I am wondering if I have a fixed attenuator after the HMC547 switch do I need to have AC coupling caps to the attenuator? I am trying to minimize my component count and want to make sure a coupling cap is or is not required.
I have a problem with the P1dB of the switch, HMC547MS8E.
I am using the switch in a receiver operating in the frequency 2-30MHz. According to the datasheets, the switch will operate from dc-3GHz.
The input power for 1dB compression stated in the data sheets is +33dBm minimum from 0.5-3.0 GHz.
When I refer to the curve for Input P1dB Vs Vdd, the plot seems to indicate that the P1dB will be lower at lower frequencies, but the minimum should still be above +26dBm.
Now when I tested the P1dB of the switch, I can only get +16dBm at the 1dB compression point. The control voltages and supply voltages (Vdd) are +5V. The test frequency is 3MHz.
Please advise why is this so?
The power handling (power compression, IIP3) of the HMC547 are expected to degrade at frequency below 200MHz, of which is a normal behavior of the GaAs FET switches. We have not evaluated the P1dB of the HMC547LP3 below 500MHz, but I believe your measured P1dB of +16dBm at 3MHz is valid based on our experience on other switches of the same process and power handling capability.
We have a new SPDT switch, HMC1118LP3DE, in the process of product releasing. This switch will be able to handle +35.5dBm from 1MHz up to 13GHz. I've attached the link to the preliminary datasheet of this switch for your review, http://www.hittite.com/content/documents/data_sheet/hmc1118lp3de_preliminary.pdf