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Half wavelength microstrip antenna loaded with a varactor a Top view b Side view l ¼ 56 mm, w ¼ 45 mm, h ¼ 1.1 mm, substrate RT Duroid, 1 r ¼ 2.2, varactor surface mount, MAH46072, C 0 ¼ 8.25 pF, F ¼ 0.82, g ¼ 0.55, equation (1)
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Analysis and experiments on microstrip antennas with varactor tuning are presented. Results are given for the frequency tuning of rectangular half and quarter wavelength microstrip antennas. Double tuning range was observed for quarter wavelength antennas. Emphasis is also given to the study of harmonic radiation generated because of the varactor n...
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Citations
The basic geometry of a microstrip patch antenna (MPA) consists of a metallic patch which is either printed on a grounded substrate or suspended above a ground plane. The antenna is usually fed either by a coaxial probe or a stripline. In the coaxial case, the center conductor is directly connected to the patch and the outer conductor to the ground. In the stripline case, energy is coupled to the patch in several ways: by direct connection, by proximity coupling, and by aperture coupling. The patch antenna idea appeared to be originated in the early 1950s, but there was little activity for almost two decades, mainly due to its inherent narrow bandwidth. It began to attract the serious attention of the antenna community in the 1970s, as antenna designers began to appreciate the advantages offered by this type of antennas, which include low profile, conformability to a shaped surface, ease of fabrication, and compatibility with integrated circuit technology. In the last three decades, extensive studies have been devoted to improving the bandwidth and other performance characteristics. This chapter begins with a brief description of the modeling techniques and basic characteristics of the MPA. Methods for broadbanding are then discussed, followed by dual- and multiband designs, size reduction techniques, circularly polarized patch antennas, and frequency-agile and polarization-agile designs. The chapter ends with some concluding remarks.
In last few decades the development of wireless technology has enabled the exciting growth in mobile telecommunications. The endless pursuit of wider bandwidth, higher frequency and better efficiency has driven the innovations of micro and millimeter wave systems and devices, where the technologies that balances both performance and feasibility prevail. Nowadays the challenge of multiband and multi-standard operation is expected to be met by the frequency-agile, software defined and cognitive radios.
A novel method based on a wideband equivalent circuit model is proposed to analyze the harmonic radiation of a tunable Planar Inverted-F Antenna (PIFA) tuned by a varactor. The nonlinear relationship between the input power, DC bias voltage and the dynamic RF voltage over the varactor are quantified for a single-band prototype. The radiation power is simulated at the first and second harmonic frequency. The verification is finally presented by measurement.
In this paper, a frequency-agile, miniaturized slot antenna suitable for use in hand-held devices is proposed. First of all, in order to design an electrically short slot, one end of the slot is terminated by a capacitance chosen according to a simple resonator model. The design concept is verified by both simulation and experiment, and is shown to be feasible. Instead of a constant capacitive termination, the frequency agility is attained by utilizing a varactor diode, of which the capacitance can be controlled by changing its bias voltage. A prototype antenna having a slot length of 20 mm and terminated by a varactor diode exhibits a continuously tunable resonant frequency between 0.78 GHz and 2.09 GHz as the bias voltage is adjusted from 0 V to 20 V.
A reconfigurable antenna with good load matching and covering a wide frequency range presents a practical design challenge when the antenna size is tightly constrained. A procedure is presented for the design of a reconfigurable mobile antenna, which overcomes the antenna size limitations. Tuning is achieved by placing a varactor diode at a specific position across a slot in the radiator conducting surface. The fabricated antenna is designed to cover a wide band, between 1700 MHz and 2040 MHz, at a return loss better than 10 dB. The radiation of harmonics generated due to the varactor nonlinearities are simulated and measured. The experimental setup insures that the low levels of radiated harmonics are reliably validated. The experimental results show a good agreement with that computed using the Friis equation.
The purpose of this work is to propose a new method to suppress the harmonic radiation from a microstrip patch antenna with proximity coupled feeding line implemented in a multilayer substrate. The goal of the design is the suppression of the resonances at the 2nd and 3rd harmonic frequencies to reduce spurious radiation due to the corresponding patch modes to avoid the radiation of harmonic signals generated by non-linear devices at the amplifying stage. The study shows the possibility of controlling the second harmonic resonance matching by varying the length of the feeding line. On the other hand, the suppression of the third harmonic is achieved by using a compact resonator. This resonator consists of a printed metallization with a via connected to the ground plane (mushroom type) in a multilayer configuration. Comparing with conventional electromagnetically coupled patch antenna, the radiated power of the proposed antenna at the 2nd and 3rd harmonic frequencies is reduced by 14 dB and 8 dB, respectively.
