aht2000
Junior Member level 3
As a way to learn more about RF design, I am considering to build an FM Band receiver. I am not looking for a professional level outcome but rather to learn. I have an oscilloscope with 200MHz bandwidth, as well as a low cost VNA. I built the attached block diagram for how the receiver would look like. Cost is not a concern as I am not looking for competing with commercial existing FM receiver but rather to learn.
Any feedback on this block diagram?
I started with the first stage which is the antenna and RF amplifier. I used the VNA to measure the impedance of a short wire antenna (20 cm). I understand that this is far from ideal, but this is what I can practically afford from a physical constraint point of view.
I built as well a common emitter amplifier with a decent gain of 25db from 45-200MHz (measured with VNA) based on the BFP420 transistor.
My first challenge is how to match these 2 together. I can do that for a fixed frequency, but what I found out that both antenna impedance and S11 (input impedance) of the RF amplifier change across the 20MHz FM Band.
Does such matching network exist between a load and generator for which their own impedance also change over frequency. How does commercial FM receivers address this? Do they just design for one frequency in the middle of the band.
Thank you.
Any feedback on this block diagram?
I started with the first stage which is the antenna and RF amplifier. I used the VNA to measure the impedance of a short wire antenna (20 cm). I understand that this is far from ideal, but this is what I can practically afford from a physical constraint point of view.
I built as well a common emitter amplifier with a decent gain of 25db from 45-200MHz (measured with VNA) based on the BFP420 transistor.
My first challenge is how to match these 2 together. I can do that for a fixed frequency, but what I found out that both antenna impedance and S11 (input impedance) of the RF amplifier change across the 20MHz FM Band.
Does such matching network exist between a load and generator for which their own impedance also change over frequency. How does commercial FM receivers address this? Do they just design for one frequency in the middle of the band.
Thank you.