STEVAL-TDR021V1

The STEVAL-TDR021V1 evaluation board is part of STMicroelectronics\' RF Evaluation and Development Kits, Boards range. It is used to evaluate, easily and quickly, the performance of ST’s high-definition time domain reflectometers (TDR) and applications.

The STEVAL-TDR021V1 evaluation board is provided with a TDR module that enables the experimentation of a wide range of applications, such as loss/saturation detection, ground/short detection, open trace detection and fixed frequency recognition. To provide the best signal conditioning, the TDR module consists of three dynamic variables: trigger threshold level, acquisition time and test signal amplitude. There is also a digital character (D) output which can be used to set the TDR applications.

The board is equipped with an impedance bridge developed to measure impedance across any two microstrip lines. This impedance bridge uses a standard 20-turn adjustable inductor, which allows flexibility in design. In order to properly measure the impedance of a microstrip line, the TDR should have a driving-end impedance which is equal to the impedance of the load-end. With the impedance bridge, this can be achieved as well as allowing for bridge calibration.

The STEVAL-TDR021V1 hardware architecture is optimized for low power consumption. An output amplifier is included to provide an output signal suitable for external measurements. Maximum input power capability is 2W continuous wave (CW) for a 20-meter range. The device also includes external power ports which are used to power external equipment.

Working Principle

The STEVAL-TDR021V1 evaluation board, in its working principle, measures the time-domain reflection caused by a sudden discontinuity in a transmission line. To do this, a pulse is sent through the transmission line and the reflected signal is observed. Based on the shape of the response waveform, the distance to the reflection can be determined. This distance is usually used to determine the characteristics of the reflection, such as length, resistance, materials and other attributes. The time-domain reflectometer can measure the length of the trace as well as its impedance.

The STEVAL-TDR021V1 also features an impedance bridge, which can be used to measure the impedance of two microstrip lines. The impedance bridge is made up of an adjustable inductor, which is used to adjust the bridge\'s termination impedance. This allows for bridge calibration and allows the TDR to have a driving-end impedance equal to the impedance of the load-end.