I have the HMC311SC70 RF Gain block on a number of custom made radar boards. These gain blocks are on the receiver path and RF generation path, both leading into a IQ mixer (HMC525LC4). Of recent, I discovered that about 3 of these boards will not pick up reflected signals- this I observed in ADC/data acquisition and confirmed using an oscilloscope.
To troubleshoot, I inject a -30dBm 5.9GHz signal into the RX path, and tried to measure output of all components on the path (LNA- RF Amp). Detected power at input port was about -45dBm, LNA output was about -23dBm and Gain block output (the HMC311) was about -44dBm.
On comparing with a 'working' board of same design, power detected at RX port was -45dBm, LNA output was -27dBm and Gain block output was -7dBm.
Could it then be that my RF amplifier is broken? Or am I missing something else? I am seeking advice/tips before I swap out the on board RF amps.
Looking forward to reading from you. Thanks in advance.
Is it possible to share a schematic of the circuit around HMC311SC70? This way I can better assist you. If not possible can you tell me if you are using the application circuit on the datasheet?
I would try to bias HMC311SC70 with an external DC voltage and verify voltage and current going into the device. HMC311SC70 should draw about 55mA with 5V at Vs shown in the schematic below. I would also check the solder connection on the device pins and check input output DC blocking capacitors (C1 & C2).
hi David,I hope you get this message after a very long time.I did not get your last response until now- possibly because I shelved the project and started revisiting it again early this year.
Sadly my complaint in the first post still persist, and as you can see in the attached schematic sheet, I followed the suggested designs from the data sheets of the respective devices to make the circuit board.
I am still not certain about which of the blocks (LNA or Gain or IQ mixer) is not working correctly. But my recent check this evening shows that I can not detect (monitored on a Oscilloscope) any baseband signals on the output of the IQ MIxer at the testpoints (TPT) as shown in the schematic attached.I am certain that LO and RF input has the right RF signals. This I verified by connecting another port of my oscilloscope to the amplifying circuit after the IQ mixer. With varying levels of RF input power, there is corresponding varying levels of baseband signal amplitude at the amplifier output. Sadly, it was not possible to detect any baseband output from the IQ mixer.Question is: why is it impossible to measure any signal at the IQ mixer output? I would expect some measurements on my oscilloscope at these outputs and corresponding amplified signals at the output of the amplifier.