Resonance characteristics of substrate-integrated rectangular cavity (SIRC) are systematically analyzed in this paper. Synthesis design techniques of substrate-integrated waveguide (SIW) dual-band bandpass filters (BPFs) and wide-stopband BPFs are demonstrated on the basis of these characteristics. The design concept of dual-band BPFs is to add some extra single-mode SIRC resonators to dual-mode resonator filters to increase the degrees of freedom in extracting direct-coupling coefficients, while the external quality factors $Q_{e}$ and cross-coupling coefficients desired in two passbands can be realized simultaneously by determining proper offset position of the I/O ports and cross-coupling window, respectively. Consequently, all the design parameters including $Q_{e}$ and coupling coefficients $M_{ij}$ required for both the passbands could be satisfied. The principle of wide-stopband BPFs is to select the constitutive SIRC resonators with identical fundamental frequency but staggered higher order ones to suppress multispurious peaks to low levels and narrow bandwidths. Then emphasis is placed on the rejection of TE202 mode, with its resonant frequency two times of TE101 for all SIRC resonators, by centered I/O ports and coupling windows. Several experimental prototypes of SIW dual-band BPFs and wide-stopband BPFs are designed and fabricated to validate these concepts. The measured results are in excellent agreement with the simulations.

Resonance Characteristics of Substrate-Integrated Rectangular Cavity and Their Applications to Dual-Band and Wide-Stopband Bandpass Filters Design

This communication presents a differential dual-polarized filtering dielectric resonator antenna (DRA). In this antenna, a four-leaf-clover-shaped dielectric resonator is excited with two groups of out-of-phase modes. The novel configuration and differential feeding provide the DRA with high isolation for input ports, and the elaborately designed feeding strips ensure controllable input impedances for integration applications. After integrating with a pair of filtering baluns on the opposite side of the reflecting ground, the proposed DRA also exhibits good out-of-band rejection for each port with a wide stopband and two radiation nulls at band edges. A prototype has been designed and implemented, and reasonable agreement between the measured and simulated results can be observed.

Differential Dual-Polarized Filtering Dielectric Resonator Antenna

The contribution of this letter is to propose a novel substrate integrated waveguide (SIW) dual-band balanced bandpass filter (BPF), which exhibits characteristics of compact size and improved common-mode (CM) suppression. Two diagonal resonant modes TE102 and TE302 in a square SIW resonator with symmetric field distributions provide the possibility to realize balanced inputs/outputs, dual-passband responses and the vertically stacked structure for compact size. Without affecting the differential-mode (DM) responses, a novel method of using slotlines etched on one broadside of either SIW resonators to shift the resonant frequency of CM away from the DM passband is also proposed, to realize a higher CM rejection for this BPF. Meanwhile, perturbation vias have been utilized to adjust the center frequency of the lower passband, while the higher passband can remain almost unchanged. A second-order prototype is designed for the demonstration. Good agreement between simulation and measurement has been observed in the measurement.

Compact Dual-Band Balanced SIW Bandpass Filter With Improved Common-Mode Suppression

A simple and planar design structure for dual-band bandpass filter (BPF) with multiple transmission poles and zeros is proposed in this brief. According to frequency response transformation, two passbands are realized on both sides of the operation frequency. Sharp selectivity and high isolation level with eight transmission poles and seven transmission zeros are achieved just by employing three-section coupled lines and three short-circuit stubs. Besides, the analytical (closed-form) extraction process for the transmission poles and zeros of the proposed dual-band BPF is presented based on the rigorous scattering-parameters theory and the even- and odd-mode analysis method. A prototype for the dual-band BPF with 3-dB fractional bandwidth of 41.1% and 19.0% is designed and fabricated. The measured and simulated results are in good agreement to verify the validity of the proposed design principle.

A Simple Planar Dual-Band Bandpass Filter With Multiple Transmission Poles and Zeros

In this paper, a multiple stubs loaded ring resonator (MSLRR) is proposed to design directly coupled multi-band bandpass filters (BPFs) with mixed electric and magnetic coupling (MEMC). The proposed MSLRR exhibits multiple-mode resonant behavior. The increased number of loaded stubs excite many more useful resonant modes, but these resonant modes can be still independently controlled. As examples, a dual-band BPF, a tri-band BPF, a quad-band BPF, and a quint-band BPF using different types of MSLRRs are designed and fabricated. The passband frequencies and return losses (RLs) of these multi-band BPFs can be independently controlled. A dual-mode open loop resonator is then introduced in the quint-band BPF to enhance the sixth resonant mode of the MSLRR to produce the sixth passband so that a sext-band BPF is also presented. Multiple transmission zeros due to the cancelling effect of MEMC and virtual grounds in the MSLRR can be observed around the passbands resulting in sharp passband selectivity and high band-to-band isolation. Moreover, all of the fabricated multi-band BPFs have compact sizes, good RLs, and low insertion losses. Good agreements are observed between the simulated and measured results.

