QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 642 HIGH LINEARITY UPCONVERTING MIXER LT5521 DESCRIPTION Demonstration circuit 642 is an upconverting mixer The IF port can be easily matched to a broad range of featuring the LT 5521. The LT 5521 is a 10MHz to frequencies for use in many different applications. 3.7GHz High Linearity Up/Downconverting Mixer Demonstration circuit 642 is designed for an RF optimized for wireless and cable infrastructure output frequency range from 1.75GHz to 2.15GHz and applications. A high-speed, internally matched LO is optimized for a 250MHz IF input frequency. amplifier drives a double-balanced mixer core, Design files for this circuit board are available. Call allowing the use of a low power, single-ended LO the LTC factory. source. LT is a registered trademark of Linear Technology Corporation. Table 1. Typical Performance Summary (T = 25C) A PARAMETER CONDITION (f = 250MHz, f =1700MHz) VALUE IF LO Supply Voltage 4.5V to 5.25V Supply Current V = 5V, EN = High 82mA CC Maximum Shutdown Current V = 5V, EN = Low 100A CC RF Frequency Range 1.75GHz to 2.15GHz IF Input Return Loss Z = 50, with external matching 15dB 0 LO Input Return Loss Z = 50 12dB 0 RF Output Return Loss Z = 50 12dB 0 LO Input Power -10dBm to 0dBm Conversion Gain P = -7dBm, P = -5dBm -0.5dB IF LO P = -5dBm SSB Noise Figure 12.5dB LO rd Input 3 Order Intercept 2-Tone, -7dBm/Tone, Df = 5MHz, P = -5dBm +24.2dBm LO nd Input 2 Order Intercept 2-Tone, -7dBm/Tone, Df = 5MHz, P = -5dBm +49dBm LO Input 1dB Compression P = -5dBm +10dBm LO LO to RF leakage P = -5dBm -42dBm LO LO to IF leakage P = -5dBm -40dBm LO 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 642 HIGH LINEARITY UPCONVERTING MIXER APPLICATION NOTE of the DC return resistors, R1, R2. Operation at a FREQUENCY RANGE lower supply current will, however, degrade linearity. Demonstration circuit 642 is optimized for an IF input frequency of 250MHz. This frequency is set by the LO TO RF LEAKAGE input IF matching components on the PCB. Other Minimum LO to RF leakage is realized when R1 & R2 values may be used to maintain best performance for are closely matched 0.1% tolerance resistors are IF frequencies ranging from 10MHz to 3GHz. recommended for this reason. Resistors with a greater tolerance (ie 1%) may be used with some degradation CURRENT CONSUMPTION of LO to RF leakage. If lower power consumption is required, the LT 5521s supply current can be reduced by increasing the value QUICK START PROCEDURE Demonstration circuit 642 is easy to set up to evaluate 5. Set the Signal Generators 2 and 3 to provide two the performance of the LT 5521. Refer to Figure 1 for -10dBm CW signals to the demo board RF input proper measurement equipment setup and follow the portone at 250MHz, and the other at 255MHz. procedure below: rd 6. To measure 3 order distortion and conversion gain, NOTE: set the Spectrum Analyzer start and stop frequencies to 1940MHz and 1965MHz, respectively. a. Use high performance signal generators with low nd rd Sufficient spectrum analyzer input attenuation harmonic output for 2 & 3 order distortion should be used to avoid distortion in the instrument. measurements. Otherwise, low-pass filters at rd the signal generator outputs should be used to 7. The 3 order intercept point is equal to (P P ) / 2 1 3 nd suppress harmonics, particularly the 2 + P , where P is the power level of the two in 1 harmonic. fundamental output tones at 1950MHz and rd 1955MHz, P is the 3 order product at 1945MHz 3 b. High quality combiners that provide a 50 ohm and 1960MHz, and P is the input power (in this in termination on all ports and have good port-to- case, -7dBm). All units are in dBm. port isolation should be used. Attenuators on the nd outputs of the signal generators are 8. To measure input 2 order distortion, set the recommended to further improve source isolation Spectrum Analyzer start and stop frequencies to and to reduce reflection into the sources. 2204MHz and 2206MHz, respectively. Sufficient spectrum analyzer input attenuation should be used 1. Connect all test equipment as shown in Figure 1. to avoid distortion in the instrument. 2. Set the DC power supplys current limit to 90mA, nd 9. The 2 order intercept point is equal to P P + P , 1 2 in and adjust output voltage to 5V. where P is the power level of the fundamental 1 nd 3. Connect Vcc to the 5V DC supply, and then connect output tone at 1950MHz, P is the 2 order product 2 EN to 5V the mixer is enabled (on). at 2205MHz, and P is the input power (in this case, in -7dBm). All units are in dBm. 4. Set Signal Generator 1 to provide a 1700MHz, -5dBm, CW signal to the demo board LO input port. 2