Supplying power to a device in most cases requires regulation of the signal to appropriate levels. Fortunately, Quell supplies a solution that is as effective as it is cost effective.

One common need is a capacitive filter, also known as a notch filter or low-pass filter, which allows low-frequency signals to pass through while attenuating high-frequency signals. A C-Filter is commonly used to remove unwanted noise or ripple from applications such as power supplies, audio equipment, and other electronic devices where stable, noise-free power is essential. The resulting output from capacitive filters is a smoother, more stable voltage for the circuit.

Another set of problems encountered by design engineers are crosstalk, interference, and signal distortion due to parasitic capacitance. Parasitic capacitance exists between conductive elements in close proximity to each other, such as adjacent cabling.

Quell EESeal® capacitive filters can rival off-the-shelf, in-circuit filters for the level attenuation of high frequencies. A range of filter insert offerings are effective in varied DC voltages. The simple and easy-to-install EESeal solution can also be employed to attenuate parallel capacitance from 1pf to 1uf, and in voltages up to 2000 WVDC.

Typical strategies to reduce or eliminate parasitic capacitance–such as increasing distance between conductive elements, incorporating ground planes to circuit layouts, differential signaling, or trying twisted-pair cables–all involve significant design modification.

By comparison, for both parasitic capacitance and high-end ripple concerns, EESeal filter inserts are often the most cost effective and convenient course of action and can be added to completed designs where unexpected signal disturbances are discovered post hoc during testing. The thin elastomeric insert installs in seconds, by hand, with no soldering.

Power Cable Test at High Frequencies

To see the effects of a Quell filter connector insert, consider the test results on a power cable between 13 GHz and 20 GHz. The first graph and table show the baseline noise at this level.

The second graph depicts the attenuation after the addition of a 2.5 pF EESeal filter insert on the power line. All the points selected in the table have reduced ~10 dB or more and substantially at sample point 5, where we find a reduction at 16 GHz by about 21 dB.

Parallel Capacitance

As the test demonstrates, filter inserts reduce overall noise but are designed to knock out a targeted range of frequencies.

To reduce a wider range of frequencies on interconnects, engineers can use two filters of different ranges (space permitting inside the connection).

The result is an overall boosted capacitance along higher frequencies that may solve noise problems with multiple peaks. The following graph shows the attenuation results from a combination of EESeal inserts designed for 47nF and 100pF targeted capacitance.

Capacitive Filters from Quell

To tackle high frequencies, Quell has several ready-to-ship products that can fit your project depending on the desired cap value and working DC voltage. Popular solutions include Hi-Rel 0201, 0402, 0603, 0805, or 1206 SMD Capacitors. Identify the requirements you need in the table below and consult with a Quell technical advisor to find the most appropriate insert for your project needs.