Showing papers on "Balun published in 2015"

Wideband Excitation Technology of ${\rm TE}_{20}$ Mode Substrate Integrated Waveguide (SIW) and Its Applications

Abstract: The higher order mode substrate integrated waveguide (SIW) has advantages in the applications, which are: 1) simplifying the structure with reduced fabrication cost and 2) enhancing the stability of performance by relaxed fabrication tolerance. In this paper, two wideband ${\rm TE}_{20}$ mode excitation structures are presented and investigated for the SIW. A slot along the mid line in the longitudinal direction of the SIW is employed to convert the electromagnetic field pattern between slotline and the ${\rm TE}_{20}$ mode SIW. The second structure is based on the slot aperture coupling and can realize wideband direct transition between the ${\rm TE}_{20}$ mode SIW and microstrip line. Both transitions have a simple and compact structure, as well as broadband characteristics. The wideband transition performance is demonstrated in this paper. As application examples of the transitions, two broadband substrate integrated baluns are presented and fabricated based on the ${\rm TE}_{20}$ mode excitation structures and ${\rm TE}_{20}$ mode characteristics. The 180 $^{\circ}$ out-of-phase and equal magnitude of the balun outputs in a wide frequency range can be achieved inherently. The balun based on the slotline excitation has a fractional bandwidth of 50.2%, from 7.3 to 12.2 GHz, with measured return loss, amplitude imbalance, and phase imbalance better than 10 and 0.45 dB and 3.8 $^{\circ}$ . The balun based on the aperture coupling excitation shows a fractional bandwidth of 50.3%, from 7 to 11.7 GHz, with measured return loss, insertion loss, amplitude imbalance, and phase imbalance better than 10, 1, and 0.27 dB and 2.4 $^{\circ}$ , respectively. Both baluns not only show good performance, but also demonstrate the existence of the ${\rm TE}_{20}$ mode in the SIW.

300 GHz Integrated Heterodyne Receiver and Transmitter With On-Chip Fundamental Local Oscillator and Mixers

Abstract: A 300 GHz integrated heterodyne receiver and transmitter for wideband communication and imaging applications have been developed in a 250 nm InP double-heterojunction bipolar transistor (DHBT) process. The receiver integrates a 300 GHz RF amplifier with a balun, a down-conversion mixer with an IF amplifier, and a local oscillator, all on a single chip. The transmitter is composed of the identical circuit blocks of RF amplifier and oscillator in addition to an up-conversion mixer. Compared to previous integrated receivers and transmitters reported at above 200 GHz, the proposed work includes the on-chip local oscillator and mixers operating at a fundamental mode. This simplifies the system architecture, thus not only reducing the chip area and DC consumption but also improving the RF performance such as high conversion gain, low spurious levels, and low noise figure. The receiver exhibits a peak conversion gain of 26 dB at 298 GHz, 3-dB bandwidth of 20 GHz, and noise figure of 12.0–16.3 dB at IF frequency from 1.1 to 7.7 GHz. The transmitter exhibits peak conversion gain of 25 dB, 3 dB bandwidth of 18 GHz, and output power of ${-}{\hbox{2.3}}$ dBm. The DC power consumption of the receiver and transmitter are 482 and 452 mW, respectively.

Design of a Planar UWB Dipole Antenna With an Integrated Balun Using Surrogate-Based Optimization

Abstract: A design of an ultrawideband (UWB) antenna with an integrated balun is presented. A fully planar balun configuration interfacing the microstrip input of the structure to the coplanar stripline (CPS) input of the dipole antenna is introduced. The electromagnetic (EM) model of the structure of interest includes the dipole, the balun, and the microstrip input to account for coupling and radiation effects over the UWB band. The EM model is then adjusted for low reflection over the UWB band by means of fast simulation-driven surrogate-based optimization. This approach allows us to obtain the final design at low computational costs and at a high-fidelity level of structure description. Measurements of the manufactured optimal design validate the use of the balun as well as the design approach.

Double-Balanced Graphene Integrated Mixer with Outstanding Linearity

Abstract: A monolithic double-balanced graphene mixer integrated circuit (IC) has been successfully designed and fabricated. The IC adopted the cross-coupled resistive mixer topology, integrating four 500 nm-gate-length graphene field-effect transistors (GFETs), four on-chip inductors, and four on-chip capacitors. Passive-first-active-last fabrication flow was developed on 200 mm CMOS wafers. CMOS back-end-of-line processes were utilized to realize most fabrication steps followed by GFET-customized processes. Test results show excellent output spectrum purity with suppressed radio frequency (RF) and local oscillation (LO) signals feedthroughs, and third-order input intercept (IIP3) reaches as high as 21 dBm. The results are compared with a fabricated single-GEFT mixer, which generates IIP3 of 16.5 dBm. Stand-alone 500 nm-gate-length GFETs feature cutoff frequency 22 GHz and maximum oscillation frequency 20.7 GHz RF performance. The double-balanced mixer IC operated with off-chip baluns realizing a print-circuit-boa...

Multi-material additive manufacturing of embedded low-profile antennas

Abstract: A low-profile antenna that includes an integrated artificial magnetic conducting (AMC) ground plane is presented and is fully fabricated using multi-material additive manufacturing. It is shown that combining standard fused deposition modelling with conductive micro-dispensing printing enable one to realise mechanically robust antenna systems that contain spatially variable dielectric properties and intricate three-dimensional conducting networks. To illustrate this capability, a low-profile antenna is designed, fabricated, and experimentally validated, consisting of a standard 2.6 GHz half wavelength printed dipole, balun, and AMC ground plane.

Design of Multilayer Balun Filter With Independently Controllable Dual Passbands

Abstract: In this letter, a novel multilayer dual-band balun filter using two dual-mode cross-slotted patch resonators placed back-to-back is proposed by converting two-port bandpass filter to a three port device. The operation frequency and bandwidth in each passband can be individually controlled, which is a new design concept for a dual-band balun filter. The detailed design procedure based on the coupling matrix is theoretically presented. A transmission zero between the two passbands is realized to improve the band to band isolation; meanwhile a good unbalanced to balanced conversion in both bands is realized. To demonstrate the design methodology, a dual-band balun filter is designed and fabricated. The measured results show good agreement with the simulation data.

13.3 A 10mW Bluetooth Low-Energy transceiver with on-chip matching

Abstract: Wireless sensor nodes present a difficult compromise at the system level between low power consumption, interference resilience and ease/size of the application. Recent low-power designs employ receiver architectures in which the LO runs at or below the received frequency (in TX at the required RF frequency). These architectures facilitate LO generation and distribution at a favorably low frequency, but cause a systematic, hard-to-circumvent susceptibility to out-of-band blockers in RX [1] and pulling in TX [1,2]. The presented Bluetooth Low-Energy (BLE) transceiver, as shown in Fig. 13.3.1, was purposely designed with a classic double-frequency VCO architecture to avoid these inherent weaknesses, but still significantly reduces the power consumption of designs of the same architecture [3,4]. In order to ease application, an on-chip DC-DC converter supports battery operation between 0.9V and 3.3V. An on-chip T/R switch, RX balun and impedance matching allow 50Ω chip antennae to be used directly on the single-ended RFIO pin, without the need for external RF filtering. This enables minimum-sized modules and a fast time-to-market.

A Broadband and Equivalent-Circuit Model for Millimeter-Wave On-Chip M:N Six-Port Transformers and Baluns

Abstract: A new equivalent-circuit model and parameter-extraction method for six-port M:N on-chip transformers and baluns are presented in this paper. All of the elements in the proposed model are extracted directly by $S$ -parameters based on full-wave electromagnetic (EM) simulations. Series branches in the model are used to capture the characteristics of the primary and secondary windings. The shunt impedance networks on the terminals represent the substrate loss. The magnetic coupling effects of windings are denoted by six mutual inductances. The electrical coupling effects are represented by mutual capacitances. In this paper, we have developed a parameter-extraction methodology for mutual inductances of six-port transformers. The proposed model and parameters extraction methodology are verified with a number of six-port transformers with different turn ratio by measurements and full-wave EM simulations. The proposed model shows good agreement with measured data over a wide frequency band.

A 37.5-mW 8-dBm-EIRP 15.5 $^{\circ}$ -HPBW 338-GHz Terahertz Transmitter Using SoP Heterogeneous System Integration

Abstract: A low-cost terahertz transmitter is proposed by using system-on-package (SoP) heterogeneous system integration. A signal source in 40-nm CMOS is integrated with an antenna array on a Benzocyclobutene carrier through a broadband low-loss terahertz interconnect. The signal source adopting triple-push oscillator topology is able to produce a differential output without any additional balun circuit. Hence, the power consumption and the chip area can be reduced. The antenna array containing 50 patch antennas is differentially excited to give simulated directivity, efficiency, and antenna gain as high as 22.6 dB, 88%, and 22 dBi, respectively, at 335 GHz. The terahertz interconnect employs a resonator coupling technique to provide low-loss and broadband performance while occupying a small area. Measured results show that the proposed terahertz transmitter can work at 338.4 GHz with equivalent isotropically radiated power (EIRP) of 8.0 dBm while consuming only 37.5 mW from a 1-V supply. The measured half-power beam-width can be as narrow as 15.5 $^{\circ}$ . The EIRP can be further raised to 9.5 dBm as the supply $V_{ DD}$ is increased to 1.3 V. The CMOS chip only occupies an area as small as 0.028 ${\hbox {mm}}^{2}$ . All of the design efforts enable the proposed terahertz transmitter to feature in small form factor, low power dissipation, low cost, and high performance. To the best of the authors' knowledge, this is the most compact, lowest power, lowest cost, and high-performance SoP-based terahertz transmitter reported thus far.

A 22 dBm, 0.6 mm² D-Band SiGe HBT Power Amplifier Using Series Power Combining Sub-Quarter-Wavelength Baluns

Abstract: We present a two-stage D-band power amplifier with stacked HBTs and sub-quarter-wavelength baluns as an efficient and compact series power combining technique which leads to a small die area of 0.62 mm² and a record 254 mW/mm² output power per unit die area. The power amplifier has been fabricated in a 90 nm SiGe BiCMOS technology and produces more than 21 dBm output power over the frequency range of 114-130 GHz with a peak output power of 160 mW (~22 dBm) at 120 GHz and a 3-dB small signal bandwidth of 35 GHz. To the author's knowledge, this is the highest recorded power for Si/SiGe BiCMOS process above 100 GHz. This amount of output power is 32% higher than highest prior work while the chip area is 13% the size of that work.

A Low-Power Broadband 200 GHz Down-Conversion Mixer with Integrated LO-Driver in 0.13 $\mu$ m SiGe BiCMOS

Abstract: This letter presents an active 200 GHz fundamental down-conversion mixer based on the Micromixer topology for low-power high data-rate wireless communications. The mixer-core operation requires a $-$ 5 dBm LO-signal, which is generated on-chip from an external single-ended source of only $-$ 20 dBm by means of a power-efficient LO-driver and a passive balun. Mixer, LO-driver and balun have been implemented together in a 450 GHz SiGe BiCMOS technology occupying a circuit core area of 0.21 mm $^{2}$ . For a 200 GHz LO-signal, the characterized circuit exhibits a maximum conversion gain of 5.5 dB over a 3 dB RF-bandwidth of 30 GHz, requiring only 17.4 and 22.5 mW of DC-power in the mixer core and in the LO-driver, respectively.

A wideband 700W push-pull Doherty amplifier

Abstract: A push-pull Doherty Power Amplifier (DPA) is proposed that uses a wideband power combiner BALUN, which is capable to provide the optimum fundamental and 2nd harmonic loading conditions over a large operating bandwidth to the active devices. A 700W DPA demonstrator using these techniques provides high average efficiency (> 40%) for a 7.5dB PAR DVB-T signal over a 37% relative RF-bandwidth.

An 85-W Multi-Octave Push–Pull GaN HEMT Power Amplifier for High-Efficiency Communication Applications at Microwave Frequencies

Abstract: This paper proposes a design methodology for multi-octave planar push–pull power amplifiers (PPPAs) to tackle the challenges associated with the integration of planar balanced to unbalanced transformers (baluns) with packaged transistors characterized by significant parasitics. This methodology relies on carefully selecting the balun’s placement and adding external matching networks to separately control the odd- and even-mode impedances presented to the power amplifier (PA) to ensure high-efficiency operation over a broad range of frequencies. Proper second harmonic impedances are obtained by placing the balun in close proximity to the transistors’ terminals and repurposing the packaged transistors’ leads into a coupled-line with a high coupling coefficient. Furthermore, adequate odd-mode terminations are realized using broadband matching networks at the unbalanced side of the baluns. Following this methodology, an 85-W PPPA was designed using off-the-shelf packaged gallium–nitride high electron-mobility transistors. The fabricated PA demonstrated drain efficiency and output power above 45% and 46.5 dBm, respectively, over the frequency band spanning from 0.45 to 1.95 GHz. Furthermore, the fabricated PA was successfully linearized using digital predistortion when driven with single- and multi-band modulated signals. Overall, the fabricated PA had the best reported power, efficiency, bandwidth, and second harmonic rejection combination for a multi-octave PPPA designed with input and output baluns using packaged off-the-shelf transistors.

On-Chip T/R Switchable Balun for 5- to 6-GHz WLAN Applications

Abstract: This brief presents a transmit/receive (T/R) switch combined with a transformer balun The differential inductor of the transformer balun is symmetrically wound to have the center taps at the outmost winding The center taps are controlled by nMOS transistors to switch between transmit and receive modes The transformer balun is matched at 5–6 GHz using parasitic capacitances of the transistors at the differential port and an integrated capacitor at the single-ended port For high transmit power handling, two transistors are stacked at the transmit path, and the source and drain of the transistors are biased with a dc voltage The measured insertion loss of the T/R switchable balun is 24–33 dB at 5–6 GHz with a return loss of less than $-$ 16 dB The amplitude and phase imbalance of the balun, respectively, are less than 1 dB and 4 $^{\circ} $ The input 1-dB power compression points for the transmit and receive mode are 28 and 20 dBm, respectively The integrated T/R switchable balun occupies only 012 $\hbox{mm}^{2}$

Planar-broadband dual-polarization base station antenna

Abstract: The invention discloses a planar-broadband dual-polarization base station antenna and belongs to the field of mobile communication base station antennae. The planar-broadband dual-polarization base station antenna mainly solves the problems that an existing base station antenna is complex in structure and has difficulty in being integrated with other devices. The planar-broadband dual-polarization base station antenna comprises radiation oscillators (1), feed baluns (2), a baffle board (3), coaxial cables (4), supporting columns (5) and a dielectric material plate (6). The radiation oscillators (1) are dual-polarization planar oscillators at +/-45 degrees, and the feed baluns (2) are planar feed baluns at +/-45 degrees. The radiation oscillator at -45 degrees and the feed balun at +45 degrees are printed on the upper surface of the dielectric material plate (6), and the radiation oscillator at +45 degrees and the feed balun at -45 degrees are printed on the lower surface of the dielectric material plate (6). The dielectric material plate (6) is fixed to the square baffle board (3) through the supporting columns (5). According to the planar-broadband dual-polarization base station antenna, planarization of the radiation oscillators and the feed baluns are achieved, meanwhile, the structure of the baffle board is simplified, and a stable directional diagram characteristic can be obtained in broadband.

Fully Integrated D-Band Direct Carrier Quadrature (I/Q) Modulator and Demodulator Circuits in InP DHBT Technology

Abstract: This paper presents design and characterization of D-band (110–170 GHz) monolithic microwave integrated quadrature up- and down-converting mixer circuits with on-chip RF and local oscillator (LO) baluns. The circuits are fabricated in 250-nm indium–phosphide double heterojunction bipolar transistor technology. The mixers require an external LO signal and can be used as direct carrier quadrature modulator and demodulator to implement higher order quadrature amplitude modulation formats. The up-converter has a single-sideband (SSB) conversion gain of 6 dB with image and LO suppression of 32 and 27 dBc, respectively. The chip can provide maximum output RF power of 2.5 dBm, a third-order output intercept point of 4 dBm, and consumes 78-mW dc power. The down-converter exhibits 14-dB SSB conversion gain with 25-dB image rejection ratio, and 11.5-dB SSB noise figure. The chip consumes 74-mW dc power and can deliver maximum output IF power of 4 dBm. Both chips have the same size with active area of 560 $\mu$ m $\,\times\,$ 440 $\mu$ m including the RF and LO baluns.

Doherty power amplifier combiner with tunable impedance termination circuit

Abstract: Doherty power amplifier combiner with tunable impedance termination circuit. A signal combiner can include a balun transformer circuit having a first coil and a second coil. The first coil can be implemented between a first port and a second port. The second coil can be implemented between a third port and a fourth port. The first port and the third port can be coupled by a first capacitor. The second port and fourth port can be coupled by a second capacitor. The first port can be configured to receive a first signal. The fourth port can be configured to receive a second signal. The second port can be configured to yield a combination of the first signal and the second signal. The signal combiner can include a termination circuit that couples the third port to a ground. The termination circuit can include a tunable impedance circuit.

A new compact ultra-wideband balun for printed balanced antennas

Abstract: A new ultra-wideband balun and its application for balanced antenna are presented in this paper. To realize the balun-type function, two different types of microstrip to slotline transition forms are adopted for the unbalanced and balanced outputs of the balun. Further, an ultra-wideband balun and its integration with a Vivaldi antenna are designed and fabricated to validate the feasibility of the new approach. Results indicated that the proposed balun and the antenna can operate from 3.6 to 10.7 GHz. For the proposed new balun, it exhibits a good balanced performance of within 0.5 dB magnitude imbalance and less than 6° phase imbalance between the two balanced outputs. Meanwhile, the antenna reveals good unidirectional radiation patterns.

High performance passive devices for millimeter wave system integration on integrated fan-out (InFO) wafer level packaging technology

Abstract: High performance passive devices for millimeter wave (MMW) system, including inductor, ring resonator, power combiner, coupler, balun, transmission line, and antenna, are first realized using integrated fan-out (InFO) wafer level packaging technology. The inductors has quality factor over 40; the power combiner, coupler, and balun show lower transmission loss than on-chip passives; antenna has the efficiency of over 60%. These devices on InFO enable low noise and power MMW system for mobile communication and IoT applications.

Systems and methods related to linear and efficient broadband power amplifiers

Abstract: Systems and methods related to linear and efficient broadband power amplifiers. A power amplifier (PA) system can include an input circuit configured to receive a radio-frequency (RF) signal and split the RF signal into a first portion and a second portion. The PA system can further include a Doherty amplifier circuit including a carrier amplification path coupled to the input circuit to receive the first portion and a peaking amplification path coupled to the input circuit to receive the second portion. The PA system can further include an output circuit coupled to the Doherty amplifier circuit. The output circuit can include a balance to unbalance (BALUN) circuit configured to combine outputs of the carrier amplification path and the peaking amplification path to yield an amplified RF signal.

Optically controlled GeTe phase change switch and its applications in reconfigurable antenna arrays

Abstract: Characterization of GeTe-Based RF Switches under direct optical laser excitation is shown with the ON state DC electrical resistivity and OFF state capacitance. Based on our tightly-coupled dipole array with performance in excess of 4 to 1 bandwidth over wide-scan angle up to 60 degrees, and with in-band rejection capability using reconfigurable baluns, the antenna aperture is shown to exhibit reconfiguration flexibility with the integration of optically-controlled GeTe-Based RF switches.

Compact 60 GHz LTCC balun bandpass filter with two transmission zeroes

Abstract: A new balun–bandpass filter with a quasi-elliptic response for 60 GHz wireless communication systems is proposed. It is designed in the form of a substrate integrated waveguide (SIW) and fabricated with the standard low-temperature co-fired ceramic (LTCC) technology. Both simulated and experimental results are provided, which have good agreement. The results indicate that the proposed balun filter has a good balance performance with <1.1 dB amplitude imbalance and better than 3.4° phase imbalance, compact size, as well as high selectivity.

A new compact high-efficiency mmWave power amplifier in 65 nm CMOS process

Abstract: This paper presents a new design technique for high-efficiency CMOS mmWave power amplifier (PA). The proposed PA adopts NMOS capacitors connected at the gates of the transistors of the last amplifying stage to compensate gate capacitance variation over large signal swing, improving the linearity and the power efficiency. Implemented in 65 nm CMOS process, the presented PA consists of two differential stages, uses baluns, transformers and inductors to realize the input, output, and inter-stage power matching, and achieves a peak PAE of 24.2%, a 6 dB back-off PAE of 10.5% from 3 dB gain compression, a maximum gain of 17 dB, and a 3-dB bandwidth from 68 to 78 GHz.

Design of microstrip tri-mode balun bandpass filter with high selectivity

Abstract: A new microstrip tri-mode balun bandpass filter (BPF) with good filter-type and balun-type functions is presented. To realise the tri-mode BPF performance, the multimode stepped-impedance resonator is introduced and parallel coupled to both the balanced and the unbalanced ports. To achieve 180° phase difference, two types of transition structures, i.e. the microstrip–coplanar waveguide–microstrip transition and the microstrip–coplanar stripline–microstrip transition, are adopted for the two balanced output ports design, respectively. A balun BPF operating at 2.6 GHz is designed and fabricated to validate the feasibility of the new approach. Results indicate that the proposed balun BPF exhibits not only high selectivity with two transmission zeros locating at 1.7 and 3.7 GHz but also good balance performance with 0.5 dB magnitude imbalance and 5° phase imbalance between the balanced outputs.

Compact coupled-line balun with complex impedances transformation and high isolation

Abstract: A planar microstrip circuit is proposed to design a kind of coupled-line balun with good ports matching and high output-ports isolation for complex source to complex load impedance transformation. This balun prototype essentially consists of three coupled-line sections, a tapped open transmission-line stub (TOTS) on the left-hand side, and a tapped complex equivalent-impedance part (TCEP) on the right-hand side. The TCEP is the key to realise high output isolation and all ports matching. Based on the traditional even-odd mode technique and the transmission-line theory, closed-form mathematical equations for circuit electrical parameters are obtained. To demonstrate this proposed design theory, a practical microstrip coupled-line balun is designed, simulated and measured to operate at approximately 2 GHz, indicating high isolation and balanced output. Good agreements between the simulated and measured results verify this design.

Toward Realization of 2.4 GHz Balunless Narrowband Receiver Front-End for Short Range Wireless Applications

Abstract: The demand for radio frequency (RF) transceivers operating at 2.4 GHz band has attracted considerable research interest due to the advancement in short range wireless technologies. The performance of RF transceivers depends heavily on the transmitter and receiver front-ends. The receiver front-end is comprised of a low-noise amplifier (LNA) and a downconversion mixer. There are very few designs that focus on connecting the single-ended output LNA to a double-balanced mixer without the use of on-chip transformer, also known as a balun. The objective of designing such a receiver front-end is to achieve high integration and low power consumption. To meet these requirements, we present the design of fully-integrated 2.4 GHz receiver front-end, consisting of a narrow-band LNA and a double balanced mixer without using a balun. Here, the single-ended RF output signal of the LNA is translated into differential signal using an NMOS-PMOS (n-channel metal-oxide-semiconductor, p-channel metal-oxide-semiconductor) transistor differential pair instead of the conventional NMOS-NMOS transistor configuration, for the RF amplification stage of the double-balanced mixer. The proposed receiver circuit fabricated using TSMC 0.18 µm CMOS technology operates at 2.4 GHz and produces an output signal at 300 MHz. The fabricated receiver achieves a gain of 16.3 dB and consumes only 6.74 mW operating at 1.5 V, while utilizing 2.08 mm2 of chip area. Measurement results demonstrate the effectiveness and suitability of the proposed receiver for short-range wireless applications, such as in wireless sensor network (WSN).

Dual polarized array antenna with modular multi-balun board and associated methods

Abstract: An array antenna includes a modular, multi-layer, multi-balun board structure for use in feeding a dual polarization radiating element. In some embodiments, contacts on a multi-balun board structure may be directly conductively coupled to corresponding feed points of a dual polarization radiating element during antenna assembly. The multi-balun board structure may be inserted into an opening within an aperture board of an array antenna before the contacts are secured to the feed points. Dual balun board structures may be provided for some or all of the radiating elements on the aperture board.

A Simple and Effective Method for Designing Frequency Adjustable Balun Diplexer With High Common-Mode Suppression

Abstract: A simple and effective structure based on traditional coupled-line theory and the configuration of folded open-loop ring resonators (OLRRs) was used to design a balanced-to- unbalanced (balun) diplexer. The two resonant frequencies of the balun diplexer are easily adjusted by changing the physical dimensions of OLRRs and microstrip lines and they had high common-mode suppression. In this study, the designed balun diplexer is investigated for LTE (2.6 GHz) and WLAN (5.2 GHz) band applications.

Low-profile, broad-bandwidth, dual-polarization dipole radiating element

Abstract: An antenna having a first dipole element configured to emit or receive electromagnetic signals in a first polarization direction wherein the first dipole is fed by a first inclined balun and a second dipole element configured to emit or receive electromagnetic signals in a second polarization direction that is orthogonal to the first polarization direction wherein the second dipole is fed by a second inclined balun.

The evolution of the push-pull RFPA

Abstract: The evolution of the push-pull power amplifier is summarized. The technique would appear to have originated about 100 years ago, and quickly became the default circuit configuration for early vacuum tube audio amplifiers. Its use has also been widely adopted for implementing power amplifiers at radio frequencies (“RF”), but the key requirement for near-ideal magnetically coupled transformers has halted the progress of the push-pull amplifier into the GHz bands. When transformers are replaced by balun structures, based on the properties of transmission lines, the assumed low frequency advantages of push-pull operation can quickly be lost. In particular, little attention has been paid to the response of balun stuctures at harmonic frequencies.