Assessment of Bandwidth Potential with Optenni Lab

Posted by Nisatuz Jahra | 3 July 2025

From this article, you will learn about:

• Antenna assessment method: bandwidth potential and why to use it?
• How bandwidth potential is calculated
• How to use bandwidth potential in practice

Introduction

Antennas are characterized by many parameters, of which bandwidth is of especial importance. All communication standards must operate within their allocated frequency bands, which must be well catered by the antenna. An important figure of merit in this study is the so-called bandwidth potential.

An important figure
of merit in this
study is the
so-called bandwidth
potential.

The bandwidth potential of an antenna describes how well it could perform across a range of frequencies if matched using an ideal, two-component lossless matching network. As explained in [1], this assessment is highly valuable for antenna designers, as it helps determine whether a mechanical design is worth taking forward for prototyping and physical implementation, especially when targeting specific applications or wireless standards.

This blog explores how bandwidth potential is calculated using Optenni Lab, and how the tool assists in identifying optimal operating bands for antenna designs. For a broader view of how the concept of bandwidth potential contributes to antenna analysis workflows in Optenni Lab, we recommend reading our earlier blog post, “Exploring Antennas with Optenni Lab”.

Understanding the Bandwidth Potential Graph

Let’s begin by directly studying an Optenni Lab output graph of the bandwidth potential calculation. The example graph below (in Figure 1) shows the bandwidth potential of an example antenna at Port 1, using a 6 dB reference matching level (the level of return loss the antenna must achieve), across a frequency range from 0 to 6 GHz.

Figure 1: Optimized symmetric bandwidth of a single-port antenna.

Let’s interpret the key features. This antenna clearly has:

• Strong performance near 2 GHz: The bandwidth potential peaks at around 1200 MHz, indicating the antenna is easily matched with a wide bandwidth in this region.
• Dip around 3 GHz: A noticeable drop shows that the antenna is more difficult to match with a wide bandwidth here, with bandwidth potential falling below 290 MHz.
• Second peak near 4.5 GHz: Another region of high bandwidth potential (~900 MHz), immediately suggesting the antenna is suitable for dual-band operation.
• Lower edge behavior: As usual, the antenna is electrically small at lower frequencies (higher wavelengths) where we can expect it to have very narrow bandwidth characteristics, eventually reaching zero.
  Upper edge behavior: The bandwidth potential falls linearly to zero near the lower and upper ends of the frequency range, which is due to the absence of impedance data beyond the upper boundaries.

What it means for designers

This type of analysis helps designers quickly understand which frequency ranges are naturally supported by the antenna and where additional matching or redesign may be necessary.

How Optenni Lab calculates the bandwidth potential

From a theoretical perspective, bandwidth potential is calculated using RF matching theory within a given frequency range. The antenna is treated as a complex, frequency-dependent load:

Z_ant(f)=R(f) + jX(f)

Based on circuit theory, any such load Z_ant(f) can be perfectly matched to a reference impedance (usually 50 Ω) with only two matching components (inductor or capacitor), either in series or in shunt. But this theory holds only for a single frequency, which is of course the narrowest frequency band imaginable.

To calculate the bandwidth potential, at each frequency point, Optenni Lab automatically synthesizes an ideal two-component lossless matching circuit to conjugately match the antenna to a system impedance (usually 50 Ω). It then computes the symmetric bandwidth, i.e. the frequency range symmetrically around the calculation frequency where the return loss stays better than the chosen reference level (e.g., 6 dB in the example). This process is repeated for all frequencies, resulting in a graph that shows bandwidth potential across the frequency spectrum.

In other words, if the original S- parameter or impedance data has 1000 frequency points, the calculation of the bandwidth potential is equivalent to calculating the conjugate matching task 1000 times and recording the obtained symmetric bandwidth for each obtained matching circuit. Note that, for each frequency the obtained matching circuit is different.

In addition to the standard conjugate matching approach, Optenni Lab also offers the calculation of Optimized Bandwidth Potential. As explained in [2], in this method, the software determines the optimal two-component match at each frequency point that yields the maximum obtainable symmetric bandwidth around the center frequency, while still respecting the specified return loss reference level. This provides a more fundamental estimate of the antenna’s true bandwidth capability, independent of any predefined system impedance.

Although the calculation process of bandwidth potential is complex and involves many steps in theory, Optenni Lab simplifies it to just a few clicks, delivering results within seconds (see Figure 2).

Figure 2: Steps to process the assessment of bandwidth potential in Optenni Lab. On the right plot, both approaches of assessment have been illustrated. Result of Standard conjugate matched in blue, Optimized symmetric bandwidth in green.

Detailed View: Conjugate Match to Termination Impedance and Symmetric Bandwidth

As mentioned above, Optenni Lab offers two kinds of bandwidth potential assessment:

• Conjugate match to termination impedance
• Optimize symmetric bandwidth

To explore the process further, let’s consider a single-port antenna and analyze how Optenni Lab calculates the bandwidth potential.

Figure 3: S-Parameter data of a single- port antenna (on the left) and standard conjugate matched bandwidth potential of the antenna at a selected frequency 1.73 GHz. This result is also shown in Figure 2.

Figure 3 shows a marker positioned at 1.73 GHz. Optenni Lab always displays the symmetric available bandwidth around the center frequency as the marker value, which in this case is 415 MHz.

Using a 6 dB reference matching level, let’s examine this automatic bandwidth potential assessment result at 1.73 GHz by running a conjugate matching synthesis (see Figures 3-4). At this point, Optenni Lab generates the best combination of a two-component matching circuit, achieving conjugate match and identifying the matched return loss performance.

