Ultrasound Probe Center Frequency: Specify the Bandwidth and the Test

By ALEVA | California, USA

Engineering question: What must an OEM specify beyond a nominal probe center frequency to make supplier measurements meaningfully comparable?

A frequency label is not an acceptance test

“30 MHz” is a starting point for a design discussion, not a complete acoustic specification. A useful requirement distinguishes the nominal design target, the measured center frequency, the spectral peak and the bandwidth. Evident’s manufacturer explanation lists center frequency, upper and lower −6 dB frequencies, peak frequency, waveform duration and sensitivity as separate characterization outputs. Its example also records the reflector and measurement conditions. This is foundational guidance published in 2019, not a new product announcement. [1]

Write the calculation into the requirement

For an illustrative acceptance convention, normalize the magnitude spectrum to its peak and define the band edges at −6 dB using 20 log10(|A(f)|/|A|max). Let fL and fH be the lower and upper crossings around the intended response band. Then define:

fc = (fL + fH)/2
BW = fH − fL
FBW = 100 × BW/fc

If the hypothetical edges are 24 and 36 MHz, this convention gives a 30 MHz center, a 12 MHz bandwidth and a 40% fractional bandwidth. These are illustrative arithmetic inputs, not measurements of an ALEVA probe. An asymmetric spectrum need not peak at its edge-defined center. For a multi-peaked response, specify which crossings define the intended band rather than silently spanning a deep notch.

Compare the same measurement

We recommend a shared test worksheet stating whether the response is pulse-echo or a one-way measurement; the medium and temperature; reflector geometry and distance; drive waveform; receiver gain and filtering; and the time gate and spectral window. Keep the raw waveform and processing settings with the reported result. This is a proposed engineering workflow, not a claim that every listed item is mandated by a particular standard.

A 2025 peer-reviewed high-frequency transducer study addresses non-destructive testing. It is useful characterization literature, but its application context must not be relabeled as medical validation or evidence for an ALEVA product. [2]

Bandwidth is a design variable, not a universal score

Recent research reinforces the need to report several properties together. Xu and colleagues’ 2026 PMUT study reports center frequency and pulse-echo fractional bandwidth separately, and investigates array arrangement in relation to sensitivity, bandwidth and acoustic uniformity. Those results belong to the authors’ device, not ALEVA hardware. [3]

The OEM decision should therefore compare a joint requirement: spectral response, sensitivity, uniformity and the intended measurement task. Do not accept or reject a design on fractional bandwidth alone. Likewise, a center-frequency label by itself does not establish an imaging-resolution or penetration specification.

Turn capability into a project-specific acceptance plan

ALEVA designs and manufactures custom ultrasound probes with nominal center frequencies up to 30 MHz, tailored to customer requirements. This published capability does not specify a universal bandwidth, sensitivity or clinical performance for every configuration.

For a custom project, agree the nominal target, measured-frequency tolerance, bandwidth definition and limits, test configuration, and evidence required for acceptance before comparing prototypes. The deliverable should be a reproducible measurement and its limitations—not just a frequency printed on a specification sheet.

Discuss the scope through ALEVA’s manufacturing page.

Sources

1. Evident. “Serial Number 1—Looking Back at Our First Transducer.” Manufacturer technical explanation, 17 September 2019. Source.

2. “Self-focusing high-frequency ultrasonic transducers for non-destructive testing applications.” Scientific Reports 15, 8845, 14 March 2025. Peer-reviewed. DOI: 10.1038/s41598-025-93195-y.

3. Xu et al. “High-uniformity miniaturized PMUT array with broadband and high-sensitivity for wearable ultrasound imaging.” Microsystems & Nanoengineering 12, 200, 22 May 2026. Peer-reviewed. DOI: 10.1038/s41378-026-01331-z.