CN105100968A - Digital intercom system based on MPPSK (M-ary Phase Position Shift Keying) modulation - Google Patents

Abstract

The invention discloses a digital intercom system based on MPPSK (M-ary Phase Position Shift Keying) modulation. The digital intercom system is characterized in that the MPPSK modulation is used as a modulation and demodulation manner of a physical layer of a digital intercom. According to special spectrum characteristics of an MPPSK modulated signal, high-speed intercom information is in plug-in transmission by utilizing the spectrum gap or the idle spectrum between adjacent channels in the existing digital intercom system. Normal communication of a receiving end of the system can be ensured only by completing adjacent-frequency or same-frequency interference elimination of the existing digital intercom on a digital base band. An MPPSK system is adopted in a transmitter and used as the modulation manner of the physical layer of the digital intercom; extra spectrum resources are not occupied; the high-speed intercom information is in plug-in transmission only by utilizing the spectrum gap or the idle spectrum between the adjacent channels in the existing digital intercom system; a receiver is only necessary to eliminate adjacent-frequency or same-frequency interference of other digital intercoms on the digital base band; and thus, normal demodulation of the MPPSK modulated signal can be ensured.

Description

Based on the digital handset system of MPPSK modulation

Technical field

The present invention relates to a kind of digital communication system in digital mobile communication field, particularly relate to a kind of digital handset system based on MPPSK modulation.

Background technology

1. digital handset current situation

Interphone communication belongs to professional radio communication, originate from army the earliest, after due to its unique advantage in colony dispatching, emergency communication, instant messaging etc., be widely used in the fields such as public security, fire-fighting, rescue, petrochemical industry and civilian construction, estate management, hotel eatery, market, school, in national economy and daily life, there is important function.

Intercom in the past all belongs to analog-interphone, but along with the increase of number of users, frequency spectrum resource growing tension, user's request is simultaneously constantly variation also, impels last analog machine in China's mobile communication system---and the digitlization of intercom is imperative.Relative to analog-interphone, digital handset has the four large advantages that frequency efficiency is high, speech quality good, can provide the supplementary services such as market demand function, be easy to encryption.

Simultaneously along with microprocessor, the develop rapidly of monolithic codec, the group system in cellular Public mobile communication and professional mobile communication has developed into time division multiple access (TDMA) digital system of the second generation from the frequency division multiple access of the first generation (FDMA) analogue system.Public's intercom, professional frequency modulation machine and non-stop layer clustered system in professional mobile communication but never realize digitlization.ETSITS102 digital handset standard was just formulated in 2005 in Europe:

(1) dPMR is equivalent to digital public's intercom standard, and adopt FDMA, channel spacing 6.25kHz, effective isotropic radiated power is lower than 500mW;

(2) DMR is equivalent to digital professional frequency modulation machine standard, defines air interface, voice and general business function, data protocol and conformance test method;

(3) DSRR is equivalent to digital non-center clustered system standard, defines system performance, signaling protocol, radio station characteristic, radio-frequency technique index and method of measurement.

In enterprise product research and development: Kenwood and ICOM company develop analog/digital bimodulus, frequency division multiple access, channel spacing 6.25kHz and 12.5kHz adaptive radio.CML company of Britain develops CMX7141 baseband chip and CMX618 low bit-rate RALCWI audio coder & decoder (codec), in order to design dPMR digital handset.Motorola Inc. is proposed DMR radio station.

In recent years, domestic digital handset industrial circle had carried out multinomial digital mobile communication technical research, actively promoted digital handset product development and standard stipulation work.Within 2007, the Ministry of Information Industry issues letter without letter [2007] No. 81 literary compositions " notice about issuing " digital handset system equipment wireless radio-frequency index request " (trying) ", indicates that the R&D work of China's digital handset formally starts.20080985-T-339 " digital intercom equipment and technology requires and the method for testing " national standard that comprehensive [2008] No. 154 literary compositions of GB Committee in 2008 have been assigned to be responsible for by the Ministry of Industry and Information Technology lays a course project.In national standard working group meeting on October 27 in 2012, FDMA standard aspect has the fast light in Beijing to reach two parts of motions of communication common carrier and Fujian Lian Tuo scientific & technical corporation; PDR, Lian Tuo company of TDMA standard aspect You Hainengda company ARC, the vertical logical 4 parts of motions such as company's T HA, Motorola Inc. DMR in lattice sky, sea, Guangzhou, show that instant stage has been arrived in the research and development of digital handset.But make a general survey of current domestic and international existing digital handset system, as TETRA, DMR, dPMR NXDN NDR standard in Europe, the P25 standard of the U.S., and the PDT standard etc. that state inland sea can reach, they are not only incompatible, and all do not become the standard of relevant department of China accreditation.

Present domestic urgent need develops brand-new digital handset system, significantly more than above-mentioned all schemes in key technical index, for determining national standard, the competition international standard of digital handset in the future, lays the foundation.

2.MPPSK modulation system

1) " plug hole " transmits thought

The spectrum management pattern generally adopted at present can be traced to for 20 beginnings of the century, thought that frequency spectrum was limited natural resources at that time, in order to avoid mutual interference, a lot of little frequency allocation must be divided into by action by government to monopolize to the user of different demand. the unit availability of frequency spectrum theoretical limit of the channel capacity that Shannon, Nyquist derive according to ideal rectangle bandwidth and 2Baud/Hz, namely divide with this rectangular spectrum and adapt, same existing digital handset system is also continued to use this rectangle and is monopolized formula spectrum division mode.But nowadays shortage of resources, the frequency spectrum resource that can utilize for digital handset is also very limited, and thus improve the availability of frequency spectrum and the capacity usage ratio of information transmission system itself, side is fundamental policy.

