Abstract: In an SSB transmitter, a problem such that the central frequency of a BPF for extracting one of sideband signals from the modulated signals obtained by modulating a carrier frequency signal by an input sound signal is changed by temperatures, causing a drop in suppression ration and a deterioration in sound is solved. The microcomputer circuit 23 determines the change of the central frequency (−&Dgr;&agr;) of the BPF 5 from the compensation table related to the BPF 5 stored in the ROM 32 based on a temperature information of the BPF 5 detected by the temperature sensor 21; controls local oscillators 4a and 7a that output modulated signals and VHF band signals to the balanced modulator 3 and the mixer 6; and changes the frequency of each signal by −&Dgr;&agr; from the standard condition.

Abstract: In a communications system implementing, e.g., an in-band on channel AM (IBOC-AM) (also known as “hybrid IBOC-AM”) scheme, multiple bit streams are used to represent an audio signal to be transmitted over one or more frequency bands including, e.g., parts of an AM frequency band for radio broadcast. These bit streams contain various and/or equivalent amounts of audio information. In an illustrative embodiment, at least one of the bit streams is a core bit stream containing core audio information. The remaining bit streams are enhancement bit streams containing enhancement audio information. The core bit stream is necessary for recovering the audio signal with minimal acceptable quality. Such quality is enhanced when the core bit stream, together with one or more of the enhancement bit streams, is used to recover the audio signal. In accordance with the invention, the AM frequency band is divided into subbands.

Abstract: A process for transmitting mixed analog and digital signals. A composite signal is transmitted whose frequency spectrum is composed of a first analog spectrum representative of the amplitude of single-sideband modulation and of a second spectrum composed of multi-subcarriers. The two spectra occupy two disjoint frequency bands. The device may be used for simultaneous broadcast of the same program or its reception by analog or digital receivers.

Abstract: An SSB radio communication system and radio apparatus applicable to ultra high frequencies such as a VHF band and UHF band. In the transmitting side, a carrier wave is amplitude modulated by modulation input signals which comprise a constant amplitude, sine wave shaped reference pulse having a predetermined width and period and a sine wave shaped modulation pulse signal having an amplitude representing two- or multi-value digital values having the same width as the reference pulse signal and which are formed based on the amplitude of the reference pulse signal, and the modulated pulse signals are transmitted on a single side band, while in its receiving side the gain of received signals is automatically adjusted based on the reference pulse signal that is the value of the peak of the received signals.

Abstract: A method and system are provided for the transmission and reception of a composite radio-frequency (RF) signal including a supplemental signal, preferably representing encoded digital information, together with an analog signal which represents monophonic analog audio in the AM-band. The analog monophonic component of the composite signal may be received by conventional AM-band audio receivers. In certain embodiments, the analog signal is a single-sideband large-carrier or vestigial-sideband large-carrier signal, and the composite RF signal includes a digital signal whose spectrum is substantially confined in one inner sideband. In other embodiments, a baseband digital signal is combined with an analog monophonic audio signal and transmitted in upper inner and lower inner sidebands using nonlinear compatible quadrature amplitude modulation (NC-QAM). Additional digital signals' spectrum occupies the lower outer and upper outer sidebands.

Abstract: The present invention is a headset based on optics and more precisely fiber-optic communications for speaking into and listening via a cellular communications unit. The fiber-optic cable connects the microphone and earphone of the headpiece to the telephone. The use of optic fiber which is an electric insulator inherently avoids the conduction of radio frequency electromagnetic signal towards the head of the user's body, and therefore reduces possible harm to biological tissue in the head due to the radio frequency electromagnetic radiation.

Abstract: The invention provides an apparatus and procedure for radio transmission of information using a middle channel, a first side channel and a second side channel. The transmitted middle channel is FM-modulated by a suitable frequency. A signal symmetrically amplitude-modulated with respect to the center frequency of the middle channel is generated, and a first amplitude-modulated single side band (LSB) and a second amplitude-modulated single side band (USB) are formed from the amplitude-modulated signal. The first single side band (LSB) is modulated by the information in the first side channel to form two side bands for the first single side band, and the second single side band (USB) is modulated by the information in the second side channel to form two side bands for the second single side band. The middle channel FM signal, the modulated first single side band (SSB) and the second modulated single side band (SSB) are then combined in a combiner for simultaneous transmission of all three channels.

