Overall Context

These are datasheets/catalog excerpts from a manufacturer of ceramic filters, specifically designed for communication equipment. They describe different series (CFUKG_X, CFUKG_X, CFUKG) of SMD (Surface Mount Device) ceramic filters centered around a nominal frequency of 455kHz.

1. CFUKG Series (Document 1 - pages 1-2)

️· Key Features:
- Small size (4.0mm thickness)
- Suitable for automatic placement
- Reflow solderable
- Input/Output Impedance: 1500 ohms
️· Specifications (for CFUKG455KE4A-R0):
- Center Frequency (fo): 455kHz ± 1.5kHz
- 6dB Bandwidth: fn ± 7.5 kHz min.
- Stop Bandwidth: fn ± 17.5 max.
- Stop Band Attenuation: 27 dB min.
- Insertion Loss: 6.0 dB max.
- Ripple: 1.0 dB max.
- GDT Deviation: Not Specified.

2. CFUKG_X Series (Document 2 - pages 1-2)

️· Key Features: Same as CFUKG Series.
️· Specifications (for CFUKG455KE4X-R0):
- Center Frequency (fo): 455kHz ± 1.5kHz
- 6dB Bandwidth: fn ± 7.5 kHz min.
- Stop Bandwidth: fn ± 17.5 max.
- Stop Band Attenuation: 27 dB min.
- Insertion Loss: 6.0 dB max.
- Ripple: 1.0 dB max.
- GDT Deviation: 25.0 µs max.

3. CFUKG_X Series (Document 3 - pages 1-2)

️· Key Features: Same as CFUKG and CFUKG_X Series.
️· Specifications (for CFUKG455KE4X-R0):
- Center Frequency (fo): 455kHz ± 1.5kHz
- 6dB Bandwidth: fn ± 7.5 kHz min.
- Stop Bandwidth: fn ± 17.5 max.
- Stop Band Attenuation: 27 dB min.
- Insertion Loss: 6.0 dB max.
- Ripple: 1.0 dB max.
- GDT Deviation: 25.0 µs max.

KEY DIFFERENCES & SUMMARY TABLE

Feature	CFUKG Series	CFUKG_X Series	CFUKG_X Series
Series Name	CFUKG	CFUKG_X	CFUKG_X
GDT Deviation	Not Specified	25.0 µs max	25.0 µs max
Overall	Baseline filter	Improved characteristics for digital comms	Improved characteristics for digital comms

Important Notes & General Observations

️· 'fn': This represents the nominal center frequency (455kHz) and is used in defining the bandwidth and stopband specifications.
️· Similarities: All three series share many specifications (center frequency, 6dB bandwidth, stop bandwidth, attenuation, insertion loss, ripple, input/output impedance).
️· GDT (Group Delay Time): GDT is a critical parameter for digital communication systems. It indicates how much delay varies across the passband frequency. Lower GDT values are generally desirable, meaning more consistent delay. The series listed have significant improvements in this metric.
️· Application: The CFUKG_X series are targeted toward narrowband digital communication applications because they offer improved performance characteristics like GDT.