Abstract:
An FM modulator circuit is provided having separate modulation (100) and channel signal paths (102). The modulation path includes a numerically controlled modulated oscillator (104) which receives a modulation signal and provides a modulated intermediate frequency signal which has been frequency modulated in accordance with the modulation signal. A channel select number is provided representative of a channel of a desired frequency. A channel signal path is provided including local oscillator means for receiving the channel select signal and providing a channel signal of the desired frequency. The modulated intermediate frequency is then combined with the channel signal to provide the desired FM output signal.
Abstract:
Es ist eine Schaltungsanordnung zur Erzeugung eines Referenzstromes (Iref) sowie eine Oszillatorschaltung mit der Schaltungsanordnung angegeben, welche eine Kapazität (8) umfasst, die an den Eingang einer spannungsgesteuerten Stromquelle (1) angeschlossen ist. Zum Ansteuern der Kapazität (8) sind zwei Verstärker (4, 6) mit verschiedenen Treiberfähigkeiten (gm1, gm2) vorgesehen, zwischen denen umschaltbar ist. Gemäss dem vorliegenden Prinzip kann beispielsweise ein LC-Oszillator (14) stromkontrolliert und gleichzeitig besonders rauscharm mit dem Referenzstrom (I ref ) gespeist werden.
Abstract:
A fully integrated, adjustable oscillator circuit for use with a crystal is disclosed in which a crystal oscillator, such as a Pierce oscillator, is arranged to utilize a tuning network that includes at least one integrated varactor (voltage-variable-capacitor) as a shunt element for providing at least one type of adjustment of the oscillating signal. More than one type of adjustment can be provided by including a bank of varactors for each of the shunt elements of the tuning network, in which various individual varactors are selected in binary (on-off) fashion to effect digital as well as analog adjustment of the crystal oscillator.
Abstract:
In one embodiment, an apparatus includes a first circuit of a digitally controlled oscillator (DCO). The first circuit has a loss component. A second circuit is coupled to the first circuit and configured to transform a positive impedance into a negative impedance in series with a negative resistance. The negative impedance includes an adjustable reactive component used to adjust a frequency of an output signal of the DCO. An equivalent reactance seen by the first circuit is less than a reactance of the adjustable reactive component.
Abstract:
An RC oscillator for varying an oscillation frequency which has a counter for counting a clock pulse of the oscillation frequency and for outputting a counted value in a form of a plurality of bits to an output terminal. It also includes a standard capacitor, a plurality of capacitors having a capacitance value in proportion to a weight of bits outputted from the counter, and a plurality of switches connected to one end of each capacitor for selectively connecting the capacitors in parallel. A plurality of first gate circuits control the switches connected thereto in response to an output of the counter, each first gate circuit has an input terminal connected to an output terminal of the counter and an output terminal connected to a control terminal of the switches. A second gate circuit turns on the switches independently of the output of the counter in the case of a frequency adjustment of the oscillation signal, the second gate circuit has an input terminal connected to a predetermined output terminal of the counter and an output terminal connected to a switch for use of the standard capacitor.
Abstract:
A modulating signal is applied to an analog-to-digital converter which addresses a read-only memory phase look-up table. The read-only memory phase look-up table output is applied to a polarity generator. The polarity generator output and output from a phase accumulator are input to a phase adder. The phase adder output is applied to the input of a sine look-up read-only memory whose output is applied to a digital-to-analog converter and low-pass filtered to produce an amplitude-modulated carrier signal. The invention thereby digitally amplitude modulates a carrier signal in the phase domain without any multiplication being required.