Narrow " blank " frequency spectrum resource of existing digital handset channel compole is actually waste, if can utilize these " free time " frequency spectrums better, will be an important breakthrough to digital handset industry.The exclusive non-rectangle spectrum division pattern adding wider " frequency spectrum grass " and share of ultra-narrow " frequency spectrum tree ", providing possibility for carrying out " plug hole " information transmission in this " free time " frequency spectrum, providing theory and technology thinking for solving spectrum requirement.

2) MPPSK modulation system

In order to improve data transmission bauds, modern communications to be had to towards broadband even ultra broadband (UltraWideBand, UWB) technique direction development, and the frequency resource taken is increasing, but the bandwidth efficiency of information transmission is still not high.Therefore, compress wireless transmission frequency spectrum to greatest extent, improve spectrum utilization efficiency, there is important practical significance and direct economic benefit, also more and more become the focus of current research.Wherein multielement positional phase shift keying (M-aryPositionPhaseShiftKeying, MPPSK) modulation is as a kind of high spectrum utilization modulation technique, receives much concern in recent years, is very applicable to digital handset communication.

The waveform expression formula of MPPSK modulation (see " multielement positional phase shift keying modulation and demodulation method ", patent of invention number: ZL200710025202.1) is as follows:

$s_k\left(t\right)=\left\{\begin{array}{ccc}{\mathrm{sin\&omega;}}_{c}t,& 0\&le;t<{\mathrm{NT}}_c,& k=0\\ \left\{\begin{array}{c}{\mathrm{sin\&omega;}}_{c}t,\\ -{\mathrm{sin\&omega;}}_{c}t,\\ {\mathrm{sin\&omega;}}_{c}t,\end{array}\right.& \begin{array}{c}0\&le;t\&le;\left(k-1\right){\mathrm{KT}}_c,\\ \left(k-1\right){\mathrm{KT}}_c<t<(k-r_g){\mathrm{KT}}_c,\\ \left(k-r_g\right){\mathrm{KT}}_c\&le;t<{\mathrm{NT}}_c,\end{array}& 1\&le;k\&le;M-1\end{array}\right.---\left(1\right)$

Wherein, ω _cfor the angular frequency of modulated carrier, T _c=2 π/ω _cfor carrier cycle, 0≤r _g< 1 is the symbol protection Separation control factor, by r _gconstitute " modulation parameter " that change signal bandwidth, efficiency of transmission and demodulation performance with integer M, N, K.

As code-element period T=NT _c=2 π N/ ω _ctime, the chip rate R of MPPSK modulation _bwith bit rate R _b(hereinafter referred to as " code check ") is respectively

R _B＝f _c/N(2a)

R _b＝(f _c/N)log ₂M(2b)

And analysis shows, works as r _gif met when=0

N＝(M-1)*K(3)

Discrete line spectrum then in MPPSK power spectrum density (PSD) can be eliminated completely, for the interference of other digital handset signal of adjacent channel, and can be lower.

3) shock filter

For improving the availability of frequency spectrum, " 0 " code element of MPPSK modulation signal is very little with " non-zero " code element difference in time domain, and in demodulator, being this difference outstanding, we had once invented a kind of so-called " shock filter ", in order to the phase hit information of outstanding MPPSK modulation signal.This shock filter adopts the narrow-band digital band pass filter of the special infinite impulse response of a class (IIR) to realize the earliest, the a pair conjugation zero point very close by resonance frequency and at least two pairs of conjugate poles are formed, trap-selecting frequency characteristic extremely narrow shown in a Figure 15 (a) is presented in its passband, thus change MPPSK modulation signal into obvious and strong parasitic amplitude modulation impact at the modulates information at " non-zero " code element place, output signal-to-noise ratio is significantly improved, therefore be referred to as digital shock filter, but at code element " 0 " place then without corresponding wave forms impact, (see " for strengthening the impact filtering method of asymmetric binary modulating signal " as Suo Shi Figure 15 (b), patent of invention number: ZL200910029875.3." impact filtering " involved in the present invention, source is all this, no longer states below).Now utilize simple amplitude to adjudicate and can carry out reliable demodulation.

Although above-mentioned IIR type numeral shock filter has excellent demodulation performance, but due to its unique and structure condition of harshness, also there is many defects (refer to " the two carrier wave ABSK communication systems based on same narrow band filter ", patent of invention publication number: CN102932298A ").For seeking narrower equivalent rectangular bandwidth and the receiver sensitivity of Geng Gao, be formed more perfectly " coupling " with MPPSK signal spectrum simultaneously, on the basis of IIR type numeral shock filter, we have invented again a kind of " two zero point shock filter " (refer to " based on the MPPSK coherent demodulation method of shock filter at two zero point; application for a patent for invention number: 201310088183.2, publication number: CN103209152A).This pair zero point shock filter essence be still the special IIR narrow-band digital band pass filter of a class, just change into by forming at two pairs of very close conjugation zero points of resonance frequency and at least two pairs of conjugate poles, and the centre frequency place therefore in passband presents 2 extremely narrow trap-selecting frequency characteristics, as shown in Figure 16 (a), MPPSK Received signal strength can be made at modulates information place equally to produce obvious and strong parasitic amplitude modulation impact, as shown in Figure 16 (b).

In a word, classical filtering theory has been expanded in the introducing of shock filter, the significant increase demodulation performance of MPPSK communication system; And it can take numeral or analog filter, IIR or FIR filter, simple zero or the diversity at two zero point in implementation, add again its flexibility and versatility.

