband I/Q amplitude = 1.4 V p-p differential sine waves in quadrature with a 500 mV dc bias; baseband I/Q frequency (fBB) = 1 MHz, unless otherwise noted. Table 1. Parameter ADL5370 Operating Frequency Range Conditions LO = 450 MHz Range over which uncompensated sideband suppression < −30 dBc Low frequency High frequency VIQ = 1.4 V p-p differential Min Typ Max Unit Output Power Output P1 dB Carrier Feedthrough Sideband Suppression Quadrature Error I/Q Amplitude Balance Second Harmonic Third Harmonic Output IP2 Output IP3 Noise Floor GSM LO INPUTS LO Drive Level1 Input Return Loss BASEBAND INPUTS I and Q Input Bias Level Input Bias Current Input Offset Current Differential Input Impedance Bandwidth (0.1 dB) Bandwidth (1 dB) POWER SUPPLIES Voltage Supply Current 1 2 POUT − (fLO + (2 × fBB)), POUT = 6.2 dBm POUT − (fLO + (3 × fBB)), POUT = 6.2 dBm f1BB = 3.5 MHz, f2BB = 4.5 MHz, POUT = −2 dBm per tone f1BB = 3.5 MHz, f2BB = 4.5 MHz, POUT = −2 dBm per tone I/Q inputs = 0 V differential with a 500 mV common-mode bias, 20 MHz carrier offset 6 MHz carrier offset, POUT = 6 dBm, PLO = 6 dBm Characterization performed at typical level See Figure 9 for a plot of return loss vs. frequency Pin IBBP, Pin IBBN, Pin QBBP, Pin QBBN Current sourcing from each baseband input with a bias of 500 mV dc 2 −7 300 1000 6.2 11 −50 −41 0.76 0.03 −65 −54 60 24 −160 −157 0 6 500 45 0.1 2900 70 350 4.75 205 5.25 +7 MHz MHz dBm dBm dBm dBc Degrees dB dBc dBc dBm dBm dBm/Hz dBc/Hz dBm dB mV μA μA kΩ MHz MHz V mA LO = 450 MHz, baseband input = 700 mV p-p sine wave on 500 mV dc LO = 450 MHz, baseband input = 700 mV p-p sine wave on 500 mV dc Pin VPS1 and Pin VPS2 High LO drive reduces noise at a 6 MHz carrier offset in GSM applications. See V-to-I converter discussion in the Circuit Description section for architecture information. Rev. 0 | Page 3 of 20 ADL5370 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Supply Voltage VPOS IBBP, IBBN, QBBP, QBBN LOIP and LOIN Internal Power Dissipation θJA (Exposed Paddle Soldered Down) Maximum Junction Temperature Operating Temperature Range Storage Temperature Range Rating 5.5 V 0 V to 2 V 13 dBm 1375 mW 54°C/W 159°C −40°C to +85°C −65°C to +150°C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ESD CAUTION Rev. 0 | Page 4 of 20 ADL5370 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 24 23 22 21 20 19 COM1 COM1 VPS1 VPS1 VPS1 VPS1 QBBP QBBN COM4 COM4 IBBN IBBP 1 2 3 4 5 6 ADL5370 TOP VIEW (Not to Scale) 18 17 16 15 14 13 VPS5 VPS4 VPS3 VPS2 VPS2 VOUT COM2 7 LOIP 8 LOIN 9 COM2 10 COM3 11 COM3 12 Figure 2. Pin Configuration Table 3. Pin Function Descriptions Pin No. 1, 2, 7, 10 to 12, 21, 22 3 to 6, 14 to 18 Mnemonic COM1, COM2, COM3, COM4 VPS1, VPS2, VPS3, VPS4, VPS5 IBBP, IBBN, QBBN, QBBP Description Input Common Pins. Connect to ground plane via a low impedance path. Positive Supply Voltage Pins. All pins should be connected to the same supply (VS). To ensure adequate external bypassing, connect 0.1 μF capacitors between each pin and ground. Adjacent power supply pins of the same name can share one capacitor (see Figure 25). Differential In-Phase and Quadrature Baseband Inputs. These high impedance inputs must be dc-biased to 500 mV dc, and must be driven from a low impedance source. Nominal characterized ac signal swing is 700 mV p-p on each pin. This results in a differential drive of 1.4 V p-p with a 500 mV dc bias. These inputs are not self-biased and must be externally biased. 50 Ω Single-Ended Local Oscillator Input. Internally dc-biased. Pins must be ac-coupled. AC-couple LOIN to ground and drive LO through LOIP. Device Output. Single-ended, 50 Ω internally biased RF output. Pin must be ac-coupled to the load. Connect to ground plane via a low impedance path. 19, 20, 23, 24 8, 9 13 LOIP, LOIN VOUT Exposed Paddle Rev. 0 | Page 5 of 20 06117-002 ADL5370 TYPICAL PERFORMANCE CHARACTERISTICS VS = 5 V; TA = 25°C; LO = 0 dBm single-ended; baseband I/Q amplitude = 1.4 V p-p differential sine waves in quadrature with a 500 mV dc bias; baseband I/Q frequency (fBB) = 1 MHz, unless otherwise noted. 