45 results about "Polyphase filter bank" patented technology

A time scale modification method employs separate bands obtained through an analysis polyphase filter bank with separate time-scale modification processing for the bands. The outputs are combined using a synthesis filter bank. Some constraints are imposed on the time-scale modification processing, such a limitation of the range of overlap adjustment values for bands other than the greatest energy band, to eliminate noise due to aliasing and inter-channel phase mismatch. This invention produces output quality considerably higher than conventional time-domain time-scale modification methods for general music signals with computational requirements comparable to those of conventional time-domain time-scale modification methods.

A full spectrum modulator processes a plurality of CATV channels from separate paths. Each path has (i) a first filter for pulse shaping an input channel signal and upsampling a channel frequency thereof, (ii) an interpolator for interpolating the output of the first filter to a common sample rate, and (iii) a decimator for centering the output of the interpolator on a predetermined channel bandwidth. An IDFT processor receives channel signal outputs from the decimators. A polyphase filter bank receives IDFT processed parallel channel signals from the IDFT processor. A commutator converts the processed parallel channel signals from the polyphase filter bank to a single stream of data. A second filter upsamples the single stream of data to a fixed output sampling rate and low pass filters alias signals therefrom. Both standard and harmonically related carrier CATV channel frequency plans are accommodated.

A system includes a polyphase multirate filter and a controller which, responsive to detecting a data stream: measures a current phase relationship between a current resampling filter input clock signal and a current multirate output clock signal; identifies, based on a mapping of the measured phase relationship within a pre-generated quantized mapping table, an initial polyphase filter coefficient index corresponding to the measured phase relationship; selects, based on the initial polyphase filter coefficient index identified, a corresponding polyphase filter component from within the multirate filter; configures the multirate filter to pass data from the data stream through the corresponding polyphase filter component to generate an initial output data sample; updates the initial polyphase filter coefficient index to a calculated next polyphase filter coefficient index value, in response to a request for generation of a next output data sample; and self-corrects the multirate filter responsive to a pre-identified error condition.

The invention relates to a full spectrum modulator for digital television signals. The full spectrum modulator processes a plurality of CATV channels from separate paths. Each path has (i) a first filter for pulse shaping an input channel signal and upsampling a channel frequency thereof, (ii) an interpolator for interpolating the output of the first filter to a common sample rate, and (iii) a decimator for centering the output of the interpolator on a predetermined channel bandwidth. An IDFT processor receives channel signal outputs from the decimators. A polyphase filter bank receives IDFT processed parallel channel signals from the IDFT processor. A commutator converts the processed parallel channel signals from the polyphase filter bank to a single stream of data. A second filter upsamples the single stream of data to a fixed output sampling rate and low pass filters alias signals therefrom. Both standard and harmonically related carrier CATV channel frequency plans are accommodated.

Methods to improve the data carrying capacity of CATV DOCSIS systems and other communications systems are disclosed. Communications channels may be more efficiently spaced with reduced or absent guard bands by using receivers with adaptive signal cancellation methods, equalizing circuits, or polyphase filter banks and Fast Fourier Transform signal processing methods to correct for higher levels of cross-talk. QAM type communications channels may also be utilized on a synchronized two-transmitter at a time basis by adjusting the transmitters to predefined signal levels, such as +1, −1, +½, −½ to enable the combined signals to be distinguished at the receiver. These two methods may be combined to create a still higher data throughput system.

A polyphase channelizer converts an intermediate frequency wideband signal into a complex signal that is sampled by parallel analog-to-digital converters having a bank of samplers respectively clocked by staggered clocking signals for respective converters for feeding I and Q quadrature samples to a polyphase filter bank of finite impulse response filters driving a fast Fourier transform processor for providing channelized digital signal outputs. The parallel analog-to-digital converters can operate at lower speeds but are parallel connected for effectively operating at required higher speeds. The channelizer channelizes the wideband signal using a polyphase clock for enabling high speed sampling and converting through low speed parallel analog to digital converters.

The invention discloses a method for realizing frequency spectrum sensing by using a multi-phase filter. The method is implemented on a field programmable gate array (FPGA) by using a Xilinx / System Generator development tool. According to the method, a multi-phase filtration part and an energy detection part are adopted, wherein the multi-phase filtration part comprises a data type conversion unit, a delay unit, a filter group coefficient address generation unit, a filter group coefficient storage unit, a filter group coefficient analysis unit, a multiplication unit, an addition unit, a clock synchronization unit and a fast Fourier transformation (FFT) unit; the energy detection part comprises the addition unit, the multiplication unit and a mean value acquiring unit; a wireless signal is received and subjected to frequency mixing by an antenna and then converted into I and Q channels of baseband signals; the two channels of baseband signals are sampled by two analog-to-digital converters (ADC) and then converted into digital baseband signals; the digital baseband signals are input into a multi-phase filter group and then filtered under the control of an enabling signal; and the filtered signals are input into the energy detection part and subjected to energy detection, so that the frequency spectrum sensing is realized.