QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 753 900MHZ HIGH LINEARITY, LOW POWER DOWNCONVERTING MIXER LT5526 DESCRIPTION Demonstration circuit 753 is a high linearity, low broad range of frequencies for use in a wide variety of applications. power downconverting mixer featuring the LT5526. The RF input frequency is 900MHz, and the IF output The LT5526 offers a high performance alternative to frequency is 140MHz. passive mixers. Unlike passive mixers which have conversion loss and require high LO drive levels, the The LT5526 is a low power broadband mixer opti- LT5526 delivers conversion gain at significantly lower mized for high linearity applications such as point-to- LO input levels and is much less sensitive to LO point data transmission, cable infrastructure, and power level variations. wireless infrastructure systems. The device includes an internally matched high speed LO amplifier driving Design files for this circuit board are available. Call a double-balanced active mixer core. An integrated the LTC factory. RF buffer amplifier provides excellent LO-RF isolation. LT is a trademark of Linear Technology Corporation The RF and IF ports can be easily matched across a Table 1. Typical Performance Summary (V = 5V, EN = High, f = 900MHz, P = -15dBm, f = 760MHz, P = -5dBm, f = CC RF RF LO LO IF 140MHz, T = 25C, unless otherwise noted. Test circuit shown in Figure 2.) A PARAMETER CONDITION VALUE Supply Voltage 3.6V to 5.25V Supply Current EN = High 28mA Maximum Shutdown Current EN = Low 100A RF to LO isolation 55dB Conversion Gain 0.6dB rd Input 3 Order Intercept 2-Tone, -15dBm/tone, Df = 1MHz 16.5dBm Single Sideband Noise Figure 11.0dB LO to RF Leakage -65dBm LO to IF Leakage -74dBm 2RF-2LO Output Spurious Product f = 830MHz, P = -15dBm, f = 760MHz -72dBc RF RF LO (f = f f /2) RF LO IF 3RF-3LO Output Spurious Product f = 806.67MHz, P = -15dBm, f = 760MHz -68dBc RF RF LO (f = f f /3) RF LO IF Input 1dB Compression 5dBm 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 753 900MHZ HIGH LINEARITY, LOW POWER DOWNCONVERTING MIXER APPLICATION NOTE ABSOLUTE MAXIMUM INPUT RATING TEST EQUIPMENT AND SETUP Supply Voltage ............................................... 5.5V Refer to Figure 1 for proper measurement equipment Enable Voltage ...........................0.3V to V +0.3V setup. CC RF Input Power ........................................ +10dBm Use high performance signal generators with low LO Input Power........................................ +10dBm harmonic output for 2-tone measurements. Other- wise, low-pass filters at the signal generator outputs should be used to suppress higher-order harmonics. FREQUENCY RANGE High quality combiners that provide broadband 50W Demonstration circuit 753 is optimized for evaluating termination on all ports and have good port-to-port the LT5526 for 900MHz RF to 140MHz IF downcon- isolation should be used. Attenuators on the outputs version with either low-side or high- side LO injec- of the signal generators are recommended to further tion. improve source isolation to prevent the sources from The RF input port is well matched with better than modulating each other and generating intermodula- 10dB return loss over the frequency range from tion products. 750MHz to 1350MHz. The IF output port is matched Spectrum analyzers can produce significant internal for 140MHz with a 10dB return loss bandwidth of distortion products if they are overdriven. Generally, 200MHz. spectrum analyzers are designed to operate at their With proper matching, the RF and IF ports can be best with about 30dBm to -40dBm at their input. tuned for operation at other frequencies. Please refer Sufficient spectrum analyzer input attenuation should to the LT5526 datasheet Applications Information be used to avoid saturating the instrument. section. Before performing measurements on the DUT, the The LO input is internally matched to 50W. External system performance should be evaluated to ensure 100pF DC blocking capacitors, C5 and C6, provide a that: 1) a clean input signal is obtained and 2) the broadband match from about 100MHz to 2.7GHz. spectrum analyzer internal distortion is minimized. The LO input match can be improved at lower fre- quencies by increasing the values of C5 and C6. QUICK START PROCEDURE Demonstration circuit 753 is easy to set up to evalu- 3. Connect DC power supply negative (-) output to ate the performance of the LT5526. Refer to Figure 1 demo board GND pin (E2 or E4). for proper measurement equipment setup and follow 4. Connect DC power supply positive (+) output (3.6V the procedure below: to 5.25V) to demo board Vcc pin (E1). 1. Connect signal generator outputs to demo board NOTE: Do not exceed 5.5V, the absolute maximum RFin port (SMA connector J1) and LOin port (SMA supply voltage. connector J3) via coaxial cable. 2. Connect demo board IFout port (SMA connector J2) to spectrum analyzer input via coaxial cable. 2