Compact LTCC Filter With 7th-Order Harmonics Suppression for 5g N77 Band Applications

Abstract

A compact dual-mode band-pass filter (BPF) with 7th-order harmonics suppression is proposed. The proposed dual-mode BPF is designed using a three-section stepped-impedance-variable feeding line (SIVFL) and a square resonator. The high-order harmonics suppression is achieved by the SIVFL structures, and the size reduction is achieved using meandered lines and a resonator with two degenerate modes. The proposed BPF has a wide stopband up to 7th-order harmonics and a compact size of only 7 × 7 × 0.3 mm. The proposed BPF is suitable for the fifth-generation (5G) N77 band applications due to its working frequency, compact size, and good performance. Comparison and discussion are implemented as well. INTRODUCTIONCurrently, owning to the high-capacity and speed of data transmission, the fifth-generation (5G) mobile communication has been on its excellent operation. The most attractive bands for 5G new radio (NR) are N77 (3.3-4.2 GHz), N78 (3.3-3.8 GHz), and N79 (4.4-5 GHz) [1,2]. Therefore, there is a shapely increasing market demand of 5G band-pass filters (BPFs), which can meet the requirements of excellent performances, small size, and comparative higher density packaging. Conventional dual-mode BPFs obtain a half size compared with single-mode ones; however, those BPFs do not show a function of harmonics suppression or a performance of wide stopband [3,4]. Modern radio frequency (RF) transceiver is a nonlinear system, and harmonics suppression and wide stopband characteristics are vital for the RF front-ends. Although low-pass filters can be added into circuits for harmonics suppression, adding extra low-pass filters will result in a huger circuit size and a higher cost of manufacture. BPFs with harmonic suppression are proposed in [5][6][7], but those BPFs have complicated structures, low level integration, and high in-band insertion loss.In this letter, a compact dual-mode BPF using stepped-impedance-variable feeding lines (SIVFLs) and a ring resonator is proposed and fabricated on a 2-layer low temperature co-fired ceramic (LTCC) substrate. The SIVFLs are used to suppress the high-order harmonics, and the ring resonator is used to excite two degenerate modes. The merits of the proposed BPF are harmonics suppression up to 7th-order and 60% size reduction. CIRCUIT DESIGNThe BPF is designed to cover 5G N77 band. The center frequency is 3.75 GHz, and the bandwidth is 0.9 GHz. The structure of the proposed dual-mode BPF is established in a 2-layer LTCC substrate, shown in Figure 1. The input/output (I/O) feeding lines with three-section SIVFLs are placed on the first layer, and the square ring resonator used to excite two degenerate modes is placed on the second

A Novel Miniaturized Capacitor Loaded Interdigital Filter

“…As a frequency selective device for separating signals from different frequencies, filters are widely used in various communication systems [1,2]. In recent years, the demand for filters in communication systems is developing towards miniaturization and low cost [3,4]. New processes and novel structures have been adopted to reduce the size of filters.…”