Compact Multi-Band Bandpass Filters With Mixed Electric and Magnetic Coupling Using Multiple-Mode Resonator

A new method of designing a dual-band balun bandpass filter (BPF) with high selectivity is proposed and implemented by taking advantage of the existence of multiple substrate integrated waveguide (SIW) cavity modes. The major design concept applied in this letter is based on two mechanisms: one is by properly placing the output ports to achieve the balanced output for both passbands, and the other is by taking cross coupling of higher/lower order modes to achieve transmission zeros (TZs) at each side of the passband. Two internal coupling slots are involved to separately control the coupling level between cascaded cavities for each passband. A prototype operating at $9.0~{\rm GHz}$ and $9.8~{\rm GHz}$ has been realized and shows the desired filtering performance. The differences between the two outputs are within $180^{\circ}\pm 2^{\circ}$ in phase and $0.6~{\rm dB}$ in magnitude across the two passbands. Measured frequency responses agree well with the simulated ones in this work.

Dual-Band Substrate Integrated Waveguide Balun Bandpass Filter With High Selectivity

A novel stepped-impedance ring resonator (SIRR) with two pairs of shorted stubs is proposed to design a dual-band bandpass filter. The proposed resonator is a quad-mode resonator, and one resonator can realize a dual-band filter. The frequency space between two passbands and bandwidths of two passbands can be controlled by the shorted stubs. Wide out-of-band rejection can be achieved by selecting the desired impedance and length ratios and suitable feeding point to suppress some spurious resonant frequencies. A prototype filter centered at 1.395 and 1.825 GHz is designed with the first spurious response occurring at 7.84 GHz or $5.7f_{01}$ ( $f_{01}$ is the center frequency of the first passband). Good agreement between the simulated and measured results can be observed.

Dual-Band Bandpass Filter With Wide Stopband Using One Stepped-Impedance Ring Resonator With Shorted Stubs

The invention discloses a substrate integrated waveguide differential band-pass filter. The substrate integrated waveguide differential band-pass filter is formed in the way that a first double-sided microwave dielectric substrate and a second double-sided microwave dielectric substrate are adhered through a prepreg; a first resonant cavity is formed by punching a metalized through hole into the first double-sided microwave dielectric substrate; the first resonant cavity performs differential feed through two first micro-band feeders which are symmetrical about the center of the first resonant cavity; a second resonant cavity is formed by punching a metalized through hole into the second double-sided microwave dielectric substrate; the second resonant cavity performs differential feed through two second micro-band feeders which are symmetrical about the center of the second resonant cavity; the two resonant cavities are cascaded through a pair of coupled empty slots on the lower surface of the first double-sided microwave dielectric substrate and a pair of coupled empty slots on the upper surface of the second double-sided microwave dielectric substrate. One out-of-band zero point is generated on each of the two sides of a passband, so that the differential mode out-of-band inhibition performance and the common mode inhibition performance are excellent.

Substrate integrated waveguide differential band-pass filter

The invention relates to a double-passband balun filter. The double-passband balun filter comprises a substrate, wherein a first resonant cavity and a second resonant cavity are formed in the substrate, the first resonant cavity and the second resonant cavity are adjacent and align to each other partially, a first coupling structure and a second coupling structure are arranged between parts, which align to each other, of the first resonant cavity and the second resonant cavity, the first coupling structure extends along the central axis of the first resonant cavity, and the second coupling structure extends along the central axis of the second resonant cavity; and a first output feed microstrip line, a second output feed microstrip line and an input feed microstrip line, and the first and second output feed microstrip lines are symmetrical about the geometric center of the first resonant cavity. The double-passband balun filter has the benefits that requirements of the balun filter for dual-passband signals are met, and the double-passband balun filter is simple in structure and small in size.

Double-passband balun filter

The invention relates to a near-field antenna. The near-field antenna comprises a metal box body, a first dielectric substrate, a near-field coupling coil, an input end and a second dielectric substrate. The metal box body is used for shielding outside electromagnetic interference and comprises a tabulate base board and a cover body fixed to the base board, and an opening exactly facing the base board is formed in the cover body. The first dielectric substrate, the near-field coupling coil and the input end used for inputting radio-frequency signals into the near-field coupling coil are contained in the metal box body, and the first dielectric substrate is placed to be adjacent to the opening. The second dielectric substrate is fixedly arranged in the metal box body and on the base board, the second dielectric substrate, the first dielectric substrate and the base board are parallel to each other, and a metal paster array is arranged on the upper surface of the second dielectric substrate. The near-field antenna has the advantages of enhancing the magnetic field strength within a near-field range and reducing the thickness of the near-field antenna.

Chu Hui

Papers

Dual-Band Substrate Integrated Waveguide Balun Bandpass Filter With High Selectivity

Dual-Band Bandpass Filter With Wide Stopband Using One Stepped-Impedance Ring Resonator With Shorted Stubs

Substrate integrated waveguide differential band-pass filter

Double-passband balun filter

Near-field antenna