Intermodulation Distortion

We demonstrate a novel photonic integrated circuit(PIC) that combines an ultra compact trench beam splitter with monolithically integrated detectors and modulators. A coherent receiver is realized by flip chip bonding of this PIC with an electronic integrated circuit(EIC). Preliminary system results yield an IMD3 distortion suppression of 46dB at a signal frequency of 300MHz. I.

The realization and characterization of Al 0.22 Ga 0.78 As/In 0.22 Ga 0.78 As/GaAs power pHEMT are reported. This structure was optimized to obtain a quasi flat transconductance profile to increase the device linearity near the compression. A maximum single carrier output power higher than 0.8 W/mm for 2 dB compression has been obtained, with more than 30 % power added efficiency and 7.4 dB linear gain at 18.5 GHz. Two tones intermodulation distortion have shown a C/I ratio of 19.9 dBc and 42.3 dBc to the 3 rd and 5 th order respectively, for an input two tones power corresponding to 1 dB compression input power in CW.

This paper presents building blocks for a proposed automotive intermodulation radar for detecting and identifying vulnerable road users (VRUs). The intermodulation radar transmits at two frequencies and it has receivers both for normal reflections and for reflections from VRUs at the intermodulation frequency. A possible radar architecture is presented and modulation techniques are discussed. Different mixing elements of radar reflectors are studied with simulations. An antenna structure enabling a wearable reflector that can be integrated into clothes is designed and characterized. The simulated and measured performance of the radar reflector is used to estimate the achievable detection range.

This paper presents a passive wireless resonating sensor that is based on a ferroelectric varactor. The sensor replies with its data at an intermodulation frequency when a reader device illuminates it at 2 closely located frequencies. The paper derives a theoretical equation for the response of such a sensor, verifies the theory by simulations, and demonstrates a temperature sensor based on a ferroelectric varactor.

Experimental results on the characterization of the linear and nonlinear microwave properties of niobium film produced by UHV cathodic arc deposition are presented. Surface impedance Z s as a function of rf field and intermodulation distortion (IMD) measurement have been carried out by using a dielectrically loaded resonant cavity operating at 7 GHz. The experimental data show that these samples have a lower level of intrinsic nonlinearities at low temperature and low circulating power in comparison with Nb samples grown by sputtering. These results make UHV cathodic arc deposition a promising technique for the improvement of rf superconducting cavities for particle accelerators.

A compressive nonlinearity in the mechanics of the cochlea is responsible for (1) the dynamic detection range of about 120 dB; (2) the level-dependent modification of the ability to detect one tonal component in the presence of another (masking); (3) the stabilization of cochlear self-oscillations, which are associated with sounds broadcast from the ear (spontaneous otoacoustic emissions); and (4) the psychoacoustic detection and detection in the ear canal of frequency components (intermodulation distortion products) not present in the original acoustic signal. The spontaneous otoacoustic emission spectra are characterized by quasi-regular frequency spacings, with some ears having over 30 narrow-band spectral peaks. The intermodulation distortion level is higher than that claimed for mediocre stereo systems and varies with frequency. Several interesting analogies between the modeling of otoacoustic emissions and the sound spectra of musical wind instruments are discussed. [Work supp...

The seismo-acoustic methods are among the most promising emerging techniques for the detection of landmines. Numerous field tests have demonstrated that buried landmines manifest themselves at the surface through resonance and nonlinear responses (or signatures) to acoustic/seismic excitation at the frequencies below 1000Hz. The resonance signatures are primarily due to mine's housing structural resonances. The nonlinear signatures explained by high contact nonlinearity at the mine-soil interface. These phenomena are utilized for landmine detection demonstrating high provability of detection and low false alarms. The paper provides overview of theoretical and experimental investigations conducted by the author and his colleagues at Stevens Institute of Technology. Among major accomplishments are discovery and explanation of mine's resonance behavior; soil/depth effect on buried mine's resonances; discovery and analysis of nonlinear acoustic interactions at the soil-mine interface; development of nonlinear quadratic and intermodulation detection algorithms based on dual-frequency excitation. Work supported by the U.S.Army NVESD, ARO and ONR.

