QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1545A-X 400MHZ TO 2.7GHZ HIGH LINEARITY UPCONVERTING MIXER LT5578 DESCRIPTION Demonstration circuit 1545A-x is a high linearity up- The DC1545A-x series of demonstration circuits are converting mixer featuring the LT5578. designed for evaluating the LT5578 IC at several com- mon frequency ranges: The LT 5578 is a high performance upconverting mixer IC optimized for output frequencies in the 400MHz to VERSION APPLICATION IF INPUT LO INPUT RF OUTPUT 2.7GHz range. It features single-ended LO input and RF -A PCS 240MHz High-side 1950MHz output ports to simplify board layout and to reduce sys- -B GSM 140MHz Low-side 900MHz tem cost. The LT5578 offers a superior alternative to passive mix- Demonstration circuit 1545A-x can be easily optimized ers. Unlike passive mixers which have conversion loss for operations at other frequencies. Refer to the Appli- and require high LO drive levels, the LT5578 delivers cation Note section and the LT5578 data sheet for de- conversion gain at significantly lower LO input levels tails. and is less sensitive to LO power level variations. Only Design files for this circuit board are available. Call -1dBm of LO power is needed, and the balanced design the LTC factory. results in low LO signal leakage to the RF output. The , LT, LTC, and LTM are registered trademarks of Linear Technology Corp. lower LO drive level requirements, combined with the All other trademarks are the property of their respective owners. excellent LO leakage performance, translate into lower LO signal contamination of the output signal. Table 1. Typical Demo Circuit Performance Summary (T = 25C, V = 3.3V, P = -5dBm (-5dBm/tone for 2-tone tests, f = 1MHz), A CC IF P = -1dBm, unless otherwise noted. Low side LO for 900MHz. High side LO for 1950MHz.) LO PARAMETER CONDITIONS TYPICAL PERFORMANCE Operating Supply Voltage 3.1V to 3.5V Supply Current V = 3.3V, LO applied 152mA CC 1545A-A 1545A-B PCS (RF = 1950MHz) GSM (RF = 900MHz) IF Input Frequency Range 12dB Return Loss, LO applied 175 to 295MHz 98 to 187MHz LO Input Frequency Range 10dB Return Loss 1450MHz to >3GHz 656MHz to 866MHz LO Input Power -5 to +2dBm -5 to +2dBm RF Output Frequency Range 12dB Return Loss, LO applied 1733 to 2142MHz 830 to 967MHz Conversion Gain -0.7dB 1.4dB Conversion Gain vs. Temperature T = -40C to 85C -0.021dB/C -0.018dB/C A Output 3rd Order Intercept 24.3dBm 27.0dBm Output 2nd Order Intercept LO2IF 58dBm 52dBm Single Sideband Noise Figure 10.5dB 8.6dB Output Noise Floor P = -5dBm -158dBm/Hz -160.5dBm/Hz OUT Output 1dB Compression 10dBm 12dBm IF to LO Isolation 60dB 75dB LO to IF Leakage -22dBm -40dBm LO to RF Leakage -46dBm -43dBm 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1545A-X 400MHZ TO 2.7GHZ HIGH LINEARITY UPCONVERTING MIXER APPLICATION NOTE 3. The 70 microstrip transmission line TL1 and TL2 ABSOLUTE MAXIMUM RATINGS provide inductances required for matching. At lower Supply Voltage ......................................................4V frequencies, external inductors are necessary. LO Input Power ..............................................10dBm 4. R1 and R2 (13.7) set the DC current in the mixer LO Input DC Current .........................................30mA core to the optimum level of 40mA per side. They RF Output DC Current.......................................45mA should be well matched for best LO leakage perform- IF Input Power (Differential) ...........................18dBm + - ance. 0.1% tolerance is recommended. IF , IF DC Currents ..........................................45mA T .............................................................. 150C JMAX 5. L1 and L2 reduce the loading effect of R1 and R2. Operating Temperature Range .............-40C to 85C Their impedances should be at least several times Storage Temperature Range .............. -65C to 150C greater than the IF input impedance at the desired IF frequency. The inductors self-resonant frequency should be at least several times the IF frequency. IF INPUT INTERFACE High quality wire-wound type inductors are recom- The standard demonstration circuit 1545A-x can be re- mended. The DC resistances of L1 and L2 need to be configured for other IF input frequencies. The details of accounted for in the selection of R1 and R2. the matching circuit are omitted in this guide, since the LT5578 datasheet presents in depth explanations and 0 the ICs IF input differential impedance. Matching com- ponent values for several common IF input frequencies -5 are listed in Table 2 and their return losses are plotted in Figure 1. Refer to the demonstration circuit schematic in Figure 7. -10 Table 2. IF Input Component Values -15 (1) (2) MATCH BW IF Freq. C1, C2 C9 C3 TL1, (3) TL2 (at 12dB RL) (MHz) (pF) (pF) (pF) -20 70 560 82 - 3.3nH 50-215 b 140 Z =70 98-187 220 39 - 0 -25 240 Z =70 175-295 82 33 4.7 0 a c -30 NOTE: 50 100 150 200 250 300 350 FREQUENCY (MHz) 1. Center of C9 is 3mm from the edge of the IC package for all cases. Figure 1. IF Input Return Loss with 70MHz (a), 140MHz (b), 2. C3 is a small-valued capacitor used to improve the and 240MHz (c) matching LO-RF leakage in some applications, and it has little effect on impedance matching. C3s value and loca- tion depend on IF, LO, and RF frequencies and are determined experimentally. In certain instances, two common-mode capacitors to ground instead of one single differential capacitor may provide better leak- age suppression. 2 RETURN LOSS (dB)