In-Bok Yom

A dual-passband filter of canonical structure for satellite applications

Due to the complex arrangement of frequency plans and spatial coverages in modern satellite communication systems, channels that are noncontiguous in frequency may be amplified by a single power amplifier and transmitted to the ground through one beam. In this letter, a dual-mode canonical filter with dual-passband is presented. The filter adopts dual-mode technique for mass and volume reduction. Canonical structure is adopted for maximum zero realization. To validate the design technique, a six-pole dual-mode dual-passband filter of canonical structure for Ka-band (30/20GHz) satellite transponder is realized. The measured frequency response of the filter shows good agreement with the computed one.

A design of K-band predistortion linearizer using reflective Schottky diode for satellite TWTAs

In this paper, a new predistortion method to reduce nonlinearity of a traveling wave tube amplifiers (TWTAs) is proposed. Nonlinear transfer characteristics of TWTA are analyzed using a carrier complex power series (CCPS). An inverse complex power series of a predistortion linearizer to linearize TWTA are also proposed. The inverse nonlinear distortion characteristics of predistorter can be realized with reflective structure that is composed of Schottky diode and resistor-terminated transmission line. The AM-to-AM and the AM-to-PM characteristics of TWTA on K-band were improved from -5.8 dB and -37.3/spl deg/ to 0.8 dB and 6.7/spl deg/ by proposed predistortion linearizer, respectively.

Ultra broadband DC to 40 GHz 5-bit pHEMT MMIC digital attenuator

A broadband, DC to 40 GHz 5-bit MMIC digital attenuator has been developed. The attenuator has been fabricated with 0.15 /spl mu/m GaAs pHEMT process. This attenuator has 1 dB resolution and 23 dB dynamic range. High attenuation accuracy has been achieved over all attenuation range and full 40 GHz bandwidth with the reference state insertion loss of less than 6 dB at 20 GHz. The input and output return losses of the attenuator are better than 14 dB over all attenuation states and frequencies.

An Active IF Balun for a Doubly Balanced Resistive Mixer

In this letter, we present a wideband active intermediate frequency (IF) balun for a doubly balanced resistive mixer implemented using a 0.5 mum GaAs pHEMT process. The 0.3 times 0.5 mm2 IF balun was realized through a DC-coupled differential amplifier in order to extend IF frequency of the mixer to DC. The measured amplitude and phase imbalances were less than 1 dB and 5deg, respectively, from DC to 7 GHz. The output third order intercept (OIP3) and P1 dB of the IF balun were 18 dBm and 6 dBm, respectively at 1 GHz. The mixer with the IF balun is 1.7 times 1.8 mm2 in size, has a conversion loss of 2 to 8 dB from 8 to 20 GHz RF frequency at a fixed IF of 1 kHz, which proves the mixer operates successfully at an IF frequency close to DC. The measured OIP3 were +10 to +15 dBm over the operating frequency with a DC power consumption of 370 mW.

A Ka-band multilayer LTCC 4-pole bandpass filter using dual-mode cavity resonators

This paper proposes a Ka-band 4-pole bandpass filter that uses dual-mode substrate integrated cavity resonator in a multilayer low-temperature co-fired ceramic (LTCC) structure. Circular-shaped dual-mode cavity resonator comprises metallic via arrays in substrate layer, a coupling via in the cavity, and external input and output feeding slots. Size of cavity and feeding slots determine the resonant frequency and quality factor of the resonator. The position of coupling via can control the coupling amount between two degenerate modes in a single cavity structure. Two dual-mode cavities are vertically laminated for fourth-order filter. Cross-shaped slot is used for coupling between the two laminated dual-mode cavity resonators. The cross-shaped slot can cause a coupling between non-adjacent resonators. Therefore the filter can have quasi-elliptic frequency response and high frequency selectivity. Example filter at Ka-band is designed and presented to demonstrate the validity of the new proposed structure.

Novel low-pass filter for broad-band spurious suppression

Novel microstrip-type low-pass filters are proposed to effectively suppress spurious response in stop-band. The proposed low-pass filter employs an open stub microstrip inserted by thin or thick film resistors in the place of a conventional open stub microstrip. The proposed low-pass filters was shown to suppress the spurious response by more than 20/spl sim/40 dB compared with conventional microstrip low-pass filters.

High Performance Vertical Transition from DC to 70 GHz for System-on-Package Applications

High performance vertical transition from DC to 70 GHz was proposed for system-on-package (SoP) applications. The trough line, slab line and shielded multilayer coplanar waveguides were employed to minimize the radiation loss, crosstalk and discontinuity of a conventional via vertical transition. The half square via pad was used in order to prevent unwanted coupling between the transmission lines of the vertical transition. The proposed vertical transition was made using a LTCC process. The manufactured single vertical transition showed a low insertion loss less than 0.7 dB and a reflection loss below -13 dB in the frequency range of DC to 70 GHz.

V-band MMIC low-noise amplifier design based on distributed active device model

A V-band two stage MMIC low-noise amplifier using 0.15 /spl mu/m pHEMT based on a distributed active device model has been designed. This model is successful in constructing the equivalent circuit of HEMT that cannot be scaled from a standard HEMT model. An MMIC amplifier based on the distributed model and careful EM simulation exhibits a maximum gain of 9.6 dB and a minimum noise figure of 3.6 dB at 61 GHz. This results indicate that the distributed HEMT model is effective for the design V-band MMIC low noise amplifiers.

Simultaneous reduction of amplitude and group-delay variation of input demultiplexer for Ku band satellite transponder

In this paper, design and realization of input demultiplexer(IMUX) for Ku band satellite transponder is described. Circulator chain structure has been used for demultiplexing each channel. Each channel consists of channel filter and external equalizer. External equalizers are designed to reduce the group delay variation and amplitude variation of channel filters simultaneously. Dual-mode technique is adopted for reducing the mass and volume of both the channel filters and external equalizers. Channel filters are designed to have 8-pole elliptic response and equalizers to be of 2-pole reflection-type. For good temperature stability characteristics, INVAR material is used for cavities, irises, and tuning srews of channel filters and external equalizers. The frequency drift has been taken into consideration in design procedure and measured by thermal test. Input demultiplexer is shown to be suitable for Ku band satellite transponder.

Development of a receiver downconverter module for Ka-band satellite payload

This paper describes the design and the test results of the receiver-downconverter module for a Ka-band Satellite Payload. The developed module has the low noise amplification in front stage and frequency down conversion which translates from 30.6 GHz - 31.0 GHz to 20.8 GHz - 21.2 GHz.. It has been fabricated and tested by the qualified satellite component manufacturing process and it shows the best performance of the receiver-downconverter modules operating at Ka-band frequency up to date. The module has the performance of 1.9 dB of NF, 55 dB of Gain, and 57 dBc of C/13 for the two-tone signals of -59 dBm input power, respectively, at ambient temperature. It is a small and light module with the size of 93 mm /spl times/ 84 mm /spl times/ 26 mm and the weight of 240 g.