Bong Su Kim

An implementation of harmonic-suppression microstrip filters with periodic grooves

In this paper, a new parallel-coupled-line microstrip band pass filter (BPF) improving the harmonic suppression performance of the second harmonic signal (2f/sub o/, twice the passband frequency) is described. It is found that the desired passband performance is improved and the harmonic passband signal is diminished by enforcing the consecutive patterns in coupled-line and increasing the number of grooves to the optimum values. The recalculation of design parameters such as space-gap between lines, line widths and lengths is not required due to the simple modification of the conventional filter by inserting periodic patterns. To evaluate the validity of this novel technique, order-3 Butterworth BPF centered at 2.5 GHz with a 10% fractional bandwidth (FBW) and order-5 Chebyshev BPF centered at 10 GHz with a 15% FBW were used. When five and three square grooves are used, over 30-dB suppression at second harmonic signal is achieved in simulation and experiment. Finally, the comparison between the characteristics of filters with square and semicircular periodic grooves has been carried out by using the simulated results.

PCB substrate integrated waveguide-filter using via fences at millimeter-wave

In this paper, the implementation and the embedding method of the existing air-filled waveguide-filters at millimeter-wave on general Printed Circuit Board(PCB) substrate are introduced by systematically inserting the vias inside waveguide and mathematically manipulating the simple equations obtained from the classical circular-post waveguide the wave propagation. Because the mass production on PCB is possible without fabricating a large-scaled metal waveguide of WR-22 as input/output ports at millimeter-wave, th Bandpass-Filter(BPF) design procedure. Side walls and poles inside the waveguide are realized by placing two series array of via and tuning the via diameters. The each length of x, y, and z axes is reduced in proportion to root square of employed substrate dielectric constant and, especially, the length of z-axis can be more reduced due to the characteristics of e manufacturing cost can be reduced considerably. Finally, when using multi-layer process like low temperature cofired ceramic(LTCC) for small-sized module, it is one of advantages to use only one layer for the filter fabrication. To evaluate the validity of this novel technique, order-3 Chebyshev BPF centered at 40 GHz-band with a 2.5% Fractional Bandwidth(FBW) was used. The employed substrate has relative dielectric constant of 2.2 and thickness of 10 mils of Rogers RT/Duroid 5880. According to design and measurement results, a good performance of insertion loss of 2 dB and return loss of -30 dB is achieved at full input/output ports.

Multiplexed Cassegrain Reflector Antenna for Simultaneous Generation of Three Orbital Angular Momentum (OAM) Modes

A multiplexed Cassegrain reflector antenna with a 2 × 2 open-ended rectangular waveguide (OERW) matrix feed and an orbital angular momentum (OAM) mode mux is proposed for the simultaneous generation of three OAM modes (l = 0, ±1). The OAM mode mux (OMM) was designed using sequential combinations of quadrature hybrids, crossovers, and phase shifters to multiplex and demultiplex three OAM modes at the same time. The 2 × 2 OERW matrix feed and the OMM were separately measured and their performances were verified according to proposed theories. A near-field antenna measurement for a multiplexed Cassegrain reflector antenna was conducted to obtain the far-field magnitude and phase patterns around polar elevation angle θ and azimuthal angle ϕ, thus confirming that our antenna can produce three OAM modes simultaneously. We also measured the communication link characteristics of two identical multiplexed antennas. The measurement results show that the channel isolation of three OAM modes is more than 12.7 [dB] and 17 [dB] for fixed and compensated receiver positions, respectively, indicating that the proposed antenna system can be used for independent communication links with the same frequency and polarisation.

Design of a novel switched four beam array antenna for millimeter wave

Phased array system is used to scan an antenna beam to given angles in space. It consists of multiple stationary antenna elements, which are fed coherently, and uses variable phase shifter at each element. The phase shifter is one of the main parts of phased array antennas but it causes loss and complexity is making it. Inevitably, recent demands for highly flexible array control have highlighted the feed network offered by digital control such as, butler matrix for less complexity and loss. The butler matrix makes the orthogonal sets of beams with uniform aperture illumination using switches. But it needs four 90deg hybrids and two crossovers to make a four beam array antenna. These 90deg hybrids and crossovers worsen not only the antenna phase characteristics and operating bandwidth but also the system complexity. We propose a simple feed network for a four beam array antenna with just one 90deg hybrid, two switches, and delay lines. The merit of the proposed antenna is less complexity, in comparison with four beam butler matrix and easy fabrication due to planar structure.

The reflection and transmission characteristics of the waveguides with step discontinuities in millimeter wave

In this paper, mode transitions inside the waveguides with step discontinuities are studied. These transitions are applied to design the corrugated horn antenna directly connected with band pass filter (BPF) in millimeter wave regime. The used rectangular waveguide at the input port is a WR-22 standard waveguide for the frequencies from 40.5 GHz to 43.5 GHz. The RF system used for transmitter and receiver requires wide beam width and wide bandwidth characteristics for coverage and return loss, respectively. Also the antenna needs the high front-to-ratio in radiation pattern.