Figure 4: Conjugate matching at 1.73 GHz to examine the automated result of Bandwidth Potential Assessment.

The result shows that the antenna achieves:

Figure 5: S11 result at 1.73 GHz after conjugate matching around reference level -6 dB.

From this S11 representation, using a reference level of -6 dB, marker L is located precisely at 1.5223 GHz and marker H at 2.255 GHz. This yields a total available bandwidth of 0.7327 GHz (approximately 733 MHz).

Additionally, Figure 5 illustrates the available symmetric bandwidth, defined as twice the minimum distance from the center frequency to the markers. The center frequency of 1.73 GHz is 207.7 MHz away from marker L and 525 MHz from marker H. Consequently, the symmetric bandwidth is calculated, 2X207.7 MHz is roughly 415 MHz as depicted in the figure.

Why Use Symmetric Bandwidth?

Considering a symmetric bandwidth around the center frequency has some key reasons:

• It provides a consistent and objective way to measure performance around each center frequency.
• It reflects real-world usage, since wireless bands (like LTE, Wi-Fi, and 5G) are centered around a specific frequency.
• It aligns with how RF systems are typically designed, balancing performance above and below a central frequency.This can be considered a worst-case scenario, where only the minimum symmetrical frequency band around the center frequency is assumed to be available, extending equally toward both the lower and upper frequency limits.

In the following picture (figure 6), It is illustrated the difference between the S11 results of conjugate matched and maximized symmetric bandwidth around the center frequency 1.73 GHz.

Figure 6: Conjugate matching at the given frequency 1.73 GHz (left) and maximizing optimized symmetric bandwidth around the given frequency 1.73 GHz (right).

Optenni Lab makes bandwidth potential assessment both accessible and efficient. While the underlying process involves detailed matching theory and circuit synthesis, the software automates these steps and presents clear, actionable results. For antenna designers, this is a powerful tool to evaluate and refine antenna concepts before committing to physical prototypes.

While the underlying
process involves
detailed matching
theory and circuit
synthesis, the software
automates these steps
and presents clear,
actionable results.

What predictive value does Bandwidth Potential have?

We have stated many times above that the Bandwidth Potential computation is based on a two-component conjugate matching, which is, in a sense, a quite simple matching approach. Naturally, Optenni Lab supports matching circuits of virtually any complexity. So why not simply use more than two components for a wider band. Should we not get a 5x wider band by using 5x components (that is, ten matching components versus two), right?

Unfortunately, not right!

This matter has been studied extensively in the academia during the heydays of mobile phone development between years 2000 and 2010. A relevant study in [3] analyzed the impact of using more than two components in the matching circuit on return loss and achievable bandwidth. For bandwidth potential estimation, using a two-component lossless matching network offers a practical balance, ensuring realistic results while maintaining an acceptable return loss level.

To emphasis on the statement mentioned above, let’s check some analysis done in [3],

Figure 7: Percentage of the theoretical maximum impedance bandwidth that can be obtained with a resonant antenna having an ideal lossless matching network as a function of the number of resonators in the system. The first resonator (n = 1) represents a resonant antenna. The matching circuit contains n − 1 resonators. And one resonator consists of two circuit elements (inductor or capacitor).

Figure 7 illustrates the relationship between the number of matching resonators and the percentage of the theoretical maximum achievable bandwidth. As shown, using a two-component matching network already provides approximately 60% of the maximum theoretical bandwidth, offering a practical and efficient balance for bandwidth potential assessment. While additional components can further increase the bandwidth to around 90% of the maximum theoretical bandwidth the improvement saturates quickly. This analysis indicates that a maximum of 1.5x bandwidth enhancement with respect to the bandwidth potential result can be achieved by adding more matching components. In other words, if 200 MHz bandwidth is required, but bandwidth potential shows 100 MHz, the required bandwidth will not be reached by using any number of lossless components.

For bandwidth potential analysis, sticking to two-component matching is sufficient and realistic to predict the best-case achievable bandwidth without overestimating due to overcomplicated matching networks. And by multiplying the bandwidth potential by two, you are very close to the theoretical limit which is virtually never reached with real life lossless circuits.

Why did we
mention the word
“lossless” above?

Well, you can always improve matching with losses (in the extreme, try a 50 Ω resistor as your antenna – what a wonderfully wide band, and what a horrible level of useful radiation). In general, the only way to get a good radiation and total efficiency is to minimize Ohmic losses in the process, even when they make the matching for a wide band harder.

Conclusions

Optenni Lab provides antenna designers with an efficient method to assess bandwidth potential using a two-component, lossless matching approach. This ensures realistic bandwidth estimation without the complexity of multi-component matching circuits. While adding more components can slightly improve bandwidth, Optenni Lab’s approach offers a practical balance between achievable bandwidth and design simplicity, supporting faster, more reliable antenna development.

References

[1] J. Villanen, J. Ollikainen, O. Kivekäs, and P. Vainikainen, “Coupling element based mobile terminal antenna structures,” IEEE Transactions on Antennas and Propagation, vol. 54, no. 7, pp. 2142-2153, 2006.

[2] J. Rahola, “Bandwidth Potential and Electromagnetic Isolation: Tools for Analysing the Impedance Behaviour of Antenna Systems,” presented at the European Conference on Antennas and Propagation (EuCAP), Berlin, Germany, March 23-27, 2009.

[3] J. Ollikainen, Matching Circuit and Antenna Structure Effects on the Bandwidth of Impedance Matching, Doctoral Thesis, Helsinki University of Technology, 2004.