Abstract: An RF amplifier for a transmitter develops a phase modulation command representing a desired phase modulation of an RF signal, and an amplitude modulation command representing a desired amplitude modulation of the RF signal. An oscillator develops an RF input signal phase modulated based on the phase modulation command. A power amplifier receives the RF input signal and amplifies the RF input signal based on the amplitude modulation command to develop an RF output signal. A modulation control is operatively associated with the oscillator. The modulation control includes a phase memory for storing phase correction information correlating the amplitude modulation commands to a phase modulation error and a phase control for varying the phase modulation command based on the phase modulation error to correct for unintended phase errors created by amplitude modulation of the power amplifier.

Abstract: In a transmitter (200) that includes a radio frequency (RF) power amplifier (218), a predistortion signal loop (234, 240, 209, 208), and a feedforward correction loop (242, 246, 248, 250, 252, 258, 261, 262), a method and apparatus is provided for correcting distortion introduced into the transmitter by the RF power amplifier. The predistortion signal loop determines a RF power amplifier characterization function that characterizes a relationship between a signal input into the RF power amplifier and the resulting signal output by the RF power amplifier. The predistortion signal loop also determines a predistorted input signal that is based on an input signal received from an information source and on the RF power amplifier characterization function, which predistorted input signal is input into the RF power and includes input signal modifications that are meant to compensate for the distortion introduced introduced by the RF power amplifier.

Abstract: A system and method for determining dispersion of intermodulation power in a satellite communication system or any other system which can be mathematically modeled as a matrix multiplication followed by an instantaneous nonlinearity and another matrix multiplication include determining a matrix (V) representing amplitudes and frequencies of signals generated by a digital processor and input to a plurality of amplifiers. A matrix (M) representing signal propagation from the amplifiers to a destination is used to determine the intermodulation power at the destination within each transmitted beam at each intermodulation distortion frequency. The intermodulation distortion frequencies are determined based on sums and differences of component frequencies corresponding to the user signals.

Abstract: A method and a circuit for high-efficiency linear RF-power amplification over a wide range of amplitudes from zero to peak output includes a final RF-power amplifier operating at or near saturation, an RF driver amplifier, a high-level amplitude modulator for the final amplifier, preferably a high-level amplitude modulator for the driver amplifier, and a means for determining the supply-voltage input to the final amplifier and for controlling the amplitude of the drive. The means for determining the supply-voltage input and for controlling the amplitude acts so that the final amplifier drive varies from a minimum level to peak as the desired transmitter output varies from zero to peak. The transmitter is preferably of the envelope-elimination-and-restoration type or the envelope-tracking type.

Abstract: A central terminal (10) in a wireless telecommunications system (1) includes an analog card (206) that combines inputs from a plurality of modem units (204) for a plurality of downlink communication paths. The analog card (206) generates a composite transmit signal (214) that is provided to a radio frequency card (208). The radio frequency card (208) prepares the composite transmit signal (214) for radio frequency transmission from the central terminal (10). A power amplifier (218) in a combining shelf (201) amplifies the composite transmit signal (214) to a desired transmitting level. A detector (240) measures a power output of the power amplifier (218). The power output measurement determined by the detector (240) is collected by a combiner monitor (222) and delivered to a shelf controller (210) of the modem shelf (200). The shelf controller (210) provides the power output measurement to the analog card (206).

Abstract: A transmitter provides a radio wave with selectable polarization. The transmitter includes antenna feeds that generate orthogonal radio waves having non-linear polarizations that corresponds to the selectable phase relationships of a first and a second modulating signals. A spacial combination of the non-linear radio waves to produce a linearly polarized radio wave that has an orientation corresponding to a selected phase relationship.

Abstract: A multiband mobile unit communication apparatus is disclosed which comprises: an antenna for receiving L FRQ bands of M radio wave SIGs modulated by N modulating methods, M>L, M>N, N≧L; a frequency synthesizer for generating a LO SIG; an IF SIG generation CKT for generating M IF SIGs using the LO SIG, the FRQ synthesizer generating the LO SIG such that the M IF SIGs have the same intermediate FRQ; a SW CKT for selectively outputting N IF SIGs modulated by the N modulating methods respectively out of the M IF SIGs; N filters for filtering outputs of N IF SIGs from the SW CKT and outputting N filtered IF SIGs respectively; a SW responsive to a SW CONT signal for selectively outputting one of the N filtered IF SIGs; and a quadrature demodulator for quadrature-demodulating one of N filtered IF SIGs and outputting baseband SIG. Different frequency bands of received signals are converted into IF SIGs having the same intermediate frequency.

