Frequency Mixer Research Articles

Graphene: A new beginning for semiconductor devices beyond silicon

Currently, graphene is a topic of very active research fields due to its exceptional electronic properties. For various RF circuit applications, including low-noise amplifiers, the unique ambipolar nature of graphene field-effect-transistors can be utilized for high-performance frequency multipliers, mixers, and highspeed radiometers. Direct current (DC) and radio frequency (RF) measurements were performed on graphene field-effect transistors to find out the DC and RF properties. Two sets of GFETs were measured; first chip was fabricated with SiC process and the second with CVD process. The SiC GFET impedance levels were too high to measure RF properties. RF-measurements were performed on CVD GFETs. The CVD GFET cut-off frequency was found to be approximately 80 MHz, which is in the same range as the calculated cut-off frequency. MOSFET small-signal model was used for GFETs and the model parameters are presented .The results of the DC measurements were analyzed and the data was fitted according to an existing device resistance model. The curve-fit to total device resistance gives estimations on parameters such as contact resistance, residual charge carrier concentration and conductivity mobility.

Real-time upstream services demonstration in orthogonal frequency division multiplexing-passive optical network system

Real-time digital service and multimedia service upstream transmission in Digital Signal Processing (DSP)-based Orthogonal Frequency Division Multiplexing-Passive Optical Network (OFDM-PON) is experimentally demonstrated with Centralised Light Source (CLS) configuration in this paper. After transmitted over 25 km Standard Single Mode Fibre (SSMF) with −16.5 dBm optical power at receiver, the Bit Error Rate (BER) is 9.5 × 10−11. The implementations of digital domain up-conversion and down-conversion based on Field Programmable Gate Array (FPGA) are introduced, which can reduce the cost of In-ph-ase and Quadrature (IQ) radio frequency mixers utilised at transmitter and receiver. A carrier synchronization algorithm is implemented for compensating carrier offset. A channel equalization algorithm is adopted for compensating the damage of channel. A new structure of Frequency Synchronization Unit (FSU) designed in FPGA is also proposed to cope with the frequency shifting at receiver.

Scalable Fabrication of Ambipolar Transistors and Radio‐Frequency Circuits Using Aligned Carbon Nanotube Arrays

Field-effect transistors (FETs) are fabricated on a large scale and with a high yield of over 95% based on aligned carbon nanotube arrays directly grown on quartz, and exhibit ambipolar transfer characteristics that can be used to construct ambipolar RF circuits. RF circuits including frequency doubler and mixer based on the ambipolar FETs demonstrate unequivocally working frequency up to 40 GHz.

Bias optimization of 2.4 GHz double gate MOSFET RF mixer

The optimum biasing points and structural design parameters for novel nano-scale double gate MOSFET (DG-MOSFET) radio frequency mixers are investigated at 2.4 GHz. Our objective is to analyze and identify the correlation of the conversion gain of the mixer circuit with the signal amplitude of the local oscillator (LO) as well as different device parameters, such as the gate length (L gate ), doping concentration (N A ) and body thickness (t Si ), thus minimizing signal loss and power consumption and increasing stability. The most important figure of merit is found to be the LO DC bias that determines the level of non-linearity in the transconductance response. Furthermore, we observe that in properly designed DG-MOSFETs $$(\hbox{L}_{gate} \ge 3t_{Si}),\; \hbox{L}_{gate}$$ ( L g a t e ? 3 t S i ) , L g a t e and N A have limited impact on the conversion gain of the mixer, while t Si has a more significant role to play. Although the mixing performance of DG-MOSFETs is ultimately limited by the short channel effects perpetrated by any given structural constraint, an optimum body thickness t Si exists in each case to maximize the conversion gain. Thus, we illustrate how 2D and quantum-corrected simulations can identify the optimum body thickness and optimum bias conditions in such compact nano-scale mixers.

The Design of Gilbert-Type-Based Zero Intermediate Frequency CMOS Mixer

Based on the techniques of dynamic current injection, common source node resonance, second-order linearity performance and the application of CMOS technology, a 1.8V power supply voltage active folding Gilbert-type zero intermediate frequency mixer has been designed by using Candense design system. The result of circuit stimulation shows, single sideband noise figure is 6.109dB when the mixer locates at 1MHz, 6.71dB at 100KHz, 10.631dB at 10KHz. Frequency conversion gain is 11.389dB and input third-order intermodulation point is 4.639dBm.

Vacuum frequency mixer with a field emitter array

A fundamental study on the development of a frequency mixer with a field emitter array was conducted. A grid to control the electron beam was introduced to the vacuum triode, which consisted of a field emitter array and an external collector. The transconductance of the field emitter array was 1.3 μS. It was found that the collector current varied linearly with the grid voltage, and the rate of the variation was estimated to be 0.9 μS. It was suggested that the fabricated tetrode would work as a frequency mixer. A preliminary experiment on the mixing of signals with frequencies of 10 and 15 kHz was performed, and the generation of signals with the sum and difference frequencies was confirmed. The possible operating frequency of the field emitter array-based vacuum frequency mixer will be 1 MHz or higher, using a larger field emitter array that can be operated at higher currents.

Fabrication of Carbon Nanotube High-Frequency Nanoelectronic Biosensor for Sensing in High Ionic Strength Solutions

The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) make them good candidates for high sensitivity biosensors. When a charged molecule binds to such a sensor surface, it alters the carrier density in the sensor, resulting in changes in its DC conductance. However, in an ionic solution a charged surface also attracts counter-ions from the solution, forming an electrical double layer (EDL). This EDL effectively screens off the charge, and in physiologically relevant conditions ~100 millimolar (mM), the characteristic charge screening length (Debye length) is less than a nanometer (nm). Thus, in high ionic strength solutions, charge based (DC) detection is fundamentally impeded. We overcome charge screening effects by detecting molecular dipoles rather than charges at high frequency, by operating carbon nanotube field effect transistors as high frequency mixers. At high frequencies, the AC drive force can no longer overcome the solution drag and the ions in solution do not have sufficient time to form the EDL. Further, frequency mixing technique allows us to operate at frequencies high enough to overcome ionic screening, and yet detect the sensing signals at lower frequencies. Also, the high transconductance of SWNT transistors provides an internal gain for the sensing signal, which obviates the need for external signal amplifier. Here, we describe the protocol to (a) fabricate SWNT transistors, (b) functionalize biomolecules to the nanotube, (c) design and stamp a poly-dimethylsiloxane (PDMS) micro-fluidic chamber onto the device, and (d) carry out high frequency sensing in different ionic strength solutions.

벡터 전압 수신기를 이용한 2-포트 산란 계수 분석 시스템

본 논문에서는 상용 벡터 회로망 분석기를 사용하지 않고도, 신호 발생기, 벡터 전압 수신기, 방향성 결합기, 주파수 혼합기 등의 기본적인 초고주파 장비/소자를 활용하여 평가하고자 하는 초고주자 소자의 2-포트 산란 계수를 측정할 수 있는 시스템을 제안한다. 벡터 회로망 분석기를 대용할 수 있는 산란 계수 측정 시스템의 해석적 모델과 제작방법을 제시하고, 이를 1-포트와 2-포트 소자에 대하여 각각 적용한 산란 계수를 측정하여 구현된 시스템을 평가하였다. 평가 주파수 대역에 따라 비교적 낮은 대역에서는 단일 신호 발생기와 벡터 전압 수신기를 사용한 직접 수신법을, 높은 대역에서는 추가의 신호원과 주파수 혼합기를 사용하여 신호를 하향 복조하는 헤테로다인 방식을 사용하여 산란 계수를 결정짓는 벡터 전압을 수신하였다. 이들 각각의 수신 방법으로 UHF와 X 대역 초고주파 소자의 2-포트 산란 계수를 평가하였고, 그 유효성을 상용 벡터 회로망 분석기로 검증하였다. This paper presents a vector network analysis system for 2-port scattering parameters of microwave devices using some basic microwave instruments/devices such as signal generators, vector voltmeter, directional couplers and frequency mixers. The analytical model and implementation method for scattering parameter measurements - which can replace the vector network analyzers - are presented. The performance of the implemented system is evaluated through 1- and 2-port scattering parameter measurements, respectively. The vector volt signals which determine the scattering parameters are detected in two distinct methods depending on the frequency band of interests; a direct-detection method with a single signal generator and vector voltmeter for relatively low band and a heterodyne method to frequency down-mix associated with an additional signal source as well as frequency mixers for high band are used, respectively. Using these two methods, scattering parameters of UHF and X bands are evaluated and their performances are verified through a comercial vector network analyzer.

임의유전체 기판을 이용한 주파수 혼합기의 소형화

A size-reduced high frequency mixer designed by adopting artificial dielectric substrate is described in this work. The artificial dielectric substrate is composed by stacking the lower substrate in which a lot of metalized via-holes exist, and upper substrate on which microstrip lines are realized. The effective dielectric constant increases due to the inserted lots of via-holes, and this may be applied to size-reduction of high frequency circuits. In this work, in order to present an application example of size-reduction for active high frequency circuits using the artificial dielectric substrate, a 8GHz single gate mixer is miniaturized and measured. It is described that the basic circuit elements for mixers such as hybrid, low pass filter, and matching networks can be replaced by the artificial dielectric substrate for size-reduction. The final mixer has 55% of size compared to the normal one. The measured average conversion gain is around 3dB which is almost similar result as the normal circuit.

Fabrication of Al/MgO/C and C/MgO/InSe/C tunneling barriers for tunable negative resistance and negative capacitance applications

Abstract In this work, the design and characterization of magnesium oxide based tunneling diodes which are produced on Al and InSe films as rectifying substrates are investigated. It was found that when Al thin films are used, the device exhibit tunneling diode behavior of sharp valley at 0.15 V and peak to valley current ratio (PVCR) of 11.4. In addition, the capacitance spectra of the Al/MgO/C device show a resonance peak of negative capacitance (NC) values at 44.7 MHz. The capacitance and resistance–voltage characteristics handled at an ac signal frequency of 100 MHz reflected a build in voltage ( V bi ) of 1.29 V and a negative resistance (NR) effect above 2.05 V. This device quality factor ( Q )–voltage response is ~10 4 . When the Al substrate is replaced by InSe thin film, the tunneling diode valley appeared at 1.1 V. In addition, the PVCR, NR range, NC resonance peak, Q and V bi are found to be 135, 0.94–2.24 and 39.0 MHz, ~10 5 and 1.34 V, respectively. Due to the wide differential negative resistance and capacitance voltage ranges and due to the response of the C/MgO/InSe/C device at 1.0 GHz, these devices appear to be suitable for applications as frequency mixers, amplifiers, and monostable–bistable circuit elements (MOBILE).

A Built-In Voltage Measurement Technique for the Calibration of RF Mixers

A built-in technique to measure internal DC voltage levels used for the calibration of radio frequency (RF) mixers is presented in this paper. According to a common alternate test approach, RF mixer calibration is based on the prediction of the circuit's performance characteristics that requires the acquisition of a set of DC voltage observables obtained from specific nodes of the mixer operating in homodyne mode. These observables, however, often correspond to internal nodes where direct access is not always possible. Furthermore, accurate calibration might require a relatively large set of voltage observables whose direct access would lead to a waste of resources and to increased cost. The proposed built-in technique provides digital readings for the DC levels at all nodes of interest through a single interface by exploiting the use of a voltage acquisition circuit implemented by a simple analog to digital converter, which consists of a ring-type voltage controlled oscillator and a counter. A reading correction method to minimize the uncertainty introduced by process variations and device mismatches in the acquisition circuit itself is also described. The efficiency of the proposed technique has been validated by its application to the calibration procedure of a typical differential RF mixer designed in a 0.18-μm CMOS technology. Simulation results have been obtained and assessed, both for the proposed built-in voltage measurement technique and for the direct voltage measurement approach, in favor of comparison.

New design approach of FPGA based control system and implementation result in KSTAR

The frequency modulation (FM) reflectometer in KSTAR is under commissioning to measure the electron density profile which focused on edge area of plasma. This diagnostic system generated order of tens MHz output signal from an intermediate frequency (IF) amplifier after a radio frequency (RF) mixer. An arbitrary waveform generator is also required for triggering a fast frequency sweep source. We have developed a data acquisition system with multi-functions which composes several digitizers and waveform generator for KSTAR reflectometer. Along with this typical hardware system, we have newly developed a field programmable gate array (FPGA) based signal controller. This customized board adapts FPGA Mezzanine Card (FMC) as a daughter board within single package of 3U Compact PCI form factor. We have been evaluating Experimental Physics and industrial control system (EPICS) input output controller (IOC) over an embedded PowerPC processor on several customized hardware. Using previous result of investigation, this new processor embedded digitizer supports full function of EPICS including KSTAR standard software framework.

Optical frequency mixing through nanoantenna enhanced difference frequency generation: Metatronic mixer

A design for a subwavelength all-optical frequency mixer is proposed. The method relies on enhanced difference-frequency generation, which is achieved in two steps with the help of plasmonic nanoantennas. The interaction of the two input signals with the nonlinear material is increased through the use of input nanoantennas, which focus the incident energy of two different frequencies onto the nanoparticle formed by a nonlinear material. Next, the difference-frequency emission is enhanced through the Purcell effect by the use of a separate output nanoantenna that is resonant at the difference frequency. The application of this twofold approach allows for a significant enhancement in the difference-frequency generation efficiency. Simulation results are presented highlighting the features of the method. This multi-element nanostructure is indeed an optical mixer circuit element in the metatronic paradigm.

Na2Ge2Se5: A highly nonlinear optical material

We report an integrated experimental and theoretical study of the two-dimensional polar selenogermanate compound Na2Ge2Se5, which exhibits strong nonlinear optical (NLO) second harmonic generation response in the visible and infrared region. The compound is type-I phase-matchable with a large SHG coefficient χ(2)≈290pmV−1, which is the second highest among the phase-matchable NLO materials. It also performs as an NLO frequency mixer to produce radiation via difference frequency generation. The compound is optically transparent from the visible (0.521μm) to the far IR (18.2μm) and melts congruently. Ab initio density functional theory band structure calculations show that the unusually large second-order optical nonlinearity is attributed to the two-dimensional character of the crystal structure. Raman, IR and optical absorption spectroscopy, differential thermal analysis, NLO properties of derivatives of Na2Ge2Se4.55Te0.45 and Na2Ge1.64Sn0.36Se5 and thermal expansion behavior studies are also reported.

Terahertz hot electron bolometer waveguide mixers for GREAT

Supplementing the publications based on the first-light observations with the German Receiver for Astronomy at Terahertz frequencies (GREAT) on SOFIA, we present background information on the underlying heterodyne detector technology. We describe the superconducting hot electron bolometer (HEB) detectors that are used as frequency mixers in the L1 (1400 GHz), L2 (1900 GHz), and M (2500 GHz) channels of GREAT. Measured performance of the detectors is presented and background information on their operation in GREAT is given. Our mixer units are waveguide-based and couple to free-space radiation via a feedhorn antenna. The HEB mixers are designed, fabricated, characterized, and flight-qualified in-house. We are able to use the full intermediate frequency bandwidth of the mixers using silicon-germanium multi-octave cryogenic low-noise amplifiers with very low input return loss. Superconducting HEB mixers have proven to be practical and sensitive detectors for high-resolution THz frequency spectroscopy on SOFIA. We show that our niobium-titanium-nitride (NbTiN) material HEBs on silicon nitride (SiN) membrane substrates have an intermediate frequency (IF) noise roll-off frequency above 2.8 GHz, which does not limit the current receiver IF bandwidth. Our mixer technology development efforts culminate in the first successful operation of a waveguide-based HEB mixer at 2.5 THz and deployment for radioastronomy. A significant contribution to the success of GREAT is made by technological development, thorough characterization and performance optimization of the mixer and its IF interface for receiver operation on SOFIA. In particular, the development of an optimized mixer IF interface contributes to the low passband ripple and excellent stability, which GREAT demonstrated during its initial successful astronomical observation runs.