8 7 14 12 TA = –40°C TA = +25°C TA = –40°C SSB OUTPUT POWER (dBm) 6 5 4 3 2 TA = +85°C OUTPUT P1dB (dBm) 10 8 6 4 2 0 250 TA = +25°C TA = +85°C 06117-003 0 250 450 650 850 1050 1250 1450 450 650 850 1050 1250 1450 LO FREQUENCY (MHz) LO FREQUENCY (MHz) Figure 3. Single Sideband (SSB) Output Power (POUT) vs. LO Frequency (fLO) and Temperature 8 7 SSB OUTPUT POWER (dBm) 6 5 4 VS = 4.75V 3 2 06117-004 Figure 6. SSB Output 1 dB Compression Point (OP1dB) vs. fLO and Temperature 14 12 VS = 5.25V VS = 5V OUTPUT P1dB (dBm) VS = 5.25V 10 8 6 4 2 0 250 VS = 5V VS = 4.75V 0 250 450 650 850 1050 1250 1450 450 650 850 1050 1250 1450 LO FREQUENCY (MHz) LO FREQUENCY (MHz) Figure 4. Single Sideband (SSB) Output Power (POUT) vs. LO Frequency (fLO) and Supply 5 Figure 7. SSB Output 1 dB Compression Point (OP1dB) vs. fLO and Supply 90 120 60 OUTPUT POWER VARIANCE (dB) 150 1450MHz S22 OF OUTPUT 1450MHz 180 250MHz S11 OF LOIP 210 06117-035 30 0 0 330 250MHz 240 270 300 –5 BASEBAND FREQUENCY (MHz) Figure 5. I and Q Input Bandwidth Normalized to Gain @ 1 MHz (fLO = 500 MHz) Rev. 0 | Page 6 of 20 Figure 8. Smith Chart of LOIP S11 and VOUT S22 . (fLO from 250 MHz to 1450 MHz) 06117-008 1 10 100 1000 06117-007 1 06117-006 1 ADL5370 0 0 –10 SIDEBAND SUPPRESSION (dBc) –5 RETURN LOSS (dB) –20 –30 TA = +85°C TA = –40°C –10 –40 –50 –60 –70 06117-012 –15 –20 06117-009 –80 –90 250 TA = +25°C –25 250 450 650 850 1050 1250 1450 450 650 850 1050 1250 1450 LO FREQUENCY (MHz) LO FREQUENCY (MHz) Figure 9. Return Loss (S11) of LOIP Figure 12. Sideband Suppression vs. fLO and Temperature Multiple Devices Shown 0 –10 SIDEBAND SUPPRESSION (dBc) 0 –10 CARRIER FEEDTHROUGH (dBm) –20 –30 –40 –50 –60 –70 06117-010 –20 –30 –40 –50 –60 –70 TA = +25°C 450 650 850 1050 1250 06117-013 TA = –40°C TA = +85°C –80 –90 250 –80 –90 250 450 650 850 1050 1250 1450 1450 LO FREQUENCY (MHz) LO FREQUENCY (MHz) Figure 10. Carrier Feedthrough vs. fLO and Temperature Multiple Devices Shown 0 Figure 13. Sideband Suppression vs. fLO and Temperature after Nulling at 25°C Multiple Devices Shown –20 SECOND ORDER DISTORTION, THIRD ORDER DISTORTION, CARRIER FEEDTHROUGH, SIDEBAND SUPPRESSION SSB OUTPUT POWER 15 –10 CARRIER FEEDTHROUGH (dBm) –30 THIRD ORDER (dBc) 10 SSB OUTPUT POWER (dBm) 06117-014 –20 –30 –40 –50 –60 –70 06117-011 –40 CARRIER FEEDTHROUGH (dBm) 5 –50 SIDEBAND SUPPRESSION (dBc) 0 –60 –5 –70 SECOND ORDER (dBc) –10 –80 –90 250 450 650 850 1050 1250 1450 –80 0.2 0.6 1.0 1.4 1.8 2.2 2.6 3.0 –15 3.4 LO FREQUENCY (MHz) BASEBAND INPUT VOLTAGE (V p-p) Figure 11. Carrier Feedthrough vs. fLO and Temperature after Nulling at 25°C Multiple Devices Shown Figure 14. Second- and Third-Order Distortion, Carrier Feedthrough, Sideband Suppression, and SSB POUT vs. Baseband Differential Input Level (fLO = 450 MHz) Rev. 0 | Page 7 of 20 ADL5370 –20 15 30 SECOND ORDER DISTORTION, THIRD ORDER DISTORTION, CARRIER FEEDTHROUGH, SIDEBAND SUPPRESSION OUTPUT THIRD ORDER INTERCEPT (dBm) THIRD ORDER (dBc) –30 SSB OUTPUT POWER –40 CARRIER FEEDTHROUGH (dBm) 10 25 TA = +25°C TA = –40°C 5 SSB OUTPUT POWER (dBm) 20 TA = +85°C –50 SIDEBAND SUPPRESSION (dBc) 0 15 –60 SECOND ORDER (dBc) –5 10 –70 –10 06117-015 5 0 250 06117-023 –80 0.2 0.6 1.0 1.4 1.8 2.2 2.6 3.0 –15 3.4 450 650 850 1050 1250 1450 BASEBAND INPUT VOLTAGE (V p-p) LO FREQUENCY (MHz) Figure 15. Second- and Third-Order Distortion, Carrier Feedthrough, Sideband Suppression, and SSB POUT vs. Baseband Differential Input Level (fLO = 900 MHz) SECOND AND THIRD ORDER DISTORTION (dBc) Figure 18. OIP3 vs. Frequency and Temperature –20 OUTPUT SECOND ORDER INTERCEPT (dBm) 70 TA = –40°C 60 50 40 30 20 10 0 250 TA = +25°C TA = +85°C –30 –40 THIRD ORDER = +25°C –50 THIRD ORDER = +85°C THIRD ORDER = –40°C SECOND ORDER = –40°C –60 –70 –80 250 SECOND ORDER = +25°C 450 650 850 1050 1250 06117-016 1450 450 650 850 1050 1250 1450 LO FREQUENCY (Hz) LO FREQUENCY (MHz) Figure 16. Second- and Third-Order Distortion vs. fLO and Temperature (Baseband I/Q Amplitude = 1.4 V p-p differential) –20 SECOND ORDER DISTORTION, THIRD ORDER DISTORTION, CARRIER FEEDTHROUGH, SIDEBAND SUPPRESSION Figure 19. OIP2 vs. Frequency and Temperature –20 SECOND ORDER DISTORTION, THIRD ORDER DISTORTION, CARRIER FEEDTHROUGH, SIDEBAND SUPPRESSION 7 SSB OUTPUT POWER 6 SSB OUTPUT POWER (dBm) 15 10 5 CARRIER FEEDTHROUGH (dBm) THIRD ORDER (dBc) 0 –5 –10 –15 –20 06117-018 –30 –40 –50 –60 –70 SECOND ORDER (dBc) –80 –90 –30 –40 –50 –60 –70 –80 SIDEBAND SUPPRESSION (dBc) CARRIER FEEDTHROUGH (dBm) THIRD ORDER (dBc) 5 4 3 2 1 0 100 SECOND ORDER (dBc) 06117-034 1 10 BASEBAND FREQUENCY (Hz) –90 –7 –5 –3 –1 1 3 5 7 LO AMPLITUDE (dBm) Figure 17. Second- and Third-Order Distortion, Carrier Feedthrough, Sideband Suppression, and SSB POUT vs. fBB and Temperature (fLO = 450 MHz) Figure 20. Second- and Third-Order Distortion, Carrier Feedthrough, Sideband Suppression, and SSB POUT vs. LO Amplitude (fLO = 450 MHz) Rev. 0 | Page 8 of 20 SSB OUTPUT POWER (dBm) SIDEBAND SUPPRESSION (dBc) SSB OUTPUT POWER 06117-024 SECOND ORDER = +85°C ADL5370 16 FLO = 450MHz –20 15 10 14 12 SECOND ORDER DISTORTION, THIRD ORDER DISTORTION, CARRIER FEEDTHROUGH, SIDEBAND SUPPRESSION –30 SSB OUTPUT POWER –40 –50 –60 –70 –80 –90 –7 CARRIER FEEDTHROUGH (dBm) THIRD ORDER (dBc) SIDEBAND SUPPRESSION (dBc) SECOND ORDER (dBc) SSB OUTPUT POWER (dBm) 5 0 –5 –10 –15 –20 QUANTITY 10 8 6 4 2 0 06117-019 –161.4 –161.2 –161.0 –160.8 –160.6 –160.4 –160.2 –160.0 –159.8 –159.6 –159.4 –159.2 –159.0 –158.8 –5 –3 –1 1 3 5 7 NOISE (dBm/Hz) AT 20MHz OFFSET LO AMPLITUDE (dBm) Figure 21. Second- and Third-Order Distortion, Carrier Feedthrough, Sideband Suppression, and SSB POUT vs. LO Amplitude (fLO = 900 MHz) 0.23 0.22 VS = 5.25V 0.21 0.20 0.19 0.18 0.17 06117-020 Figure 23. 20 MHz Offset Noise Floor Distribution at fLO = 450 MHz (I/Q Amplitude = 0 mV p-p with 500 mV dc bias) SUPPLY CURRENT (A) VS = 5V VS = 4.75V 0.16 0.15 –40 25 TEMPERATURE (°C) 85 Figure 22. Power Supply Current vs. Temperature Rev. 0 | Page 9 of 20 –158.6 06117-036 ADL5370 THEORY OF OPERATION CIRCUIT DESCRIPTION Overview The ADL5370 can be divided into five circuit blocks: the local oscillator (LO) interface, the baseband voltage-to-current(V-to-I) converter, the mixers, the differential-to-single-ended (D-to-S) amplifier, and the bias circuit. A detailed block diagram of the device is shown in Figure 24. LOIP LOIN PHASE SPLITTER V-to-I Converter The differential baseband inputs (QBBP, QBBN, IBBN, IBBP) consist of the bases of PNP transistors, which present a high impedance. The voltages applied to these pins drive the V-to-I stage that converts baseband voltages into currents. The differential output currents of the V-to-I stages feed each of their respective Gilbert-cell mixers. The dc common-mode voltage at the baseband inputs sets the currents in the two mixer cores. Varying the baseband common-mode voltage varies the current in the mixer and affects overall modulator performance. The recommended dc voltage for the baseband common-mode voltage is 500 mV dc. Mixers IBBP IBBN Σ QBBP QBBN OUT 06117-032 Figure 24. Block Diagram The ADL5370 has two double-balanced mixers: one for the inphase channel (I channel) and one for the quadrature channel (Q channel). Both mixers are based on the Gilbert-cell design of four cross-connected transistors. The output currents from the two mixers sum together into a load. The signal developed across this load is used to drive the D-to-S amplifier. The LO interface generates two LO signals in quadrature. These signals are used to drive the mixers. The I and Q baseband input signals are converted to currents by the V-to-I stages, which then drive the two mixers. The outputs of these mixers combine to feed the differential-to-single-ended amplifier, which provides a 50 Ω output interface. The bias cell generates reference currents for the V-to-I stage and the D-to-S amplifier. D-to-S Amplifier The output D-to-S amplifier consists of a totem pole output stage. The 50 Ω output impedance is established by an on-chip resistor. The D-to-S output is internally dc-biased and should be ac-coupled at its output (VOUT). Bias Circuit An on-chip band gap reference circuit is used to generate a proportional-to-absolute temperature (PTAT) reference current for the