1. Field of the Invention
The present invention relates to a phase inverter, and more particularly, to a microstrip phase inverter that directly inverts a phase without a converter for converting a line which is required when a conventional phase inverter is applied to a microstrip line.
2. Description of the Related Art
A general method for changing the phase of a signal transmitted in a microwave band is to adjust the length of a transmission line. For example, when the length of the transmission line is increased by ½ wavelength, the phase of a signal is delayed by 180 degrees, that is, the phase of the signal is inverted. However, when the length of the transmission line is increased to invert the phase of a signal, the volume of the entire system is inevitably increased.
Therefore, when a phase inverter is used as a device which changes the phase of an input signal by 180 degrees while maintaining the size of the input signal, the phase of the input signal may be changed by a system having a relatively small size. Such a phase inverter may be applied to a 180-degree hybrid coupler, a branch line coupler, a band-pass filter and the like in a microwave band, thereby reducing the size of the systems. Furthermore, when the length of the systems is reduced, a phase variation with respect to frequency decreases to thereby increase a bandwidth.
Similarly, in the coplanar-line phase converter of
However, a microstrip line includes a signal line, a ground line, and a dielectric substance interposed therebetween. The ground line is disposed to correspond to the signal line, and implemented as a ground substrate. Such a microstrip line may be applied to a microwave passive element. In order to invert the phase of a signal in the microstrip line, the conventional microwave passive element requires a separate device to convert the microstrip line into a parallel line. Therefore, the volume of the conventional microwave passive element is inevitably increased.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a microstrip phase inverter that directly inverts the phase of a signal of a microstrip line without an additional line converter.
In order to achieve the above object, according to one aspect of the present invention, there is provided a microstrip phase inverter including: a ground substrate having a slot formed therein; a dielectric layer formed over the ground substrate; a first microstrip line connected to a signal line of a first port and stacked and extended on the top surface of the dielectric layer at one side thereof; a second microstrip line facing the first microstrip line so as to deviate from the first microstrip line, connected to a signal line of a second port, and stacked and extended on the top surface of the dielectric layer at the other side thereof; and first and second via pins connected between one ends of the extended first and second microstrip lines and the ground substrate and configured to transmit first and second currents. The slot is formed in the ground substrate such that the first and second currents flowing in the ground substrate through the first and second via pins are separated from each other so as to form electrical fields with the second and first microstrip lines, respectively.
The slot may be formed in the ground substrate so as to be connected along a direction crossing the first and second microstrip lines and a direction crossing the space between the first and second via pins, except portions connected to the first and second via pins.
The length of the slot may be set to a value at which resonance occurs at the frequency of signals transmitted from the first and second microstrip lines.
The length of the slot may be 0.4 to 0.8 times than the wavelength of signals transmitted to the first and second microstrip lines.
The slot may be formed in a zigzag shape. The slot may have a width of 0.05 mm to 0.5 mm.
The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description taken in conjunction with the drawings, in which:
Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.
The microstrip phase converter includes a ground substrate 200, a slot 202, and a dielectric layer 204. The ground substrate 200 is configured to transmit a signal. The slot 202 is configured to block a signal flow in a ground substrate. The dielectric layer 204 is stacked over the ground substrate 200. Furthermore, the microstrip phase converter of
The first and second via pins 210 and 212 are connected to the ground substrate 200 and extended terminals of the first and second microstrip lines 206 and 208, respectively, like the conventional phase inverter. The first and second via pins 210 and 212 serve to pass currents flowing in the microstrip lines 206 and 208 to the ground substrate 200 which is divided by the slot 202 to block a signal.
The slot 202 is formed in the ground substrate 200 so as to be connected along a direction crossing the first and second microstrip lines 206 and 208 and a direction crossing a space between the first and second via pins 210 and 212, except for portions connected to the first and second via pins 210 and 212. Accordingly, the slot 202 blocks a signal flow between the first and second via pins 210 and 212. Therefore, when the slot 202 resonates at the frequency of a transmitted signal, signal currents flowing from ports 1 and 2 to the first and second microstrip lines 206 and 208 form an electric field between the second and first microstrip lines 208 and 206 and the ground substrate 200 through the via pins 210 and 212 separated from each other with the slot 202 set to the boundary therebetween. As a result, the signal currents are passed to the divided parts of the ground substrate 200, respectively. Accordingly, the phase inversion may be achieved at a signal frequency where the slot 202 resonates, without a signal loss.
In the embodiment of the present invention, signals transmitted through the slot 202 may be radiated, and signals between the two signal lines may not be normally transmitted. Therefore, the design of the slot 202 is important. When the slot 202 has a large width or is formed in a straight line, radiation occurs through the slot. Therefore, the slot 202 may be formed in a zigzag shape to reduce the effect of radiation, and may have a small width of 0.05 mm to 0.5 mm.
The strip phase inverter according to the embodiment of the present invention was manufactured by using a substrate having a dielectric constant of 2.2 and a thickness of 0.508 mm. The widths of the first and second microstrip lines 206 and 208 were set to 1.55 mm such that the impedance becomes 50Ω, and the diameters of the via pins 210 and 212 were set to 0.3 mm. The longitudinal length L of the ground substrate 200 was set to 30 mm, the slot 202 was designed to resonate at 2.34 GHz, and the length of the slot 202 was set to 86 mm. In the slot 202, resonance generally occurs at a length corresponding to a half wavelength. However, when a zigzag shape is applied to the slot 202, resonance occurs at a larger length. Therefore, the slot is set to have a length slightly larger than the half wavelength.
At a resonant frequency of 2.34 GHz, a maximum transmission coefficient S21 of the phase inverter is 0.39 dB, and a phase difference is 193°. Furthermore, a transmission coefficient of the microstrip line at the same frequency is −0.23 dB. In an ideal case, the phase difference is 180°. However, an additional phase delay of 13° occurs due to the via pins. Accordingly, as the length of the transmission line including the phase inverter is slightly reduced, the phase difference may be corrected to become 180°.
Furthermore, as the phase inverter according to the embodiment of the present invention is applied, the transmission coefficient was decreased to −0.16 dB. However, the value may be sufficiently accepted. Furthermore, when the maximum transmission coefficient of the phase inverter falls within a difference of 0.3 dB and the phase difference falls within ±5°, the bandwidth of the phase inverter corresponds 11%. These values may be sufficiently applied to a phase inverter which is integrated in a microwave passive element.
The microstrip phase inverter according to the embodiment of the present invention does not require an additional device to convert a microstrip line. Furthermore, since the microstrip line is used to directly invert the phase of a transmitted signal, the phase of the signal may be converted by a small-size system.
The embodiment of the present invention may be applied to a microstrip phase inverter which directly inverts the phase of a signal without a converter that changes a transmission line required when a conventional phase inverter is applied to the microstrip transmission line.
Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and the spirit of the invention as disclosed in the accompanying claims.
Number | Date | Country | Kind |
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10-2009-0114065 | Nov 2009 | KR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/KR10/08170 | 11/19/2010 | WO | 00 | 4/3/2013 |