CN100344166C

CN100344166C - Modulation demodulation method and device

Info

Publication number: CN100344166C
Application number: CNB031218784A
Authority: CN
Inventors: 朱静宁
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2003-04-16
Filing date: 2003-04-16
Publication date: 2007-10-17
Anticipated expiration: 2023-04-16
Also published as: CN1538762A

Abstract

The present invention puts forward a modulation and demodulation method suitable for the envelope elimination and restoration technology, and a device for realizing the method. The method is suitable for the envelope elimination and restoration technology, and comprises the following steps: carrying out difference operation for input signals to obtain increment signals; carrying out pulse width modulation for the increment signals to obtain a three-level signal; obtaining a demodulation and restoration signal by carrying out integral operation for a signal obtained by amplifying the three-level signal. The present invention can enhance the linearity of modulation and demodulation signals, and reduce the requirements and the realization difficulty of devices.

Description

A kind of modulation-demo-demodulation method and device

Technical field

The present invention relates to moving communicating field, relate in particular to the modulation-demodulation technique field in the moving communicating field.

Technical background

Envelope is eliminated and recovery (Envelope Elimination and Restore, EE﹠amp; R) technology is a kind of radio frequency high efficiency linearization technology, can be used for radio frequency amplifier or complete linear transmitter.Adopt EE﹠amp; R technology and switching amplifier are realized a kind of high efficiency, the scheme of wide-band linearity power amplifier cheaply, it is the focus of industry research of communicating by letter at present, can make base station/terminal equipment use the less demanding high frequency power device of linear properties just can satisfy broadband power amplifier linearity index request, thereby reduce the cost of base station equipment significantly.

So-called EE﹠amp; The R technology is meant that a signal transforms to polar coordinate system earlier, is decomposed into amplitude and phase place two parts.Respectively amplitude and phase place are amplified, merge the process that reverts to original signal then.EE﹠amp; The principle of R power amplifier as shown in Figure 1.

At first, input signal is decomposed into amplitude and phase place two parts of signals.The amplitude tributary signal is through ovennodulation, amplification, and phase signal is called the radio-frequency carrier signal of being with phase information through phase modulation, and amplitude and carrier wave synthesize the radio frequency output signal at main power amplifier.

Wherein, the amplitude modulation(PAM) of amplitude branch road has several different methods.EE﹠amp; What use always among the R is that (these two kinds of modulation techniques respectively have its characteristics for Pulse Wide Modulation, PWM) method and increment (Delta) modulator approach in pulse width modulation.

The main thought of increment (Delta) modulation technique is to use the notion that difference quantizes, and principle as shown in Figure 2.Sampling point before and after the input signal is carried out calculus of differences, if increment then encodes+1 for just, if increment then encodes-1 for negative.Demodulation is only to need the signal integration that adds up is got final product.This is a kind of 2 level codings, realizes simple.But be guaranteed performance, sampling rate must be very high.Here quantization step square D fixes, thereby is called the linear incremental modulation again.

As shown in Figure 3, the D of linear incremental modulation is constant, thereby when sampling rate was not high enough, more accurately reflected signal ground changed.When the signal variation is very fast, obtain the variation that the ground prediction signal may not catch up with original signal after the demodulation, cause overload.In addition, when signal amplitude descends, quantize signal to noise ratio and descend.Therefore fixed quantisation terrace linear incremental modulating performance is relatively poor.

The width that PWM is meant the sampled value control impuls carrier wave that utilizes modulation signal is linear change thereupon, and that pulse amplitude keeps is constant.Simply, be with certain frequency output duty cycle and the linear continuous impulse of input signal, signal amplitude information is converted to pulse width information.

Fig. 4 is the legend and the parameter schematic diagram of PWM modulation.

The PWM modulation needs two input parameters: pulse frequency and pulse duty factor.Wherein, pulse frequency is similar to sampling frequency, influences the bandwidth of whole PWM passage; Pulse duty factor, the quantization error after the similar sampling of its precision.

The PWM modulation is a kind of non-linear modulation mode, can produce the abundant high order harmonic component, and the baseband portion signal also has to a certain degree distortion.For improving the linearity of PWM modulation and demodulation, need very high sampling rate.Even like this, the low-pass filtering method that usually adopts in the digital power amplifier is recovered modulated signals, and its linearity is still not ideal enough.

Summary of the invention

Purpose of the present invention is exactly to propose a kind of modulation-demo-demodulation method in envelope elimination and the recovery technology and device of realizing this method of being applicable to, can improve the linearity of modulation-demodulation signal, reduces requirement on devices and realizes difficulty.

A kind of modulation-demo-demodulation method is applicable to envelope elimination and recovery technology (Envelope Elimination andRestore, EE﹠amp; R) in, may further comprise the steps:

A, input signal x (t) is carried out calculus of differences, obtain increment signal d (t);

B, (Pulse Wide Modulation PWM), obtains a three level signal y (t) through pulse width modulation with increment signal d (t);

C, described three level signal y (t) is amplified, obtain signal y ' (t);

D, signal y ' obtain demodulation (t) through integral operation, recover to obtain signal x ' (t).

Step a further comprises input signal x (t) is divided into the two-way same signal, and wherein one road signal obtains signal x (t-τ) through delay process, and signal x (t) and signal x (t-τ) subtract each other, and obtain increment signal d (t).

A kind of device of realizing above-mentioned modulation-demo-demodulation method, comprise a time delay module, a subtracter, a PWM modulator, an amplifier, an integrator, described time delay module is done delay process to the road signal that input signal x (t) tells, described subtracter sends to described PWM modulator after input signal x (t) and time delayed signal x (t-τ) are subtracted each other, signal after the modulation amplifies through described amplifier, send to described integrator, obtain demodulation.

Described amplifier can be made up of two Switch amplifiers.

The present invention is in conjunction with the advantage of delta modulation and PWM modulation, avoided delta modulation to quantize the problem that exponent number equates that the overload brought and signal to noise ratio reduce, and overcome the non-linear of PWM modulation again.Just can recover original signal by an integrator, reach good linearty.

Description of drawings

Fig. 1 is EE﹠amp; R digital power amplifier principle schematic;

Fig. 2 is the delta modulation principle schematic;

Fig. 3 is a delta modulation overload schematic diagram;

Fig. 4 is a pwm signal waveform schematic diagram;

Fig. 5 is a demodulation structure schematic diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is described.

As shown in Figure 5, be the demodulation structure schematic diagram of practicality of the present invention, as can be seen from the figure, this device comprises a time delay module, a subtracter, a PWM modulator, an amplifier, an integrator, order link successively.Wherein this amplifier can be made up of two Switch amplifiers.

Present embodiment is asked difference to signal earlier in conjunction with delta modulation and PWM modulation, and the increment of output is modulated by PWM, is modulation signal, needs the signal demodulation is got final product by an integrator restoring signal.As shown in Figure 5.

Input signal x (t) is x (t-τ) through time delay module 501 time-delays, and signal x (t) and signal x (t-τ) ask poor through subtracter 502, obtain increment d (t).Then d (t) signal is modulated through PWM modulator 503, obtained one+1,0,-1 three level signal y (t), y (t) signal can pass through amplifier 504 processing and amplifying, obtains y ' (t), y ' (t) through integrator 505, just obtains demodulation, recovers to obtain (t) signal of x '.

It is pointed out that the PWM modulation here is different with the two level PWMs modulation of introducing previously, except pulse duration reflected signal amplitude, also have the polarity of positive and negative symbol reflection original signal, is+1,0 therefore ,-1 three level signal.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with the people of this technology in the disclosed technical scope of the present invention; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Claims

1, a kind of modulation-demo-demodulation method is applicable in envelope elimination and the recovery technology, it is characterized in that this method may further comprise the steps:

B, with increment signal d (t) through pulse width modulation, obtain a three level signal y (t);

C, described three level signal y (t) is amplified, obtain signal y ' (t);

2, modulation-demo-demodulation method as claimed in claim 1, it is characterized in that step a comprises further input signal x (t) is divided into the two-way same signal that wherein one road signal obtains signal x (t-τ) through delay process, signal x (t) and signal x (t-τ) subtract each other, and obtain increment signal d (t).

3, a kind of device of realizing the described modulation-demo-demodulation method of claim 1, it is characterized in that, this device comprises a time delay module, a subtracter, a PWM modulator, an amplifier, an integrator, described time delay module is done delay process to the road signal that input signal x (t) tells, described subtracter sends to described PWM modulator after input signal x (t) and time delayed signal x (t-τ) are subtracted each other, signal after the modulation amplifies through described amplifier, send to described integrator, obtain demodulation.

4, device as claimed in claim 3 is characterized in that, described amplifier is made up of two Switch amplifiers.