Graphene-based ambipolar electronics for radio frequency applications

Graphene is considered as a promising material to construct field-effect transistors (FETs) for high frequency electronic applications due to its unique structure and properties, mainly including extremely high carrier mobility and saturation velocity, the ultimate thinnest body and stability. Through continuously scaling down the gate length and optimizing the structure, the cut-off frequency of graphene FET (GFET) was rapidly increased and up to about 300 GHz, and further improvements are also expected. Because of the lack of an intrinsic band gap, the GFETs present typical ambipolar transfer characteristic without off state, which means GFETs are suitable for analog electronics rather than digital applications. Taking advantage of the ambipolar characteristic, GFET is demonstrated as an excellent building block for ambipolar electronic circuits, and has been used in applications such as highperformance frequency doublers, radio frequency mixers, digital modulators, and phase detectors.

Graphene field-effect transistor for radio-frequency applications : review

Currently, graphene is a topic of very active research in fields from science to potential applications. For various radio-frequency (RF) circuit applications including low-noise amplifiers, the unique ambipolar nature of graphene field-effect transistors can be utilized for high-performance frequency multipliers, mixers and high-speed radiometers. Potential integration of graphene on Silicon substrates with complementary metal-oxide-semiconductor compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene metal-oxide-semiconductor field-effect transistors to minimize parasitics and improve gate modulation efficiency in the channel. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antenna, where its success depends on quality of materials. We also attempt to discuss future applications and challenges of graphene.

Two-dimensional PPLN for simultaneous laser Q-switching and optical parametric oscillation in a Nd:YVO_4 laser

We report on a tunable intracavity optical parametric oscillator (IOPO) achieved using a two-dimensional (2D) periodically poled lithium niobate (PPLN) as simultaneously an electro-optic (EO) Bragg Q-switch and an optical frequency mixer (OFM) in a diode-pumped Nd:YVO(4) laser. The 2D periodic domain inversion structure is designed to provide two orthogonal reciprocal vectors to respectively satisfy the phase-matching conditions required by the two quasi-phase-matching devices (i.e., the PPLN EO Bragg deflector and the PPLN OFM). At a ~140-V Q-switching voltage and a 1-kHz switching rate, we obtained a signal wave at 1550 nm with a pulse energy of 9.7 μJ (corresponding to a peak power of ~2.4 kW) from the IOPO at 9.1-W diode pump power. Simultaneously we also observed multi-wavelength generation from the system originating in the single-pass parametric conversions in the 2D nonlinear photonic crystal structure. Temperature tuning of the IOPO signal wavelength in the eye-safe region was also demonstrated.

Graphene: Its Fundamentals to Future Applications

Currently, graphene is a topic of very active research fields from science to potential applications. For various RF circuit applications, including low-noise amplifiers, the unique ambipolar nature of graphene field-effect-transistors can be utilized for high-performance frequency multipliers, mixers, and high-speed radiometers. Potential integration of graphene on silicon substrates with CMOS compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene MOSFETs to minimize parasitics and improve gate modulation efficiency in the channel with zero or a small bandgap. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antennas, where its success depends on the quality of materials. We also attempt to discuss future applications and challenges of graphene.

A Nearly All-Digital Frequency Mixer Based on Nonlinear Digital-to-Analog Conversion and Intermodulation Cancellation

We propose a nearly all-digital frequency mixer producing either the sum or difference of two frequencies provided as digital clocks. No filtering of the clock inputs is needed to suppress intermodulation products at the output. The mixer achieves high spurious-free dynamic range through optimization of an output nonlinear DAC and a multiphase intermodulation cancellation technique. A programmable logic implementation demonstrates feasibility and performance of the architecture.