Zhiqun Cheng

Polarization-Reconfigurable Circularly Polarized Planar Antenna Using Switchable Polarizer

A novel polarization-reconfigurable planar antenna is presented. The antenna consists of an electronically reconfigurable polarizer integrated with a printed slot. By changing the states of the p-i-n diodes on the polarizer, the linearly polarized (LP) waves radiated by the slot can be converted into either right-hand circularly polarized (RHCP) or left-hand CP (LHCP) waves. The polarizer contains 16 unit cells arranged as a

15158A SP6T RF switch based on IBM SOI CMOS technology

4\times 4

3-D Coverage Beam-Scanning Antenna Using Feed Array and Active Frequency-Selective Surface

array. The antenna radiates RHCP waves if the p-i-n diodes on the top side of the polarizer are switched ON, while LHCP waves are radiated if the p-i-n diodes of the bottom side of the polarizer are switched ON instead. The physical mechanisms of the antenna are discussed and the parametric study is carried out by full-wave simulations. To verify the concept, one prototype at 2.5 GHz is designed, fabricated, and measured. Good agreement between the measured and simulated results is obtained. The antenna achieves a gain ≥8.5 dBic in both RHCP and LHCP with an aperture efficiency of 70%. Advantages of the proposed design include electronically reconfigurable polarizations for RHCP or LHCP, low profile, low cost, high isolation between the dc bias circuit and RF signals, high power handling capability, and easy extension to large-scale arrays without increasing the complexity of the dc bias circuit. To the best of our knowledge, this is the first report of an electronically polarization-reconfigurable CP antenna with a single-substrate polarizer.

A broadband high-efficiency Doherty power amplifier using symmetrical devices

This paper presents the design of single-pole six-throw (SP6T) RF switch with IBM 0.18 μm SOI CMOS technology, which can be widely used in a wireless communication system with its high performance and low cost. The circuit is designed and simulated by using an idea that the total load is divided into six branches and SOI special structures. The insertion loss is less than 0.6 dB, isolation is more than 30 dB, the input power P0.1dB for 0.1 dB compression point is more than 37.5 dBm, IIP3 is more than 70 dBm, the 2nd and the 3rd harmonic compressions are more than 96 dBc, and the control voltage is (+2.46 V, 0, −2.46 V) in the frequency from 0.1 to 2.7 GHz.

Bandwidth enhancement of three-device Doherty power amplifier based on symmetric devices

This paper presents the design of a smart antenna that can achieve 3-D beam-scanning coverage. The antenna consists of a novel planar feed array and a cylindrical active frequency-selective surface (AFSS). First, an array fed metallic reflector is studied as a reference antenna to validate the beam-scanning characteristics in the elevation plane. Then, the AFSS is assessed through simulation and measurement results. Finally, the complete structure containing the planar collinear array and the AFSS is analyzed. A prototype at S-band has been designed, manufactured, and measured. The resulting antenna is shown to be able to operate at the 2.4–2.5 GHz frequency band and switch beams in both the azimuth and elevation planes. In the azimuth plane, the proposed antenna is capable of sweeping beams toward different directions to cover a full range of 360°. In the elevation plane, it can achieve beam steering within an angle range of +16°/ − 15°. The measured maximum gain of the antenna is 9.2 dBi. This is the first report of a low-cost 3-D coverage beam-scanning antenna based on AFSS.

A High-Efficiency Compact Planar Antenna for ISM Wireless Systems

This paper proposes a method for broadband and high-efficiency amplification of Doherty power amplifier (DPA) using symmetric devices. In order to achieve the perfect load modulation, the carrier amplifier output circuit total power length is designed to odd multiple of 90°, and the peak amplifier output total power length is designed to even multiple of 180°. The proposed method is demonstrated by designing a broadband high-efficiency DPA using identical 10-W packaged GaN HEMT devices. Measurement results show that over 51% drain efficiency is achieved at 6-dB back-off power, over the frequency band of 1.9–2.4 GHz.

Compact Multiband Interdigital-Coupled-Fed Planar Antenna with Stepped-Impedance Structures for Mobile Handsets

This paper proposes a method for extending the bandwidth of a three-device Doherty power amplifier (DPA) based on symmetric devices. ?/4 transmission lines are inserted between each peaking amplifier output and carrier amplifier output to compensate load impedance of carrier amplifier. In order to achieve perfect load modulation, carrier amplifier output circuit total electrical length is designed to 90 degrees, and the peak amplifier output total electrical length is designed to 180 degrees. The proposed method is demonstrated by designing a three-device broadband DPA using three 10-W packaged GaN HEMT devices. Measurement results show that over 40% drain efficiency is achieved at 9-dB back-off power, over the frequency band of 1.45–2.35 GHz, accounting for 46% fractional bandwidth.

A Doherty power amplifier with extended efficiency and bandwidth

A novel high-efficiency compact planar antenna at 433 MHz with minimized size and low-cost and easy to integrate into the ISM wireless applications is designed, fabricated, and measured. Capacitive strips that are formed by cutting inter-digital slots and the meander lines on both sides are introduced to greatly reduce the antenna size yet maintain the high efficiency. The proposed antenna has a simple planar structure and occupies a small area (i.e., 45 × 30 mm2). This novel electrically small antenna can be operated well without any lumped elements for impedance matching. Details of the antenna design and experimental results are presented and discussed.

Frequency-Agile Beam-Switchable Antenna

A new compact multiband planar antenna combining an interdigital-coupled feeding line and one stepped-impedance structure is presented here. This antenna is capable of generating five resonant modes to cover the ISM 915/2400/5800 MHz bands, GPS band, and IMT C-band, respectively. The five resonant frequencies covered by the proposed antenna can be adjusted individually by controlling the impedances and electrical lengths of the corresponding stepped-impedance sections. An additional advantage of the proposed stepped-impedance structure is its ability to suppress higher order resonance modes, thus filtering out unwanted interference. The proposed antenna utilizes a simple planar compact structure and occupies a small area of only 12 × 30 mm2. Details of the antenna design and experimental results are presented and discussed.

Design of 0.8–2.7 GHz High Power Class-F Harmonic-Tuned Power Amplifier with Parasitic Compensation Circuit

This paper proposes a modified Doherty power amplifier (DPA) configuration for bandwidth and efficiency operations. To mitigate the efficiency degradation resulting from the incomplete load modulation network (LMN) and the knee voltage effect, the carrier transistor’s optimum load impedances based on related constant voltage standing wave ratio (VSWR) circle theory are introduced. Meanwhile, a innovative LMN with broadband matching technologies is adopted, which plays a guiding role on the bandwidth expansion from the theoretical point of view. In order to verify the practical feasibility of the design scheme, two 10W GaN HEMT transistors are used to design a broadband DPA. The measurement results show that the working bandwidth of the power amplifier is from 1.6GHz to 2.6GHz. The saturated output power of the whole frequency band is about 41.7–44 dBm and the drain efficiency (DE) is more than 50.8% at the input power of 33 dBm. In addition, the DE is 41.5–45% at 6-dB back-off power. Measurement results verify that the proposed enhancement techniques of bandwidth and efficiency are effective for DPA.