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| Number | Title | Issue Date |
| 5105445 | Predistortion arrangement for a digital transmission system Predistortion arrangement (9) for a digital transmission system transmits complex input data of a constellation by means of a modulator (14) and a power amplifier (15) which distorts the data. The arrangement comprising a predistortion circuit (11) which ... | 04/14/1992 |
| 5105446 | Digital method of correcting non-linearity in a transmission chain, and apparatus implementing the method The invention provide a digital method of correcting non-linearity in a transmission chain, in which the effects of amplifier non-linearities are compensated by applying predistortion in baseband prior to modulation, with the signal being processed digita... | 04/14/1992 |
| 5105442 | Coded modulation with unequal error protection Digital signals, such as digitized television signals, are subjected to a source coding step in which a class of "most important" data elements represents a proportionately greater amount of the information to be communicated than the rest of the data ele... | 04/14/1992 |
| 5091919 | Transmitter arrangement for digitally modulated signals A radio transmitter arrangement for e.g. QAM signals comprising a class C output transistor amplifier (AMP). The control voltage generator (CVG) comprises a memory, whereby the I,Q-signals (I,Q) of the modulating signal (DM) address the control voltage ge... | 02/25/1992 |
| 5077757 | System for synthesizing a modulated signal A modulation system and associated method therefor for synthesizing a modulated signal. Information is converted into an in-phase signal portion and a quadrature signal portion. The two signal portions are combined by summation and difference operations, ... | 12/31/1991 |
| 5054037 | Method of servo-controlling the parameters of a modulator having 2n phase and amplitude states, and a circuit for implementing the method Servo-controlling position in a modulator having 2n phase and amplitude states (used for e.g. 16-QAM radio beam transmission) is achieved by monitoring the amplitude of the signal output from the modulator. In a first or inner loop, any constel... | 10/01/1991 |
| 5041793 | Controlled slew rate amplifier An adjustable slew rate amplifier in the input stage of an amplifier circuit helps reduce off-channel frequency splatter. In instances where test sequences are input to an amplifier circuit that are used to measure maximum permissible input levels to the ... | 08/20/1991 |
| 5012208 | Quadrature modulator having compensation for local oscillator leak The invention relates to a quadrature modulator comprising a circuit for the compensation of a local oscillator leak signal in an output signal of the modulator, which circuit adds different compensation voltages to two modulation signals. To provide an a... | 04/30/1991 |
| 4999590 | Four state phase shift modulator, in particular for amplitude modulation of two carriers in quadrature with a large number of states A QPSK modulator has a signal generator which generates four carrier outputs having respective phases of 0°, 90°, 180°, and 270°. A four input phase selector is connected to the four outputs of the generator, has four modulator signal inputs, and has ... | 03/12/1991 |
| 4993021 | Automatic transmit power level control in radio links The automatic transmit power level control in multiline radio links using a multilevel QAM modulation is basically comprised of: means to derive a threshold signal for each RF channel in each receiver, means to multiplex all threshold signals from the individual re... | 02/12/1991 |
| 4990867 | Modulator In a modulator for converting two digital signals of I channel and Q channel in base band into analog signals and for converting a component of the signals whose phase is the same as a carrier and another component of the signals whose phase is orthogonal... | 02/05/1991 |
| 4991164 | Automatic transmit power level control in radio links A system for stabilization of the coupling value between the transmitted radio signals resulting from cross polar discrimination, using the transmit power level control in radio link systems formed of several radio channels using multilevel QAM modulation... | 02/05/1991 |
| 4974236 | Arrangement for generating an SSB signal An SSB generator in which a digitized analogue signal is processed in accordance with Weaver's method. The baseband I and Q signals are interpolated at a sampling frequency fs in respective first interpolators (30, 32). The interpolated signals... | 11/27/1990 |
