Low‐ringing and reduced‐cost step recovery diode based UWB pulse generators for GPR applications

Abstract

Low‐ringing and reduced‐cost pulse generators for ultrawideband applications using step recovery diode (SRD) have been reported in this article. The circuits generate Gaussian pulses of 170 ps pulse width and a minimal ringing of −22 dB and monocycles of 401 ps duration and high fractional bandwidth of 162%. Cost‐reduction is mainly attributed to the resistive attenuator and single SRD used. Negligible change in circuits' performance was witnessed for repetition rate from 1 to 100 MHz which makes it apt for low to medium range ground penetrating radar applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2289–2294, 2014

A design of UWB reconfigurable pulse transmitter with pulse shape modulation

“…Another approach is using distributed circuit topology based on microstrip transmission line theory and combining different delayed edges of the Gaussian pulse in order to generate higher order Gaussian pulse shapes. Although this method reduces the number of employed components and the manufacturing costs, the produced pulse will have pulse duration about twice of that of the original pulse .…”

“…In the current design, the Gaussian impulse section is driven by a clock signal of 40 MHz PRF and 5 ns rise/fall time and the SRD is selected to have 120 ps transition time and 50 ns MCLT. The conversion efficiency is determined by the physical construction of the SRD . However, the aspects of tuning the physical parameters of the SRD are beyond the scope of this article.…”

“…The pulse width of the generated Gaussian pulse shape can be controlled by the length of the short‐circuited stub. The relation between the pulse width and the length of the employed short circuited transmission line can be expressed by following equations: where V p , C , ε eff , l , and Δt are phase velocity, velocity of light, effective dielectric constant, length of the delay line, and desired time delay, respectively . Shorter pulse duration can be achieved using shorter stub however, this will reduce the pulse amplitude significantly and the ringing effect will increase dramatically.…”

“…Besides, many existing UWB transmitters are capable of producing only a single type of pulse shape with a fixed pulse width. However, creating additional features such as tunable pulse duration or switchable pulse shapes to existing UWB systems is very advantageous . For example, in UWB communication systems the pulse can be seen as a burst of RF energy where each pulse carries one symbol of information and therefore multiple pulse shape generation can provide pulse shape modulation (PSM) which is desirable for encoding data .…”

“…For example, in UWB communication systems the pulse can be seen as a burst of RF energy where each pulse carries one symbol of information and therefore multiple pulse shape generation can provide pulse shape modulation (PSM) which is desirable for encoding data . Recently, reconfigurable UWB transmitters with switchable and tunable output pulse shapes have also been developed .…”