Younkyu Chung

High isolation dual-polarized patch antenna using integrated defected ground structure

This letter presents a high isolation dual-frequency orthogonally polarized rectangular patch antenna utilizing microstrip feed line integrated with a defected ground structure (DGS). The demonstrated approach results in a significant improvement in port isolation in comparison to a conventional dual-polarized antenna fed by simple microstrip lines. Measurements show an improvement of 20 dB in port isolation relative to the conventional antenna, operating at 2 and 2.5 GHz. Image impedance of a microstrip line with DGS is controlled by the DGS geometry without modifying the dimension of the line. A 150 /spl Omega/ high impedance line is effectively implemented using a microstrip line with 75 /spl Omega/ line width by incorporating the DGS.

Multifunctional microstrip transmission lines integrated with defected ground structure for RF front-end application

This paper presents multifunctional microstrip transmission lines for designing a high port-isolation dual-frequency orthogonally polarized rectangular patch antenna and the antenna-integrated power amplifier. The proposed lines were realized through the integration of defected ground structures (DGSs) with conventional microstrip lines. A spiral-shaped DGS-integrated microstrip line enhances the port isolation of the antenna, while feeding the 2.0-GHz excitation to the antenna and filtering out the 2.5-GHz receiving signal from the other port. High-order harmonic signal suppression of the power amplifier at the 2.5-GHz port was accomplished by the dumbbell-shaped DGS, thereby improving the efficiency of the amplifier. Measurements show an improvement of 20 dB in port isolation and 3% in power-added efficiency relative to an identical RF front-end, but integrated with a conventional patch antenna. An image impedance of the DGS-integrated microstrip lines can be controlled by the integrated DGS geometries. Relatively high-impedances lines, i.e., 150 and 100 /spl Omega/, are effectively implemented using microstrip lines with 75- and 50-/spl Omega/ linewidths by incorporating the spiral- and dumbbell-shaped DGSs, respectively.

Reconfigurable power divider and combiner with variable power ratio

This paper presents the design of a power divider and combiner with variable power ratios. The essential idea is to use the operating principle of coupled-line coupler. The couple-line coupler, which has control switches at the coupled and the isolation ports, offer several different operating conditions depending on the state of the switches. By means of changing the terminating-state of the coupled and the isolation ports, short or open, the power ratio becomes 1:1 or 1:0. The input power is either equally divided into two output ports or delivered to the one output port exclusively.

Power level-dependent dual-operating mode LDMOS power amplifier for CDMA wireless base-station applications

The design and analysis of a dual-operating mode laterally diffused metal-oxide semiconductor (LDMOS) power amplifier for code-division multiple-access wireless communication base-station applications is presented in this paper. The amplifier structure consists of four parallelly located single-stage LDMOS amplifier array, the dual-mode input power divider, and output power combiner. In this dual-mode operation, the number of operating power amplifier (either one or four amplifiers) is controlled depending on the required power level. This results in significant improvement in efficiency performance of the amplifier by minimizing unnecessary dc power consumption. In addition to the enhancement of efficiency, the amplifier design approach also provides better overall linearity performance. The proposed dual-operating mode design technique was successfully demonstrated by designing, implementing, and testing an LDMOS power amplifier with Motorola MRF 21030 in this study

Effects of output harmonic termination on PAE and output power of AlGaN/GaN HEMT power amplifier

The authors experimentally investigate and discuss the effects of output harmonic termination on power added efficiency (PAE) and output power of an AlGaN/GaN high electron mobility transistor (HEMT) power amplifier (PA). The AlGaN/GaN HEMT PA with gate periphery of 1 mm was built and tested at L-band. Large-signal measurements and comparisons of the PAE and output power were carried out at different DC bias conditions from 50% of saturated drain current (I/sub dss/) to 1% of Id., for the PA with and without output harmonic termination. For class-AB operation at 25% of I/sub dss/, an increase of about 10% in peak PAE and 1 dBm in output power were observed in saturated output power range. Improvements of up to 9% in PAE and 1.2 dBm in output power were achieved over the measured DC bias conditions provided the output harmonics are properly terminated.

Output harmonic termination techniques for AlGaN/GaN HEMT power amplifiers using active integrated antenna approach

In this paper, effects of output harmonic terminations on PAE and output power of AlGaN/GaN HEMT power amplifier are investigated. Using a traditional method of harmonic termination, we observe a substantial increase in PAE and output power. Further, we demonstrate the high efficiency AlGaN/GaN HEMT power amplifier with harmonic termination characteristics by using the active integrated antenna approach. For the microstrip-based AlGaN/GaN HEMT power amplifier, large signal measurements and comparisons of PAE and output power were done in class-AB operation with and without output harmonic terminations. For the antenna integrated power amplifier using an AlGaN/GaN HEMT with 1 mm gate periphery, output power of 30 dBm and peak PAE of 55 % with a power gain of 14 dB were achieved at a drain voltage of 18 V and a gate voltage of -2.8 V.

Alternating input power dividing technique for high conversion gain frequency doubler

This paper presents a new frequency doubler scheme with significant conversion gain improvement. The new design approach utilizes switching operation of FETs. All input power, in this configuration, is directed alternately to each single branch of a pair of parallelly connected FETs corresponding with the polarity of the anti-phase input signal without split of the input power, thereby resulting in enhancing conversion gain. Measurement results demonstrate improvement of 2.87 dB in conversion gain and output power relative to a single-ended structure. For doubling from 5 to 10 GHz the new scheme shows a maximum conversion gain of 11.67 dB.

Efficiency-enhancing technique: LDMOS power amplifier using dual-mode operation design approach

This paper presents an input power-dependent high-efficiency LDMOS power amplifier by employing a dual-mode operation design approach. The proposed amplifier scheme provides two different operating modes depending on the power level: low or high input power modes. By controlling the number of operating amplifiers in each mode, the efficiency of the amplifier at low power level is substantially improved. Four single stage LDMOS power amplifiers with Motorola MRF 21030 were incorporated with a dual-mode input power divider and output power combiner. In the proposed operation, either one or four amplifiers were activated. The measurement results show a 50 dBm saturated output power and 40% PAE in high input power mode, when four amplifiers are active. By switching the operation to the low input mode, when the input power was relatively low, a 5% increase in PAE was obtained.

Design of a 90/spl deg/ hybrid coupler with harmonic rejection characteristic

In this paper, a 90/spl deg/ hybrid coupler with the power dividing as well as harmonic rejection performance is presented. This circuit technique was realized by integrating the fundamental operation of a conventional 90/spl deg/ hybrid with a LPF characteristic. The proposed 90/spl deg/ hybrid coupler power provides not only the power dividing capability and proper phase difference but also harmonic suppression characteristic. Two types of 90/spl deg/ hybrids were successfully demonstrated by using five-pole/three-pole and five-pole/five-pole filters.