| 4965536 | Quadrature amplitude modulation system using digital filters A modulating device applicable to a digital radio communications system which is adaptable to a 16 or greater multi-level QAM modulation system. The device has two multi-input digital filters to implement the role of cosine roll-off filters. A logic circu... | 10/23/1990 |
| 4962510 | Phase modulated system with phase domain filtering A phase modulation system includes a phase mapping circuit (218) for mapping binary data into a plurality of discrete phase values in accordance with a predetermined phase modulation scheme. The discrete phase values are then filtered in the phase domain ... | 10/09/1990 |
| 4940954 | Unbalanced quadrature PSK modulator-limiter An unbalanced quadrature phase-shift keyed UQPSK modulator modulates two information signals onto mutually quadrature components of a carrier. If the carrier components differ from an exact quadrature relationship by an error angle, crosstalk orr distorti... | 07/10/1990 |
| 4899367 | Multi-level quadrature amplitude modulator system with fading compensation means A multi-level quadrature amplitude modulator system that can be used in communication channels in which there is intense fluctuation has a transmitter section that is provided with a frame synchronizer that inserts a reference symbol into each group of me... | 02/06/1990 |
| 4890301 | Arrangement for compensating errors in a quadrature modulator An arrangement for compensating errors occurent in a quadrature modulator. Two quadrature signals (cos a(t), sin a(t)) in the baseband are generated, each of which signals is delivered to a respective branch in the modulator two high frequency signals (co... | 12/26/1989 |
| 4881049 | QAM modulator/demodulator A digital signal transmission system adopting a quadrature amplitude modulation and demodulation principle and feasible for large capacity data transmission in which a number of levels are used. Each of a modulating and a demodulating device of the system... | 11/14/1989 |
| 4860316 | Multilevel amplitude modulation and demodulation communication system A digital communication system using a QAM signal and a honeycomb constellation multilevel signal. The digital communication system includes a modulator having a unit for transforming in-phase and quadrature-phase data arranged in a quadrature lattice con... | 08/22/1989 |
| 4855692 | Method of quadrature-phase amplitude modulation A square array of signal points forming a QAM signal point constellation is modified by relocating signal points from corners of the square to positions extrapolated from the square array and at reduced distances from the origin, corresponding to reduced ... | 08/08/1989 |
| 4843351 | Vector modulation signal generator A novel vector signal generator is provided which includes a vector modulator controlled by baseband manipulation circuitry. The output signal from the vector modulator is down converted to a desired output frequency. The baseband manipulation circuitry p... | 06/27/1989 |
| 4801899 | Quadrature amplitude modulation/demodulation device using multi-level digital signals A modulation device using multi-level digital signals includes: a pair of balanced mixers for carrying out quadrature amplitude modulation to deliver a quadrature amplitude modulated signal; input and output hybrid circuits, connected to carrier input ter... | 01/31/1989 |
| 4759039 | Simplified recovery of data signals from quadrature-related carrier signals A technique is presented for simplifying the recovery of two synchronous data signals having a common symbol rate after each signal has respectively modulated a different one of a pair of quadrature-related carrier signals. In the transmitter, the data si... | 07/19/1988 |
| 4750191 | D/A converter capable of producing an analog signal having levels of a preselected number different from 2N and communication network comprising the D/A converter In a digital-to-analog converter, a digital input signal of x bits is subjected to digital-to-analog conversion with at least two of x bit positions recognized as a common bit position and converted into analog levels of a number which is different from 2... | 06/07/1988 |
| 4745628 | Symbol generator for phase modulated system A symbol generator is provided for generating a filtered analog waveform for use in phase modulating a carrier. A memory (30) is provided for storing predetermined waveform segments. The waveform segments are correlated with an input data stream. The data... | 05/17/1988 |
| 4737969 | Spectrally efficient digital modulation method and apparatus A method and apparatus are provided for generating a uniquely shaped prototype digital pulse which is transmitted with minimal frequency spectrum consumption and yet a relatively high bit rate. Such uniquely shaped digital pulse is stored in a memory incl... | 04/12/1988 |
