Intermodulation Distortion Characteristics Research Articles

Temperature Dependence of the Taylor Series Coefficients and Intermodulation Distortion Characteristics of GaN HEMT

This paper focused on nonlinear distortion modeling and characterization of AlGaN/GaN HEMT on SiC substrate using a two-tone intermodulation measurement. The variation of Taylor series coefficients with temperature: linear terms ( ${G}_{ {m}}$ and ${G}_{ {ds}}$ ), nonlinear terms ( ${G}_{ {m2}}$ , ${G}_{ {m3}}$ , ${G}_{ {ds2}}$ , and ${G}_{ {ds3}}$ ), and the cross terms ( ${G}_{ {md}}$ , ${G}_{ {md2}}$ , and ${G}_{ {m2d}}$ ) are reported. Furthermore, in the saturation region, the magnitude of ${G}_{ {ds}}$ related linear, nonlinear, and cross terms ( ${G}_{ {ds}}$ , ${G}_{ {ds2}}$ , ${ G}_{ {ds3}}$ , ${G}_{ {md}}$ , ${ G}_{ {md2}}$ , and ${G}_{ {m2d}}$ ) are found to be minimal. This implies that the nonlinear distortion behavior of the device is transconductance-dependent. A temperature-dependent current-based empirical model taking into account bias, input power, and frequency for the nonlinearity of the device has been developed based on two-tone measurements. The modeled data are consistent with the two-tone measurements, providing an effective means for analyzing these devices.

Effect of Barrier Thickness on Linearity of Underlap AlInN/GaN DG-MOSHEMTs

In this proposed work, an extensive study on the linearity performance of underlap AlInN/GaN double gate metal oxide semiconductor high electron mobility transistors (MOS-HEMT) has been analyzed using 2D Sentaurus TCAD simulation. Specifically a brief comparison is made on the linearity and intermodulation distortion characteristics of the proposed device due to variation of barrier layer thickness from 2 nm to 6 nm. Various parameters such as transconductance ([Formula: see text], second-order transconductance ([Formula: see text]), third-order transconductance ([Formula: see text]), second-order voltage intercept point (VIP2), third-order voltage intercept point (VIP3), third-order input intercept point (IIP3) and third-order intermodulation distortion (IMD3) of underlap AlInN/GaN double gate metal oxide semiconductor high electron mobility transistors (MOS-HEMT) are discussed. The simulated results obtained confirms that by careful optimization of barrier layer thickness linearity characteristics of this proposed device can be improved, which can be suitable for analog and circuit applications.

High-Current Backside-Illuminated Photodiode Array Module for Optical Analog Links

We have developed a high-current photodiode (PD) array module that consists of a beam splitter, which splits a light beam from a single-mode fiber into four beams with identical powers, a backside-illuminated InGaAs p-i-n PD array, and a two-stage Wilkinson RF power combiner. To obtain a linear PD response, the PD is equipped with a partially depleted absorber, which reduces the bias voltage. To prevent thermal failure, the backside-illuminated PD structure is used, which reduces the thermal resistivity. The beam splitter is fabricated using optical contacts at the SiO2 interfaces between a coating film and a neighboring prism to prevent degradation of the adhesive glue at the prism interfaces along the optical path; therefore, light with a power of a watt level can be used. The two-stage Wilkinson combiner combines four RF outputs of the PD array into a single-RF output through a K connector; the combiner also works as an impedance-matching circuit. Experimental results reveal that an RF power output of 29.0 dBm can be obtained at a frequency of 5 GHz, and good intermodulation distortion characteristics with a third-order intercept point of 32.5 dBm can be achieved.

Distortion Compensation for Thermal Memory Effect on InGaP/GaAs HBT Amplifier by Inserting RC-Ladder Circuit in Base Bias Circuit

An inter-modulation distortion (IMD) compensation method for thermal memory effect using a multistage RC-ladder circuit has been proposed. The IMD caused by the thermal memory effect on an InGaP/GaAs HBT amplifier was compensated for by inserting a multistage RC-ladder circuit in the base bias circuit of the amplifier. Since heat flux owing to self-heating in the transistor can be approximated with a multistage thermal RC-ladder circuit, the canceling of IMD by an additional electrical memory effect generated from the RC-ladder circuit is predicted. The memory effects cause asymmetrical characteristics between upper and lower IMD. The IMD caused by the memory effects is expressed as a vector sum of each origin. By adjusting an electrical reactance characteristic for sub-harmonics affected by the thermal memory effect in the amplifier circuit, the asymmetric characteristic is symmetrized. The parameters of the RC-ladder circuit were estimated so that the adjusted electrical reactance characteristic is reproduced in simulation. A fabricated InGaP/GaAs HBT amplifier with the thermal memory effect compensation circuit exhibited a symmetrized and suppressed IMD characteristics.

