Ceramic Diplexers

A ceramic diplexer is a compact RF component made from high-permittivity ceramic materials, designed to split or combine two frequency bands with high isolation and minimal size. It uses ceramic resonators or dielectric waveguides for precise filtering.

Ceramic diplexers use ceramic-based resonant structures to create two frequency-selective paths:

• One for lower-frequency band (e.g., Band 1)

• One for higher-frequency band (e.g., Band 2)
  They allow both bands to share a single antenna or signal path while maintaining high isolation between them.

• Ultra-compact size (ideal for portable and embedded devices)

• Stable performance over temperature

• High isolation between bands

• Low insertion loss for their size

• No tuning required (factory-calibrated)

• Suitable for mass production

Ceramic diplexers are widely used in:

• Mobile phones and tablets

• Wi-Fi modules

• Bluetooth + GPS combo modules

• IoT devices

• Wearables

• Low-power RF front ends

Most ceramic diplexers operate between 300 MHz and 6 GHz, targeting wireless communication standards like:

• LTE

• 5G NR

• Wi-Fi (2.4/5 GHz)

• GNSS (GPS, GLONASS, Galileo)

Key parameters include:

• Center frequencies of each band

• Bandwidth

• Insertion loss (typically 0.5–1.5 dB)

• Isolation between bands (typically 30–60 dB)

• Return loss / VSWR

• Temperature stability

• Fixed frequencies — not tunable

• Limited power handling (suitable for low-power applications)

• Susceptible to mechanical damage if not handled properly

• Narrower bandwidth compared to cavity or LC filters

Very small — often SMD packages as small as 1.6 × 0.8 mm or even smaller. This makes them ideal for space-constrained RF designs.

They are relatively thermally stable, especially when built using temperature-compensated ceramic materials. However, minor frequency shifts can still occur under extreme conditions.

Ceramic diplexers offer a strong balance between size, performance, and cost. Compared to LC diplexers, they provide higher Q, better temperature stability, and more consistent performance. Compared to cavity diplexers, they are much smaller and cheaper but support lower power levels and narrower bandwidths. This makes ceramic diplexers ideal for compact, low-power wireless devices.

Yes, many manufacturers offer custom ceramic diplexers for specific frequency combinations, bandwidths, or package sizes. However, customization typically requires higher minimum order quantities (MOQs) and longer lead times compared to standard off-the-shelf parts. Because ceramic diplexers are fixed-frequency devices, customization is done at the design and manufacturing stage.

Most ceramic diplexers are internally matched to 50 ohms and do not require additional matching components. However, depending on the antenna, PCB layout, or nearby RF components, small external tuning elements (such as capacitors or inductors) may be used to optimize overall system performance.

Most commercial ceramic diplexers are RoHS and REACH compliant. Many parts are qualified for consumer and industrial temperature ranges (–40°C to +85°C), and some are suitable for automotive-grade applications depending on the manufacturer. Always check the datasheet for environmental, reliability, and qualification standards.

Key PCB layout recommendations include:

• Keep RF traces as short as possible

• Use controlled-impedance (50-ohm) microstrip or coplanar waveguides

• Place the diplexer close to the antenna or RF front-end

• Provide a solid ground plane with sufficient grounding vias

Good layout is critical to achieving the specified insertion loss and isolation.

When selecting a ceramic diplexer, especially for compact RF systems like smartphones, IoT devices, Wi-Fi modules, or GNSS receivers, it’s crucial to balance electrical performance, mechanical size, and cost. Here’s a detailed breakdown of the key parameters to consider:

1. Center Frequencies (Band 1 & Band 2)

• Definition: The two frequency bands the diplexer supports (e.g., 1575 MHz for GPS and 2.4 GHz for Bluetooth).

• Why it matters: You must choose a diplexer with precise band matching to your system’s RF signals.

• Tip: Frequency bands are fixed in ceramic diplexers—select the exact part number for your bands.

2. Bandwidth (Per Port)

• Definition: The usable range around each center frequency that the diplexer passes with minimal attenuation.

• Why it matters: Must be wide enough to handle your signal or modulation scheme.

• Example: A Wi-Fi diplexer may need ≥ 80 MHz bandwidth at both 2.4 GHz and 5 GHz.

3. Insertion Loss

• Definition: Signal attenuation in the passband, measured in dB.

• Typical Values:

  • 0.5 to 1.5 dB for most ceramic diplexers

• Why it matters: Lower insertion loss = better signal strength and link budget.

4. Isolation Between Bands

• Definition: Attenuation of one band in the other band’s path (e.g., GPS signal rejected from the Bluetooth path).

• Typical Values:

  • 30–60 dB

• Why it matters: Prevents cross-talk and self-interference, especially in co-located radio systems.

5. Return Loss / VSWR

• Definition: Indicates how well the diplexer matches the system impedance (typically 50 ohms).

• Target Values:

  • Return loss > 14 dB

  • VSWR < 1.5:1

• Why it matters: Poor return loss causes reflections, reducing efficiency and increasing power loss.

6. Power Handling

• Definition: Maximum RF power (usually CW) the diplexer can handle without failure or performance degradation.

• Typical Range:

  • 0.5 W to 2 W (depending on part size)

• Why it matters: Ensure it’s suitable for your transmit power level, especially in Wi-Fi or Bluetooth applications.

7. Temperature Stability

• Definition: Frequency and performance stability over temperature changes.

• Why it matters: Ceramic materials are stable, but some frequency drift may occur.

• Tip: Choose components rated over –40°C to +85°C or higher for industrial use.

8. Package Size and Mounting Type

• Definition: Physical footprint and soldering method (usually SMD).

• Common Sizes:

  • 1.6 × 0.8 mm (1608)

  • 2.0 × 1.25 mm (2012)

• Why it matters: Must fit your PCB layout, especially in miniaturized designs.

9. Quality Factor (Q)

• Definition: Indicates how sharp or selective the filter is.

• Why it matters: Higher Q = better selectivity, lower loss—but can be more sensitive to tolerance variations.

To place an order for ceramic diplexers please contact us and we will help you!