Frequency multiplier x2

Component: XOR port Input a, b; Output cn internal signal: delay_clk; clk period: T; clk_t0=0; a <= clk; delay_clk period: T; delay_clk_t0=0+0.25T; b<=delay_clk; c<=clk xor delay_clk; Input frequency:fin; Output frequency: fout; fout=2*fin