On 02/12/2013 04:03 PM, Marcus D. Leech wrote:
>>
>> On 02/12/2013 12:10 PM, John Wilson wrote:
>>> Hi,
>>>
>>> I'm wondering whether it's possible/how to use a USRP1 with 2x DBSRX
>>> boards
>>> to generate 4 separate streams via the 4rx usrp1 firmware. The required
>>> channels will be within the front end bandwidth of the DBSRX2.
>>>
>>> At the moment I'm using a subdev spec of 'A:0 A:0 B:0 B:0' which I
>>> assume
>>> runs the signal from subdev A through RX chains 0 and 1, and subdev B
>>> through 2 and 3. Is this correct?
>> That seems correct.
>>
>>> I am planning to set each daughter board to a frequency between its two
>>> frequencies of interest, then I'd like the DDCs to downconvert the data
>>> from the ADC independently to sit the two frequencies of interest in the
>>> centre of their respective baseband channels out of the USB bus. So
>>> can I
>>> change the DDC frequencies independently of the centre frequency in the
>> You will want a tune_request object where the rf_freq is set to the
>> desired center frequency of the DBSRX (something in between that each
>> CORDIC can shift away from). And set the rf freq policy to manual.
>>
>> There are some examples of making the tune request in the grc block for
>> usrp source properties dialog box.
>>
>>> daughterboard? Also what is the resolution of the DDS in the DDC,
>>> i.e. can
>>> I tune each one independently in ~1Hz steps?
>>>
>> The CORDIC resolution is pretty much 64e6/(1<<32), so sub Hz.
>>
>>
>> -josh
>>
> Also, will he need to use the 4rx FPGA image, or will UHD automagically
> use the right image?
>
>