Systems and methods for resizing a signal for use with a fixed-point DSP are provided. More specifically, a process called companding is used in conjunction with fixed-point devices to resize a signal to make use of the available range of these devices. In some embodiments, companding is used to improve the signal-to-noise and distortion ratio. Also, information loss associated with quantization and rounding errors can be reduced in some embodiments.

Systems and methods for companding adc-dsp-dac combinations

The transmitter circuit architecture is disclosed based on a phase lock loop architecture and which uses a delta-sigma modulator with 2 point modulation. In order to restrict the bandwidth of the PLL, subsidiary analogue modulation is employed, which requires aligning with the delta-sigma modulation. Alignment of the modulation is accomplished by correction of the sensitivity of the PLL voltage controlled oscillator to modulation by correlating residual modulation in the PLL with the modulated signal input. The action of the modulation correlator trims the modulation and the PLL bandwidth without disturbing the normal operation of the transmitter, and allows the use of modulation bandwidths greater than the PLL bandwidth.

Radio transmitter architecture comprising a PLL and a delta-sigma modulator

A digital frequency synthesizer comprises means for the generation of the samples of a digital signal to be converted into an analog signal encoded on N bits as a function of a frequency control word, means for the generation of a noise signal encoded on N bits, and a digital-analog converter, the useful signal and the noise signal being truncated to M bits before being added up by an adder. The result of the addition is converted into analog signal form by the digital-analog converter. The generated noise has at least a noise density substantially equal to a law of equiprobability, this density being zero outside a given space. Application especially to direct digital synthesis, for example in the field of radar techniques or that of instrumentation.

Digital synthesizer of signals

A method and apparatus are disclosed for tuning a voltage controlled oscillator (VCO) having two point modulation used in a phase lock loop modulation system. A loop correction voltage applied to a first modulation input of the VCO when a first modulation signal, e.g., +1, is applied to a second modulation input of the VCO is compared to a loop correction voltage applied to the first modulation input when a second modulation signal, e.g., −1, is applied to the second modulation input of the VCO. The comparison produces a correction signal used to adjust the signal level of at least one of the signals, e.g., the second modulation input signal, applied to the two modulation inputs of the VCO.

Method and apparatus for simplified tuning of a two-point modulated PLL

Direct frequency modulation of a phase-locked loop (PLL) output signal is achieved by means of a modulation signal comprising a digital sequence. The digital modulation signal is coupled to the input of the VCO of the PLL, and is also coupled to drive an up-down counter. The output of the counter is coupled to a D/A converter to provide a compensation signal for the PLL. When the counter output reaches values representing modulation-induced phase errors of +360 degrees and −360 degrees, the counter generates signals respectively corresponding thereto to adjust the PLL frequency divider.

Direct modulated phase-locked loop

Device for continuous phase modulation, produced from a frequency synthesizer including a variable oscillator and a phase-locked loop with, in series, a frequency division circuit, a phase comparator and a low-pass filter. In order to reduce modulation in the loop, the modulation is applied not only to the input of the synthesizer but also, in compensation, in the loop. In order to eliminate the modulation residue in the loop, a control signal for the oscillator is derived by a circuit which performs a correlation between the residue of the modulation and the output signal from a filter producing the same filtering effect as the loop, and which receives the modulation signal from the input of the synthesizer.

Device for continuous phase modulation by frequency synthesizer with phase-locked loop

Dispositif de modulation de phase continue, realise a partir d'un synthetiseur de frequences comportant un oscillateur variable (1) et une boucle a verrouillage de phase (5-6) avec, en serie, un circuit de division de frequence, un comparateur de phases et un filtre passe-bas (5). Il est connu, pour reduire la modulation dans la boucle, d'appliquer la modulation non seulement a l'entree du synthetiseur mais egalement, en compensation, dans la boucle. Pour eliminer le residu de modulation dans la boucle un signal de commande de l'oscillateur (1) est elabore par un circuit (12, 13) qui effectue une correlation entre le residu de la modulation et le signal de sortie d'un filtre (17) produisant le meme effet de filtrage que la boucle et qui recoit le signal de modulation de l'entree du synthetiseur. Application a la modulation de phase continue.

Dispositif de modulation de phase continue par synthetiseur de frequences a boucle a verrouillage de phase

A continuous phase modulation device consisting of a frequency synthesizer having a variable oscillator (1) and a phase-locked loop (5-6) with, in series, a frequency divider circuit, a phase comparator and a low-pass filter (5). Modulation in the loop has been known to be reduced by applying modulation both at the synthesizer input and, for compensation, in the loop. To eliminate residual modulation in the loop, an oscillator control signal is generated by a circuit (12, 13) which correlates the residual modulation with the output signal from a filter (17) providing the same filtering effect as the loop and receiving the modulation signal from the synthesizer input. The device is useful for continuous phase modulation.

Lionel Fousset

Papers

Device for continuous phase modulation by frequency synthesizer with phase-locked loop

Dispositif de modulation de phase continue par synthetiseur de frequences a boucle a verrouillage de phase

Continuous phase modulation device using a frequency synthesizer with a phase-locked loop