| 4736170 | Unbalanced quarternary PSK modulator using unbalanced quadrature coupler An unbalanced quarternary phase-shift keying modulator provides relatively higher signal power for one of two signal information channels. The carrier to be modulated is split into two equal-amplitude, equal-phase portions, each of which is applied to a b... | 04/05/1988 |
| 4721928 | Multilevel modulator capable of producing a multilevel quadrature amplitude modulated signal having (2n +) output signal points In a multilevel modulator for use in modulating a main data signal of n bits and a subdata signal of a single bit into a multilevel quadrature amplitude modulated signal, the main data and the subdata signals have a first bit rate f1 and a seco... | 01/26/1988 |
| 4700151 | Modulation system capable of improving a transmission system In a modulation system responsive to a system input signal for supplying an amplifier having nonlinearities with a modulated analog signal to make the amplifier produce an amplified output signal, the system input signal conveys a baseband signal having a... | 10/13/1987 |
| 4696017 | Quadrature signal generator having digitally-controlled phase and amplitude correction A digitally-controlled quadrature signal generator is provided having a frequency synthesizer for receiving a digital input signal and in response thereto generating an output signal having a predetermined frequency. The output signal is split to produce ... | 09/22/1987 |
| 4675880 | Antimultipath communication by injecting tone into null in signal spectrum A transmitter for digital radio communication creates a null by balanced encoding of data modulated on an RF carrier, and inserts a calibration tone within the null. By having the calibration tone coincide in phase and frequency with the transmitted radio... | 06/23/1987 |
| 4661948 | Digital quadrature amplitude modulator In a quadrature amplitude modulator, two binary, synchronous data signals representing four possible phase states of a carrier signal are sampled and respectively fed into two shift registers comprising part of a finite impulse response lowpass filter. Th... | 04/28/1987 |
| 4644565 | Superposed quadrature modulated baseband signal processor A signal processor for providing a continuous raised cosine output signal having no jitter or intersymbol-interference and with controllable main and side lobes. An NRZ input signal is converted to a double interval raised cosine pulse signal having an am... | 02/17/1987 |
| 4626803 | Apparatus for providing a carrier signal with two digital data streams I-Q modulated thereon A digital I-Q modulator provides an analog signal at a desired frequency ω1 with in-phase I and quadrature-phase Q modulation sidebands provided responsive to different associated ones of in-phase I and quadrature-phase Q digital data streams,... | 12/02/1986 |
| 4571549 | 16-QAM Modulator with PLL amplification devices A 16-quadrature amplitude modulation (QAM) modulator for radio links converts a train of data into signals having a phase selected from sixteen predetermined phase values and an amplitude selected from four values. The modulator divides the data train int... | 02/18/1986 |
| 4534040 | Method and apparatus for coding a binary signal An input bit sequence is encoded for transmission on a QAM carrier by dividing a scrambled version of the input sequence into groups of N consecutive bits. Each group is then subdivided into first and second subsets of r and r1 bits, where r+r | 08/06/1985 |
| 4483012 | Differentially convolutional channel coding with expanded set of signalling alphabets A technique for converting a sequence of binary digits into a sequence of signalling alphabets of a modulated carrier signal for data transmission. By introducing additional redundant signalling alphabets and differentially coding incoming data in a state... | 11/13/1984 |
| 4464767 | System for generation of multiple pointed QAM signal spaces by use of synchronous Qam transmitters A system for the generation of many-pointed QAM signal spaces by use of multiple, synchronous QAM transmitters is provided. Three individual relatively low BPS data rate transmitters have their outputs connected to different weighting multipliers. The out... | 08/07/1984 |
| 4244047 | Multiplexed carrier transmission through harmonic polluted medium Multiplexed carrier signals modulated with digital data are transmitted through a medium polluted with harmonic signals by asymmetrically positioning the frequency of one of the carrier signals between two of the adjacent system harmonics, modulating that... | 01/06/1981 |
