Abstract: A data transmission system includes a source of a data signal and a modulator, responsive to the data signal, producing a first modulated signal representing the data signal and a second modulated signal representing a signal 180 out-of-phase with the data signal. The first and second modulated signals are transported via a transmission channel. A first demodulator demodulates the transported first modulated signal and a second demodulator demodulates the transported second modulated signal. A subtractor, responsive to the first and second demodulators, produces a signal representative of the data signal.

Abstract: In an amplitude-modulated broadcast transmitter for various types of modulation, particularly DSB (double sideband), SSB (single sideband) and ISB (independent sideband), of at least one AF signal to be transmitted, the sum and the difference is formed from the two input channels (7a, 7b). Either the sum or the difference is subjected to a Hilbert transformation in a Hilbert transformer (12). From these signals, an amplitude signal is formed in an amplitude processor (22) and a phase signal is formed in a cyclic sampler (21) and a phase conditioner (23). The amplitude signal is used for anode modulating the transmitting tube (5) and the phase signal is used for grid modulating the transmitting tube. The amplitude-modulated broadcast transmitter for various types of modulation has the advantage that the three types of modulation ISB, DSB and SSB can be set by allocating the AF signals to be transmitted to the two input channels (7a, 7b).

Abstract: Transmitting signals containing amplitude modulated (AM) and phase modulation (PM) components requires a transmitter having AM and PM control loops. The PM control loop provides phase modulation, frequency translation and phase predistortion for the transmitter. The phase predistortion/correction is accomplished by using an oscillator, thus, the amount of PA phase correction is essentially unlimited. Additionally, the PM control loop is nested about a power amplifier (PA), allowing the PM control loop to correct for any distortion introduced by the PA.

Abstract: The present invention relates generally to RF power amplifiers for portable cellular radiotelephones, and more particularly, to dual-mode cellular radiotelephones. A power supply network enables the RF power amplifier in a dual-mode radiotelephone to operate with two separate modes: saturated and unsaturated. Switches in the power supply network, e.g. complementary transistors, are driven to a first set of logic states by a square wave which is synchronized with transmit time slots present in a TDMA frame structure to charge a capacitor from a battery. When the switches are then driven to a second set of logic states, the capacitor is placed in series with the battery to essentially double the supply voltage. When the radiotelephone operates in a digital mode, the increased supply voltage coincides with the transmit time slot and temporarily increases the saturation point of the RF power amplifier to permit linear amplification.

Abstract: A digital exciter (30) for selectively modulating digital or analog input data. The digital exciter includes a digital signal modulator (32) and a digital quadrature modulator (DQM)(36) comprising two digital signal processors (DSPs). The signal modulator is controlled by a control (40). An operator can selectively determine whether the digital exciter is used for modulating either two level or four level NRZ digital data and whether the device is to provide linear modulation or frequency modulation (FM) of the input signal. An interpolator (38) interpolates a 662/3 kHz timer interrupt rate used in the signal modulator to a 400 kHz rate, thereby reducing the processing load on the DSP comprising the DQM by simplifying the sine and cosine values used in the quadrature modulation. An operator can select from among a plurality of operating parameters on a menu for controlling the signal modulator, either from a local or a remote video display terminal (VDT).

Abstract: The process according to the invention consists in breaking down a radiofrequency signal to be modulated according to a first and second signal, representing respectively the sum of the output voltages of identical amplitude of a first and second determined number of modules, with which respectively a first and second vector are associated whose respective amplitude and phase verify that the vectorial sum of the two vectors coincides with a determined reference that is used as a phase reference of the two vectors, in adapting the phase of the load impedance of each module so that vector associated with the current supplied by each of the amplifying modules is in phase delay in relation to their output voltages, in modulating the phase of the two signals by the modulation signal and in adding the first and second phase modulated signal to obtain a resultant amplitude modulated signal. Application: Medium wave radio broadcast transmitters.

