The J2154A is a low-cost single or differential TDR in a portable package. It turns your oscilloscope into a PCB Trace, Cable, Connector, and Coupon Tester. With its 10.5GHz pulse generator and internal power splitter, the J2154A can make TDR, FRA (probe measurement), and VNA (S21) measurements. The J2154A has improved jitter (~20dB). The J2154A now comes in multiple colors. Please choose your color: silver, black, red, blue, or gold, when ordering.

The PerfectPulse signal generator provides a square ~30ps edge pulse in a pocket size, self-contained package, requiring only a USB power source. The affordable, small, simple to use, portable and lightweight unit with unique specifications for differential lines and high accuracy in detecting and locating small resolution impedance changes. The 50 Ohm output signal is very square, without overshoot or undershoot making it perfect for verifying instrument and probe rise/fall times, as well as verifying signal path rise/fall time and undershoot/overshoot. The addition of a 10GHz power splitter allows the signal generator to be used as a reflectometer for measuring PCB coupons, cable and PCB trace impedance, verifying cable crimps, measuring trace and cable lengths, dielectric constant and many other applications.

Modes of Operation and Connectivity
TDR – For single-ended and differential mode TDR measurements, Connectors 1 and 3 connect to the oscilloscope channels, while connectors 2 and 4 connect to the probes. This is the native mode and most common mode of operation. These can be either single-ended or differential measurements. Connectors 1 and 2 are used for single-ended measurements.

FRA – For the measurement of an oscilloscope probe, the voltage is measured at the tip of the probe, so that the 50O port resistance does not damp the probe response. This is equivalent to measuring with a very low source impedance, such as that presented by a power supply. Connectors 1 and 3 connect to the oscilloscope channels, while connectors 2 and 4 connect to the probes. This is the same connection as the TDR, but the math functions use Fast Fourier Transforms (FFTs) of the high-speed signal edge at the tip of the probe and a high or low impedance scope input to measure the back end of the probe to display the probe transfer function. These can be either single-ended or differential measurements.

VNA – For VNA (frequency domain) measurements the signal is measured prior to the 50O port resistance so that the output is 50O as required by S-parameters. This is accomplished by connecting the oscilloscope to connectors 2 and 4 and the probes to connectors 1 and 3. As with the FRA, the math functions use Fast Fourier Transforms (FFTs) of the high-speed signal edge at the probe side as one 50O port and a second 50O scope channel as the second port. The math function displays S21. (It is possible also to display S11, but not S22 or S21). These can be either single-ended or differential measurements.

Demo Board

The Picotest TDR Demo board includes differential and single-ended test traces with varying impedances.