Recommended Accessories: Cables, Splitters, Attenuators, and Inverters

Learn how to integrate accessories like cables, splitters, attenuators, and inverters to send and shape signals in your experiment.

All Time Tagger inputs are designed for SMA connection with 50 Ohm impedance. When selecting any accessory below, make sure it matches the input impedance to avoid signal reflections and distortions.

Recommended SMA Cables for Time Taggers

SMA cables are the cable of choice when connecting a Time Tagger with a device.

As a reference, to test our devices internally, we mainly use two types of cables. One type for standard usage (see under this link), and one used to achieve better signal-to-noise ratios (see under this link).

More specifically, there are many parameters to consider when selecting an SMA cable:

• Length. Ideally, the Time Tagger has to be placed close to the experimental setup, and USB extenders should be used to cover longer distances. When this solution is not possible, we would suggest keeping the length of the SMA cable below five meters. Our devices can work with longer cables, but the signal can degrade, affecting the overall jitter.

• Shielding. One should check its effectiveness, in other words, how much an external signal can be transmitted in the line. To achieve better timing jitter, the cable should be shielded as much as possible from external sources of interference, such as electromagnetic and radio frequency signals. Therefore, we would recommend a double-shielded cable instead of a single-shielded one.

• S-parameters. Return and insertion losses must be kept as low as possible to avoid signal distortions.

• Frequency range. The bandwidth supported by the cable should cover the frequency range of the signal from the detectors. Signal with frequencies out of this range can cause distortions. As a result, the time jitter would no longer reflect the specified one.

• Power vs. frequency. Depending on the frequency range, there can be differences in the transmitted power and how much of it can be handled by the cable itself.

• Temperature. There are typical ranges given by the manufacturer, especially important when working with cryo temperatures.

Power Splitters

A power splitter lets you send the same signal to two channels of the Time Tagger or two separate measurement setups simultaneously, without needing a second signal source.

Keep in mind that splitting a signal also reduces its power. A standard 2-way splitter divides the signal equally between its two outputs, so each output receives about 50% of the original power, resulting in a loss of approximately 3 dB. Make sure the resulting signal still meets your Time Tagger’s minimum amplitude requirements after the split (see the Minimum Pulse Amplitude and Duration Requirements section).

The splitter should cover the frequency range of your signal.

Example models: ZFRSC-42-S+, ZX10R-14-S+, and ZFRSC-183-S+.

We recommend not using T-connectors to split electrical signals. While practical, they can distort the signal, e.g., producing reflections.

Attenuators

If your signal’s amplitude exceeds the maximum input voltage range of your Time Tagger (see the Maximum Input Voltage Amplitude section), an attenuator can bring it within the accepted range without distorting the signal shape.

Attenuators are rated by how much they reduce a signal, in decibels (dB). For example, a 10 dB attenuator reduces the signal’s voltage amplitude to about 32% of its original value. Choose the attenuation value needed to bring your signal’s peak amplitude within your Time Tagger’s accepted input range.

The attenuator should support the required input power within your signal’s frequency range.

Example models: VAT-10A+ (10 dB) and VAT-12A+ (12 dB).

Recommended Pulse Inverters for Compatibility with Time Tagger 20

The Time Tagger 20 can accept only positive signals and requires a pulse inverter to be used with negative polarity signals. A pulse inverter is usually a simple passive component that inverts pulse polarity. Passive inverters use a type of transformer, transfer only alternating signals, and work in a specific frequency range. They may perform poorly when used outside their design frequency range, leading to signal distortion and incomplete inversion.

The table below lists various pulse inverters available in the market that have been tested or are expected to work with the Time Tagger 20.