J. Foit

Autonomous access control system

The main target of this paper is the software implementation of a radio frequency identification (RFID) access control system. It should be used for RFID readers, communication between readers and central device, with focus on a fast and safe data transfer, information database and real time data analysis. The readers have to work standalone, independently of the central device, with minimum power consumption. Optionally, the system should permit to connect additional sensors.

Analysis and Measurement of Capacitive Coupling in Integrated Circuits

Parasitic electromagnetic couplings result in the transfer of interfering energy from the interference source to the interference receiver. Inside the ICs the principal sources of interference are usually the clock circuits, output drivers and other circuits with low output impedance. The most frequent receivers of interference are the input circuits, flip-flops and circuits with high input impedance. The small distances of leads result in increased signal crosstalk inside the integrated circuit.

Coupling Capacitances of Connecting-lead Systems in Integrated Circuits

The development of integrated circuits has reached a situation today that the circuit operating speed is not limited by the parameters of the transistors any more, but rather by the electrical parameters of the interconnections inside the integrated circuit (Kropewnicki, 2002). For this reason, it is necessary to take in account the properties of interconnecting conductors from the start of the circuit design process. Undesirable parasitic electromagnetic couplings appear between the interconnecting lines, causing the transfer of interfering impulses onto the signal-carrying lines. These interfering impulses then result in random errors and/or disturbances in the integrated circuit

Reducing crosstalk in the internal structures of integrated circuits

The advent of novel sub-micron technologies of IC fabrication led to such a decrease in lead-to-lead separation that it is not possible any more to neglect the influence of these leads on the reliability of the system operation. Both the small lead separation and the application of multilayer interconnecting systems cause parasitic electromagnetic couplings; in the case of a unipolar CMOS technology, the capacitive coupling is the dominant effect. It is impossible to measure direct the rapid variations voltage between leads inside the IC.

Analysis of interfering signals in structures of integrated circuits

The electromagnetic compatibility serves as a measure for the possibility of coexistence of numerous electronic systems occupying a common environment without unwanted electromagnetic couplings that could interfere with correct functioning of individual systems [1]. The integrated circuits can be assumed to be independent electronic systems set up of individual operational blocks. The conveying of signals between blocks is provided by networks of electrical leads.

Special purpose oscillators

In many sensor applications, the frequency variations of signals generated as sustained oscillations are used as a measure of the tracked non-electrical quantity. The variations of oscillation frequency are usually obtained by some mechanism influencing the imaginary parts of impedances constituting a resonant circuit, electrical or some electro-mechanical equivalent. Unfortunately, in all these cases, real parts of the resonant circuit are varied as well, frequently to a quite considerable degree, meaning that in real operation the dynamic impedance of the resonator varies notably. As a result, it is rather difficult to keep the oscillations-generating circuit (i.e., oscillator) operating in optimum mode. In this connection, the optimum operating mode is defined as the state in which the condition for sustained self-oscillation is just fulfilled, without overdriving any of the active and passive devices involved. This paper discusses methods for solving this problem.

Influence of conductor systems on the crosstalks in integrated circuits

The advent of novel sub-micron technologies of IC fabrication led to such a decrease in lead-to-lead separation that it is not possible any more to neglect the influence of these leads on the reliability of the system operation. Both the small lead separation and the application of multilayer interconnecting systems cause parasitic electromagnetic couplings [1]; in the case of a unipolar CMOS technology, the capacitive coupling is the dominant effect. It is impossible to measure direct the rapid variations voltage between leads inside the IC.

Broadband amplitude-stabilized oscillator

In many applications we need oscillators tunable over a considerable frequency range by simple LC circuits with broadly varying dynamic resistances (quality factor Q of the reactances), while insisting on keeping a rather constant amplitude of the A.C. voltage across the LC circuit, or at least of some output voltage (not necessarily of a harmonic waveform) somewhere in the circuit. If we manage to arrange the circuit in such a way that a variable external load will not cause appreciable frequency shifts of the oscillations, it will be felt as a particular benefit. Another particular benefit will be strongly appreciated: if the circuit does not require any taps (inductive or capacitive) or any transformer coupling in the frequency-determining LC circuit. Perhaps even more appreciated will be a possibility to have one side of the LC circuit grounded. The following paper shows a surprisingly simple circuit capable to fulfill these seemingly conflicting requirements, all at the same time.

Frequency characteristic of the capacitive coupling in CMOS integrated circuits

Parasitic electromagnetic couplings result in the transfer of interfering energy from the interference source to (he interference receiver. Inside the Ies the principal sources of interference are usually the clock circuits, output drivers and other circuits with low output impedance. The most frequent receivers of inteiference are the input circuits, flip-flops and circuits with high input impedance. The small distances of leads result in increased signal crosstalk inside the integrated circuit.

Processing of low frequency analog signals from capacitive sensors

One of the crucial problems of direct processing low-frequency analog signals from capacitive sensors is the low frequency cutoff. The miniaturization of current sensors has led to rather small sensor capacitance, typically 10 values of the order of 10-11 F. If the signal from such a sensor, to be processed, has a frequency range extending below 100 Hz, problems start to appear due to the non-zero differential conductance seen at the signal amplifier input terminals. Moreover, some capacitive sensors require a DC polarizing voltage which, in certain cases, can be as high as 100 V or more.