All transmitted signals are to some extent degraded by the environment through which they propagate. Signal degradation can take many forms, but generally it falls into three types: noise, distortion, and attenuation (reduction in power). In order to solve or reduce these errors generated during signal transmission, an M-QAM single-carrier baseband communication system was designed and simulations were made to determine the BER under different SNR. This method of modulation has the advantage of reducing or eliminating intermodulation interference caused by a continuous carrier near the modulation sidebands. Also it will enable data transmission at twice the rate of standard pulse amplitude modulation (PAM) without any degradation in the bit error rate (BER), thereby doubling the effective bandwidth. The numerical results obtained from the Matlab simulink were compared to the theoretical results obtained from the Matlab tool named 'bertool' when QAM orders for 0 / N E b were set at 12.0dB, the new simulated BER's for the different QAM's were obtained. The BER values obtained from both simulation systems were found to be similar.

The seismo-acoustic method is one of the most promising emerging techniques for the detection of landmines. Numerous field tests have demonstrated that buried landmines manifest themselves at the surface through linear and nonlinear responses to acoustic/seismic excitation. The present paper describes modeling of the nonlinear response in the framework of the mass–spring model of the soil–mine system. The perturbation method used in the model allows for the derivation of an analytical solution describing both quadratic and cubic acoustic interactions at the soil–mine interface. This solution has been compared with actual field measurements to obtain nonlinear parameters of the buried mines. These parameters have been analyzed with respect to mine types and burial depths. It was found that the cubic nonlinearity could be a significant contributor to the nonlinear response. This effect has led to the development of a new intermodulation detection algorithm based on dual-frequency exci...

An rf superconducting quantum interference device (SQUID) array in an alternating magnetic field is investigated with respect to its effective magnetic permeability, within the effective medium approximation. This system acts as an inherently nonlinear magnetic metamaterial, leading to negative magnetic response, and thus negative permeability, above the resonance frequency of the individual SQUIDs. Moreover, the permeability exhibits oscillatory behavior at low field intensities, allowing its tuning by a slight change of the intensity of the applied field.

For the implementation of RF tunable components, semiconductor based varactors provide advantages in terms of low control voltage, high capacitance density, low packaging costs, high reliability and technology compatibility. In this paper, an overview is given of the linearization approaches for semiconductor based ultra-linear varactors. Implementation issues regarding the optimum doping profiles are discussed. Design considerations for dedicated bias networks that provide optimum thirdorder intermodulation cancellation for the various varactor configurations are presented. To give an indication of the system-level responses for linear varactors, a varactor-based "true" time delay phase shifter is designed and the system-level linearity parameters, like adjacent channel power ratio (ACPR) and error vector magnitude (EVM), are evaluated for various application conditions.

A simulator for shipboard radio frequency interference, intended to be used in the characterization of UHF satellite communications terminals such as the AN/WSC-3 and AN/SSR-1, has been developed. Analytical results for the performance of various types of communications systems in white gaussian noise is available in the open literature. Performance in other types of channels, such as between a satellite and ship, is not known yet due to un-availability of analytical models for the additive type of interference found in the ship's environment. A physical-statistical model for shipboard inter-ference, based on Middleton's model for urban noise, is given. The model developed incorporates the relevant physical aspects of the various possible interferers and postulates a statistical framework in which these signals are inserted. A simulator based on the developed model was built to serve as a tool for study of the effects of the various interferers upon shipboard satel-lite co...

