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Digital filters are mainly intended for echo cancellation and other digital signal processing tasks, but they can also be used to alter the nominal frequency and resolution of the input data sequence, that is, provide oversampling. Fig.9 has the corresponding block diagram:
- The clock duty- cycle must be 50%, otherwise it has to be regenerated using a phase- locked loop; (you could try a monostable, if you are expecting operation at a single frequency only.)
- Actual adders can only add two numbers at a time, so the adder block will comprise two physical adder sets, in spite of what the block diagram shows.
- You may want to involve more input samples in the calculations, watching out for the possible effects of finite length arithmetic. If the output bus is wider than the input bus, the original samples must be shifted the appropriate number of places to the left.
- There are other options for the coefficients, and although it is not this section's purpose to discuss adder/ multiplier design in detail, it must be said that 'multiplier' design is trivial for the coefficients indicated.
- It is also possible to calculate additional samples in order to create a 4x or even 8x oversampling digital filter: In that case, the additional select inputs of the multiplexer will be driven from a counter, which runs at an appropriate multiple of the input clock frequency.
Sections' Update: The transient simulation page now includes graphs of output voltages, while the fractals section now features 12 different fractals. The converters section now comprises a successive approximation voltage diagram. An obvious omission from the simplified simulation page is a test case (a numerical example)- this will soon be rectified.
Electronics links:- Simplified Analog Electronics Simulation
- Successive approximation register and converters
- Video Digitizer
- Thermionic valves
- Simulation revisited! Transient response
- Under 50- chip simple discrete Microcontroller
Computing Projects:
- Chess programs
- Fractals!
