Texas Instruments TRF370315 User manual

TRF3703 Quadrature Modulator EvaluationModule
User's Guide
Literature Number: SLWU042BOctober 2006 – Revised August 2008

2 SLWU042B – October 2006 – Revised August 2008Submit Documentation Feedback

Contents
1 Overview ............................................................................................................................ 51.1 Purpose..................................................................................................................... 51.2 EVM Circuit Overview .................................................................................................... 51.3 Power Requirements ..................................................................................................... 51.4 TRF3703 EVM Operating Procedure ................................................................................... 62 Physical Description ........................................................................................................... 112.1 PCB Layout ............................................................................................................... 112.2 Parts List .................................................................................................................. 183 Circuit Description .............................................................................................................. 183.1 Circuit Function .......................................................................................................... 184 Circuit Board ..................................................................................................................... 195 Schematic ......................................................................................................................... 20
Important Notices ............................................................................................................... 21
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List of Figures
1 Un-Optimized Sideband Suppression ..................................................................................... 72 Optimized Sideband Suppression ......................................................................................... 83 GSM EDGE EVM at 1800 MHz ............................................................................................ 94 1.5-V Interface Network for 19.2 mA Full Scale ........................................................................ 105 3.3-V Interface Network for 19.2 mA Full Scale ........................................................................ 106 Top Layer .................................................................................................................... 117 Top Layer–NH .............................................................................................................. 128 Ground Plane L2 ........................................................................................................... 139 Ground Plane L3 ........................................................................................................... 1410 Layer 4—Bottom Layer .................................................................................................... 1511 Layer 4—Bottom Layer–NH............................................................................................... 1612 Drill Pattern .................................................................................................................. 1713 Silkscreen Top Layer ...................................................................................................... 1914 TRF3703 EVM Schematic ................................................................................................ 20
List of Tables
1 Bill of Materials for TRF3703 EVM ....................................................................................... 182 Power Supply J1 ........................................................................................................... 18
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1 Overview
1.1 Purpose
1.2 EVM Circuit Overview
1.3 Power Requirements
User's GuideSLWU042B – October 2006 – Revised August 2008
TRF3703 Quadrature Modulator Evaluation Module
This document relates to the TRF3703-33 and TRF3703-15 (hereinafter referred to as TRF3703) directquadrature modulator for applications in the transmit path of base stations and communicationsequipment. The TRF3703 operates between 400 MHz and 4 GHz. The quadrature modulator is used forupconversion of signals from the transmit chain DAC to the RF power amplifier device. Evaluatingmodulator complex performance involves careful bias-voltage setup, an LO signal, and two differential(I/Q) signals at the input of the modulator. This document describes the wide range of test optionsavailable and the factors that must be considered in using this EVM.
The TRF3703 evaluation module (EVM) is intended for the evaluation of the TRF3703-33 andTRF3703-15 direct-launch quadrature modulators. Unless otherwise stated, the functionality described inthis manual applies to both the TRF3703-33 and TRF3703-15 devices.
The EVM comes configured for differential I/Q input signals via four SMA connectors as shown in theschematic, Figure 14 , and in Table 1 .
For the upper sideband, the I signals are connected to J4 (I+) and J3 (I–). The Q signals are connected toJ5 (Q–) and J6 (Q+). The LO signal is fed to SAM connector J1, whereas J2 must be terminated with 50 Ωto ground. SMA connector J7 is used to monitor the RF output signal from the quadrature modulator (U1).
The quadrature modulator requires a supply voltage of 4.5 V–5.5V at 235 mA from a regulated powersupply through headers W1 and W2. The TRF3703-33 requires a 235-mA current limit, whereas theTRF3703-15 requires 205 mA.
The TRF3703-33 and TRF3703-15 quadrature modulators require a dc common-mode bias voltage (3.3VDC and 1.5 VDC, respectively) on all four input pins.
The TRF3703 EVM requires two 5-V V
CC
dc power-supply connectors through headers W1 and W2.Header W1 supplies 5 V to the LO circuitry, and W2 supplies 5 V to the modulator circuitry.
CAUTION
Voltage Limits
