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Integrate MTI canceller and DC notch filter for ground clutter removal

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MTI canceller (2-pulse, H(z)=1-z^{-1}) between range decimator and
Doppler processor. Subtracts previous chirp from current, nulling DC
Doppler (stationary clutter). Pass-through when host_mti_enable=0.

DC notch filter (post-Doppler, pre-CFAR) zeros bins within
+/-host_dc_notch_width of DC. Complements MTI for residual clutter.

New host registers: 0x26 (mti_enable), 0x27 (dc_notch_width).
Both default to 0 (disabled) - fully backward-compatible.

Verification: 23/23 regression, 29/29 MTI standalone, 3/3 real-data
co-sim (5137/5137 exact match) all PASS.
This commit is contained in:
Jason
2026-03-20 16:39:17 +02:00
parent 075ae1e77a
commit ed629e7559
5 changed files with 751 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files
9_Firmware/9_2_FPGA/radar_system_top.v
+39 -6
View File
@@ -234,6 +234,10 @@ reg [7:0] host_cfar_alpha; // Opcode 0x23: threshold multiplier (Q4.4)
reg [1:0] host_cfar_mode; // Opcode 0x24: 00=CA, 01=GO, 10=SO
reg host_cfar_enable; // Opcode 0x25: 1=CFAR, 0=simple threshold
// Ground clutter removal registers (host-configurable via USB)
reg host_mti_enable; // Opcode 0x26: 1=MTI active, 0=pass-through
reg [2:0] host_dc_notch_width; // Opcode 0x27: DC notch ±width bins (0=off, 1..7)
// ============================================================================
// CLOCK BUFFERING
// ============================================================================
@@ -486,7 +490,10 @@ radar_receiver_final rx_inst (
.stm32_new_elevation_rx(stm32_new_elevation),
.stm32_new_azimuth_rx(stm32_new_azimuth),
// CFAR: Doppler frame-complete pulse
.doppler_frame_done_out(rx_frame_complete)
.doppler_frame_done_out(rx_frame_complete),
// Ground clutter removal
.host_mti_enable(host_mti_enable),
.host_dc_notch_width(host_dc_notch_width)
);
// ============================================================================
@@ -499,6 +506,26 @@ assign rx_doppler_real = rx_doppler_output[15:0];
assign rx_doppler_imag = rx_doppler_output[31:16];
assign rx_doppler_data_valid = rx_doppler_valid;
// ============================================================================
// DC NOTCH FILTER (post-Doppler-FFT, pre-CFAR)
// ============================================================================
// Zeros out Doppler bins within ±host_dc_notch_width of DC (bin 0).
// In a 32-point FFT, DC is bin 0; negative Doppler wraps to bins 31,30,...
// notch_width=1 → zero bins {0}. notch_width=2 → zero bins {0,1,31}. etc.
// When host_dc_notch_width=0: pass-through (no zeroing).
wire dc_notch_active;
wire [4:0] dop_bin_unsigned = rx_doppler_bin;
assign dc_notch_active = (host_dc_notch_width != 3'd0) &&
(dop_bin_unsigned < {2'b0, host_dc_notch_width} ||
dop_bin_unsigned > (5'd31 - {2'b0, host_dc_notch_width} + 5'd1));
// Notched Doppler data: zero I/Q when in notch zone, pass through otherwise
wire [31:0] notched_doppler_data = dc_notch_active ? 32'd0 : rx_doppler_output;
wire notched_doppler_valid = rx_doppler_valid;
wire [4:0] notched_doppler_bin = rx_doppler_bin;
wire [5:0] notched_range_bin = rx_range_bin;
// ============================================================================
// CFAR DETECTOR (replaces simple threshold detector)
// ============================================================================
@@ -520,11 +547,11 @@ cfar_ca cfar_inst (
.clk(clk_100m_buf),
.reset_n(sys_reset_n),
// Doppler processor outputs
.doppler_data(rx_doppler_output),
.doppler_valid(rx_doppler_valid),
.doppler_bin_in(rx_doppler_bin),
.range_bin_in(rx_range_bin),
// Doppler processor outputs (DC-notch filtered)
.doppler_data(notched_doppler_data),
.doppler_valid(notched_doppler_valid),
.doppler_bin_in(notched_doppler_bin),
.range_bin_in(notched_range_bin),
.frame_complete(rx_frame_complete),
// Configuration
@@ -703,6 +730,9 @@ always @(posedge clk_100m_buf or negedge sys_reset_n) begin
host_cfar_alpha <= 8'h30; // alpha=3.0 (Q4.4)
host_cfar_mode <= 2'b00; // CA-CFAR
host_cfar_enable <= 1'b0; // Disabled (simple threshold)
// Ground clutter removal defaults (disabled — backward-compatible)
host_mti_enable <= 1'b0; // MTI off
host_dc_notch_width <= 3'd0; // DC notch off
end else begin
host_trigger_pulse <= 1'b0; // Self-clearing pulse
host_status_request <= 1'b0; // Self-clearing pulse
@@ -741,6 +771,9 @@ always @(posedge clk_100m_buf or negedge sys_reset_n) begin
8'h23: host_cfar_alpha <= usb_cmd_value[7:0];
8'h24: host_cfar_mode <= usb_cmd_value[1:0];
8'h25: host_cfar_enable <= usb_cmd_value[0];
// Ground clutter removal opcodes
8'h26: host_mti_enable <= usb_cmd_value[0];
8'h27: host_dc_notch_width <= usb_cmd_value[2:0];
8'hFF: host_status_request <= 1'b1; // Gap 2: status readback
default: ;
endcase