AnsweredAssumed Answered

on-off keying with AD9914

Question asked by MikeHolt on Sep 16, 2015
Latest reply on Sep 23, 2015 by LouijieC

Dear all,

 

I am not completely sure if AD9914 meets our requirements (after reading the datasheet) and I therefor would like to pose the following questions.

 

Our requirements: 
- Carrier with frequency f_c = 240MHz (later maybe 400MHz),

- on-off-keying (ook) with frequency f_ook = 120MHz (later maybe 145MHz).

 

Solution:

- SYNC_CLK = f_ook = 120 (later 145) MHz,

- direct mode,

- I/O_UPDATE  = 1, CFR1[12] = 1 (autoclear phase akkumulator), phase offset = 0.

 

Thus I hope to get the following signal: | 0 | amplitude-value1 | 0 | amplitude value2 | 0 | …, modulated onto the carrier always starting at phase = 0°, with 120MHz (up to 145MHz).

 

My questions:

  a) is it possible at all to get the required signal as proposed under solution / at all with AD9914?

  b) what is the output-signal if the amplitude is set to 0 (carrier still at 240 or 400MHz)?

  c) I/O_UPDATE = 1 i guess i need in order to get a starting phase of 0° on each SYNC_CLK rising edge. Is that true?

  d) latency for amplitude changes according to the datasheet is 102 SYSCLK cycles = 4.25 SYNC_CLK cycles.
      Does that mean the amplitude is changed:

      1. exactly 4.25 SYNC_CLK cycles after it was registered at the input pins or

      2. is it changed after 5 SYNC_CLK cycles synchronous with the next rising edge of the SYNC_CLK?

 

I would greatly appreciate if you could enlighten me regarding these questions. Thank you for your time and consideration.

 

Best regards,

Michael

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