Search the leading research in optics and photonics applied research from spie journals, conference proceedings and presentations, and ebooks. Cross modulation normally arises out of imperfect mixer performance in the radio, although it can easily occur in one of the rf amplifiers. In the presence of strong blocker interference signals, such nonlinearities introduce severe cross modulation over the desired signals. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. This digital electronics is based on the use of three key elements. Basic digital predistortion techniques for nonlinear distortion in sdr duration. This paper investigates how the crossmodulation distortion can be compensated for by using digital signal. Radio frequency rf power amplifiers pas represent the most challenging design parts of wireless transmitters. Signal processing for rf distortion compensation in.
In digital modulation, an analog carrier signal is modulated by a discrete signal. Mikhemar m, sayed ah 2009 digital compensation of crossmodulation distortion in softwaredefined radios. Considering the continuous increase of digital computation power governed by moores law an attractive alternative approach is to digitally compensate for the cm distortion. De10303055a1 fet amplifier with temperature compensation. Rf and digital signal processing for softwaredefined radio.
The amplitude of each sample in the crosscorrelation signal is a. This study highlights the current and futuristic trends in the arena of transmitter system modelling and digital domain compensation for radio frequency distortions of nonlinear power amplifiers and wireless transmitters in case. Klumperink, senior member, ieee, and bram nauta, fellow, ieee abstracta softwaredefined radio sdr receiver with improved robustness to outofband interference obi is presented. To define the parameters and conditions correctly, the cross modulation specification must include the percentage of modulation of the interfering signal. Digitally enhanced softwaredefined radio receiver robust to outofband interference zhiyu ru, member, ieee, niels a. High speed data converters have been used in communications applications for many years and can be found in much of the equipment that forms the basis of our connected world, from cellular telephone base stations to cable headend equipment to radar and specialized. Basics of software defined radios iitr recommended for you.
The obtained results show that distortions can be suppressed significantly. To avoid the performance challenges caused by nonlinearities and distortion, modern measurement techniques can help engineers understand the device mechanics that cause them. Zou et al digital compensation of crossmodulation distortion in softwaredefined radios 351 making the interference term comparable to the desired signal component. Digitally enhanced softwaredefined radio receiver robust. An ldmosfet 1, the source of which is grounded and to which a gate voltage vgs from a gate bias terminal 3 via a temperature compensation circuit 2 and a choke coil and a drain voltage vts from a drain bias terminal 4 via. Sigma delta modulation, software defined radio, rfid, hbridge.
When this large interference passes through the inherently nonlinear receiver frontend fe, distortion products are generated. Rouphael amsterdam boston heidelberg london new york oxford paris san diego san francisco singapore sydney tokyo newnes is an imprint of elsevier. Radio frequency rf power amplifiers pas represent the most challenging\ud design parts of wireless transmitters. Owing to the small size of the transceiver, the transmitter for one standard induces a large interference on the receiver for another one. This paper investigates how the crossmodulation distortion can be compensated for by using digital signal processing techniques. All of these choices are correct the interfering signal sounds like ac hum on an am receiver or a carrier modulated by 60 hz hum on a ssb or cw receiver, the interfering signal may drift slowly across the hf spectrum, the interfering signal can be several khz in width and usually repeats at regular intervals across a hf band. In order to be more energy efficient, pas should\ud operate in nonlinear region where they produce distortion that significantly degrades the\ud quality of signal at transmitters output. In the presence of strong blocker interference signals, nonlinearities introduce severe cross modulation over the desired signals. Advanced digital signal processing techniques for compensation of. The displayed performance was obtained without digital compensation of the baseband data. Baseband compensation principles for defects in quadrature. Using software defined radio by pu and wyglinski artech house, 20. The proposed receiver structure is based on the adaptive interference cancellation ic using an adaptive algorithm such as a leastmeansquare lms.
