Walsin Technology (Walsin) builds four main RF passive families. Baluns convert between
an unbalanced line and a balanced pair. Filters pass one band and reject the rest. Couplers
tap a known fraction of forward power. Multiplexers split one antenna port into two or more
bands. The RF catalogue holds 457 parts, concentrated on 2.4 GHz and cellular.
What does a balun actually do in an RF front end?
A balun sits between a single-ended 50 Ω line and a differential pair. Most transceiver
ICs present a balanced port. Most antennas, filters and connectors present an unbalanced
one. The balun performs the impedance transformation and the phase inversion in one
component, so you do not need a discrete matching network on each leg.
Walsin’s balun range is 72 parts. The two specification fields that decide the part are the
unbalanced impedance and the balanced impedance. RFBLN20121G8D1T is a 2012 balun covering
1700~2000 MHz with 50 Ω unbalanced and 100 Ω balanced. RFBLN20121G8D0T covers the same
band in the same case size, but presents 50 Ω on both ports. Those are different parts for
different ICs, and the part numbers differ by one character.
Balun applications in the catalogue break down as 32 parts for telecom (2G/3G/4G), 23 for
2.4 GHz Bluetooth, Wi-Fi and Zigbee, eight for 5G Wi-Fi, six automotive, one 5G and one
listed as other.
Which RF filter types does Walsin offer, and for which bands?
Filters are the largest RF family at 235 parts. They split into 110 band-pass, 94 low-pass,
26 balanced, three high-pass and two further band-pass entries under a variant spelling.
Application coverage is dominated by 2.4 GHz Bluetooth, Wi-Fi and Zigbee at 115 parts, then
telecom (2G/3G/4G) at 69 and 5G Wi-Fi at 25.
Here are four real 2.4 GHz parts from the catalogue, compared field by field against a
common reference. The right-hand column states what matches and what does not. None of
these parts is a drop-in for another.
| Walsin part number | Technology | Size | Band | Insertion loss (dB) | Impedance (Ω) | Match / mismatch vs RBBPF1005040A1T |
|---|---|---|---|---|---|---|
| RBBPF1005040A1T | LC band-pass | 1005 | 2400~2500 MHz | 2.5 | 50 | reference part |
| RBBPF1411060A3T | LC band-pass | 1411 | 2400~2500 MHz | 1.1 | 50 | match: filter type, band, impedance · mismatch: 1411 case not 1005, insertion loss 1.1 dB not 2.5 dB |
| RBBPF1411060A38Q1C | LC band-pass | 1411 | 2400~2500 MHz | 1.1 | 50 | match: filter type, band, impedance, insertion loss · mismatch: 1411 case not 1005, different part-number suffix |
| BA11092442AE1T | BAW | 1109 | 2401~2483 MHz | see datasheet | 50 | match: impedance, broad band of interest · mismatch: BAW not LC, 1109 case, narrower 2401~2483 MHz passband, insertion loss not listed in the parametric data |
Source: Walsin product index — https://www.passivecomponent.com/products/ (product
index, not a per-part datasheet).
Read the insertion loss column carefully. Moving from the 1005 part to the 1411 part buys
1.4 dB. On a battery-powered radio that is a real link-budget gain, paid for in board area.
What is the difference between an LC filter, a SAW filter and a BAW filter?
An LC filter is built from printed inductors and capacitors inside a ceramic body. A SAW
filter uses a surface acoustic wave on a piezoelectric substrate. A BAW filter uses a bulk
acoustic wave through a thin-film resonator. Acoustic filters give much steeper skirts.
LC filters give wider bandwidth and better power handling.
Walsin’s acoustic range is small and specific: five BAW parts and three SAW parts. The BAW
set covers narrow bands around the crowded 2.4 GHz region — BA11092442AE1T at
2401~2483 MHz, BA11092350B40E1T at 2300~2400 MHz and BA11092593B41E1T at
2496~2690 MHz. BA14112593B41E1T covers that same 2496~2690 MHz band in a 1411 case
instead of 1109.
The SAW parts are SF11091582GC2T at 1559~1605 MHz, which is GNSS territory,
SF11092350B4004T at 2300~2400 MHz and SF11092595B4108T at 2535~2655 MHz.
Choose acoustic when an adjacent transmitter sits within a few tens of megahertz of your
passband. Choose LC when you need cheap, wide, low-loss rejection of harmonics.
When do I need a coupler rather than a filter?
A coupler does not shape the spectrum. It samples it. A directional coupler takes a fixed,
known fraction of the forward wave and presents it at a separate port, so a power detector
or a closed-loop transmit control can measure output without sitting in the main path.
Reach for one when you need to regulate or verify transmit power.
