Filters and Frequency Control Flashcards
6 cards from real GROL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Filters and Frequency Control flashcards as text
What component is primarily responsible for setting the resonant frequency in a crystal-controlled oscillator?
Answer: Quartz crystal
The quartz crystal's mechanical resonance determines the oscillator frequency with very high stability, overriding the effects of LC components.
A Butterworth filter is characterized by which response?
Answer: Maximally flat passband with no ripple
A Butterworth filter provides a maximally flat (no ripple) frequency response in the passband, at the expense of a less steep initial rolloff compared to other designs.
What is the cutoff frequency of a filter defined as?
Answer: The frequency at which output power is 3 dB below the passband level
The cutoff (or -3 dB) frequency is the point where output power falls to half (−3 dB) of the passband level, marking the boundary of the filter's pass region.
In a parallel LC circuit at resonance, the impedance is:
Answer: Maximum (very high)
At resonance, a parallel LC (tank) circuit presents maximum impedance because the circulating current between L and C is self-sustaining, drawing minimal current from the source.
What happens to the selectivity of a filter as its Q factor increases?
Answer: Selectivity increases
Higher Q means a narrower bandwidth relative to the center frequency, resulting in greater selectivity (ability to distinguish closely spaced signals).
What is the main advantage of using a crystal filter in a superheterodyne receiver's IF stage?
Answer: It offers very narrow, stable bandwidth for improved adjacent-channel rejection
Crystal IF filters provide extremely narrow and stable passbands, greatly improving the receiver's ability to reject adjacent-channel interference.