What should be the IF in VCO design using Superheterodyne?

[acey80]

VCO Design....

What should be my IF in designing VCO at 868 MHz CMOS Tech, using Superheterodyne Transceiver?
Thanks!

 

[flatulent]

Re: VCO Design....

There are many things to consider. One is the image response. The usual rule of thumb is to make the IF be above 10% of the RF frequency. This can be made lower if your filtering in the RF has many poles.

Another thing is the IMD products which fall in the IF range. Pay special attention to input frequency ranges with high power broadcast stations and their harmonics.

 

[acey80]

Re: VCO Design....

Opps! Actually I'm quite new in this RF technology. IMD Products?? What does it mean? Is it Inter-Metal Dielectric?, in-mold decals?, intermodulation distortion?, Initial Marching Direction?, :?:

 

[hrkhari]

Re: VCO Design....

IMD products are the Intermodulation Product, which is defined as the weighted summation or subtraction of the input LO and RF frequencies. This phenomenon is due to the nonlinearity of the circuitry it self.

Rgds