Abstract: A the vertical-cavity surface-emitting laser includes a stripe-shaped active medium (10) having an emission maximum at a first wavelength (?1), wherein a first reflector (18) is arranged below the stripe-shaped active medium (10) and a second reflector (20) is arranged above the stripe-shaped active medium (10), with the first reflector (18) facing the second reflector (20), wherein the first reflector (18) and a second reflector (20) have a reflectivity maximum in the region of the first wavelength (?1), wherein a third reflector (12) and a fourth reflector (13) are each arranged on a side above or next to the stripe-shaped active medium (10), wherein the third reflector (12) faces the fourth reflector (13), and wherein the third reflector (12) and the fourth reflector (13) have a reflectivity maximum in the region of a second wavelength (?2), wherein the first wavelength (?1) is greater than the second wavelength (?2).

Abstract: A the vertical-cavity surface-emitting laser includes a stripe-shaped active medium (10) having an emission maximum at a first wavelength (?1), wherein a first reflector (18) is arranged below the stripe-shaped active medium (10) and a second reflector (20) is arranged above the stripe-shaped active medium (10), with the first reflector (18) facing the second reflector (20), wherein the first reflector (18) and a second reflector (20) have a reflectivity maximum in the region of the first wavelength (?1), wherein a third reflector (12) and a fourth reflector (13) are each arranged on a side above or next to the stripe-shaped active medium (10), wherein the third reflector (12) faces the fourth reflector (13), and wherein the third reflector (12) and the fourth reflector (13) have a reflectivity maximum in the region of a second wavelength (?2), wherein the first wavelength (?1)) is greater than the second wavelength (?2).

Abstract: A receiving device having an input receiving an input signal which includes a useful signal and an interference signal, a demodulator coupled to the input and generating a demodulated output signal from the input signal, which has an adjustable operating point, and a detector coupled to the demodulator and determining from the output signal a characteristic value representing a power level of the interference signal and setting the operating point of the demodulator as a function of the characteristic value.

Abstract: The invention relates to a method for producing c-plane GaN substrates or AlxGa1-xN substrates using an original substrate. Said method is characterized by the following steps: a tetragonal (100)-oriented or (?100)-oriented original LiAlO2 substrate is used; said original substrate is nitrided in a nitrogen compound-containing atmosphere at temperatures lying below the decomposition temperature of LiAlO2; a nucleation layer is grown at temperatures ranging between 500° C. and 700° C. by adding GaCl or AlCl or a mixture of GaCl and AlCl in a nitrogen compound-containing atmosphere; single-crystalline c-plane-oriented GaN or AlxGa1-xN is grown on the nucleation layer at temperatures ranging between 900° C. and 1050° C. by means of hydride vapor phase epitaxy (HVPE) with GaCl or AlCl or a GaCl/AlCl mixture in a nitrogen compound-containing atmosphere; and the substrate is cooled.

Abstract: A receiving device having an input receiving an input signal which includes a useful signal and an interference signal, a demodulator coupled to the input and generating a demodulated output signal from the input signal, which has an adjustable operating point, and a detector coupled to the demodulator and determining from the output signal a characteristic value representing a power level of the interference signal and setting the operating point of the demodulator as a function of the characteristic value.

Abstract: A multiplier circuit includes a multiplier core with two cross-coupled transistor pairs. First and second signal sources are respectively driven by first and second signals to be multiplied, and are connected to control inputs of the transistors of the multiplier core for diversion between the transistor pairs and between the transistors of the pairs.

Abstract: A semiconductor laser has an antiresonant waveguide (10), which is formed by a layer sequence applied to a substrate (1). The layer sequence has outer waveguide regions (2, 8), reflection layers (3, 7), and a waveguide core (11) with an active layer (5). With this structure, semiconductor lasers with only slight vertical beam divergence and with a large beam cross section can be produced.

Abstract: A multiplier circuit with a multiplier core with two cross-coupled transistor pairs (2, 3; 4, 5) is specified, wherein a first and a second signal source (10, 11, 13, 14), which are driven by a first and, respectively, second signal to be multiplied, are in each case connected to control inputs of the transistors (2 to 5) of the multiplier core for diversion between the transistor pairs (2, 3; 4, 5) or, respectively, differentially between the transistors (2, 4; 3, 5) of the differential amplifiers. Due to the high degree of symmetry which can be achieved at the input gates of the circuit, a particularly precise multiplication with good linearity is possible. The multiplier described can be used, for example, as radio-frequency mixer circuit or as 90° phase detector circuit.

Abstract: An offset voltage at an output of a differential amplifier is compensated for by a control circuit having a digital setting device. The control circuit has a control device which is controlled by an offset voltage of the differential amplifier and which feeds an offset compensation signal into the differential amplifier. Compared with analog compensation with an external storage capacitor, temporal drift effects do not distort the offset compensation on the differential amplifier. The described principle can be applied, for example, in radio frequency receiver circuits.

Abstract: An offset voltage at an output of a differential amplifier is compensated for by a control circuit having a digital setting device. The control circuit has a control device which is controlled by an offset voltage of the differential amplifier and which feeds an offset compensation signal into the differential amplifier. Compared with analog compensation with an external storage capacitor, temporal drift effects do not distort the offset compensation on the differential 10 amplifier. The described principle can be applied, for example, in radio frequency receiver circuits.

Abstract: A circuit array for frequency translation by means of quadrature heterodyne signals has very low quadrature errors even at very high frequencies and is monolithically integratable with little external circuitry. The circuit array includes a first mixer which receives a first portion of an input signal, a second mixer which receives a second portion of the input signal, and a heterodyne signal generator which receives a local oscillator signal and supplies quadrature heterodyne signals to the mixers. The heterodyne signal generator includes a control loop to ensure a 90.degree. phase shift between the quadrature heterodyne signals. The circuit array can be used in a modulator for a transmitter or in a demodulator for a receiver.

Abstract: A controllable broadband amplifier whose current consumption and direct voltage output level are independent of the control voltage includes four differential amplifiers, each having two input ports, two output ports, and a shared port. The two input ports of the first differential amplifier are connected to the two signal input ports of the broadband amplifier, the shared port of the first differential amplifier is connected to the power supply port via a constant current source, and the output ports of the first differential amplifier are connected to the shared ports of the second and third differential amplifiers. The input ports of the second and third differential amplifiers are connected together and to control voltage input ports of the broadband amplifier. One output port of the second differential amplifier is connected to one output port of the third differential amplifier, and both are connected to the shared port of the fourth differential amplifier.