The SQG30-AC is a 10:1 passive low impedance probe with AC coupling and a bandwidth above 3 GHz. Its SMA output connects to oscilloscopes and other instruments with a 50 Ω input, and the probe reaches fast digital and RF test points directly on the PCB without soldered wires.
The AC coupling blocks up to 50 V DC, so no DC current flows between probe and circuit and the operating point of the device under test is left undisturbed. The response is flat within ±0.5 dB from 1 kHz to 2.6 GHz and the low-frequency cutoff is 359 Hz, so the small high-frequency content on a biased line can be viewed at full oscilloscope sensitivity.
With usable data rates up to 6 Gbps at the fundamental, the probe covers DC-biased serial lanes such as SuperSpeed USB at 5 Gbps, PCIe Gen 2, SATA III and DisplayPort up to HBR2, and reaches all the way to HDMI 2.0 TMDS lanes at 6 Gbps. ECL, PECL and LVPECL signaling is covered as well. On the RF side it reaches the 2.4 GHz band used by Wi-Fi and Bluetooth, GNSS receivers and other front-ends below 3 GHz, and supply noise, ripple and decoupling problems on power and control lines can be traced the same way. Besides oscilloscopes, the probe works with sampling oscilloscopes, network analyzers, spectrum and modulation analyzers, receivers, power meters and millivoltmeters with a 50 Ω input.
The nominal tip impedance is 500 Ω and the typical tip capacitance 0.35 pF. The return loss for the probed line is typically -26 dB to -3.7 dB from 0 to 3 GHz, and on a 50 Ω line the probe lowers the amplitude by about 0.42 dB without reshaping the waveform, so scaling the result restores the level. The transition time is below 103 ps, ringing stays within 0.14 dB at 3 GHz and the additive noise is 156 µV.
Both ground options are included. The dual spring-loaded ground needles sit 2.3 mm (0.09 in) on each side of the signal needle, 4.6 mm (0.18 in) apart, and keep the full 3 GHz bandwidth. The ground spring reaches ground points 6.5 mm (0.26 in) away with the bandwidth limited to 2 GHz, so the dual needles are the choice above that. A spare spring-loaded test needle is included, and the needle is replaceable when it wears.
Each SQG30-AC has its own serial number (SPID), and the S-parameters measured on that probe can be downloaded for simulation or de-embedding. The insulated head is 90 mm (3.5 in) long and 8.9 mm (0.35 in) wide, the probe weighs 34 g (1.2 oz) with its 1.2 m (47 in) cable, and its low center of gravity keeps it in place in a PCBite holder through long captures or in the hand for quick checks. A storage case holds the probe together with the probe holder, an SMA wrench, 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 6.0 V AC RMS at the probe tip.
