Need help in Crystal LTSpice Model

[exhalt]

I need to attach a 433.92MHz crystal at the part where it is circled by red. I am using LTSpice.

I would need some help in this. Any values that i need to insert for the model? Or is there any spice model that i can use for this?

 

[esp1]

hi,
Use Key 'F2' to show the symbols, then select 'Misc' you should find the xtal symbol there.

Look at these 3 images, you have to select the values for the xtal to suit the frequency of the xtal, its a bit tricky.

You could use a Voltage source, set for SINE as quick substitute for an xtal.
E

 

[exhalt]

How am I supposed to choose the values or pick any crystal model based on the frequency that I want? Any help on that too?

Can I use the values that you have shown me?

 

[esp1]

You can get some guidance from the datasheet for the xtal you are planning to use..

I found it a real pain to get the frequency just right.

Have you tried the Yahoo LTSpice user group, its free.?


https://groups.yahoo.com/neo/groups/LTspice/files/ Lib/

 

[exhalt]

I will try later but i still hope that i can get help from here too. Or even better is there any way I can design a transmitter circuit that transmits at 145MHz?

 

[esp1]

I will try later but i still hope that i can get help from here too. Or even better is there any way I can design a transmitter circuit that transmits at 145MHz?

These ready built modules could be an option.

 

[exhalt]

Thank you but I am supposed to design it using transistor not ready made modules.

 

[FvM]

According to the thread title you are asking for a crystal model, but:

- you won't find a crystal for the 430 MHz band, SAW resonators are exclusively used in this frequency range

- some SAW resonators are two-port devices which need a basically different oscillator circuit

- presumed you have a resonator that can work in the common-base colpitts circuit, you need to correct the bias

- what's the intended output load. Are you sure that the oscillator will still work with the load connected?

 

[exhalt]

I am supposed to design a transmitter circuit to transmit a signal at 145MHz. I am not sure how to go about this. Any guidance from anyone here?

 

[FvM]

O.K., I was wrongly assuming 430 MHz. 145 MHz crystals may be available.

Basically a crystal connected between ground and base makes a colpitts crystal oscillator. But biasing the base with an AC voltage is incorrect. It must be feed by a DC voltage which can be superimposed by modulating AC.

 

[vfone]

Today are available overtone quartz crystals with frequencies up to 300 MHz.

https://www.golledge.com/docs/products/xtl_ld/xtl_ld.htm

Beware that overtone oscillators needs a special schematic topology to make them work properly. Your Colpitts oscillator may work on the fundamental of the crystal, but not on the overtone frequency.
Search the net for some examples for overtone crystal oscillators.