FSF-5050 Series · SAW Bandpass Filter
638 MHz SAW Bandpass Filter
FSF-5050-638M
A compact 5.0 × 5.0 mm SMD filter for 638 MHz RF selection in UHF receiver and test equipment designs.
Key Features
Define the Bandwidth and Interface
3 dB Bandwidth
11 MHz typ.
Typical 3 dB bandwidth. Minimum and maximum limits are not provided.
Insertion Loss
2.4 dB typ.
3.5 dB maximum at the 638 MHz center frequency. Not stated across the entire bandwidth.
Amplitude Ripple
0.18 dB typ.
1.0 dB maximum over the 636.5–639.5 MHz ripple test interval.
The ripple test interval 636.5–639.5 MHz is not the 3 dB bandwidth. The typical 3 dB bandwidth is 11 MHz; no minimum or maximum is stated.
Electrical Specifications
Six Key Selection Parameters
Test setup: 50 Ω source and load, with single-ended input and output. The FCom datasheet does not specify device input or output impedance or a uniform measurement temperature for this table.
Scroll horizontally to view all columns.
| Parameter | Min. | Typ. | Max. | Unit | Definition / condition |
|---|---|---|---|---|---|
| Center frequency | — | 638.0 | — | MHz | fc |
| 3 dB bandwidth | — | 11.0 | — | MHz | 3 dB definition; min./max. not provided |
| Insertion loss | — | 2.4 | 3.5 | dB | At fc; not stated across the full bandwidth |
| Amplitude ripple | — | 0.18 | 1.0 | dB | Over 636.5–639.5 MHz (ripple test interval) |
| Operating temperature | −40 | — | +85 | °C | Operating range; not an electrical test condition |
| Storage temperature | −40 | — | +85 | °C | Storage range |
— means not specified, not zero. The ripple interval 636.5–639.5 MHz is not the 3 dB bandwidth. The insertion-loss maximum applies at the center frequency; it is not stated as a limit across the entire 3 dB bandwidth. Typical values are for design guidance. Refer to the FCom datasheet and confirm applicable production limits with FCom.
Typical Applications
Frequency Selection Around 638 MHz
UHF Receiver Filtering
Use the bandpass response to select the signal region around 638 MHz in a UHF receiver. Check occupied bandwidth against the required in-band response.
Receiver Preselector
Evaluate the filter for frequency selection ahead of a receiver stage. Confirm rejection, insertion loss and signal levels in the intended RF chain.
Measurement-Path Filtering
Consider the filter for a 638 MHz measurement path where band selection is required. Validate the complete fixture and its source and load conditions.
Integration Notes
Match the Evaluation Conditions
Test Setup and Device Impedance
The stated performance uses a 50 Ω source and load. These are test conditions, not a declaration of the device impedance. Assess matching requirements using your actual source, load and board parasitics.
Complete Signal Path
Evaluate the required signal bandwidth, ripple tolerance and rejection together. The 11 MHz typical 3 dB bandwidth does not define a guaranteed flat passband. Do not extend the center-frequency loss limit to the full bandwidth.
Package & Pin Assignment
5 × 5 mm, 8-Terminal SMD Package
The FCom drawing specifies a 5.0 × 5.0 mm body and a maximum height of 1.5 mm. The pin assignments at right apply to FSF-5050-638M.
- Body dimensions
- 5.0 × 5.0 mm
- Maximum height
- 1.5 mm
- Package type
- 8-SMD, no lead
Use the dimension drawing in the FCom datasheet for mechanical review. Its plan-view orientation is not explicitly labeled; confirm orientation and the PCB land pattern before layout release. Contact FCom for other pin configurations.
| Pin(s) | Function |
|---|---|
| 2 | Input |
| 6 | Output |
| 1, 3, 5, 7 | Ground |
| 4, 8 | Case ground |
Selection and Design-In Support
Make the Design Requirements Clear
For selection and design-in discussions, provide the required bandwidth and its definition, source and load requirements, operating temperature, sample quantity and expected usage. Reference FSF-5050-638M and confirm the complete ordering code and applicable production specification with FCom.
The model designation alone is not a confirmed complete ordering code.
Engineering Questions
Frequently Asked Questions
Is 636.5–639.5 MHz the filter bandwidth?
No. This is the interval used for the amplitude-ripple specification. The specified 3 dB bandwidth is 11 MHz typical; minimum and maximum 3 dB bandwidth limits are not provided.
Does the 50 Ω test setup specify the device impedance?
No. The datasheet uses a 50 Ω source and a 50 Ω load with single-ended input and output. Device input and output impedances are not specified. Evaluate the filter with your actual source, load and PCB layout.
Where does the insertion-loss specification apply?
Insertion loss is specified at the 638 MHz center frequency: 2.4 dB typical and 3.5 dB maximum. These values are not stated as limits across the entire 3 dB bandwidth.
How should the ground pins be connected?
The FCom datasheet assigns pin 2 to input and pin 6 to output. Pins 1, 3, 5 and 7 are ground; pins 4 and 8 are case ground. Confirm the drawing orientation and land pattern before PCB release.
What information should I include in a design-in inquiry?
Include FSF-5050-638M, the required bandwidth and its definition, source and load requirements, operating temperature, sample quantity and expected usage. Confirm the complete ordering code and applicable production limits with FCom before ordering.