A novel asymmetric coplanar strip (ACS)-fed multiple-input-multipleoutput (MIMO) antenna working in the ultra-wideband (UWB) frequency band with a shared radiator is discussed. The proposed antenna is composed of a radiator which is shared by two antenna elements in order to achieve a very compact size of 26 × 26 mm 2 . By etching an I-shaped slot in the radiator and attaching a rectangular patch on the back, the operating bandwidth is broadened and a high isolation between the two antenna elements is realised. The stub from the ground also has a great effect on the return loss and isolation. The measured results show that the working frequency band of the MIMO antenna covers 3.1-10.6 GHz with an isolation of more than 15 dB. Furthermore, the simple feeding structure and compact size could enable the proposed antenna to be used in portable devices.Introduction: Ultra-wideband (UWB) technology possesses great merits including high data rate, low cost and easy fabrication [1], but this excessively researched technology suffers from multipath fading. To solve this problem, a multiple-input-multiple-output (MIMO) antenna was introduced [2]. However, when two antenna elements work closely to each other, the mutual coupling between the two antenna elements becomes strong and the MIMO antenna cannot reach high isolation and a wide operating band without further steps being taken [3]. Li and Feresidis [4] introduced a double-layer EBG structure where three slit-patch structures are inserted in the ground plane between two closely placed UWB monopoles, and the isolation of the whole working frequency band is larger than 15 dB. Gao and He [5] presented a 5.5 GHz band-notched UWB-MIMO antenna using a coplanar waveguide (CPW)-fed to achieve a small size of 48 × 48 mm 2 and a stub from the ground, which could enhance the isolation to more than 15 dB in its operating frequency band. Liu and Wang [6] demonstrated a MIMO antenna using an asymmetric coplanar strip (ACS)-fed structure to reach a compact size of 28.5 × 28.5 mm 2 ; in order to raise the isolation between the two antenna elements, a stub stretched from the ground is introduced, the impedance bandwidth of the antenna covers the UWB frequency band with an isolation of more than 15 dB.

A miniaturised three-order wideband filtering antenna by employing a composite right/left handed transmission line (CRLH-TL) and a simplified asymmetric coplanar strip feeding structure is presented. The CRLH-TL resonator resonates at zeroth-order mode and first-positive-order mode, and the meander-line antenna performs not only as a radiator but also as the last resonator of the corresponding bandpass filter. The proposed filtering antenna has four poles in the passband and two radiation nulls at the band edges. Compared with conventional antennas, the proposed filtering antenna shows flat gain responses and flat radiated powers within the passband, and displays good frequency skirt selectivity. Measurement results show that the filtering antenna can operate at from 4.03-to 7.11 GHz, has a 3.08 GHz bandwidth, a 2.5 dBi average gain in the broadside (+Z) direction and nearly 30 dBm average radiated power within the passband.

In this paper, a waveform theory for harmonic tuned class E power amplifier (HT class E PA) based on waveform analysis is proposed. This paper uses the waveform theory of class F PAs and class F−1 PAs to solve the problem of harmonic tuning of traditional class E PAs. The equation of normalized current waveform of the class E PA is analyzed, set the phase difference between the current and voltage of the harmonic components to π2, and finally deduced the equation of normalized voltage waveform. This paper replaces the output impedance in the traditional class E PA design with the output impedance obtained from the waveform analysis, which makes the design of the matching network more convenient and ensures that the output current waveform and voltage waveform of the designed new HT class E PA are very close to those of the ideal class E power amplifier. The theoretical efficiency of the new HT class E PA is 89.04%. Based on this theory, a power amplifier is designed using a CREE GaN CGH40010F transistor. Test results show that: the gain can reach 10.7 dB, the output power is 40.7 dBm, PAE is 67.7%, DE is 74%.

No abstract

A novel compact ultrawideband (UWB) CPW-fed antenna with triple lower pass bands and dual notched bands for wireless applications is presented. The low-profile antenna comprises of an approximate hexagonal-shaped radiator for covering the UWB band (3.1 ∼ 10.8 GHz). Triple lower pass bands, the 1.5 Gband, 1.8 GHz GSM band and 2.4 GHz Bluetooth band, can be realized by adding three handstand semielliptical-shaped stubs bilaterally at the upper part of antenna ground. A notched band of 3.3 ∼ 3.7 GHz for rejection of WiMAX radio signals can also be obtained by adjusting the geometry of the three stubs. In addition, an U-shaped slot on the radiating patch generates a notched band in 5.15 ∼ 5.825 GHz for rejection of WLAN radio signals. The proposed antenna is designed and built on a FR-4 substrate, with overall size of 25 mm × 24 mm. The simulated and measured results are presented and show that the proposed compact antenna has a stable and omnidirectional radiation patterns across all the relevant bands.