Electrically Tunable Substrate Integrated Waveguide Equalizer With Stable Insertion Loss in High Frequency

Abstract

In this letter, a novel design for an electrically tunable substrate integrated waveguide (SIW) equalizer that maintains a stable insertion loss at high frequencies, is proposed. The SIW equalizer is composed of various parallel units consisting of microwave resistor (R) and varactor diode (C). Different resistance and capacitance values, forming a complex impedance, are achieved through PIN and varactor diodes under different DC biases, respectively. It results in greater losses in the low-frequency range compared to the high-frequency range, achieving an equalization effect. Moreover, because ideal capacitors do not contribute to signal loss, the loss in the high-frequency range remains minimal and stable under certain conditions. Experimental results indicate that the equalization range in the Ku-band is 0.30–9.75 dB with a DC voltage range of 0–4 V, and the insertion loss change in the high-frequency band is only 0.5 dB. For the equalizer operating in the Ka-band, within a DC voltage range of 6–14 V, the equalization range is 0.30–16.60 dB, with a change in insertion loss of only 0.12 dB at high frequencies. The return losses of equalizers are all better than −12.4 dB and −11.6 dB, respectively, in Ku- and Ka-band.