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 numerically-controlled modulated oscillator and modulation method which selectively provides frequency modulation, phase modulation or amplitude modulation with minimal circuitry. A numerically-controlled modulated oscillator is provided having a tuning register for receiving a center frequency parameter, an adder for receiving at one input the frequency parameter, a phase accumulator for receiving a phase increment number from the adder and producing a waveform phase number, a waveform memory for producing a waveform amplitude number in response to the phase number, and a digital-to-analog converter for producing an analog signal in response to the waveform amplitude number. Another input is provided to the adder from an angle modulation register which provides an angle modulation parameter. This parameter can perform either phase or frequency modulation.

Abstract: A method of and apparatus for telemetering both analog and digital data transcutaneously between an implantable medical device and an external receiver, such as between an external programmer and an implantable cardiac pacer. A damped carrier at 175 kilohertz is pulse position modulated by digital data. The data, along with synchronization and identification codes, are positioned into predefined ranges within predefined frames as measured by individual time periods. The data is uniquely identified by the position of a burst of the carrier within the predefined range. An automatically initiated hand shake protocol maintains the link over slight variations in programmer head position with an indicator notifying the operator when repositioning is required. Analog data may be transferred in digital form or alternatively transferred using phase modulation of the carrier bursts. A cyclic redundancy code is used for link error detection.

Abstract: A device and a method for the transmission or storage of data optimizing the use of the pass-band. Also, a method for transmission by phase modulation. In order to obtain high data throughput rates, the synchronization of a transmission clock with the reception clocks is used. This synchronization is gotten, for example, by transmission of a pseudo-random code and by the convolution or correlation of the received signals with the pseudo-random code. The invention also enables the elimination of multiple echoes by computation. The invention can be applied chiefly to the transmission of radio programs, television broadcasts or digital data.

Abstract: A multiplication circuit for use in an FM television transmitter and receiver is provided. The multiplication circuit includes a limiting circuit for limiting a subcarrier supplied thereto and a dividing circuit coupled to the limiting circuit and dividing the output of the limiting circuit by a predetermined factor. A mixer is coupled to the dividing circuit and mixes the output of the dividing circuit with the subcarrier.

Abstract: In a vestigial sideband modulator, an i.f. signal is modulated with a video input and the extreme part of one of the sidebands is removed to provide the right frequency response shape for transmission. The signal for transmission is usually produced by mixing the i.f. signal with an oscillator signal known as the heterodyne signal which differs from the desired carrier frequency by the i.f. frequency, and filtering the signal with a subsequent channel filter to remove any unwanted heterodyne oscillator components and the unwanted sum or difference product. To avoid the need for such a channel filter, the filtered video-modulated i.f. signal is demodulated to quadrature baseband components using the i.f. oscillator, and quadrature components at carrier frequency are modulated with these baseband components to produce on combination a v.s.b. modulated video output at carrier frequency.

Abstract: A cellular-telephone transmitter (10) employs a vector modulator (14). An integrating circuit (52) generates the integral of the message signal and applies it to circuitry (54, 56) for generating in-phase and quadrature modulation signals representing the cosine and sine, respectively, of the integrating-circuit output. The vector modulator (14) produces the desired FM signal by adding together quadrature and in-phase versions of a carrier in proportion to the values that the quadrature and in-phase modulating signals represent.

Abstract: This invention is a multiple-frequency signal generator apparatus and method primarily for simulating a cell site interference environment for electromagnetic communications systems. The generator can produce a plurality of frequencies having a frequency-spacing of d cycles per second. The invention comprises a single frequency multiplier, at least three oscillators and two mixers for providing a multitude of frequencies closely spaced about a carrier frequency. The simple design and components avoid complexity and save costs.

Abstract: A microwave system is provided for the broadcast of multiple channels of audio programming to a wide listener base, in which noise-free transmission of multiple audio channels is accomplished through microwave transmission followed by down converting the received signal to television band frequencies, accomplished in one embodiment through the use of a single MDS channel.

Abstract: A new method of modulating and demodulating signals and circuitry therefor is disclosed. The modulation circuit defines a non-linear voltage current transfer function wherein at low voltage levels the current voltage transfer function is substantially linear and at higher voltages, the transfer function is substantially exponential. The modulation circuit can be designed of three parallel branches, a resistive branch, and two diodes in the remaining branches, the anode of one diode being coupled to the cathode of the other diode. Demodulation circuitry is also disclosed that includes a circuit for determining the instantaneous phase and amplitude and then processing circuitry to decode the modulation information based upon the sampled phase and amplitude data.