Digital signal processing techniques are used to alleviate nonlinear distortions in. An fet amplifier is provided that minimizes the deterioration in distortion sensitivity due to fluctuations in the ambient operating temperature. Axell e, leus g, larsson eg, poor hv 2012 spectrum sensing for cognitive radio. In the presence of strong blocker interference signals, such nonlinearities introduce severe cross modulation over. Elimination of crossmodulation distortion in a radio frequencyamplified intensitymodulation directdetection analog photonic link xiaodong liang, feifei yin, yitang dai, jianqiang li, kun xu. The individual component of proposed fm modulator and demodulator has been optimized in such a way that the overall design consists of a highspeed, area optimized and lowpower features. Compensation of timedivision multiplexing distortion in. Software defined radios are increasingly used in modern communication. Signal processing for rf distortion compensation in wireless communication systems. Transmitter digital domain linearisation solutions are constantly evolving to extract optimum benefits in terms of cost, performance and flexibility.
This book describes softwaredefined radio concepts and design principles from the perspective of rf and. Softwaredefined radio for engineers analog devices. Performance analysis on the selfmixed interference. After compensation in the digital domain, the downconverted xmd and imd3 distortions are experimentally suppressed with 33 db and 25 db, respectively, resulting in. Digitally enhanced softwaredefined radio receiver robust to out. Digital compensation of cross modulation distortion in software defined. To measure the effects quantitatively, the effective signaltonoise ratio snr in is computed as 4 see the equation at the bottom of the page. Power efficient adaptive mitigation of local interference. As it is a third order effect, a receiver with a good third order intercept point should also exhibit good cross modulation performance. Digital compensation of rf nonlinearities in softwaredefined radios the wideband rf receiver in a softwaredefined radio sdr system suffers from the nonlinear effects caused by the frontend analog processing.
The tunable oscillator and mixer are used to selectively downconvert the signal in a desired frequency band. This results in less gain required in the subsequent stages of the radio. Digital compensation of crossmodulation distortion in softwaredefined radios. Digital linearization of multicarrier rf link with. In order to be more energy efficient, pas should operate in nonlinear region where they produce distortion that significantly degrades the quality of signal at transmitters output. In this dissertation, digital signal compensation schemes for the signal distortion due to radio frequency rf components, timing jitter, and baseband. Digital compensation of rf nonlinearities in softwaredefined radios qiyue zou, mohyee mikhemar, and ali h. In a multimode transceiver, several communication standards may be active at the same time. A softwaredefined radio system is a radio communication system where. Softwaredefined radio sdrbased rf frontend transmitters and.
Digital compensation of rf nonlinearities in software. In the presence of strong blocker interference signals, such nonlinearities introduce severe cross modulation. Index terms digital frontend, wideband receiver, iip3, adc requirements, rf frontend, softwaredefined radio, iq imbalance compensation, cross modulation. Cross modulation is the amount of amplitude modulation which is transferred from an offchannel and unwanted signal to the required one being received. Woodward, predistortion compensation of nonlinearities in. Abstractthe wideband rf receiver in a softwaredefined radio sdr system suffers from the nonlinear effects caused by the frontend analog processing. With the aim of reducing this distortion and improve signal quality, digital predistortion. The reference signal for the adaptive ic is obtained from the received signal itself. The emphasis is largely directed towards radio communications, yet many of the principles are directly applicable to other fields of application. Compensation of timedivision multiplexing distortion in switched antenna arrays with a single rf frontend and digitizer abstract. Digital compensation of crossmodulation distortion in softwaredefined radios abstract. Digital compensation of crossmodulation distortion in softwaredefined radios q zou, m mikhemar, ah sayed ieee journal of selected topics in signal processing 3 3, 348361, 2009. Digital compensation of crossmodulation distortion in softwaredefined radios abstractthe wideband rf receiver in a softwaredefined radio sdr system suffers from the nonlinear effects caused by the frontend analog processing.
Based on forward distortion information acquisition and post digital signal processing dsp, we propose and demonstrate a novel scheme to effectively suppress the thirdorder intermodulation distortion imd3 and crossmodulation distortion xmd in a channelized rf photonic link. Digital polar transmitter amam and ampm distortion 80. Digital compensation of rf nonlinearities in softwaredefined radios conference paper in acoustics, speech, and signal processing, 1988. Digital predistortion of rf amplifiers using baseband. Therefore, the degree of effective amplitude modulation in a system will affect some distortion parameters.
Crossmodulation distortion xmd is a specific type of intermodulation between two. In the proposed solution, the sdr scans the wide spectrum and locates the desired signal and strong blocker signals. An existing solution to compensate for the cm distortion is tailored to singlemode transceivers and requires an auxiliary fe. Switched antenna arrays in which a single rf frontend and a single digitizer are used to perform digital array processing are considered in this communication.
Compensation of crossmodulation distortion in multimode. You are right, the term cross modulation usually means modulating an audio signal maybe the pitch of an osc, maybe the amplitude of a waveform through a vca, whatever with another signal that is also in the audio range, as opposed to modulating an audio signal with a nonaudiorange control signal like an lfo or envelope generator. This paper discusses digital postprocessing compensation of such unintentional clipping in multiband ofdma receivers. This paper deals with an fpga implementation of a high performance fm modulator and demodulator for software defined radio sdr system. A broadband iq modulator for broadband radio designs.
In modern wideband communication receivers, the large inputsignal dynamics is a fundamental problem. Spectrum sensing, measurement, and modeling springerlink. Top methods for measuring 5 common signalcorrupting distortions. Top methods for measuring 5 common signalcorrupting. Unintentional signal clipping occurs, if the receiver frontend with the analogto digital interface cannot respond to rapidly varying conditions. The wideband rf receiver in a softwaredefined radio sdr system suffers from the nonlinear effects caused by the frontend analog processing. Cross modulation in radio receivers radioelectronics. In commercial or military software defined radios sdrs, it is urgent to.
Digital compensation of crossmodulation distortion in. Digital compensation of crossmodulation distortion in software. Understand the rf and digital signal processing principles driving softwaredefined radios. Request pdf digital compensation of rf nonlinearities in softwaredefined radios the wideband rf receiver in a softwaredefined radio sdr system suffers from the nonlinear effects caused by. Cognitive radio, software defined radio, nonlinear distortion, interference cancellation. Digital signal processing techniques are used to alleviate non linear distortions in. Digital compensation schemes for signal distortion in ofdm. Nonlinear interference suppressor for lte receiverin. The signal distortion compensation in the digital domain brings more scalability and. Softwaredefined radio sdr technology is a configurable, low cost, and power efficient solution for multimode and multistandard wireless designs. This book describes softwaredefined radio concepts and design principles from the perspective of rf and digital signal processing as performed within this system. Zou et al digital compensation of crossmodulation distortion in softwaredefined radios 349 fig. Request pdf digital compensation of crossmodulation distortion in softwaredefined radios the wideband rf receiver in a softwaredefined radio sdr. Mitigating rf frontend nonlinearity of sensor nodes to enhance.
Introduction software defined radio sdr represents a. The simultaneous distortion compensation capacity is studied numerically, and suppression of. Digital compensation of crossmodulation distortion in softwaredefined radios article in ieee journal of selected topics in signal processing 33. The wideband rf receiver in a softwaredefined radio sdr system suffers from the nonlinear effects caused by the frontend analog. Wideband receiver for a space software radio application. A systemlevel approach to mitigate nonlinear distortions in the digital domain. The high oip3 of the adl5385 iq modulator enables it to achieve high output power levels with minimal adjacent channel leakage. The modulator and demodulator contain an optimized direct digital. Some amount of this distortion is inevitable in any system where modulation causes amplitude changes. Iterative signal processing for mitigation of analogto. The performance of those never seems to live up to the hype.
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