Bias Tees and DC blocks are actually specific forms of very low frequency filters. Specifically, a Bias Tee is a diplexer with an extremely low crossover frequency, while a DC block is a high pass filter with a very low cutoff frequency. All Marki Microwave bias tees and DC blocks offer low, flat insertion loss up to high frequencies.
Marki offers two basic designs for surface mount bias tees. The design used only in the BT-0030SM/G, includes a bypass capacitor on the DC input line, making it immune to external disturbances on the bias line, but it also cannot be improved with additional external components. The performance of the BT-0030SM/G does not change with the current load on the DC bias line. The design used in the BT-0014SM/G, BT-0024SM/G, and BT-0034SM/G does not include an internal bypass capacitor directly on the DC blocking line. The low frequency on these bias tees is lower (500 kHz instead of 10 MHz), but is dependent on the bias conditions. It can be extended lower and made more insensitive to current with an external coil (down to 4 kHz). An external bypass capacitor can also be added to make it more immune to bias line disturbances.
All bias tees are constructed using a custom-made, resonance-free conical inductor to achieve extremely broadband performance. These bias tees offer superior performance, reliability, and ease-of-use when compared to cumbersome bias tees employing off-the-shelf conical inductors.
Marki DC blocks use a proprietary coaxial construction to offer extremely high frequency operation with low, flat insertion loss.