As a disclaimer, sorry if this question seems "weird" or very basic to some fo you but just consider that I pretty new to DSP and radio stuff
What kind of application may require to feed a precision clock reference input (Rubidium, GPS) in the bladeRF?
I saw on the forum a (very interesting) subject about ground station and telemetry (DGSN if I remember correctly) and I know that the list may be pretty huge...
I also know that most of the time, for dealing with day to day RF signals from commercial devices I won't need such precision reference and that's why I am interested on the corner cases where it starts to be problematic to only rely on the internal clock. For example, is it required for GSM/GPRS/3G/LTE?
That's a good question. Recently someone had wanted to track the beacon from the ISEE-3 satellite. Since it is a beacon, it is a single carrier. Moreover, they wanted to watch the Doppler shift of the satellite. When doing an experiment like this, they wanted to only look at 200Hz worth of spectrum at a time. When you want to look at very narrow bandwidths from very high frequencies, then using a precision LO is basically required such that your signal of interest (way up at RF) doesn't appear out of band.
To have this make a little more sense, lets look at an example. Our VCTCXO is 38.4MHz with a 1.0ppm tolerance over temperature meaning it can be off by as much as 38.4Hz. When using a PLL, it will take this reference clock, and multiply it to get a signal of interest - lets say 2GHz. In this case, it would multiply the output of the VCTCXO by around 58. Up at 2GHz, 1ppm is 2000Hz - around 10x the overall bandwidth of the narrow 200Hz spectrum they wanted to view.
In general, synchronization and frequency offset error is inherent in many systems - but sometimes having a really good oscillator makes life a lot easier.
On a related note, we're still committed to getting a 1pps and 10MHz reference into the board and able to lock onto it.
Most of the time, that kind of accuracy constraint seems to be related to communication with space (probes, satellites, etc.), right?
Back on earth, is there an application that may require such clock?
Again, sorry if that seems silly. I am basically trying to figure out if it may be relevant, regarding the expected usages I have for my bladeRF, to get a hand into such clock. Because they don't tend to be cheap
Hi, after reading this thread, I would like to ask.
1. What is the way to get bladeRF to be driven by an external clock, bypass the VCTCXO and input the clock via the CLK connector
2. What frequency must be set at the CLK connector if this is possible? I have options to generate 10MHz, 38.4MHz and 40MHz.
The Cyclone IV FPGA has a 1PPS input for time synchronization. Where must I connect the GPSDO/1pps line physically?
Is there a timestamp to mark 1PPS signal?
Assuming bladedRF is running with a host, how can I use libbladeRF to read the timestamp of the 1PPS?
