Abstract: A DC offset cancellation circuit used for compensating a carrier leak at an output signal of a modulator has a sign extraction unit for extracting sign of an information signal which is applied to the modulator, an envelope detecting unit for performing envelope detection on the output signal of the modulator to output the resulting envelope, a slope detecting unit for performing polarity detection on the slope of the envelope; and a signal processing unit for generating a DC offset cancellation signal for compensating the carrier leak based on the result of the sign extraction and the result of the polarity detection. The signal processing unit preferably calculates the DC offset cancellation signal by multiplying the sign of the information signal by the polarity of the slope of the envelope and accumulating the result of multiplication.

Abstract: A mixer circuit accumulates I signal (digital signal of first channel) having its band limited by low-pass filter and first carrier signal to perform two-phase shift keying modulation thereon. An adder adds fundamental-wave component of bit clock signal BCK into Q signal (digital signal of second channel) having its band limited by the another low-pass filter to obtain a resultant added-up signal. Another mixer circuit accumulates the added-up signal and second carrier signal to perform two-phase shift keying modulation thereon. Output signals of the mixer circuits are input to another adder so that they may be added up to obtain a QPSK signal as a modulated quadrature signal. The QPSK signal contains frequency signals whose frequencies are a sum of bit clock frequency and carrier frequency and a difference between them. When demodulating, the carrier signal and the bit clock signal are reproduced using the frequency signals.

Abstract: A method and apparatus for wireless data transmission between a base station and one or more, in particular, passive and/or backscatter-based transponders, in which the base station modulates a carrier signal with a modulation signal, to generate synchronization markers, and transmits the modulated carrier signal. Whereby, a frequency of the modulated carrier signal can be switched between different frequency values.

Abstract: A stereo multiplex encoder (MPX) for FM transmission with a digital signal processor utilizes residual sideband modulation in stereo transmission instead of the conventional double sideband modulation. The adjustment of the sampling frequency to the modulation frequency (fmod=fs/2) is carried out, so that the antialiasing filter of the DAC can be used which produces the residual sideband modulated signal.

Abstract: The operating method is based on the simultaneous application of FM and AM, and is distinguished by passing through three operating states, specifically a warm-up phase, an impressing phase and the continuous operation. In the warm-up phase, the f002_hor is selected as fundamental frequency of the AM, or an AM is dispensed with. The impressing phase is distinguished by a temporally changing AM deviating from the conditions of the continuous operation and having an AM degree different from zero. In the continuous operation, constant conditions of the AM in the case of which the f002_hor is reached as fundamental frequency of the AM, and the AM degree is at 20 to 25% are characteristic.

Abstract: A modulation process with a fully suppressed carrier and input preprocessor filtering to produce an encoded output; for amplitude modulation (AM) and audio speech preprocessor filtering, intelligible subjective sound is produced when the encoded signal is demodulated using the RF Hearing Effect. Suitable forms of carrier suppressed modulation include single sideband (SSB) and carrier suppressed amplitude modulation (CSAM), with both sidebands present.

Abstract: A multi-carrier radio system in which pairs of subcarriers are positioned in frequency such that each subcarrier in a pair is the image of the other subcarrier in the pair. By making each subcarrier the image of another subcarrier, the radio system of the present invention permits highly integrated low-IF transceiver implementation. In an exemplary embodiment, a multi-carrier transceiver includes an integrated receiver comprising a first mixer for mixing an input signal with a local oscillator signal to produce an in-phase downconverted signal. Additionally, a first phase shifter phase-shifts the local oscillator signal to produce a quadrature local oscillator signal, and a second mixer mixes the input signal with the quadrature local oscillator signal to produce a quadrature downconverted signal. Thereafter, a second phase shifter phase-shifts, or rotates, the quadrature downconverted signal to produce a rotated quadrature downconverted signal.

Abstract: In a computer or other digital system a double side band suppressed carrier (DSB-SC) signal is derived from a clock or other synchronous signal. The clock or other synchronous signal is amplitude modulated at a source using a broadband low frequency envelope signal. The modulated signal is the DSB-SC signal, which then serves as a clock or other synchronous signal for the source and/or a destination circuit.

Abstract: In a computer or other digital system a clock or other synchronous signal is routed from a source to a destination as a double side band suppressed carrier (DSB-SC) signal. The clock or other synchronous signal is amplitude modulated at the source using a broadband low frequency envelope signal. The modulated signal is the DSB-SC signal, which then is routed over PC board traces to the destination. At the destination, the DSB-SC signal is demodulated to achieve the clock or other synchronous signal.

Abstract: A method and apparatus for reducing peak-to-average power ratio in a paging transmitter broadcasting an independent sideband amplitude modulation protocol is disclosed. A digital signal, for example a digital voice signal, is provided to a control gain generator which generates a digital gain sequence. The digital gain sequence is such that during peak values in the digital signal the gain is low and during low values in the digital signal the gain is high. The digital gain sequence is multiplied with the digital signal to compress the dynamic range of the digital signal.

