QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 792A 900MHZ HIGH LINEARITY, LOW POWER DOWNCONVERTING MIXER LT5525 DESCRIPTION Demonstration circuit 792A is a high linearity, low broad range of frequencies for use in a wide variety of applications. power downconverting mixer featuring the LT5525. The RF input frequency is 900MHz, and the IF output The LT5525 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 LT5525 is a low power broadband mixer opti- LT5525 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. The RF and IF ports can be easily matched across a Table 1. Typical Performance Summary (V = 5V, EN = High, f = 1900MHz, P = -15dBm, f = 1760MHz, 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 5.3V Supply Current EN = High 28mA Maximum Shutdown Current EN = Low 100A RF to LO isolation 38dB Conversion Gain -1.9dB rd Input 3 Order Intercept 2-Tone, -15dBm/tone, Df = 1MHz 17.6dBm Single Sideband Noise Figure 15.1dB LO to RF Leakage -43dBm LO to IF Leakage -39dBm 2RF-2LO Output Spurious Product f = 1830MHz, P = -15dBm, f = 1760MHz -53dBc RF RF LO (f = f f /2) RF LO IF 3RF-3LO Output Spurious Product f = 1806.67MHz, P = -15dBm, f = 1760MHz -59dBc RF RF LO (f = f f /3) RF LO IF Input 1dB Compression +4dBm 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 792A 900MHZ HIGH LINEARITY, LOW POWER DOWNCONVERTING MIXER APPLICATION NOTE ABSOLUTE MAXIMUM INPUT RATING TEST EQUIPMENT AND SETUP Supply Voltage ..................................................... 5.5V Refer to Error Reference source not found. for Enable Voltage.................................0.3V to V +0.3V proper measurement equipment 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 792A is optimized for evaluat- termination on all ports and have good port-to-port ing the LT5525 for 1900MHz RF to 140MHz IF down- isolation should be used. Attenuators on the outputs conversion with either low-side or high- side LO in- of the signal generators are recommended to further jection. improve source isolation, to prevent the sources from The RF input port is well matched with better than modulating each other and generating intermodula- 12dB return loss over the frequency range from tion products. 1300MHz to 2300GHz. The IF output port is matched Spectrum analyzers can produce significant internal dis- for 140MHz with a 10dB return loss bandwidth of tortion products if they are overdriven. Generally, spec- 50MHz. trum analyzers are designed to operate at their best with With proper matching, the RF and IF ports can be about 30dBm to -40dBm at their input. Sufficient tuned for operation at other frequencies. Please refer spectrum analyzer input attenuation should be used to the LT5525 datasheet Applications Information to avoid saturating the instrument. section. Before performing measurements on the DUT, the The LO input is internally matched to 50W. system performance should be evaluated to ensure that: 1) a clean input signal is obtained and 2) the spectrum analyzer internal distortion is minimized. QUICK START PROCEDURE Demonstration circuit 792A is easy to set up to evalu- 3. Connect DC power supply negative (-) output to ate the performance of the LT5525. Refer to Error demo board GND pin (E2 or E4). Reference source not found. for proper measure- 4. Connect DC power supply positive (+) output (3.6V ment equipment setup and follow the procedure be- to 5.25V) to demo board Vcc pin (E1). low: NOTE: Do not exceed 5.5V, the absolute maximum 1. Connect signal generator outputs to demo board supply voltage. RFin port (SMA connector J1) and LOin port (SMA 5. Using a jumper cable, connect demo board Vcc pin connector J3) via coaxial cable. (E3) to EN pin (E1). Now the detector is enabled 2. Connect demo board IFout port (SMA connector (on) and is ready for measurement. J2) to spectrum analyzer input via coaxial cable. 2