Abstract: Provided is a microwave filter system having a feedback structure. The microwave filter system may include an input hybrid coupler configured to output first output signals having a phase difference with respect to an input signal; filters disposed to be in parallel with an output end of the input hybrid coupler, and configured to filter the first output signals; and an output hybrid coupler configured to output second output signals having a phase difference with respect to each of signals filtered through the filters. An output signal of the output hybrid coupler is applied to an input end of the input hybrid coupler along a feedback path.

Abstract: Provided is a microwave filter system having a feedback structure. The microwave filter system may include an input hybrid coupler configured to output first output signals having a phase difference with respect to an input signal; filters disposed to be in parallel with an output end of the input hybrid coupler, and configured to filter the first output signals; and an output hybrid coupler configured to output second output signals having a phase difference with respect to each of signals filtered through the filters. An output signal of the output hybrid coupler is applied to an input end of the input hybrid coupler along a feedback path.

Abstract: The present invention provides a multi-port amplifier which adopts a pair of SP4T switches and a pair of hybrid couplers in order to flexibly adjust an amplification mode. By using the proposed invention, the limited system flexibility and reconfigurability due to fixed input and output relations are overcome regardless of a component failure in a system. Moreover, signal amplification based on effective signal distribution and combination can be consistently performed according to various port configurations by different switching modes. Thus, the overall practicality of outputs comparing to the conventional multi-port amplifier can be effectively increased within an available lifespan of the system.

Abstract: Disclosed is an apparatus and a method for multiport amplification configured to amplify a signal input to a multi-input port and output the amplified signal to a multi-output port in order to normally transmit/receive a signal in a communication system. The apparatus and the method are configured to: amplify an input signal input through a multi-input port, detect a phase error and an amplitude error of the input signal, and then calculate a phase error value and an amplitude error value of the input signal; correct the phase error and the amplitude error of the input signal through the phase error value and the amplitude error value of the input signal; and then amplify the input signal of which the phase error and the amplitude error are corrected, and output the input signal to a multi-output port.

Abstract: Provided is a phase shifter for shifting a phase of a signal the phase shifter including an input unit to split an input signal into a plurality of signals having different phases, a connection unit to change at least one of magnitudes and phases of the plurality of signals, apply the changed plurality of signals to a plurality of loads, and receive a plurality of return signals generated when the applied signals are returned by the plurality of loads, and an output unit to generate an output signal having a predetermined phase difference from the input signal based on the return signals.

Abstract: Disclosed is an apparatus and a method for multiport amplification configured to amplify a signal input to a multi-input port and output the amplified signal to a multi-output port in order to normally transmit/receive a signal in a communication system. The apparatus and the method are configured to: amplify an input signal input through a multi-input port, detect a phase error and an amplitude error of the input signal, and then calculate a phase error value and an amplitude error value of the input signal; correct the phase error and the amplitude error of the input signal through the phase error value and the amplitude error value of the input signal; and then amplify the input signal of which the phase error and the amplitude error are corrected, and output the input signal to a multi-output port.

Abstract: Disclosed herein is the structure of a Square Quadrifilar Helical antenna (S-QHA). The structure of the S-QHA includes a square column, four radiation elements, and a feed network. The four radiation elements are formed on the square column. The feed network is disposed at the top or bottom of the square column, and feeds signals to the radiation elements at a phase difference of 90 degrees in a clockwise or counterclockwise direction. As a result, the S-QHA according to the present invention can receive circularly polarized signals.

Abstract: The present invention relates, in general, to a Radio Frequency Identification (RFID) system for reading or recording RFID tag information using radio frequencies and, more particularly, to an intelligent RFID system for low-powered reader-tag communication, which includes an RF shower system (370) that radiates a high power electromagnetic wave in a high frequency band to activate the passive tags having no batteries and that has predetermined communication means for reading information from a plurality of passive tags existing in a radiation zone having a predetermined size, storing the read tag information, and providing the stored tag information when a request is received from an RFID reader (310).

Abstract: The present invention relates to a lowpass filter for effectively suppress a spurious in stop-band. The lowpass filter includes an input port microstrip element; an output port microstrip element; a first open-ended microstrip element; a second open-ended microstrip element; a first connector microstrip element; and, a second connector microstrip element. The each open-ended microstrips of the present invention is composed of distributed elements and distributed resistances connected each others in series and operated as a capacity, has a large impedance of the microstrip by low influence of a resistance in case of a low frequency, and has a small impedance of the microstrip by high influence of a resistance value in case of a high frequency. The present invention can effectively suppress the spurious characteristic, which is a disadvantage of the conventional lowpass filter composed of transmission lines at the RF band or the microwave band, by inserting resistance elements in open-ended microstrips.

Abstract: The present invention relates to a lowpass filter for effectively suppress a spurious in stop-band. The lowpass filter includes an input port microstrip element; an output port microstrip element; a first open-ended microstrip element; a second open-ended microstrip element; a first connector microstrip element; and, a second connector microstrip element. The each open-ended microstrips of the present invention is composed of distributed elements and distributed resistances connected each others in series and operated as a capacity, has a large impedance of the microstrip by low influence of a resistance in case of a low frequency, and has a small impedance of the microstrip by high influence of a resistance value in case of a high frequency. The present invention can effectively suppress the spurious characteristic, which is a disadvantage of the conventional lowpass filter composed of transmission lines at the RF band or the microwave band, by inserting resistance elements in open-ended microstrips.