on-Sik Cho

A Novel Dual-Band Wilkinson Power Divider Using Branch-line

Power combiners/dividers are frequently used in wireless-communication systems, specifically for phased array antenna, vector modulator, and mixer. Due to multi-band requirements, various dual-band circuits based on lumped and distributed elements have been reported recently.This paper proposes a novel dual band Wilkinson power divider based on the ring resonator topology with branch-line. The branch-line plays a key role in obtaining the dual-band operation.

An enhancement of input impedance bandwidth of circular-disc loaded monopole antenna with horizontal and vertical parasitic strips

In this paper, a monopole antenna with a circular disc at the top and parasitic strips around antenna is analytically investigated and simulated using the mode-matching technique and a commercially available software package, CST MW Studio based on FDTD algorithm. Mode-matching technique with boundary conditions are applied to compute the unknown modal coefficients in each region. For the usefulness of mode-matching technique to open boundary, the artificial ground plane is added away from the top- loading disc. Compared results between two methods show that the proper radius and height of parasitic elements can reduce the peak value of input impedance at the resonant frequencies over wide bandwidth without power dissipation due to lossy material used in conventional ways.

A Highly Linear Self Oscillating Mixer Using Second Harmonic Injection

In this paper, a highly linear self oscillating mixers(SOM) using second harmonic injections are presented. The H-slot defected ground structure(DGS) is designed as a balanced resonator for oscillation in the proposed SOM. Since the H-slot DGS resonator achieves a high Q factor, it is a suitable structure to provide low phase noise for the oscillator. The single balanced mixer is utilized in this work and it provides good LO-RF isolation since balanced LO signals are suppressed at the RF input port. In order to inject the second harmonic of the IF, we propose two different methods using feedback loops. In the first method, IF achieves a 3.08 dB conversion gain at 226 MHz with input power of -20 dBm at 5 GHz RF input signal. The IF achieves 2 dB conversion gain at 423 MHz with the input power of -20 dBm at 5.2 GHz RF input signal in the second method. The measured IMD3s are 61.8 dB and 65 dB for the each method. These SOMs present improved linearity compared to that without the second harmonic injection because IMD3s are improved by 18. dB and 21 dB for each method.

A Dual - Band Planar Inverted-F Antenna with Periodic Grooves

This paper describes a design of dual-band antenna design resonating in PCS and cellular frequency band. In order to accomplish this goal, the PIFA (planar inverted-F antenna) with periodic grooves is suggested and analyzed by using a commercially available software package based on the FDTD algorithm. In addition to that, the experimental results are compared with the predicted data obtained from the software package, CST MW Studio. Finally, the concept and characteristics of the periodic grooves are introduced and a variation of resonant frequency occurring from the enforcement of periodic grooves on the planar antenna is shown in this paper

A triple-band antenna using CPW-fed and meander-line for PCS/IMT-2000/Bluetooth applications

In this paper, the design procedure and electrical performance of a new triple-band antenna are reported and investigated. The operating frequency of the proposed antenna includes the PCS/IMT-2000/Bluetooth bands for the mobile communication system. It adopt the CPW-fed structure that is easily integrated with MMIC and fabricated in a simplified configuration. For the radiating elements, the proposed antenna employs a meander-line structure for size reduction. By adjusting the gap of the CPW ground and the feed line, the antenna achieves a good matching between the input impedance of the antenna and microstrip feed line. The resonant frequency was obtained by adjusting the length of the meander-line, the relative position of the CPW feed line and radiating elements (R). in addition, the width of the radiating elements and the size of the CPW ground play important roles in achieving increased input impedance bandwidth. 10dB return loss with the required bandwidth can be obtained by adjusting the gap of the meander-line. It is expected that the proposed antenna is small enough to be applicable for practical mobile communication systems.

A CPW-fed self-affine fractal antenna

A new CPW-fed self-affine fractal antenna, which has a novel configuration, is proposed and investigated for low profile and multi-band performance in mobile communication systems. The vastly different structure can be created from a simple rectangular patch while the number of iterations increases. The proposed antenna provides a radiation pattern similar to that of a simple monopole antenna oriented in the y-direction. In addition, the effect of the iteration coefficient, k, on the fundamental resonant frequency is studied along with the procedure of antenna design and experimental results.

Time-Efficient SE(Shielding Effectiveness) Prediction Method for Electrically Large Cavity

It is generally well-known that the inevitable high power electromagnetic wave affects the malfunction and disorder of electronic equipments and serious damages in electronic communication systems. Hence, it is necessary to take measures against high power electromagnetic(HPEM) wave for protecting electronic devices as well as human resources. The topological analysis based on Baum-Liu-Tesche(BLT) equation simplifying the moving path of electromagnetic and the observation points and Power Balance Method(PWB) employing statistical electromagnetic analysis are introduced to analyze relatively electrically large cavity with little time consumption. In addition to the PWB method, full wave results for cylindrical cavity with apertures and incident plane wave are presented for comparison with time-consumption rate according to the cavity size.

Linearity Enhancement of RF Power Amplifier Using Digital Pre-Distortion Based on Affine Projection Algorithm

In this paper, we design a digitally pre-distorted RF power amplifier operating in 900 MHz band. The linearity of RF power amplifier is improved by employing the digital pre-distortion(DPD) based on affine projection(AP) algorithm, where the look-up table(LUT) method is used with non-linear indexing. The proposed DPD with AP algorithm is compared with that with normalized least mean square(NLMS) algorithm, applied to the RF power amplifier. A commercial power amplifier module is used for verification of the proposed algorithm which shows improvement of adjacent channel leakage ratio(ACLR) by about 21 dB.

Linearity Enhancement of RF Power Amplifier Using Digital Predistortion with Tanh as a Nonlinear Indexing Function

In this paper, we design a digital predistortion(DPD) for linearity enhancement of RF power amplifier operating in 900 MHz band. We verify improvement of linearity by comparing the proposed DPD using tanh as a nonlinear indexing function and the DPD using linear indexing function based on signal amplitude. The digital predistortion is realized by look-up table(LUT) method, and the Saleh model is employed for power amplifier modeling, then a commercial power amplifier module is used for measurement. The LUT has 256 tables, and the NLMS(Normalized Least Mean Square) algorithm was utilized for an adaptive algorithm for estimation. As a result, we improve the ACLR(Adjacent Channel Leakage Ratio) by around 15 dB.

Design and Measurement of Active Phased Array Radar Digital Receiver

Active phased array antenna structure is used for modern multi-function radars. To search targets in high clutter environment, the radar receiver needs high dynamic range performance. Though active phased array antenna structure lead to increase of SNR, the SFDR is not increased. In this paper, high SFDR receiver of X-band active phased array radar was designed and manufactured. One channel digital receiver is connected to 32 T/R modules and one PCB assembly is composed to 2 channel digital receivers with RF part, ADC part, LO distribution part and digital down conversion part. A commercial FIFO board was used for digital receiver measurement about major performance in digital output signal condition. The measured digital receiver gain and SFDR is 33 dB and more than 81 dBc each.