Circularly-polarized planar antenna with a shaped pattern for airborne applications, is proposed in this letter. The proposed antenna consists of vertically-polarized formation and horizontally-polarized stubs to provide circularly-polarized configuration, which is loaded by a copper curl based top layer to control current distribution for beam shaping and filling of zenith null. The antenna also contains split ring resonators beside partial ground to make it deployable over larger ground planes (metallic bodies) without distorting circular polarization by controlling phase of reflected waves. The power density of presented airborne shaped pattern antenna differs for variant elevation and azimuth angles, to have uniform wireless coverage over the earth's surface by managing variations of the signal strength because of different path lengths. The demonstrated antenna also possesses circular polarization and direction based circular polarization diversity at angles against the greatest path-lengths. Antenna retains a null-filled pattern in the vertical plane along with having high absolute peak gain (5.5 ± 1 dBi) and adequate peak polarization gain (2 to 4 dBi) throughout the operational bandwidth from 2.82 GHz to 2.89 GHz (Measured reflection coefficient less than −10 dB). Moreover, the radiating element exhibits omnidirectional radiation characteristics, with good horizontal gain (greater than −3.6 dBi).
0.3 mm is mounted in the metal cavity. The frequency tripler assembly step mainly includes a DC bias circuit substrate and quartz substrate adhering and sintering, jumping gold line between the DC bias circuit and the quartz substrate, and Schottky diode chip adhering and baking. As shown below, the photo of 220 GHz tripler is shown in the Figure 7.Input power is provided by Agilent E8257D PSG Analog Signal Generator, a monolithic microwave integrated circuit (MMIC) amplifier and high-power doubler, in the frequency band 70$80 GHz. The power is up to 120 mW. The 220 GHz output signal is measured by VDI Erickson PM4 millimeter/submillimeter wave power meter.When the input power is 20 mW, 60 mW, 90 mW, and 120 mW, respectively, the tripler is tested with self-biased. The tested conversion loss results are shown in Figure 8. When the input power is greater than 60 mW, the frequency tripler working condition is stable, and the conversion losses of the three cases (60 mW, 90 mW, and 120 mW) are almost identical. The typical conversion loss in the frequency band 216$232 GHz is 15 dB. The 20 mW input power is too low to drive the tripler.The conversion loss with different bias is shown in Figure 9. The results show that the conversion loss is below 15 dB in the band 216$232 GHz with the lowest loss 13 dB.In order to obtain high output power, larger power is input to drive the multiplier. The maximum output power of 70$80 GHz source is only about 140 mW. Figure 10 is the output power test results. The maximum output power is 6.34 mW and the output power is greater than 5 mW in the frequency range 220$228 GHz. The corresponding conversion loss is shown in Figure 11. There is no significant difference compared with the earlier test, so the tripler is not saturated, and therefore it will get a higher output power with a higher power input source. CONCLUSIONA 220 GHz tripler is designed in this article, which is composed of input and output standard copper waveguide split in the Eplane, 50 microns quartz circuits as suspended microstrip and a GaAs Schottky varactor diode chip. A precise 3D electromagnetic (EM) planar Schottky barrier diode (SBD) model is established and the field-circuit co-simulation method is employed for the design of the 220 GHz tripler. The measured results show that the maximum output power is about 6.34 mW, and the lowest frequency conversion loss is 13 dB, and the output power is greater than 5 mW in the frequency range 220$228 GHz. The improvement of diode model and mechanical manufacturing process will help to improve the performance of the tripler. The designed frequency multipliers in this article can be used as terahertz signal source.ABSTRACT: In this article, a compact dielectric resonator antenna array was proposed for microwave imaging systems. Four resonator elements of Roger RT/Duroid 6010 were used over the FR4 substrate for an array configuration with a total size of 35 3 50 3 7 mm. The proposed antenna array attained wide operational bandwidth of 6 GHz ranging from 12 to 18 GHz making a...
In this paper, a modified ground structure capable of reducing mutual coupling to provide isolation between adjacent antenna elements is presented. The proposed modified ground structure is a combination of a strategically located ground slot, asymmetric partial ground and a substrate-integrated pin wall. The use of the modified ground structure causes a more than 28 dB (measured value) mutual coupling reduction. The modified ground structure has been optimized and validated with a finite spaced planar 2 × 1 antenna array operating at 4.16 GHz, intended for unmanned aerial vehicle radar altimeter applications. The patch antennas built with the MGS exhibit high gain (greater than 6 dBi throughout the operational band), along with inter-element coupling as low as −65 dB. Mutual coupling reduction at lower contours is beneficial for altimeter applications.
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