# how to create a 1MHz sine wave 0.4Vpp with short gaps in between?

Discussion in 'The Projects Forum' started by Abhishek Y, Apr 22, 2016.

1. ### Abhishek Y Thread Starter New Member

Mar 24, 2016
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Hey, I need assistance in my project to create a 1MHz sine wave of 0.4Vpp with short gaps of sometimes 10us and other 20us. I need it as an input to my project. Please find the attached photo of the LTspice simulation. I need it as an input to my hardware.

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2. ### RichardO Well-Known Member

May 4, 2013
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Old analog function generators (such as from Wavetek) could do this by gating one generator from another one. With any luck, you can find some of these to use.

The way they did this was to first generate a triangle using an integrator and hysterisis switch. This is similar to how a 555 timer works if the capacitor is charged and discharged from current sources. Then they clamped the integrator when it reached the desired phase (while it is going in the correct direction of voltage). The triangle wave was converted to a sine wave using a nonlinear shjaping circuit.

This might be done with a generator that uses direct digital synthesis as well. That would require more thinking on my part...

3. ### Abhishek Y Thread Starter New Member

Mar 24, 2016
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Thank you RichardO I'll see to it. But any other method you have any idea.

4. ### #12 Expert

Nov 30, 2010
16,705
7,358
You are trying to make a gated oscillator, an oscillator and a gate circuit. Make an oscillator and turn it on and off with any of a dozen methods.
You can stop the oscillator or stop the signal in a circuit after the oscillator.

5. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
You should be able to use an analog switch as a multiplexer to switch between your signal source and a passive pulldown to GND. Would you catre to share the circuit you used for the simulation with us. It might clarify what you are trying to do. We should be able to eliminate what looks like an exponential decay between the bursts.

EDIT: Yeah -- what #12 said.

6. ### Abhishek Y Thread Starter New Member

Mar 24, 2016
5
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Thank you both. I'm actually implementing a rfid tag so I'm giving data in short bursts.

7. ### ScottWang Moderator

Aug 23, 2012
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777
Here is the block diagram, you can according the block to modify to close your goal and describe some more details, when the pictures more clear then you will more quick to reach your goal.

Abhishek Y likes this.
8. ### Alec_t AAC Fanatic!

Sep 17, 2013
5,980
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For an RFID tag won't a gated 1MHz triangle wave, or even square wave, suffice? Simpler to generate than a sine-wave.

9. ### Abhishek Y Thread Starter New Member

Mar 24, 2016
5
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thank you sir

10. ### Abhishek Y Thread Starter New Member

Mar 24, 2016
5
0
ya square wave is simpler, but I'm already working with sine wave so needed it.