To meet the modern technological requirements according to the market needs, the device dimensions of the conventional MOSFET are decreasing continuously. The continuous miniaturization of MOSFET at nano scaled regime increases shorts channel effects (SCEs) as well as the fabrication complexity. Due to very high doping requirement and high thermal conditions, the fabrications of the ultra sharp source/drain junctions in nano-scaled MOSFET become more complex. Hence recently a new device, called junctionless transistor [1] has been proposed to alleviate the aforementioned problems. The junctionless nanowire transistors (JLNWT) are uniformly heavily doped throughout the source, channel and drain region and there is no formation of junctions thereby eliminating the problem of the diffusion of the impurities. Although JLNWT shows superior immunity against SCEs and can be scaled to lower channel lengths compared to inversion mode (IM) transistor, but still SCEs are not negligible for suc...

This paper presents a mathematical analysis of a fully differential BD-modulated Class-D amplifier with analog feedback, i.e., one having a bridge-tied-load output configuration with negative feedback and ternary PWM signal. Notwithstanding the highly nonlinear nature of the amplifier's operation, an extremely accurate closed-form expression for the audible output signal is derived and verified based on computer simulations. This expression demonstrates that there exist larger high-order intrinsic distortions (e.g., 5th-order harmonic distortion and intermodulation distortion) for BD-modulation, compared to that for AD-modulation (binary PWM signal). Furthermore, the 3rdorder harmonic distortion has a roughly parabolic response as a function of the magnitude of the input signal and reaches its peak when the modulation index of the input signal is around 0.7. Overall, the BD-modulated Class-D amplifier has a larger intrinsic distortion for small input signal but a smaller intrinsic distortion for large input signal, compared to AD-modulated designs.

This paper presents a time-domain analysis of the intermodulation distortion (IMD) of a closed-loop Class D amplifier with either 1 st -order or 2 nd -order loop filter. The derived expression for the IMD indicates that there exist significant 3 rd -order intermodulation products (3 rd -IMPs) within the output spectrum, which may lead to even greater distortion than the intrinsic harmonic components. In addition, the output expressions are compact, precise and suitable for hand calculation, so that the parametric relationships between the IMD and the magnitude and frequency of the input signals, as well as the effect of the loop filter design, are straightforwardly investigated. In order to accurately represent the IMD performance of Class D amplifiers, a modified testing setup is introduced to account for the dominantly large 3 rd -IMPs when the ITU-R standard is applied.

This paper presents a time-domain analysis of the intermodulation distortion (IMD) of a closed-loop Class D amplifier with either 1 st -order or 2 nd -order loop filter. The derived expression for the IMD indicates that there exist significant 3 rd -order intermodulation products (3 rd -IMPs) within the output spectrum, which may lead to even greater distortion than the intrinsic harmonic components. In addition, the output expressions are compact, precise and suitable for hand calculation, so that the parametric relationships between the IMD and the magnitude and frequency of the input signals, as well as the effect of the loop filter design, are straightforwardly investigated. In order to accurately represent the IMD performance of Class D amplifiers, a modified testing setup is introduced to account for the dominantly large 3 rd -IMPs when the ITU-R standard is applied.

This paper presents a mathematical analysis of a fully differential BD-modulated Class-D amplifier with analog feedback, i.e., one having a bridge-tied-load output configuration with negative feedback and ternary PWM signal. Notwithstanding the highly nonlinear nature of the amplifier's operation, an extremely accurate closed-form expression for the audible output signal is derived and verified based on computer simulations. This expression demonstrates that there exist larger high-order intrinsic distortions (e.g., 5th-order harmonic distortion and intermodulation distortion) for BD-modulation, compared to that for AD-modulation (binary PWM signal). Furthermore, the 3rdorder harmonic distortion has a roughly parabolic response as a function of the magnitude of the input signal and reaches its peak when the modulation index of the input signal is around 0.7. Overall, the BD-modulated Class-D amplifier has a larger intrinsic distortion for small input signal but a smaller intrinsic distortion for large input signal, compared to AD-modulated designs.

