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Power Combining in PCB Design

Published Date
Author Cadence PCB Solutions

Key Takeaways

  • Power combining is used to increase the power of a signal by combining inputs from multiple sources.

  • The power combining method depends on the application's requirements, whether the goal is to increase output power, improve signal reception, enhance energy storage, or optimize power distribution.

  • Power combining techniques can be applied in PCB design, especially in RF and microwave applications, where combining multiple signals or amplifying power is necessary.

RF balun in comparison with match head

A balanced-to-unbalanced (Balun) transformer is a device for power combining.

Power combining is used to increase the power of a signal by combining inputs from multiple sources. Power combining methods can include techniques such as adding or multiplexing signals coherently to achieve higher power levels, improving the overall efficiency and performance of the system. The technique is commonly used in electronics, telecommunications, satellites, and radio frequency (RF) engineering. Here are some common types of power combiners:

Common Types of Power Combiners

Balanced-to-Unbalanced (Balun) Transformer

Combines signals in a balanced manner; converts single-ended signals into balanced signals

Wilkinson Power Combiner

Combines two input signals into one output with minimal loss; based on quarter-wavelength transmission lines and often used in balanced microwave and RF systems

Hybrid Ring Combiner (Rat-race Coupler) 

Combines multiple input signals into one output; commonly used in balanced circuits

Resistive Power Combiner

Combines the power of input signals using resistors; used for equally combining power; less efficient than other types.

Coupled-Line Power Combiner

Uses transmission lines that are closely coupled to combine power; types include Lange couplers and branchline couplers; used in applications requiring high isolation and compact size.

Magic Tee (E-Hybrid) Combiner

Combines power and based on the E-plane and H-plane junctions; used in various microwave applications

Quadrature Hybrid Combiner (90-Degree Hybrid)

Combines two signals with a 90-degree phase difference; used in phase-combining applications, such as in phased array antennas.

Directional Coupler

Couples power from one transmission line to another; used in applications requiring monitoring or sampling of RF signals

Multiport Combiners

Combines power from more than two ports; used in complex RF systems where multiple input or output signals need to be combined

Power combining devices come in various forms to facilitate the aggregation of multiple signal sources for increased output power. The choice depends on the specific application, signal requirements, and the desired output power levels.

Power Combining Methods

Power combining can be achieved through various techniques, including passive and active methods. Each method has its advantages and limitations, making the choice of power combining technique dependent on the specific application and requirements. Some common methods are:

  • Antenna Array Power Combining: To transmit or receive signals, antenna arrays use multiple antennas. The outputs of these antennas can be combined to achieve directional radiation patterns or to improve the overall signal strength.

  • Amplifier Power Combining: Solid-state power amplifiers are often combined in RF and microwave systems to increase the overall output power, which is particularly important in radar and wireless communications applications. Amplifiers can be combined in parallel, series, or other configurations to achieve the desired power output.

  • Parallel Battery Power Combining: In applications with higher voltage or longer battery life, multiple batteries can be combined in parallel to increase the total capacity. This application is commonly used in electric vehicles and backup power systems.

  • Signal Combiners and Splitters: In electrical and RF engineering, signal combiners and splitters are employed to combine or split signals. Combiners merge multiple signals into a single output, while splitters divide a signal into multiple outputs. These devices are used in various applications, including cable television distribution and RF communication systems.

  • Power Management Systems: In power distribution and management systems, power combining is used to manage and distribute electrical power efficiently. Power from various sources, such as renewable energy sources and grid power, can be combined to meet the energy demands of a facility.

  • Phased Array Radar Systems: In radar systems, phased array antennas use phase shifting to combine signals from multiple antenna elements, which enables electronically steering the radar beam without physically moving the antenna.

  • Load Balancing in Data Centers: In data centers and server farms, power combining techniques can be used to balance the load across multiple servers or power sources, ensuring efficient use of resources and redundancy in case of failure.

The specific method of power combining used depends on the application's requirements, whether the goal is to increase output power, improve signal reception, enhance energy storage, or optimize power distribution. Combining techniques can also impact the system's efficiency, reliability, and cost.

Application of Power Combining Techniques in PCB Design

Power combining techniques can be applied in PCB design, especially in RF and microwave applications, where combining multiple signals or amplifying power is necessary. Here are some considerations for power combining in PCB design:

PCB Layout and Traces

The optimal PCB layout ensures proper power combining. High-frequency RF and microwave signals require controlled impedance transmission lines and low-loss materials. The traces carrying signals to be combined should have consistent widths and characteristic impedances.

Component Placement 

Careful placement of components, including amplifiers, filters, and power dividers, can reduce signal losses and improve power combining. Components should be positioned to minimize transmission line lengths and reduce signal path impedance.

Power Dividers/Combiners 

RF power dividers and combiners are passive components that split or combine RF signals. These can be integrated directly into the PCB design.

Balun Transformers

Baluns (balanced-to-unbalanced transformers) are often used to combine signals in a balanced manner. They convert single-ended signals into balanced signals, which can be combined or split as needed. Baluns can be integrated into the PCB design as surface-mounted devices.

Isolation and Crosstalk Mitigation 

When signals are combined, minimizing crosstalk between signal paths is essential. You can use proper ground planes, shielding, and well-designed layout techniques that reduce interference between combined signals to achieve this.

Impedance Matching

Proper impedance matching is crucial in power combining to minimize signal reflections and losses. Impedance matching networks, such as quarter-wave transformers, can be designed into the PCB layout to match the source and load impedances with the combiner.

High-Quality Substrates

You should select a high-quality PCB substrate material with low dielectric loss for RF and microwave applications. FR-4 is common for lower frequencies, but higher-frequency designs might require specialized materials like Rogers or Taconic substrates.

Filtering 

Depending on the application, you might need filters to remove unwanted harmonics or interference. Filters can be integrated into the PCB design to improve signal quality before power combining.

Temperature Considerations 

In high-power applications, thermal management is crucial. You should ensure that the PCB layout allows for efficient heat dissipation and use appropriate heat sinks or cooling solutions for power amplifier components.

Testing and Simulation 

Before finalizing the PCB design, perform simulations and testing to ensure the power combining setup meets the desired specifications for signal gain, power levels, and impedance matching.

Cadence Has the PCB Tools You Need

Power combining in PCB design requires careful consideration of electrical and mechanical factors. The choice of specific components, layout, and materials should align with the system's requirements, such as the desired power output, frequency range, and signal quality. Additionally, working with specialized PCB design tools is essential to achieve optimal results.

Cadence has the PCB Design and Analysis Software tools you need, including the  OrCAD PCB Designer. Leading electronics providers rely on Cadence products to optimize power, space, and energy needs for a wide variety of market applications. To learn more about our innovative solutions, talk to our team of experts or subscribe to our YouTube channel.