Exceeding 5.6 V may damage the TRF3703.
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1.4 TRF3703 EVM Operating Procedure
1.4.1 Typical Test Results
1.4.1.1 Un-Optimized Sideband Suppression
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Set up the EVM as follows:1. Power-supply connection:a. Switch on the V
CC
(5-V) supply and set the current limit set to 235 mA.b. Connect the 5-V supply to headers W1 and W2.c. Verify that the current drawn is approximately ≤205 mA for the TRF3703-15 and ≤235 mA for theTRF3703-33.
2. Use a suitable 50- Ωoutput signal generator (LO = ±5 dBm) or the TRF3761 to supply the LO signal atdesired frequency to J1, and terminate J2 with 50 Ωto ground.3. Use a DAC or an arbitrary waveform generator to provide the I/Q input signals. A typical setup is asfollows: a 1-Vp-p sine wave, a frequency of 50 KHz, a dc-offset of 0 V, and an output impedance of50 Ω(typically an ESG vector signal generator or similar).4. Set the common mode on the ESG to either 1.65 V or 0.75 V, depending on device type (set to 1.65 Vfor the TRF3703-33, set to 0.75 V for the TRF3703-15).5. Use an arbitrary waveform generator to suppress the sideband. Adjust the I/Q amplitude and phase ofthe CW signal coming from the arbitrary waveform generator.6. Connect a spectrum analyzer to the SMA connector marked RFOUT (J7) and monitor the TRF3703output.
measures the amount by which the unwanted sideband of the input signal is attenuated in the output ofthe modulator, relative to the wanted sideband. This assumes that the baseband inputs delivered to themodulator input pins are perfectly matched in amplitude and are exactly 90 °out of phase. Un-optimizedsideband suppression is measured in dBc. An iterative test is required in order to match perfectly theinputs to the modulator. This ensures that any equipment, board, or signal conditioning componentimbalances are corrected before the signals are applied to the device under test. Once the basebandinputs to the modulator are balanced, the amount of suppression attained is a measure of the internalmismatches of the modulator, inherent to any modulator design. This suppression is the one specified inthe TRF3703 datasheet. See Figure 1 .
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C003
1.4.1.2 Optimized Sideband Suppression
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Figure 1. Un-Optimized Sideband Suppression
There are two ways to change the sideband suppression of the TRF3703. One is the amplitude betweenthe four inputs, and the second is the phase of the four inputs. The ideal condition is when all four inputs(I, I, Q, and Q) have exactly the same amplitude and the phase relationship is: I = 0 °, I = 180 °, Q = 90 °,and Q = 270 °. Also, the optimization of the sideband is controlled by the amplitude and phase of the I andQ signals, which are controlled with the gain settings of the DAC. This is an iterative procedure that resultsin optimized suppression levels that exceeds 60 dBc. The level of suppression observed depends on theamount of resolution available from the DAC driving the modulator. By using TI’s DAC568X, the user cantake advantage of built-in features (DAC fine gain) to optimize the sideband suppression by changing theamplitude relationship of the signals. If another DAC is used, then the user must provide this level ofadjustment by controlling the regular digital inputs to the DAC. See Figure 2 .
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C002
1.4.1.3 Carrier Feedthrough
1.4.1.4 GSM (EDGE EVM Measurements)
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Figure 2. Optimized Sideband Suppression
Carrier feedthrough is the amount of the LO that leaks onto the output spectrum of the modulator. Ideallyfor the TRF3703, inputs (I, I, Q, and Q) must be at approximately 3.3 V for TRF3703-33 and 1.5 V forTRF3703-15. The DAC dc settings are also useful to correct the dc mismatch between I and I andbetween Q and Q to correct for the LO feedthrough. If using TI's DAC568X, then the internal controls forthe IQ offsets provide excellent carrier suppression (very low LO leakage). Alternatively, if an ESG isbeing used, adjust the I and Q voltage offsets in mV steps until you obtain the minimum carrierfeedthrough. A typical carrier feedthrough value exceeds 50 dBm. See Figure 2 .
1. Provide a GSM edge signal of the desired frequency into the differential baseband inputs (examplesample rate = 4.33 MHz).2. Use a spectrum analyzer with edge personality to measure the transmit power to either 0 or –5 dBm.3. PSA: Mode →GSM(w/ EDGE) →measure →Transmit Pwr(usually 0 or –5 dBm) →more →EDGEEVM.
4. ESG: Mode setup →select waveform →highlight EDGE →select waveform →ARB setup →type4.33333 MHz →I/Q →I/Q output control →Common mode I/Q offset →(set to either 1.65 V forTRF3703-33 or to 0.75 V for TRF3703-15) →I/Q →I/Q output control →I/Q output atten (adjust to getdesired transmit power to either 0 or –5 dBm).See Figure 3 .
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C001
1.4.2 Interface to TI's DAC
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Figure 3. GSM EDGE EVM at 1800 MHz
Both the TRF3703-33 and the TRF3703-15 work well with TI's DACs. The TRF3703-33 is well suited towork with TI's DAC568X family, and the TRF3703-15 is well suited to work with TI's DAC56X2 series.Each DAC series is optimized to work at certain common-mode voltage. The DAC568X has acommon-mode of 3.3 V, while the DAC56X2 has a 0.7-V common-mode voltage. Figure 1 shows aninterface network to interface both DAC series to the TRF3703.
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DAC56x2 TRF3703-15
I I
Q
S0225-01
Q
II
QQ
R2
R2
R2
R2
5 V
5 V
R1
R1
R3
R3
R1
R1
R3
R3
DAC568x TRF3703-33
I I
S0226-01
II
R5
R5
5 V
5 V
R6
R1
R1
R3
R3
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TYPICAL VALUES
R1 R2 R3
53 Ω210 Ω931 Ω
NOTE: A DAC interface calculator is available (SLWC083 ).
Figure 4. 1.5-V Interface Network for 19.2 mA Full Scale
LOSS 1 dB 2 dB 3 dB 4 dB 5 dB
Pullup R1 115 115 115 115 115Pulldown R3 634 634 634 634 634Series R5 11 21 30 37.4 45.3Shunt R6 187 165 147 130 118
Figure 5. 3.3-V Interface Network for 19.2 mA Full Scale
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