CN1449165A - Instantaneous phase continuous differencing four-phase-shift-keyed modulating technology - Google Patents

Abstract

The QPSK modulating and demodulating technique with Hilbert transformation phase continuous difference pi/4 (HCD pi/4 QPSK as below) is developed on the base of traditional pi/4 - DQPSK modulating technique. By Hilbert transformion, the QPSK modulating and demodulating technique with phase continuous difference pi/4 is constructed. The maximum phase difference of transitional region between the codes of adjacent signals approximates zero. And the jumping value of main phase is a continuous value. In the invention, the energy consumption will be reduced, the anti-disturbance capacity, the secrecy performance and the ability of data transmission will be improved in radio mobile communication.

Description

Instantaneous phase continuous differencing four-phase-shift-keyed modulating technology

The present invention relates to the radio mobile communication technical field.

PI/4-DQPSK (π/4-shift Differential Code Quadrature Phase ShiftKeying) position modulation mutually is to use more a kind of modulation system in recent years in mobile communication, is adopted by U.S. Digital Cellular System standard I S-54 and Japan digital cellular system PDC.In the position in digital communication field phase modulation and demodulation technology, position phase saltus step+π/4 ,-π/4 ,+3* π/4 ,-3* π/4, just in time represent dibit word information 00,01,11,10, PI/4-DQPSK position phase modulation technique as the standard modulation system, the absolute value that dominant bit between the adjacent code element of signal differs is π * 3/4, and the absolute value that minimum bit differs is π/4.But position phase saltus step contains numerous harmonic components, harmonic component meeting consumed energy, occupied frequency bandwidth, reduction anti-jamming capacity, a certain amount of power of consumption etc.In mobile radio system, high power system capacity and high communication quality are the targets that system is pursued.In order to realize such target, will have that modulation and demodulation mode, coded system, multi-access mode are realized more efficiently.

Purpose of the present invention is exactly to propose a kind of phase continuous difference π of Hilbert transform/4 QPSK modulation and demodulation technology (being called for short HCD π/4 QPSK) that have at this present situation, grows up on phase modulation technique basis, original PI/4-DQPSK position.By Hilbert transform, set up phase continuous difference π/4QPSK modulation and demodulation technology, the absolute value that differs at the transition region dominant bit between the adjacent code element of signal levels off to 0, a main position phase hop value is continuous changing value.In wireless mobile communications, can reduce energy consumption, improve antijamming capability, strengthen security performance, improve data transmission capabilities etc.

In the code division multiple access spread spectrum communication system of wideband territory, (be called again among the 21 century radio multi-user multimedia mobile communication CDMA of system), as HCD π/4 QPSK technology have been adopted, can effectively improve the total system data transmission capabilities, improve total system digital signal anti-jamming capacity in transmission course, reduce the frequency bandwidth that digital information is occupied, promptly utilize limited frequency resource efficiently, improved system-wide integration capability.

The present invention is achieved by the following technical solutions, wherein mainly contains 3 points; The one, Hilbert transform (Helbter Transform) technology, the 2nd, phase continuous difference π/4 QPSK modulation techniques, the 3rd, demodulation techniques.

Accompanying drawing has four width of cloth.Fig. 1 is HCD π/4 QPSK modulation transmitting terminal block diagram, and Fig. 2 is the receiving demodulation device block diagram of HCD π/4 QPSK, and Fig. 3 is the oscillogram of HCD π/4 QPSK demodulation staes, and Fig. 4 is the HCD π/spectrogram of 4 QPSK modulating stages in the diffCDMA system.

When with π/4 DQPSK position phase modulation system, phasic difference and signal expression can be write as the form of (1) and (2) formula: Δ θ k=θ k-θ k-1, θ k=Δ θ k+ θ k-1 (1)

f(t)＝A*cos(ωt+θk)＝A*cos(ωt+Δθk+θk-1)

In=cos ω tcos (Δ θ k+ θ k-1)-sin ω tsin (Δ θ k+ θ k-1) (2) formula, A is a coefficient, and θ k is the phase function of k code-element period, and θ k-1 is the phase function of k+1 code-element period, and Δ θ k is adjacent phasic difference.ω is the angular frequency of carrier signal.

