One of the fundamental problems in power amplifier (PA) design is the mismatch between the optimum loads for maximum output power and maximum efficiency. This work demonstrates that a GaN transistor of choice can reduce such mismatch when operating at the minimum input RF power required ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\text {in}}$ </tex-math></inline-formula> ) to obtain its maximum output power. Furthermore, this work investigates the average power-added efficiency (PAE) degradation caused by the baseband terminations for high-efficient switch-mode class-E PAs. Our results show that the average PAE degradation mechanism of class-E PAs is similar to that of class-B ones, but some class-E solutions are more susceptible to the driving signal’s bandwidth. To clarify that, two class-E PAs were implemented using commercial package GaN transistors based on two different modes from the continuum of class-E solutions. Despite being driven by half of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\text {in}}$ </tex-math></inline-formula> typically employed by designers, the PAs have achieved a gain almost 3 dB higher than the state-of-the-art and excellent efficiency controlling only the second harmonic. Based on the obtained results, the proposed design strategy is believed to have a promising potential for developing high-efficiency simultaneous wireless information and power transmission (SWIPT) base stations for batteryless Internet of Things (IoT).

High-Efficiency Moderate-Power Amplifier Using Packaged GaN Transistor With Improved Average PAE and Gain for Batteryless IoT Applications

This paper presents a method to expand the bandwidth of conventional class-F power amplifier. Analysis indicates that small characteristic impedance of quarter-wave shorted-circuit transmission line in the harmonic control network is beneficial for PA design, as the second harmonic impedance varies less with frequency variation. A 10W GaN packaged transistor is used to verify the proposed method. The measured results show that the PA exhibits a good performance at the center frequency 2.6 GHz with 74.37% drain efficiency, 40.82 dBm output power and 11.82 dB gain. Besides, the PA maintains more than 60% drain efficiency over the bandwidth of 250 MHz.

Design of a class-F power amplifier with expanding bandwidth

A new X-band retrodirective antenna based on superheterodyne mixer and phase conjugating technology is proposed for inter-satellite data transmission in this paper. The novel phase conjugating circuit, utilizing the reciprocity of the passive mixers, achieves high RF-IF and LO-IF isolations, high communication link gain, and a very compact low profile layout with all antenna elements and circuit components arranged at one common layer of a double-sided printed circuit board (PCB). Its mathematical principles of circuit design are derived, and the effect of up and down conversion loss deviation of mixers on the amplitude and phase error of the circuit, thus on the beam pointing error and the side-lobe of the antenna is discussed. A prototype of circularly polarized one dimension retrodirective antenna is fabricated, and its bistatic RCS measurement in an anechoic chamber is implemented to verify the effectiveness of the proposed antenna array. The results show that, within the scanning range from -30° to +30°, the array has good retrodirective performance. The proposed antenna would be a good choice for the inter-satellite data transmission inside a distributed satellite cluster.

/pdf/retrodirective-antenna-for-inter-satellite-data-transmission-3yejgf3ar9.pdf

Retrodirective Antenna for Inter-Satellite Data Transmission

A microwave power transmission (MPT) demonstration system was assembled to comprehensively emulate the operating mode of MPT in space solar power station (SSPS). Based on solid power amplifier and phased antenna array, this system comprised three main parts, that is, microwave power transmitting subsystem, microwave power rectenna subsystem, and power beam steering subsystem. It was employed to validate the constraint relationship between beam collection efficiency and the sizes of transmitting antenna and rectenna, transmission distance, operation frequency. High efficiency rectifying and accurate beam steering were also demonstrated. The power transmitting antenna was composed of 64 sub‐arrays of patch antennas, with the dimension of 1.2 × 1.2 m2. In addition, the rectenna array was constructed as a corner truncated square with the side length of 2 m. Its design was based on the concept of perfectly matched layer and integrated rectifying surface. The power beam steering subsystem, implemented with software retrodirective idea, pointed the microwave beam to the rectenna according to the direction of arrival of the pilot signal. The experimental MPT system, operating at 5.8 GHz, transmitted 910 W microwave power across 30 m distance. At the power receiving end, the optimum rectenna conversion efficiency of 49.3% was obtained. With aid of the beam steering subsystem, beam granularity, and beam steering accuracy of 0.23 and 0.18° were achieved, respectively. The compositive experiment verified all function as power transmitting, receiving, rectifying, and steering of MPT system. MPT technology is thus driven toward engineering application, and will ultimately space solar power exploration.

Design of a microwave power transmission demonstration system for space solar power station

In this letter, a self-packaged substrate-integrated suspended line (SISL) rectifier is proposed. The rectifier consists of a quarter-wavelength high-impedance transmission line, a diode, a tuning inductor, and a dc pass filter. The lower the power is, the lower the rectifying efficiency is. At a low input power level, the diode impedance real part is almost zero. A tuning inductor is introduced to form a parallel resonator to enhance the diode voltage. A quarter-wavelength high-impedance line is presented to match the rectifying diode to the source. In addition, due to the self-packaging characteristics and air cavity of SISLs, the radiation loss and dielectric loss of the proposed rectifier are reduced. A rectifier was designed, fabricated, and measured at 5.8 GHz. The radio frequency (RF)-dc conversion efficiency reaches 3.5% at −30 dBm, which is close to its theoretical estimated efficiency at 5.8 GHz. This ultralow power rectifier may be used in energy harvesting at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -band.

A Self-Packaged SISL Low-Power Rectifier Based on a High-Impedance Line for C-Band Applications

Microwave power transmission is one of the key technologies to realize solar power satellite. In this paper, the authors design a high efficiency GaN Class-F power amplifier at 2.45GHz. Power added efficiency is up to 78.8% and output power is 40.3dBm in simulation. Simulated results predict high performance of the proposed PA.

Design of high efficiency GaN HEMT class-F power amplifier at S-band

This paper presents a microwave power transmission demonstration system comprehensively simulating the operating mode and validating the functions and efficiency of microwave power transmission technologies for SSPS (Space Solar Power Station). The transmitting antenna array is a planar microstrip antenna array with quasi-Gaussian distribution. The beam collecting efficiency of this system is about 94% analyzed by theoretical transmission equation and radiation field integral method respectively. Compared with uniform distribution, the beam collecting efficiency in this system is well enhanced.

Beam collecting efficiency analysis in microwave power transmission demonstration system for SSPS

A polarization auto-matching retrodirective method is proposed in this paper. Using phase conjugating circuits and polarization rotators, it can receive any polarized pilot signal and generate predictable polarized beam aimed back to the rectenna. Phase conjugation with heterodyne mixing is executed twice to lower LO frequency and reduce phase error. The polarization mismatch loss and interference between power beam and pilot signal can be decreased to improve transmission efficiency.

A polarization auto-matching retrodirective method

Microwave power transmission is the key of space solar power station. Microwave power transmitting array is introduced firstly. Using Wilcox expansion spatial structure of electromagnetic field is discussed, especially in the Fresnel region. Power distribution is depicted subsequently.

Spatial structure of electromagnetic field in the power transmitting antenna fresnel region

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Papers

Design of high efficiency GaN HEMT class-F power amplifier at S-band

Beam collecting efficiency analysis in microwave power transmission demonstration system for SSPS

A polarization auto-matching retrodirective method

Spatial structure of electromagnetic field in the power transmitting antenna fresnel region