Hi guys,

I am new to this forum and also new to using LTspice. I have a project on simulation of chirp signals, please I will really appreciate if anyone can tell me how to simulate a simple chirp signal on LT spice and what circuit would be great for a simulation of chirp signal.

 

Define a chirp signal.

Bob

 

Hi Bob,

Chirp signals are defined as sinusoidal signals in which its frequency increases or decreases over a certain amount of time, the phase and the frequency must be specified at all time. Chirp signals are required for earth remote sensing, planetary remote sensing and they are used for several applications for example target velocity estimation, phase coding of sweep signals in communication applications, system characterisation, radar, sonar, acoustic digital imaging and determination of system response with network analyzers.

Another name for chirp signals is Linear Frequency Modulated signals. This is an angle modulated sweeping signals. Chirp signals are used to sweep through an entire frequency bandwidth from one end to another. ‘Up chirp’ is derived from this method of frequency sweeping and can be said to come into place when frequency is wept from the lowest point to the highest limit. The opposite direction of the frequency sweep is called ‘Down Chirp’.

 

Here's an example of how you do it in LTspice. Use the 'modulate' component in the 'SpecialFunctions' folder.
You can think of 'Mark' and 'Space' as multipliers.

 

Hi Alec t,

Thanks a lot for this, whats the A1 called on LTspice ?

 

As Alec_t said in his post, the component is called "modulate" and is found in the "Special Functions" folder after all of the LTC components that begin with "LTC...". There is also "modulate2" for quadrature outputs.

 

Thanks a lot, I appreciate.

 

Here's an example of how you do it in LTspice. Use the 'modulate' component in the 'SpecialFunctions' folder.
You can think of 'Mark' and 'Space' as multipliers.
View attachment 75234

I seem to be putting the Mark and space in a different place, which line on the modulate symbol should it be please ?

 

Put it in the 'Value' line.

 

Put it in the 'Value' line.

I figured out before seeing your post, thanks a lot