CN102594764A - Method for restraining peak-to-average power ratio based on pulse regeneration, and intermediate frequency peak clipping module - Google Patents

Abstract

The invention provides a peak-to-average power ratio suppression method based on pulse regeneration and an intermediate frequency peak clipping module for realizing the method. The present invention performs simple amplitude-limiting processing on the signal at the intermediate frequency, and generates a noise signal for the part exceeding the threshold; then filters the noise signal through modulation and demodulation, thereby obtaining a better filtering effect at a lower implementation cost ; Finally, the noise signal is modulated to the intermediate frequency to perform pulse cancellation with the original signal, so as to realize limiting and peak-cutting and reduce the peak-to-average power ratio of multi-carriers. The invention completes the peak-shaving work of the intermediate frequency signal in a simple and effective manner, and takes into account system performance and resources.

Description

Peak-to-average power ratio suppression method based on pulse regeneration and intermediate frequency peak clipping module

technical field

The invention belongs to the technical field of communication, and in particular relates to a peak-shaving technology for reducing the peak-to-average power ratio.

Background technique

In many current wireless communication systems, such as Wideband Code Division Multiple Access (WCDMA) and Worldwide Interoperability for Microwave Access (WiMAX), the IF signal is usually formed by adding multiple independent baseband signals, and the synthesized IF signal has a large The peak-to-average power ratio (Peak to Average Power Ratio, PAPR), and conform to the Gaussian distribution. The power amplifier (PA) is a nonlinear device widely used in communication systems. Its characteristic is that when the input signal amplitude exceeds its linear region, the output will generate nonlinear distortion, causing signal in-band distortion and adjacent-band signal interference. Therefore The input signal amplitude must be controlled within its linear region. However, the working range of the PA corresponding to the intermediate frequency signal with a large PAPR will be greatly reduced, thereby causing a decrease in PA efficiency. Therefore, it is very important to reduce the PAPR of the IF signal before the PA.

Existing technologies often cannot achieve a good peak clipping effect. For example, some peak clipping techniques, although simple to implement, cannot achieve the required adjacent channel leakage power ratio (ACLR) and error vector magnitude (EVM) due to the spectrum uncertainty caused by the adjustable carrier. In addition, some other methods have complicated implementation process, weak adjustment flexibility, and poor portability.

Contents of the invention

The technical problem to be solved by the present invention is to provide a peak-to-average power ratio suppression method based on pulse regeneration and an intermediate frequency peak clipping module that are easy to implement and have excellent performance.

The technical solution adopted by the present invention to solve the above technical problems is a peak-to-average power ratio suppression method based on pulse regeneration, which is characterized in that it includes the following steps:

Calculate the phase and amplitude modulus of the currently input intermediate frequency signal, and when the amplitude modulus exceeds the threshold, generate a noise signal using the amplitude and corresponding phase of the part exceeding the threshold;

Demodulate the generated noise signal to the baseband for down-sampling and filtering, and then up-sampling and filtering the down-sampled and filtered noise signal to modulate to an intermediate frequency;

The noise signal is subtracted from the delayed original intermediate frequency signal to obtain the intermediate frequency signal after peak clipping.

If the intermediate frequency signal is the addition of multiple baseband signals, the noise signal is first divided into multiple channels with the same number of baseband signals forming the original intermediate frequency signal, and demodulated to the baseband by different local oscillator signals. , carry out down-sampling filter processing, and then perform up-sampling filter processing on the noise signal after down-sampling filtering and then modulate it to the intermediate frequency, and finally add and combine the noise signals modulated to the intermediate frequency by different local oscillator signals to form an intermediate frequency noise signal output .

