QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1455A 5MHZ TO 1600MHZ HIGH LINEARITY DIRECT QUADRATURE MODULATOR LTC5598 DESCRIPTION Demonstration circuit 1455A is a high linearity direct tended for DC coupling from a source with a common- quadrature modulator featuring the LTC5598. mode voltage level of about 0.5V. The LO path consists of an LO buffer with single-ended or differential inputs, The LTC 5598 is a direct I/Q modulator designed for and precision quadrature generators that produce the high performance wireless applications, including wire- LO drive for the mixers. The supply voltage range is less infrastructure. It allows direct modulation of an RF 4.5V to 5.25V, with about 165mA current. signal using differential baseband I and Q signals. It supports point-to-point microwave link, GSM, EDGE, Demonstration circuit 1455A is designed for evaluating CDMA, 700MHz band LTE, CDMA2000, CATV applica- the LTC5598 IC at frequencies from 80MHz to tions and other systems. It may also be configured as 1300MHz. With a few component changes, it can be an image reject upconverting mixer, by applying 90 easily optimized for evaluations at lower or higher fre- phase-shifted signals to the I and Q inputs. quencies. Refer to Application Note section and the LTC5598 data sheet for details. The LTC5598s I/Q baseband inputs consist of voltage- to-current converters that in turn drive double-balanced Design files for this circuit board are available. Call mixers. The outputs of these mixers are summed and the LTC factory. applied to a buffer, which converts the differential mixer , LT, LTC, and LTM are registered trademarks of Linear Technology Corp. signals to a 50 single-ended buffered RF output. The All other trademarks are the property of their respective owners. four balanced I and Q baseband input ports are in- 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1455A 5MHZ TO 1600MHZ HIGH LINEARITY DIRECT QUADRATURE MODULATOR Table 1. Typical Demo Circuit Performance Summary T = 25C V = 5V, EN = 5V BBPI, BBMI, BBPQ, BBMQ common-mode DC Voltage V = 0.5V , single-tone I and Q baseband input signal = A CC CMBB DC 100kHz CW, 0.8V , two-tone I and Q baseband input signal = 2MHz and 2.1MHz CW, 0.5V each tone, I and Q 90 shifted (lower side-band PP,DIFF PP,DIFF selection) P = 0dBm, single-ended f = f f , unless otherwise noted. LO RF LO BB PARAMETER CONDITIONS TYPICAL PERFORMANCE Supply Voltage 4.5V to 5.25V Supply Current I +I , EN = High 165mA CC1 CC2 Sleep Current I +I , EN = Low 240A CC1 CC2 Baseband Bandwidth -3dB Bandwidth > 400MHz Baseband Input Current Single-Ended -68A Baseband Input Resistance Single-Ended -7.4k Baseband DC Common-Mode Voltage Externally Applied 0.5V Baseband Amplitude Swing No Hard Clipping, Single-Ended 0.86V PP LO Input Frequency Range Standard Demo Board, S < -10dB 80MHz to 1300MHz 11, ON LO Input Power Range, Differential -10 to 20dBm LO Input Power Range, Single-Ended -10 to 12dBm RF Output Frequency Range 5 to 1600MHz f = 140MHz f = 450MHz f = 900MHz LO LO LO Conversion Voltage Gain 20 Log (V / V ) -2dB -2.1dB -2dB RF, OUT, 50 IN, DIFF, I OR Q Absolute Output Power 1V on each I and Q Inputs 2dBm 1.9dBm 2dBm PP,DIFF Output 1dB Compression 8.5dBm 8.4dBm 8.5dBm Output 2nd Order Intercept IM2 is Measured at LO 4.1MHz 74dBm 72dBm 69dBm rd Output 3 Order Intercept IM3 is Measured at LO 1.9MHz and LO 2.2MHz 27.7dBm 25.5dBm 22.9dBm RF Output Noise Floor No Baseband AC Input Signal (6MHz offset) -161.2dBm/Hz -160.9dBm/Hz -160.3dBm/Hz Image Rejection Without Image Nulling -50.4dBc -55dBc -54dBc LO Feedthrough Without LO Feedthrough Nulling -55dBm -51dBm -48dBm 2