Recently I study frequency Offset estimation due to mismatch in carrier frequency from the oscillator at the receiver. I understand how this cause problem can cause a phase shift. But I also saw that this cause problem called CARRIER LEAKAGE. So I look online and I saw the following:

Certain transmitter implementations may cause leakage of the center frequency component. Such carrier Leakage can occur in some transmitter because of DC offset. This issue is seen on the receiver side as energy in the transmit center frequency

Does carrier leakage mean an increase in interference power?? I thought that carrier offset happens at receiver and not transmitter. I also saw that carrier leakage can cause increase in the Error Vector Magnitude (EVM), I can't see the relationship between carrier leakage and EVM.

Looking forward for your discussion.


1 Answer 1


I think you are confusing two different things.

  • Carrier offset is the difference between the transmitter's and the receiver's local oscillator (LO). The receiver needs to eliminate or reduce the offset if it hopes to receive data consistently. This is done by estimating the offset and adjusting the frequency of the LO.

  • Carrier leakage causes a DC offset in the receiver. Consider the receiver mixer: it has two inputs, one is the received signal, and the other is the local oscillator. In practice, the LO signal will be present at both inputs, because it is very difficult to isolate high-frequency signals in a PCB. This causes the LO to mix with itself, producing a DC term at the mixer's output.

  • $\begingroup$ I think I understand what you mean, "Local-oscillator energy can leak through the mixer stage to the antenna input and then reflect back into the mixer stage. The overall effect is that the local oscillator energy will self-mix and create a DC offset signal. " $\endgroup$
    – Henry
    Jun 9, 2015 at 0:34
  • $\begingroup$ Do you what this effect would increase the error vector magniturde? @Mbaz $\endgroup$
    – Henry
    Jun 9, 2015 at 0:35
  • $\begingroup$ I've never studied the EVM in very much detail, sorry. $\endgroup$
    – MBaz
    Jun 9, 2015 at 1:35

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