A head-end for a signal distribution system with selection facility, includes a matrix (8) and a multiplexer (12) connected thereto for forming a multiplex signal. The head-end further comprises A/D converters (4-1 to Δ-N) for converting the wide-band input signals into digital signals prior to supply to the matrix. The multiplexer comprises two amplitude modulators (13, 14) for the mutual quadrature amplitude modulation of a carrier (17) by two digital signals, and a summing means (18) for adding a digital signal in the base band to the modulated signal. A signal receiver for one of the modulated signals comprises a synchronous amplitude demodulator (21) connected to a synchronized carrier source (20) and also comprises means for digital-to-analog conversion (24).

Signal distribution system

It is difficult that the impedance of the circuit part on the output side of an amplifying element at the frequency of a modulating wave is lower, and consequently, it is difficult to more effectively use the linearity of the amplifying element. The phase of a signal of the frequency of the modulating wave included in an amplified signal output from a FET is inverted by a difference frequency inverting circuit. The inverted signal of the frequency of the modulating wave and a signal of the frequency of a modulated wave included in an amplified signal output from a FET cancel each other out at the drain of the FET. At the drain end of the FET, the signal of the frequency of the modulating wave included in the amplified signal of the FET and a signal of the frequency of the modulating wave output from the FET cancel each other out.

Power amplifier, power amplifying method and radio communication apparatus

A transcoding arrangement transcodes signals sampled at a first frequency into second signals clocked at a second frequency. The first and second frequencies are selected so that their quotient is the ratio of integers. This results in recurrent blocks of samples having integer numbers of input samples and new output samples. A transcoder uses delay elements to form successively delayed samples of the input signal. Subtractors form difference signals representing the amplitude difference between successive delayed samples. Multipliers coupled to the subtractors multiply the difference signals by a running variable multiplicand to form weighted difference signals. The running variable is related to the effective position of the new sample being formed within a transcoding block of samples. The weighted difference signals are summed in an adder to form the new sample values. In a preferred embodiment of the invention, the ratio of the first and second frequencies is selected to be the ratio of an integer divided by an integer power of two (2 r ), which results in blocks of samples in which the number of new samples is 2 r , with the result that the multipliers can advantageously be of the shift-and-add type.

Transcoder for sampled television signals

ECONOMICAL HIGH-DEFINITION TELEVISION USING A MODULATED-SIGNAL COMBINATION Abstract A television (TV) system having a compatible high-definition signal receivable at conventional resolution by conventional TV receivers without auxiliary apparatus with carrier modulated high-definition luminance information being transmitted in a continuous spectrum spanning two conventional TV channels, carrier modulated quadrature amplitude modulated (QAM) high-frequency chrominance information being transmitted in one TV channel, and carrier modulated QAM low-frequency chrominance information being transmitted in another TV channel. At the transmitter, the high-definition luminance and chrominance signals are first comb filtered to reduce cross-effects between these types of information before modulation. A decoder recovers the high-definition luminance information by demodulating the transmitted signal and then selectively comb filtering the demodulated luminance information. The chrominance information is recovered from the transmitted signal by first notch filtering the transmitted high-definition signal to remove energy existing between the two sidebands of the QAM high-frequency chrominance information, and then, demodulating at the carrier frequency. The demodulating at the carrier frequency results in the QAM high- and low-frequency chrominance information forming a continuous spectrum that is then bandpass filtered. The high-definition I and Q chrominance signals are then recovered from the bandpass filtered chrominance information by a QAM demodulator. The QAM demodulation of the latter results in continuous high-definition I and Q chrominance signals. Another embodiment discloses a system having a compatible high-definition signal with carrier modulated high-definition luminance information being transmitted in a continuous spectrum spanning two TV channels including the high-frequency Q segment of the chrominance information as a single sideband component in one of the TV channels, the high-definition I chrominance segment and low-frequency Q segment is QAM coded and frequency translated to the other TV channel before being combined for transmission with the luminance and high-frequency Q segment.

Economical high-definition television using a modulated-signal combination

A low-range-converted chrominance signal is demodulated into two color difference signals. The two color difference signals are each filtered by a comb filter to eliminate undesired components. The two color difference signals, having been filtered, are modulated to obtain a carrier chrominance signal having a prescribed carrier frequency. To be suitable for digital signal processing, the low-range-converted chrominance signal is sampled at a first frequency which is an integral multiple of a low-range-converted carrier frequency of the low-range-converted chrominance signal when being demodulated. The two color difference signals are sampled at a second frequency which is an integral multiple of the prescribed carrier frequency of the carrier chrominance signal.

Method of reproducing a chrominance signal from a previously low-range-converted chrominance signal using comb filtering and sampling

Color encoding format for a color picture information record, and recording apparatus therefor, are disclosed for recording of discs for use with both (1) disc players designed to provide PAL-type outputs for driving PAL-type color television receivers, and (2) disc players designed to provide SECAM-type outputs for driving SECAM-type color television receivers. In players, up-conversion of recovered composite signal precedes comb filtering to separate luminance and chrominance components. Decoding of up-converted chrominance component, to obtain baseband color-difference signal information is followed by remodulation of a carrier pursuant to a desired output format. Comb filter arrangements of U.S. Pat. No. 3,969,757 are used when up-conversion shifts color subcarrier to a frequency in vicinity of PAL subcarrier frequency, but bearing odd integral multiple relationship to half the line frequency. Differing comb filter arrangements are employed when up-conversion shifts color subcarrier to PAL subcarrier frequency. Demodulation/remodulation arrangement involving the separate detection and remodulation use of two color-difference signals, as well as system requiring detection and remodulation use of only one color-difference signal, are disclosed.

Schiess J

Papers

Encoding and transcoding apparatus for video disc systems

Anordnung zur bildung eines farbvideosignalgemisches und zum abspielen einer farbbildinformation von einem aufzeichnungstraeger

Video disc recording systems