V-to-I stage and a temperature independent current for the D-to-S output stage. LO Interface The LO interface consists of a polyphase quadrature splitter followed by a limiting amplifier. The LO input impedance is set by the polyphase. The LO can be driven either single-ended or differentially. When driven single-ended, the LOIN pin should be ac-grounded via a capacitor. Each quadrature LO signal then passes through a limiting amplifier that provides the mixer with a limited drive signal. Rev. 0 | Page 10 of 20 ADL5370 BASIC CONNECTIONS Figure 25 shows the basic connections for the ADL5370. QBBP QBBN IBBN IBBP Baseband Inputs The baseband inputs QBBP, QBBN, IBBP, and IBBN must be driven from a differential source. The nominal drive level of 1.4 V p-p differential (700 mV p-p on each pin) should be biased to a common-mode level of 500 mV dc. The dc common-mode bias level for the baseband inputs may range from 400 mV to 600 mV. This results in a reduction in the usable input ac swing range. The nominal dc bias of 500 mV allows for the largest ac swing, limited on the bottom end by the ADL5370 input range and on the top end by the output compliance range on most digital-to-analog converters (DAC) from Analog Devices. QBBN COM4 COM4 QBBP IBBN 24 23 22 21 20 19 IBBP C16 0.1µF C15 0.1µF COM1 COM1 VPS1 VPOS 1 2 3 4 5 6 18 VPS5 VPS4 VPS3 C14 0.1µF VPOS C13 0.1µF C11 OPEN VOUT 06117-033 Z1 ADL5370 17 16 LO Input A single-ended LO signal should be applied to the LOIP pin through an ac-coupling capacitor. The recommended LO drive power is 0 dBm. The LO return pin, LOIN, should be ac-coupled to ground through a low impedance path. The nominal LO drive of 0 dBm can be increased to up to 7 dBm to realize an improvement in the noise performance of the modulator. This improvement is tempered by degradation in the sideband suppression performance (see Figure 20) and, therefore, should be used judiciously. If the LO source cannot provide the 0 dBm level, then operation at a reduced power below 0 dBm is acceptable. Reduced LO drive results in slightly increased modulator noise. The effect of LO power on sideband suppression and carrier feedthrough is shown in Figure 20. The effect of LO power on GSM noise is shown in Figure 35. VPS1 VPS1 VPS1 C12 0.1µF VPS2 15 VPS2 14 EXPOSED PADDLE 13 VOUT COUT 100pF 10 LOIP COM2 LOIN COM2 COM3 GND CLOP 100pF LO CLON 100pF Figure 25. Basic Connections for the ADL5370 Power Supply and Grounding All the VPS pins must be connected to the same 5 V source. Adjacent pins of the same name can be tied together and decoupled with a 0.1 μF capacitor. These capacitors should be located as close as possible to the device. The power supply can range between 4.75 V and 5.25 V. The COM1 pin, COM2 pin, COM3 pin, and COM4 pin should be tied to the same ground plane through low impedance paths. The exposed paddle on the underside of the package should also be soldered to a low thermal and electrical impedance ground plane. If the ground plane spans multiple layers on the circuit board, they should be stitched together with nine vias under the exposed paddle. The Analog Devices AN-772 application note discusses the thermal and electrical grounding of the LFCSP_VQ in greater detail. COM3 12 11 7 8 9 RF Output The RF output is available at the VOUT pin (Pin 13). This pin must also be ac-coupled. The VOUT pin has a nominal broadband impedance of 50 Ω and does not need further external matching. Rev. 0 | Page 11 of 20 ADL5370 OPTIMIZATION The carrier feedthrough and sideband suppression performance of the ADL5370 can be improved through the use of optimization techniques. It is often desirable to perform a one-time carrier null calibration. This is usually performed at a single frequency. Figure 27 shows how carrier feedthrough varies with LO frequency over a range of ±50 MHz on either side of a null at 450 MHz. –25 –30 CARRIER FEEDTHROUGH (dBm) Carrier Feedthrough Nulling Carrier feedthrough results from minute dc offsets that occur between each of the differential baseband inputs. In an ideal modulator the quantities (VIOPP − VIOPN) and (VQOPP − VQOPN) are equal to zero, and this results in no carrier feedthrough. In a real modulator, those two quantities are nonzero; and, when mixed with the LO, they result in a finite amount of carrier feedthrough. The ADL5370 is designed to provide a minimal amount of carrier feedthrough. Should even lower carrier feedthrough levels be required, minor adjustments can be made to the (VIOPP − VIOPN) and (VQOPP − VQOPN) offsets. The I-channel offset is held constant while the Q-channel offset is varied, until a minimum carrier feedthrough level is obtained. The Q-channel offset required to achieve this minimum is held constant while the offset on the Ichannel is adjusted, until a new minimum is reached. Through two iterations of this process, the carrier feedthrough can be reduced to as low as the output noise. The ability to null is sometimes limited by the resolution of the offset adjustment. Figure 26 shows the relationship of carrier feedthrough vs. dc offset as null. –60 –64 CARRIER FEEDTHROUGH (dBm) –35 –40 –45 –50 –55 –60 –65 –70 –75 –80 –85 400 410 420 430 440 450 460 470 480 490 06117-028 500 LO FREQUENCY (MHz) Figure 27. Carrier Feedthrough vs. Frequency After Nulling at 450 MHz Sideband Suppression Optimization Sideband suppression results from relative gain and relative phase offsets between the I and Q channels and can be suppressed through adjustments to those two parameters. Figure 28 illustrates how sideband suppression is affected by the gain and phase imbalances. 0 –10 SIDEBAND SUPPRESSION (dBc) –68 –72 –76 –80 –84 –88 –300 –240 –180 –120 2.5dB –20 1.25dB –30 0.5dB 0.25dB –40 0.125dB –50 0.05dB 0.025dB –60 0.0125dB –70 0dB 06117-026 06117-027 –80 –90 0.01 –60 0 60 120 180 240 300 VP –VN OFFSET (µV) 0.1 1 PHASE ERROR (Degrees) 10 100 Figure 26. Carrier Feedthrough vs. DC Offset Voltage at 450 MHz Note that throughout the nulling process, the dc bias for the baseband inputs remains at 500 mV. When no offset is applied VIOPP = VIOPN = 500 mV, or VIOPP − VIOPN = VIOS = 0 V When an offset of +VIOS is applied to the I-channel inputs VIOPP = 500 mV + VIOS/2, and VIOPN = 500 mV − VIOS/2, such that VIOPP − VIOPN = VIOS The same applies to the Q channel. Figure 28. Sideband Suppression vs. Quadrature Phase Error for Various Quadrature Amplitude Offsets Figure 28 underlines the fact that adjusting only one parameter improves the sideband suppression only to a point, unless the other parameter is also adjusted. For example, if the amplitude offset is 0.25 dB, improving the phase imbalance better than 1° does not yield any improvement in the sideband suppression. For optimum sideband suppression, an iterative adjustment between phase and amplitude is required. The sideband suppression nulling can be performed either through adjusting the gain for each channel or through the modification of the phase and gain of the digital data coming from the digital signal processor. Rev. 0 | Page 12 of 20 ADL5370 APPLICATIONS INFORMATION DAC MODULATOR INTERFACING The ADL5370 is designed to interface with minimal components to members of the Analog Devices family of DACs. These DACs feature an output current swing from 0 to 20 mA, and the interface described in this section can be used with any DAC that has a similar output. AD9779 OUT1_P 93 RBIP 50Ω 92 RBIN 50Ω RSLI 100Ω 20 IBBN 19 ADL5370 IBBP OUT1_N Driving the ADL5370 with an Analog Devices TxDAC® An example of the interface using the AD9779 TxDAC is shown in Figure 31. The baseband inputs of the ADL5370 require a dc bias of 500 mV. The average output current on each of the outputs of the AD9779 is 10 mA. Therefore, a single 50 Ω resistor to ground from each of the DAC outputs results in an average current of 10 mA flowing through each of the resistors, thus producing the desired 500 mV dc bias for the inputs to the ADL5370. AD9779 OUT1_P 93 RBIP 50Ω 92 RBIN 50Ω 20 19 OUT2_N 84 RBQN 50Ω RBQP 50Ω 83 23 RSLQ 100Ω QBBN OUT2_P QBBP Figure 30. AC Voltage Swing Reduction Through the Introduction of a Shunt Resistor Between Differential Pair ADL5370 IBBP The value of this ac voltage swing limiting resistor is chosen