For realizing the intermediate frequency peak clipping module of said method, it is characterized in that, comprise noise signal generation unit, filtering unit, time delay unit and pulse cancellation unit; The input end of intermediate frequency input signal input noise signal generation unit and the input end of time delay unit , the output end of the noise signal generation unit is connected to the input end of the filter unit, the output end of the filter unit is connected to an input end of the pulse cancellation unit, the output end of the delay unit is connected to the other input end of the pulse cancellation unit, The output terminal of the pulse canceling unit outputs the intermediate frequency signal after peak clipping processing;

The noise signal generation unit is used to calculate the phase and amplitude modulus of the currently input intermediate frequency signal, and when the amplitude modulus exceeds a threshold, the amplitude and corresponding phase of the part exceeding the threshold are used to generate a noise signal;

The filtering unit is used to demodulate the generated noise signal to the baseband for down-sampling and filtering, and then modulate the down-sampling and filtering noise signal to an intermediate frequency after up-sampling and filtering;

The delay unit is used to delay the input signal so that the output original input signal is synchronized with the noise signal output by the filter unit;

The pulse canceling unit is used for subtracting the noise signal from the delayed original intermediate frequency signal to obtain the intermediate frequency signal after peak clipping processing.

Specifically, when the intermediate frequency peak clipping module is applied to a multi-carrier system with adjustable carrier, the filter unit includes several filter subunits, and the filter unit inputs the generated noise signal to each filter subunit, and the filter subunit will generate The noise signal is demodulated to the baseband for down-sampling and filtering processing, and the down-sampling and filtering noise signal is subjected to up-sampling filtering and then modulated to an intermediate frequency. The filtering unit then adds and combines the intermediate frequency noise signals output by each filtering sub-unit. An intermediate frequency signal output is formed; the frequency of the local oscillator signal used for demodulation and modulation is different among the filtering subunits, and the number of filtering subunits in the filtering unit is the same as the number of baseband signals forming the original intermediate frequency signal.

The present invention performs simple amplitude-limiting processing on the signal at the intermediate frequency, and generates a noise signal for the part exceeding the threshold; then filters the noise signal through modulation and demodulation, thereby obtaining a better filtering effect at a lower implementation cost ; Finally, the noise signal is modulated to the intermediate frequency to perform pulse cancellation with the original signal, so as to achieve limiting and peak-cutting and reduce the peak-to-average power ratio of multi-carriers.

The beneficial effect of the invention is that the peak clipping work of the intermediate frequency signal is completed in a simple and effective manner, and system performance and resources are taken into consideration.

Description of drawings

Fig. 1 is a structural diagram of the intermediate frequency peak clipping module of the present invention.

Fig. 2 is a schematic diagram of the limiting unit of the intermediate frequency peak clipping module in the embodiment.

Fig. 3 is a schematic diagram of a filter unit of the intermediate frequency peak clipping module in the embodiment.

Detailed ways

The embodiment includes the following steps in order to realize the process of intermediate frequency peak clipping:

Step 1. After the baseband signal is modulated to the intermediate frequency, it is input to the intermediate frequency peak clipping module, and the intermediate frequency peak clipping module calculates the amplitude modulus and phase of the intermediate frequency signal;

Step 2, the intermediate frequency peak clipping module performs a simple limit judgment on the calculated signal modulus, that is, if the amplitude modulus of the input signal exceeds a given threshold, calculate the part Δx(n) exceeding the threshold; if not If this threshold is exceeded, there is no need to limit it, that is to say, Δx(n) is 0;

Step 3, the intermediate frequency peak clipping module regenerates the noise signal according to Δx(n) and the previously calculated phase, and further, it is necessary to perform gain compensation on the noise signal to obtain the final noise signal x'(n);

Step 4, using the corresponding baseband frame signal to demodulate the noise signal x'(n) to the baseband signal, and perform down-sampling filtering at the baseband to obtain baseband noise that meets the spectrum requirements;

Step 5, the baseband noise is modulated corresponding to the signal of this frame, followed by up-sampling and frequency mixing, and the noise signal is re-modulated to the intermediate frequency;

Step 6: After a certain delay, the intermediate frequency signal originally input to the intermediate frequency peak clipping module is correspondingly subtracted from the filtered intermediate frequency noise signal to obtain the intermediate frequency signal after peak clipping processing.

