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#1 2018-Feb-21 06:43:36

fc
Member
Registered: 2016-Oct-14
Posts: 21

connect an external oscillator

Hi,
I am a newer, our goal is that can we control CPU to shield the oscillator's signal produced by Y1, and we connect an external oscillator to replace it.
But now, we have some questions:
(1) can we control CPU to shield the oscillator's clock signal instead FPGA?
(2) how to connect an external oscillator to the warp k3 kit, and how to configure the external oscillator to cooperate with the warp k3.

Thanks

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#2 2018-Feb-21 09:59:03

murphpo
Administrator
From: Mango Communications
Registered: 2006-Jul-03
Posts: 5159

Re: connect an external oscillator

You can use a CM-PLL clock module to provide an external frequency reference for the WARP v3 kit.

Can you describe your experiment in more detail? I don't understand the goal here. Y1 is an 80MHz TCXO - it's a pretty good oscillator (low phase noise, good frequency stability). What clocking requirements do you have that are not met by the default WARP v3 clocking scheme?

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#3 2018-Feb-23 19:46:45

fc
Member
Registered: 2016-Oct-14
Posts: 21

Re: connect an external oscillator

Thanks for your reply.

I know the Y1 is pretty good oscillator, which is robustness to environment noise and temperature changes. But now, I want to use a oscillator that hasn’t the temperature compensated unit to compensate when the environment temperature changes. So, I wonder that whether exits a good way to connect a external oscillator which hasn't the temperature compensated module to replace Y1, and shield the clock signal produced by Y1.

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#4 2018-Feb-23 19:55:10

fc
Member
Registered: 2016-Oct-14
Posts: 21

Re: connect an external oscillator

I want to ask another question, whether the warp k3 kit has a CPU,  and can we control CPU to shield the clock signal produced by Y1.

Thanks.

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#5 2018-Feb-24 14:34:05

murphpo
Administrator
From: Mango Communications
Registered: 2006-Jul-03
Posts: 5159

Re: connect an external oscillator

But now, I want to use a oscillator that hasn’t the temperature compensated unit to compensate when the environment temperature changes. So, I wonder that whether exits a good way to connect a external oscillator which hasn't the temperature compensated module to replace Y1, and shield the clock signal produced by Y1.

This would be possible using the CM-PLL module plus an external frequency reference (typically 10MHz) with the stability characteristics you require.

However, I still don't understand the experiment you are trying to run. Why do you want to use an oscillator this is not temperature compensated? Are you studying oscillator characteristics? Or are you studying how to build wireless systems which are robust to frequency offsets?

I want to ask another question, whether the warp k3 kit has a CPU,  and can we control CPU to shield the clock signal produced by Y1.

The WARP v3 clocking design drives a copy of the master clock into the FPGA. Our reference designs (802.11, WARPLab) implement CPUs and PHY logic in the FPGA. If you use a CM-PLL module as the WARP v3 clock source, the WARP v3 on-board oscillator will not be used for the RF interfaces or any logic in the FPGA.

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#6 2018-Feb-24 20:48:19

fc
Member
Registered: 2016-Oct-14
Posts: 21

Re: connect an external oscillator

“This would be possible using the CM-PLL module plus an external frequency reference (typically 10MHz) with the stability characteristics you require.”

Sorry,I cannot clearly understand the meaning of "plus an external frequency reference (typically 10MHz)", whether you mean that the CM-PLL module offer an external frequency reference or connecting an external oscillator to offer a frequency reference.

Another question, I want to know can we connect an exteranl oscillator expect using the CM-PLL module on the warp k3 board, if could, how to connect it into the warp k3 board, and what factors do we need to pay attention to ?

The reason why i want to connect an external oscillator without temperature compensated module  is to exploring the impacts of frequency offset by the not good oscillators when the surrounding environment changes. Due to the Y1 is pretty good, which is robust to the change of environment, so I want to use a not good oscillator replace Y1. So i want to know the practicability of this apporach.

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#7 2018-Feb-25 11:57:14

murphpo
Administrator
From: Mango Communications
Registered: 2006-Jul-03
Posts: 5159

Re: connect an external oscillator

Sorry,I cannot clearly understand the meaning of "plus an external frequency reference (typically 10MHz)", whether you mean that the CM-PLL module offer an external frequency reference or connecting an external oscillator to offer a frequency reference.

Refer to the CM-PLL user guide for details on the hardware. The module implements a PLL+VCXO. The PLL adjusts the frequency of the VCXO to match a multiple of the frequency of the reference input. You can use an external reference (typically 10MHz, but other reference frequencies are possible), another CM-PLL (for daisy-chaining WARP v3 nodes) or the WARP v3 board's TCXO (typically used by the "master" node in a daisy chain).

Another question, I want to know can we connect an exteranl oscillator expect using the CM-PLL module on the warp k3 board, if could, how to connect it into the warp k3 board, and what factors do we need to pay attention to ?

The WARP v3 board's clock module header is the only way to provide off-board clock signals to the FPGA and RF interfaces. You could design a custom clock module - the specs are in the WARP v3 user guide. Mango's CM-PLL is the best option if you want to use an existing clock module.

The reason why i want to connect an external oscillator without temperature compensated module  is to exploring the impacts of frequency offset by the not good oscillators when the surrounding environment changes. Due to the Y1 is pretty good, which is robust to the change of environment, so I want to use a not good oscillator replace Y1. So i want to know the practicability of this apporach.

I still don't understand the goal of the experiment. Are you trying to characterize the frequency stability of various oscillators? The frequency stability is usually specified in the oscillator's data sheet (often in units of ppm / deg C). If you want to observe an oscillator's frequency directly, you could do this without the WARP v3 kit - just measure the frequency of the oscillator output on an oscilloscope or spectrum analyzer.

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