AdvancedA-002-011-002
What factor determines the bandwidth and response shape of a crystal lattice filter?
C
Answer
Circuit design and power supplies
Type
A
The amplitude of the signals passing through the filter
B
The gain of the RF stage following the filter
C
The relative frequencies of the individual crystals
D
The centre frequency chosen for the filter
Answer Notes
In a crystal lattice filter, the overall frequency response—specifically the bandwidth and the shape of the passband—is determined by the slight differences in the resonant frequencies of the individual quartz crystals used in the circuit.
By carefully selecting crystals with specific relative frequencies, circuit designers can spread out the extremely narrow resonance of a single crystal to create a usable passband (such as 2.4 kHz for SSB voice) while maintaining a flat top and steep skirts.
Other factors listed do not change the filter's shape. The centre frequency merely dictates where the filter operates in the RF spectrum, while signal amplitude and following stage gain have absolutely no effect on the physical resonant properties of the lattice.
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What is a crystal lattice filter?
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For single-sideband phone emissions, what would be the bandwidth of a good crystal lattice filter?