Find out the Hilbert transform form of f (t) (t), shown in (3) formula: $\hat{f}=\frac{1}{2\mathrm{\πj}}\underset{0}{\overset{\∞}{\∫}}\{F\left(\mathrm{\ω}\right)e^{\mathrm{j\ωt}}-F(-\mathrm{\ω})e^{-\mathrm{j\ωt}}\}\mathrm{d\ω}---\left(3\right)$ $\underset{0}{\overset{\∞}{\∫}}F(-\mathrm{\ω})e^{-\mathrm{j\ωt}}\mathrm{d\ω}=\underset{\∞}{\overset{0}{\∫}}F\left(\mathrm{\ω}\right)e^{\mathrm{j\ωt}}\mathrm{d\ω}$ $\hat{f}=\frac{1}{2\mathrm{\πj}}\{\underset{0}{\overset{\∞}{\∫}}F\left(\mathrm{\ω}\right)e^{\mathrm{j\ωt}}\mathrm{d\ω}-\underset{-\∞}{\overset{0}{\∫}}F\left(\mathrm{\ω}\right)e^{\mathrm{j\ωt}}\}\mathrm{d\ω}$ $=\frac{1}{2\mathrm{\π}}\{\underset{0}{\overset{\∞}{\∫}}-\mathrm{jF}\left(\mathrm{\ω}\right)e^{\mathrm{j\ωt}}\mathrm{d\ω}+\underset{-\∞}{\overset{0}{\∫}}\mathrm{jF}\left(\mathrm{\ω}\right)e^{\mathrm{j\ωt}}\}\mathrm{d\ω}$ $=\frac{1}{2\mathrm{\π}}\underset{-\∞}{\overset{\∞}{\∫}}\{-\mathrm{jsgn\ω}\}F\left(\mathrm{\ω}\right)\mathrm{d\ω}---\left(4\right)$ In the formula,

F (ω)=R (ω)+jX (ω) (5), the described real function representation that is f (t) at frequency domain of (5) formula, real function can be write as the form of odd function and even function sum.Odd function, even function are shown in (6) and (7) formula. $R\left(\mathrm{\ω}\right)=\underset{-\∞}{\overset{+\∞}{\∫}}f\left(t\right)\·\cos \mathrm{\ωt}\·\mathrm{dt}---\left(6\right),----R\left(\mathrm{\ω}\right)$ Be even function. $X\left(\mathrm{\ω}\right)=\underset{-\∞}{\overset{\∞}{\∫}}f\left(t\right)\·\sin \mathrm{\ω}\·\mathrm{dt}---\left(7\right)----X\left(\mathrm{\ω}\right)$ Be odd function.

Secondly according to (1) and (2) formula, we redefine the coefficient A (t) of HCD π/4 QPSK shown in (8) formula, θ k (t) is that the phase function of k code-element period is shown in (9) formula, θ k-1 (t) is the phase function of k+1 code-element period, and the adjacent phasic difference of Δ θ k (t) is shown in (10) formula.Tb is symbol (symbol) cycle or cries the code-element period time, $A\left(t\right)=\sqrt{f^2\left(t\right)+{\hat{f}}^2\left(t\right)}---\left(8\right),$ $\mathrm{\θk}\left(t\right)={\tan }^{-1}\frac{\hat{f}\left(t\right)}{f\left(t\right)}---\left(9\right),$

Δθ _k(t)＝θ _k(t)-θ _k(t-T _b)，θ _k(t)＝Δθ _k(t)+θ _k(t-T _b)(10)

Through this Hilbert transform, the transmitting terminal in system is modulated the transmitting terminal block diagram according to following formula HCD π/4 QPSK that just can draw, and sees shown in Figure 1.In Fig. 1, HCD π/4 qpsk modulators comprise four functional module parts, and the one, Hilbert transform module (H conversion), the 2nd, phasic difference branch and symbolism module (comprising decay part), the 3rd, phase continuous module, the 4th, QPSK modulating stage module.

Introduce the demodulation techniques of HCD π/4 QPSK at last.Receiving terminal in system is described as (11) formula through the adjacent phasic difference Δ θ k (t) after the Hilbert transform demodulation, is the instantaneous phasic difference of composite signal. $\mathrm{\Δ\θk}\left(t\right)=\frac{\hat{f}\left(t\right)f(t-T_b)-f\left(t\right)\hat{f}(t-T_b)}{f\left(t\right)f(t-T_b)+\hat{f}\left(t\right)\hat{f}(t-T_b)}---\left(11\right)$

According to the basic principle of π/4 DQPSK position phase modulation systems, the signal of two quadrature positions of output phase is I respectively _kAnd Q _k, it is by I that the position of output is worth Δ θ k (t) mutually _kAnd Q _kSynthetic and form.According to I _kAnd Q _kValue just can obtain phasic difference signal delta θ k (t), again through a decision circuit, phasic difference signal delta θ k (t) is become corresponding binary code, this demodulation method is for postponing demodulation method.The receiving demodulation device block diagram of the HCD π that draws thus/4 QPSK as shown in Figure 2.In Fig. 2, HCD π/4 qpsk demodulators are divided into several sections according to function, comprise nine functional modules, and Hilbert transformer, delayer (finishing the time-delay of a symbol period Tb), multiplier and adder are arranged.

Technology involved in the present invention had been done simulated experiment on mainframe computer, major parameter is during experiment: each channel data transfer rate is 64Kbps, and shared 32 channels, the rate of data signalling of system are 2Mbps.First order modulation system is HCD π/4 QPSK modes, and first order carrier frequency is 32KHz.Pilot signal is included among each channel, and the code check of Walsh spread-spectrum codes is 4.096Mcps, and the carrier frequency of system's transmitting terminal is 2GHz.

Effect shows oscillogram and two aspects of spectrogram.The waveform of typical case adjacent phase continuous and discontinuousization as shown in Figure 3, dotted line is the waveform of the mutually discontinuous change in position in adjacent two cycles, as can be known from Figure, a phase step changing value is a pi/2.And solid line is described is line of transference after the serialization between two adjacent periods, realizes adjacent periods smoothing transition.Step signal contains many harmonic components from the spectroscopy angle, wants consumed energy and causes interference easily in the process that signal is propagated, and comparatively speaking, put into practice after the serialization mutually at two phase ortho positions, has promptly compressed frequency bandwidth, has reduced interference.

Spectrogram is seen shown in Figure 4, and what thick line was described is the power spectrum that adopts HCD π/4 QPSK modulating stages, and what fine rule was described is to adopt and non-phase continuous technology power spectrum at first modulating stage.Envelope among the figure except main peak, about respectively comprise 8 peaks; That is to say that main peak is the centre frequency of modulating stage, 8 peaks, from second to the 8th peak are respectively 8 order harmonic components.Useful Information is determined by main peak that mainly other harmonic components should be the smaller the better, flogs a dead horse because harmonic component can consume power consumption.In mobile radio communication system, the utilization ratio of power supply should be high more good more.Each harmonic component learns that except that main peak remained unchanged, second to the 8th peak had descended 3.87db respectively to 19.36db in two kinds of average power spectral lines of comparison.For the average power of nonsinusoidal signal, equal stationary component and each multifrequency sinusoid average power component sum.Learn that according to calculating when K=8, the ratio of the two average power is about 10: 6.5, promptly under the constant situation of available signal power, useless consumed power declines to a great extent.Be more in addition aspect the frequency bandwidth of system, serialization system output band width is narrower than discontinuousization band system band width.So, after HCD π/4 QPSK modulation systems uses, improved effectively diffCDMA overall performance, comprise and reduce frequency bandwidth, improved noise this, improved power utilization efficient etc.

Claims (2)

1. one kind has the phase continuous difference π of Hilbert transform/4 QPSK modulation and demodulation technology (being called for short HCD π/4 QPSK), adopting more efficiently on phase modulation technique basis, original PI/4-DQPSK position, the modulation and demodulation mode realizes, it is characterized in that by Hilbert transform, the coefficient A (t) that redefines HCD π/4QPSK is shown in (8) formula, θ k (t) is that the phase function of k code-element period is shown in (9) formula, θ k-1 (t) is the phase function of k+1 code-element period, the adjacent phasic difference of Δ θ k (t) shown in (10) formula, T _bBe symbol (symbol) cycle or cry the code-element period time, $A\left(t\right)=\sqrt{f^2\left(t\right)+{\hat{f}}^2\left(t\right)}---\left(8\right),$ $\mathrm{\θk}\left(t\right)={\tan }^{-1}\frac{\hat{f}\left(t\right)}{f\left(t\right)}---\left(9\right),$

Δθ _k(t)＝θ _k(t)-θ _k(t-T _b)，θ _k(t)＝Δθ _k(t)+θ _k(t-T _b) (10)

Through this Hilbert transform, transmitting terminal in system, set out HCD π/4 QPSK modulation transmitting terminal block diagram according to following formula, this HCD π/4 qpsk modulators comprise four functional module parts, the one, Hilbert transform module (H conversion), the 2nd, phasic difference branch and symbolism module (comprising decay part), the 3rd, phase continuous module, the 4th, QPSK modulating stage module.

2. by the described phase continuous difference π of the Hilbert transform/4 QPSK modulation and demodulation technology that have of claim 1, it is characterized in that receiving terminal in system, describing as (11) formula through the adjacent phasic difference Δ θ k (t) after the Hilbert transform demodulation, is the instantaneous phasic difference of composite signal $\mathrm{\Δ\θk}\left(t\right)=\frac{\hat{f}\left(t\right)f(t-\left(T_b\right)-f\left(t\right)\hat{f}(t-T_b))}{f\left(t\right)f(t-T_b)+\hat{f}\left(t\right)\hat{f}(t-T_b)}---\left(11\right)$ Again through a decision circuit, phasic difference signal delta θ k (t) is become corresponding binary code, the receiving demodulation device block diagram of the HCD π that sets out thus/4 QPSK, comprise nine functional modules, Hilbert transformer, delayer (finishing the time-delay of a symbol period Tb), multiplier and adder are arranged.

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