High-Frequency Waveform Generation Using Optoelectronic Switching in Silicon

Abstract

A ,love[ approach to provide redundancy in an N-way MESFET switch has been invented and realized with monolithic microwave integruted circuit technology. This switch circuit uses series and shunt FETs con-$gured in a manner toprevent failure of the switch even i f several FETs fail. For example, a SPDT redundant switch is capable of providing 1.3-dB insertion loss and return loss and isolation better than 20 and 35 dB, respectively, over dc to 12 GHz, even if25 % of the FETs fail in euch arm.

Voltage pulse forming dynamics in a transmission line section employing photoconductive charging and discharging

“…This was attributed to drift velocity saturation, as discussed in [2]. = 1,2 (7) where in the present case, w1 = 0.7, wg = 0.3, t,l = 0.5 and t r 2 = 2.5, with t in nanoseconds.…”

“…The function gi(t) = gioexp(-r1/7zff) and (7) thus have equal time integrals when evaluated over 0 < t < 00.…”

“…The value of 7zff is thus calculated to be 22 for the present device, using (8) along with the values of w1, W Z , t,l and t r 2 used in (7). 7-2"' cannot in general be used in (4) to determine the required 7-3, since the latter equation was derived on the basis of the time required for g1 (t) to decay to .025glo; this time will differ between the decay functions governed by 7-2" and that given by (7), so that an evaluation of the latter equation is needed to determine the necessary 73.…”

“…Various devices have been demonstrated for pulse-forming applications over a broad range of voltage levels and pulsewidths [ 11- [6]. Other charged line applications include microwave burst generation by frozen wave structures [7], and by use of the line section as a resonator [8]. Use of a charged line enables the formation of short rectangular pulses while employing photoconductors with long recovery times; the latter feature is necessary to make the most efficient use of the optical pulse energy.…”

Analysis of waveform generation utilizing striplines and photoconductive switches

“…Real switches behave in a much less ideal fashion. A typical output from a bulk type avalanching photoconductor is shown in Figure lb Several methods for generation of more complex waveforms have been suggested and a few have been tested (2)(3)(4)(5)(6)(7). However, little has been written on the limitations of these circuits imposed by the non-ideal switch.…”