fm demod

src/fm_demod.rs

@@ -1,4 +1,6 @@
-use crate::iq_reader::{IqChunk, IqSample};
+use crate::iq_reader::IqSample;
+
+pub type Phase = f32;
 
 pub struct FmDemod<I> {
     pub inner: I,
@@ -13,9 +15,10 @@ impl<I> FmDemod<I> {
         }
     }
 
-    pub fn process_sample(&mut self, sample: IqSample) -> IqSample {
-        // TODO: FM Demodulation
-        todo!();
+    pub fn process_sample(&mut self, sample: IqSample) -> Phase {
+        let phase_diff = sample * self.prev_sample.conj();
+        self.prev_sample = sample;
+        phase_diff.arg()
     }
 }
 
@@ -23,7 +26,7 @@ impl<I, E> Iterator for FmDemod<I>
 where
     I: Iterator<Item = Result<IqSample, E>>,
 {
-    type Item = Result<IqSample, E>;
+    type Item = Result<Phase, E>;
 
     fn next(&mut self) -> Option<Self::Item> {
         match self.inner.next()? {

src/iq_reader.rs

@@ -6,18 +6,18 @@ use std::io::{BufReader, ErrorKind, Read};
 pub type IqSample = Complex<f32>;
 
 // Data chunk
-#[derive(Debug)]
-pub struct IqChunk {
-    pub samples: Vec<IqSample>,
-}
-
-impl IqChunk {
-    pub fn new() -> Self {
-        IqChunk {
-            samples: Vec::<IqSample>::new(),
-        }
-    }
-}
+// #[derive(Debug)]
+// pub struct IqChunk {
+//     pub samples: Vec<IqSample>,
+// }
+//
+// impl IqChunk {
+//     pub fn new() -> Self {
+//         IqChunk {
+//             samples: Vec::<IqSample>::new(),
+//         }
+//     }
+// }
 
 pub struct FileSource {
     // Buffer

src/main.rs

@@ -17,11 +17,12 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     let pipeline = source
         .agc(20_000_000.0, 1.0, 0.001, 100.0)
-        .fir::<64>(taps, 4);
+        .fir::<64>(taps, 4)
+        .demodulate();
 
-    for sample_r in pipeline {
-        let sample = sample_r?;
-        println!("sample : {} + i{}", sample.re, sample.im);
+    for phase_r in pipeline {
+        let phase = phase_r?;
+        println!("phase : {}", phase);
     }
 
     Ok(())

src/pipeline.rs

@@ -1,5 +1,6 @@
 use crate::agc::Agc;
 use crate::fir::Fir;
+use crate::fm_demod::FmDemod;
 use crate::iq_reader::IqSample;
 
 pub trait DspPipelineExt<E>: Iterator<Item = Result<IqSample, E>> + Sized {
@@ -10,6 +11,10 @@ pub trait DspPipelineExt<E>: Iterator<Item = Result<IqSample, E>> + Sized {
     fn fir<const N: usize>(self, taps: [f32; N], decimation_factor: usize) -> Fir<Self, N> {
         Fir::new(self, taps, decimation_factor)
     }
+
+    fn demodulate(self) -> FmDemod<Self> {
+        FmDemod::new(self)
+    }
 }
 
 impl<I, E> DspPipelineExt<E> for I where I: Iterator<Item = Result<IqSample, E>> {}