Abstract: Frequency synthesizers of a radio transceiver are automatically tuned so that its transmit and receive frequencies correspond to whichever upper band and lower band filters the radio transceiver has been connected by the user. A capacitive electrical impedance interface is coupled to filter circuitry of an upper band filter section, while an inductive electrical impedance interface is coupled to filter circuitry of the lower based filter section. A voltage reference circuit is coupled to one of the transmit port and the receive port of the transceiver. A controller is operative to automatically tune the transceiver to transmit in one of the upper and lower frequency bands, and to receive on the other frequency band, in accordance with the voltage level generated by the voltage reference circuit.

Abstract: A technique for amplitude modulating a carrier without producing side-bands is disclosed. In a preferred embodiment, a signal carrier is directly modulated and no energy side-bands are produced. This is accomplished by amplitude quantizing the data or information to be transmitted at the carrier rate or frequency and then resetting the amplitude of the carrier during one of the two 0-crossing times for each cycle of the carrier.

Abstract: A multichannel television access control system is disclosed wherein processing of the broadband signal is performed by gated coherent RF injection on a plurality of channels, thereby effecting selective descrambling of an arbitrary subset of channels in a channel group. The system provides for a closed loop injection signal phasor control so as to maintain substantially constant relationship between the television signals and the injected signals. The combined signals are supplied to subscribers enabling the use of their cable ready equipment.

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: A processing system (150) that generates a voice output signal having high precision controlled gain from a voice input signal by generating (225) a slow gain signal from the voice message by controlling a signal level gain of the voice signal using a setup gain and a first slow time constant, and then generating (230) a high precision controlled gain voice signal from the slow gain signal by controlling a signal level gain of the slow gain signal using at least one of a fast attack time constant and a slow release time constant.

Abstract: A method and system are provided for the transmission and reception of a composite radio-frequency (RF) signal including a supplemental signal, preferably representing encoded digital information, together with an analog signal which represents monophonic analog audio in the AM-band. The analog monophonic component of the composite signal may be received by conventional AM-band audio receivers. In certain embodiments, the analog signal is a single-sideband large-carrier or vestigial-sideband large-carrier signal, and the composite RF signal includes a digital signal whose spectrum is substantially confined in one inner sideband. In other embodiments, a baseband digital signal is combined with an analog monophonic audio signal and transmitted in upper inner and lower inner sidebands using nonlinear compatible quadrature amplitude modulation (NC-QAM). Additional digital signals' spectrum occupies the lower outer and upper outer sidebands.

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 method of and apparatus for effecting single sideband modulation which mixes and sums the quadrature and in-phase components of a baseband signal with the in-phase and quadrature components of an intermediate frequency (IF) signal to form in-phase and quadrature components of a sum signal having a frequency equal to the sum of the frequencies of the baseband and intermediate frequency signals and which mixes and sums the quadrature and in-phase components of an RF carrier signal with the in-phase and quadrature components of the sum signal to form a single-sideband signal.

Abstract: A modulation and demodulation scheme for video signals may be used for HDTV signals using VSB-PAM, analog NTSC signals using VSB-AM and digital video signals using QAM. VSB-PAM modulation and demodulation may be performed using in-phase and quadrature baseband filters. By adjusting the filter taps, a single modulator structure may be used for QAM and VSB-PAM modulation. Similarly, a single demodulator structure may be used for QAM and VSB-PAM demodulation. This demodulator may also be used for VSB-AM modulation.

Abstract: A modulating reflector circuit arrangement comprising a transistor configured by means of a feedback arrangement upon operation within a linear region of the transistor's current/voltage characteristic to reflect an incoming amplitude modulated signal with an increased amplitude and a modulator operable to modulate power to the transistor with a periodic waveform in which the reciprocal of the period of the periodic waveform is the required sideband frequency of the reflected signal and the waveform is selected such that the arrangement reflects a substantially single sideband 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 single sideband modulator circuit for modulating an optical signal with an RF signal to provide a frequency shift to the optical signal. The modulator circuit utilizes a dual path modulator having an electrical terminal and two optical terminals. An RF signal is provided to the electrical terminal and an optical signal is provided to each optical terminal so that the optical signal input to one terminal travels in the direction of the RF signal to produce an output optical signal having a carrier band and a single sideband, and the optical signal input to the other optical terminal travels in the opposite direction of the RF signal to produce an output having only a carrier band. A coupler adds the resulting optical output signals so that the carrier bands are cancelled, leaving only the sideband.

Abstract: A common transceiver circuit for use as either a modulator or demodulator and that is implemented through a shared resource approach. This approach is particularly, though not exclusively, suited for vestigial sideband (VSB) signals. Specifically, a VSB transceiver circuit (700), through strategically located multiplexing stages, physically re-uses a complex vestigial Nyquist filter (610), a complex mixer (620) and an equalizer (785) during demodulation and modulation. The VSB transceiver also selects a particular configuration of a common complex Hilbert transform circuit (720) for use during either demodulation or modulation. In addition, the same equalizer selectively provides both channel equalization, during de-modulation, and (sin x)/x compensation, during modulation, through use of differing corresponding sets of tap coefficients.

