N-channel Multiplexed FIR Filter

FIR_NTAP_MUX is an N-channel multiplexed FIR filter designed for high sample rate applications where hardware resources are limited. The main filter core is organized as a scalable systolic array permitting the user to specify large order filters without compromising maximum attainable clock-speed.

Essentially the filter functions as if it were 'N' separate FIR filters. Each input sample is multiplexed into the filter at a sample rate equal to FS/N, where FS is the sampling frequency of the main filter core. Likewise, output samples are updated at a frequency of FS/N.

The first sample into the filter is aligned by asserting the signal x_val high. The signal y_val is asserted with the first valid output sample. Data samples are advanced in the pipeline on the rising clock-edge of clk when en is active high. When en is low then all data samples are stalled. The clock-enable signal may be used to temporarily disable the filter - or possibly to modify the effective sampling frequency of the system clock. If the clock-enable is not needed it is recommended that this signal be tied high as it will improve overall circuit performance.

• Synthesizable, technology independent VHDL Core
• N-channel FIR filter core implemented as a systolic array for  speed and scalability
• Support for one or more independent channels (8 maximum)
• Configurable and independent coefficient sets for each channel
• Configurable data width and number of taps
• Symmetric arithmetic rounding limits DC-bias problems
• Output saturation or wrap modes
• Much cheaper than implementing separate FIR filters in parallel as hardware resources are shared between all channels
• Supports 550 MHz+ sample rates (550/N MHz per channel)

• High-speed filtering applications where hardware resources are limited - e.g. when it becomes impractical to use multiple FIR filters in parallel
• Dual-channel inputs such as complex valued I/Q in digital  communications systems
• Parallel DSP processor architectures
• General purpose FIR filters with odd or even numbers of taps
• Filters with arbitrary sets of coefficients (e.g. non-symmetrical)