Abstract: A transmitter system (18) which transmits a communication signal (14) through a phased-array antenna (10) uses a signal processor (26) and a multiplicity of direct modulators (30). Each direct modulator (30) drives a single element (12) of the antenna (10). Each direct modulator (30) receives a digital baseband phase point data signal (62) from a digital data stream (28). The digital data stream (28) also conveys digital beam formation data (60). Each direct modulator (30) digitally combines the baseband phase point data (62) with the beam formation data (60) to produce digital streams that modulate an RF carrier signal (34). The digital data stream (28) is generated by a phased-array signal processor (26) which processes user data bits (86) received from any number of input signals (22) and processes beam signals (24). In one embodiment, the signal processor (26) calculates phase point data (62) representative of all input signals (22).

Abstract: A transmitter for a cellular phone comprising an antenna and being operable at a first radio frequency band and a second radio frequency band is disclosed. The transmitter comprises a first power amplifier and a second power amplifier. The first power amplifier has a first input for a first signal at the first radio frequency band, a second input for a first control signal and a first output for an amplified first signal. The first output is connectable to the antenna. The second power amplifier has a third input for a second signal at the second radio frequency band, a fourth input for a second control signal and a second output for an amplified second signal. The second output is connectable to the antenna. The transmitter further comprises a single control module which receives a signal indicative of a current an active power amplifier draws. The control module uses this signal indicating the drawn current to generate a control signal to control the active power amplifier.

Abstract: A method for use in a dual mode wireless communication system supporting at least a first modulation method and a second modulation method, wherein the first and second modulation methods are used on different RF channels, wherein a wireless transmitter is capable of supporting both modulation methods, and wherein it is preferred that emergency 911 calls generally take place with the first modulation method, comprising the steps of: when the wireless transmitter is currently using the second modulation method and attempts to originate a call to 911, causing the wireless transmitter automatically to switch to the first modulation method; and originating the call to 911 using the first modulation method on one of the set of RF channels prescribed for use in the first modulation method.

Abstract: An apparatus and method generate a linearly modulated signal in a polar modulation system. A signal for transmission is separated into a phase component and an amplitude component, and a carrier signal is modulated with the phase component in a phase modulator, creating a phase distortion. A compensator compensates for the phase distortion created by the phase modulator by modifying the amplitude component. The phase modulated carrier signal is amplitude modulated by the compensated amplitude component to produce a linearly modulated signal.

Abstract: A transmitter circuit for use in a mobile radio using both a normal frequency transmission band and a talk-around frequency transmission band is disclosed. The transmitter employs a local oscillator in the modulation circuit that operates at only a single frequency band characteristic. At the output of the modulation circuit, one of two transmission paths is selected by an RF switch. In the normal transmission path, the input signal is output in the normal frequency band. Alternatively, in the talk-around transmission path, the input signal is modulated to the talk-around frequency band and then output. The present circuitry eliminates the requirement for local oscillators having dual operational characteristics.

Abstract: The present invention is a digital FM voice paging system which uses digital signal processing (including D/A conversion and data compression) to transmit voice pager data over existing FM broadcast subcarriers.

Abstract: A wireless telephone equipment is provided with a microphone for receiving voice of a user and changing the voice to audio signals of an outgoing call, a cellular transmitter for modulating a carrier with the audio signals in a cellular communication, a cellular band-pass filter for filtering the carrier modulated in the cellular transmitter, a cordless transmitter for modulating a carrier with the audio signals in a cordless communication, a cordless band-pass filter for filtering the carrier modulated in the cordless transmitter, an antenna for transmitting the carrier filtered in the cellular or cordless band-pass filter and receiving a modulated signal, a band-pass filter for filtering the modulated signal, a cellular-cordless receiver for demodulating the modulated signal filtered to reproduce audio signals of an incoming call in the cellular communication and cordless communication, and a speaker for receiving the audio signals of the incoming call and giving voice.

