Reading an RF Filter Part Number by Band

A Walsin RF filter part number decodes its filter type from the prefix, not its exact frequency band. RFBPF, RBBPF and KFBPF are band pass; RFLPF and AMLPF are low pass; RFBPB is balanced; RFHPF is high pass — verified across all 235 real filters in Walsin Technology (Walsin)’s export. The band itself has to come from the Application and Frequency fields, because the numeric code in the part number is not reliable enough to design against.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin’s RF filter parametric export, 235 rows. Every part number below is real and counts are of part numbers, not pieces.

How many RF filters does Walsin actually list?

235, not 470. As with the balun export, Walsin’s RF folder stores the filter data twice — Walsin_Filter.xlsx and FRESH_rf_filter.xlsx — byte-identical, same 235 part numbers, no duplicates inside either file. Summing both files doubles the real count.

Unique to Venatech’s data. Walsin_Filter.xlsx and FRESH_rf_filter.xlsx hold the identical 235 rows, confirmed field by field. 235 is the real figure for this line.

What does the prefix of a Walsin filter part number tell me?

The filter type, with zero exceptions across all 235 parts:

Prefix	Parts	Filter Type
RFBPF	100	Band pass
RFLPF	92	Low pass
RFBPB	26	Balanced
RBBPF	9	Band pass
RFHPF	3	High pass
AMLPF	2	Low pass
KFBPF	1	Band pass

Part number	Prefix	Filter Type	Match / mismatch
RFBPF1608060A1T	RFBPF	Band pass	Match
RFLPF1608060A5T	RFLPF	Low pass	Match
RFBPB1608060ABT	RFBPB	Balanced	Match
RFHPF0605040K0T	RFHPF	High pass	Match
RBBPF1005040A1T	RBBPF	Band pass	Match — a second band-pass prefix, same type
AMLPF16080G9DM1T76	AMLPF	Low pass	Match — automotive variant of RFLPF

The prefix is the one field in a Walsin filter part number that resolves cleanly to a category every time. Three different prefixes map to band pass and two to low pass — vendor variants of the same filter type, not different functions — so match on filter type, not on assuming one prefix per type.

Can I read the exact frequency band from the part number itself?

Not reliably. Some part numbers carry a fragment that looks like a frequency — RFLPF10051G8D0T cuts off around 2025 MHz, and the digits 1G8 sit close to that figure — but the match is approximate, not exact, and it fails outright on the two highest-frequency filters in the file. We checked every part number in the export against its own Frequency column: where a digit-G-digit fragment exists, it lands within 150 MHz of the band’s upper edge on about two-thirds of those parts and misses by 300–1,200 MHz on the rest.

The reliable band signal is the Application field — 2.4GHz BT/WiFi/Zigbee, Telecom (2G/3G/4G), 5G WiFi, GPS/GNSS, MoCA/Docsis — read together with the exact Frequency range next to it.

What is the double-space “Band Pass Filter” defect?

Walsin’s own Filter Type column spells the same value two ways. 110 of 112 band pass filters read "Band Pass Filter" with a double space; the other two read "Band Pass Filter" with a single space. A string filter built for the correctly-spelled single-space version returns 2 parts out of 112.

Those two parts are not a random pair. They are the two highest-frequency filters in the whole 235-row extract:

Part number	Filter Type spelling	Frequency	Application	Category
RFBPF20077G2W0T	Band Pass Filter (single space)	6240–8240 MHz	not given	not given
RFBPF25207G3W1T	Band Pass Filter (single space)	6230–8500 MHz	not given	not given

Unique to Venatech’s data. The two single-space “Band Pass Filter” rows are also the only two of 235 rows with no Application value and no Category (construction) value — every other filter in the file reads LTCC. The spelling defect, the missing application and the missing construction type all land on the identical two parts, which suggests these two were added to the export from a different source than the rest of the 233-row file, not entered by hand one at a time.

Does the four-digit code after the prefix always match the declared size?

No. 15 of the 235 part numbers (6.4%) carry a size code that disagrees with the file’s own Size column:

Part number	Code in part number	Declared Size column	Match / mismatch
RBBPF2010A10T	2010	2012	Mismatch
RFBPF2008A13T	2008	2012	Mismatch
RFBPF2008A40T	2008	2012	Mismatch
RFBPF2009A12T	2009	2012	Mismatch
RFBPF2108AM627Q1C	2108	2012	Mismatch
RFBPF1608060A1T	1608	1608	Match

All 15 exceptions cluster at the 2012 (2.0 × 1.2 mm) size, where the embedded code reads 2008, 2009, 2010 or 2108 instead. A script extracting case size from the part number string alone, rather than from the Size column, misreads 15 real filters.

So how do I actually find a filter for my band?

Filter on Application and Frequency together, then confirm the filter type from the prefix, then confirm the declared Size column rather than the digits embedded in the part number. In that order, the 235-part catalogue resolves cleanly: band pass, low pass, balanced or high pass from the prefix; the real band from Application plus Frequency; the real footprint from Size.

For 2.4 GHz Bluetooth, WiFi or Zigbee, 115 of 117 2.4GHz BT/WiFi/Zigbee-tagged parts use the same part-number letter A after the size code — a useful shortlist signal, not a guarantee, since two Telecom-tagged parts also carry that letter.

Do you hold a Walsin RF filter datasheet?

No. Venatech holds no datasheet and no public datasheet URL for Walsin’s RF filter line. This post is written from the parametric export — part number, series, filter type, size, application, frequency, insertion loss, impedance, attenuation, pin description and construction category. Confirm every figure against Walsin’s own documentation before a design review.

For the related RF lines, see Choosing an RF chip filter by band and Walsin RF baluns: how to pick one. The full range is on the Walsin RF products page.

The short version

Read the prefix for filter type — it is the one field that never mismatches. Read Application and Frequency together for the band — the digits in the part number are not precise enough on their own. Expect 15 of 235 part numbers to disagree with the declared Size column, all at the 2012 footprint. And filter Filter Type on both spellings of “Band Pass Filter,” because the two parts the single-space version returns are the two highest-frequency filters in the whole range.

Send the band, the filter type and the footprint, and Venatech Limited, an authorised Walsin distributor in Hong Kong, will return every real Walsin filter that matches — reading the file the way it actually needs to be read.

Faster than an email. The cross-reference tool takes a pasted list or a spreadsheet and returns Walsin RF part candidates field by field, differences included. Ready stock shows what is physically in Hong Kong, so you can see straight away whether a line is a stock pull or a production slot.

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Frequently asked questions

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