In this letter, a wideband substrate integrated waveguide (SIW) based slot antenna is designed for D -band applications. A wideband response is attributed to the merging of closely lying six resonance frequencies. Two of them at frequencies of 114.25 GHz and 134.75 GHz signifies the excitation of TE $_{310}$ and TE $_{120}$ modes, respectively. The modes at 124 GHz and 144 GHz are identified as hybrid modes that are formed from the combination of TE $_{310}$ –TE $_{120}$ and TE $_{120}$ –TE $_{220}$ modes, respectively. The upper two resonances at the frequencies of 154 GHz and 160 GHz occur due to TE $_{220}$ –TE $_{320}$ based hybrid modes. A two-step wideband WR6-SIW transition is also designed and integrated with the antenna for measurement purpose. In the first step, the three-section Chebyshev transition is developed to match the impedance of standard WR6 with a rectangular waveguide (RWG) of the same height as that of the PCB. In the second step, the RWG is matched with SIW using a dielectric extension. The final antenna with transition is simulated and measured. A wide $-$ 10 dB impedance bandwidth for $|S_{11}| \leq -$ 10 dB of 42.86% (110–170 GHz) is obtained. The gain and radiation measurements were also performed after constructing an in-house measurement system.

In this letter, a tilted-D-shaped monopole antenna with wide dual-band dual-sense circular polarization is proposed. The tilted-D-shaped radiator is designed by combining inverted-C-shaped (ICS) and tilted-I-shaped (TIS) structures. The proposed radiator is attached to a 50-Ω line through an impedance transformer. The proposed design is compared with two of its variants, which concludes that the wide 3 dB axial ratio bandwidth (ARBW) in both bands is achieved due to the contributions from the ICS and TIS structures. Besides, the lower and upper bands radiate left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP), respectively. A prototype of the proposed antenna is fabricated, and its performance is experimentally verified. The measurement results show that the proposed antenna exhibits a wide impedance bandwidth for |S11|< -10 dB of 104.54% (3.47-1.07 GHz) entirely covering both CP bands with 3 dB ARBWs of 31.16% (4.28-5.86 GHz) in the lower and 22.62% (7.49-9.4 GHz) in the upper band. In broadside direction, the measured gain varies between (1.26-3.58 dBic) and (3.85-6 dBic) in the lower and upper bands, respectively.

In this paper, a triple-band dual-sense circularly polarized (CP) hybrid dielectric resonator antenna is proposed. A modified hexagonal dielectric resonator (DR) is top-loaded with a square microstrip ring (SMR). A vertical-tapered-strip connected to a 50- $\Omega$ microstrip line is used to excite the proposed antenna. It is found that the lower and central CP bands correspond to left-handed circular polarization and are produced by the TM ${}_{11}$ and TE ${}_{111}$ modes of the SMR and modified hexagonal DR, respectively. The upper CP band is formed by the combination of the quasi-TM ${}_{21}$ mode of the SMR and quasi-TE ${}_{111}$ mode of the DR that exhibits right-handed circular polarization. The measurement results of the fabricated prototype show triple-band response for |S ${}_{11}|<$ −10 dB with impedance bandwidths (IBWs) of 17.4% (1.75–2.03 GHz), 28.13% (2.23–2.96 GHz), and 2.97% (3.65–3.76 GHz) in the lower, central, and upper bands, respectively. The measured 3 dB axial ratio bandwidths lying within −10 dB IBWs are 3.69% (1.86–1.93 GHz), 5.46% (2.67–2.82 GHz), and 2.15% (3.68–3.76 GHz) along with the peak gains of 5 dBic, 5.28 dBic, and 2.36 dBic in the lower, central, and upper bands, respectively.

In this paper, a new dual-band circularly polarized (CP) dielectric resonator antenna for WLAN and WiMAX applications is proposed. The dielectric resonator has an asymmetric Y-shaped geometry. By properly selecting the length of the arms, the pairs of fundamental (TE ${}_{111}$ ) and second-order (TE ${}_{211}$ ) are excited separately at the design frequencies to radiate the CP wave. The measurement shows that the fabricated antenna exhibits a wide impedance bandwidth for |S ${}_{11}|<$ −10 dB of 62.07% (2.2–4.18 GHz). The far-field measurements in the broadside direction demonstrated a dual-band CP response with 3 dB ARBWs of 4.92%(2.38–2.5 GHz) at the lower and 12.64% (3.26–3.70 GHz) at the upper band. The measured CP bands cover the entire frequency range of WLAN (2.401–2.495 GHz) and WiMAX (3.4–3.69 GHz) at the lower and upper bands, respectively.

In this paper, an electronically-controlled frequency-agile hybrid dielectric resonator antenna is presented that also produces a reconfigurable circularly polarized (CP) wave over a specific frequency range. Two L-shaped metallic strips are placed adjacent to a partial ground plane that can be shorted/detached in four combinations using two PIN diodes (D1 and D2). Frequency reconfigurability is achieved by switching from both OFF to at least one ON state to yield a single and dual-band responses for the former and latter, respectively. The Eigen mode simulation reveals that the upper-band is mainly attributed to the quasi-TEδ21 mode of the rectangular dielectric resonator. The lower-band in one and two ON-states arises due to the dielectric-loaded monopole antenna and the strip-loaded partial ground plane, respectively. The ON-OFF state produces a right-handed CP wave at the lower band that can be reconfigured to a left-handed CP wave by switching to OFF-ON state. A fabricated sample is measured and simulation results are validated. The measured – 10 dB impedance bandwidths for OFF-OFF, ON-ON, OFF-ON, and ON-OFF are 13.31% (4.42–5.05 GHz), 11.30% (2.17–2.43 GHz)/27.43% (3.68–4.85 GHz), 30.64% (2.46–3.35 GHz)/17.94% (4.16–4.98 GHz), and 26.57% (2.48–3.24 GHz)/18.7% (4.12–4.97 GHz), respectively. The measured 3 dB axial ratio bandwidths are 12.20% (2.54–2.87 GHz) and 10.95% (2.59–2.89 GHz) when D1 and D2 are turned-ON alternatively.

We report 280 GHz 8:1 and 16:1 frequency multipliers in 250-nm indium phosphide (InP) HBT technology. The 8:1 multiplier uses three cascaded push-push emitter-coupled-pairs serving as balanced frequency doublers, with 1:1 transformers at 35, 70, and 140 GHz providing single-ended to differential conversion; the 16:1 multiplier has an additional input emitter-coupled push-push doubler whose drive signal is generated by a transistor differential input stage. With $-\text{2}$ dBm input power, the 8:1 multiplier generates $-\text{0.6}$ dBm output power at 280 and has 48-GHz $\text{3}$ -dB bandwidth. Spurious harmonics are suppressed by ${>} 28$ dBc over the $\text{3}$ -dB bandwidth. With $-\text{13}$ dBm input power, the 16:1 multiplier generates $-\text{0.6}$ dBm output power at 280 and has 44-GHz $\text{3}$ -dB bandwidth. Spurious harmonics are suppressed by ${>} 26$ dBc over the $\text{3}$ -dB bandwidth. The 8:1 and 16:1 multipliers consume 102-and 162-mW dc power and occupy 0.4-and 0.75-mm ² die area, respectively. To the authors’ knowledge, these results demonstrate record spectral purity for frequency multiplier chains operating near 280 GHz.