Abstract

A Class D amplifier comprising a control circuit configured to receive an audio input signal and derive first, second and third PWM switching control signals therefrom, being supplied to respectively first, second and third switches of a driver, the first and second switches being serially arranged between first and second supply voltages, and having a common node coupled to an output terminal. The driver comprises a DC level shifter being configured to provide a reference voltage to a reference terminal in at least first and second states of operation, said reference voltage including a DC component at least substantially equidistant between the first and second supply voltages. Said third switch being included in a shunt path between the output and the reference terminal.

IPC Classes  ?

• H03F 3/217 - Class D power amplifiers; Switching amplifiers
• H03F 1/30 - Modifications of amplifiers to reduce influence of variations of temperature or supply voltage
• H03F 1/02 - Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation

Abstract

A class D amplifier output stage including an input for receiving an input signal, an output for providing an output signal to a load, serially coupled upper and lower switching devices configured to provide an output signal to the output, a driver circuit configured to receive the input signal, and to derive therefrom first and second drive signals for driving the upper and lower switching devices alternately from a conducting state into a non-conducting state and vice versa, such that the conducting state periods of the upper switching device with respect to those of the lower switching device are mutually exclusive and separated by dead time intervals during which both upper and lower output transistors are non-conducting. To reduce distortion and more particularly, total harmonic distortion (THD), the amplifier output stage includes a substantially linear circuit configured to provide a bidirectional current sink for residual currents from the load occurring during at least part of each dead time interval.

IPC Classes  ?

• H03F 3/217 - Class D power amplifiers; Switching amplifiers
• H03F 1/32 - Modifications of amplifiers to reduce non-linear distortion
• H03F 3/185 - Low-frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only with field-effect devices
• H03F 3/30 - Single-ended push-pull amplifiers; Phase-splitters therefor

Abstract

An anti-jamming system includes a tunable negative jamming signal feedback loop for feedback suppression of a received jamming signal. The system includes a zero IF phase locked loop (PLL) jamming signal receiver having a synchronous demodulator and a phase detector. A VCO is included in the PLL, as well as a phase detector and a loop filter. A replica jamming signal generator includes a tracking modulator with a baseband signal input coupled to an output of a synchronous demodulator in the receiver and a carrier input provided by the VCO. An output of the tracking modulator is negatively fed back to the input of the receiver to suppress the jamming signal in the received input.

IPC Classes  ?

• H04B 1/10 - Means associated with receiver for limiting or suppressing noise or interference
• H04K 3/00 - Jamming of communication; Counter-measures

Abstract

Method for reducing noise included in a stereo reproduction signal derived from a stereo input signal characterized by the steps of: • varying stereo channel separation of said stereo reproduction signal with frequency within the frequency range of the stereo input signal in accordance with the frequency response of a filter selectivity located around a center frequency to obtain a stereo channel separation peak value at said center frequency; • at a continuing increase of said noise, decreasing the bandwidth of said filter selectivity to a predetermined non-zero bandwidth while maintaining the channel separation within the bandwidth of said filter selectivity substantially at said channel separation peak value.

IPC Classes  ?

• H04B 1/16 - Circuits
• H04H 40/81 - Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast receiving for stereo-monaural switching

Abstract

i are each consecutively selected to be coupled to a load.

IPC Classes  ?

• H03M 1/66 - Digital/analogue converters

Abstract

Anti jamming system comprising a tunable negative jamming signal feedback loop for feedback suppression of a received jamming signal, including a receiver receiving an jamming signal followed by a jamming signal replica generator for generating an replica jamming signal. The receiver comprising a zero IF PLL jamming signal receiver having a synchronous demodulator and a phase detector, signal inputs thereof being coupled to said input means and carrier inputs coupled to in-phase and phase quadrature oscillator outputs, respectively, of a local voltage controlled oscillator (VCO), said VCO receiving a tuning control signal for tuning the zero IF PLL jamming signal receiver at the carrier frequency of the jamming signal. The VCO is included in a phase locked loop (PLL) comprising subsequent to the VCO, said phase detector and a loop filter. The replica jamming signal generator includes a tracking modulator with a baseband signal input coupled to an output of said synchronous demodulator and a carrier input coupled to the in-phase oscillator output of the VCO, an output of said modulator being negatively fedback to the input of the receiver.

IPC Classes  ?

• G01S 7/36 - Means for anti-jamming

Abstract

Anti jamming system comprising a tunable negative jamming signal feedback loop for feedback suppression of a received jamming signal, including an receiver receiving an jamming signal followed by a replica jamming signal generator for generating an replica jamming signal. The receiver comprising a zero IF PLL receiver having a synchronous demodulator and a phase detector, signal inputs thereof being coupled to said input means and carrier inputs coupled to in-phase and phase quadrature oscillator outputs, respectively, of a local voltage controlled oscillator (VCO), said VCO receiving a tuning control signal for tuning the zero IF PLL receiver at the carrier frequency of the jamming signal. The VCO is included in a phase locked loop (PLL) comprising subsequent to the VCO, said phase detector and a loop filter. The replica jamming signal generator includes a modulator with a baseband signal input coupled to an output of said synchronous demodulator and a carrier input coupled to the in-phase oscillator output of the VCO, an output of said modulator being negatively fedback to the input of the receiver.

IPC Classes  ?

