updated Rx documentation

docs/pl_rx_subsystem.md

@@ -86,10 +86,12 @@ Implementation typically uses:
 
 ### ADC Input
 - Sampling rate: 4096 MSPS
+- Data type: **fixdt(1,16,15)** (Q1.15 format)
 
 ### PFB Channelizer
 - Decimation: 8
 - Effective bandwidth: 512 MHz
+- Input and internal scaling aligned to Q1.15 domain
 
 ### FFT
 - Size: 512
@@ -103,10 +105,48 @@ Implementation typically uses:
 
 ---
 
+## Numeric Format and Scaling
+
+### System Standardization
+
+The signal chain was standardized to a **Q1.15 fixed-point format (fixdt(1,16,15))**:
+
+- DAC output uses Q1.15
+- ADC input is reinterpreted as Q1.15 (Same Stored Integer)
+- Channelizer input operates in this normalized domain
+
+---
+
+### Channelizer Output Scaling
+
+- Native channelizer output: **sFix25_En23**
+- Rescaled and quantized to: **fixdt(1,16,15)**
+
+This conversion:
+
+- Preserves signal dynamic range
+- Maximizes fractional precision
+- Uses rounding and saturation
+- Aligns with system-wide numeric format
+
+---
+
+### Data Width Reduction
+
+- Previous format: **50 bits per complex sample** (25 bits real + 25 bits imag)
+- New format: **32 bits per complex sample** (16 bits real + 16 bits imag)
+
+Benefits:
+
+- Reduced AXI bandwidth
+- Reduced FIFO usage
+- More efficient DMA transfers
+
+---
+
 ## AXI4-Stream Output
 
-- Data type: uint64
-- Packed real/imag
+- Data type: uint32 (packed complex: 16-bit real + 16-bit imag)
 - TLAST = frame boundary
 
 ---
@@ -114,7 +154,7 @@ Implementation typically uses:
 ## Data Format
 
 - Frame size: 512 samples
-- Complex values packed into uint64
+- Complex samples packed into 32-bit words
 
 ---
 
@@ -123,6 +163,7 @@ Implementation typically uses:
 - Fully streaming pipeline
 - High throughput
 - Deterministic latency
+- Consistent fixed-point scaling (Q1.15 end-to-end)
 - Supports dual-mode operation (channelizer / bypass)
 
 ---