Power limiting circuit
A power limiting circuit includes: a maximum value prediction filter section (MVPFS) interpolating data of one branched digital input signal; a maximum value detection section detecting maximum value of an output of the MVPFS and a time detection position thereof every constant period; a threshold subtraction section subtracting a threshold from detected maximum value and outputting a peak signal (zero when the subtraction result is negative); a coefficient selection section weighting the peak signal according to time detection position; a complex filter section limiting the weighted peak signal within a band of the input signal; a filter coefficient calculation section calculating filter coefficients of the complex filter section; a delay adjustment section delaying another of the branched input signals by a time period required for calculating the band-limited peak signal; and a subtraction section subtracting the band-limited peak signal from the other of the branched input signals subjected to delay.
1. A power limiting circuit for outputting an input signal by limiting a maximum instantaneous power value of the input signal to a predetermined power value or less, comprising:
a maximum value prediction filter section that interpolates one of branched input signals obtained by branching the input signal, which is quantized at a first sampling rate, at a second sampling rate higher than the first sampling rate;
a maximum value detection section that outputs a maximum value of the signal interpolated by the maximum value prediction filter section and a time detection position thereof every constant period corresponding to the first sampling rate;
a first subtraction section that outputs, as a peak signal, a result obtained by subtracting a preset threshold from the maximum value, the peak signal being 0 (zero) when the subtraction result is negative;
a coefficient selection section that weights the peak signal according to the time detection position;
a complex filter section that imposes a band limitation on the weighted peak signal output from the coefficient selection section;
a filter coefficient calculation section that calculates coefficients of the complex filter section;
a delay adjustment section that delays another of the branched input signals by a delay of processing from the maximum value prediction filter section to the complex filter section; and
a second subtraction section that subtracts the band-limited peak signal, which is an output of the complex filter section, from the another of the branched input signals which is subjected to delay adjustment by the delay adjustment section.
2. A power limiting circuit according to claim 1 , wherein the maximum value of the signal interpolated by the maximum value prediction filter section is detected every constant period corresponding to the first sampling rate, to thereby set an output rate of the maximum value output from the maximum value detection section to be the same as the first sampling rate.
3. A power limiting circuit according to claim 1 , wherein the filter coefficient calculation section calculates a coefficient for performing a band limitation according to a type, a signal band, or frequency characteristics of each carrier constituting the input signal.
4. A power limiting circuit according to claim 1 , wherein the filter coefficient calculation section changes, in a process of calculating a coefficient for performing a band limitation according to a signal band or frequency characteristics of each carrier constituting the input signal, distribution of amounts to be subtracted based on a type, the signal band, or the frequency characteristics of each carrier.
5. A power limiting circuit according to claim 1 , further comprising, instead of the maximum value prediction filter section, an interpolation section that performs interpolation processing without using a filter.