Abstract: A Single-Sideband (SSB) modulator includes:a demultiplexer for successively distributing an A/D converted digital signal x(t) to L sequences x.sub.1 (t.sub.1), x.sub.2 (t.sub.2)... ...x.sub.L (t.sub.L) in accordance with a sampling period t, an adder including L/2 adders for adding constants to x.sub.i (t.sub.i) of the demultiplexer, where i is either an even or an odd number; a phase shift network system comprising L/2 phase shift networks for making a 90-degree phase difference between the outputs of the adder and x.sub.i (t.sub.i) of the demultiplexer; a timing signal generator for generating timing signals expressed by A(-1).sup.(KL)/2+n and/or A(-1).sup.((K-1)L)/2+n in accordance with the sampling period t; a multiplier including L/2 pair of multipliers for multiplying the outputs of the phase shift network system by the outputs of the timing signal generator; a multiplexer for selecting the outputs of the multiplier in accordance with the sampling period t.

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 digital single sideband modulator (10) includes a relatively complex CMOS NCO (14) that drives a relatively simple ECL frequency translator (30). The frequency translator (30) outputs a digital signal that is converted to analog by a D/A (44) and then filtered in a bandpass filter (46) having a pass band including a frequency of twice the NCO's clock frequency. The NCO (14) generates a modulated intermediate frequency NCO signal having quadrature components. The frequency translator (30) multiplies real and imaginary components of the NCO signal by real and imaginary components of digitized SIN, COS sampling functions (48, 50). The resulting products are added together. The adding operation is performed by a multiplexer (32), whose selection input is driven at twice the carrier frequency, and the multiplying operations are performed by a selective negation circuit (34), that is driven at the carrier frequency.

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: An improved modulator circuit for mixing a modulation signal with a carrier signal includes first and second harmonic mixers which are operative to produce modulated output signals at an output frequency corresponding to both the sum and the difference of the modulation signal frequency and the even harmonic frequencies of the carrier signal frequency. In one configuration employing a 90.degree. hybrid, the output signals of the harmonic mixers are combined to produce a single sideband modulated output signal. A novel harmonic mixer circuit is also provided along with demodulator circuits and methods of modulating and demodulating modulation signals.

Abstract: A digital circuit having a first section for converting a low-frequency signal into a sampled single sideband signal, coupled to a second section for separating the sampled SSB signal into its two components, the phase and envelope components.

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: 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 single sideband radio system. The system comprises a transmitter and a receiver. The transmitter comprises a transmitter baseband processing portion for generating a first baseband signal comprising first, second, and pilot components and modulating the first baseband signal in inverse proportion to the strength of the first component of the first baseband signal and an RF output stage for generating and transmitting a single sideband signal comprising first, second, and pilot portions corresponding to the first, second, and pilot components of the modulated first baseband signal. The receiver comprises an RF input stage for receiving the single sideband signal and a receiver baseband processing portion for generating a second baseband signal comprising first, second, and third components corresponding to the first, second, and third portions of the single sideband signal and for correcting the second baseband signal based on the pilot component of the second baseband signal.

Abstract: A push-pull modulator stage 70 has two possible transmission paths, an electrically short path (7) and a phase delay path (6) with a phase delay element providing a phase shift of approximately 180.degree.. The phase delay element has the form of a low pass filter. In each of the two paths (6, 7) a semiconductor diode (D.sub.1, D.sub.2) is disposed in such a way that they sense the carrier (U.sub.c) with a phase shift of 180.degree. and, correspondingly, switch in unison if no modulation voltage (U.sub.m) is present, thus suppressing the carrier at the signal output (3). When a modulation signal (U.sub.m) is present, the push-pull balance is disturbed and the resistance of one of the two paths (6) becomes lower relative to the other path (7), which leads to the generation of the modulated carrier voltage (Umc). The modulator stage (70) can also be designed as a dual modulator stage and/or can be used as a mixer stage.

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: An S-Band video transmitter includes a modulator, an up converter for converting the modulated signals to a preselected S-band, and transmit circuitry for transmit circuitry for transmitting the RF signals. The S-band frequency is selected by a synthesizer including a digital phase locked loop in accordance with an input frequency selection signals.