This paper describes the designing of a fourth order low-pass lter (LPF) for portable ECG application. The proposed lter is designed by cascading one P-biquad and one N-biquad to form a fourth order lter. It is self-compensated and provides a 0 dB gain. It also acquires the same input and output common mode voltages, which helps to produce higher order lters. It consumes power of 7.2 nW with a supply voltage of 1.2 V. Dynamic range of 68.1 dB with noise of 61.2 µVrms is obtained. The proposed lter is designed for a cut-off frequency of 230 Hz, suitable for ECG application. With 100 Hz frequency and 100 mV pp ac amplitude, HD 3 of 71 dB is achieved. The circuit is simulated in cadence software using Silterra 130 nm CMOS technology. Compared with other state-of-the-art designs, this novel LPF provides the largest dynamic range and the best gure of merit (FOM).

It is critically important in designing RF receiver front ends to handle high power jammers and other strong interferers. Instead of blocking incoming energy or dissipating it as heat, we investigate the possibility of redirecting that energy for harvesting and storage. The approach is based on channelizing a high power signal into a previously unknown circuit element which serves as a passive intermodulation device. This intermodulation component must produce a hysteretic current-voltage curve to be useful as an energy harvester. Here we demonstrate a method by which carbon nanotube transistors produce the necessary hystereticI-Vcurves. Such devices can be tailored to the desired frequency by introducing functional groups to the nanotubes. These effects controllably enhance the desired behavior, namely, hysteretic nonlinearity in the transistors’I-Vcharacteristic. Combining these components with an RF energy harvester may one day enable the reuse of inbound jamming energy for stand...

Two linearization techniques for double-balanced active mixers are introduced in this paper. The proposed techniques are based on cancelling the second-and third-order kernels of the transconductance stage output current. The second-order kernel is cancelled by adding a second-order intermodulation (IM2) current with an opposite sign generated by injecting a first-order term to the transconductance stage and also attenuating the third-order kernel of the transconductance current significantly by an improved form of the IM2 injection method. The proposed mixer has been designed for IEEE 802.11 applications with input frequency and output bandwidth equal to 2.4 GHz and 20 MHz, respectively, and simulated using a 90 nm RF-CMOS technology. Spectre-RF simulation results show that the proposed techniques have simultaneously improved IIP2 and IIP3 by approximately 26.7 dB and 21.4 dB, respectively, while only a 0.2 mA extra current is drawn from a 1.2 V power supply. In addition, the proposed techniques have no effect on the other parameters of the mixer such as the noise figure and conversion gain.

In satellite communication systems, there are high power multichannel transmitters and wideband receivers that have shared RF antenna transmission lines because of: 1) large power level difference between the transmitted and received signal; 2) limited frequency channels. The harmonics and Passive Intermodulation (PIM) Interference will be generated due to passive non-linearities in the high power transmission path. This can be a serious problem. This paper describes how to determine the signal levels and dominant mechanisms that are associated with non-linear dielectric behavior in this context. A novel measurement system for testing dielectric samples is described and measurement results are provided for commonly used microwave dielectrics.

Noncontiguous transmission schemes combined with high power-efficiency requirements pose big challenges for radio transmitter and power amplifier (PA) design and implementation. Due to the nonlinear nature of the PA, severe unwanted emissions can occur, which can potentially interfere with neighboring channel signals or even desensitize the own receiver in frequency division duplexing (FDD) transceivers. In this article, to suppress such unwanted emissions, a low-complexity sub-band DPD solution, specifically tailored for spectrally noncontiguous transmission schemes in low-cost devices, is proposed. The proposed technique aims at mitigating only the selected spurious intermodulation distortion components at the PA output, hence allowing for substantially reduced processing complexity compared to classical linearization solutions. Furthermore, novel decorrelation based parameter learning solutions are also proposed and formulated, which offer reduced computing complexity in parameter estimation as well as the ability to track timevarying features adaptively. Comprehensive simulation and RF measurement results are provided, using a commercial LTE-Advanced mobile PA, to evaluate and validate the effectiveness of the proposed solution in real world scenarios. The obtained results demonstrate that highly efficient spurious component suppression can be obtained using the proposed solutions.

