The SQG15-AC is a 10:1 passive low impedance probe with AC coupling and a bandwidth above 1.5 GHz. It connects through a BNC connector to any instrument with a 50 Ω input, or to a high impedance input through a 50 Ω feed-through termination, and measures high-speed digital and RF signals directly on the PCB without soldering.
AC coupling blocks up to 50 V DC, so the probe neither sources nor sinks current at the test point and the bias of the circuit stays where it is. The response is flat within ±0.5 dB from 1 kHz to 1.5 GHz, with a low-frequency cutoff of 377 Hz, so small high-frequency signals riding on a DC level can be viewed at full oscilloscope sensitivity.
Typical measurements include DC-biased data lanes up to 3 Gbps at the fundamental, such as PCIe Gen 1, SATA at 1.5 and 3 Gbps and HDMI TMDS up to 1080p, differential standards such as ECL, PECL and LVPECL, and RF signals up to 1.5 GHz on biased lines. On supply and control lines, the probe shows power supply noise, ripple and decoupling problems without the DC level filling the screen. Besides oscilloscopes, the probe works with sampling oscilloscopes, network analyzers, spectrum and modulation analyzers, receivers, power meters and millivoltmeters with a 50 Ω input.
A nominal tip impedance of 500 Ω and a typical tip capacitance of 0.35 pF keep the load on the line low, and the return loss for the probed line is typically -26 dB to -11 dB from 0 to 1.5 GHz. The loading mainly lowers the amplitude slightly, by 0.42 dB on a 50 Ω line, without changing the waveform, its spectral content or its phase, so the small loss can be corrected by scaling the measurement. The transition time is below 190 ps and the additive noise is 110 µV.
Two ground options are included. The dual spring-loaded ground needles sit 2.3 mm (0.09 in) from the signal needle on each side and 4.6 mm (0.18 in) apart, which matches PCB-mounted RF connectors and closely spaced test points. The ground spring reaches ground points 6.5 mm (0.26 in) from the signal needle. On the SQG15 both keep the full 1.5 GHz bandwidth. The spring-loaded fine-pitch test needle is replaceable, and a spare needle is included.
Every probe carries a serial number (SPID) linked to its own measured S-parameters, which can be downloaded for simulation or de-embedding. The insulated probe head is 90 mm (3.5 in) long and 8.9 mm (0.35 in) in diameter, and the probe weighs 34 g (1.2 oz) with its 1.2 m (47 in) cable. The low center of gravity keeps it steady in a PCBite holder through long captures, and it can also be used handheld. It ships in a storage case together with the probe holder, color coded cable holders and a tip protection cap.
The probe is rated CAT 0 under IEC 61010-031:2022 for circuits not directly connected to mains, with a maximum continuous input of 6.6 V AC RMS at the probe tip.
