Analysis and practical performance of a difference frequency technique for improving the multicarrier IMD performance of RF amplifiers

Modeste, M.; Budimir, D.; Moazzam, M.R.; Aitchison, C.S.

doi:10.1109/mtttwa.1999.755128

Cited by 20 publications

(20 citation statements)

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“…Analog RF predistortion is simple, low cost to implement and having a much wider bandwidth, so it is more suitable than digital predistortion for base station HPAs. An RF predistorter has a distortion characteristic complementary to that of the RF HPA [1,2] and can be implemented by generating either the harmonicfrequency signals [1,3,4] or the inband intermodulating (IM) products [5][6][7][8][9] and then adding to the original signal at the input of the HPA. The harmonic-frequency technique has an advantage of low insertion loss [4], but the bandwidth of the HPA may block the high-order harmonic-frequency signals, making the technique less useful for high frequency systems.…”

Section: Iintroductionmentioning

confidence: 99%

“…using the differencefrequency signal or the sum-frequency signal, to generate the inband IM products for HPA predistortion [5,6]. In [5], a diode was used as a nonlinear device to generate the difference-frequency signal. However, for HPAs operating in the microwave frequency band, the difference-frequency signal will be out of the HPA operation frequency band and thus blocked.…”

Section: Iintroductionmentioning

confidence: 99%

“…In general, there are two ways, i.e. using the differencefrequency signal or the sum-frequency signal, to generate the inband IM products for HPA predistortion [5,6]. In [5], a diode was used as a nonlinear device to generate the difference-frequency signal.…”

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confidence: 99%

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A simple and effective RF predistorter for use in the HPAs of base stations in cellular mobile systems

Xiao¹,

Cheung²,

Yuk³

2008

2008 11th IEEE Singapore International Conference on Communication Systems

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This paper presents the design of using a simple mixer circuit, constructed with Schottky diodes as the nonlinear device, to generate the intermodulation (IM) products for predistortion of high-power amplifiers (HPAs) in the base stations of cellular mobile systems. The design has a simple structure and requires no external dc bias voltage. A complex polynomial is used to model the characteristic of the HPA and the predistorter generates the in-phase and quadrature components of the intermodulation distortion (IMD) products for predistortion of the HPA. Experimental results using a practical HPA show that, for a modulated CDMA (IS-95) signal, the predistorter can reduce the adjacent-channel-power ratio (ACPR) by 15 dB.Index terms Adjacent-channel-power ratio (ACPR), High Power Amplifier, Inter-modulation, Mixer, RF Analog Predistorter. I.INTRODUCTIONThe current mobile radio systems such as the GSM-EDGE, CDMA (IS-95) and 3G require the RF high power amplifiers (RF HPAs) in the base stations to be broadband and have linear amplification. However, due to the inherent nature of RF HPAs (even with class-A or class-AB configurations), the amplification processes are always nonlinear, so some sorts of linearization techniques need to be used in the base station HPAs of these mobile systems. Analog RF predistortion is simple, low cost to implement and having a much wider bandwidth, so it is more suitable than digital predistortion for base station HPAs. An RF predistorter has a distortion characteristic complementary to that of the RF HPA [1, 2] and can be implemented by generating either the harmonicfrequency signals [1,3,4] or the inband intermodulating (IM) products [5-9] and then adding to the original signal at the input of the HPA. The harmonic-frequency technique has an advantage of low insertion loss [4], but the bandwidth of the HPA may block the high-order harmonic-frequency signals, making the technique less useful for high frequency systems. In general, there are two ways, i.e. using the differencefrequency signal or the sum-frequency signal, to generate the inband IM products for HPA predistortion [5,6]. In [5], a diode was used as a nonlinear device to generate the difference-frequency signal. However, for HPAs operating in the microwave frequency band, the difference-frequency signal will be out of the HPA operation frequency band and thus blocked. In [6], two wideband double-balanced mixers capable of operating at twice of the maximum frequency were used to generate the sum-frequency signal in order to generate the IM3 signals. But it is not easy to handle signals with such high frequency, particularly when generating the IM products with higher orders for intermodulation distortion (IMD) products cancellation.This paper proposes to use mixers as the nonlinear devices to generate the inband IM products for RF HPA predistortion and presents the design of a simple mixer circuit to generate the 3 rd -order intermodulation (IM3) products for 3 rd -order IMD cancellation. The mixer circuit employs two mixers c...

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Section: Iintroductionmentioning

confidence: 99%

Section: Iintroductionmentioning

confidence: 99%

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A simple and effective RF predistorter for use in the HPAs of base stations in cellular mobile systems

Xiao¹,

Cheung²,

Yuk³

2008

2008 11th IEEE Singapore International Conference on Communication Systems

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“…The second harmonic of the input spectrum can be applied to the amplifier input, together with the signal to be amplified [2]. Alternatively, the frequency difference between a set of equally spaced input tones can be applied to the amplifier input, together with the signal to be amplified [3]. Details are given below of the theory, simulation predictions, and bench experiments.…”

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confidence: 99%

Improvement of third-order intermodulation product of RF and microwave amplifiers by injection

Aitchison

Mbabele

Moazzam

et al. 2001

IEEE Trans. Microwave Theory Techn.

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101

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Abstract-This paper discusses the improvement in the third-order intermodulation product (IM3) performance obtainable from RF and microwave amplifiers by two alternative injection techniques. The first is the addition to the amplifier input of the second harmonics of the input spectrum and the second is the addition to the amplifier input of the difference frequencies between the spectral components of the input signal. Both techniques are considered in theory, by simulation and in practice. Both techniques give useful improvements in two-tone IM3 performance. The second harmonic technique reduced the IM3 level by 43 dB in an amplifier at 835 MHz. The difference-frequency technique gave a reduction of 48 dB in an amplifier at 880 MHz. The difference-frequency technique also gives a greater improvement for complex spectra signals.

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“…Previous theoretical and experimental work have demonstrated that injection of the second harmonic of the signal input components into the gate, with the correct phase and amplitude can improve the 2-tone intermodulation performance [2], [3]. Alternatively injection of the frequency separation between the tones of the 2-tone input signal (here referred to as the difference frequency) also improves the 2-tone intermodulation performance [3], [4], [5].…”

Section: Introductionmentioning

confidence: 99%

A simple technique for improving the IM3/C and PAE performance of MESFET amplifiers

Wong¹,

Aitchison²

33rd European Microwave Conference Proceedings (IEEE Cat. No.03EX723C)

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-This paper shows by simulation that a shunt short -circuited /4 line placed across the drain terminals of a microwave MESFET amplifier significantly improves both the IM3/C and 2-tone PAE performance by a maximum of 14dB and 3%(from 24.5% to 27.5%), respectively. Practical confirmation with both WCDMA and GSM-EDGE input signals is obtained with a microstrip amplifier at 2GHz demonstrating an average improvement in ACPR of 12.5dB and a reduction in EVM from 5.0% to 1.3% respectively. The technique is novel, simple and practical and will be of direct interest to designers of base station amplifiers.

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Analysis and practical performance of a difference frequency technique for improving the multicarrier IMD performance of RF amplifiers

Cited by 20 publications

References 3 publications

A simple and effective RF predistorter for use in the HPAs of base stations in cellular mobile systems

A simple and effective RF predistorter for use in the HPAs of base stations in cellular mobile systems

Improvement of third-order intermodulation product of RF and microwave amplifiers by injection

A simple technique for improving the IM3/C and PAE performance of MESFET amplifiers

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