Digital interpolation filter, corresponding rhythm changing device and receiving equipment

A digital device for changing a sampling frequency of a signal x(t), comprising:

• at least one digital interpolation filtering device with fractional delay of the signal x(t), comprising:
• a signal input to receive a series of input samples of a signal x(t) taken at sampling instants of the form nTs, with n being an integer, Ts being a sampling period;
• an output which delivers a series of output samples approximating the signal x(t) at sampling instants of the form (n+d)Ts based on the series of input samples of said signal x(t) with d being a real number defining the sampling instants;
• a removable or non-removable memory for storing a sequence of instructions;
• a computing machine, which is connected to receive the series of input samples from the input and deliver the series of output samples to the output, and which is configured to execute the sequence of instructions to implement:
• a Newton structure implementing a first transfer function H1d(Z−1) representing a Lagrange-polynomial interpolation of said series of input samples;
• and
• another structure implementing a second transfer function H2d(Z−1) representing another polynomial interpolation of said series of input samples, said other structure comprising at least said Newton structure, and
• wherein said at least one digital interpolation filtering device has a transfer function in the Z-transform domain, Hcd(Z−1), which comprises a linear combination between the first transfer function and the second transfer function and is a function of at least one real combination parameter c;
• and
• at least one real combination parameter input to receive the at least one real combination parameter c and connected to apply the at least one real combination parameter c to the at least one digital interpolation filtering device, wherein a value of the at least one real combination parameter c received at the at least one real combination parameter input determines a sampling frequency of the series of output samples approximating the signal x(t) delivered by the digital interpolation filtering device at the output.

Equipment comprising:

• an antenna delivering a radio-frequency signal x(t);
• at least one processing element, which is connected to receive the radiofrequency signal x(t) from the antenna and generates a series of input samples of the signal x(t) taken at sampling instants of the form nTs, with n being an integer, Ts being a sampling period;
• at least one digital interpolation filtering device with fractional delay for changing a sampling frequency of the radio-frequency signal x(t), the at least one digital interpolation filtering device comprising:
• a signal input connected to receive the series of input samples of the signal x(t) from the at least one processing element;
• an output which delivers a series of output samples approximating the signal x(t) at sampling instants of the form (n+d)Ts based on the series of input samples of said signal x(t) with d a real number defining the sampling instants;
• a removable or non-removable memory for storing a sequence of instructions;
• a computing machine, which is connected to receive the series of input samples from the input and deliver the series of output samples to the output, and which is configured to execute the sequence of instructions to implement:
• a Newton structure implementing a first transfer function H1d(Z−1) representing a Lagrange-polynomial interpolation of said series of input samples;
• and
• another structure implementing a second transfer function H2d(Z−1) representing another polynomial interpolation of said series of input samples, said other structure comprising at least said Newton structure,
• wherein said at least one digital interpolation filtering device has a transfer function in the Z-transform domain, Hcd(Z−1), which comprises a linear combination between the first transfer function and the second transfer function and is a function of at least one real combination parameter c;
• and
• at least one real combination parameter input to receive the at least one real combination parameter c and connected to apply the at least one real combination parameter c to the at least one digital interpolation filtering device, wherein a value of the at least one real combination parameter c received at the at least one real combination parameter input determines a sampling frequency of the series of output samples approximating the signal x(t) delivered by the digital interpolation filtering device at the output.

A system for processing an input signal, comprising:

• a digital device for changing a sampling frequency of a signal x(t), comprising:
• at least one digital interpolation filtering device with fractional delay of the signal x(t), comprising:
• a signal input to receive a series of input samples of a signal x(t) taken at sampling instants of the form nTs, with n being an integer, Ts being a sampling period;
• an output which delivers a series of output samples approximating the signal x(t) at sampling instants of the form (n+d)Ts based on the series of input samples of said signal x(t) with d being a real number defining the sampling instants;
• a removable or non-removable memory for storing a sequence of instructions;
• a computing machine, which is connected to receive the series of input samples from the input and deliver the series of output samples to the output, and which is configured to execute the sequence of instructions to implement:
• a Newton structure implementing a first transfer function H1d(Z−1) representing a Lagrange-polynomial interpolation of said series of input samples;
• and
• another structure implementing a second transfer function H2d(Z−1) representing another polynomial interpolation of said series of input samples, said other structure comprising at least said Newton structure, and
• wherein said at least one digital interpolation filtering device has a transfer function in the Z-transform domain, Hcd(Z−1), which comprises a linear combination between the first transfer function and the second transfer function and is a function of at least one real combination parameter c;
• and
• at least one real combination parameter input to receive the at least one real combination parameter c and connected to apply the at least one real combination parameter c to the at least one digital interpolation filtering device, wherein a value of the at least one real combination parameter c received at the at least one real combination parameter input determines a sampling frequency of the series of output samples approximating the signal x(t) delivered by the digital interpolation filtering device at the output;
• and
• a controller to program the digital interpolation filtering device, wherein said controller comprises:
• a non-transitory computer-readable memory storing at least one value of the at least one combination parameter c to be applied to the digital interpolation filtering device;
• and
• a microcontroller configured to transmit the at least one value of the at least one combination parameter c to the at least one real combination parameter input of the digital interpolation filtering device and thereby determine the sampling frequency of the series of output samples delivered by the digital interpolation filtering device,
• wherein the digital interpolation filtering device is configured to receive the at least one value and process the series of input samples of the signal x(t) by using the received at least one value.