Abstract: The invention provides a FM modulation system using a quadrature modulator, wherein a circuit for exclusive use in FM modulation and a change-over means can be dispensed with. In this system, modulating signals are inputted to a baseband signal processing circuit, converted into digital signals after integration, and turned into an analog signal by reading out a sine wave signal pre-stored in a sin ROM, thereby generating a baseband signal I for an equi-phase signal and a baseband signal Q for a quadrature signal. By adding together results of multiplication of the baseband signal I for the equi-phase signal and the baseband signal Q for the quadrature signal by a local signal of cosine and a sine wave signal obtained by phase shifting the local signal through 90 degrees, respectively, a quadrature modulation signal containing a FM modulated signal and the maximum frequency deviation can be generated.

Abstract: An increase in usable carrier frequency signals within a frequency band is achieved by identifying each carrier frequency signal or channel, not only by its base or reference frequency, but also by a rate of change of the carrier frequencies, such that for each carrier frequency assignment, an additional number of transmission channels, each having a different linear rate of change of frequency starting simultaneously from the reference carrier frequency, is provided where the instantaneous carrier frequency of these channels changes continuously over the frequency band, but each with a different incremental rate of change. Reception comes from tuning a receiver to the reference carrier frequency which adjusts automatically to the frequency reached at that time by a selected carrier frequency signal and then changing the tuning circuit at the same rate as the selected carrier frequency signal changes frequency starting from the predetermined base or reference frequency.

Abstract: A phase deviation can be prevented at the time of processing carried out when a multi-carrier signal is transmitted. A multi-carrier signal is filtered in a filter (103), and thereafter subjected to fast Fourier transform to produce symbol sequence data. The amplitude and phase of a signal obtained as the symbol sequence data are corrected. As its amplitude-phase correction circuit (211), a correction value storing portion for storing a value to cancel a change amount of the signal caused by an amplitude characteristic and a phase characteristic of the filtering in its pass band, and a multiplier for multiplying an output value of the fast Fourier transform by a value stored in the correction value storing portion are provided.

Abstract: A double mode modulator, particularly, for a portable telephone, which is adapted to realize both digital and analog modulations and have a low phase noise and a reduced locking time with a device readily integrated in an integrated circuit, including: a frequency synthesizer for synthesizing a particular frequency from an external reference clock signal; a digital modulator for performing a quadrature modulation for an output signal of the frequency synthesizer; and an analog modulator for performing a frequency modulation for the output signal of the frequency synthesizer.

Abstract: A wireless speaker system that transmits and receives both analog and digital audio signals simultaneously over a single channel at frequencies above 900 MHz. The present invention advantageously uses continuously variable slope delta (CVSD) modulation to perform analog-to-digital (A/D) and digital-to-analog (D/A) conversion of audio signals in the transmitter and receiver, respectively, using complementary filters and CVSD modulation circuits in both the transmitter and receiver. Analog signals are modulated in the transmitter with a high-frequency carrier and band-pass filtered before being combined with the digitized audio signal to modulate a high-frequency carrier, i.e. over 900 MHz, which is transmitted to the receiver. Similarly, the receiver band-pass filters and demodulates the received signal to recover the analog signal components.

Abstract: The present invention includes a system and method for ensuring reception of a communications signal. A modulating baseband signal with desired information is accepted, and a plurality of redundant spectrums is generated. Each redundant spectrum comprises the necessary amplitude, phase, and frequency information to substantially reconstruct the modulating baseband signal. It is expected but not required that the redundant spectrums will be generated at a first location and sent to a second location over a communications medium. At the second location, the redundant spectrums are independently processed to recover a demodulating baseband signal for each of the redundant spectrums. In one embodiment, an error detection process is employed at the second location to detect and eliminate those demodulated baseband signals that have been corrupted during transmission. An error-free demodulated baseband signal is selected from the remaining demodulated baseband signals.

