Partially Complex Modulated Filter Bank

Apparatus for processing a plurality of complex-valued subband signals, the plurality of complex-valued subband signals comprising a first complex-valued subband signal and a second complex-valued subband signal to obtain a real-valued subband signal, comprising:

• an extractor for extracting from the first complex-valued subband signal a first imaginary part, for extracting from the second complex-valued subband signal a second imaginary part and for extracting from the first, the second or a third complex-valued subband signal of the plurality of complex-valued subband signals a real part;
• a multiband filter for providing a real-valued intermediate subband signal by filtering the first imaginary part to obtain a first filtered imaginary part signal, by filtering the second imaginary part to obtain a second filtered imaginary part signal and by combining the first filtered imaginary part signal and the second filtered imaginary part signal to obtain the intermediate subband signal;
• a calculator for providing the real-valued subband signal by combining the real part and the intermediate signal;
• and
• a delayer for delaying the real part signal and for passing on the real part signal to the multiband filter in a delayed form.

Apparatus according to claim 220, wherein the extractor is operative to provide a real-valued real part signal with a value ûkn,m and a real-valued imaginary part signal with a value {circumflex over (v)}kn,m for each complex-valued subband signal with a value ŷkn,m of the plurality of complex-valued subband signals with the index m, in the range from 0 to (K−1), and wherein ûkn,m, {circumflex over (v)}kn,m and ŷkn,m fulfill a relation based on the equation

• u
• ^
• k
• n
• ,
• m
• +
• 
• 
• 
• v
• ^
• k
• n
• ,
• m
• =
• 1
• 2
• 
• y
• ^
• k
• n
• ,
• m
• ,
• m
• =
• 0
• ,
• 1
• ,
• …
• 
• ,
• K
• -
• 1.

Method for processing a plurality of real-valued subband signals, the plurality of real-valued subband signals comprising a first real-valued subband signal and a second real-valued subband signal to obtain a complex-valued subband signal, comprising:

• filtering the first real-valued subband signal to obtain a first filtered subband signal;
• filtering the second real-valued subband signal to obtain a second filtered subband signal;
• combining the first filtered subband signal and the second filtered subband signal when deriving a real-valued intermediate subband signal;
• and
• combining a real-valued subband signal from the plurality of real-valued subband signals as a real part of a complex-valued subband signal and a signal which is based on the intermediate subband signal as an imaginary part of the complex-valued subband signal.

Method for processing a plurality of complex-valued subband signals, the plurality of complex-valued subband signals comprising a first complex-valued subband signal and a second complex-valued subband signal to obtain a real-valued subband signal, comprising:

• extracting from the first complex-valued subband signal a first imaginary part;
• extracting from the second complex-valued subband signal a second imaginary part;
• extracting from the first, the second or a third complex-valued subband signal of the plurality of complex-valued subband signals a real part;
• filtering the first imaginary part to obtain a first filtered imaginary part signal;
• filtering the second imaginary part to obtain a second filtered imaginary part signal;
• combining the first filtered imaginary part signal and the second filtered imaginary part signal to obtain an intermediate subband signal;
• and
• combining the real part and the intermediate subband signal to obtain the real-valued signal the real-valued signal.