A high-precision multi-phase Crest Factor Reduction (CFR) system for performing crest factor reduction on an input signal to obtain a peak-clipped signal for output, the system includes a main circuit, a branch circuit for generating a peak cancellation signal, and an adder/subtractor module;
- an original input signal is divided into two paths and input into the main circuit and branch circuit respectively;
- on the main circuit, the original input signal is delayed to generate a main circuit output signal;
- the branch circuit is provided with an interpolation module, a multi-phase max mag select module, a peak screening module, a peak allocation module, a multi-phase Cancel Pulse Generation (CPG) coefficients generation module and a cancellation signal generation module;
- the adder/subtractor module subtracts the peak cancellation signal from the main circuit output signal to obtain the peak-clipped signal for output;
- wherein,
- the interpolation module is configured to:
- when the original input signal with a sampling rate of fs is input into the branch circuit, the original input signal is interpolated N times to N*fs sampling rate, fs is an original data sampling rate, and after interpolation, one signal data x (n) becomes N-phase signal data X(Nn), X(Nn+1), . . . . X(Nn+N-1) of different phases, wherein N is an integer greater than or equal to 2, and n, Nn, Nn+1, . . . . Nn+N-1 represent time;
- the multi-phase max mag select module is configured to:
- for each signal data x(n), according to the N-phase signal data X(Nn), X(Nn+1), . . . . X(Nn+N-1) obtained after interpolation, compare the magnitudes of these N phases, select a phase with the maximum magnitude from the N phases as a peak point output, and record the phase information of the peak point position;
- and, form an N-phase peak signal according to the magnitude and phase of the peak point extracted from the N-phase signal data;
- the peak screening module is configured to:
- perform two peak screenings in sequence, including an initial peak screening and a secondary peak screening;
- the initial peak screening is to perform peak detection of the N-phase peak signal by sliding window processing;
- and the secondary peak screening is peak window screening which selects a maximum peak in the window according to a set window length, after two peak screenings, obtain a maximum peak set which contains multiple maximum peaks;
- and, store peak noise, which includes:
- retain magnitude and phase information corresponding to maximum peak points, and set all data at positions other than the maximum peak points to 0 to obtain a noise set, the noise set corresponding to a noise signal;
- the peak allocation module is configured to:
- perform filter multiplication allocation on the maximum peaks in the noise set, wherein, a number of multipliers is allocated according to a density of the maximum peaks in the noise set;
- a filter is used to filter the noise signal to maintain the same spectral characteristics as the original input signal;
- the multi-phase CPG coefficients generation module is configured to:
- perform a convolution operation on a single-phase CPG coefficient and a multi-phase fractional delay filter to obtain multi-phase CPG coefficients including multiple groups of CPG coefficients, each group of CPG coefficient corresponds to a phase;
- the single-phase CPG coefficient is obtained by designing a filter with a same spectrum as the original input signal at the rate fs;
- the cancellation signal generation module is configured to:
- for noise of different phases within the noise set, perform a convolution operation on the noise and a CPG coefficient of the corresponding phase to obtain a CPG pulse signal of this phase after delay compensation;
- and according to peak allocation, the CPG pulse signals of multiple phases are combined to obtain the peak cancellation signal.