Abstract: A scanning and targeting system (100) interconnects a plurality of radio channel units (203) in a single trunk group with a plurality of antennas (202), each radio channel unit (203) having a receive section and a transmit section and the scanning and targeting system dynamically connecting the receive section of each one of the radio channel units with any one of the plurality of antennas which, on average during a sampling period, has the strongest received signal strength of RF signals at the operating frequency of the radio channel unit, and the scanning and targeting system dynamically interconnecting the transmit section of each of the plurality of radio channel units with any one of the plurality of antennas which, on average during the sampling period, is best suited for transmitting RF signals at the operating frequency of the radio channel unit in a direction corresponding to the desired destination for the transmitted RF signals.

Abstract: In a radio communication system (100), enhanced communication capability is provided while maintaining standard channel modulation compatibility. At a transmitter (110, 200, 600), a first information signal is generated from data according to a predefined standard modulation scheme (212, 613). A second information signal is generated from data that provides supplemental information to the standard modulated data (213, 616). For transmission, the first and second information signals are combined into a composite signal (214, 619) that represents the first information signal when interpreted according to the predefined standard modulation scheme.

Abstract: Distortion or noise in detected signals, due to intermodular distortion in transmitting sets which transmit multiple channels simultaneously via the same element or component, is reduced by selecting carrier frequencies such that they are not all spaced by the same given frequency. In one embodiment, a first group of channels have one spacing, and an adjacent group have the same spacing but with carrier frequencies offset from a multiple of the spacing used in the first group. In another embodiment, the carrier frequencies of adjacent channels are unequally spaced. Two adjacent blocks of channels may use the same, or different, patterns of unequal spacing.

Abstract: In a single-chip multistandard video modulator arrangement in which audio signals for transmission with video signals are first modulated onto a subcarrier and then combined with the video signals for modulation onto a VHF or UHF main carrier, the modulated subcarrier signals are passed through a high-pass filter before being combined with the video signals in order to reduce the amplitude of any audio frequency components, and the resulting variations in main carrier amplitude, which tend to produce "sound in vision" effects.

Abstract: The present invention relates to a process and a device for the wireless transmission of a signal S.sub.1 between a transmitter and at least one receiver.According to the invention, at the sending end:a first carrier S.sub.2, of frequency F.sub.2, situated in the VHF (Very High Frequency) range, is frequency-modulated by the signal S.sub.1 to be transmitted, and thena second carrier S.sub.3 of frequency F.sub.3, situated in the SHF (Super High Frequency) frequency range, is amplitude-modulated by a modulating signal S.sub.2m. resulting from the frequency modulation of the carrier S.sub.2 so as to transmit an amplitude-modulated signal S.sub.3m to the receiver,and at the receiving end:amplitude demodulation of the signal S.sub.3m is performed so as to recover the signal S.sub.2m, and thenfrequency demodulation of the signal S.sub.2m is performed so as to recover the signal S.sub.1.

Abstract: An AM multiplexing broadcast apparatus multiplexes a digital modulated signal independent of an AM modulated signal, in the same frequency band as the AM modulated signal. A sum signal is amplified by a first amplifier. An inverse of the sum signal is obtained by an inverse calculator. A divider divides this inverse signal by a magnification factor of the first amplifier. An output of the divider and a digital modulated signal in the same frequency band as an AM modulated signal are multiplied by a first multiplier. A carrier generated by a carrier generator is phase-modulated by a phase modulator. Outputs of the phase modulator and first multiplier are synthesized and thereafter amplified by a second amplifier. Outputs of the first and second amplifiers are multiplied by a second multiplier and transmitted from an antenna.

Abstract: A frequency conversion method and a frequency conversion circuit which enlarge the frequency difference between the upper and lower sidebands of the output signal so as to enable the undesired sideband to be easily eliminated by a filter even in a case where the frequency of the input signal is low. First, a first excitation signal having a first excitation frequency (Fp) is modulated by an input signal (a) of a predetermined frequency (F1) to produce two sidebands and thereby generate a first intermediate signal (b). Next, a second excitation signal having a second excitation frequency (Fq) lower than the first excitation frequency (Fp) by exactly a frequency twice the frequency of the input signal (a) is modulated by the input signal (a) to produce two sidebands and thereby generate a second intermediate signal (c).

