Implement DTV receivers with cost-effective demodulator

The market for DTV is growing fast, and system developers continue the search for more cost-effective ways to implement DTV receivers without sacrificing picture quality. TI's TVP9900 ATSC demodulator offers a high-performance receiver front-end solution with multipath performance, helping DTV manufacturers reduce components costs while maintaining the high-quality images that are expected from digital transmission. Designed for flexible implementation, the standalone demodulator is based on field-proven technology that TI has used successfully in other DTV products.

Extensive support is also available to help system developers evaluate DTV concepts and develop circuitry and software quickly. Among the most useful tools is the TVP9900 evaluation module (EVM), which provides a ready-to-use ATSC front-end receiver, complete with an Alps tuner daughter card. The WinVCC (Windows' Video Control Center) software included with the EVM provides a comprehensive user interface for initialization, optimization, status and visualization. The EVM hardware and WinVCC software work together to simplify TVP9900 development, and help speed time-to-market for new DTV products. The TVP9900 ATSC demodulator supports the reception of DTV broadcasts, including HDTV, in North America. The device supports all standard ATSC over-the-air and cable transmissions. The standalone demodulator is compatible with standard ATSC tuners and a wide range of DTV video processors from TI and other suppliers. The figure shows the major components and connections of a DTV receiver using the TVP9900.

TVP9900 performance meets or exceeds the ATSC's A/74 recommendations, helping to simplify receiver design while ensuring high-quality imaging. Signal equalization covers the echo profile required by A/74 guidelines. Multipath and burst noise impairment performance demodulates all Brazil ensembles for improved signal reception over a greater transmission range.

With a high level of system integration, the demodulator saves DTV manufacturers up to 20 percent BOM for the receiver. With a 14mm x 14mm footprint and the removal of external circuitry, the device saves considerable board space (up to 300mm) over alternative demodulation solutions.

Troubleshooting
The TVP9900 EVM is intended to help designers evaluate the TVP9900 demodulator and test design concepts quickly. Its PCB provides circuitry along with test points and jumpers to operate the TVP9900 and dynamically troubleshoot the chip's functions within a receiver system. The WinVCC software included with the EVM provides one-click settings for 8-VSM and 64/256 QAM demodulation.

At the front-end, the EVM's main module interfaces to a daughter card with an Alps TDQU4X005A tuner and RF input. A common interface enables easy communication to other tuner boards. MPEG-2 data is output to the developer's selected DTV processor through a port with both parallel and serial settings. The demodulator is controlled by and reports to the WinVCC software through a PC host port that emulates the I?C bus. A 25MHz crystal is provided on board for the device clock, or a 4MHz input from the tuner can be selected as the clock source. Tuner control can be set as either direct from the TVP9900 demodulator or through the emulated I?C bus.

The EVM also provides layout guidance for the developer's own circuitry with complete schematics in the documentation. Additional TVP9900-based reference designs are also available.

The TVP9900 ATSC demodulator supports the reception of DTV broadcasts, and all standard ATSC over-the-air and cable transmissions.

Enhancing evaluation
Included with the TVP9900 EVM is WinVCC software for control and troubleshooting of the DTV receiver front-end. The tasks that WinVCC performs to enhance demodulator evaluation include:

• System initialization via command files with different register data sets;

• Download of firmware to the device;

• Optimization of register settings using property sheets that can be edited and saved;

• Status reporting via registers;

• Real-time status plotting for visualization.

For ease-of-use, all WinVCC functions are controlled by a main Windows taskbar that calls up windows for specific tasks, including interactive windows for editing settings. Among these tasks are system initialization, ATSC tuner control, TVP9900 property sheets, I?C register map editor, virtual oscilloscope and eye diagram/constellation plot.

Configuration and control of the TVP9900 itself is provided via property sheets. The interactive sheets allow evaluation of an entire range of parameter values by moving a slider and offering the other features. Similar register editor sheets are provided. They enable the user to show and edit the current state of all bit fields in the I?C register space. Values from the property sheets can be saved as initialization data sets and inserted in system software to save time in program modification.

The WinVCC software also offers visualization tools that can be selected from the property sheets. These tools include the virtual oscilloscope, which provides real-time plots of up to four status registers. The tool stores all acquired data from time 0 and provides the option of saving data for offline analysis. Features that aid in signal analysis include:

• Real, magnitude, phase or Doppler plot types;

• Variable time and division;

• Variable Y offset and scale;

• Automatic Y scale;

• Zoom and horizontal pan.

Visualization is also offered by the eye diagram and constellation plotting tool. The tool displays signal variation at the carrier recovery slicer input with persistent plots and allows the user to save data to a log file.

- Marc Pyne
Digital Video Applications Engineer
Texas Instruments Inc.