As shown in Figure 1, the IF peak clipping module mainly includes a noise signal generation unit, a filter unit, a delay unit and a pulse cancellation unit. The intermediate frequency input signal is input to the input end of the noise signal generating unit and the input end of the delay unit, the output end of the noise signal generating unit is connected to the input end of the filtering unit, and the output end of the filtering unit is connected to an input end of the pulse cancellation unit, The output terminal of the delay unit is connected with the other input terminal of the pulse canceling unit, and the output terminal of the pulse canceling unit outputs the intermediate frequency signal after peak clipping processing.

Take the signal with variable carrier and four different carriers as an example. The baseband signal generates different local oscillator signals according to its different carrier frequencies; after baseband demodulation and modulation, four intermediate frequency signals with different carriers are synthesized and one intermediate frequency signal is input to the intermediate frequency peak clipping module.

After the noise signal generation unit receives the input intermediate frequency signal, it performs a simple limit judgment on the synthesized intermediate frequency signal. As shown in Figure 2, the noise signal generation unit mainly includes a calculation unit for modulus and phase, an amplitude comparison unit and a pulse regeneration calculation unit. First calculate the signal modulus and signal phase of the four-way synthesized intermediate frequency signal. On the one hand, compare the calculated signal modulus with the preset peak threshold, if the signal modulus exceeds the peak threshold, calculate the difference between the two, and record the part exceeding the threshold as Δx(n) ; If the signal modulus value does not exceed the peak threshold, there is no need to limit, and Δx(n) can be considered as 0. On the other hand, according to the obtained Δx(n) and the previously calculated signal phase after a certain delay, it enters the pulse regeneration calculation unit, and recalculates the noise signal x'(n) to realize pulse regeneration. Preferably, in order to ensure the peak clipping effect, gain compensation is performed on x'(n).

Afterwards, the noise signal x'(n) respectively enters four different sub-filtering units with different carriers. The structural diagram of the sub-filter module is shown in Figure 3, mainly including a demodulation module and a modulation module. Among them, the demodulation module and the modulation module can be designed according to the demodulation and modulation of the corresponding baseband processing, and the technology is mature, the design is simple, and the complexity of the system is reduced. In the embodiment of the present invention, the local oscillator signal modulated and demodulated by baseband is used, and the carrier frequency of each signal is different, so as to realize the flexible control of the multi-carrier intermediate frequency peak clipping module with adjustable carrier.

The sub-unit of one filter unit is taken as an example for illustration. x'(n) first enters the demodulation module for frequency mixing and down-conversion filtering. The demodulator mixes x'(n) with the local oscillator signal to move to different frequency points, and the local oscillator signal used in modulation is the local oscillator signal when demodulated by the delayed baseband. Then, a certain multiple of downsampling and low-pass filtering are used for the multiplied output signal. The reason why downsampling is considered from the perspective of easy realization of the low-pass filter and resource conservation is to obtain a baseband that meets the spectrum requirements. noise. Next, this noise signal enters the modulation block, where it is re-modulated to an intermediate frequency. Similarly, the modulation module is basically the same as the baseband modulator, and the signal is up-sampled and filtered by a corresponding multiple, and finally mixed with the local oscillator signal used by the demodulation module. At this time, after filtering, it can be ensured that the obtained noise IF signal meets the spectrum requirement in the frequency domain, and at the same time, preparations are made for reducing the peak-to-average power ratio.

Finally, the four processed noise intermediate frequency signals are added and combined to form one intermediate frequency signal. At the same time, pulse cancellation processing is performed between it and the original intermediate frequency signal after a certain delay processing, so as to achieve the purpose of reducing the peak-to-average ratio. Compared with the existing intermediate frequency part, the signal passed through the intermediate frequency peak clipping module here not only meets the spectrum requirements, but also can significantly improve the peak-to-average ratio of the output signal. Obviously, since noise signal generation and filtering processing require a certain time delay, the delay amount of the original input intermediate frequency signal can be determined by multiple simulations.

