From CRPA to RTK: Why RF Passive Components Still Matter in High-Precision GNSS

When discussing GNSS, RTK, or advanced positioning systems, most attention naturally goes to antennas, RF chipsets, algorithms, and signal-processing technologies.

But there is another part of the signal chain that is often overlooked:

RF passive components.

Filters, baluns, transformers, power dividers, couplers, and matching networks do not perform positioning calculations. However, they directly affect how accurately and consistently RF signals are transferred through the system.

This becomes particularly important as GNSS receivers evolve from single-channel architectures toward multi-antenna, multi-channel and high-precision systems.

From GNSS Reception to Controlled Reception

CRPA, or Controlled Reception Pattern Antenna, is one example of this evolution.

Public information from the European Space Agency (ESA) describes CRPA technology as using multiple antenna elements and beamforming techniques to control the reception pattern and reduce the impact of interference arriving from specific directions.

The basic idea is relatively straightforward:

Instead of treating all incoming signals equally, the receiver uses spatial information to distinguish useful signals from unwanted ones.

But once multiple antenna elements and RF channels are introduced, system requirements become more demanding.

Each RF channel needs to maintain reasonably consistent:

• Amplitude

• Phase

• Impedance

• Insertion loss

• Frequency response

Even relatively small differences between channels can become important when signals are processed together.

This is where passive RF components become more than just supporting parts.

Why RTK Places More Emphasis on RF Signal Quality

RTK (Real-Time Kinematic) positioning uses carrier-phase measurements together with correction information to achieve much higher positioning accuracy than conventional standalone GNSS.

Public technical materials from GNSS manufacturers and ESA describe carrier-phase measurements as an important foundation of high-precision GNSS positioning.

In practical terms, the receiver is no longer concerned only with:

“Can I receive the satellite signal?”

It also needs to consider:

“How accurately and consistently can I preserve the signal information throughout the RF chain?”

That makes parameters such as insertion loss, return loss, phase response, channel-to-channel consistency and out-of-band rejection increasingly relevant.

A few tenths of a decibel may not sound significant when looking at a single component.

But when multiple components and multiple RF channels are combined, their individual characteristics can accumulate into a measurable system-level difference.

Where Does a Balun Fit In?

A balun is a good example of a small component performing an important RF function.

The name comes from balanced-to-unbalanced transformer.

Depending on the application, a balun can be used for:

• Single-ended to differential conversion

• Differential to single-ended conversion

• Impedance transformation

• Common-mode signal suppression

• RF interface matching

Many modern RF ICs and converters use differential architectures, while antennas, coaxial cables, test equipment and other RF interfaces frequently use single-ended 50 Ω connections.

The balun provides the interface between these two worlds.

For this reason, selecting a balun should not simply be a matter of checking its operating frequency.

Engineers may also need to look at:

Insertion Loss | Amplitude Balance | Phase Balance | Return Loss | Impedance | Common-Mode Rejection

For multi-channel RF architectures, consistency can be just as important as the nominal specification of an individual device.

Passive Components Can Influence the Entire RF Chain

Another example is the RF filter.

GNSS receivers operate in a crowded electromagnetic environment. Strong signals outside the desired frequency band can potentially overload or disturb sensitive receiver front ends.

A properly designed filter can improve selectivity and help protect the receiver from unwanted signals.

However, filtering always involves trade-offs.

Higher selectivity may come with additional insertion loss. A sharper response can also introduce phase characteristics that need to be considered in some applications.

The same principle applies to power dividers and couplers.

When a multi-channel architecture requires one signal to be distributed across several paths, the divider's amplitude and phase balance become part of the overall system performance.

In other words:

A passive component does not process the positioning algorithm, but it can influence the quality of the signal that reaches the algorithm.

From Component Specifications to System-Level Performance

This is why RF engineers increasingly need to look beyond a single headline specification.

For a filter, insertion loss alone may not tell the whole story.

For a balun, operating frequency alone is not enough.

For a power divider, the number of ports does not fully describe its usefulness.

The real question is how the component behaves inside the complete RF architecture.

For GNSS, RTK, satellite communications, radar and other multi-channel RF applications, engineers may need to consider:

• Frequency coverage

• Insertion loss

• Return loss / VSWR

• Amplitude balance

• Phase balance

• Isolation

• Power handling

• Temperature stability

• Package size

• Manufacturing consistency

This becomes even more important when a design moves from prototype to volume production.

A component that performs well in one laboratory setup may still need to demonstrate consistent performance across temperature, production batches and different RF channels.

A Practical Perspective from Jieying Communication

At Jieying Communication, our passive RF portfolio includes baluns and RF transformers, filters, power dividers, couplers and other microwave passive components.

For balun applications in particular, the focus is not simply on achieving a specified frequency range.

The more important question is how the device fits into the complete RF signal chain — whether it is being used for differential interfaces, impedance transformation, RF front-end matching or multi-channel architectures.

This engineering perspective also applies to our filter and divider products.

Rather than viewing a passive component as an isolated part number, it is often more useful to evaluate it according to the requirements of the complete system.

The Smallest Components Can Still Have System-Level Impact

As positioning technology develops from conventional GNSS toward RTK, multi-antenna receivers and controlled reception architectures, RF systems are becoming increasingly sensitive to signal consistency.

That makes the role of passive components worth revisiting.

The performance of an RF system is not determined by the active devices alone.

The filters, baluns, dividers, couplers, matching networks and interconnects surrounding those devices all contribute to the final signal quality.

Sometimes, the difference between a stable RF design and a difficult one comes down to components that are only a few millimeters in size.

And that is exactly why passive RF components still matter.

Technical note: This article discusses CRPA, RTK and RF passive components from a general RF engineering perspective based on publicly available technical information. It does not describe or reproduce specific military system designs or implementation details.