11、GPS L1信号载波NCO的Verilog 源码
\qquad 下面是GPS L1信号载波NCO的Verilog代码（下载完整的HD-GR基带模块代码）：
// -*- Mode: Verilog -*-
// Original filename : carrier_nco.v
// Filename : gps_carrier_nco.v
// Description : Generates the 8 stage carrier local oscilator. // Author : Peter Mumford, UNSW, 2005
// Author : Cheng Huaide, turing321.com, 2015 (BDS & 1PPS - processing upgrade)/* Numerically Controlled Oscillator (NCO) which replicates the carrier frequency. This pseudo-sinusoid waveform consists of 8 stages or phases. The NCO frequency is: f = fControl * Clk / 2^N where: f = the required carrier wave frequency Clk = the system clock (= 40MHz) N = 30 (bit width of the phase accumulator) fControl = the 30 bit (unsigned) control word The generated waveforms for I & Q look like: Phase : 0 1 2 3 4 5 6 7 --------------------------------- I: -1 +1 +2 +2 +1 -1 -2 -2 Q: +2 +2 +1 -1 -2 -2 -1 +1 The nominal center frequency for the GP2015 is: IF = 1.405396825MHz Clk = 40 MHz fControl = 2^N * IF / Clk fControl = 0x23FA689 for center frequency Resolution: fControl increment value = 0.037252902 Hz Put another way: 37mHz is the smallest change in carrier frequency possible with this NCO. The carrier phase and carrier cycle count are latched into the carrier_val on the tic_enable. The carrier phase is the 10 msb of the accumulator register (accum_reg). The cycle count is the number of full carrier wave cycles between the last 2 tic_enables. The two values are combined into the carrier_val. Bits 9:0 are the carrier phase, bits 31:10 are the cycle count. */
/* Copyright (C) 2007 Peter Mumford This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/ `ifdef ENABLE_CARRIER_PHASE_MEASUREMENTmodule gps_carrier_nco (clk, rstn, tic_enable, f_control, carrier_val, i_sign, i_mag, q_sign, q_mag); input clk, rstn, tic_enable; input [28:0] f_control; output reg [31:0] carrier_val; // latched into the carrier_val on the tic_enableoutput reg i_sign, i_mag; // in-phase (cosine) carrier wave output reg q_sign, q_mag; // quadrature (sine) carrier wave reg [29:0] accum_reg; // phase accumulator registerreg [21:0] cycle_count_reg; // full cycle registerwire [3:0] phase_key; wire [30:0] accum_sum; wire accum_carry; wire [31:0] combined_carr_value; // 30 bit phase accumulator always @ (posedge clk) begin if (!rstn) accum_reg <= 0; else accum_reg <= accum_sum[29:0]; end assign accum_sum = accum_reg + f_control; assign accum_carry = accum_sum[30]; assign phase_key = accum_sum[29:26]; assign combined_carr_value[9:0] = accum_reg[29:20]; assign combined_carr_value[31:10] = cycle_count_reg; // cycle counter and value latching always @ (posedge clk) begin if (!rstn) cycle_count_reg <= 0; else if (tic_enable) begin carrier_val <= combined_carr_value; // latch in carrier value, then... cycle_count_reg <= 0; // reset counter end else if (accum_carry) cycle_count_reg <= cycle_count_reg + 1'd1; end // look up table for carrier pseudo-sinewave generation always @ (phase_key) // ?? is there a way to have or'ed values in case statements ?? case (phase_key) // 0 0 degrees 15 : begin i_sign <= 0; i_mag <= 0; q_sign <= 1; q_mag <= 1; end 0 : begin i_sign <= 0; i_mag <= 0; q_sign <= 1; q_mag <= 1; end // 1 45 degrees 1 : begin i_sign <= 1; i_mag <= 0; q_sign <= 1; q_mag <= 1; end 2 : begin i_sign <= 1; i_mag <= 0; q_sign <= 1; q_mag <= 1; end // 2 90 degrees 3 : begin i_sign <= 1; i_mag <= 1; q_sign <= 1; q_mag <= 0; end 4 : begin i_sign <= 1; i_mag <= 1; q_sign <= 1; q_mag <= 0; end // 3 135 degrees 5 : begin i_sign <= 1; i_mag <= 1; q_sign <= 0; q_mag <= 0; end 6 : begin i_sign <= 1; i_mag <= 1; q_sign <= 0; q_mag <= 0; end // 4 180 degrees 7 : begin i_sign <= 1; i_mag <= 0; q_sign <= 0; q_mag <= 1; end 8 : begin i_sign <= 1; i_mag <= 0; q_sign <= 0; q_mag <= 1; end // 5 225 degrees 9 : begin i_sign <= 0; i_mag <= 0; q_sign <= 0; q_mag <= 1; end 10 : begin i_sign <= 0; i_mag <= 0; q_sign <= 0; q_mag <= 1; end // 6 270 degrees 11 : begin i_sign <= 0; i_mag <= 1; q_sign <= 0; q_mag <= 0; end 12 : begin i_sign <= 0; i_mag <= 1; q_sign <= 0; q_mag <= 0; end // 7 315 degrees 13 : begin i_sign <= 0; i_mag <= 1; q_sign <= 1; q_mag <= 0; end 14 : begin i_sign <= 0; i_mag <= 1; q_sign <= 1; q_mag <= 0; end endcase // case(phase_key)
endmodule // gps_carrier_nco `else // ENABLE_CARRIER_PHASE_MEASUREMENTmodule gps_carrier_nco (clk, rstn, f_control, i_sign, i_mag, q_sign, q_mag); input clk, rstn; input [28:0] f_control; output reg i_sign, i_mag; // in-phase (cosine) carrier wave output reg q_sign, q_mag; // quadrature (sine) carrier wave reg [29:0] accum_reg; // phase accumulator registerwire [3:0] phase_key; wire [30:0] accum_sum; // 30 bit phase accumulator always @ (posedge clk) begin if (!rstn) accum_reg <= 0; else accum_reg <= accum_sum[29:0]; end assign accum_sum = accum_reg + f_control; assign phase_key = accum_sum[29:26]; // look up table for carrier pseudo-sinewave generation always @ (phase_key) // ?? is there a way to have or'ed values in case statements ?? case (phase_key) // 0 0 degrees 15 : begin i_sign <= 0; i_mag <= 0; q_sign <= 1; q_mag <= 1; end 0 : begin i_sign <= 0; i_mag <= 0; q_sign <= 1; q_mag <= 1; end // 1 45 degrees 1 : begin i_sign <= 1; i_mag <= 0; q_sign <= 1; q_mag <= 1; end 2 : begin i_sign <= 1; i_mag <= 0; q_sign <= 1; q_mag <= 1; end // 2 90 degrees 3 : begin i_sign <= 1; i_mag <= 1; q_sign <= 1; q_mag <= 0; end 4 : begin i_sign <= 1; i_mag <= 1; q_sign <= 1; q_mag <= 0; end // 3 135 degrees 5 : begin i_sign <= 1; i_mag <= 1; q_sign <= 0; q_mag <= 0; end 6 : begin i_sign <= 1; i_mag <= 1; q_sign <= 0; q_mag <= 0; end // 4 180 degrees 7 : begin i_sign <= 1; i_mag <= 0; q_sign <= 0; q_mag <= 1; end 8 : begin i_sign <= 1; i_mag <= 0; q_sign <= 0; q_mag <= 1; end // 5 225 degrees 9 : begin i_sign <= 0; i_mag <= 0; q_sign <= 0; q_mag <= 1; end 10 : begin i_sign <= 0; i_mag <= 0; q_sign <= 0; q_mag <= 1; end // 6 270 degrees 11 : begin i_sign <= 0; i_mag <= 1; q_sign <= 0; q_mag <= 0; end 12 : begin i_sign <= 0; i_mag <= 1; q_sign <= 0; q_mag <= 0; end // 7 315 degrees 13 : begin i_sign <= 0; i_mag <= 1; q_sign <= 1; q_mag <= 0; end 14 : begin i_sign <= 0; i_mag <= 1; q_sign <= 1; q_mag <= 0; end endcase // case(phase_key)
endmodule // gps_carrier_nco `endif // ENABLE_CARRIER_PHASE_MEASUREMENT本文来自互联网用户投稿，文章观点仅代表作者本人，不代表本站立场，不承担相关法律责任。如若转载，请注明出处。 如若内容造成侵权/违法违规/事实不符，请点击【内容举报】进行投诉反馈！