Time-domain manipulating of short-time chirps

Broadband chirp-type signals are suitable excitation signals in the measurement of passive frequency-dependent electrical parameters of different objects, including the biological ones (bioimpedance). Using chirp excitation enables to monitor the behavior of objects under study within a wide frequency range by a single measurement cycle. In addition to the simple frequency scaling, chirps are easily scalable in the time domain, too. It makes it possible to generate very short chirps, maintaining their bandwidth at the same time. It is especially important in measurements, where the speed of measurement is important, e.g., in high throughput microfluidic lab-on-chip type devices for monitoring of cells and droplets, or in systems, where low power consumption is unavoidable, e.g., in implantable medical devices. Unfortunately, shortening of chirps reduces the useful energy of excitation and involves the decline of some spectral properties, e.g., flatness, which is an advantage of traditional long chirps. This paper provides a short overview about methods for improving the spectral and energy parameters of short-time chirps.