Ultrasound imaging with high resolution and large field of depth has been increasingly adopted in medical diagnosis, surgery guidance and treatment assessment because of its relatively low cost, non-invasive and capability of real-time imaging. There is always a tradeoff between the resolution and depth of field in ultrasound imaging. Conventional ultrasound works at a particular frequency, with −6 dB fractional bandwidth of < 100%, limiting the resolution or field of depth in many ultrasound imaging cases.
In this paper, a bi-frequency co-linear array covering a frequency range of 5 MHz-20 MHz was investigated to meet the requirements of resolution and depth of field for a broad range of ultrasound imaging applications. As a demonstration, a 31-element bi-frequency co-linear array was designed and fabricated, followed by element characterization and real time sectorial scan (S-scan) phantom imaging using a Verasonics system.