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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?

  • Hi Ankita,

    • I responded to the other forum thread with some additional guidance for akshay92; please review.
    • You should connect the 500 ohm differential load impedance in place of R7x and R6x. No additional terminations are needed.
    • Also, be careful connecting the baseband outputs into a 50 ohm oscilloscope, because DC voltage will be present. Depending upon oscilloscope, you could exceed the maximum input limit. It's best to observe the baseband outputs with high impedance probes or a DMM, since it's a DC voltage.
    • For the LO/RF signals there will be no issue using 50 ohm impedance test equipment or oscilloscope with 50 ohm input setting.

    Best Regards,


  • Thank you Sir for the quick response.

    I have a doubt regarding outputs. When i am connecting the Ip and Qp to the oscilloscope ports and when i am switching ON the 5V supply only, the output voltage obtained is Ip = 1.7V and Qp= 1.84v. Can you explain me what exactly is this output??

  • Hello Sir,

    By testing the ADL5380 board individually, When i am switching ON the  DC supply and RF/LO is OFF, the Voltage across load resistor is 1.4V at I and Q.

    and when i am switching ON the RF/LO there is no change in the voltage across load resistor.

    As you suggested, i checked the voltage across each capacitor which seems to be 2v across C1,C13 ; C6,C3,C7,C8, C11, C9- 5V AND C4, C14 - 0.4V 

    Idle current of the device is 256mA.

    I am not able to understand why still there is a voltage across load resistor when i am turning ON the supply.

  • Also after 2 hours the idle current of the board is displaying 160 mA 

  • Sir,  what should be the Rf and Lo power range if my operating frequency is 5.81 Ghz? 

  • Hi Ankita,

    It seems as though the chip may be damaged because supply current has changed drastically and you are not getting good results.

    To proceed, my recommendation would be the following:

    1. Obtain a new evaluation board.
    2. Markup the attached schematic with your intended changes and post here for review.
    3. Also, post your intended measurement setup for review.
    4. If you perform voltage checks on the evaluation board, please markup the various points on the schematic for review.





  • Ok sir. But what could be the reason for the damage sir? Actually i was experiencing a severe shock on output ports but then i turned off the device immediately. And after an hour when i turned on the device the current was 160 mA 

  • I'm not sure how the damage occurred. It's just a hypothesis, but earlier in your testing, I believe you had connected an oscilloscope with 50 ohm impedance to the baseband ports, and this may have over stressed the baseband output transistors.

    If you receive a shock while touching an evaluation board, you should check all your supply connections and voltages and to be sure there is no elevated voltages, ground loops, or floating ground connections. Also, be sure to wear an ESD wrist strap protection when working with this device.

  • Ok sir

    Thank you so much sir

    Sir, since my requirement is single ended I and Q 50 ohm outputs each at Lo/Rf freq 5.81 Ghz for phase detection 

    can i use HMC8193 IQ mixer for phase detection as an IQ DEMODULATOR?Below i am attaching a link of the module for your reference?

  • Hi Ankita,

    The HMC8193 could potentially be used for DC output applications. A few things to note, 1) it is a passive mixer, which would require a large LO drive level of +18dBm; and 2) the output ports must not exceed 6mA sourcing or sink current.

    What is driving the requirement for 50 ohm transmission line impedance? When comparing phase between two signals of the same frequency, the output is a DC voltage, which would normally not precipitate requiring a 50 ohm transmission line impedance.

    Best Regards,


  • Thank you sir for your valuable response.

    A 5.81Ghz oscillator drives an output power of 10 dbm of 50 ohm impedance and this power will be given to the splitter and one output of the splitter with power around 8 dbm will be given to LO of IQ demodulator and other output of splitter to transmitting antenna.

    At the receiver Antenna, the power obtained will be given to the RF port of I Q Demodulator.

    So i need 50 ohm impedance at input side

    and since the output will be DC i thing impedance will not matter.

    so if i  use amplifier then i can drive LO and use HMC8193?

    Correct me if i am wrong?

  • Hi Ankita,

    That's correct. For the input signals (RF and LO) you would use 50 ohms, and the baseband output would be high impedance.

    You could use an amplifier for the LO if you decide to go with the HMC8193.

    Best Regards,


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