4) based on the MPPSK coherent demodulator of impact filtering

For improving the demodulation performance of MPPSK communication system further, expand matched filtering theory, in above-mentioned " the MPPSK coherent demodulation method based on shock filter at two zero point ", MPPSK Received signal strength is divided into two-way: a road goes out local coherent carrier through arrowband bandpass filtering with the feature extraction making full use of MPPSK Received signal strength and be rich in carrier information, MPPSK Received signal strength is converted into significant parasitic amplitude modulation at the phase-modulation at " non-zero " code element place and impacts by the shock filter at two zero point that another road then adopts equivalent rectangular bandwidth extremely narrow; Then after being multiplied to two-way output signal, low-pass filtering is to extract envelope signal; Last under the guidance of sampling pulse, simple threshold judgement can be adopted to carry out demodulation.Owing to again taking full advantage of carrier energy, thus compared with the MPPSK non-coherent demodulation scheme of adjudicating based on direct amplitude, the method significantly can promote the demodulation performance of MPPSK signal.

5) " filtering of code check territory " of MPPSK system

We are once in " a kind of hybrid multiplex modulation system of compatible medium wave analog AM broadcast " (application for a patent for invention number: 201310464224.3), impact filtering is being carried out to AM-MPPSK complex modulated Received signal strength and is being multiplied by after coherent carrier forwards base band frequency range to, the perfection directly utilizing simulated audio signal and the MPPSK digital signal difference in spectrum distribution can carry out the two is separated, its key is then the reasonable setting of both rates of information throughput, the low-limit frequency (being generally taken as the code check of this MPPSK signal) mainly contained with frequency spectrum of General Requirements MPPSK signal must higher than the highest frequency of frequency range residing for audio signal, now adopt the band pass filter of corresponding passband and stopband separation and Extraction can go out desired signal respectively.

We are by above-mentioned way called after " filtering of code check territory " in " a kind of common channel full duplex system based on MPPSK modulation " (patent of invention number: CN103957182A) simultaneously, its essence is the further filtering interference signals of spectrum distribution difference utilizing Received signal strength and interference signal.The code check corresponding with it due to the spectrum distribution of signal or information rate directly related, so be referred to as " code check territory " (in essence still for frequency domain) filtering.Theory analysis is thought, to be multiplied with coherent carrier and after bandpass filtering carrying out impact filtering to MPPSK signal, the frequency spectrum its power spectrum main lobe is positioned between 1 times of fundamental frequency to 8 ~ 10 times of fundamental frequencies just can represent its main useful information and carry out follow-up correlation demodulation, and fundamental frequency is here the code check of MPPSK bar modulation signal.

Owing to no matter being DMR digital handset or dPMR digital handset, its rate of information throughput is fixing, but MPPSK signal can pass through modulation parameter M and N controls transfer speed, make the rate of information throughput between native system and existing digital handset can there is larger difference, and this just naturally agrees with above-mentioned " filtering of code check territory " thought, thus likely expansive approach in digital handset system.

Summary of the invention

The object of the invention is to the above problem overcoming prior art existence, a kind of digital handset system based on MPPSK modulation is provided, this system utilizes " joint portion " or the spectral slots of conventional digital talkback system spectrum division, the high speed intercommunication information that " plug hole " transmission of one line is new, ensureing more still there is good communication performance while spectral efficient, also do not affect the transmission of existing digital handset, be therefore a kind of can with existing digital handset and the new digital intercom system of depositing.

For realizing above-mentioned technical purpose, reach above-mentioned technique effect, the present invention is achieved through the following technical solutions:

Based on a digital handset system for MPPSK modulation, described MPPSK is modulated at code-element period [0 a, T=NT _c] expression formula as follows:

$s_k\left(t\right)=\left\{\begin{array}{ccc}{\mathrm{sin\&omega;}}_{c}t,& 0\&le;t<{\mathrm{NT}}_c,& k=0\\ \left\{\begin{array}{c}{\mathrm{sin\&omega;}}_{c}t,\\ -{\mathrm{sin\&omega;}}_{c}t,\\ {\mathrm{sin\&omega;}}_{c}t,\end{array}\right.& \begin{array}{c}0\&le;t\&le;\left(k-1\right)\left(K+r_g\right)T_c,\\ \left(k-1\right)\left(K+r_g\right)T_c<t<\&lsqb;\left(k-1\right)\left(K+r_g\right)+K\&rsqb;T_c,\\ \left(k-r_g\right){\mathrm{KT}}_c\&le;t<{\mathrm{NT}}_c,\end{array}& 1\&le;k\&le;M-1\end{array}\right.---\left(1\right)$

Wherein, ω _c=2 π f _cfor the angular frequency of modulated carrier, T _c=2 π/ω _cfor carrier cycle, 0≤r _g< 1 is the symbol protection Separation control factor, and M, N, K are integer, with the physical layer modulation demodulation mode of MPPSK modulation as digital handset, and chip rate R _b=f _c/ N is at least higher than 12.5kHz.

Further, according to the particular frequency spectrum characteristic of MPPSK modulation signal, native system utilizes the spectral slots in existing digital handset system, or the idle frequency spectrum between adjacent channel, plug hole transmission of one line high speed intercommunication information.

Further, for existing digital handset receiving terminal, only (this is all existing basic function for any digital handset product) need be disturbed by the MPPSK on radio frequency outside filtering channel size; And for native system receiving terminal, adjacent frequency or the co-channel interference elimination of existing digital handset only need be completed at digital baseband, can proper communication be ensured.

Further, digital modulation signals described in native system adopts multielement positional phase shift keying, and the expression formula of described multielement positional phase shift keying is such as formula shown in (1):

1) N=(M-1) * K, force down its power spectrum sidebands levels with the line spectrum eliminated in described MPPSK modulation signal power spectrum, ensure that native system to carry out in digital handset channel space while " plug hole " transmits little to the interference of other digital handsets of neighboring trace;

2) described multielement positional phase shift keying modulation signal transmission code rate is at least higher than existing digital handset channel spacing.