Abstract: In a transmitter, a modulator switchably operates on one of two modes of operations, that is, in a first mode of the operation, such as an offset QPSK, FSK or .pi./4 shift QPSK, an amplitude of an output signal of the modulator does not become zero at any instant, and in a second mode of the operation, such as two-phase FSK or four-phase PSK, the output signal of the modulator is 100% amplitude-modulated or 180 phase-modulated. Second mode operation. The operation mode is switched by changing the mode of the parallel input signals to the modulator, where the parallel signals have been converted from a serial input data signal to be transmitted.

Abstract: An amplitude modulated RF amplifier using dual path modulation to increase operating efficiency. Both the RF drive to the amplifier and the DC power supply voltage to the amplifier are amplitude modulated. Preferably, the power supply modulation is accomplished with a high efficiency pulse width modulator circuit. To prevent phase shift distortion, the modulated DC output from the power supply is used both to power the RF amplifier and to amplitude modulate the RF drive to the amplifier. For maximum efficiency, the modulators are both non-linear. Maximum efficiency is realized with primarily supply modulation and some drive modulation providing the positive envelope modulation and primarily a non-linear RF drive modulation providing the negative envelope modulation. The use of primarily RF drive modulation for the deep negative modulation will reduce the amount of incidental phase modulation experienced, while having a nearly inconsequential effect on total efficiency of the RF amplifier.

Abstract: A modulator circuit comprises an input for receiving an audio frequency (AF) signal, an oscillator circuit for providing a carrier wave signal, a mixer circuit for mixing the AF input signal with the carrier wave signal to provide an AM modulated signal, a switch having a first position in which the AM modulated signal is provided to an output and the switch having a second position in which the AM modulated signal is provided to a vector adding circuit where the AM modulated signal is vector added to the carrier wave signal, and the circuit including phase shift circuitry for shifting the phase of the AM modulated signal prior to vector adding with the carrier wave signal whereby to provide an FM modulated version of the AF input signal on the oscillator carrier wave.

Abstract: An RF modulator according to this invention is constructed so as to allow channel setting without a test pattern generator. Specifically, the RF comprises an A/D converter for digitizing the TV channel setting data, an oscillator control circuit for controlling both the audio carrier oscillation and the RF carrier oscillation on the basis of the channel setting data digitized by the A/D converter, a signal adder for combining the video signal amplitude-modulated at the frequency of the RF carrier oscillation with the audio signal frequency/amplitude-modulated at the frequency of the audio carrier oscillation, channel picking-up means for picking up a portion near the center of each channel in the channel setting data, and a clipper circuit for cutting of the video signal at both ends of each channel setting range that have not been picked up by the channel picking-up means.

Abstract: A method and device are set forth for, where a linear transmitter has inphase and quadrature modulation paths for an input signal and at least one open feedback signal path is provided, substantially correcting an initial phase relationship between an input signal having an input signal vector with a phase and a magnitude, and an input feedback signal having an input feedback signal vector with a phase and a magnitude. The present invention provides a more time-efficient phase correction to at least one feedback signal path.

Abstract: An RF modulator comprising an FM modulator supplied with an audio signal, and AM modulator supplied with the FM modulator output and a video signal, an oscillator for generating a sound subcarrier signal, and an oscillator for generating a main carrier signal. Each of the oscillators consists of a VCO with a PLL circuit, and the entire components are composed of a single IC chip so as to be formed into a compact miniature structure. A modified RF modulator includes a PLL circuit for varying the oscillation frequency of a VCO by a variable frequency divider, and a modulation circuit supplied with a modulating signal and the oscillation output of the VCO. The division ratio (integer) of the variable frequency divider is continuously varied, and the reference frequency of a reference oscillator is set to be less than a predetermined channel interval frequency, thereby reducing the frequency error in the modulated signal output.