• G01S 7/36 - Means for anti-jamming

Abstract

FM receiver including an RF input circuit followed by a tunable mixer stage for frequency conversion of an RF FM signal into an IF FM signal, which is coupled to an FM input of a first narrow-band IF filter. The center frequency of the first narrow-band IF filter is controlled to vary in dependence on the IF FM signal. The first narrow-band IF filter is subsequently coupled to a first FM demodulator and a first LF signal processing unit. To increase the receiver's selectivity and sensitivity without adversely affecting tracking stability, the FM input of a first narrow-band IF filter is coupled through a second FM demodulator to a control input of said first narrow-band FM tracking filter for a feed forward tracking control of the center frequency of said first narrow-band FM tracking filter with the momentary frequency of the IF FM signal.

IPC Classes  ?

• H04B 1/16 - Circuits

Abstract

Anti jamming system comprising a tunable negative jamming signal feedback loop for feedback suppression of a received jamming signal, including an receiver receiving an jamming signal followed by a replica jamming signal generator for generating an replica jamming signal. The receiver comprising a zero IF PLL receiver having a synchronous demodulator and a phase detector, signal inputs thereof being coupled to said input means and carrier inputs coupled to in-phase and phase quadrature oscillator outputs, respectively, of a local voltage controlled oscillator (VCO), said VCO receiving a tuning control signal for tuning the zero IF PLL receiver at the carrier frequency of the jamming signal. The VCO is included in a phase locked loop (PLL) comprising subsequent to the VCO, said phase detector and a loop filter. The replica jamming signal generator includes a modulator with a baseband signal input coupled to an output of said synchronous demodulator and a carrier input coupled to the in-phase oscillator output of the VCO, an output of said modulator being negatively fedback to the input of the receiver.

IPC Classes  ?

• H03D 7/16 - Multiple frequency-changing
• G01S 7/36 - Means for anti-jamming
• G01S 7/38 - Jamming means, e.g. producing false echoes

Abstract

Anti jamming system comprising a tunable negative jamming signal feedback loop for feedback suppression of a received jamming signal, including a receiver receiving an jamming signal followed by a jamming signal replica generator for generating an replica jamming signal. The receiver comprising a zero IF PLL jamming signal receiver having a synchronous demodulator and a phase detector, signal inputs thereof being coupled to said input means and carrier inputs coupled to in-phase and phase quadrature oscillator outputs, respectively, of a local voltage controlled oscillator (VCO), said VCO receiving a tuning control signal for tuning the zero IF PLL jamming signal receiver at the carrier frequency of the jamming signal. The VCO is included in a phase locked loop (PLL) comprising subsequent to the VCO, said phase detector and a loop filter. The replica jamming signal generator includes a tracking modulator with a baseband signal input coupled to an output of said synchronous demodulator and a carrier input coupled to the in-phase oscillator output of the VCO, an output of said modulator being negatively fedback to the input of the receiver.

IPC Classes  ?

• H04B 15/00 - Suppression or limitation of noise or interference

Abstract

FM receiver including an RF input circuit followed by a tunable mixer stage for frequency conversion of an RF FM signal into an IF FM signal, which is coupled to an FM input of a first narrow-band IF filter. The center frequency of the first narrow-band IF filter is controlled to vary in dependence on the IF FM signal. The first narrow-band IF filter is subsequently coupled to a first FM demodulator and a first LF signal processing unit. To increase the receiver's selectivity and sensitivity without adversely affecting tracking stability, the FM input of a first narrow-band IF filter is coupled through a second FM demodulator to a control input of said first narrow-band FM tracking filter for a feed forward tracking control of the center frequency of said first narrow-band FM tracking filter with the momentary frequency of the IF FM signal.

IPC Classes  ?

• H04B 1/16 - Circuits
• H03D 3/00 - Demodulation of angle-modulated oscillations

Abstract

Transceiver comprising a low power RF radio broadcast transmitter having means to modulate a transmitter carrier frequency with a baseband modulation signal as well as transmitter tuning means to vary said transmitter carrier frequency within an RF radio broadcast band. To secure that operation of said transmitter means will not cause interference to broadcast reception, said transceiver includes an RF radio broadcast receiver having a search tuning circuit being provided with channel selecting means for, in a receiving mode of the transceiver, detecting a free RF radio broadcast channel within said RF radio broadcast band carrying no RF signal exceeding a predetermined threshold level, said channel selecting means supplying tuning data defining said free RF radio broadcast channel to means for transmitting said tuning data to said transmitter tuning means for tuning said transmitter carrier frequency to said free RF radio broadcast channel in a transmitting mode of the transceiver.

IPC Classes  ?

• H04B 1/38 - Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving

Abstract

Transceiver comprising a low power RF radio broadcast transmitter having means to modulate a transmitter carrier frequency with a baseband modulation signal as well as transmitter tuning means to vary said transmitter carrier frequency within an RF radio broadcast band. To secure that operation of said transmitter means will not cause interference to broadcast reception, said transceiver includes an RF radio broadcast receiver having a search tuning circuit being provided with channel selecting means for, in a receiving mode of the transceiver, detecting a free RF radio broadcast channel within said RF radio broadcast band carrying no RF signal exceeding a predetermined threshold level, said channel selecting means supplying tuning data defining said free RF radio broadcast channel to means for transmitting said tuning data to said transmitter tuning means for tuning said transmitter carrier frequency to said free RF radio broadcast channel in a transmitting mode of the transceiver.

IPC Classes  ?

• H04B 1/38 - Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving