A closely located dual-band meander-line antenna array with isolation enhancement by inserting novel split electromagnetic bandgap (EBG) uniplanar structure is proposed. The meander-line antenna is ...coupled to a parasitic rectangular patch to achieve the dual-band operation. Splits are applied on the surface of an EBG structure to cause decoupling at the first resonant mode and utilizing an EBG structure to decouple at the second resonant mode. The prototype of the proposed structure achieves a dual band of 180 MHz (3.42-3.6 GHz) and 400 MHz (4.7-5.1 GHz). The mutual coupling is significantly reduced by 26 and 44 dB at 3.48 and 4.88 GHz, respectively, compared to the reference antenna. In addition, the structure has high front-to-back ratio radiation characteristics.
A new synthesis method for the design of broadband impedance matching network has been introduced to match the transistor input. The proposed matching network would be a realistic alternative to ...those that are frequently designed in low-pass structure. Easy-to-use design equations are given for this filter-based matching network. The required impedance of the stubs and the connecting lines can be directly calculated from the equations. This synthesis method simplifies the implementation of the network in the distributed form as compared with the LC low-pass matching network where equivalences are necessarily required in the rough conversion from lumped-to-distributed elements. The high-efficiency mode of operation is guaranteed by the constructed output low-pass matching network, since the LC low-pass network can provide the prescribed load terminations at fundamental frequencies and at harmonics. A commercially available 10-W GaN HEMT device (CGH40010) was used in this investigation. The proposed broadband power amplifier exhibits band-pass Chebyshev response in S-parameter measurements, and yields good gain flatness (±0.5 dB) and input return loss (>13 dB). Power-added efficiency of 58%-72% has been measured in large-signal measurements. After digital predistortion, the measured adjacent channel leakage power ratio is below -50 dBc at ±5- and ±10-MHz offset, when driven by 5- and 10-MHz WCDMA signals at 7-dB power back off.
This paper presents an unequal Wilkinson power divider operating at arbitrary dual band without reactive components (such as inductors and capacitors). To satisfy the unequal characteristic, a novel ...structure is proposed with two groups of transmission lines and two parallel stubs. Closed-form equations containing all parameters of this structure are derived based on circuit theory and transmission line theory. For verification, two groups of experimental results including open and short stubs are presented. It can be found that all the analytical features of this unequal power divider can be fulfilled at arbitrary dual band simultaneously.
A novel generalized coupled-line circuit structure for a dual-band Wilkinson power divider is proposed. The proposed power divider is composed of two coupled lines with different even- and odd-mode ...characteristic impedances and two lumped resistors. Using rigorous even- and odd-mode analysis, the analytical design equations for this proposed power divider are obtained and the ideal closed-form scattering parameters are constructed. Since the traditional transmission line is a special case of coupled line (coupled coefficient is zero), it is found that traditional noncoupled-line dual-band (including single band) Wilkinson power dividers and previous dual-band coupled-line power dividers are special cases of this generalized power divider. As a typical example, which could only be designed by using this given design equations, a compact microstrip 3-dB power divider operating at both 1.1 and 2.2 GHz is designed, fabricated, and measured. There is good agreement between calculated and measured results.
In this paper, a novel broadband Doherty power amplifier based on the continuous-mode technique (C-DPA) is proposed. The amplifier is focused on manipulating harmonic components in a Doherty power ...amplifier (DPA) structure to achieve improved bandwidth and efficiency. In a conventional DPA, harmonic isolation is typically required between the two transistors to prevent them from modulating each other at harmonic frequencies. However, as presented in this paper, such isolation is not actually necessary. On the contrary, by allowing the two transistors to modulate each other at harmonic frequencies with the help of a properly designed postharmonic tuning network, a series of highly efficient DPA modes can be created over a continuous frequency band, leading to a broadband C-DPA. Based on the proposed method, an example of a C-DPA working from 1.65 to 2.75 GHz was designed. According to the measured results, the designed C-DPA exhibits a 52%-66% efficiency at a -6 dB power backoff and a power utilization factor higher than 1.08 over the 1.1-GHz band. In addition, when simulated by a 7.5-dB peak-to-average power ratio 20-MHz LTE signal, the example C-DPA exhibits an efficiency of 46%-62% while maintaining an adjacent channel power ratio below -45 dBc after linearization over the full 1.1-GHz band. To the best of our knowledge, this is the first proposed C-DPA and a state-of-the-art performance for broadband DPAs.
