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A miniaturized lumped‐element balun is proposed for the very high frequency band applications. The miniaturization is accomplished by the inductor–capacitor (L‐C) surrounded resonator, which places a vertically interdigital‐capacitor inside spiral inductor for higher integration. The L‐C surrounded resonator only takes up one element's area without increasing the number of substrate layers. The balun is built on a 10‐layer thickness low temperature co‐fired ceramic substrate and has the smallest reported size of only 0.004 × 0.003 × 0.0003λg. Moreover, the proposed balun also has a second‐order harmonic suppression of 40 dB. Furthermore, thermal boundary analysis, comparisons, and discussions are also implemented. [ABSTRACT FROM AUTHOR]

A wideband and miniaturized bandpass filter (BPF) is proposed using size reduced resonator (SRR) for the very high frequency band applications. The proposed SRR places vertically interdigital‐capacitor inside spiral inductor, thus two L‐C elements only take up one inductor's area. Therefore, significant size reduction and integration increment are both achieved without increasing the number of substrate layers. The BPF is built on a 10‐layer thickness low temperature cofired ceramic substrate and has the smallest reported size of only 0.00 7 λg × 0.004 λg × 0.0005 λg. Moreover, the BPF also achieved a wide fractional bandwidth of 97.2%, a low in‐band insertion loss of only 0.7 dB, a great selectivity BW20 dB/BW3 dB of 1.23 and a wide stopband up to 2.2f0 with 20 dB suppression. Furthermore, comparisons and discussions are also implemented. [ABSTRACT FROM AUTHOR]

In the RF (Radio Frequency) front-end of a communication system, bandpass filters (BPFs) are used to send passband signals and reject stopband signals. Substrate-integrated waveguides (SIW) are widely used in RF filter designs due to their low loss and low cost and the flexibility of their integration properties. However, SIW filters under 6 GHz are still too large to meet the requirement of portable communication devices due to their long wavelength. In this paper, a very compact fully integrated SIW filter is proposed and designed with RT6010 dielectric material to meet the small size requirement of portable devices for next-generation sub-6 G applications. The proposed filter contains two sawtooth-shaped composite right-/left-handed (CRLH) resonator units, instead of traditional rectangular-shaped CRLH resonator units, which makes the filter more compact and cost effective. The filter is designed and fabricated on an RT6010 substrate, with a size of only 10 mm × 7.4 mm. The measurement results illustrated that the proposed BPF shows a passband covering the frequency range of 3.25–3.45 GHz; the minimum passband insertion loss is only 2.4 dB; the stopband rejection is better than −20 dB throughout the frequencies below 3.0 GHz and above 3.8 GHz; S11 is as low as −37 dB at 3.35 GHz; and the group delay variation is only 1.4 ns throughout the operation bandwidth. [ABSTRACT FROM AUTHOR]