Release of a New IC Capable of Achieving Greater Compactness for the Digital CATV Set Top Box

~ A Japan-First Development Integrating all Functions Required for Frequency Conversion to the Base Band in a Single Chip ~

[µPC2798GR]

This new IC product converts the intermediate frequency (IF) signal output from the tuner of a digital CATV STB or cable modem to the base band frequency in the region of 10MHz, that is, the frequency suitable for handling the signals. The principal features of the IC product include the following:

• As the various functions, including the AGC amplifier (Note 2) maintaining the intermediate input frequency (IF) signal at a constant level, the mixer converting the IF signal frequency to the base band frequency, and the video amplifier amplifying the base band signal have been integrated in a single chip, this Japan-first achievement has made it possible to reduce the number of parts required for products such as the STB significantly, thereby achieving greater compactness;
• Thanks to its built-in amplifier, the IC product is capable of directly driving the analog/digital (A/D) converter required for demodulating the QAM signals;

• Due to the use of aluminum wires instead of the conventional metal wires generally employed in high-frequency ICs, is has also been possible to achieve lower cost.

The digital CATV market is expected to show a rapid rate of growth. In connection with the use of CATV cable networks for PC data transmission, dramatic progress is also being made in achieving a cable modem capable of transmitting and receiving motion picture signals at a transmission speed in excess of 30Mbps. This advance is a major step forward to usher in high-speed, high-capacity digital cable data communication. The IC component of the receiver configuration meets the exacting requirements for low distortion, low price, and compact packaging as the precondition for high-density mounting.

To meet these demands, the new product is manufactured by a special NEC silicon high-frequency process known as NESAT-II. (NESAT stands for NEC Silicon Advanced Technology.)

Features of the new product are as follows:

(1) Harnessing all functions required for converting the IF signals to the base-band frequency band in a single channel

Thanks to the use of the high-frequency process based on original NEC technology and to a special circuit design, it has been possible to integrate the conventional, mainly discrete products and the universal blocks normally consisting of 4 or 5 IC arrays into a single channel, thereby reducing the number of parts to about a fifth.

(2) The A/D Converter Required for QAM Signal Demodulation Can be Directly Driven

Thanks to the built-in video amplifier, it is possible to drive the A/D converter directly, thereby facilitating the design of the interface circuit.

(3) Use of a 20 Pin SSOP Package

The ability to achieve a high surface mounting density offers major benefits in terms of the compactness of the set.

(4) Operation Using a Single 5V Power Source

The power supply circuit for the set marks an evolution toward greater simplification.

NEC is confident that the new product will contribute to achieving higher standards of compactness and performance for digital CATV STBs and cable modems in anticipation of the rapid expansion these fast-growing products are expected to show in the near future and of the widening application scope of these products. In response to these needs and to the existing market potential, positive efforts are being made to promote and expand sales of the new products.

See the attatchment for main specifications of the new product.

Note 1: QAM (Quadrature Amplitude Modulation)

QAM stands for Quadrature Amplitude Modulation. This is one technology for transmitting digital signal at high efficiency with the use of signal multiplexing. With 64 QAM, for example, it is possible to achieve 6 bit (26 x 64) data transmission at a single time.

IF (Intermediate Frequency)
IF stands for Intermediate Frequency. For CATV reception, the incoming signals from the broadcasting station in the frequency range of 50 - 75MHz are first converted (in Japan) to a constant frequency of 58.75MHz. This is known as the intermediate frequency.

Down Converter
This is a certain type of frequency converter consisting of a circuit that steps the high input frequency down to a low output frequency. Down converters are used in digital CATV receivers for converting the incoming QAM-modulated transmitted high frequency signals to the low frequency that can be handled by the demodulating IC.

Note 2: AGC(Automatic Gain Control)

AGC stands for Automatic Gain Control which is used to obtain signals of a constant output level regardless of the input signal level.