Difference between LO Frequency , RF Frequency, Carrier Frequency

[Amib]

Hello,

I am doing an internship about frequency synchronization. However, I am finding it difficult to understand the difference between:

1. Local Oscillator (LO) Frequency.
2. RF frequency.
3. Carrier frequency.

I have read that the LO generates the carrier signal, so is the Carrier frequency the same as the LO Frequency?

Or is the RF frequency the same as the Carrier Frequency?

Please enlighten me on this subject, as I feel that it is not difficult. 

Any reply is appreciated, thank you!!

[Amib]

Anyone help please?

Any reply could make me understand a lot.

Thanks!!

[psisterhen]

The Local Oscillator (LO) generates the frequency tone used to mix a baseband (or intermediate frequency (IF)) up to the RF (or Passband) Frequency... or mix the RF/Passband signal down to Baseband/IF.

The Carrier Frequency, as used in the NI-USRP API, is the LO Frequency + Digital Frequency Offset.

For example, let's say you have a baseband signal, 1 MHz wide, centered at 0 Hz.  You can set the Carrier Frequency to 2 GHz and the LO Frequency to 1.995 GHz.  This will apple a 5 MHz digital frequency shift, which shifts the signal up to be centered at 5 MHz.  Then the mixer shifts the signal up another 1.995 GHz, so your RF signal is centered at 2 GHz (even though the LO is 1.995 GHz - 5 MHz below your Carrier Frequency).

RF Frequency is sometimes used interchangeably with Carrier Frequency or Center Frequency (if the Center Frequency is in the RF range).