Abstract: A method for digitally demodulating a complex modulation signal and allowing different parameters to be transmitted thereby. The input signal is baseband filtered and a complex demodulation is performed on the first subcarrier at a frequency Fp to obtain a correction signal, after squaring. The input signal is demodulated around a frequency exactly equal to twice the frequency of the first demodulation in order to obtain output signals which exhibit a frequency error with respect to 2Fp. This frequency error is corrected by multiplication with the previously derived frequency correction signal. The corrected signal is filtered at a frequency lower than 1 Hz, in order to obtain a signal giving the phase error at a frequency 0, that is to say that of the subcarrier at 2Fp. The signal makes it possible to correct the phase of signals which were previously frequency corrected in order to obtain two signals which are complementary to one another and transmitted by quadrature modulation around the frequency 2Fp.

Abstract: The invention provides various embodiments of a balanced modulator, each of which involves one or more individual amplitude modulators which, individually, do not provide suppressed-carrier outputs. A first embodiment employs a single amplitude modulator whose carrier input is selectively delayed by a half wavelength, depending on the polarity of the input modulating signal, and whose amplitude input receives the absolute value of the modulating input signal. A second embodiment involves summation of the outputs of two amplitude modulators whose carrier inputs are responsive to carrier signals offset by a half carrier wavelength and whose modulating signal inputs are responsive only to signals of respectively opposite polarity. Further, quadrature amplitude modulation (QAM) modulators are provided by a combination of the above-described modulators.

Abstract: A local frequency generator employing a single crystal oscillator, latches and direct digital synthesizer circuits digitally produces all signals needed in the transmitter channel of a MRI system to generate MRI transmitter RF pulses. The local frequency generator is operable in both the single side band and double side band modes and has the capability of switching between the modes. The generator is constructed with a phase resetting capability for providing the plural output frequencies needed for making plural MRI slices.

Abstract: A quadrature modulation circuit of the present invention has a phase shifter whose shifting amount is fixed at 90 degrees, a minute amount-phase shifter whose shifting amount is variable, a detector for detecting a RF signal supplied from the quadrature modulation circuit by a direct voltage signal, and a control circuit for generating a control signal in accordance with a direct voltage signal from the detector. Phase shifting amount of the minute amount-phase shifter is adjusted by the control signal whereby a total amount of the phase shifting is maintained at 90 degrees.

Abstract: Apparatus and method for effecting single sideband suppressed carrier modulation suitable for small, hand-held, high-frequency cellular radio transmitters such as those used at 900 mHz. A local oscillator generates a signal at 0.8 the frequency of the desired carrier. The generated frequency is counted down to produce an IF that is 0.2 the frequency of the desired carrier and the IF is mixed with the baseband signal to produce a modulated IF. The modulated IF is then mixed with the first generated signal to generate the modulated carrier signal. Advantageously, all of the foregoing components can be provided on the same integrated circuit chip.

Abstract: A carrier rejection circuit for improving carrier rejection in a balanced modulator includes balun transformers, connected to the carrier signal port and the modulated signal port, which reduces parasitic carrier leakage by reducing the average voltages at the ports, offset adjustment circuitry, connected to the modulating signal port, which applies an adjustable offset voltage to the modulating signal to reduce in-phase parasitic carrier leakage and carrier leakage caused by offset voltage at the modulating port, and a reactance network, connected between the carrier signal port and the modulated signal port, for reducing quadrature-phase parasitic carrier leakage.

Abstract: A system of transmission with amplitude modulation for the transmission of signals of all types, analog and/or digital, requiring high performance characteristics with respect to the noise induced by the transmission channel, comprising, at transmission, means for the suppressed carrier amplitude modulation of a useful signal and means for the amplitude modulation, in phase quadrature with said modulated useful signal, of a service signal, making it possible, at reception, to remove the ambiguity on the polarity of the demodulated useful signal. Thus it enables the transmission of signals in suppressed carrier modulation mode, hence with a good signal-to-noise ratio, without losing the polarity of the signal. The transmitters and receivers according to the invention also enable the transmission and reception of the signals modulated in SCAM, VSBAM or VSBSCAM modes.

Abstract: A digital amplitude modulation apparatus for amplitude-modulating a digital carrier having a frequency fc by a digital modulating wave associated with a sampling frequency fs1, at a sampling frequency fs2, wherein the conditions m.times.fs1=fs2, and fc=n/4.times. fs2 are satisfied, where m is a positive integer (2, 4, 6, . . . ) and n is a positive integer (1, 3, 5, . . . ). A fold distortion relative to an original digital amplitude modulated wave is not generated even if a fold component elimination filter is not used.

Abstract: A direct frequency modulation crystal-controlled oscillator circuit is provided having a configuration which minimizes the number of parts required for modulation while maintaining a linear relationship between the incoming modulation voltage and the outputted frequency. The circuit includes a tuning diode in a parallel arrangement with a tank circuit connected to the collector of a transistor. In the preferred embodiment, the tank circuit includes only an inductor. The crystal of the circuit operates in the anti-resonant mode and its impedance is much greater than that of the tank circuit. Direct frequency modulation results from the frequency change of the crystal in responding to a phase change caused by the modulation voltage applied to the tuning diode, which subsequently results in a change in the phase of a transistor collector voltage.