A compact filtering phase shifter is proposed using two quarter-wavelength coupled lines, two quarter-wavelength transmission lines, and two face-to-face feed lines. With such a circuit model, the proposed design has the advantage of compact size and simple structure compared with the state-of-the-art designs. Multiple transmission zeros (TZs) can be obtained. Constant passband for different phase shifts can be achieved by controlling the parameters of coupled lines and transmission lines. Theoretical analysis based on the even-/odd-mode method guides the design. Two prototypes with the phase shifts of 45° and 90° are designed for verifying the theoretical analysis. It is shown that the 45° (90°) phase shifter can obtain 45° ± 2.3° (90° ± 4.3°) for the 3-dB bandwidth of 51% (51%), the phase shift bandwidth of 57% (58%), and the size of $0.5\lambda _{\mathrm {g}} \times 0.01\lambda _{\mathrm {g}}$ ( $0.7\lambda _{\mathrm {g}} \times 0.01\lambda _{\mathrm {g}}$ ), where $\lambda _{\mathrm {g}}$ is the guided wavelength at the center frequency.

In this paper, a balanced phase shifter using coupled line with loaded transmission line is proposed, which is the first balanced passive phase shifter providing both differential-mode (DM) phase shift and common-mode (CM) suppression simultaneously. Furthermore, the proposed design can provide (30° ~ 90°) phase-shift range with characteristic of wide bandwidth. Compared with single-ended phase shifters, the proposed design can be directly utilized in differential system without additional baluns. Compared with the state-of-arts balanced passive phase shifters, the proposed one shows the advantages of CM suppression, wider bandwidth, wider alternative phase-shift range and simpler structure. Three DM transmission poles can be obtained to support the wide bandwidth. Complete theoretical analysis and discussion are given to guide the design. To verify the theoretic prediction, three prototypes are designed with the operation bandwidth for 30°$\pm$2.5° (60°$\pm$4.2° and 90°$\pm$5.5°) of 68% (70% and 73%), with the minimum insertion of 0.2 dB (0.15 dB and 0.27 dB), with the CM suppression better than 10 dB, and with the minimum return loss of 17.8 dB (18.5 dB and 15.1 dB), respectively.

A differential filtering phase shifter is proposed utilizing two three-end folded coupled lines with three half-wavelength microstrip lines. Four differential-mode (DM) transmission zeros (TZs) can be obtained on both sides of the DM passband because of the cascaded two three-end folded coupled lines and one half-wavelength line. Thus, the frequency selectivity and out-of-band suppression can be enhanced. Wide CM suppression bandwidth can be obtained by the multiple common-mode (CM) TZs and the upper and lower half-wavelength lines. The phase shift bandwidth can cover the passband and the passband performance for different phase shifts can keep constant by controlling the parameters because all lines contribute to the control of phase shift deviation and 3-dB bandwidth. Compared with the reported differential filtering phase shifter, the proposed phase shifter obtains higher frequency selectivity and wider CM suppression. Complete theoretic odd- and even-mode analysis and design procedure are carried out. Two prototypes centered at 3.3 GHz are designed, which exhibit fractional bandwidth (FBW) for 45° ± 2.29° (90° ± 4°) of 42.7% (42.4%), the 3-dB FBW of 39.4% (39.4%) and the CM suppression FBW of 141% (145%).

A millimeter-wave (mm-wave) end-fire substrate integrated dielectric resonator antenna (EFSIDRA) is proposed to provide dual-beam radiation. The dual-beam radiation is caused by the multilayer rectangular dielectric resonator (DR) with metallic walls on both sides and air vias at the center, which are used to generate modified TE13δ mode and adjust the distribution of E-fields, respectively. The metallic walls, air vias, DR and feeding line can all be implemented with printed circuit board (PCB) process, which enhances the integration level of the end-fire dielectric resonator antenna. The theoretical analysis of the dual-beam radiation is provided to guide the practical design. Compared with the state-of-the-art designs, the proposed antenna not only achieves dual-beam radiation in end-fire dielectric resonator antenna, but also exhibits the capability of substrate integration and high radiation efficiency. For demonstration, a dual-beam prototype is fabricated and measured. The proposed antenna shows a dual-beam radiation with ±61° beam direction and more than 13 dB suppression at the end-fire direction.