Abstract: A television ghost signal cancellation system is provided in which the video intermediate frequency signal is demodulated by two synchronous detectors. A picture carrier extractor produces a first reference signal for the first of the synchronous detectors exhibiting a phase which is aligned with that of the picture carrier of the direct television signal. The first reference signal is shifted in phase by a controllable phase shifter to develop a second reference signal for the second synchronous detector. The output of the second synchronous detector is delayed by an amount of time equal to the difference in time between the appearance of the direct signal and a detected ghost signal. The amplitude and polarity of the delayed signal are adjusted by a control circuit to produce a pseudo-ghost signal. An amplitude comparator compares the amplitude of the pseudo-ghost signal with that of the output signal of the first synchronous detector.

Abstract: A television ghost detector system is provided which receives a training signal component of the video signal followed by a signal interval which may contain a ghost of the training signal. The training signal activates the production of a varying search signal, which in turn initiates the production of a sequence of identification pulses. The identification pulses are compared with the video signal interval following the training signal, and a coincidence signal is produced when a ghost appears in time coincidence with an identification pulse. The coincidence signal causes the value of the varying search signal to be stored as an indication of the delay of the ghost with respect to the training signal. During subsequent training signal intervals, an identification pulse is produced only when the search signal attains the previously stored value, and the identification pulse is phase compared with the ghost to update the stored value to a more precise value.

Abstract: A ghost detection and cancellation system is provided in which the horizontal sync pulses of a first sequence of lines in the vertical retrace interval are used as training signals for the detection and verification of the presence of a ghost signal. This detection procedure results in the development of a signal which reliably indicates the time location of the ghost signal with respect to the main television signal. The location indication signal is then used to select the appropriate tap of a tapped delay line. The delayed video signal from the tapped delay line is then applied to the control amplifier of a ghost canceller for the generation of a pseudo-ghost signal during a subsequent line or lines of the vertical retrace interval. The pseudo-ghost signal is combined with the original video signal to cancel its ghost signal component.

Abstract: A television ghost signal cancellation system is provided which compensates for the phase of the ghost carrier signal. A video signal containing a ghost signal component is applied to a variable delay line, which delays the video signal by an amount of time equal to the difference in time between the appearance of the direct video signal and its corresponding ghost signal components. The delayed video signal is modulated by a carrier signal and demodulated by a phase-shifted version of the carrier signal. The carrier signal is phase-shifted for the demodulator by an amount which compensates for the phase difference between the picture carriers of the direct and ghost signals. The demodulated signal is inverted and its amplitude adjusted to produce a pseudo-ghost signal which is substantially equal in amplitude but opposite in polarity to the ghost signal components.

Abstract: A television horizontal deflection system and a switched-mode power supply are provided which share a single sawtooth waveform generator for the generation of delayed deflection signals and delayed power supply gating signals, respectively. The sawtooth waveform generator has an input coupled to receive pulses which are maintained in phase and frequency synchronism with the sync pulses of the video signal. The sawtooth waveform is applied to a comparator in the horizontal deflection system where it is compared with a D.C. voltage resulting from the phase comparison of the sync and flyback pulses to determine the time of delayed generation of the succeeding horizontal deflection signals. The sawtooth waveform is also applied to a comparator in the power supply to determine the time of delayed generation of the succeeding gating signals for the SCR or like device. By selecting a time constant for the phase adjustment between sync and flyback in the deflection system which is smaller (i.e.

Abstract: A signal separation network is provided which accomplishes the functions of a sound take-off network and intercarrier sound trap in a single network. A common detector produces detected composite video and intercarrier sound signals. Circuitry is provided for processing the composite video signal, and a separate circuit is provided for processing sound information. The signal separation network has an input responsive to the detected composite video and intercarrier sound signals, a first output terminal coupled to the input of the video processing circuitry, and a second output terminal coupled to the input of the sound processing circuitry. The network is characterized by a transfer function which exhibits a dominant zero approximately at the intercarrier sound frequency at the first output terminal, which provides trapping of the intercarrier sound signal in the path to the video processing circuitry.

Abstract: A pulse generator is provided which may be advantageously used to produce a deflection drive signal in a television receiver. A capacitor is initially charged to a reference voltage level. Prior to the time at which the output pulse is to be generated, the capacitor is charged from a current source for a known time duration at a first rate. At the end of the charging interval, the capacitor has accumulated a known increment of charge proportional to the charge interval, and a new voltage level is established across the capacitor. The generator is now prepared to produce an output pulse. At a subsequent time, when the output pulse is needed, the capacitor is discharged at a second rate by a second current source. During the time interval that the second current source is discharging the capacitor, an output pulse is produced by the generator.

Abstract: A method of tuning a trap circuit to a desired frequency is provided. A constant amplitude signal is applied to the trap circuit in a progression of successively different frequency increments. The frequency increments cover a frequency range including the desired frequency. The amplitude of the signal, as modified by the trap circuit is detected and stored at each of the different frequency increments. Successive ones of the stored amplitude values are compared until an amplitude difference is found which is greater than a predetermined minimum difference and is of a polarity indicative of an increase in amplitude with the progression, and is a successor of an amplitude difference which is greater than the predetermined minimum difference and of a polarity indicative of a decrease in amplitude with the progression. The frequency at which the inflection point occurs, as indicated by the two-named amplitude differences, represents the null frequency of the trap circuit.

