Method for designing a digital reception filter and corresponding receiving device
A method is provided for designing a digital reception filter for a wanted signal. The method includes modeling at least one transmission channel of at least one signal interfering with said wanted signal in such a way that the pattern of an interfering channel is obtainable, in bleaching said at least one interfering signal by a bleaching filter taking into consideration said interfering channel pattern and a noise thereon (pattern noise) and in calculating the coefficients of said digital reception filter using at least one coefficient of the bleaching filter.
1. Method for designing a digital reception filter for a main signal, the method comprising:
modelling at least one channel for transmission of at least one signal interfering with said main signal, so as to obtain an interfering channel model;
whitening of said at least one interfering signal, by a whitening filter taking into account said interfering channel model and a noise on said model, referred to as a model noise;
calculating coefficients of said digital reception filter on the basis of at least one coefficient of said whitening filter;
wherein, if said interfering signal is transmitted in a desired frequency band, called a co-channel interfering signal, said whitening filter, called the whitening filter W 1 , verifies the equation:
W
1
(
z
)
·
W
1
*
(
1
/
z
*
)
=
1
G
1
(
z
)
·
G
1
*
(
1
/
z
*
)
+
σ
2
with
G
1
(
z
)
=
R
(
z
)
·
J
1
(
z
)
,
and
J
1
(
z
)
=
Tx
(
z
)
+
σ
1
and, if said interfering signal is transmitted in a frequency band different from said desired frequency band, called an adjacent interfering signal, said whitening filter, called the second whitening filter W 2 , verifies the equation:
W
2
(
z
)
·
W
2
*
(
1
/
z
*
)
=
1
G
2
(
z
)
·
G
2
*
(
1
/
z
*
)
+
σ
2
with
G
2
(
z
)
=
R
(
z
)
·
Rx
1
(
z
)
·
J
2
(
z
)
,
where
σ 2 is the power of said model noise;
σ 1 2 is the power of a thermal white noise;
Tx(z) is the z-transform of a transmission filter Tx;
R(z) is the z-transform of a radio filter R;
Rx 1 (z) is the z-transform of a first filter Rx 1 ;
J 2 (z) is the z-transform of a frequency-shifted transmission filter.
2. Design method according to claim 1 , and further comprising parameterizing the complexity of said digital reception filter by said model noise.
3. Design method according to claim 1 , wherein said whitening filter comprises a minimum-phase filter.
4. Design method according to claim 1 , wherein said modelling step takes into account:
at least one filter for transmission of said main signal and/or said at least one interfering signal;
at least one channel for propagation of said interfering signal of which the transfer function is modelled by the identity function;
at least one filter representing at least one radio processing operation applied to said main signal at reception of said main signal, called a radio filter.
5. Device for receiving a main signal transmitted in a desired frequency band, the device comprising:
a series filtering architecture making it possible to at least partially eliminate contribution of at least one disturbance affecting said main signal, including:
at least one first filter suitable for the disturbances belonging to the group consisting of:
at least one interfering signal transmitted in said desired frequency band, called a co-channel interfering signal; and
at least one thermal white noise; and
at least one second filter suitable for at least one interfering signal transmitted in a frequency band different from said desired frequency band, called an adjacent interfering signal,
coefficients of at least one of said first and second filters are a function of coefficients of a filter for whitening at least one co-channel and/or adjacent interfering signal, said whitening filter taking into account a noise on a model of a channel for transmission of said interfering signal, called model noise,
said filter for whitening at least one co-channel interfering signal, called the first whitening filter W 1 , verifying the equation:
W
1
(
z
)
·
W
1
*
(
1
/
z
*
)
=
1
G
1
(
z
)
·
G
1
*
(
1
/
z
*
)
+
σ
2
with
G
1
(
z
)
=
R
(
z
)
·
J
1
(
z
)
,
and
J
1
(
z
)
=
Tx
(
z
)
+
σ
1
and said filter for whitening at least one adjacent interfering signal, called the second whitening filter W 2 , verifying the equation:
W
2
(
z
)
·
W
2
*
(
1
/
z
*
)
=
1
G
2
(
z
)
·
G
2
*
(
1
/
z
*
)
+
σ
2
with
G
2
(
z
)
=
R
(
z
)
·
Rx
1
(
z
)
·
J
2
(
z
)
,
where
σ 2 is the power of said model noise;
σ 1 2 is the power of a thermal white noise;
Tx(z) is the z-transform of a transmission filter Tx;
R(z) is the z-transform of a radio filter R;
Rx 1 (z) is the z-transform of the first filter Rx 1 ;
J 2 (z) is the z-transform of a frequency-shifted transmission filter.
6. Receiving device according to claim 5 , and further comprising a detector to detect at least one adjacent interfering signal determining the activation of said second filter.
7. Receiving device according to claim 5 , wherein the device is linear and of the MMSE type (“Minimum Mean Square Error”).
8. Receiving device according to claim 5 , wherein coefficients of at least one of said first and second filters are a function of coefficients of a filter for whitening at least one co-channel and/or adjacent interfering signal, said whitening filter taking into account a noise on a model of a channel for transmission of said interfering signal, called model noise.
9. Receiving device according to claim 8 , wherein, for the first filter, said transmission channel model takes into account:
a filter for transmission of said main signal and/or said at least one co-channel interfering signal;
at least one channel for propagation of said co-channel interfering signal of which the transfer function is modelled by the identity function;
at least one filter representing at least one radio processing operation applied to said main signal at reception of said main signal, called a radio filter.
10. Receiving device according to claim 8 wherein, for said second filter, the transmission channel model takes into account:
a filter for transmission of said main signal;
at least one filter for transmission of said adjacent interfering signals;
at least one channel for propagation of said adjacent interfering signals of which the transfer function is modelled by the identity function;
at least one filter representing at least one radio processing operation applied to said main signal at reception of said main signal, called a radio filter;
said first filter.