1 /* ----------------------------------------------------------------------
9  * Target Processor: Cortex-M and Cortex-A cores
10  * -------------------------------------------------------------------- */
12  * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
14  * SPDX-License-Identifier: Apache-2.0
20  * www.apache.org/licenses/LICENSE-2.0
38   const float64_t * pCoeff = S->pTwiddleRFFT;       /* Points to RFFT Twiddle factors */  in stage_rfft_f64()
46    k = (S->Sint).fftLen - 1;  in stage_rfft_f64()
61    // U2 = XB(1) - XA(1); % It is imaginary  in stage_rfft_f64()
64    // real(tw * (xB - xA)) = twR * (xBR - xAR) - twI * (xBI - xAI);  in stage_rfft_f64()
65    // imag(tw * (xB - xA)) = twI * (xBR - xAR) + twR * (xBI - xAI);  in stage_rfft_f64()
67    *pOut++ = 0.5 * ( t1a - t1b );  in stage_rfft_f64()
69    // XA(1) = 1/2*( U1 - imag(U2) +  i*( U1 +imag(U2) ));  in stage_rfft_f64()
81          XB = conj(XA([1 end:-1:2]));  in stage_rfft_f64()
82          TW = i*exp(-2*pi*i*[0:L/2-1]/L).';  in stage_rfft_f64()
84             XA(l) = 1/2 * (XA(l) + XB(l) + TW(l) * (XB(l) - XA(l)));  in stage_rfft_f64()
86 …XA(1) = 1/2* (XA(1) + XB(1) + TW(1) * (XB(1) - XA(1))) + i*( 1/2*( XA(1) + XB(1) + i*( XA(1) - XB(…  in stage_rfft_f64()
98       t1a = xBR - xAR ;  in stage_rfft_f64()
101       // real(tw * (xB - xA)) = twR * (xBR - xAR) - twI * (xBI - xAI);  in stage_rfft_f64()
102       // imag(tw * (xB - xA)) = twI * (xBR - xAR) + twR * (xBI - xAI);  in stage_rfft_f64()
109       *pOut++ = 0.5 * (xAI - xBI + p1 - p2 ); //xAI  in stage_rfft_f64()
112       pB -= 2;  in stage_rfft_f64()
113       k--;  in stage_rfft_f64()
125   const float64_t *pCoeff = S->pTwiddleRFFT;        /* Points to RFFT Twiddle factors */  in merge_rfft_f64()
131    k = (S->Sint).fftLen - 1;  in merge_rfft_f64()
139    *pOut++ = 0.5 * ( xAR - xAI );  in merge_rfft_f64()
146       /* G is half of the frequency complex spectrum */  in merge_rfft_f64()
148       //    Xk(k) = 1/2 * (G(k) + conj(G(N-k+2)) + Tw(k)*( G(k) - conj(G(N-k+2))));  in merge_rfft_f64()
157       t1a = xAR - xBR ;  in merge_rfft_f64()
165       // real(tw * (xA - xB)) = twR * (xAR - xBR) - twI * (xAI - xBI);  in merge_rfft_f64()
166       // imag(tw * (xA - xB)) = twI * (xAR - xBR) + twR * (xAI - xBI);  in merge_rfft_f64()
167       *pOut++ = 0.5 * (xAR + xBR - r - s ); //xAR  in merge_rfft_f64()
168       *pOut++ = 0.5 * (xAI - xBI + t - u ); //xAI  in merge_rfft_f64()
171       pB -= 2;  in merge_rfft_f64()
172       k--;  in merge_rfft_f64()
191   @brief         Processing function for the Double Precision floating-point real FFT.
196                    - value = 0: RFFT
197                    - value = 1: RIFFT
206    arm_cfft_instance_f64 * Sint = &(S->Sint);  in arm_rfft_fast_f64()
207    Sint->fftLen = S->fftLenRFFT / 2;  in arm_rfft_fast_f64()
215       /* Complex radix-4 IFFT process */  in arm_rfft_fast_f64()