Abstract: A balanced modulation circuit includes first, second, and third differential amplifiers. The first differential amplifier includes first and second transistors (Q11, Q12) having the emitters connected to first and second constant-current sources (CS11, CS12) and also connected with each other through a resistor, the collectors connected to the power supply line through respective base-collector-coupled transistors (Q13, Q14) used as diodes, and the bases connected to a first voltage source (V11) through respective resistors (R11, R12).

Abstract: A single sideband modulator provides a means of translating low frequency baseband signals directly to radio frequency in a single stage. Such modulators, providing suppressed carrier and one or two of the sidebands, facilitates the transmission of intelligence with significantly increased gain over AM transmission. Control signals are continuously generated to keep the local oscillator breakthrough and image sidebands down to an insignificantly low level. This is achieved by monitoring amplitude of the RF output of the single sideband modulator, and comparing this with the baseband signals. By adjusting the d.c. offsets at the baseband inputs to the balanced modulators, carrier breakthrough is cancelled. By adjusting the relative phases of the baseband signals, deviations from the 90.degree. split are compensated. By changing the amplitude of one of the baseband signals, the level of one of the RF paths is adjusted to achieve amplitude balance.

Abstract: An upper and lower side-band generator comprised of a combination of combinational logic circuits. In a preferred embodiment the invention utilizes a substantially square wave sync output associated with carrier and modulator signal generators. A lower side-band signal is generated by synchronizing the transitions of a modulator signal with the transitions of a carrier signal, mixing the synchronized signal with the carrier signal, and filtering the resulting mixed signal. An upper side band signal is generated by synchronizing the carrier and modulator signals, delaying the resulting synchronized signal, and mixing the delayed, synchronized signal and the carrier signal.

Abstract: A modulator suitable for 16 quadrature amplitude modulation (QAM) is designed as a double modulator (1), wherein a 16 QAM modulator (39) consists of two double modulators (1). One double modulator (1) has two partial modulators (1',1") forming a bridge. Each partial modulator (1',1") has two possible transmission paths: (6',6") with a phase delay line (39',39") which causes a 180.degree. phase shift. On each of the two paths (6',6", 7',7"), a semiconductor diode (D.sub.1 ',D.sub.1 ",D.sub.2 ',D.sub.2 ") is disposed in such a way that they provide the carrier (U.sub.c) with a 180.degree. phase inversion and are accordingly rendered conductive in unison, if no modulation voltage (U.sub.m) is applied, whereby the carrier is suppressed at the signal output (3'). When a modulation signal (U.sub.m) is applied, the balance is changed to push-pull, and one of the two paths (6',6") assumes less impedance compared to the other path (7',7"), which leads to the generation of the modulated carrier voltage (U.sub.mc).

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: Phase or frequency modulators which utilize phase generators rather than se shifters to produce low frequency input voltages to single side band modulators. Two phase generators are used to supply the two low frequency input ports of a single side band modulator of the 90.degree. phase shift/side band cancellation type, with the voltage dividers of one phase generator being adjusted so that its output is displaced 90.degree. in phase from the output of the other phase generator.

Abstract: 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 f.sub.s in respective first interpolators (30, 32). The interpolated signals are frequency up-converted to an output SSB carrier frequency Nf.sub.s by applying said signals to respective second interpolators (38, 40) in which the signals are sampled at 4Nf.sub.s. The samples at the outputs of the second interpolators (38, 40) are applied to a multiplexer (42) which provides a digitized version of the SSB signal which is converted to an analogue signal and filtered.

Abstract: This invention relates to apparatus for marking a recorded signal. The apparatus includes means for generating and storing a marking signal comprising at least two codes which are mutually in phase quadrature. The codes are converted to analogue signal and are used to phase-shift modulate the signal to be recorded, the modulating means performing the function of a single side band modulator on the signal to be recorded.

Abstract: The SSB modulator according to the present invention is comprised of a driving voltage generator, a diode, a bias supply circuit, an impedance transformation circuit and an input/output terminal. The SSB modulator is arranged such that the impedance of the diode is changed by changing the driving voltage impressed across the diode, resulting in the mismatching of the impedance, which leads to generation of a reflected wave. Therefore, by changing the amplitude and the phase of the above-obtained reflected wave, SSB modulation is effected. Accordingly, the SSB modulator of the present invention, requiring no particular side band filter, is compact in size, light in weight and low in manufacturing cost, with a simple structure of the circuit.