Abstract: The present invention is a method and apparatus for providing an output signal having a high average power and the method has the steps of providing a standard frequency; forming a plurality of input signals from the standard signal such that each of the input signals has a predetermined frequency which is different from the frequencies of the other input signals; phase shifting at least one of the input signals such that at least one of the input signals has a phase different from the phase of the other input signals; combining all of the input signals to produce a combined signal; and amplifying the combined signal to produce the output signal. In one embodiment all of the input signals are phase shifted relative to one another and in another embodiment all of the input signals are equally phase shifted relative to one another except for one which is of opposite phase. Also all of the input signals are equally spaced in frequency relative to one another or have a common divisor in spacing.

Abstract: A transmission link for transmitting a sequence of signals comprising pulse and interval signals, across a transmission medium from a transmitter to a receiver circuit of a receiver, whereby each pulse signal is modulated with a frequency. At least two frequencies are used to modulate the pulses, and a separate evaluation circuit is provided in the receiver for each modulating frequency. The output signals of the evaluation circuits are concatenated (linked in series) by a AND-gate circuit.

Abstract: A transmitter generates three signals for sequential transmission. These signals are an unmodulated r.f. carrier, an r.f. carrier amplitude modulated by a first audio frequency waveform and an r.f. carrier amplitude modulated by a second audio frequency waveform which is distinguishable from the first and which may be employed as a means for identifying a particular transmitter. The composite, sequentially transmitted signal may be varied in terms of the individual signal transmission sequence, the duration of the individual signals, overall composite signal repetition rate and the frequency of the second audio waveform. Various combinations of signal variations may be employed to transmit different information.

Abstract: A radio transceiver is disclosed for use in an SSB communication system having FM data capability. The dual-mode radio transceiver of the present invention includes a receiver capable of demodulating and deriving AFC from either (a) the voice channel having voice messages transmitted via single sideband amplitude modulation with a pilot carrier, or (b) the data channel having high speed data messages transmitted via narrowband frequency modulation in the same channel bandwidth. Furthermore, the dual-mode radio transceiver includes a transmitter capable of transmitting one of either of the above types of modulation on the appropriate channel, as determined by information received from the high speed data messages transmitted on the control channel.

Abstract: A privacy signal transmission system having a transmitter portion and a receiver portion. The transmitter portion digitizes an analog message signal and enciphers the digitized signal into a privacy signal before modulation and transmission to the receiver portion. The transmitter portion also extracts and modulates an analog error signal representative of the digitization error for transmission to the receiver portion. The receiver portion demodulates the digitized privacy signal and analog error signal, and after the privacy signal is deciphered and reconverted to an analog signal it is added to the received analog error to reconstitute the original analog message signal.

Abstract: A four-channel multifunction digital frequency synthesizer which uses direct numerical synthesis to generate one or more complex output signals having selectable frequency, phase offset, amplitude level and waveform is provided. A waveform synthesizer digitally synthesizes precise sine, square, triangle, ramp, uniform and Gaussian noise and DC waveforms which can be selected for any of the four channels. One of the four channels can be frequency, phase and amplitude modulated by the signals on the remaining three channels in any combination. The four channels are time-multiplexed which allows the use of a single frequency synthesizer to realize four independent channels and a large number of support functions and capabilities in a high-density VLSI integrated circuit on a single chip. The synthesizer system can provide up to four independent output signals which can be any one of the four channel signals, or any combination of the four channel signals summed to form a complex waveform signal.

Abstract: A process and apparatus for simultaneously broadcasting a first intelligence signal with a plurality of second intelligence signals is disclosed. The transmitter performs the following steps: multiplexing the plurality of second intelligence signals into a single signal to form a first modulating signal; frequency modulating a first radio frequency carrier signal with the first modulating signal to form a second radio frequency carrier signal; amplitude modulating the second radio frequency carrier signal using the first intelligence signal as a second modulating signal; and broadcasting the resultant single radio frequency signal out over a transmitting antenna.

Abstract: FM transmission system in which, besides program content, an auxiliary carrier of, for example 57 kHz, is radiated, which auxiliary carrier is modulated by an announcement recognition (AR) signal and by a region or radio-station recognition (RR) signal, the AR and RR signals being low-frequency, AM modulations on the auxiliary carrier. To enhance recognition of an AR signal, e.g. between 142 and 170 Hz, is enhanced, in spite of reception difficulties, for example due to multi-path reception and the like, by decreasing the modulation of the 57 kHz subcarrier by the RR signal to 30% or less, while the AR signal is modulating the subcarrier, so that the AR modulation may extend to 60 and even 90% modulation. Multiple AR frequencies can be used, for example to characterize different announcements, e.g. in different languages, or of different characteristics, such as traffic, news, sports, or others, recognition of the AR signal in the receiver permitting switch-over from other reproduced programs, e.g.

