Abstract: A line-waveguide converter includes a backside electrode disposed on a first face of a dielectric substrate, a waveguide attached to a second face of the dielectric substrate opposite the first face and having electrical conduction to the backside electrode, and multiple electrodes disposed inside the waveguide on the second face. The electrodes are identical in shape and size, and the intervals between adjoining ones of the electrodes are identical. At least one of the electrodes can be fed with power from a line.

Abstract: An RF impedance-matching transformer for matching the output impedance of an RF amplifier to the discharge of a gas-discharge laser includes upper and lower dielectric plates arranged face-to-face and bonded together. A primary U-shaped strip winding is embedded in the bonded surface of one of the dielectric plates. A secondary strip-winding is formed on an exposed surface of the upper dielectric plates. A ground-plane electrode formed on an exposed surface of the lower dielectric plate. An electrical connector connects one end of the secondary strip-winding to the ground-plane electrode via a via-hole extending through the dielectric plates. The other end of the secondary strip-winding can be connected to the laser.

Abstract: The present invention is directed to a balun that includes a first coupler structure having a first port of a balanced port pair and an unbalanced port. A second coupler structure includes a second port of the balanced port pair. The second coupler port structure being connected to the first coupler structure such that the second port of the balanced port pair is DC isolated from the first port of the balanced port pair without decoupling components.

Abstract: A balun may include series-coupled balanced-signal lines. In some examples, a balun may include a first transmission line having a first unbalanced signal port on which an unbalanced signal may exist relative to circuit ground; a second transmission line having a first balanced-signal port may be connected in series with a third transmission line having a second balanced-signal port. In some examples, a fourth transmission line may be coupled to the first transmission line and have a third balanced-signal port. A fifth transmission line may be connected in series with the fourth transmission line and have a fourth balanced-signal port. In some examples, the transmission lines may be coaxial. Balanced signals may exist between the first and second balanced-signal ports and between the third and fourth balanced-signal ports. Series-connected coaxial transmission lines may be formed of a single coaxial line with a gap in the outer conductor separating the two coaxial transmission lines.

Abstract: A balun is provided in which first balanced line and second balanced line are disposed on a nearly the same plane, first unbalanced line is disposed above first balanced line at a predetermined distance from first balanced line, second unbalanced line is disposed below second balanced line at the predetermined distance from second balanced line. With this configuration, the distance between first unbalanced line and second unbalanced line can be increased thereby greatly suppressing mutual cancellation of a current flowing in first unbalanced line and a current flowing in second unbalanced line.

Abstract: A balun that includes a first conductor, a second conductor, and a third conductor. The first conductor has a first length. The first conductor also has a first end connected to a first balanced power amplifier output port. The second conductor has substantially the same first length. The second conductor also includes a first end connected to a second balanced power amplifier output port and a second end connected to a second end of the first conductor. The third conductor has substantially the same first length. The third conductor has a first end connected to an antenna port and a second end connected to a ground potential.

Abstract: A compact single-to-balanced bandpass filter is proposed in this invention. Firstly, a pre-design circuit is presented, which is composed of an inductive coupled-line (ICL) bandpass filter and an out-of-phase capacitive coupled-line (CCL) bandpass filter. A novel compact circuit with three coupled lines configuration, derived from the pre-design circuit, is then proposed for miniaturizing the single-to-balanced bandpass filter. In order to verify the feasibility of the proposed structure, a 2.4 GHz multilayer ceramic chip type single-to-balanced bandpass filter with size of 2.0 mm×1.2 mm×0.7 mm is developed. The filter is designed by using circuit simulation as well as full-wave electromagnetic (EM) simulation softwares, and fabricated by the use of low-temperature co-fire ceramic (LTCC) technology. The measured results agree quite well with the simulated. According to the measurement results, the maximum insertion loss is 1.

Abstract: A coaxial waveguide converter circuit is provided for converting an input/output coaxial section of a traveling-wave tube to a waveguide. The circuit comprises a waveguide matching part for connecting an inner conductor of the coaxial section extending into the waveguide to a wall of the waveguide. The waveguide matching part includes a fitting hole for fitting the inner conductor thereinto, and a plurality of cantilever supports which define the fitting hole at leading end portions thereof. The leading end portions of the plurality of cantilever supports defining the fitting hole are uniformly kept in close contact with a peripheral surface of the inner conductor.

Abstract: A first dielectric substrate an electromagnetically coupling conductor for a coplanar strip transmission line disposed on a surface close to a dielectric layer, a second dielectric substrate has a grounding conductor disposed on a surface close to the dielectric layer, the grounding conductor has an electromagnetic coupling slot formed in a substantially H-character shape therein, and the second dielectric substrate has an electromagnetically coupling conductor for a microstrip transmission line disposed on a surface remote from the dielectric layer so as to pass over or under the connecting slot.

Abstract: A laminated balun transformer that may be used for lines having various impedances includes a first magnetic substrate, a laminated body, a second magnetic substrate, and external electrodes. The laminated body includes a first transformer, a second transformer, and an insulator that covers the first and second transformers. The first transformer includes a primary coil and a secondary coil. The second transformer includes a primary coil and a secondary coil. The line width of the primary coil of the first transformer is set so as to decrease from the side of the internal electrode towards the side of the internal electrode. The line width of the secondary coil of the second transformer is also set so as to decrease from the side of the internal electrode towards the side of the internal electrode.

Abstract: The present antenna system includes a balun for coupling an antenna to a feed line. The balun has at least two transmission line transformers, such that the transmission line transformers are coupled in parallel at their inputs with the feedline, and coupled in series at their outputs with the antenna. At least one of the transmission line transformers maintained by the balun is fabricated so that it has reduced power dissipation properties, and reduced electromagnetic stress handling properties with respect to the other transmission line transformers. Such considerations reduce fabrication time, waste of material, and the cost of the balun.

Abstract: A three dimensional (3D) monolithic integrated circuit (MMIC) balun and methods of making the same are provided. A primary spiral winding is spaced apart from a secondary primary winding by a gap in a substantially aligned stacked configuration forming a balun. The gap medium can be a low dielectric constant material if employing a multi-metal process or air if employing a wafer level packaging process.

Abstract: A probe device for testing a semiconductor chip includes a substrate and a balun formed on the substrate. The balun includes first and second differential ports and a single-ended port. The probe device includes first and second probe tips respectively coupled to the first and second differential ports.

Abstract: A splitter circuit for use in a CATV network. A signal input communicates with a first balun to supply two signal outputs, wherein the first balun is impedance matched to the impedance of the input using two or more additional baluns in parallel with each other. The additional baluns are transmission line baluns in parallel or series with resistive and/or capacitive and/or inductive components.

Abstract: A balanced-unbalanced transformation device includes a plate-like dielectric substrate having a ground electrode and a plurality of major surface electrodes formed thereon. Two of the major surface electrodes are connected to the ground electrode via short-circuit side surface electrodes so as to form ¼ wavelength resonator transmission lines. A third major surface electrode is disposed between the two major surface electrodes and has either end open so as to form a ½ wavelength resonator transmission line. A balancing characteristic adjustment side surface electrode is provided on a side surface of the dielectric substrate. By adjusting a capacitance formed between the balancing characteristic adjustment side surface electrode and the third major surface electrode, a phase balance between two balanced signals is set to a desired value.

Abstract: A dielectric substrate includes a filter unit, a non-balance/balance conversion unit, and a connection unit for electrically connecting the filter unit to the non-balance/balance conversion unit which are formed in the dielectric substrate. A first resonator has an electrode formed on the main surface of a fourth dielectric layer and a via hole penetrating through a first to a third dielectric layers and connecting the electrode to a grounding electrode. A second resonator has an electrode formed on the main surface of the fourth dielectric layer and a via hole penetrating through the first to the third dielectric layers and connecting the electrode to the grounding electrode.

Abstract: A wireless communication module includes a laminated substrate where a plurality of dielectric sheets are laminated, a band pass filter, a balun circuit, and first and second matching circuits. The band pass filter is formed in the laminated substrate. The balun circuit is formed in the laminated substrate, and includes an unbalanced element having one end connected to the band pass filter. The first and second matching circuits are formed in the laminated substrate, and each of them is connected to one end of each of balanced elements of the balun circuit. Herein, at least one of the band pass filter, the balun circuit, the first matching circuit, and the second matching circuit is formed between the dielectric sheets of the laminated substrate using a distributed element.

Abstract: A pair of balanced terminals is connected to a pair of interdigital-coupled quarter-wave resonators in an electronic device. This electronic device has a first resonance mode that resonates at a first resonance frequency f1 higher than a resonance frequency f0 in each of the pair of quarter-wave resonators when establishing no interdigital-coupling, and a second resonance mode that resonates at a second resonance frequency f2 lower than the resonance frequency f0. The second resonance frequency f2 of a low frequency is set as an operating frequency. This provides an electronic device and a filter that facilitate miniaturization and enable a balanced signal to be transmitted with superior balance characteristics.

Abstract: A waveguide/strip line converter includes a waveguide and a multilayer substrate. A second end of the multilayer substrate is fixed to an opening of the waveguide. The multilayer substrate includes a plurality of dielectric layers to form a plurality of substrate faces. A top substrate face includes a strip line and a first short-circuiting metal pattern. First and second intermediate substrate faces include second and third short-circuiting metal patterns with openings, respectively. A matching element forming substrate face includes a matching element, which is electromagnetically coupled with the strip line. A waveguide passage extends through the openings between the strip line and the matching element. A cross sectional area of the opening is larger than that of the opening.

Abstract: A balanced filter includes: a filter that has at least one unbalanced signal terminal; a balun that is a lumped parameter balun that inputs or outputs signals with different phases generated based on a signal input or output from the unbalanced signal terminal of the filter, the balun being formed with an integrated passive device; and a mounting unit in which the filter and the balun are flip-chip mounted.

Abstract: A high frequency filter incorporates: an unbalanced input/output terminal; two balanced input/output terminals; two resonators respectively provided between the unbalanced input/output terminal and the two balanced input/output terminals; and a layered substrate for integrating components of the high frequency filter. The two resonators are inductively coupled to each other, and are also capacitively coupled to each other through two capacitors. Each of the two capacitors is formed using a pair of first and second electrodes and a dielectric layer. The first electrode is connected to one of the resonators via a through hole. The second electrode is connected to the other of the resonators and opposed to the first electrode forming the pair with the second electrode, the dielectric layer being disposed between the second electrode and the first electrode.

Abstract: A transmission line transformer is disclosed. The transformer improves efficiency and a dynamic range of a power amplifier. The transformer is formed to have a plurality of load impedances as the primary side of the transmission line transformer is separated to form a plurality of primary transmission lines with parasitic components which are different from each other. The transformer is used as an impedance matching circuit of the power amplifier requiring a plurality of load impedances.

Abstract: A broadband microstrip balun and a method of manufacturing the same are provided. In the balun, transmission lines formed at different layers partially overlap in parallel with each other, and a common ground having a predetermined opening is inserted between the transmission lines. Thus, an unbalanced signal may be converted into a balanced signal in a broad frequency band using resonance of a common ground plate with the opening and a Bethe hall effect. Also, impedance matching is readily enabled, thereby reducing a parasitic element.

Abstract: A pseudo-Marchand balun, compound balun and tunable multi-resonant coaxial balun, and NMR probes employing each such balun, and a fine balance and impedance adjustment module and a multi-layer transmission line for use in such NMR probes.

Abstract: An antenna of the present invention includes a coaxial cable, antenna elements (3a and 3b), and an unbalanced/balanced converter. The unbalanced/balanced converter has a high-pass circuit provided between an input terminal port1 and an output terminal port2 and a low-pass circuit provided between the input terminal port1 and an output terminal port3. Moreover, the high-pass circuit rejects frequencies within a VHF band, and the high-pass circuit and the low-pass circuit both pass frequencies within a UHF band. In response to a signal, inputted to the input terminal port1, which falls within the UHF band, the high-pass circuit and the low-pass circuit output signals that are inverted in phase and equal in amplitude with respect to each other. Therefore, the antenna has high transmission and reception sensitivity in a wide frequency range, i.e., in the VHF and UHF bands. This makes it possible to provide an antenna having high transmission and reception sensitivity in a wide frequency range.

Abstract: A dual band balun filter that includes a first coupled-line section pair provided with a first terminal; a second coupled-line section pair configured to be connected to the first coupled-line section pair, a third coupled-line section pair, and a fourth coupled-line section pair, respectively, and the fourth coupled-line section pair is provided with a second terminal; the third coupled-line section pair is provided with a transmission line and is connected to a fifth coupled-line section pair that is provided with a third terminal; and each of the first to fifth coupled-line section pairs is formed with partial coupled stepped impedance resonators (SIRs).

Abstract: In order to realize with a low loss a hybrid structure in which an NRD guide is used for a transmission part and a microstrip line is used for a circuit element loading part, the present device includes: a dielectric waveguide (1) which is sandwiched between parallel conductor plates and has a gap which is less than a ½ wavelength; a microstrip line (4) which is provided on a side surface of a metal rod (3) opposite to the dielectric waveguide (1), the metal rod (3) being adjacently arranged in parallel with the dielectric waveguide (1); and a coaxial line (5) which pierces the metal rod (3) and connects the dielectric waveguide (1) with the microstrip line (4).

Abstract: A balun includes a first transforming part (30) and a second transforming part (40). The first transforming part includes a first coupled line (32), a first transmission line (34), a second transmission line (36), and a first capacitor (C1). The first transmission line includes a first balanced port (2). The second transmission line includes a second balanced port (3). The first capacitor connects the first balanced port and the second balanced port. The second transforming part includes a second coupled line (42), a third transmission line (44), a first line node (48), a second capacitor (C2), a fourth transmission line (46), a second line node (49), and a third capacitor (C3). The third transmission line includes an unbalanced port (1). The second capacitor connects the third transmission line and the first line node. The third capacitor connects the fourth transmission line and the second line node.

Abstract: The present invention relates to the field of electronic devices known as baluns. It concerns an active balun which is broadband and reciprocal. Embodiments of the invention integrate an active splitter balun with an active combiner balun so as to form three transmission lines. A first active coupling is provided between the first and second transmission lines and a second active coupling is provided between the first and third transmission lines. The active couplings are provided by means of amplifier cells distributed along the transmission lines. Embodiments of the invention have configurable means for polarizing the different amplifier cells so as to create a specific coupling direction between the various transmission lines. The device according to the invention can be applied in the field of broadband mixers which are used, notably, in radio transmission and reception circuits.

Abstract: A balun includes an input line for receiving an unbalanced signal, an output line for receiving the unbalanced signal from the input line and outputting a balanced signal, and a ground. The input line and the output line are formed in the same layer, and the ground is formed in a different layer from the input line and the output line. The ground has an opening so as to generate a potential difference between the first output line and the second output line. The ground is electrically connected to the input line.

Abstract: A line transition device that includes a waveguide and a microstrip line. The microstrip line is substantially orthogonal to an electromagnetic wave propagation direction in the waveguide. A choke groove crosses the microstrip line. A coupling conductor provided at a tip of the microstrip line is positioned at a terminal end of and inside the waveguide. A slit-like region where a ground conductor is not formed is substantially orthogonal to the electromagnetic wave propagation direction in the waveguide. A longitudinal length of the slit-like region is substantially equal to a quarter of the wavelength of electromagnetic waves. The slit-like region is provided such that it extends from an end of a ground conductor near a boundary between the coupling conductor and the microstrip line to reach the choke groove.

Abstract: A balun circuit includes a first CPW line 11, a second CPW line 12a, and a third CPW line 12b that serve as signal input/output ports; a first CPS line 14a that is a differential transmission line, the first CPS line 14a relaying the first CPW line 11 to the second CPW line 12a; a second CPS line 14b that is a differential transmission line, the second CPS line 14b relaying the first CPW line 11 to the third CPW line 12b; and at least one connection section that connects grounded conductors of each of the first CPW line 11, the second CPW line 12a, and the third CPW line 12b.

Abstract: A balun including a single-ended port, a differential port and first and second sets of coupled transmission line sections. Each set has three coupled transmission line sections. The signal carrying terminal of the single-ended port is connected to an inner end of a third coupled transmission line sections in one of the sets, and the terminals of the differential port are connected to a respective outer end of a respective first transmission line. The balun is fabricated in a multi-layer insulating substrate with the single-ended port located on an upper surface of the substrate and the differential port located on a lower surface of the substrate. The balun is suitable for connection to a chip antenna mounted on a common carrier substrate.

Abstract: Disclosed are a microstrip-type BALUN (BALance to UNbalance transformer), broadcast receiving apparatus using the same, and a method for forming the same. The BALUN includes a board and a microstrip line formed on the board for transforming an input unbalanced signal into a balanced signal. Since the microstrip-type BALUN is realized by a microstrip line which is a distributed constant line, the microstrip-type BALUN has an excellent performance even for high-frequency signals. Similarly, a broadcast receiving apparatus to which a microstrip-type BALUN is applied also has an excellent performance for high-frequency broadcasting signals.

Abstract: A balun circuit is provided that includes a first coupling line in which an unbalanced line thereof is connected to a first terminal and a balanced line thereof is electrically connected to a second terminal, a second coupling line in which an unbalanced line thereof is electrically connected to the unbalanced line of the first coupling line and a balanced line thereof is electrically connected to a third terminal, a first transmission path that is serially connected between the balanced line of the first coupling line and a ground potential, a second transmission path that is serially connected between the balanced line of the second coupling line and a ground potential, and a third transmission path that is serially connected between the unbalanced line of the first coupling line and the unbalanced line of the second coupling line.

Abstract: In general, in accordance with an exemplary aspect of the present invention, a low-loss interface for connecting an integrated circuit such as a monolithic microwave integrated circuit to an energy transmission device such as a waveguide is disclosed. In one exemplary embodiment, the interface comprises a coaxial structure such as a coaxial cable that directly connects the monolithic microwave integrated circuit to the waveguide to transmit energy such as microwave energy with minimal loss.

Abstract: A high frequency line-waveguide converter comprises a high frequency line including a dielectric layer, a line conductor disposed on an upper surface of the dielectric layer, and a ground conductor layer disposed on the same surface so as to surround one end of the line conductor, a slot formed in the ground conductor layer so as to be substantially orthogonal to the one end of the line conductor and coupled to the line conductor, a shield conductor part disposed on a side of or in an inside of the dielectric layer so as to surround the one end of the line conductor and the slot, and a waveguide disposed at the lower side of the dielectric layer so that an opening is made opposite to the one end of the line conductor and the slot, and electrically connected to the shield conductor part.

Abstract: A low frequency reject filter element is formed on a printed circuit board that utilizes the fact that power transmission in a waveguide is cut-off below a certain frequency. A quasi waveguide cavity is formed in printed circuit board using the top and bottom ground plane of the stripline circuit and using conductive via holes to form the side walls of the cavity. Waveguide cavity mode is launched from the input and output striplines by shorting them to ground. Transformers and matching via hole elements may be used to improve matching. The resulting filter is compact and is highly effective in suppressing low frequency transmissions.

Abstract: An apparatus and method relating to a rectangular waveguide cavity launch are disclosed that enable coupling an electromagnetic wave from the top surface of a waveguide distribution network formed into a conductive plate with the narrow wall of a rectangular waveguide facing the top of the conductive plate. A resonant cavity structure is formed into a conductive plate and coupled to a waveguide also formed into the plate, the resonant cavity structure having a cavity width wider than the narrow wall dimension of the waveguide. The resonant cavity structure includes a conductive block within it having a block width substantially equal to a difference between the cavity width of the resonant cavity structure and the narrow wall dimension. The cavity launch excites and rotates a dominant waveguide mode entering the structure such that the dominant waveguide mode enters the waveguide substantially parallel to the narrow wall dimension.

Abstract: The modification of the impedance ratio of a balun of four conductive windings formed in two metallization planes stacked by being interdigited and electrically in series two by two, by connecting a capacitor in series with the two windings defining the common mode of the balun.

Abstract: A balun is provided in which first balanced line and second balanced line are disposed on a nearly the same plane, first unbalanced line is disposed above first balanced line at a predetermined distance from first balanced line, second unbalanced line is disposed below second balanced line at the predetermined distance from second balanced line. With this configuration, the distance between first unbalanced line and second unbalanced line can be increased thereby greatly suppressing mutual cancellation of a current flowing in first unbalanced line and a current flowing in second unbalanced line.

Abstract: Electrical coupling apparatus providing transition between a high radio frequency waveguide and a perpendicularly oriented microstrip line without use of a shorting cap fixes an open end of the waveguide perpendicularly to a dielectric substrate. The microstrip line is carried on the substrate and couples through a hole in the waveguide wall to a microstrip patch on the substrate within the waveguide having a resonance with the waveguide encompassing a predetermined high radio frequency bandwidth of signals to be conducted by the apparatus. A plurality of parallel conducting members form a via fence aligned with the waveguide wall and extending through the substrate to electrically connect the waveguide to a planar ground conductor that covers the opposite side of the substrate, including the area under the open end of the waveguide.

Abstract: A surface mountable transformer integratable into a printed circuit board. In one aspect, the transformer comprises two broadside vertically coupled transmission lines. In another aspect, the transformer may comprise two broadside vertically partially coupled transmission lines. The layout of the transformer is adaptable for use in microwave modules where transformers are integrated into the printed circuit board and the active components are mounted in the cavity. The layout preferably requires only two signal areas. In addition, an aspect of the present invention allows the differential or unbalanced ports to lie on the same surface as the balanced port.

Abstract: The present invention comprises novel means and apparatus which provide both impedance matching of arbitrary impedances and transformation between single-ended, floating, and balanced circuits over very wide operating bandwidths with very low excess loss and very low phase and magnitude ripple in the pass band. The present invention can provide high-performance matching, for example from a 50-ohm single-ended system to a 100-ohm balanced system over a bandwidth of 10 kHz to 10 GHz with an excess loss of less than nominally 1 dB and a bandpass magnitude ripple of less than ±0.5 dB. The present invention also provides precision low-loss power division over very wide-bandwidth. The novel means, according to the present invention, can utilize commonly available materials and can be optimized for specific applications to tailor performance to specific needs and to simplify assembly and reduce cost.

Abstract: Provided is a broadband microstrip-waveguide transition apparatus operating in a millimeter waveband. The millimeter-wave band broadband microstrip-waveguide transition apparatus includes a slot for transferring an electromagnetic signal propagating along a microstrip line, a main patch positioned between the slot and a waveguide and resonating from the signal transferred from the slot, and a parasitic patch positioned between the main patch and the waveguide and resonating together with the main patch. According to the millimeter-wave band broadband microstrip-waveguide transition apparatus, it is possible to transfer a signal from the microstrip line to the waveguide, and to increase a resonance bandwidth to a broadband level.

Abstract: The present invention provides an RF module capable of converting electromagnetic waves in the TE mode to balanced electromagnetic waves in the TEM mode without adjustment and outputting the balanced electromagnetic waves while easily realizing miniaturization. The RF module includes: a waveguide (3) in which a half-wavelength TE mode resonator (2) is formed; an E plane coupling window (4) formed in a wall portion (3a) orthogonal to an H plane out of wall portions (3a) to (3e) constructing the TE mode resonator (2) in the waveguide (3); an output line (5a) provided at the edge on the side of the wall portion (3d) parallel with the H plane on the E plane coupling window (4), and magnetically coupled to electromagnetic waves in the TE mode resonator (2); and another output line (5b) provided at the edge on the side of the wall portion (3e) parallel with the H plane in the E plane coupling window (4), and magnetically coupled to the electromagnetic waves.

Abstract: Apparatus and methods are provided for constructing waveguide-to-transmission line transitions that provide broadband, high performance coupling of power at microwave and millimeter wave frequencies. More specifically, exemplary embodiments of the invention include wideband, low-loss and compact coplanar waveguide-to-rectangular waveguide transition structures and asymmetric coplanar stripline (or coplanar stripline)-to-rectangular waveguide transition structures that are particularly suitable for microwave and millimeter wave applications.

Abstract: A miniaturised half-wave balun comprises a single-ended I/O port comprising a first signal carrying terminal for connection to a source impedance and a differential I/O port comprising second and third signal carrying terminals for connection to a load impedance. First and second transmission line sections of equal length and characteristic impedance are connected together at a common end and at opposite ends to the second and third terminals. The first signal carrying terminal is coupled to the first transmission line section. The combined length of the first and second transmission line sections is substantially less than one half of the wavelength of an RF signal at the operating frequency. First and second loading shunt capacitors are connected to respective first and second transmission line sections. A shunt capacitive element is connected at the common end of the transmission line sections.

Abstract: An MMIC chip is disclosed that includes a planar substrate having a first surface and a second surface, a conductive layer having an opening on the first surface, a transmission line on the second surface, at least one conductor extending from the conductive layer to the second surface defining a waveguide around the opening, wherein the transmission line is connected to the at least one conductor such that a signal traveling along the transmission line is guided toward the opening in the first side by the at least one conductor.

Abstract: In a balun for mutually converting an unbalanced line for unbalanced input/output and a balanced line for balanced input/output, the unbalanced line and the balanced line are microstrip lines including a signal line arranged on one main surface of a substrate and a ground conductor arranged on the other main surface of the substrate. The balun further includes a slot line formed by a aperture line arranged in the ground conductor in the other main surface. The microstrip line as the unbalanced line includes one end portion used as an input/output end and the other end portion that traverses the slot line, electromagnetically couples to the slot line, and functions as an electric short-circuited end. The central portion of the microstrip line as the balanced line traverses the slot line and electromagnetically couples to the slot line. Both ends of this microstrip line serves as the input/output ends.