Telefonaktiebolaget Lm Ericsson (publ)

Peter M Petersson

Mats Johansson

Bo Gosta Hedberg

Patrik Eriksson

Krister I Ripstrand

The present invention eliminates the need for an anti-aliasing filter in a receiver that employs an analog-to-digital converter. By maintaining a predetermined relationship between a local oscillator frequency and the sampling frequency of the analog-to-digital converter, aliasing that would normally occur in the desired pass band is avoided. More specifically, the frequency of the periodic signal provided to the mixer is an integer multiple of half the sampling rate of the analog-to-digital converter. In a preferred, non-limiting example embodiment, the sampling rate of the analog-to-digital converter Fand the frequency of the local oscillator Fare related by the following: F=n*F/2, where n is any positive integer.

Method and apparatus for analog-to-digital conversion

A digital-to-analog circuit arrangement that can be used, for example, in radio transmitters, includes a Digital-to-Analog Converter (DAC) whose output is connected directly to a mixer. A periodic signal is also provided to the mixer. The frequency of the periodic signal provided to the mixer, is an integer multiple of half the update rate frequency of the DAC. In an embodiment of the invention, the frequency of the periodic signal provided to the mixer, is half the update rate frequency of the DAC. An intermediate frequency (IF) filter can be provided. downstream of the mixer.

Digital to analog conversion method and apparatus

A phase locked loop frequency synthesizer in which the output frequency is changed in a series of steps in order to reach a final frequency value. The steps are computed and stored in a memory in a control unit. The steps are chosen to approximately cancel the poles of the transfer function of the synthesizer. The phase locked loop provides increased switching speed.

Step controlled signal generator

Separate phase (or frequency/phase) detectors are used in separate feedback loops of a phase-locked loop, one of the detectors having a dead zone and the other detector having no dead zone. The dead zone of the one detector, rather than being regarded as undesirable as in the prior art, is used to gradually shift the effective loop bandwidth of the phase-locked loop from a wide bandwidth to a narrow bandwidth without requiring any deliberate control action or switching circuitry.

Multi-loop controlled VCO

In a frequency synthesizer of the type having a phase locked loop, a variable frequency divider is coupled to the output of the phase locked loop and a variable divider for dividing a reference signal is coupled to a frequency source for the frequency synthesizer. The phase lock loop also includes a variable divider for dividing the signal fed back from a voltage controlled oscillator to a phase detector. The division numbers or divisors of the variable frequency dividers are controlled such that a predetermined relationship exists among the frequency dividers. The frequency synthesizer is capable of switching reference frequencies without causing phase jumps. The reference frequency is selected depending upon the choice of a division number for the frequency divider coupled to the output of the frequency synthesizer.

Broad band frequency synthesizer for quick frequency retuning

A frequency synthesizing apparatus comprising a reference generator (1) and a phase locked loop containing a phase detector (3) of the sample-hold type, a loop filter (4) a VCO (5) and a frequency divider (6) in the loop. The frequency divider (6) can be set at different numbers (N) so that the VCO sends different frequencies. In accordance with the invention a synchronizing unit (2) is connected between the reference generator (1) and the phase detector (3). The synchronizing unit switches reference generator (1) and the frequency divider means simultaneously to the phase locked loop during the locking phase and switches these out during a working phase, when the VCO (5) sends an output signal of the desired frequency (f). The loop filter can then be dimensioned with a wide bandwidth for rapid locking.

Growing community of inventors

Jarfalla, Sweden

Peter M Petersson