Abstract: A two-way communication system for communication betweeen a system network and a mobile unit. The system network includes a plurality of base transmitters and base receivers include in the network. The base transmitters are divided into zonal assignments and broadcast in simulcast using multi-carrier modulation techniques. The system network controls the base transmitters to broadcast in suimulcast during both systemwide and zone boundaries to maximize information throughout. The preferred mobile unit inlcudes a noise detector circuit to prevent unwanted transmissions. The system network further provides an adaptive registration feature for mobile units which controls the registration operation by the mobile units to maximize information throughout.

Abstract: A digital and analog modulator is configured in a simplified circuit structure. The modulator includes a first frequency mixer circuit for modulating a carrier with an analog signal or a sine wave component of a digital signal, a second frequency mixer circuit for modulating a signal attained by shifting a phase of the carrier with an analog signal or a cosine wave component of the digital signal, and an adder for adding signals from the first and second frequency mixer circuits to each other.

Abstract: The present invention teaches a paging transmitter that has an exciter that upconverts a modulated signal to an intermediate frequency (IF) above that of the transmit frequency. By so doing, the paging transmitter can broadcast a large range of transmit frequencies. Additionally, filtering of unwanted byproducts during the upconversion process is significantly simplified.

Abstract: The method for generating a modulated television signal involves performing a first filtering and a second filtering to obtain two signals, one having a passband that is equal to complete passband and the other one having a passband that is equal to the sideband to be suppressed. The signal having a complete passband is amplitude-modulated with a video carrier, obtaining a first signal. The signal having a passband equal to the sideband to be suppressed is then divided into a first component and a second component, and the first component is phase-shifting by 90.degree. with respect to the second component. The first component is modulated with a video carrier that is phase shifted by 90.degree., obtaining a second signal. The second component of the signal having a passband equal to the sideband to be suppressed is modulated with the video carrier, obtaining a third signal. The second and third signals are then subjected to an algebraic sum, obtaining a fourth signal.

Abstract: A method and apparatus for transmitting digital sound is disclosed. The method contemplates transmitting a digital radio signal (such as an FM band signal) over a plurality of sub-channels subject to some constraints on the digital signal power. A control sub-channel, sometimes referred to as an auxiliary overhead channel is used to transmit control information which is interpreted by the receiver to identify the location and potentially the mode of the digital signals.

Abstract: In a dual mode transmitter for modulating, in a digital mode, an input digital signal and transmitting a modulated digital signal and modulating, in an analog mode, an input analog signal and transmitting a modulated analog signal, a digital modulating section modulates the input digital signal to thereby generate the modulated digital signal, and outputs the modulated digital signal. An analog modulator/carrier generator modulates the input analog signal to thereby generate the modulated analog signal, and outputs it. Also, the analog modulator/carrier generator generates a carrier signal for up-converting the modulated digital signal. The up-converter up-converts, in the digital mode, the modulated digital signal by using the carrier signal and receives, in the analog mode, the modulated analog signal and passes it therethrough.

Abstract: A dual-mode frequency and phase RF modulator (11) for use in a transmitter of a radiotelephone. A dual-mode modulation approach is employed wherein, in the analog (FM) mode of operation, a phase modulator, such as a .pi./4-shift DQPSK modulator, is bypassed and may be powered down. A frequency modulated RF carrier is coupled through a bypass circuit (52) to a modulator output node (50) for transmission from the radiotelephone. In the digital mode of operation, the bypass signal path is disabled, the .pi./4-shift DQPSK modulator is enabled, and in-phase (I) and quadrature (Q) signals are input to the .pi./4-shift DQPSK modulator which provides a phase modulated RF carrier that is coupled to the modulator output node for transmission from the radiotelephone. The teaching of this invention can be employed with radiotelephones having, by example, TDMA/analog capability or CDMA/analog capability.

Abstract: An IQ modulator incorporates a quadrature network that is responsive to a frequency dependent control signal and that has in-phase and quadrature signals that are of equal amplitude and in exact quadrature over a wide range of applied frequencies. The quadrature network includes RC and CR phase shifters whose C's are fixed capacitors of equal value and whose R's are made equal to each other and to the capacitive reactance of the C's by the action of the frequency dependent control signal. The R's may be FET's. The frequency dependent control signal may be generated without express knowledge of the applied frequency by a servo loop that nulls out the amplitude difference between the in-phase and quadrature outputs from the quadrature network; it may also be generated from a look-up table as an express function of frequency. The frequency dependent control signal is split into separate instances that are applied to each R, and an offset may be introduced therebetween to provide extreme precision.