Abstract: A preamplifier is provided which couples a television tuner to a surface acoustic wave (SAW) filter and amplifies the I.F. signals supplied by the tuner so as to overcome the signal losses of the SAW filter. The preamplifier comprises a single transistor, the gain of which may be varied to provide desired gain and noise performance for the entire tuner-SAW filter-I.F. system. The gain of the preamplifier is simply adjusted by changing the values of one or two resistive components. The preamplifier includes a negative feedback path, which stabilizes the preamplifier against temperature variations, presents desired impedances to the tuner and SAW filter, and permits the substitution of a different transistor without the need for extensive readjustment. Means are provided for simply adjusting the biasing of the transistors without adversely affecting any previous gain adjustments.

Abstract: Apparatus is provided for suppressing radio frequency interference radiation at a circuit connection point. The apparatus includes a capacitor having first and second terminals, the first of which is coupled to a substantially planar plate of the capacitor. The first terminal is coupled to the circuit connection point, which may otherwise act as an RFI antenna. The second capacitor terminal is coupled to a point of reference potential for radio frequencies. The capacitor is oriented when mounted so that the planar plate opposes and is substantially parallel to a metallic surface which is at the radio frequency reference potential (e.g., ground). The capacitor suppresses RFI radiation from the circuit connection point by conducting a portion of the RFI energy at that point to the point of RFI reference potential by way of the first terminal, the body of the capacitor, and the second terminal.

Abstract: A differential amplifier is provided, including first and second emitter coupled transistors responsive to an input signal applied to one of their base electrodes, and a current source transistor having its collector-to-emitter path serially coupled between the coupled emitters of the first and second transistors and a point of reference potential. A current repeater circuit is coupled between the collector electrodes of the first and second transistors which comprises a current mirror for replicating the collector current of the first transistor. The current mirror includes third and fourth transistors having respective collector electrodes coupled to the collector electrodes of the first and second transistors, respectively, the base electrode of the third transistor being coupled to the base electrode of the fourth transistor, and a resistor for coupling the emitter electrode of at least one of the third and fourth transistors to a source of supply voltage.

Abstract: A comb filter apparatus is provided with means for equalizing the delayed and undelayed signal levels at the inputs to the adding or subtracting matrix, whereby maximum cancellation and reinforcement of the undesired and desired signals is effected. An input signal is coupled to an additive or subtractive matrix by way of an undelayed signal path and a delayed signal path. The delayed and undelayed signals at the inputs to the matrix are each coupled to a detector by way of a bandpass filter, which pass frequencies at which the combing of the signal is most critical. The detectors detect the levels of the input signals and apply the detected levels as two inputs to a difference circuit. The two signal levels are compared in the difference circuit to develop a gain control signal. The gain control signal is utilized to control the gain of a gain controllable stage which is coupled in series with one of the signal paths thereby equalizing the levels of the input signals to the combining matrix.

Abstract: A selectivity network is provided for a synchronous detector, a reference signal circuit, and an AFT circuit. The selectivity network comprises a first tuned circuit coupled across two terminals of the reference signal circuit and tuned to the desired frequency of the I.F. picture carrier. A second tuned circuit is lightly coupled to the first tuned circuit and is coupled across two inputs of the AFT circuit to provide a frequency dependent phase-sifted reference signal to the AFT circuit. The first tuned circuit includes a trap circuit tuned to provide attenuation about a frequency intermediate the frequency of a sound carrier and that picture signal sideband frequency which, upon detection, results in a video signal corresponding to the intercarrier sound second subharmonic frequency. The trap in the reference signal tuned circuit minimizes quadrature distortion in the reference channel and the resultant harmonic distortion in the video signals, which causes sound buzz.

Abstract: A network is provided for attenuating the adjacent channel sound carrier signal in a television receiver. First and second trap circuits are serially coupled intermediate the R.F. mixer and the first I.F. amplifier. One of the trap circuits is tuned to a frequency in the vicinity of and above the nominal frequency of the adjacent channel sound carrier, and the other is tuned to a frequency in the vicinity of and below that of the adjacent channel sound carrier. The two trap circuits are mutually coupled to a degree necessary to produce a composite response curve exhibiting a substantially constant level of maximum attenuation in the vicinity of the nominal frequency location of the adjacent channel sound carrier. The trap circuits provide attenuation in excess of that required to eliminate adjacent channel sound carrier interference over a bandwidth sufficient to encompass expected carrier deviation due to frequency modulation, carrier mislocation, and trap mistuning.

Abstract: A gating circuit coupled to the phase detector of an AFPC loop prevents response of the phase detector to alternate sync pulses during the equalizing and vertical sync pulse interval.

Abstract: A peak detector circuit is provided for detecting the maximum excursions of an amplitude varying signal. The circuit includes a network comprising a capacitor serially coupled to a charging impedance and having a time constant suitable for responding to the maximum excursions of the amplitude varying signal. A semiconductor means has an input terminal for receiving the amplitude varying signal and an output terminal coupled to the charging impedance for charging the capacitor toward the maximum excursions of the amplitude varying signal. The semiconductor means exhibits an impedance which is subject to increase with a decrease in current drawn therethrough.

Abstract: A differential sample-and-hold circuit includes first and second emitter-coupled transistors the bases of which are coupled to the signal source to be sampled. A gated circuit source coupled to the joined emitters supplies operating current in the sampling mode and supplies no current in the holding mode. First and second rectifiers each serially coupled with a resistor are coupled between a reference voltage and the collectors of the first and second transistors, respectively. A hold capacitor is coupled between the collectors of the transistors.