based on the desired ac voltage swing. Figure 31 shows the relationship between the swing-limiting resistor and the peakto-peak ac swing that it produces when 50 Ω bias-setting resistors are used. 2.0 1.8 OUT1_N IBBN DIFFERENTIAL SWING (V p-p) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 10 100 RL (Ω) 1000 06117-025 OUT2_N 84 RBQN 50Ω RBQP 50Ω 83 23 QBBN OUT2_P QBBP Figure 29. Interface Between the AD9779 and ADL5370 with 50 Ω Resistors to Ground to Establish the 500 mV DC Bias for the ADL5370 Baseband Inputs The AD9779 output currents have a swing that ranges from 0 mA to 20 mA. With the 50 Ω resistors in place, the ac voltage swing going into the ADL5370 baseband inputs ranges from 0 V to 1 V. A full-scale sine wave out of the AD9779 can be described as a 1 V p-p single-ended (or 2 V p-p differential) sine wave with a 500 mV dc bias. 06117-029 24 10000 Figure 31. Relationship Between the AC Swing-Limiting Resistor and the Peak-to-Peak Voltage Swing with 50 Ω Bias-Setting Resistors FILTERING It is necessary to low-pass filter the DAC outputs to remove images when driving a modulator. The interface for setting up the biasing and ac swing that was discussed in the Limiting the AC Swing section lends itself well to the introduction of such a filter. The filter can be inserted between the dc bias setting resistors and the ac swing-limiting resistor. Doing so establishes the input and output impedances for the filter. An example is shown in Figure 32 with a third-order elliptical filter with a 3 dB frequency of 3 MHz. Matching input and output impedances makes the filter design easier, so the shunt resistor chosen is 100 Ω, producing an ac swing of 1 V p-p differential. LIMITING THE AC SWING There are situations in which it is desirable to reduce the ac voltage swing for a given DAC output current. This can be achieved through the addition of another resistor to the interface. This resistor is placed in shunt between each side of the differential pair, as shown in Figure 30. It has the effect of reducing the ac swing without changing the dc bias already established by the 50 Ω resistors. Rev. 0 | Page 13 of 20 06117-030 24 ADL5370 AD9779 OUT1_P 93 RBIP 50Ω RBIN 92 50Ω 1.1nF C1I LPI 2.7nH ADL5370 19 RSLI 100Ω 20 IBBN IBBP GSM OPERATION Figure 34 shows the GSM EVM and spectral mask performance vs. output power for the ADL5370 at 450 MHz. For a given LO amplitude, the performance is independent of output power. –35 250kHz EVMRMS (%) 2.0 –42 –49 –56 –63 –70 –77 –84 –91 1200kHz 600kHz 400kHz 0.5 1.1nF C2I LNI 2.7nH LNQ 2.7nH OUT1_N OUT2_N QBBN RBQN 50Ω RBQP 83 50Ω 1.1nF C1Q 1.1nF C2Q RSLQ 100Ω QBBP 06117-031 EVMPK (%) 1.0 OUT2_P 24 LPQ 2.7nH Figure 32. DAC Modulator Interface with 3 MHz Third-Order Low-Pass Filter USING THE AD9779 AUXILIARY DAC FOR CARRIER FEEDTHROUGH NULLING The AD9779 features an auxiliary DAC that can be used to inject small currents into the differential outputs for each main DAC channel. This feature can be used to produce the small offset voltages necessary to null out the carrier feedthrough from the modulator. Figure 33 shows the interface required to utilize the auxiliary DACs. This adds four resistors to the interface. AUX1_P 90 500Ω 93 RBIP 50Ω RBIN 92 50Ω 1.1nF C1I 250Ω 0 1 2 3 4 5 6 7 OUTPUT POWER (dBm) Figure 34. GSM EVM and Spectral Performance vs. Channel Power at 450 MHz vs. Output Power; LO Power = 0 dBm Figure 35 shows the GSM EVM, spectral mask performance and 6 MHz offset noise vs. LO amplitude at 450 MHz with an output power of 6 dBm. Increasing the LO drive level improves the noise performance but degrades EVM performance. –35 3.1 2.9 250kHz EVMPK (%) AD9779 OUT1_P 19 RSLI 100Ω 20 6MHz NOISE (dBc/100kHz) 250kHz, 400kHz, 600kHz AND 1200kHz SPECTRAL MASK (dBc/30kHz) LPI 2.7nH 1.1nF C2I LNI 2.7nH ADL5370 IBBP –42 –49 –56 –63 –70 –77 –84 –91 –98 EVMRMS (%) 600kHz 400kHz 2.7 2.5 2.3 2.1 1.9 1.7 1.5 1200kHz OUT1_N IBBN 250Ω AUX1_N 89 500 Ω 87 AUX2_N 500Ω OUT2_N 84 RBQN 50Ω RBQP 83 50Ω 1.1nF C1Q 250Ω 1.3 1.1 LNQ 2.7nH 23 RSLQ 100Ω 24 –105 QBBN 1.1nF C2Q –4 –2 0 2 4 6 LO AMPLITUDE (dBm) OUT2_P AUX2_P 86 500Ω 