Further, the method for the receiver adjacent frequency or co-channel interference of eliminating other digital handsets at digital baseband comprises following steps:

1) first carrying out impact filtering to the aliasing signal of received MPPSK modulation signal and interference, is that stronger parasitic amplitude modulation is impacted by the phase place change transitions of " non-zero code element " in described MPPSK modulation signal;

2) be multiplied by the suppression of coherent carrier, bandpass filtering, correlation demodulation and suitable bandreject filtering method to adjacent frequency or with other digital handset interference signals frequently to impacting filtered output signals combination, and reliably demodulate MPPSK signal.

Preferably, for the co-channel interference (f of other digital handsets _c=F _c), neighbour's frequently interference (| F-f _c| < R _b), adjacent frequency interference very far away (| F-f _c| > 10*R _b), adopt described reception processing procedure to carry out interference and eliminate, wherein the left cut-off frequency of band pass filter should be greater than zero-frequency, and band connection frequency is set to R _b~ (8 ~ 10) * R _b, left and right stopband attenuation should be tried one's best greatly simultaneously, to utilize the spectrum distribution difference filtering interference signals receiving MPPSK signal and existing digital handset signal, wherein F _cfor the carrier frequency of other digital handsets, F is the interference spectrum of other digital handsets.

Preferably, for the adjacent frequency interference (R far away of other digital handsets _b≤ | F-f _c|≤10*R _b), adopt suitable bandreject filtering to eliminate, wherein the bandwidth of rejection of band stop filter should slightly larger than adjacent frequency jamming signal bandwidth far away, and stopband attenuation is at least greater than-40dB.

Preferably, described receiving terminal is after eliminating adjacent frequency or the digital handset interference signal with frequency, utilize the whole surge waveform sample sequence of broadening after bandpass filtering prestored as related operation template or matched filtering impulse response, slip fixed step size is to code element 0 successively, 1, or code element 1 2...M-1,2,3...M impact there is position after, be multiplied with the MPPSK Received signal strength of the current symbol after bandpass filtering respectively and carry out integration judgement, integrated value the maximum being demodulated into corresponding transmission code element.

The invention has the beneficial effects as follows:

1) spectrum efficiency is high, and demodulation performance is good

Existing research and open test show that MPPSK modulation signal itself just has the high spectrum utilization of super existing general communication system far away.With digital intercom machine technology be combined with the development and popularization that are beneficial to and promote China's digital intercom machine technology; The method of reseptance of distinctive " filtering of code check territory " of native system simultaneously and suitable bandreject filtering, adds channel coding technology simultaneously, in turn ensure that the reliable demodulation to useful MPPSK signal.

2) compatible good

Current domestic and international existing digital handset system, as TETRA, DMR, dPMR/NXDN/NDR standard in Europe, the P25 standard of the U.S., and the PDT standard etc. of inland sea Neng Da company of state, all incompatible between them, be unfavorable for development and the popularization of digital intercom machine technology, but according to the distinctive plug hole transmission characteristic of system of the present invention, can deposit with existing various digital handset system and not interfere with each other.

3) little to the signal disturbing of adjacent channel

Because MPPSK modulation signal is made up of " frequency spectrum tree " and " frequency spectrum grass ", wherein " frequency spectrum tree " very bandwidth is narrow, is exactly almost the sinusoidal signal frequency spectrum of carrier wave; And its frequency spectrum grass is lower than the power spectral density of legacy ultra-wideband signal, be submerged in completely under background noise, very easily with existing wireless communications coexistence of systems and electromagnetic compatibility.According to above-mentioned characteristic, for the most easily by the adjacent digital handset channel in left and right of native system interference, only need when radio frequency reception, increase a band pass filter close with channel size, get final product the interference of basic filtering native system.

4) to adjacent frequency or high with interference and insulation degree frequently

Although native system is easily subject to adjacent frequency or the interference with frequently other digital handsets, native system distinctive " filtering of code check territory " and suitable bandreject filtering receiving handling method, can significantly other digital handset interference signals of filtering.

Above-mentioned explanation is only the general introduction of technical solution of the present invention, in order to better understand technological means of the present invention, and can be implemented according to the content of specification, coordinates accompanying drawing to be described in detail as follows below with preferred embodiment of the present invention.The specific embodiment of the present invention is provided in detail by following examples and accompanying drawing thereof.

Accompanying drawing explanation

Accompanying drawing described herein is used to provide a further understanding of the present invention, and form a application's part, schematic description and description of the present invention, for explaining the present invention, does not form inappropriate limitation of the present invention.In the accompanying drawings:

Fig. 1 (a) is the transmitter principle block diagram of the digital handset system based on MPPSK modulation;

Fig. 1 (b) is the receiver principle block diagram of the digital handset system based on MPPSK modulation;

Fig. 1 (c) is the power spectrum of MPPSK signal in Fig. 1 (a) system;

Fig. 2 is the special symbol of 4FSK modulation and the corresponding relation figure of frequency deviation in DMR digital handset;

Fig. 3 (a) is the full digital starting of MPPSK/EBPSK modulator;

Fig. 3 (b) is that the analog circuit of MPPSK/EBPSK modulator realizes;

Fig. 3 (c) is that the integrated circuit of MPPSK/EBPSK modulator realizes;

Fig. 4 is normalized power spectrum and the ber curve of 4FSK modulation signal in DMR digital handset, disturbs as additive white Gaussian noise (AWGN), without any chnnel coding;

Fig. 5 (a) is the Costas principle of phase lock loop block diagram that this area is commonly used;

Fig. 5 (b) be extract pure and with the carrier signal (curve of constant amplitude, abscissa be sampling number) of phase-locked loop input signal with frequently homophase.