In this paper, a novel terminated coupled line structure (TCLS) is introduced, which is constructed by a coupled line section and four terminations loaded on it. Introducing different kinds of ...terminations, three types of bandpass filters (BPFs) based on TCLSs are proposed, theoretically analyzed, and fabricated, including two single-ended wideband BPFs with fractional bandwidths (FBWs) of 67% and 40% respectively, and a wideband differential BPF with 74% differential-mode FBW. These BPFs can achieve wide passband bandwidth, low in-band insertion loss, high passband selectivity, as well as deep stopband rejection performance simultaneously, benefited from the multiple transmission zeros and transmission poles obtained by the TCLSs. The practical design procedures of these BPFs are presented and explained. The agreement among theoretical predictions, EM-simulated, and measured results validates our proposed filter structures. Finally, the generalized multistage filter topology based on TCLSs is proposed to design high-order filters with better filtering performances.
A circularly polarized (CP) patch array antenna is proposed for ultrawideband operation by introducing weak-coupling mechanism into feeding network, feeding unit, and radiation structure, ...respectively. As an example, a wideband 2×2 patch array antenna consists of a weakly coupled-line four-feed network, a coupled feeding unit, and four weakly coupled sequentially rotated symmetric hexagonal patches is designed for verification. Measured results show that the proposed antenna exhibits the 10-dB impedance bandwidth of 98% (2-5.92 GHz), 3-dB axial ratio bandwidth of 96.3% (2.15-6 GHz), and 3-dB gain variation bandwidth of 82.5% (2.65-5.95 GHz) with the peak gain of 9.5 dBic at 5.15 GHz and the maximum efficiency of 88%. By the weak-coupling method, the design achieves not only the largest CP bandwidth and the symmetric radiation patterns without any beam squint over the whole band, but also the smaller volume of (1.13 × 1.13 × 0.15) λ 3 0 (λ 0 is the wavelength at 4 GHz) compared with the reported patch array antennas. Therefore, the proposed CP patch array antenna is very promising for modern wireless applications such as WiFi, global navigation satellite system, and radio frequency identification systems.
This paper presents a compact 0.92/2.45-GHz dual-band directional circularly polarized (CP) microstrip antenna for handheld radio-frequency identification (RFID) reader applications. The proposed ...antenna comprises a wideband dual-feed network and two stacked concentric patches assembled by two orthogonally placed vertical probes. The dual-feed network feeds quadrature signals across the RFID bands between 0.92 and 2.45 GHz. The two stacked concentric patches provide resonance frequencies in fundamental mode for lower band and higher band, respectively. Additionally, the antenna features only one connection port and same sense CP radiation at two bands, beneficial to cost and complexity reductions of the dual-band front end of RFID readers. The measurement results show the performances of return loss (RL) >10 dB, 3-dB gain variation, and axial ratio (AR) <;3 dB are achieved on the bands 0.911-0.933 GHz and 2.40- 2.57 GHz. The measured peak gains are 3.8 dBic at 0.926 GHz and 8.9 dBic at 2.48 GHz. In addition, the antenna provides symmetrical patterns with wide-angle half-power beamwidths and wide-angle 3-dB AR beamwidths. The size of the antenna 110 × 110 × 6.6 mm 3 is much smaller than reported dual-band one port RFID directional CP reader antennas. The antenna appropriates to both ultra-high frequency (UHF) and industrial scientific and medical (ISM) bands in handheld RFID reader applications.
A dual-band 0.92/2.45 GHz circularly-polarized (CP) unidirectional antenna using the wideband dual-feed network, two orthogonally positioned asymmetric H-shape slots, and two stacked concentric ...annular-ring patches is proposed for RF identification (RFID) applications. The measurement result shows that the antenna achieves the impedance bandwidths of 15.4% and 41.9%, the 3-dB axial-ratio (AR) bandwidths of 4.3% and 21.5%, and peak gains of 7.2 dBic and 8.2 dBic at 0.92 and 2.45 GHz bands, respectively. Moreover, the antenna provides stable symmetrical radiation patterns and wide-angle 3-dB AR beamwidths in both lower and higher bands for unidirectional wide-coverage RFID reader applications. Above all, the dual-band CP unidirectional patch antenna presented is beneficial to dual-band RFID system on configuration, implementation, as well as cost reduction.
In this paper, a novel design method of generalized dual-band unequal filtering power divider (DUFPD) is proposed. Using this method, the power divider (PD) could be designed to realize the dual-band ...filtering response with arbitrary power division, arbitrary frequency ratio, arbitrary real terminated impedances, independently controllable bandwidth, and excellent isolation. To satisfy these characteristics, a proper dual-band filtering structure is selected to replace the conventional quarter-wave length transmission line in the PD. In addition, a single resistor structure is utilized to obtain effective isolation between the output ports. Furthermore, the complete design procedures and analytical equations of the proposed generalized DUFPD are presented based on the circuit and transmission line theories. To demonstrate the validity of the proposed design method, a DUFPD with different real terminated impedances is designed, fabricated, and measured. We show that there is a good agreement between the simulated and measured results.
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