Power detection for Baseband I/Q signal

Hi everyone,

I want to use HMC1030 to measure the power of baseband I and Q signal in order to calculate the power of the signal before demodulation. Does the HMC1030 can measure the power for baseband I/Q signal?

If there is other option, I really appreciate.

Regards,

Arash 

  • 0
    •  Analog Employees 
    on Sep 30, 2016 4:05 AM over 4 years ago

    Yes, you can do this but you need to be aware of a few things. I assume that you input signals to the two channels are the baseband I and Q signals that you want do demodulate. Be aware that the detector inputs present a 50 ohm load to your signal. Also, you will probably need to put capacitance on the four COF pins to enable low frequency operation. So the detectors are not measuring all the way down to dc but that's not necessarily a problem.  If you make the corner frequency low enough, you will be measuring most of the signal

  • Hi Enash. Thanks very much for your answer. I wonder if HMC1030 is suitable for zero IF application. As in the datasheet, it always define the lower frequency of 100 MHz. Is there any problem if I use this IC for the signal of zero frequency? You mentioned about COF in your answer. But if the lower frequency is as low as zero, can we just connect these pins without any capacitor? 

    In case we use this for I/Q baseband signal, we should use this chip as differential configuration. Is there any application note for differential use?

    Thank you very much!

  • 0
    •  Analog Employees 
    on Aug 28, 2017 8:04 PM over 3 years ago

    A direct dc connection from your input to the RF input pins is problematic. Firstly, you would need to dc bias your signal so that it matches the input bias level on these pins. This isn't really a good idea because internally, the chip likes to control the bias levels on these pins so that internal input offset voltages can be minimized. This is a complicated topic with interactions between the input bias levels and the internal offset control circuit.  In the AD8310 datasheet we did develop a dc-coupled application circuit. Search in the AD8310 datasheet applications section for "DC Coupled Input". A similar type circuit may work for HMC1030 but it has never been tried. To be honest, I think that the AD8310 application circuit may better meet your needs.

  • Thanks Enash for replying me soon. Unfortunately, it seems like I cannot use HMC1030 for baseband signal in zero IF structure. AD8310 is not suitable as well because it has single-ended output and the frequency range is limited to 440MHz while the application requires up to 500 MHz. Could you please recommend any chip for me in order to measure signal strength of differential baseband signal from DC to 500MHz in a direct conversion receiver? Thank you very much!