이동 통신 기지국 안테나의 수동 상호 변조 왜곡에 진동이 미치는 영향 분석 및 개선 방안

본 논문은 800 MHz 대역의 CDMA 이동 통신 기지국의 안테나에서 보편적으로 발생되고 있는 수동 상호 변조 왜곡 특성에 대하여 조명해 보고 진동이 수동 상호 변조 왜곡에 미치는 영향을 분석하여 그에 대한 개선 방안을 연구하였다. 이동 통신 기지국은 대부분 건물 옥상이나 철탑 등 고지대에 위치하게 된다. 그렇기 때문에 비, 바람 등 자연 환경적인 요인이나 차량 등 생활 환경적인 요인에 의해 미세한 흔들림 곧, 진동이라는 영향을 수없이 받고 있다. 이에 착안하여 이동 통신 안테나가 진동에 의해 영향을 받고 있다는 것을 실험을 통해 입증해 냄으로써 실제 이동 통신 운용 필드에서 진동이라는 요인에 의해 안테나의 수동 상호 변조 왜곡 특성이 쉽게 열화된다는 것을 증명해 보였다. 또한, 진동에 잘 견딜 수 있는 안테나 구조에 대한 개선 방안을 제시하였고, 구조 개선 전후 안테나의 수동 상호 변조 왜곡 특성을 실험적으로 비교함으로써 그 열화 정도를 35 dB 이상 향상시킬 수 있었다. This work investigates the effects of vibration on the passive intermodulation distortion characteristics of base station antennas for 800 MHz CDMA mobile communication systems. In general, base station antennas are located at high positions such as on building rooftops or iron towers. Thus the antennas are always affected by random vibrations, coming from various natural environmental factors such as rain and wind, or from living environmental factors such as vehicles and trains passing by. The measured intermodulation distortion characteristics before and after vibration accelerated degradation test show that vibrations are indeed the main cause for the intermodulation distortion performances of such antennas. To minimize the effects of vibrations, a new antenna design isptoposed that has an improved tolerance for vibrations. Experimental results show that the proposed antenna design dramatically reduces the degradation of the intermodulation distortion more than 35 dB.

Improvement of microwave power amplifier intermodulation distortion by a novel second‐harmonic short‐circuit termination

AbstractThe intermodulation distortion characteristics of a microwave Si MOSFET power amplifier are improved by realization of a true second harmonic short‐circuit termination of the drain. By the use of a circuit configuration taking account of the parasitic inductance of the FET drain, second harmonic short‐circuiting of the drain is realized. First, a two‐variable Taylor series expansion model of the drain current with respect to the gate voltage and the drain voltage is used and an approximate analysis by the perturbation method, including the low frequency (signal difference frequency) and second harmonic load dependence of the third‐order intermodulation distortion, is used for an analysis of the intermodulation distortion and its asymmetry. Next, a 1‐GHz Si MOSFET power amplifier is fabricated. Reduction of the intermodulation distortion and its asymmetry is realized by introducing a true second harmonic short circuit for the drain. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(11): 9–16, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20344

High-Power-Density and High-Gain δ -Doped In0.425Al0.575As ∕ In0.425Ga0.575As Low-Voltage for Operation

A δ-doped metamorphic high electron mobility transistor with an channel to effectively relieve the impact-ionization effects has been successfully fabricated by the molecular beam epitaxy system. With the designs of an channel layer and a wide-bangap Schottky-contact layer, good carrier confinement, improved breakdown, low output conductance, and high voltage gain with good linearity have been simultaneously achieved. We have also comprehensively investigated the microwave and power performances as a function of and , respectively. Experimentally, the unity-gain cutoff frequency and the maximum oscillation frequency slightly decrease with of above . However, the power gain and the output power increase as increases from 1 to . Furthermore, the proposed device has also demonstrated good intermodulation distortion characteristics at lower biases, indicating its promise for the large-scale and low-voltage millimeter-wave integrated circuit applications.

Intermodulation distortion characteristics of a 4 GHz-band HTS microstrip-disk filter

We report on the 3rd intermodulation distortion (IMD3) characteristics of high-Tc superconducting (HTS) microstrip TM11-mode disk filters with conventional and proposed resonator-structures for 4GHz-band applications. The electromagnetic simulation results implied that the proposed structure had lower IMD3 than the conventional structures. The experimental filter sample designed with a center frequency (fC) of 4GHz and bandpass characteristic were prepared using YBCO films on the both sides of MgO(100) substrates. As the measurement results around 4GHz band, there is a temperature range for which the IMD3 is less than −50dBc at 10W input power.

An analog compensation method for asymmetric IMD characteristics of power amplifier

The modulation frequency affects the asymmetric intermodulation distortion (IMD) products of a RF power amplifier. This effect reduces IMD cancellation performance of power amplifiers in connection with predistortion linearization. A phase extraction method to determine phase difference between upper and lower third-order IMD products and a phase compensation circuit using an envelope injection technique is proposed. The experimental results demonstrate a significant improvement in the third-order IMD cancellation performance.

DTV 중계기에서의 UHF 전송장치용 구동증폭단의 구현 및 성능평가에 관한 연구

본 논문에서는 UHF(470∼806 MHz) 대역에서 전송장치로 사용 가능한 DTV 중계기용 1 Watt 급 구동증폭단을 설계 및 제작하였다. 구동증폭단은 유전율 2.53, 두께 0.8 mm 기판을 사용하여, 전치증폭기 및 1 Watt 단위증폭기를 단일기판상에 집적화 하였다. 바이어스 전압 28 V DC, 전류 900 mA를 구동증폭단에 인가하였을 때, 470∼806 MHz의 대역에서 53.5 dB 이상의 이득, <TEX>$\pm$</TEX>0.5 dB의 이득 평탄도 및 -12 dB 이하의 입ㆍ출력 반사손실이 나타났다. 또한 출력전력이 1 Watt일 때 사용주파수 대역에서 2 MHz 주파수 간격의 두 신호를 구동증폭단에 입력하여 설계사양보다 우수한 48 dBc 이상의 상호변조왜곡 특성이 나타남을 알 수 있었다. In this paper, a driving amplifier stage with 1 Watt output has been designed and fabricated, which is operating at UHF band( 470 ∼ 806 MHz) for digital TV repeater. In the driving amplifier stage, preamplifier and 1 Watt unit amplifier are integrated by one electric substrate which is 2.53 in dielectric constant and 0.8 mm thickness. When the driving amplifier stage is flown by bias voltage of 28 V DC and current of 900 mA. it has the gain of more than 53.5 dB. the gain flatness of <TEX>$\pm$</TEX>0.5 dB and return loss of less than -15 dB in 470 ∼ 806 MHz. Also, when two signals at 2 MHz frequency interval are input port into the driving amplifier stage with 1 Watt output, it resulted in excellent characteristics to designed specification with showing intermodulation distortion characteristics of more than 48 dBc.

Spurious-free dynamic range characteristics of the photonic up-converter based on a semiconductor optical amplifier

We investigate nonlinear intermodulation distortion characteristics of the photonic up-converter based on a semiconductor optical amplifier for multifrequency signal up-conversion. The third-order intermodulation distortions are measured with two-tone intermediate frequency signals for the photonic up-converter under various conditions. The spurious-free dynamic range is determined to be larger than 72 dB/spl middot/Hz/sup 2/3/.

Prediction of IMD in LDMOS transistor amplifiers using a new large-signal model

In this paper, the intermodulation distortion (IMD) behavior of LDMOS transistors is treated. First, an analysis is performed to explain measured IMD characteristics in different classes of operation. It is shown that the turn-on region plays an important role in explaining measured IMD behavior, which may also give a clue to the excellent linearity of LDMOS transistors. Thereafter, with this knowledge, a new empirical large-signal model with improved capability of predicting IMD in LDMOS amplifiers is presented. The model is verified against various measurements at low as well as high frequency in a class-AB power amplifier circuit.

Intermodulation distortion in pseudomorphic HEMTs and an extension of the classical theory

Pseudomorphic high electron-mobility transistors (pHEMTs) offer superior RF and microwave performance and, in particular, exhibit exceptional intermodulation distortion characteristics that are not adequately modeled by the classical theory. Intermodulation products are typically 8-10 dB below classical expectations, and can be as much as 12 dB lower. An extension of the classical theory is presented, which allows for a better understanding of this phenomenon in terms of the device transconductance characteristic. Experimental data is included to provide quantitative verification based on both device and amplifier results. pHEMT-based devices have the potential to satisfy the spectral performance requirements of today's wireless systems with improved dc-to-RF efficiencies.

Linearity and CNR Improvement Technologies against Optical Reflection inFiber-Oriented Wireless Access Systems

It is important to consider optical reflection conditions when designing fiber-oriented wireless access systems around subcarrier optical transmission since the noise characteristic can be significantly degraded by optical reflection, especially if narrow spectral width devices are used. The superluminescent diode (SLD) offers stable noise and 3rd-order intermodulation distortion (IM3) characteristics that follow the ideal cubic law, even under multiple optical reflection. The SLD-predistorter combination is proposed as a way to overcome the SLD's narrow dynamic range. It is experimentally found that the predistorter reduces IM3 by 8 dB. The receiver sensitivity of a practical system that uses the SLD-predistorter combination is discussed from the viewpoint of overall design. A superimposed subcarrier modulation (SSM) technique is also proposed in order to reduce the reflection noise. We experimentally confirm that the SSM technique reduces the noise degradation and provides stable optical transmission. An SSM design methodology is presented that takes both noise and linearity into account. The SLD-predistorter and the SSM scheme make it possible to realize stable transmission performance and wider dynamic range in the presence of optical reflection.

Linearity and third-order intermodulation distortion in DFB semiconductor lasers

This paper presents a systematic investigation of the third-order intermodulation distortion characteristics in distributed feedback (DFB) semiconductor lasers. The influence of several nonlinearities, such as longitudinal spatial hole burning, gain compression, and relaxation oscillation, is considered. Detailed analysis shows that it is possible to make different nonlinearities cancel one another to give a low intermodulation distortion by choosing the appropriate DFB structure and beat conditions. Specifically, conditions for cancellation between spatial hole burning and gain compression nonlinearities are introduced.

Numerical steady state analysis of electronic circuits driven by multi-tone signals

Characteristics of analogue circuits such as intermodulation distortion and transfer characteristics can often be received from the steady state behavior. This paper presents a unified approach for the simulation of non-autonomous circuits with multi-tone excitation. The steady state is here regarded as the solution of a partial differential-algebraic equation. A suitable numerical method for its solution is a variational method with trigonometric basis functions. The Harmonic Balance technique based either on the multi-dimensional Fourier transformation or the Artificial Frequency Map technique can be interpreted as a special variant of this method.

Analysis of the second- and third-order intermodulation distortion in DFB lasers including dynamic spatial hole burning effect

Analysis of second and third order intermodulation distortion characteristics of semiconductor DFB lasers is, for the first time, performed, including dynamic longitudinal spatial hole burning (LSHB) effect. We have shown theoretically that the third order intermodulation distortion can be lower than the calculated curve without LSHB effect, which is confirmed with experiments.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Intermodulation distortion characteristics of a semiconductor laser amplifier in subcarrier multiplexing

The intermodulation distortion (IMD) characteristics of a subcarrier multiplexed signal in semiconductor laser amplifiers have been calculated. The minimum value of the carrier to the second-order IMD with detuning decreases 3 dB for the amplifier under consideration when the facet reflectivity changes from 10 -4 to 10 -3. In the case of third-order IMD the minimum value of the carrier to IMD ratio with detuning decreases 10 dB for the same change of reflectivity.

Radiation Effects on Distortion Characteristics of Power GaAs MESFET Amplifiers

A nonlinear MESFET model that explains the degradation in power GaAs MESFET amplifier third order intermodulation distortion (IM3) characteristics following neutron irradiation is presented. The model verifies the experimental data and shows that the significant increase in IM3 observed at a neutron fluence of 1.4 × 1015 n/cm2 and higher is mainly due to the non-linearity in device transconductance gm and output conductance go. The model also indicates that IM3 is dominated by the device gm or go non-linearity depending on applied gate bias.

Third-Order Intermodulation Distortion and Gain Compression in GaAs Fet's

A simple unilateral nonlinear circuit model of a GaAs FET is used in the analysis of the third-order intermodulation distortion and gain compression characteristics of a single-stage amplifier. Expressions are obtained for these characteristics, relating them to the input power level and to the device load admittance. The expressions are illustrated with contours on the load admittance plane of constant intermodulation distortion ratio, intercept point gain compression, AM-to-PM conversion, and output power, and as output power versus input power plots for fixed terminations. Agreement with experimentally measured distortion characteristics is good.