Fig. 6 (a) is native system co-channel interference scene 1 time, receives the power spectrum of MPPSK signal at the MPPSK aliasing signal at digital baseband place;

Fig. 6 (b) is the partial enlarged drawing of Fig. 6 (a) near zero-frequency.

Fig. 7 (a) is that native system disturbs in neighbour's interference frequently and neighbour very far away and deposits scene 2 times, receives the power spectrum of MPPSK signal at the MPPSK aliasing signal at digital baseband place;

Fig. 7 (b) is the partial enlarged drawing of Fig. 7 (a) near zero-frequency.

Fig. 8 (a) is that native system exists scene 3 times in adjacent frequency interference far away, receives the power spectrum of MPPSK signal after digital baseband place utilizes bandpass filtering to carry out " filtering of code check territory " process;

Fig. 8 (b) is the partial enlarged drawing of Fig. 8 (a) near zero-frequency.

Fig. 9 is that native system exists scene 3 times in adjacent frequency interference far away, utilizes bandreject filtering with the power spectrum chart after filtering adjacent frequency interference far away;

Figure 10 (a) is the ber curve of MPPSK signal in carrier interference ratio C/I=-32.1dB situation;

Figure 10 (b) is in carrier interference ratio C/I=-81.8dB situation, wherein the ber curve of MPPSK carrier power C=0.5W, MPPSK signal;

Figure 11 (a) is that native system disturbs in neighbour's interference frequently and neighbour very far away and deposits scene 2, in carrier interference ratio C/I=-48.2dB situation, and the ber curve of MPPSK signal;

Figure 11 (b) is that native system disturbs in neighbour's interference frequently and neighbour very far away and deposits scene 2, in carrier interference ratio C/I=-97.9dB situation, and the wherein ber curve of MPPSK carrier power C=0.5W, MPPSK signal;

Figure 12 (a) is that native system exists scene 3 times in adjacent frequency interference far away, in carrier interference ratio C/I=-48.2dB situation, and the ber curve of MPPSK signal;

Figure 12 (b) is that native system exists scene 3 times in adjacent frequency interference far away, in carrier interference ratio C/I=-89.8dB situation, and the wherein ber curve of MPPSK carrier power C=0.5W, MPPSK signal;

Figure 13 (a) is the ber curve of Figure 12 (a) by the MPPSK after convolutional encoding;

Figure 13 (b) is the ber curve of Figure 12 (b) by the MPPSK after convolutional encoding;

Figure 14 is the 4FSK ber curve of carrier interference ratio C/I=-32.1dB, wherein MPPSK carrier power C=0.5W.

Figure 15 (a) is the amplitude-frequency response of IIR type numeral shock filter;

Figure 15 (b) is the output waveform of MPPSK signal by shock filter in Figure 15 (a).

Figure 16 (a) is the amplitude-frequency response of two remainder word shock filter;

Figure 16 (b) is the output waveform of MPPSK signal by shock filter in Figure 16 (a).

Embodiment

Below with reference to the accompanying drawings and in conjunction with the embodiments, describe the present invention in detail.

Based on the digital handset transmitter system of MPPSK modulation

For substituting the efficient modulation mode of the modulation system (the 4FSK modulation system as DMR digital handset) in existing digital handset system, i.e. MPPSK modulation, be the key factor of the digital handset based on MPPSK modulation, we wish that it possesses following 3 conditions simultaneously:

1. sidebands levels is low.

Requiring the PSD sidebands levels of the digital handset modulated based on MPPSK at least lower than carrier wave 60dB in the adjacent intercom channel bandwidth in left and right, is to reduce MPPSK signal to adjacent frequency or the interference with other digital handset of frequency.

2. character rate is high.

This has two aspect purposes: be first that any digital transmission system all wishes to provide numeric code rate high as far as possible to user, particularly at digital handset channel, if the lowest bit rate being not less than existing digital handset standard and can reaching can not be carried, be just difficult to realize digital intercom communication; Next is the needs in order to distinguish MPPSK impact signal envelope and adjacent frequency or same digital handset signal frequently from frequency spectrum as far as possible, and this explains further by the realization of " the digital handset receiver system based on MPPSK modulation ".

3. demodulation performance is good.

This is any digital transmission system for the main technique requirements of receiver (at this i.e. digital handset receiving terminal), has both depended on the technical merit of receiver, be more limited to the signal system of modulation waveform.

In above-mentioned 3 conditions:

" condition 1. " is necessary condition, determines " legitimacy " of the digital handset based on MPPSK modulation, namely can not damage the interests of existing digital handset user.From formula (1): by selecting lower modulation duty cycle and K:N, the PSD sidebands levels of MPPSK modulated signal all can be forced down arbitrarily, can meet " condition is 1. ", but MPPSK modulation is expected the discrete line spectrum thoroughly eliminated in PSD sideband and obtains lower sideband, more desirable;

" condition 2. " determines " advance " of the digital handset based on MPPSK modulation, be embodied in " high efficiency " and " durability " of the availability of frequency spectrum, should pursue as possible, and from formula (2), as M>2, adopt MPPSK modulation can obtain higher transmission rate, be worth preferential and adopt;

Whether whether the capacity usage ratio of digital handset that " condition 3. " embodies based on MPPSK modulation also can keep " high efficiency ", determine this technical system and have " practicality ", and the technical sophistication degree of digital handset in the future.Although MPPSK is multi-system modulation, namely each signal element can carry log ₂m-bit, but the demodulation performance of each bit is (namely according to bit signal to noise ratio E _b/ N ₀examination) and no less than M=2 time.