The coupler family is 17 parts. TFCPL0605B2450T is a thin-film coupler in an 0605 body
covering 2400~2500 MHz with 0.32 dB insertion loss and 14.6 dB coupling. RFCPL1608070P2T
is a broadband cellular coupler in a 1608 body covering 698~2690 MHz, with insertion loss
specified per sub-band: 0.20 dB at 698~960 MHz, 0.22 dB at 1427.9~2170 MHz and 0.25 dB at
2300~2690 MHz.
Two numbers matter. Insertion loss is what the coupler costs you in the main path. Coupling
factor is how much signal reaches the detector. Low insertion loss and high coupling pull
in opposite directions.
What does a diplexer do that two separate filters cannot?
A diplexer combines two bands onto one antenna port while keeping the two paths isolated
from each other. Two independent filters would each load the other’s passband. A diplexer
is designed as a single network, so the low-band arm looks like an open circuit at the high
band and the reverse is also true.
Walsin’s multiplexer family is 116 parts, and the listed entries are diplexers. The obvious
application is dual-band Wi-Fi. AMDIP2520070L4T is a 2520 diplexer combining 2400~2500 MHz
with 5150~5850 MHz for automotive use. AMDIP2012050LP7B1U covers 2400~2500 MHz with
4900~5950 MHz, a wider upper arm that reaches further into the 5 GHz UNII bands.
How many RF parts are actually in Walsin’s catalogue?
- That figure comes from our own extraction of the parametric data, counted part by part.
Walsin’s on-site product counter for RF includes the header row of the underlying table, so
the displayed figure reads one higher than the number of real orderable parts. The same
off-by-one applies to the antenna and MOV counters.
It is a trivial discrepancy on its own. It matters because it tells you the counter is
reporting rows, not parts, and that is worth knowing before you build a sourcing decision
on a headline number from any manufacturer’s website.
Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the extracted RF
data set and can filter it by band, insertion loss, impedance and case size on request.
Frequently asked questions
Can I use a 50 Ω to 50 Ω balun as a plain impedance match?
No. A 50 Ω to 50 Ω balun such as RFBLN20121G8D0T still performs the single-ended to differential conversion. That is its function. If your IC port is already single-ended, a balun adds insertion loss and solves nothing. Match with an LC network instead.
Is a smaller RF filter always worse?
Not always, but there is a consistent trend in this catalogue. The 1005 band-pass part RBBPF1005040A1T specifies 2.5 dB insertion loss. The 1411 parts in the same band specify 1.1 dB. Larger resonator volume gives lower loss. Decide whether the board area is available before you assume the small part is fine.
Do these RF parts have individual datasheets I can link?
Walsin publishes RF documentation through its product index at https://www.passivecomponent.com/products/. We do not hold a per-part PDF map for the RF range in the way we do for MLCC, so we will not publish direct PDF links we cannot verify. Ask us and we will send the current document for a specific part.
What is the difference between a diplexer and a multiplexer?
A diplexer handles two bands. A multiplexer is the general term for two or more. Walsin’s multiplexer family is listed under one category of 116 parts, with the diplexer type carrying the entries we hold. The export provides fields for a third frequency, which is populated as - on the diplexer rows.
Which Walsin RF parts cover automotive applications?
The export marks application at part level. Six baluns and two filters carry an automotive application, and the diplexers we hold — including AMDIP2520070L4T and AMDIP2004L157B1U — are marked automotive. Application marking is not the same as a qualification certificate. Ask for the qualification status of any part before you design it into a vehicle programme.
Can I substitute a BAW filter for an LC filter in the same footprint?
Almost never directly. BA11092442AE1T is a 1109 case; RBBPF1005040A1T is 1005 and RBBPF1411060A3T is 1411. The passbands also differ: 2401~2483 MHz against 2400~2500 MHz. Different footprint, different band edges, different rejection shape. Re-simulate the front end rather than swapping the part.
Does Walsin make RF switches as well?
Yes, a small antenna switch range of nine parts. RFASWA630PTF0E is an SPDT covering 100 MHz~6000 MHz in a 1.1 x 0.7 mm body. RFASWK626PTF0E is an SP4T covering 100 MHz~2700 MHz in 1.1 x 1.1 mm. RFASWB022ATF0E is a DPDT covering 617 MHz~5000 MHz. All three are GPIO-controlled.
Next step
If you are building a 2.4 GHz or cellular front end and need to know exactly which Walsin
RF parts exist for your band, send us the band edges, the impedance at each port and the
board area you have. Venatech Limited will return a filtered list from the 457-part RF data
set with insertion loss, impedance and case size stated field by field. We will not tell you
a part is equivalent to the one you are replacing. We will show you where it differs.
Send us your BOM → · Browse Walsin RF →
Related reading: High-Q, low-ESR MLCC for RF ·
Choosing a 2.4 GHz chip antenna
Cross it yourself. The cross-reference tool takes a single part number or a whole BOM column and returns the Walsin candidates with every field that differs stated plainly — qualification stays with you. Ready stock shows what is held in Hong Kong today, with an RFQ against any line.