Abstract: An amplitude modulated radio transmission system is described which is compatible with conventional AM receivers. The transmitted signal comprises a carrier and two unequal amplitude sidebands. This signal can be received by receivers that are tuned to the carrier as well as receivers that are off tuned to favor the stronger sideband.

Abstract: An apparatus for frequency-modulating telecommunication carriers with baseband signals includes an arrangement for generating two quadrature-related baseband signals in two separate channels, wherein each of the quadrature-related baseband signals is a sinusoidal function of the instantaneous angle of the message signal to be transmitted. The apparatus further includes an arrangement for producing a frequency-modulated carrier from the quadrature-related baseband signals, this arrangement including a device that provides two quadrature-related carrier-frequency waveforms, two mixing devices each for individually mixing one of the quadrature-related carrier-frequency waveforms with one of the quadrature-related baseband signals in one of the channels, and a combining device which combines the output signals from the two channels into a single frequency-modulated carrier-frequency output signal.

Abstract: A single sideband communications system conveying a message through a transmitter to one or more predetermined receivers which are enabled by a coded squelch signal unique to the predetermined receivers is disclosed. The transmitter comprises means to angle modulate both the pilot signal and the information bearing single sideband signal with the coded signal at a predetermined deviation and to transmit the resulting signal.Each receiver frequency control means tracks the frequency excursions of a selected portion of the transmitted signal up to predetermined limits so that the message can be demodulated without frequency distortion being introduced. Each receiver demodulates the coded squelch without interfering with the message demodulation or tracking functions and activates the receiver squelch of those preselected receivers.

Abstract: In equipment for transmitting or re-transmitting television signals comprising, in the intermediate frequency stage, group propagation time correction cells for linearizing the phase-frequency characteristic of the equipment, the non linearity correction system of the invention uses these cells while completing them with an amplitude pre-modulation control circuit and/or a frequency premodulation control circuit, for correcting amplitude and phase non linearities affecting the pole carrier frequencies of the correction cells.

Abstract: An electronic arrangement for generating an amplitude and phase-modulated carrier signal having a phase modulation stage with two inputs for receiving two modulation signals, which modulation stage generates two different phase-modulated signals having the same carrier frequency and substantially the same amplitude, and an output stage to which the phase-modulated signals are applied for assembling by means of summation of the phase-modulated signals to produce the amplitude and phase-modulated carrier, the amplitude of which is modulated in dependence on the phase difference of the phase-modulated signals and the phase of which is modulated in dependence on the sum of the phases of the phase-modulated signals.

Abstract: A method and apparatus for phase modulating a carrier signal to convey an information signal (12) such that the carrier signal has a constant amplitude envelope. A Hilbert transform signal (14) of the information signal (12) is produced. The signals (12, 14) are sampled to produce signals (16, 18), which represent cartesian coordinate values. The cartesian coordinate values are then converted into equivalent polar vectors (20-36) which have both an amplitude (R) and an angle (.theta.). The polar vector quantity (R,.theta.) is converted into two unity amplitude vectors (A, B). The unity amplitude vectors (A, B) are offset from the polar vector quantity by an angle the cosine of which is proportional to the amplitude of the polar vector (R). The carrier signal is sequentially phase modulated by each of the angles of the unity amplitude vectors (A, B) for each sample period of the information signal.

Abstract: In a system for transmitting a charging signal from an exchange to a telephone system together with a voice signal, radio equipment in the exchange side detects the charging signal sent from the exchange and encodes it into a pulse code signal comprising a plurality of continuous pulses. Thereafter, this pulse signal is modulated into a frequency signal outside the voice transmitting frequency band and then transmitted as a radio signal after it is superimposed on the voice signal. Radio equipment on the telephone side detects this charging signal carrier and demodulates it into the pulse code signal, then counts it and transfers the charging signal when the counted value reaches a specified value.