Increasing the flexibility in spectrum access is a key to enhanced efficiency in radio spectrum utilization. Noncontiguous carrier aggregation (CA) is one enabling technology towards more flexible spectrum access, but can also lead to serious implementation challenges in terms of transmitter linearity. Especially when a single power amplifier (PA) is deployed for all carriers, serious intermodulation components will rise which can easily limit the maximum transmit power. In this paper, a low-complexity digital predistortion (DPD) solution is developed to reduce the most critical spurious components at the PA output, opposed to more classical full bandwidth linearization. The developed concept and associated parameter learning and optimization are particularly tailored towards mobile devices, building on limited narrowband feedback receiver with reduced instrumentation complexity and reduced-rate DPD processing. The developed DPD solution can handle PAs with substantial memory effects, and is verified with extensive simulation examples in various non-contiguous carrier aggregation scenarios and practical PA models with memory.

In frequency division duplex transceivers employing non-contiguous carrier aggregation (CA) transmission, achieving sufficient isolation between transmit and receive chains us-ing radio frequency filtering alone is increasingly difficult. Particularly challenging problem in this context is spurious intermodulation (IM) components due to nonlinear power amplifier (PA), which may easily overlap the receiver band. With realistic duplex filters, the residual spurious IM at RX band can be several dBs stronger than the thermal noise floor, leading to own receiver desensitization. In this paper, we carry out detailed signal modeling of spurious emissions due to wideband PAs at the third-order IM band. Stemming from this modeling, and using the known transmit data, we present an efficient nonlinear digital identification and can-cellation technique to suppress the unwanted IM components at RX band. The proposed technique is verified with com-puter simulations, showing excellent calibration ...

We report on the use of strong external optical feedback to enhance the modulation response of semiconductor lasers over a frequency passband around modulation frequencies higher than 60 GHz. We show that this modulation enhancement is a type of photon-photon resonance (PPR) of oscillating modes in the external cavity formed between the laser and the external reflector. The study is based on a time-delay rate equation model that takes into account both the strong feedback and multiple reflections in the external cavity. We examine the harmonic and intermodulation distortions associated with single and two-tone modulations in the mmwave band of the resonant modulation. We show that compared with solitary lasers modulated around the carrier-photon resonance frequency, the present mm-wave modulated signal has lower distortions.

In this paper, an asymmetrical Doherty amplifier fabricated in microstrip technology is tested in the experiments to verify the impact of the 2 nd order signal for the linearization prepared in baseband. The measurement set-up consists of three USRPs programmed by LabVIEW to generate the useful 64QAM signal and the signals for linearization that are set in amplitude and phase and modulate the 2 nd harmonic of fundamental carrier. The USRPs instruments should be synchronized for performing measurements for two scenarios: the signals for linearization are injected at input of the transistor within the main Doherty amplifier or are injected at its output.

In this paper the system for 3 rd order intercept point measurements of RF amplifiers and mixers is presented. "The fragmentary method" which bases on narrow band measurements of fundamentals and 3 rd order products is described. The decreasing of the measurement time and the spectrum analyzer dynamic range improvement method was presented.

This study aims to document the historical conceptualization of the inner ear as the anatomical location for the appreciation of sound at a continuum of frequencies and to examine the evolution of concepts of tonotopic organization to our current understanding. Primary sources used are from the sixth century BCE through the twentieth century CE. Each work/reference was analyzed from two points of view: to understand the conception of hearing and the role of the inner ear and to define the main evidential method. The dependence on theory alone in the ancient world led to inaccurate conceptualization of the mechanism of hearing. In the sixteenth century, Galileo described the physical and mathematical basis of resonance. The first theory of tonotopic organization, advanced in the seventeenth century, was that high-frequency sound is mediated at the apex of the cochlea and low-frequency at the base of the cochlea. In the eighteenth and nineteenth centuries, more accurate anatomical information was developed which led to what we now know is the accurate view of tonotopic organization: the high-frequency sound is mediated at the base and low-frequency sound at the apex. The electrical responses of the ear discovered in 1930 allowed for physiological studies that were consistent with the concept of a high to low tone sensitivity continuum from base to apex. In the mid-twentieth century, physical observations of models and anatomical specimens confirmed the findings of greater sensitivity to high tones at the base and low tones at the apex and, further, demonstrated that for high-intensity sound, there was a spread of effect through the entire cochlea, more so for low-frequency tones than for high tones. Animal and human behavioral studies provided empirical proof that sound is mediated at a continuum of frequencies from high tones at the base through low tones at the apex of the cochlea. Current understanding of the tonotopic organization of the inner ear with regard to pure tones is the result of the acquisition over time of knowledge of acoustics and the anatomy, physical properties, and physiology of the inner ear, with the ultimate verification being behavioral studies. Examination of this complex evolution leads to understanding of the way each approach and evidential method through time draws upon previously developed knowledge, with behavioral studies providing empirical verification.

Abs tract: OFDM have a several attractive features which give many advantages for transmission of fast and reliable data, high spectral efficiency, and easy equalization. During the transmission of this OFDM signal PAPR is a major practical problem involving OFDM modulation. PAPR in signal is usually undesirable because it usually strains the analog circuitry. To overcome this problem constant modulus algorithm is an efficient scheme which can decreases PAPR (Peak to average power ratio) gradually. In this paper, SD-CMA (Steepest Descent constant modulus algorithm) and UC-CMA (Unit circle constant modulus algorithm) are used for the reduction of PAPR. OFDM signals are generated by using these two algorithms and then compared with the originally generated signal the comparison gives an idea for the algorithm more efficient for data transmission with above 90 percent PAPR.

Frequency modulation experiments were performed on a spin torque vortex oscillator for a wide range of modulation frequency, up to 10 % of the oscillator frequency. A thorough analysis of the intermodulation products shows that the key parameter that describes these experiments is the deviation sensitivity, which is the dynamical frequency-current dependence. It differs significantly from the oscillator tunability discussed so far in the context of spin-transfer oscillators. The essential difference between these two concepts is related to the response time of the vortex oscillator, driven either in quasi-steady state or in a transient regime.

Analog predistortion linearizer for the high power amplifier of CDMA base station has been developed. To suppress the spectral regrowth in the adjacent channels effectively, the odd order intermodulation distortions should be cancelled. For the purpose, the predistorter, which can cancel the 3rd and 5th intermodulation distortions independently, has been employed. The implemented predistorter linearized the RF amplifier with average power 45 dBm at 2.37-2.4GHz band. 9dB suppression of spectral regrowth was achieved for CDMA signal over 30MHz bandwidth.

Operational behaviors of the class-F and class-F amplifiers are investigated. For the half-sinusoidal voltage waveform of the class-F amplifier, the amplifier should be operated in the highly saturated region, in which the phase relation between the fundamental and second harmonic currents are out-of-phase. The class-F amplifier can operate at the less saturated region to form a half sinewave current waveform. Therefore, the class-F amplifier has a bifurcated current waveform from the hard saturated operation, but the class-F amplifier operates as a switch at the saturated region for a second harmonic tuned half-sine waveform. To get the hard saturated operation, the fundamental load is very large, more than times larger than that of the tuned load amplifier. The operational behaviors of the amplifiers are explored with the nonlinear output capacitor. Since the capacitor generates a large second harmonic voltage with smaller higher order terms, the class-F amplifier with the nonlinear capacitor can deliver the proper half-sinusoidal voltage waveforms at a lower power, but the effect of the nonlinear capacitor is small for the class-F amplifier. The class-F amplifier delivers the superior performance at the highly saturated operation due to its larger fundamental current and voltage generation at the expense of the larger voltage swing. The simulation results lead to the conclusion that the class-F amplifier with the nonlinear capacitor is suitable topology for high efficiency. However, in the strict sense, the class-F amplifier with the nonlinear capacitor is not the classical class-F amplifier because the voltage-shaping mechanisms and the fundamental load are quite different. We call it the saturated amplifier since the amplifier is the optimized structure of the power amplifier operation at the saturated mode.