06117-041 250Ω LPQ 2.7nH QBBP Figure 35. GSM EVM, Spectral Performance, and 6 MHz Noise Floor vs. LO Power at 450 MHz; Output Power = 6 dBm Figure 33. DAC Modulator Interface with Auxiliary DAC Resistors Figure 35 illustrates that an LO amplitude of 0 dBm provides the ideal operating point for noise and EVM for a GSM signal at 450 MHz. Rev. 0 | Page 14 of 20 06117-040 –112 –6 6 MHz OFFSET NOISE 0.9 RMS AND PEAK EVM (%) 06117-039 0 RMS AND PEAK EVM (%) 84 23 250kHz, 400kHz, 600kHz, AND 1200kHz SPECTRAL MASK (dBc/30KHz) 1.5 ADL5370 LO GENERATION USING PLLS Analog Devices has a line of PLLs that can be used for generating the LO signal. Table 4 lists the PLLs together with their maximum frequency and phase noise performance. Table 4. ADI PLL Selection Table Part ADF4110 ADF4111 ADF4112 ADF4113 ADF4116 ADF4117 ADF4118 Frequency FIN (MHz) 550 1200 3000 4000 550 1200 3000 Phase Noise @ 1 kHz Offset and 200 kHz PFD (dBc/Hz) −91 @ 540 MHz −87@ 900 MHz −90 @ 900 MHz −91 @ 900 MHz −89 @ 540 MHz −87 @ 900 MHz −90 @ 900 MHz TRANSMIT DAC OPTIONS The AD9779 recommended in the previous sections of this data sheet is by no means the only DAC that can be used to drive the ADL5370. There are other appropriate DACs, depending on the level of performance required. Table 6 lists the dual Tx-DACs offered by Analog Devices. Table 6. Analog Devices Dual Tx—DAC Selection Table Part AD9709 AD9761 AD9763 AD9765 AD9767 AD9773 AD9775 AD9777 AD9776 AD9778 AD9779 Resolution (Bits) 8 10 10 12 14 12 14 16 12 14 16 Update Rate (MSPS Min) 125 40 125 125 125 160 160 160 1000 1000 1000 The ADF4360 comes as a family of chips, with nine operating frequency ranges. One is chosen, depending on the local oscillator frequency required. While the use of the integrated synthesizer may come at the expense of slightly degraded noise performance from the ADL5370, it can be a cheaper alternative to a separate PLL and VCO solution. Table 5 shows the options available. Table 5. ADF4360 Family Operating Frequencies Part ADF4360-0 ADF4360-1 ADF4360-2 ADF4360-3 ADF4360-4 ADF4360-5 ADF4360-6 ADF4360-7 ADF4360-8 Output Frequency Range (MHz) 2400 to 2725 2050 to 2450 1850 to 2150 1600 to 1950 1450 to 1750 1200 to 1400 1050 to 1250 350 to 1800 65 to 400 All DACs listed have nominal bias levels of 0.5 V and use the same simple DAC-modulator interface that is shown in Figure 31. MODULATOR/DEMODULATOR OPTIONS Table 7 lists other Analog Devices modulators and demodulators. Table 7. Modulator/Demodulator Options Part AD8345 AD8346 AD8349 ADL5390 ADL5385 ADL5371 ADL5372 ADL5373 ADL5374 AD8347 AD8348 AD8340 AD8341 Mod/Demod Mod Mod Mod Mod Mod Mod Mod Mod Mod Demod Demod Vector mod Vector mod Frequency Range (MHz) 140 to 1000 800 to 2500 700 to 2700 20 to 2400 50 to 2200 700 to 1300 1600 to 2400 2300 to 3000 3000 to 4000 800 to 2700 50 to 1000 700 to 1000 1500 to 2400 Comments External quadrature Rev. 0 | Page 15 of 20 ADL5370 EVALUATION BOARD Populated RoHS-compliant evaluation boards are available for evaluation of the ADL5370. The ADL5370 package has an exposed paddle on the underside. This exposed paddle must be soldered to the board (see the Power Supply and Grounding discussion in the Basic Connections section). The evaluation board is designed without any components on the underside so heat can be applied to the underside for easy removal and replacement of the ADL5370. QBBP QBBN IBBN IBBP RFPQ RFNQ CFNQ CFNI 0Ω 0Ω OPEN OPEN RTQ CFPQ OPEN OPEN RFNI 0Ω RTI OPEN RFPI 0Ω CFPI OPEN C16 0.1µF L12 0Ω C15 0.1µF L11 0Ω QBBN COM4 COM4 QBBP IBBN IBBP COM1 COM1 VPS1 VPS1 VPS1 VPS1 C12 0.1µF 1 2 3 4 5 6 18 VPS5 Figure 37. Evaluation Board Layout, Top Layer. VPOS VPS2 15 VPS2 14 EXPOSED PADDLE 13 VOUT COUT 100pF C13 0.1µF C11 OPEN VOUT 06117-021 10 COM2 LOIN LOIP COM2 COM3 GND CLOP 100pF LO CLON 100pF Figure 36. ADL5370 Evaluation Board Schematic Table 8. Evaluation Board Configuration Options Component VPOS, GND RFPI, RFNI, RFPQ, RFNQ, CFPI, CFNI, CFPQ, CFNQ, RTQ, RTI Description Power Supply and Ground Clip Leads. Baseband Input Filters. These components can be used to implement a low-pass filter for the