DEMO MANUAL DC2391A LTC5589 700MHz to 6000MHz LOW POWER I/Q MODULATOR DESCRIPTION ABSOLUTE MAX INPUT RATINGS Supply Voltage: .....................................................+3.8V Demonstration circuit 2391A is optimized for evaluation Common Mode Level of of the LTC 5589 low power I/Q modulator up to 4.5GHz. BBPI, BBMI, BBPQ, and BBMQ: ........................... +2V For frequencies above 4.5GHz, LO matching circuit on LOL, LOC DC Voltage: .........................................50mV the DC2391A demo board can be easily modified for LOL, LOC Input Power: .....................................+20dBm improved image rejection performance. Refer to data TEMP, SDO Current Sink ....................................... 10mA sheet for additional information. The four balanced I- and Voltage on Any Pin Not Q-baseband input ports can be either AC-coupled with to Exceed ..................................0.3V to (V +0.3V) internal bias supplied, or DC-coupled from a source with CC T ....................................................................150C a common-mode voltage level of about +1.4V. The SPI JMAX Operating Temperature Range .............. 40C to 105C interface is used to set internal registers which control Storage Temperature Range ................. 65C to 150C the gain, optimum center frequency, I-offset, Q-offset and sideband suppression. In addition to the digital gain control CAUTION: This part is sensitive to electrostatic discharge with 1dB steps, there is an analog gain control, V . An CTRL (ESD). Observe proper ESD precautions when handling on-chip thermometer can be used to compensate for the the LTC5589. gain vs temperature variations using a digital gain control change. The update can either be automatically triggered, Design files for this circuit board are available at or entirely switched off. DEMO MANUAL DC2391A NOTES ON TEST EQUIPMENT AND SETUP Use a high performance baseband signal genera- the displayed average noise level (DANL). The trade- tor with differential outputs, such as the Rohde & off is increased sweep time. Schwarz SMJ100A vector signal generator or Spectrum analyzers can produce significant internal equivalent. distortion products if overdriven. Generally, spectrum The LO harmonics can degrade image rejection analyzers are designed to operate their best with severely. Third harmonic should be kept at least 6dB about 30 to 40dBm at their 1st mixer. Sufficient lower than the desired image rejection, or it should spectrum analyzer input attenuation should be used be compensated by adjusting the quadrature phase to avoid overdrive, but too much attenuation reduces balance, register 0x05. In the extreme case of nearly sensitivity and dynamic range. square wave LO drive, large offset values may be Before taking measurements, the system performance required for registers 0x04 and 0x05. should be evaluated to ensure that: 1) clean baseband Use narrow resolution bandwidth (RBW) and engage signals can be produced, 2) the LO harmonics and video averaging on the spectrum analyzer to lower phase noise are minimized for CW LO drive, 3) the spectrum analyzers internal distortion is minimized, and noise floor is satisfactory. QUICK START PROCEDURE 1. Remove the DC2391A from its protective packaging in 9. Observe the modulators RF output on the spectrum an ESD-safe working area (see Figure 1). Make sure analyzer at 2559.9MHz. Also observe the sideband jumper JP1 is installed (V = V ). suppression (aka Image Rejection) at 2560.1MHz, CTRL CC and the LO Leakage at 2560MHz. 2. Set the baseband signal generator output DC common- mode voltage to +1.4VDC, set the amplitude (V ) = 1V 10. Up to this point, the I/Q Modulator has been at default emf diff, but do not yet connect the 4 cables to the DC2391A. center frequency and gain, with no trims. To change modulator center frequency, gain, etc., connect the 3. Connect the DC power supply and increase voltage Linduino to the DC2391A with the ribbon cable pro- to +3.3V. Using a voltmeter, verify the voltage at the vided. Make sure jumper JP3 on the DC2026C is set LTC5589 V pin or JP1 is +3.3V. Adjust if necessary. CC to 3.3V. 4. Apply 3.3V to DC2391As enable input (EN).The enable 11. Run QuikEval to start the GUI associated with the I/Q voltage must never exceed the LTC5589s V supply CC modulator. voltage by 0.3V or drop below 0.3V. 12. Be sure to update the QuikEval to get latest software 5. Verify the total V supply current is approximately CC version that supports the LTC5589. LTC5589 GUI will 29mA. automatically be installed on the computer for the 6. Connect the RF output to the spectrum analyzer. first time when DC2391A is connected to Linduino DC2026C. 7. Connect the LO source to the LO input and apply a 2560MHz, 0dBm CW LO signal. 13. The turn off procedure is the reverse of the turn on procedure: Make sure V is removed before V . EN CC 8. Configure the baseband signal source to provide a single CW carrier with 100kHz offset. I- and Q-channels should be in phase-quadrature and set for lower side- band selection. dc2391af 2