Frequency counter front end: A pulse-shaping (conditioning) block is required so that an unknown input waveform is compatible with the counter's clock input specifications (logic levels, edge cleanliness). Evaluate this design requirement.

Introduction / Context:
Frequency counters measure how many cycles of an input signal occur within a precise gate time. The input waveform may be noisy, analog, or outside logic thresholds. A pulse shaper or input conditioner (e.g., comparator with hysteresis, Schmitt trigger) cleans the waveform into crisp logic-level edges that the digital counter can reliably clock on.

Given Data / Assumptions:

• Unknown signal amplitude/shape and possible noise.
• Digital counter block requires specific V_IL/V_IH and adequate edge slew rate.
• We desire consistent triggering on one edge per cycle.

Concept / Approach:
The pulse shaper performs level translation and squaring. It ensures the clock input sees monotonic, sufficiently fast transitions and meets logic thresholds. Hysteresis (Schmitt action) reduces spurious triggers from noise. If necessary, attenuation or amplification precedes the squaring stage to fit the device’s safe input range.

Step-by-Step Solution:
Sense unknown input → AC/DC couple as needed.Condition via comparator/Schmitt trigger to create rail-to-rail logic pulses.Feed clean pulses into the counter’s clock pin.Calibrate trigger level and hysteresis to avoid multiple counts.

Verification / Alternative check:
Oscilloscope comparison: raw input vs. shaped output shows reduced jitter, sharper edges, and stable logic levels; counter readings become repeatable.

Why Other Options Are Wrong:
Need is not limited by 1 MHz; even low-frequency noisy signals need shaping. Sine waves also require thresholding; square waves can still need conditioning if amplitude or slew is inadequate. Synchronous architecture alone doesn’t solve analog interfacing needs.

Common Pitfalls:
Feeding analog signals directly into logic inputs; ignoring input protection; missing hysteresis causing double counts.

Final Answer:
Correct