Subversion Repositories quadrature_oscillator

// 

// Davi C. M. de Almeida

//

// Quadrature Oscillator

//

// System that impulse response is sin(wo*n) / cos(wo*n) waves with period of 100 samples (wo = pi/50)

//

// Input x in 8b8 signed fixed point format

// Output y in 8b8 signed fixed point format

//

// To make the system oscilate just give him an impulse!

// (That is, put x to 1 (16'd256) for one clock cicle and 0 in the rest)

//

// If you want more bits of resolution in the waves just multiply the impulse by powers of 2

// Eg. For 9 bits of resolution use an impulse x of 16'd256 * 2 = 16'd512  

//       For 10 bits of resolution use an impulse x of 16'd256 * 4 = 16'd1024

module quad_oscillator(

        input   clk, rst,

        input signed [15:0] x,

        output signed [15:0] sin, cos

);

        // registers z^(-1)

        reg signed [15:0] z1, z2;

        // auxiliary wires

        wire signed [23:0] za1, za2, zb1_sin, zb1_cos, sx1;

        wire signed [15:0] v;

        // synchronism

        always @ (posedge clk or posedge rst) begin

                if (rst == 1) begin

                        z1 <= 16'd0;

                        z2 <= 16'd0;

                end

                else begin

                        z1 <= v;

                        z2 <= z1;

                end

        end

        // routing

        assign za1 = (z1 <<< 9) - z1;

        assign za2 = (z2 <<< 8);

        assign zb1_sin = (z1 <<< 4);

        assign zb1_cos = -(z1 <<< 8) + z1;

        assign sx1 = za1 - za2;

        assign v = x + sx1[23:8];

        // outputs

        assign sin = zb1_sin[23:8];

        assign cos = v + zb1_cos[23:8];

endmodule