Abstract: To regulate a single sideband up converter having a pair of mixer stages (M1, M2), each mixer stage receives control signals to compensate for spurious signals of the mixer components. Part of the radio frequency output signal (RF') from the converter is fed to a down converter (M3). From the resulting down-converted signal, the original intermediate frequency signal (IF) as well as the first harmonic thereof are filtered out as a measure of oscillator and sideband suppression. From these filtered-out signals, control signals for the mixer stages (M1, M2) are obtained.

Abstract: An SSB pulse modulator which attenuates unwanted even harmonics of the carrier frequency without expensive filtering. The modulator comprises two pairs of comparators (12, 14 and 16, 18), and the sine and cosine components of the carrier signal are modulating signal [a(t)] and the Hilbert transform [a(t)] thereof are applied to respective ones of the comparators. EX-OR gates (20, 22) multiply together the outputs of each pair of comparators (12, 14 and (16, 18), the multiplied outputs being combined with each other in a signal combining arrangement (24). Each pair of the comparators produces the unwanted even harmonics, which are then attenuated by subtraction from each other in the combining arrangement.

Abstract: An active polyphase filter arrangement in which asymmetric poles and zeros are obtained using feedback. In implementing the active polyphase filter arrangement there is provided a feedforward path comprising a first polyphase filter and a feedback path comprising a second polyphase filter. Both filters are preferably two phase filters. In operating the polyphase filter arrangement the loop gain at the unwanted "image" frequency can either be made much greater than unity thereby making the feed forward path insensitive to mismatching or be made much less than unity thereby making the feedback path insensitive to mismatching.

Abstract: Several forms of a novel amplitude-modulated (AM) signal format are disclosed. Circuits of several types for generating the desired special vestigial-sideband (SVSB) AM waveforms are discussed. The principal form of the SVSB modulation provides for a reduction in transmitted signal bandwidth compared with standard double-sideband techniques plus very linear amplitude characteristics with simple synchronous detectors. Circuits according to the invention may also include means for dynamically varying signal bandwidth to accommodate special applications.

Abstract: A broadcast transmitter with single-sideband modulation for transmitting a message with a band width and carrier power which is lower in comparison with double-sideband modulation. To be able to operate a high-power single-sideband transmitter with only one transmitting tube, a single-sideband modulator (1) is used which generates, as a function on a modulating LF signal (2), a zero-phase modulator amplitude signal (9) which amplitude-modulates the anode (23) of an RF output stage tube (26) via a digital/analog converter (21), constructed as a switching amplifier with pulse step modulation, and an RF filter (22). The single-sideband modulator (1) also supplies a modulator phase signal (19) which is preferably not amplitude-dependent and which is fed to the control grid of the RF output stage tube (26), if necessary via a frequency converter (25).

Abstract: A superheterodyne receiver using the "Third Method" is equipped for reception of color-television programs. The oscillator frequency for the first mixer is located exactly in the middle between the picture carrier and the chrominance subcarrier, so that the picture carrier and the chrominance subcarrier coincide at the intermediate frequency. The Nyquist slope for the picture carrier is made steeper, so that one loss-pass filter slope determines the Nyquist slope for the picture carrier and the chrominance subcarrier and the adjacent-channel selectivity on both sides in the RF spectrum.

Abstract: A single-sideband generator comprising a 90-degree phase shifter to which a modulating signal is applied, a modulator, and a switching circuit for alternately switching the delayed and nondelayed modulating signals to the modulator at a rate corresponding to the frequency of a carrier. A frequency divider is provided for halving the frequency of the carrier and applying its output to the modulator to cause it to modulate the divider output with the output of the switching circuit. In a preferred embodiment, the modulator comprises a balanced modulator.

Abstract: A polar loop transmitter in which a negative feedback bias adjusting system is provided to control the bias voltage applied to a differential amplifier which supplies the input envelope information to an amplitude modulator, so that the R.F. modulated output goes to zero for a zero in the input envelope information.The negative feedback bias adjusting system comprises a threshold circuit for deriving a threshold voltage from the D.C. component in the output of the differential amplifier. This enables negative going spikes to be separated from the output waveform and their amplitude used to control the D.C. correction component which is applied to an input of the differential amplifier.

Abstract: A system for transmitting television signals on a radio link. The system includes a transmitter having a modulator for modulating a carrier signal to produce a vestigial sideband amplitude modulated signal for transmission. The modulator includes a first converter for converting the frequency of video signals to an intermediate frequency and a second converter for converting the intermediate frequency of the video signals to a radio frequency. The system further includes a receiver having a demodulator for demodulating a received vestigial sideband amplitude modulated signal. The modulator includes a Nyquist filter connected between the first and second converters, and the demodulator includes a filter having a rectangular characteristic for processing the signal to be demodulated.