Compared with the prior art, the intermediate frequency peak clipping module of the embodiment of the present invention is more suitable for multi-carrier systems with adjustable carriers, and effectively reduces the peak-to-average power ratio of signals at intermediate frequencies.

Of course, the present invention can also have other various embodiments, and those skilled in the art can make various corresponding changes and deformations according to the present invention without departing from the spirit and essence of the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (5)

1. the method for restraining peak average power ratio based on pulse regneration is characterized in that, may further comprise the steps:

Calculate the phase place and the amplitude mould value of the intermediate-freuqncy signal of current input,, then utilize the amplitude and the corresponding phase place generted noise signal that exceed the threshold value part when amplitude mould value surpasses threshold value;

The noise signal that generates is demodulated to base band falls sampling filter and handle, more filtered noise signal is carried out rising and be modulated to intermediate frequency after sampling filter is handled;

Original intermediate-freuqncy signal after the time-delay is deducted noise signal, obtain the intermediate-freuqncy signal after peak clipping is handled.

2. a kind of according to claim 1 method for restraining peak average power ratio based on pulse regneration; It is characterized in that, if intermediate-freuqncy signal is that the addition of multichannel baseband signal forms, when carrying out Filtering Processing; Earlier noise signal is divided into and the identical multichannel of baseband signal quantity that forms original intermediate-freuqncy signal; Be demodulated to base band by different local oscillation signals respectively, fall sampling filter and handle, will fall noise signal behind the sampling filter again and carry out rising and be modulated to intermediate frequency after sampling filter is handled; To be modulated to the noise signal phase adduction road of intermediate frequency at last through different local oscillation signals, form the output of one road mid-frequency noise signal.

3. the intermediate frequency peak-clipping module is characterized in that, comprises that noise signal generation unit, filter unit, delay unit and pulse offset the unit; The input of intermediate frequency input signal input noise signal generation unit and the input of delay unit; The output of noise signal generation unit links to each other with the input of filter unit; The output of filter unit links to each other with the input that pulse offsets the unit; The output of delay unit links to each other with another input that pulse offsets the unit, and pulse offsets the output of unit and exports the intermediate-freuqncy signal after peak clipping is handled;

Said noise signal generation unit is used for, and calculates the phase place and the amplitude mould value of the intermediate-freuqncy signal of current input, when amplitude mould value surpasses threshold value, then utilizes the amplitude and the corresponding phase place generted noise signal that exceed the threshold value part;

Said filter unit is used for, and the noise signal that generates is demodulated to base band falls sampling filter and handle, and will fall noise signal behind the sampling filter again and carry out rising and be modulated to intermediate frequency after sampling filter is handled;

Said delay unit is used for, and input signal is carried out delay process, and the noise signal of the original input signal of feasible output and filter unit output is synchronous;

Said pulse offsets the unit and is used for, and the original intermediate-freuqncy signal after the time-delay is deducted noise signal, obtains the intermediate-freuqncy signal after peak clipping is handled.

4. like the said intermediate frequency peak-clipping module of claim 3; It is characterized in that; When the intermediate frequency peak-clipping module was applied to the adjustable multicarrier system of carrier wave, said filter unit comprised that some filtering subelements form, and filter unit is with each the filtering subelement of noise signal input that generates; Said filtering subelement is demodulated to base band with the noise signal that generates and falls the sampling filter processing; To fall filtered noise signal and carry out rising and be modulated to intermediate frequency after sampling filter is handled, filter unit closes the road with the mid-frequency noise signal plus after each filtering subelement output again, forms the output of one tunnel intermediate-freuqncy signal; The frequency that realizes demodulation, the employed local oscillation signal of modulation between each filtering subelement is different, and the number of filtering subelement is identical with the baseband signal quantity that forms original intermediate-freuqncy signal in the filter unit.

5. like the said intermediate frequency peak-clipping module of claim 3, it is characterized in that the local oscillation signal that the local oscillation signal that demodulation in said some filtering subelements, modulation are used uses for the base band demodulating after delaying time, modulation.

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