A no¨el extractionion method has been proposed for direct extract of the higher order Taylor coefficients of the channel current I d s ( ) ( ) V , V in a GaAs MESFET. Low-frequency 45 and 70 MHz g s d s two-tone signals are employed to measure the harmonic component, and the load impedance was properly designed to find the cross terms. A Volterra series analysis is used for the formulation of Taylor series coefficients of the nonlinear channel current. This proposed parameter extraction procedure is simple and straightforward. The extracted current model is utilized successfully for intermodulation analysis.

Linearisation of a radio basestation amplifier using a third order, a fifth order and a seventh order predistortion scheme is studied. Adaptive predistortion using a third order predistorter improved the amplifier intermodulation distortion (IMD) by between 6.4 dB and 33 dB from the third IMD power level (i.e., maximum power amplitude variation of the IMD), provided by the raw amplifier,

Broad-band high-power cascode AlGaN/GaN high electron-mobility transistor monolithic-microwave integrated-circuit (MMIC) amplifiers with high gain and power-added efficiency (PAE) have been fabricated on high-thermal conductivity SiC substrates. A cascode gain cell exhibiting 5 W of power at 8 GHz with a small-signal gain of 19 dB was realized. A nonuniform distributed amplifier (NDA) based on this process was designed, fabricated, and tested, yielding a saturated output power of 3-6 W over a dc-8-GHz bandwidth with an associated PAE of 13%-31%. A broad-band amplifier MMIC using cascode cells in conjunction with a lossy-match input matching network showed a useful operating range of dc-8 GHz with an output power of 5-7.5 W and a PAE of 20%-33% over this range. The third-order intermodulation products of the amplifiers under two-tone excitation were studied and third-order-intercept values of 42 and 43 dBm (computed using two-tone carrier power) for the lossy match and NDA amplifiers were obtained.

Dit proefschrift beschrijft spontane otoakoestische emissies van mensen en kikkers. Met een gevoelige microfoon, aangesloten op een oor van b.v. een mens, kunnen in veel gevallen zachte fluittoontjes worden geregistreerd. De frequenties van deze spontane otoakoestische emissies liggen doorgaans tussen de 1 en 3 kHz, terwijl het geluidsniveau van emissies rond de gehoordrempel ligt. De meest gangbare opvatting over het ontstaan van een emissie is, dat deze gegenereerd wordt door een actief auditief fllter. Instabiliteit van een dergelijk filter zou de oorzaak zijn van een mechanische oscillatie in het binnenoor, die een akoestische emissie in de gehoorgang tot gevolg heeft. ... Zie: Samenvatting

This paper provides a new theoretical model for the characterization of passive intermodulation behaviour when non-contributing carriers (i.e., carriers which do not directly affect the particular non-linear contribution under analysis) are added to classical two or three carriers scenarios. According to traditional models, the power of a particular passive intermodulation frequency term is only related to the contributing carriers which combines in non-linear way to generate this term, thus the presence of additional (i.e., non-contributing) carriers should not affect to the predicted power of such an intermodulation product. However, recent laboratory tests reveal that non-contributing carriers do reduce the power of unrelated passive intermodulation terms. A heuristic model is proposed in this work to explain this effect, which shows a good matching with measured results already published in the technical literature. The study is focused in third order non-linear contributions, as being the most critical in practical applications.

This paper provides the guidelines for the practical development of novel advanced test beds for passive intermodulation (PIM) measurements. The proposed test beds are highperformance and flexible, allowing for the measurement of several PIM signals of different orders, with two or more input carriers. In contrast to classic test beds for satellite hardware, based on the cascaded connection of several elements, an integrated solution involving the minimum number of hardware pieces is proposed. The result is a lower number of flanged interconnections thus reducing residual PIM level and insertion losses. In addition, return loss degradation and harmful spurious generation in the interconnections are also avoided. Measurement test beds for conducted and radiated PIM, in both transmitted and reflected directions, are discussed, highlighting the benefits and drawbacks of each configuration. Design guidelines for the key components are fully discussed. Illustrative application examples are also reported. Finally, excellent experimental results obtained from low-PIM measurement setups, working from C band to Ka band, are shown, thus fully confirming the validity of the proposed configurations.