Abstract: A frequency modulator for radio frequency (RF) signals is described that symmetrically modulates the RF signal with either binary signals or voice signals without distorting the amplitude of the binary signal near bit edges. The inventive frequency modulator includes a reference signal generator, a phase comparator for comparing the reference signal and a feedback signal to provide an error signal, a filter for filtering the error signal, a voltage-controlled oscillator (VCO) responsive to the filtered error signal for generating an output signal, a divider for dividing the VCO output signal by a predetermined number to provide the feedback signal, circuitry coupled to the VCO for modulating the VCO output signal with the binary signal, and circuitry coupled to the divider for varying the predetermined number of the divider between a first predetermined number and a second predetermined number in response to the binary signal.

Abstract: To minimize carrier leak in the modulation of voice frequencies to the desired line frequency for a carrier system, a first balanced modulator is operated at a low frequency where low carrier-leak modulators may be constructed and a second balanced modulator, directly coupled to the first, is employed. The modulation frequency of said second modulator is very high compared to that of said low-frequency modulator. The sideband obtained from the second modulation stage is remote from said high-frequency carrier and a band-pass filter selects the desired sideband and substantially eliminates the high-frequency carrier and the other sideband. Thus, only a low amplitude of carrier leak is present which may cause interference with other channels.

Abstract: To permit mass-production of coders selectively usable in various types of transmitter installations, and regardless of whether designed for stereophonic or monophonic transmission, in which a subcarrier of non-audible frequency (57 kHz) is radiated, amplitude modulated by separate recognition signals characterizing intelligence information (AR, or announcement recognition) and a specific transmitter (region or radio station recognition, RR), a memory element (36) such as a PROM is provided, connected to a selector switch, the memory element having stored therein data representative of(1) frequency of amplitude modulation of the subcarrier of the announcement recognition (AR) signal;(2) frequency of amplitude modulation of the radio station recognition (RR) signal;(3) degree of modulation by the (AR) signal;(4) degree of modulation by the (RR) signal, and,preferably, data to provide a visual indication of a respective frequency channel and modulation degree, the memory element (36) being programmed for select

Abstract: Public alert and advisory systems for the communication of emergency and/or other information from one or more central locations to a plurality of remote locations, such as, by way of example, information regarding a nuclear accident and evacuation procedures. This system utilizes conventional programming stations such as AM, FM or TV stations, central transmitting equipment, with the emergency information being modulated by a second modulation technique differing from the first modulation technique for the ordinary programming so that conventional manually operated programming receivers will not be responsive to the emergency information. The receivers of the system however, are responsive to the transmitted emergency information, so as to sound a warning alarm, display codes relating to evacuation or other information and/or receive and present audio information depending upon the specific configuration of the system.

Abstract: In a system for frequency-diversity transmission, separate and distinct frequency carriers are obtained from the frequency modulation of an oscillator by a pure frequency with an index such that a certain number of Bessel lines thus obtained constitute a corresponding number of separate carriers. All the carriers are subsequently modulated by the information, then power-amplified in a single amplifier having a peak power equal to that of a single signal whose effective power would be the sum of those of the separate carriers. By means of this system, equipment for radio communication by tropospheric or ionospheric scatter propagation can be constructed in a simple manner and at low cost, with a high diversity order.

Abstract: In a method of transmitting data and speech signals over a telephone system through which communication is effected via a radio link, the data and the speech signals are separated in the frequency domain, and are transmitted in respective separate sideband channels. The data sideband channel contains sidebands generated by time coding an otherwise continuous wave signal. The latter signal may be a carrier signal which is modulated to convey the speech signals.

Abstract: A submultiple (30Fl) of an S-band transmitter output frequency (240Fl) is divided equally between a linear phase modulation branch and a QPSK modulation branch. The linear modulation branch includes a multiplier (X7) to increase the carrier frequency to a level (210Fl) which, when combined with the carrier in the QPSK branch in an up-converter (utilizing a mixer at the input thereof followed by a bandpass filter), produces the transmitter output frequency. This allows the QPSK modulator to operate at one-eighth of the output frequency where repeatable and precisely controlled modulation can be easily achieved. This also allows linear phase modulation at one-eighth the output frequency where low modulator deviation and good linearity can be easily maintained.