Therefore, after choosing comprehensively, digital handset system of the present invention, adopts MPPSK modulation system, the transmitter principle block diagram of the digital handset system based on MPPSK modulation namely as shown in Fig. 1 (a).

Fig. 1 (c) be systems radiate based on MPPSK modulation signal power spectrum chart.From Fig. 1 (c), even if described MPPSK digital handset transmitting terminal does not carry out any filtering or spectrum shaping, the sidebands levels of MPPSK modulation signal power spectrum also can lower than carrier wave 60dB.

2. based on the digital handset receiver of MPPSK modulation

According to background technology, the theory diagram of the digital handset receiver based on MPPSK modulation proposed by the invention is as shown in Fig. 1 (b), and its key link is as follows:

1) the MPPSK modulation signal received enters shock filter, is be divided into two-way after amplitude is impacted: a road directly outputs to multiplier by the phase place change transitions produced because of MPPSK modulation; Another road outputs to another input of multiplier after being used for extracting carrier wave that is pure as far as possible and same homophase frequently with it from the response of MPPSK modulation signal impact filtering.In multiplier, two paths of signals is multiplied, realizes the coherent demodulation of MPPSK being modulated to impact filtering signal envelope.

2) output of multiplier is MPPSK impact filtering signal envelope and other adjacent frequency or the mixing (superposition) with frequency digital handset signal, and the two is complete aliasing in time waveform, also may aliasing on frequency spectrum.Native system, because be that " plug hole " transmits in digital handset channel and channel gap, can be subject to adjacent frequency interference or the co-channel interference of existing digital handset.

Co-channel interference refers to that the carrier frequency of intercom signal is identical with the carrier frequency that native system MPPSK modulates, and adjacent frequency interference refers to that the carrier frequency of intercom signal is different with the carrier frequency that native system MPPSK modulates.Adjacent frequency interference be divided into neighbour's frequently interference (| F-f _c| < R _b), adjacent frequency interference (R far away _b≤ | F-f _c|≤10*R _b) and adjacent frequency interference very far away (| F-f _c| > 10*R _b), wherein R _bfor the chip rate of described MPPSK Received signal strength, F is the interference spectrum of other digital handsets, f _cfor the carrier frequency of MPPSK signal.Co-channel interference, neighbour frequently interference and adjacent frequency interference very far away, concerning native system, are all belong to same class interference, native system and the difference of above-mentioned interference signal in spectrum distribution can be utilized to carry out " code check territory " filtering.Adjacent frequency interference far away drops in the useful band limits of MPPSK signal, and at this moment " code check territory " filtering is invalid, and the present invention adopts the band stop filter of well-designed correspondence to carry out filtering.The transmission code rate that the present invention requires MPPSK to modulate in the design of " the digital handset transmitter system based on MPPSK modulation " is high, be exactly at least be higher than existing digital handset channel spacing at this, to guarantee from the left and right that MPPSK carrier wave is nearest other digital handset signal channels adjacent and to be all drop in neighbour's frequency interference range of native system with other digital handset signals frequently, only need utilize the filtering that the difference in spectrum distribution is carried out on " code check territory ", reduce implementation complexity.

Should be noted that at this, after native system passes through " filtering of the code check territory " process of " impact filtering → be multiplied by coherent carrier → bandpass filtering " to MPPSK Received signal strength, only leave the frequency spectrum be positioned between 1 times of fundamental frequency to 8 ~ 10 times of fundamental frequencies on its main lobe and just can represent its main useful information, at this moment need through disturbing judging treatmenting module to adjacent frequency far away, utilize existing techniques well known, judge whether to there is adjacent frequency far away interference, if existed, determine its interference spectrum scope.Then adopt corresponding band stop filter to carry out filtering, content of the present invention is not belonged to for judging treatmenting module, neither key of the present invention, just suppose knownly whether there is adjacent frequency far away interference and interfering frequency scope thereof at this.

3) modulate impact filtering signal feeding MPPSK demodulator to adjacent frequency or with the MPPSK after frequency digital handset interference signal Processing for removing, demodulate original data code flow.

4) a kind of digital handset system based on MPPSK modulation described in native system and other digital handsets existing are Coexistences, are ensureing the proper communication also needing to guarantee other digital handset systems existing while other digital handset systems existing do not impact native system.Lower than the PSD of legacy ultra-wideband signal according to native system distinctive " frequency spectrum grass ", be submerged in the characteristic under background noise completely, at other digital handset radio frequency reception ends existing, existing band pass filter, while other interference signals of filtering, is also enough to the interference of filtering native system to it.

In sum, the digital handset system based on MPPSK modulation of the present invention is by following Technical Design:

1.MPPSK modulator

1) selection of MPPSK modulation parameter

According in this specification background technology about described in the content of " MPPSK transmission system ", select MPPSK modulation parameter time should meet formula (3) as far as possible, namely get r _g=0 and N=(M-1) * K, the discrete line spectrum in MPPSK modulated signal power spectrum can be eliminated so completely, for the interference of other digital handset signal of left and right adjacent channel, can be lower.This condition is substituted into formula (2a), and the chip rate obtaining MPPSK modulation is

R _B＝f _c/N＝f _c/((M-1)*K)(5)

Visible, now code check is relevant with M, K and carrier frequency.In conjunction with emulation experiment, the numerical value of modulation parameter M and K and the highest code check can be determined under given carrier frequency according to the principle of formula (5).Here the chip rate R ensureing MPPSK modulation transmissions is also required _bnumerically at least higher than the channel spacing of existing digital handset.

