International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / A simplex or ‘passive’ continuous wave and monopulse seeker tracks specific attributes of a target’s radio frequency (RF) radar return in some coordinate frame. In particular, a return carries dynamic information in amplitude (ω) and frequency (ω) at some point in azimuth (r,θ) and elevation (r,θ) planes. A passive seeker requires an illuminator beam, I(ω,φ,θ), and may require a frequency modulation on the illuminator. To model a simplex target return, we have based the dynamics on a point source radar cross section (RCS) along a line of sight (LoS) radial. The Az and El angles are equivalent to antenna placement, the attenuation and frequency dynamics are modeled in commercial off-the-shelf (COTS) software.

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / PSK demodulators have been an integral part of the signal recovery process for decades. Unless a person has designed a demodulator, how much can a person know or understand about its operation? Instruction on how to set up a demodulator’s parameters to acquire a signal is found in a manual. An explanation of why parameters are set a certain way to handle particular input signal characteristics is often not provided in a manual. This paper is designed to be a tool to aid engineers, technicians, and operators who utilize demodulators. Its purpose is to relay the functionality of a demodulator to a user so that he or she can take advantage of its control parameters and status feedback. Knowing the reasons why a demodulator is set to certain parameters may greatly reduce confusion when a system is not working properly. On site troubleshooting may be accomplished without the need to call the manufacturer of the product. Another advantage of understanding the operation will be recognized when interfacing with the manufacturer. A person will be able to relay the information to a design engineer more easily, and will understand more of the engineer’s feedback on the potential problem. Utilizing this paper as an aid to enhance operation of a PSK demodulator will bring a user one step closer to understanding the complexity of its design.

Tuning to an optimal stimulus is a widespread property of neurons in cortex. We propose that such tuning is a consequence of normalization or gain control circuits. We also present a biologically plausible neural circuitry of tuning.

Abstract This thesis describes the development of integrated structures and circuit implementations for the receiver channel of portable pulsed time-of-flight laser rangefinders for industrial measurement applications where the measurement range is from ∼1 m to ∼100 m to noncooperative targets and the required measurement accuracy is from a few millimetres to a few centimetres. The receiver channel is used to convert the current pulse from a photodetector to a voltage pulse, amplify it, discriminate the timing point and produce an accurately timed logic-level pulse for a time-to-digital converter. Since the length of the laser pulse, typically 5 ns, is large compared to the required accuracy, a specific point in the pulses has to be discriminated. The amplitude of the input pulses varies widely as a function of measurement range and the reflectivity of the target, typically from 1 to 100 ... 1000, so that the gain of the amplifier channel needs to be controlled and the discrimination scheme should be insensitive to the amplitude variation of the input signal. Furthermore, the amplifier channel should have low noise in order to minimize timing jitter. Alternative circuit structures are discussed, the treatment concentrating on the preamplifier, gain control circuitry and timing discriminator, which are the key circuit blocks from the performance point of view. New circuit techniques and structures, such as a fully differential transimpedance preamplifier and a current mode gain control scheme, have been developed. Several circuit implementations for different applications are presented together with experimental results, one of them being a differential BiCMOS receiver channel with a bandwidth of 170 MHz, input referred noise of 6 pA/√Hz and maximum transimpedance of 260 kW. It has an accuracy of about +/- 7 mm (average of 10000 measurements), taking into account walk error with an input signal range of 1:624 and jitter (3s). The achievable performance level using integrated circuit technology is comparable or superior to that of the previously developed commercially available discrete component implementations, and the significantly reduced size and power consumption open up new application areas.

Sensory neurons assemble to form networks that process inputs coming from the senses. Through synaptic connections neurons interact and create complex dynamical states in response to these inputs. Networks with different connectivity patterns are thought to display different states and therefore subserve different computational goals. In this thesis, we mainly study brain rhythms, a dynamical state that occurs in various neural structures. Rhythms are emergent oscillations that typically occur in homogeneous recurrent networks, whose neurons have identical properties and are densely interconnected. Many sensory systems comprise neurons with opposite ON and OFF responses to inputs. We show that homogenous recurrent networks fail to sustain rhythms when ON and OFF neurons are present in equal proportions. This happens even when the network is subjected to spatially correlated inputs, which are known to promote synchronized oscillations. In this context, we adapted the so-called linear response theory to include networks containing ON and OFF neurons with different intrinsic properties. In this asymmetric case, oscillations can be recovered. A simpler approach is to segregate the ON and OFF populations, thus producing two oscillating subnetworks. The dynamics of purely feedforward networks are studied next. These networks are composed of two or more populations. The populations are connected in a serial fashion, but neurons are unconnected within the populations. This connectivity scheme is drastically different from the fully recurrent network. Yet, this network is shown to display oscillatorylike properties when subjected to spatially correlated stimulation under certain conditions. We also find that this network can implement various types of gain control, depending on the noise in the system and the strength of synaptic interactions. These results establish some unexpected links between feedforward and recurrent networks. Along the way, we apply our results and conclusions to a well-characterized sensory network, the electrosensory system of weakly electric fish.

The output characteristics of five compression hearing aids in response to a transient signal were examined to determine if, the input-output function (i.e. output levels of the hearing aid as a function of input level) for a transient signal could be made to approximate that of a continuous signal, by activating the compression circuit with a second signal (activator). Input-output functions for three input compression and two output compression hearing aids were obtained in order to determine if: 1. the automatic gain control (AGC) was activated by the second signal and the transient signal output approximates that of a continuous tone, and 2. if the second tone was evident in the output of the hearing aid and thereby potentially being an interfering factor in aided auditory brainstem response (ABR) measurement.