A hand-held wireless system directly converts a 10MHz bandwidth signal to baseba

Question

A hand-held wireless system directly converts a 10MHz bandwidth signal to baseband. A 12-bit ADC is used to convert the analog baseband signal to the digital domain for subsequent digital signal processing. The energy consumption of the ADC is measured to be 1pJ/bit. A low-pass anti-alias filter prior to the ADC can either be a 4-pole or a 10-pole Butterworth filter. The 4-pole design consumes 0.4mW and the 10-pole design consumes 1mW.

(a) What is the Nyquist sampling rate?

(b) What is the ADC sampling rate for the system with the 4-pole filter?

(c) What is the ADC sampling rate for the system with the 10-pole filter?

(d) To minimize power consumption, is it better to use the 4-pole or 10-pole filter? and why?

(e) If a new 12-bit ADC is designed in an advanced CMOS process can achieve energy consumption of just 0.1 pJ/bit, is it better to use the 4-pole or 10-pole filter? and why?

Explanation / Answer

Nyquist rate is FN = 2Fmax.

=2x10MHz

=20MHz

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