HTS power filters for output multiplexers in satellite communications

Abstract

The paper reports on advances in the development of high temperature superconducting 40 MHz bandwidth fourpole bandpass filters with elliptic frequency response for 3.4 -4.2 GHz (extended C-band) output multiplexers of communication satellites. By employing the concept of "edgecurrent-free" disk and ring resonators the filters possess a small size but can handle 60 W transmitted power with sufficiently low insertion loss and intermodulation. Measurements of the unloaded Q-factor and power handling as function of the temperature, performed at single disk resonators made from YBa2Cu307.p on LaA103 and sapphire substrates indicate the conditions under which the required Q-factor of about 1.5.105 and sufficiently low nonlinear response up to an oscillating power of 15 kW can be obtained. Approaches for shifting the resonant frequencies of unwanted modes relative to the resonant frequency of the employed TMolo-mode are outlined and shown to be necessary for the envisaged multiplexer applications.

Progress on applications of high temperature superconducting microwave filters

“…The disc resonator filter was proposed to improve the electric power performance of HTS filters in the early years [23][24][25]. Those two-dimension resonators were designed to resonate at TM 01 or TM 11 modes.…”

HTS narrowband stripline filter at 2.1 GHz with high power handling capability

“…Several high power filters have been reported with TM-mode or dual mode for high frequency range [1][2][3][4]. TM 0n0 mode ring resonator carries only radial component of the current density, and there is current free in parallel to the edges of the disk patch.…”

Compact superconducting dual-log spiral resonator with high Q-factor and low power dependence

“…Suppressing these sources of losses in the device to a minimum, would greatly improve the and exploit the benefits of extremely low surface resistance of the YBCO conductor strip. For instance, high-quality YBCO 4-GHz disk resonators (ignoring their larger size) on a sapphire and improved LaAlO3 substrates have been reported to achieve of more than 50 000 at 77 K and sufficiently low nonlinear response up to an oscillating power of 15 kW [11]. These researchers have used the efficient concept of edge current-free disk resonators.…”

“…Equation (11) can only be applied with sufficient accuracy if the correct effective permittivity is calculated. This also is a problem due to the complexity of the log-spiral shape since is dependent on the total equivalent capacitance of the microstrip line and hence is very sensitive to its nonuniform width and spacing.…”