Abstract: A transmitting apparatus transmits at least one of a main and a supplementary modulated signal in response to a transmitting signal. The apparatus includes a first modulating circuit for modulating the transmitting signal in a main modulation system to produce the main modulated signal. The apparatus also includes a second modulating circuit for modulating the transmitting signal in a supplementary modulation system to produce the supplementary modulated signal. The apparatus further includes a selective supplying circuit for selectively supplying the transmitting signal to at least one of the first and second modulating systems. The apparatus also includes a control circuit connected to the first and second modulating circuits for controlling operation of the first and second modulating circuits and the selective supplying circuit.

Abstract: A radio-frequency broadcasting system and method for simultaneously broadcasting analog and digital signals in a standard AM broadcasting channel wherein the system includes: a transmitter for providing, and broadcasting, a composite signal containing an adaptively-modulated phase-shift-keyed digital signal with analog programming material modulated thereon; and a receiver for detecting the composite signal, extracting the analog audio signal and digital audio, or data, therefrom, and playing back the received audio programming. The adaptively-modulated phase-shift-keyed digital signal is responsive to the transmitted signal, dynamically increasing the digital data transmission rate as the transmitted signal power increases. Symbol states are generally arranged around concentric arcs, and adjacent symbol states are generally equidistant.

Abstract: An integrated circuit chip set is provided for use in a radio communication system in which a modulated digital input signal is processed for transmission and a modulated signal received from an antenna is processed to provide an output signal, wherein the modulation of the signals is either QPSK or FSK and the signal transmission and reception is by either TDD or FDD.

Abstract: A transmitter includes a combiner for combining plural data signal sets into a single set of data signals. An I/Q modulator modulates the single sets of data signals onto for example an intermediate frequency (IF) carrier signal. A frequency upconverter converts the frequency of the IF signal to a radio frequency signal which, when amplified in a power amplifier, is transmitted via antenna. Using the present invention, plural sets of quadrature modulated signals separated in frequency are transmitted on a single RF carrier rather than on two carriers.

Abstract: A multiple-modulation communication system includes a transmitter that modulates and transmits communication signals modulated by a first modulation technique and communication signals modulated by a second modulation technique. The first modulation technique and the second modulation technique are different. The communication system also includes a receiver capable of receiving the communication signals modulated by the first modulation technique and the communication signals modulated by the second modulation technique and demodulating the communication signals.

Abstract: A radio transmitter (103) transmits a cycle (320) including a digital portion (330) generated by frequency modulating a radio carrier with a digital signal and an analog portion (440) generated by amplitude modulating a radio carrier with an analog signal. A selective call radio (106) frequency demodulates the digital signal; amplitude demodulates the analog signal; decodes a message address (510); generates a quality signal indication (643) while a quality assessment signal (420) is being received; processes an information signal (550) in response to a message received signal (641); records at least one measurement of the quality assessment signal (420) during the quality signal indication (643); determines a signal quality level of the information signal (550) from the at least one measurement of the quality assessment signal (420); and generates a sensible alert in response to the signal quality level.

Abstract: Device and process for the generation of amplitude-modulated radiofrequency excitation pulses. A first unit (2) delivers a radiofrequency signal of constant level and a second unit (3) delivers a modulation signal of the radiofrequency signal, formed from numerical data. At least two analog multipliers (6) are connected in cascade as to the radiofrequency signal (RF) from the first unit (2) and are supplied in parallel by the modulation signal (SM) from the second unit (3). For n multipliers (6) in cascade, with n.gtoreq.2, the modulation signal (SM) delivered to the n multipliers (6) is of the A.sup.1/n.f(t) type, A.f(t) being the desired resulting modulation signal (SMR). The second unit (3) is a memory (4) containing point by point the envelope of the modulation signal A.sup.1/n.f(t) and a digital/analog converter (5) whose output is connected to the inputs in parallel of the n analog multipliers (6) in cascade.

