Re: [Discuss-gnuradio] Is a unipolar signal bad as an input for a USRP receiver?

[Marcus Müller]

Hi Jeon,

What I concern is, USRP can process bipolar signal, has a low noise amplifier (LNA) and an ADC at the receiving end.

That's not true. The USRP motherboard itself doesn't have an amplifier; amplifiers are, if they exist, on the daughterboards.
The LFRX doesn't have an LNA -- it just has an OpAmp configured as a voltage follower.

I've heard that LNA and ADC take a heavy stress if they process a unipolar, a DC biased signal

The ADC doesn't mind static signals (in fact, signals are always presented to the ADC as differential), and the OpAmp is speced to withstand any signal within its input range. So you don't have to worry :)

NRZ might be a good idea for other reasons, but these depend solely on your application.

Best regards,
Marcus

PS: I'll try to locate your thread on usrp-users. Normally we strive to not miss anything on that mailing list.

On 07/02/2015 05:03 PM, Jeon wrote:

I am using LFTX and LFRX to transmit and receive data between two nodes.

I am modulating a bit stream with on-off keying (OOK) in which bit 1 is modulated into HIGH voltage and bit 0 is modulated into LOW voltage close to zero.

What I concern is, USRP can process bipolar signal, has a low noise amplifier (LNA) and an ADC at the receiving end. I've heard that LNA and ADC take a heavy stress if they process a unipolar, a DC biased signal.I want the statement to be clear. I have a particular condition that I can't make a transmitted signal a bipolar NRZ signal instead of OOK...

PS. I make a thread in discuss-gnuradio since I've got no reply on USRP-users several days or weeks ago (I don't remember exactly...).

Regards,

Jeon.

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