In this paper, the generation of passive intermodulation at rectangular waveguide flange bolted connections is investigated. An exhaustive series of tests has been performed in order to provide understanding on the physics lying behind such a phenomenon. In particular, the intermodulation response of the system has been studied as a function of the applied torque to the flange screws. It has been found that, in some situations, the intermodulation response differs from its expected behavior. An interpretation of such discrepancies is given, and practical guidelines for the design of waveguide flanges free of passive intermodulation are provided as well.

This paper presents a broadband linearization technique that can be used for mmWave amplifier circuits. It is based on the well-known principle of derivative superposition, where FETs with different operating points are connected in parallel to generate mutually cancelling third order intermodulation distortion (IM3) products. It is demonstrated by measurements in excess of 10 dB improvement in IM3 obtained from 1 GHz to 30 GHz, practically free by connecting a NMOS with very low gate bias in parallel of an amplifying NMOS. The reasons and limits of the cancellation are discussed. The inherent broadbandness of the technique makes it extremely suitable to be used in CMOS mmWave circuits.

Amplifier nonlinearities affect drastically the performance of OFDM systems. A new carrier allocation method that reduces the intermodulation distortion between different carriers for multiuser OFDM system is presented. Using this allocation technique and transmit beamforming a bit error rate improvement is obtained in a low or medium load system. Comparison of this proposal with Block and Interleaved OFDM allocation methods is performed. Applying the novel allocation technique, the values of Input Back Off (IBO) that can be applied in order to obtain an adequate bit error rate are smaller than with conventional allocation techniques.

The generation of intermodulation distortion products due to the coupling of signals into the output port of an amplifier, often referred to as Reverse Intermodulation Distortion (IMD) can be a major problem when multiple transmitters are operated in close proximity. Such conditions can exist at cell telephone sites, broadcast facilities and even on satellites. This type of distortion can also be a problem when making high linearity measurements. The sensitivity of different types of power amplifiers to Reverse IMD and techniques for mitigating the resulting distortion has been experimentally investigated.

In this article, the harmful radiation level of electric field strength from the hostile low-power radio devices causing the intermodulation interference to the AMPS receiver has been predicted. The predicted level becomes the upper limit to avoid the intermodulation interference on the victim device. Our findings show that the quantified upper limit was 79.13 [dBµV/m] to mitigate the adverse influence from these low-power radio devices. Our results are based on the calculation, simulation, and measurement for the commercial AMPS chip. Resulting values are in a good agreement within less than 3 [dB].

This paper presents the preliminary results from a feasibility study regarding the operation of secondary spectrum users within unused television spectrum. Television spectrum is known within the wireless communications community as being underutilized, making it a prime candidate for dynamic spectrum access. Nevertheless, the quality of this spectrum for enabling secondary transmissions has never been assessed. Two unique scenarios are examined:(i) the possibility of unlicensed devices interfering with digital TV reception, and (ii) the possibility of secondary users experiencing interference when operating within close proximity to television towers. With respect to the former, we investigate the critical operating parameters for developing the technical rules for device operation in bands adjacent to a digital television transmission. Regarding the latter, we examine, via measurement campaign, how non-ideal transmission properties of television broadcasts, including intermodulation and saturation effects, can potentially impair the performance of secondary transmissions.

Linearity is one of the most important characteristics for current and next-generation RF power devices for wireless communication. In this work, linearity of power LDMOS devices is analysed by using a unique harmonic balance device simulator. Sweet-spots in the third order intermodulation distortion product (IM3) are explained and found to be in agreement with measurements and compact modeling. For demonstration of the simulation methodology, a change in the lightly doped drain (LDD) region doping concentration was performed and the effect on linearity was analysed.