摘要:
A random number generator comprising a sigma-delta modulator, the sigma-delta modulator having a modulation unit and a feedback loop arranged to receive a digital output signal from the modulator and form an adjustment signal in dependence on the digital output signal such that at any given time the absolute difference between an amplitude of a summation output signal of the modulator and a quantizer threshold of the modulator is less than the first voltage range. The random number generator is thus capable of forming a digital output signal that has a high degree of entropy.
摘要:
The A/D converter has a digital output for outputting a digital output signal selected from a set of three or more available values. A feedback loop generates the digital output signal so that a time averaged difference between an analog input signal and an analog feedback signal representative of the digital output signal is minimized. A feedback signal generator generates successive signal levels of the feedback signal. A return to zero switch inserts predetermined return to zero levels between the signal levels in the feedback signal. The return to zero switch is also used to provide the signal level for one of the available values.
摘要:
A 1-bit D/A conversion circuit according to the present invention comprises an RZ signal generating circuit and a PRZ signal generating circuit. The RZ signal generating circuit receives 1-bit digital data sampled at a predetermined frequency, converts the digital data into a first RZ signal and a second RZ signal complementary to the first RZ signal, shifts the first and second RZ signals with respect to each other by an integral multiple of the predetermined frequency, which is greater than one, and outputs these RZ signals. The PRZ signal generating circuit receives the first and second RZ signals, combines these signals together, and outputs a signal which is a type of a PRZ signal.
摘要:
An improved analog front end circuit for a high performance modem comprising an oversampling sigma delta modulator analog-to-digital converter which employs a novel four phase clocked MOSFET switched capacitor integrator. The integrator is switched in a manner as to eliminate signal dependent charges in the MOSFET switches. The sigma delta modulator shifts quantization noise of the analog-to-digital conversion process out of baseband of the analog signal. A novel integrated decimating FIR low pass filter filters the quantization noise from the digital output signals, and reduces the number of digital signals to obtain a sufficient number of signal samples in order to provide operation at high speeds, for example 9600 bps. The improved four phase switched capacitor integrator is also suitable for use in sigma delta modulator circuits, analog-to-digital converter circuits, integrating cirucits, and the like. A novel return-to-zero circuit eliminates distortion in a sigma delta modulator based analog-to-digital conversion process which can result from unequal rise and fall times of the digital output, by insuring that the energies in signals represented by a "one" and signals represented by a "zero" are equal, even during portions of the bit stream wherein there is a consecutive sequence of "ones".
摘要:
Analog circuits are often non-linear, and the non-linearities can hurt performance. Designers would trade off power consumption to achieve better linearity. An efficient and effective calibration technique can address the non-linearities and reduce the overall power consumption. A dither signal injected to the analog circuit can be used to expose the non-linear behavior in the digital domain. To detect the non-linearities, a counting approach is applied to isolate non-linearities independent of the input distribution. The approach is superior to and different from other approaches in many ways.
摘要:
A bandpass sigma-delta modulator using acoustic resonators or micro-mechanical resonators. In order to improve resolution at high frequencies, acoustic resonators or micro-mechanical resonators are utilized in a sigma-delta modulator instead of electronic resonators. The quantized output is fed back using a pair of D/A converters to an input summation device. In fourth order devices, the feed back is to two summation devices in series. Such a sigma-delta modulator is usable in a software defined radio cellular telephone system and in other applications where high-frequency and high-resolution A/D conversion is required.
摘要:
A digital-to-analog converter having a differential signal path, and a current parking circuit that is independent of the signal path, thereby avoiding a source of imbalance that caused output anomalies in conventional digital-to-analog circuitry. In one embodiment of the invention, a pair of diodes in the current parking circuit are connected through their own independent load resistors to a voltage source. In another embodiment, a single diode is used instead of the pair of diodes, and in a third embodiment the current parking circuit comprises a single load resistor connected to the voltage source, and no diodes at all.
摘要:
A bandpass sigma-delta modulator using acoustic resonators or micro-mechanical resonators. In order to improve resolution at high frequencies, acoustic resonators or micro-mechanical resonators are utilized in a sigma-delta modulator instead of electronic resonators. The quantized output is fed back using a pair of D/A converters to an input summation device. In fourth order devices, the feed back is to two summation devices in series. Such a sigma-delta modulator is usable in a software defined radio cellular telephone system and in other applications where high-frequency and high-resolution A/D conversion is required.
摘要:
A bandpass sigma-delta modulator using acoustic resonators or micro-mechanical resonators. In order to improve resolution at high frequencies, acoustic resonators or micro-mechanical resonators are utilized in a sigma-delta modulator instead of electronic resonators. The quantized output is fed back using a pair of D/A converters to an input summation device. In fourth order devices, the feed back is to two summation devices in series. Such a sigma-delta modulator is usable in a software defined radio cellular telephone system and in other applications where high-frequency and high-resolution A/D conversion is required.
摘要:
The output gates of a delta-sigma modulator can generate i(t) transient signal in the power supply lines of a delta-sigma modulator. These i(t) spikes, which would otherwise produce non-linearities which can be coupled into the frequency band of interest of the modulator, are made to be linear by using return-to-zero data encoding and by providing multi-bit outputs to the delta-sigma modulator in which the output states all have equal numbers of logic ones at the output lines for each of the output states.