baseband signals. See the Filtering discussion in the Applications Information section. Default Condition Not applicable RFNQ, RFPQ, RFNI, RFPI = 0 Ω (0402) CFNQ, CFPQ, CFNI, CFPI = Open (0402) RTQ, RTI = Open (0402) COM3 12 11 7 8 9 Rev. 0 | Page 16 of 20 VPOS Z1 ADL5370 VPS4 17 VPS3 16 C14 0.1µF 06117-022 24 23 22 21 20 19 ADL5370 CHARACTERIZATION SETUP AEROFLEX IFR 3416 250kHz TO 6GHz SIGNAL GENERATOR FREQ 4MHz LEVEL 0dBm BIAS 0.5V GAIN 0.7V BIAS 0.5V GAIN 0.7V RF OUT R AND S SPECTRUM ANALYZER FSU 20Hz TO 8GHz LO CONNECT TO BACK OF UNIT I OUT I/AM Q OUT Q/FM 90° AGILENT 34401A MULTIMETER 0.175 ADC IP VPOS +5V AGILENT E3631A POWER SUPPLY IN QP QN VPOS GND FMOD LO I Q 0° +6dBm RF IN FMOD TEST SETUP OUT OUTPUT 5.000 0.175A Figure 38. Characterization Bench Setup The primary setup used to characterize the ADL5370 is shown in Figure 38. This setup was used to evaluate the product as a single-sideband modulator. The Aeroflex signal generator supplied the local oscillator (LO) and differential I and Q baseband signals to the device under test, DUT. The typical LO drive was 0 dBm. The I channel is driven by a sine wave, and the Q channel is driven by a cosine wave. The lower sideband is the single sideband (SSB) output. The majority of characterization for the ADL5370 was performed using a 1 MHz sine wave signal with a 500 mV common-mode voltage applied to the baseband signals of the DUT. The baseband signal path was calibrated to ensure that the VIOS1 and VQOS offsets on the baseband inputs were minimized, as close as possible, to 0 V before connecting to the DUT. 1 See the Carrier Feedthrough Nulling section for the definitions of VIOS and VQOS. Rev. 0 | Page 17 of 20 06117-037 + 6V – + COM – ±25V ADL5370 TEKTRONIX AFG3252 DUAL FUNCTION ARBITRARY FUNCTION GENERATOR R AND S SMT 06 SIGNAL GENERATOR RF OUT CH1 OUTPUT CH1 1MHz AMPL 700mV p-p PHASE 0° CH2 1MHz AMPL 700mV p-p PHASE 90° 0° AGILENT E3631A POWER SUPPLY CH2 OUTPUT FREQ 4MHz TO 4GHz LEVEL 0dBm IQ 90° SINGLE TO DIFFERENTIAL CIRCUIT BOARD LO FMOD TEST RACK 5.000 0.350A Q IN AC FMOD CHAR BD GND IP IP IN QP OUT OUTPUT LO VPOS + – +5V 6V + COM – ±25V Q IN DCCM TSEN VPOSB VPOSA IN AGND IN1 IN1 VP1 QP QN +5V VPOS +5V AGILENT E3631A POWER SUPPLY –5V VN1 I IN DCCM I IN AC QN GND VPOS R AND S FSEA 30 SPECTRUM ANALYZER 0.500 0.010A RF IN 100MHz TO 4GHz +6dBm VCM = 0.5V + 6V – + COM – ±25V AGILENT 34401A MULTIMETER 0.200 ADC 06117-038 Figure 39. Setup for Baseband Frequency Sweep and Undesired Sideband Nulling The setup used to evaluate baseband frequency sweep and undesired sideband nulling of the ADL5370 is shown in Figure 39. The interface board has circuitry that converts the single-ended I and Q inputs from the arbitrary function generator to differential I and Q baseband signals with a dc bias of 500 mV. Undesired sideband nulling was achieved through an iterative process of adjusting amplitude and phase on the Q channel. See Sideband Suppression Optimization in the Optimization section for a more detailed discussion on sideband nulling. Rev. 0 | Page 18 of 20 ADL5370 OUTLINE DIMENSIONS 4.00 BSC SQ 0.60 MAX 0.60 MAX 0.50 BSC 0.50 0.40 0.30 1.00 0.85 0.80 12° MAX 0.80 MAX 0.65 TYP 19 18 EXPOSED PAD 24 1 PIN 1 INDICATOR *2.45 2.30 SQ 2.15 6 PIN 1 INDICATOR TOP VIEW 3.75 BSC SQ (BO TTOMVIEW) 13 12 7 0.23 MIN 2.50 REF 0.05 MAX 0.02 NOM 0.20 REF COPLANARITY 0.08 SEATING PLANE 0.30 0.23 0.18 *COMPLIANT TO JEDEC STANDARDS MO-220-VGGD-2 EXCEPT FOR EXPOSED PAD DIMENSION Figure 40. 24-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 4 mm × 4 mm Body, Very Thin Quad (CP-24-2) Dimensions shown in millimeters ORDERING GUIDE Model ADL5370ACPZ-R21 ADL5370ACPZ-R7 1 ADL5370ACPZ-WP1 ADL5370-EVALZ1 1 Temperature Range –40°C to +85°C –40°C to +85°C –40°C to +85°C Package Description 24-Lead LFCSP_VQ, 7” Tape and Reel 24-Lead LFCSP_VQ, 7” Tape and Reel 24-Lead LFCSP_VQ, Waffle Pack Evaluation Board Package Option CP-24-2 CP-24-2 CP-24-2 Ordering Quantity 250 1,500 64 Z = Pb-free part. Rev. 0 | Page 19 of 20 ADL5370 NOTES ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06117-0-10/06(0) Rev. 0 | Page 20 of 20