Method for limiting amplitude of a carrier frequency output signal
View Patent ↗Partial signals of a basic frequency band are used to form a carrier frequency output signal. Each of n partial signals is attributed as an input signal to a representative main branch and the corresponding partial signal is limited in amplitude, filtered and converted into an intermediate frequency partial signal. As output signals of the main branch, the n partial signals are assembled into a common sum signal. Moreover, each partial signal reaches an auxiliary branch, whereby expected peak values of the partial signal can be determined as estimated values. Using the estimated values, the amplitude limitations of the corresponding partial signals, executed in the main branch, can be regulated in the branch.
1. A method for forming a carrier frequency output signal from n partial signals of a basic frequency band, comprising:
attributing each of the n partial signals as an input signal to a corresponding main branch and a corresponding auxiliary branch;
determining, in each corresponding auxiliary branch, an i-th estimated value in an i th auxiliary branch for 1≦i≦n for an expected peak value of the input signal in the corresponding main branch, said determining including
filtering an i-th partial signal attributed to the i-th auxiliary branch, a plurality of times corresponding to n;
forming a signal sequence based on maximum values resulting from all of said filtering of the i-th partial signal; and
determining the estimated value for the i-th auxiliary branch based on the signal sequence;
forming a corresponding information signal for each estimated value in the corresponding auxiliary branch;
limiting amplitude of the input signal in each corresponding main branch based on the corresponding information signal to keep the carrier frequency output signal limited in amplitude and free from distortion;
filtering and converting the input signal in each corresponding main branch into an intermediate frequency partial signal;
assembling n intermediate frequency partial signals into a sum signal; and
performing digital-to-analog conversion of the sum signal to produce the carrier frequency output signal.
2. A method according to claim 1 , wherein said filtering in each corresponding main branch includes sending the input signal through a root raised cosine filter.
3. A method according to claim 1 , further comprising, in each corresponding auxiliary branch
adding the signal sequence of the i-th partial signal to form an i-th amount sum; and
forming an i-th maximum value based on the i-th amount sum.
4. A method according to claim 3 , further comprising:
forming a common maximum value from m maximum values;
comparing the common maximum value with a predefined clipping value; and
forming each corresponding information signal based on said comparing.
5. A method according to claim 4 , further comprising in each corresponding main branch multilplying the corresponding information signal by a delayed partial signal.
6. A method according to claim 1 , further comprising:
creating the i-th partial signal by modulation and combination of individual signals;
using a root raised cosine filter to only slightly attenuate useful signal bands corresponding to modulation frequencies, while attenuating further partial signal bands.