Because the standard of present digital handset is a lot, therefore for simple and can describe the problem, the present embodiment gets the emulation that DMR digital handset standard is carried out adjacent frequency and co-channel interference signal.

The digital handset of DMR standard adopts 4FSK modulation-demodulation technique, R _b=4800B _d(baud), maximum frequency deviation D=1.944kHz, the frequency spectrum of its each symbology as shown in Figure 2.

Be approximately according to the bandwidth that the frequency interval between first zero point of 4FSK modulation signal calculates:

B _4FSK≈|f ₃-f _-3|+2f _s(6)

Wherein f ₃and f _-3be expressed as the carrier frequency that code element is ' 3 ' and '-3 ', its value is respectively f ₃=F _c+ 1.944kHz and f _-3=F _c-1.944kHz, f _s=4.8kHz is chip rate.Calculate theoretic bandwidth according to the frequency interval between first zero point, because the channel spacing of DMR digital handset is 12.5kHz, the bandwidth obtaining 4FSK modulation signal becomes B _4FSKthe base band highest frequency of=12.5kHz, 4FSK signal is F _max=6.25kHz.

In order to ensure that transmission code rate that MPPSK modulates is at least higher than the requirement at 4FSK signal channel interval.It is f that the present embodiment gets MPPSK modulation parameter _c=4.8MHz and K=8, N=128 and M=17 emulate, and now by formula (5), obtain R _b=f _c/ N=37.5kB _d, meet the demands, code check is then more than R _b=R _blog ₂17 > 150kbps, can pass video data.

2) realization of MPPSK modulator

Block diagram is implemented in the total digitalization that Fig. 3 (a) provides MPPSK modulator: the MPPSK sequence of symhols with M kind value controls MUX, from M group waveform sample, select the MPPSK modulation waveform numeral sample corresponding with current symbol, sending digital to analog converter (DAC) to be directly changed into carrier frequency is f _csimulation MPPSK modulated signal export; Fig. 3 (b) is then the simulated implementation mode of MPPSK modulator, the MPPSK modulation signal of simulation only directly need can be exported with information sequence and MPPSK bite rate control electronic switch, obviously simpler, cheap than the full digital starting mode of Fig. 3 (a), and can be used in higher operating frequency; Fig. 3 (c) is then the improvement to Fig. 3 (b), compensates the time delay of inverting amplifier by adding in-phase amplifier, be conducive to being operated in higher carrier frequency and integrated circuit (IC) chip integrated.

3) DMR digital handset transmitting terminal

DMR digital handset adopts 4FSK modulation, R _b=4800B _d, wherein each symbol carries 2bit information, then code check is R _b=9.6kbps, maximum frequency deviation D are 1.944kHz.In the present embodiment, DMR digital handset adopts digital quadrature synthesis modulation, simulation result as shown in Figure 4, wherein the spectrum width of 4FSK signal under-40dB sidebands levels is 8kHz<12.5kHz, meets the requirement of DMR digital handset 12.5kHz channel bandwidth.

2.MPPSK demodulator

The digital handset system based on MPPSK modulation that the present invention proposes, in " plug hole " transmitting procedure, can disturb with adjacent frequency or with DMR digital handset system frequently mutually.But MPPSK signal is being carried out while " filtering of code check territory " eliminate co-channel interference, neighbour frequently interference and adjacent frequency interference very far away, bandreject filtering receives process and can filtering adjacent frequency far away disturb, this feature is also just making the present invention can obtain higher adjacent frequency or co-channel interference Signal segregation degree, and detailed process is as follows:

1) impact filtering

Once mentioned in " background technology ", shock filter can adopt digital filter or analog filter to realize, the latter can elevator system performance larger, and the requirement to ADC great dynamic range and high sampling rate can be avoided again, therefore the present embodiment can adopt crystal filter design to obtain shock filter.

2) coherent carrier extracts

Although the MPPSK modulation signal received is subject to adjacent frequency or co-channel interference, but still containing stronger sinusoidal carrier, the Costas phase-locked loop that the present embodiment adopts this area as shown in Fig. 5 (a) conventional, therefrom extract pure and with the carrier signal of phase-locked loop input signal with frequently homophase, as shown in Fig. 5 (b), modulate the coherent demodulation of impact filtering signal envelope for follow-up MPPSK.

3) coherent demodulation

The MPPSK aliasing signal exported by impact filtering in multiplier and the local coherent carrier signal multiplication extracted, carry out coherent demodulation owing to taking full advantage of carrier energy, therefore be expected the demodulation performance of lifting to MPPSK modulation signal further.In addition, after being multiplied with coherent carrier, the frequency spectrum of MPPSK aliasing signal is shifted to the base band near zero-frequency, carries out process lay a good foundation for ease of follow-up link in base band.

4) " filtering of code check territory " and band stop filter

After coherent demodulation, the output signal of multiplier is still useful MPPSK Received signal strength and the mixing (superposition) of adjacent frequency or the impact filtering signal envelope with the 4FSK of strong jamming frequently signal, the two complete aliasing in time waveform, frequency spectrum also overlaps substantially, therefore the present invention's transmission code rate of just requiring MPPSK to modulate at the beginning of the design to MPPSK digital handset modulation parameter is numerically higher than existing digital handset channel spacing, again due to just required demodulating information can be rebuild with frequency spectrum MPPSK main lobe is positioned between 1 times of fundamental frequency to 8 ~ 10 times of fundamental frequencies, therefore both the present embodiment designs difference 3 times.Because 4FSK signal is divided into adjacent frequency to disturb and co-channel interference to native system interference, adjacent frequency interference can be subdivided into: neighbour is interference frequently, adjacent frequency interference far away, and adjacent frequency very far away disturbs 3 kinds.