Abstract: For each of a plurality of modulation techniques, corresponding data reception history information is stored. A particular modulation technique is selected from amongst the plurality of modulation techniques (52). At least one block of data is transmitted using the particular modulation technique (55). A message is received that provides information regarding reception of the at least one block of data, including whether reception of each of the at least one block of data occurred without error (56). The data reception history information is updated for the particular modulation technique using the information regarding reception (57). The data reception history information is used to determine an estimate of transmission signal quality (51).

Abstract: In a radio telephone apparatus of the TDMA/TDD system, signal transmission and reception are conducted by use of carriers having an identical frequency. This leads to a problem that the transmission intermediate frequency carrier and the transmission RF carrier enter the receiver section in an identical housing, thereby causing a cochanncl interference. To overcome this difficulty, there is disposed a frequency division modulator including a frequency divider for dividing by four a local signal having a frequency which is four times that of the intermediate frequency to obtain a carrier having a frequency shifted from that of the local signal by 90.degree.. Signal to be modulated is subjected to an orthogonal modulation according to the carrier wave to produce an intermediate frequency carrier. The operation of the modulator is stopped in a signal reception state to prevent the intermediate frequency carrier undergone the orthogonal modulation from being produced.

Abstract: A system (10) for transferring digital data from one data bank to another. The system (10) is designed especially for transmitting audio/video signals in digital format from a central processing center (16) to a plurality of cable networks for viewing either instantaneously or in the future. The system (10) incorporates four processing units: a central processing unit (16), a transmission processing unit (18), a receiving processing unit (20), and a master processing unit (22). The central processing unit (16) includes a scripter computer (24) for receiving a video signal (26), converting it to a digital signal (30), and storing the digital signal (30). The transmission processing unit (18) includes a transmission computer (34) and associated transmission hardware (36). The transmission computer (34) will attach a checksum to the end of each packet of information to be sent, along with any other identifying and scheduling information related to that particular file.

Abstract: A multi-carrier radio transmission apparatus provided with an idling detection means for detecting when all of a plurality of modulators are idling and a selective automatic level control means for selectively driving only specific modulators among a plurality of modulators so as to cause them send out their modulated outputs when receiving an idling detection signal from the idling detection means and for enabling an automatic level control unit to perform an automatic level control operation only when receiving an idling detection signal, whereby it is possible to realize a power detector which can exhibit an effect equivalent to that of a diode with a wide dynamic range even when use is made of a diode with a narrow dynamic range.

Abstract: An I/Q-modulator or I/Q demodulator circuit in which the modulating signals (2, 3) are input through the output phase transfer branches of the circuit. In relation to the RF-characteristics, a series resistor (16) and a series inductance (20) in the phase transfer circuits are grounded with small capacitors (23, 25). A capacitor (17) having a high impedance at the modulating frequency is located between the branches. Tho modulating signals are not summed through the capacitor (17), and, thus, their phase difference is not weakened.

Abstract: The present invention provides a system and method in which an arbitrary information-modulated signal is efficiently amplified to high power levels. The arbitrary information-modulated signal is received at a low power level and is separated into elemental signals. In a preferred embodiment, a frequency/phase information signal and an amplitude information signal are the elemental signals which collectively represent the essential information in the original information-modulated signal. The circuit uses the elemental signals to provide an amplified replica of the original information-modulated signal. The amplification preferably, though not necessarily, involves using the digital amplitude modulators disclosed in U.S. Pat. No. 4,804,931, U.S. Pat. No. 5,260,674, or U.S. Pat. No. 5,367,272.

Abstract: A system for combining AM and FM transmissions. In-band, On-channel, FM Digital Audio Broadcast (IBOC FM-DAB) allows simultaneous transmission of DAB and FM over existing FM allocations without interfering with conventional analog FM signals. The utility of existing FM spectrum allocations is therefore enhanced.

Abstract: A wide-band microwave modulator arrangement for an information transmission system, such as a video signal distribution system, in which signals from a microwave carrier signal source are split and directed over a first path comprising an attenuator and a second path comprising phase shift means and a balanced modulator, the output signals from the two paths being combined for transmission. Signals from the carrier signal source may also be directed over a third path including phase shift means and a second balanced modulator, amplified output signals from the first two paths being combined with output signals from this third path before transmission.