Cable Television Device

What is this patent about?

’866 is related to the field of wideband receivers, specifically those used in cable television (CATV) systems. Modern CATV systems need to handle a large number of channels spread across a wide frequency spectrum. Traditional tuner designs struggle to balance dynamic range and bandwidth, leading to expensive data conversion and processing requirements in the demodulator.

The underlying idea behind ’866 is to perform channel selection and filtering in the digital domain, immediately after a wideband Analog-to-Digital Converter (ADC). The digitized wideband signal, containing both desired and undesired channels, is fed into a digital frontend (DFE) . This DFE then uses digital down-converters to isolate and extract only the desired channels, effectively filtering out the unwanted ones early in the signal processing chain.

The claims of ’866 focus on a cable TV device that includes a wideband ADC and a DFE. The ADC digitizes a contiguous band of frequencies containing both desired and undesired channels. The DFE then selects and provides each of the desired channels, without providing any of the undesired channels. The claims specify that the desired channels are outputted via a serial interface .

In practice, the wideband signal is digitized, and then a bank of digital mixers, driven by numerically controlled oscillators (NCOs), shifts each desired channel down to baseband. Digital filters then remove out-of-band noise and interference. This approach reduces the data rate and dynamic range requirements for the subsequent demodulator, allowing for the use of less expensive components. The selected channels can then be outputted via a serial interface for further processing or display.

This design differs from traditional tuners by moving the channel selection and filtering from the analog to the digital domain. Prior approaches typically down-converted the entire wideband signal to an intermediate frequency (IF) and then relied on the demodulator to perform channel selection and filtering. By performing these operations in the DFE, ’866 reduces the burden on the demodulator and allows for a more efficient and cost-effective receiver architecture, particularly suitable for applications like digital video recorders (DVRs) and picture-in-picture displays.