Low PIM Diplexers

A Low PIM (Passive Intermodulation) diplexer is a passive RF component designed to either split or combine two frequency bands with minimal interference. It isolates high and low frequency bands to enable multiple signals to travel over a single path while ensuring extremely low levels of intermodulation distortion, which is critical in high-performance RF systems.

Low PIM is essential in systems where multiple high-power signals share components, such as:

• Cellular base stations (4G/5G)

• DAS (Distributed Antenna Systems)

• Satellite and radar systems
  Uncontrolled PIM can cause self-interference, degraded signal quality, and reduced system capacity.

PIM is caused by:

• Nonlinearities in passive materials (e.g., ferrous metals, poor-quality plating)

• Mechanical junctions (e.g., loose connectors, poor solder joints)

• Contaminants like dirt or corrosion at interfaces

PIM is typically measured in dBc (decibels relative to the carrier), with two tones injected at high power (usually 2 × 43 dBm = 20 W), and the intermodulation products (e.g., 3rd-order) are measured.

• Low PIM rating: –150 dBc or better (often –160 dBc in critical applications)

• Cellular infrastructure (e.g., BTS, RRH)

• Distributed Antenna Systems (DAS)

• In-building wireless systems

• Public safety and critical communications

• Multi-band antenna systems

To reduce PIM, manufacturers use:

• High-purity, non-ferromagnetic metals (e.g., aluminum, silver-plated brass)

• Low-PIM dielectric materials

• High-quality connectors (like DIN 7/16 or 4.3-10)

• Silver plating to reduce surface resistance and non-linear junctions

• PIM rating: –150 dBc or better

• Insertion loss: ≤ 1 dB (usually lower)

• Isolation: ≥ 60 dB between ports

• Return loss: > 18 dB (VSWR < 1.3:1)

• Power handling: Up to 300 W or more (depends on application)

• Use Low PIM-rated cables and connectors

• Ensure tight, torque-specified connections

• Avoid bending or straining cables

• Keep connectors clean and corrosion-free

• Avoid using ferrous tools near the RF path

When selecting a Low PIM (Passive Intermodulation) diplexer, you’re often working in high-performance RF systems where signal clarity and reliability are critical — especially in cellular infrastructure, DAS, public safety, and multi-band antenna systems.

Here are the key parameters you should consider:

1. PIM Performance (Passive Intermodulation Level)

• Definition: The level of unwanted intermodulation products generated within the passive diplexer itself.

• Measured in: dBc (decibels below carrier)

• Target:

  • –150 dBc or better (standard)

  • –160 dBc or better (premium systems)

• Why it matters: PIM causes self-interference, reduces signal-to-noise ratio, and limits system capacity—especially in high-power, multi-carrier systems like 4G/5G.

2. Frequency Bands

• Definition: The two (or more) frequency ranges the diplexer separates or combines.

• Why it matters: Must match the Tx/Rx bands or co-located services (e.g., 700 MHz and 2600 MHz in LTE/5G systems).

• Tip: Choose a diplexer specifically designed for your exact band pairing to ensure proper filtering and isolation.

3. Bandwidth (Per Port)

• Definition: The width of each passband the diplexer supports.

• Why it matters: Needs to accommodate the entire operating band including any carrier aggregation or channel overlap.

4. Insertion Loss

• Definition: The amount of signal attenuation introduced by the diplexer in each passband.

• Typical Values:

  • < 0.5 dB (excellent)

  • < 1 dB (good)

• Why it matters: Lower insertion loss = better signal strength, less need for amplification, and improved link budget.

5. Isolation Between Ports

• Definition: The attenuation between the two frequency bands’ signal paths.

• Typical Values:

  • ≥ 50–60 dB is desirable

• Why it matters: High isolation prevents cross-band interference, especially in shared-antenna systems.

6. Return Loss / VSWR

• Definition: A measure of how well the diplexer is impedance-matched to your system (typically 50 ohms).

• Typical Values:

  • Return loss > 18 dB

  • VSWR < 1.3:1

• Why it matters: Poor return loss causes signal reflections, degrades performance, and increases the risk of PIM.

7. Power Handling

• Definition: The maximum RF power the diplexer can handle per port.

• Typical Values:

  • Up to 300 W (for DAS and macro cells)

  • Lower for small cell or indoor applications

• Why it matters: Ensure the diplexer can safely handle peak and average power levels without overheating or generating PIM.

8. Connector Type and Quality

• Common Options:

  • 7/16 DIN (rugged, high power)

  • 4.3-10 (compact, low PIM, modern systems)

  • N-type (lower power, common in indoor)

• Why it matters: Connector quality and torque affect both PIM and signal integrity. Use Low PIM-rated connectors and cables.

9. Environmental Ratings

• Definition: Ability to operate in harsh conditions (temperature, moisture, vibration).

• Look for:

  • IP65/IP67 for outdoor use

  • Wide temp range (e.g., –40°C to +85°C)

• Why it matters: Especially important in outdoor, rooftop, or tower-mounted deployments.

10. Mechanical Size and Mounting Options

• Why it matters: In dense rack or antenna environments, size and weight can be critical.

• Tip: Look for compact, lightweight, and mounting-flexible designs if needed.

11. Certification and Compliance

• Why it matters: Especially for public safety or commercial wireless infrastructure, diplexers may need to comply with:

  • RoHS/REACH

  • Carrier-grade requirements

  • UL, FCC, CE, or regional telecom regulations

12. Customizability

• Why it matters: For non-standard or multi-band deployments, you may need:

  • Custom frequency pairs

  • Tri-/quad-plexer configurations

  • Special packaging or connector options

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