Hello Sir/Madam,

I am using ADL5380 eval board for same RF/LO Frequency. I have Given both the Input signals through Splitter for synchronizing the input signals. With the guidance of this forum i have bypassed the output side baluns to pass DC value and at R7x and  R6x i have populated a resistor of 500 ohms.  Do you have any data of what should be the IP, IN, QP and QN data for same Input frequency?

According to the datasheet, the impedance of single ended output is 25 ohms and oscilloscope which i am using has an impedance of 50 ohms. So do i have to  use impedance matching circuit between Eval Board and oscilloscope?

Also when i bypass the balun, the circuit becomes differential so can i terminate the port IN and QN port with 50 ohm termination?

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  • Hi David,

    I have few doubts regarding the load resistor and regarding output at I and Q SMA PORTS.

    1. What should be the exact value for load resistor at R7x and R6x? Is it 200 ohms or 500 ohms?

    2. During the test of ADL5380, what we did was through DMM we measured the output value of I and Q across R6x and R7x ( 500 ohm resistor at each R6x and R7X) but we were unable to test across SMA connectors. 

    Please correct me if we are doing anything wrong?

    How is it possible to get the outputs at SMA ports?

  • 0
    •  Analog Employees 
    on Sep 25, 2020 12:30 PM in reply to Ankita S.

    Hi Ankita,

    • Yes, that's correct, the resistor should be between 200 and 500 ohms.
    • It is possible using SMA to BNC connections to use the SMA ports, but you would neglect the grounding on these cables and connect the center pin conductor of each cable to each input of the DMM.
    • It may be easier just to use DMM test probes or solder on small wires to the resistor and then use clip leads to connect to the DMM. Since it's DC, there will be no concern regarding inductance of the cables, clip leads, etc.
    • Another possibility is to use two DMM's for the I resistor and two for the Q resistor, connecting to the SMA ports. You would then measure the absolute voltage on each baseband output and subtract the voltages: IP - IN and QP - QN. This method would give you the voltage across the resistors.

    Best Regards,


  • Ok 

    Thanks David . Will try this and if need help will get back to you.

  • Hi David,

    I integrated Adl5380 with instrumentational amplifier to obtain single ended output.

    The problem which i am facing now is

    1. Current is fluctuating from 170 mA to 200 mA.

    2. When i am switching ON the bias voltage(RF is OFF) the output across R6 shows 750mV and Output across R7 is 0v

    According to my knowledge, the voltage across R6 and R7 at condition RF= Off should be 0.

    Correct me if i am wrong.

     Thank you in advance.