Abstract: A fractional-N frequency synthesizer using the first order Delta-Sigma frequency discriminator which is composed of only a dual modulus frequency divider and a D flip-flop is used to replace the function of phase detector is disclosed. The invented structure is characterized by generating the feedback error signal indirectly from the output bit stream of said discriminator in such a way that the quantization noise contained in the bit stream is maximally canceled by comparing it with another bit stream generated by an accumulator digitally performing the first order Delta-Sigma modulation to the required fractional number, so that there is almost no discrete fractional spurs in the output spectrum of the synthesizer. Most other circuit of the synthesizer could be formed digitally so that high integration level and low noise performance could be achieved. Narrow or wideband phase or frequency modulation could also be conveniently added digitally with good accuracy.

Abstract: A polar loop transmission circuit is proposed wherein a signal to be transmitted and a feedback signal are separated into their polar phase and amplitude components and the components are compared to one another for realizing a phase and amplitude modulation. An amplitude modulator controlled by an amplitude modulation signal is provided, whereby the amplitude modulator follows an oscillator and is preferably fashioned as a nonlinear amplifier that is operated in saturation. An amplifier attenuating the output signal of the amplitude modulator is provided in the feedback path. The present transmission architecture is suitable for future mobile radio telephone systems having a phase and amplitude modulation and are based on the known GSM standard, for example.

Abstract: A fractional-N frequency synthesizer using the first order Delta-Sigma frequency discriminator which is composed of only a dual modulus frequency divider and a D flip-flop is used to replace the function of phase detector is disclosed. The invented structure is characterized by generating the feedback error signal indirectly from the output bit stream of said discriminator in such a way that the quantization noise contained in the bit stream is maximally canceled by comparing it with another bit stream generated by an accumulator digitally performing the first order Delta-Sigma modulation to the required fractional number, so that there is almost no discrete fractional spurs in the output spectrum of the synthesizer. Most other circuit of the synthesizer could be formed digitally so that high integration level and low noise performance could be achieved. Narrow or wideband phase or frequency modulation could also be conveniently added digitally with good accuracy.

Abstract: A controllable current source circuit and a phase locked loop contained such a circuit are disclosed. The current source circuit such a single switched driver stage for a switched actuation of the loop filter. A continuously switched-on driver stage is introduced into one of several paths of the current source circuit, so that a continuously weaker current is drawn by the loop filter. The currents are preferably stabilized via a current mirror circuit.

Abstract: A polar loop transmission circuit is proposed wherein a signal to be transmitted and a feedback signal are separated into their polar phase and amplitude components and the components are compared to one another for realizing a phase and amplitude modulation. An amplitude modulator controlled by an amplitude modulation signal is provided, whereby the amplitude modulator follows an oscillator and is preferably fashioned as a nonlinear amplifier that is operated in saturation. An amplifier attenuating the output signal of the amplitude modulator is provided in the feedback path. The present transmission architecture is suitable for future mobile radio telephone systems having a phase and amplitude modulation and are based on the known GSM standard, for example.