1. co-channel interference, neighbour interference frequently and adjacent frequency interference very far away

This 3 kinds of situations are disturbed for co-channel interference, neighbour interference frequently and adjacent frequency very far away, from frequency spectrum, within the fundamental frequency that interference signal drops on MPPSK modulation signal and outside 10 times of fundamental frequencies, band pass filter now can be adopted to extract useful MPPSK Received signal strength " code check territory " (being still frequency domain in essence), and isolate 4FSK modulated interferer signal.In the present embodiment, design co-channel interference scene 1 and neighbour interference frequently and neighbour very far away disturb and deposit scene 2 and emulate:

Co-channel interference scene 1: only there is a road with 4FSK interference frequently, 4FSK carrier frequency is F _c=4.8MHz

Under this scene, native system receiving terminal: MPPSK modulation signal, after impact filtering and coherent demodulation process, obtains the power spectrum of Fig. 6, because the carrier frequency of MPPSK with 4FSK is identical, so be multiplied by carrier wave f _cafter, the frequency spectrum of MPPSK signal and 4FSK signal all moves zero-frequency, and now near zero-frequency, the bandwidth of 4FSK becomes its baseband bandwidth:

B _{4FSK base band}=B _4FSK/ 2=6.25kHz

Due to the code check R of MPPSK _b=37.5kHz > B _{4FSK base band}, so fundamental frequency (i.e. R on MPPSK main lobe _b) more than frequency spectrum resource do not disturb by 4FSK homogenous frequency signal.

Neighbour's interference frequently and neighbour very far away disturb and deposit scene 2:4 road neighbour 4FSK interference frequently and disturb with 1 tunnel adjacent frequency 4FSK very far away

1st road 4FSK signal carrier frequency: F _c1=f _c-12.5kHz/2-12.5kHz=4.78125MHz

2nd road 4FSK signal carrier frequency: F _c2=f _c-12.5kHz/2=4.79375MHz

3rd road 4FSK signal carrier frequency: F _c3=f _c+ 12.5kHz/2=4.80625MHz

4th road 4FSK signal carrier frequency: F _c4=f _c+ 12.5kHz/2+12.5kHz=4.81875MHz

5th road 4FSK signal carrier frequency: F _c5=f _c+ 32*12.5kHz=5.2MHz

Under this scene, native system receiving terminal: MPPSK modulation signal after impact filtering and coherent demodulation process, because MPPSK signal is different with the carrier frequency of 5 road 4FSK signals, so be multiplied by carrier wave f _cafter, MPPSK signal spectrum moves zero-frequency, but due to the carrier frequency of 2 and 3 road 4FSK signals | F _c2orc3-f _c|=6.25kHz, so 2 roads and 3 road 4FSK move near 6.25kHz, it is B that left and right keeps bandwidth constant _4FSK=12.5kHz.1 road and 4 road 4FSK signal carrier frequency simultaneously | F _c1orc4-f _c|=18.75kHz, so move near 18.75kHz, it is B that left and right keeps bandwidth constant _4FSK=12.5kHz.For MPPSK base band frequency, the adjacent frequency interfering frequency scope " 0 ~ B of 1 ~ 4 road 4FSK signal _{4 road 4FSK low frequencies}" wherein B _{4 road 4FSK low frequencies}=2*B _4FSK=25kHz, due to R _b=37.5kHz > B _{4 road 4FSK low frequencies}, the adjacent frequency interference of this 1 ~ 4 road 4FSK can be obtained thus all at the fundamental frequency R of MPPSK _bwithin.

Meanwhile, the carrier frequency of the 5th road 4FSK signal | F _c5-f _c|=400kHz, so the 5th road 4FSK signal is moved near 400kHz, left and right keeps bandwidth B _4FSK=12.5kHz.The interfering frequency scope of 5 road 4FSK signals to MPPSK signal is " (400-6.25) kHz ~ (400+6.25) kHz " i.e. 393.75kHz ~ 406.25kHz.Due to 393.75kHz > 10*R _b, so the adjacent frequency interference of the 5th road 4FSK signal drops on 10*R _boutside, spectrum distribution is as shown in Figure 7.

Through above-mentioned analysis, within the fundamental frequency that the 4FSK of scene 1 and scene 2 interference all drops on MPPSK modulation signal and outside 10 times of fundamental frequencies, therefore when native system receives MPPSK signal, the passband that can design its band pass filter is " R _b~ 10*R _b"; as the left and right cut-off frequency of this band pass filter, then wish that its close corresponding band connection frequency of trying one's best is with more filtering interference signals, namely makes transition band narrower more precipitous; this will increase design difficulty simultaneously, therefore needs when specific implementation the condition such as combination property and cost to take the circumstances into consideration to accept or reject.Above-mentioned design filtering 4FSK interference signal as far as possible while then can ensureing to keep useful information to the full extent.This band pass filter all can realize with numeral or analog form, and consider the needs to reducing ADC dynamic range and sample rate requirement, the present embodiment can adopt crystal filter to realize.

2. adjacent frequency interference far away

Above-mentioned " filtering of code check territory " processing method can only filtering co-channel interference, neighbour's frequently interference and adjacent frequency disturbed condition very far away, but under there is adjacent frequency disturbed condition far away, " filtering of code check territory " can not remove interference signal, therefore propose the receiving handling method of " filtering of code check territory " and the combination of suitable band stop filter in the present invention, higher adjacent frequency or co-channel interference Signal segregation degree can be obtained.Wherein " filtering of code domain rate " filtering co-channel interference, neighbour interference frequently and adjacent frequency interference very far away, designs suitable band stop filter filtering adjacent frequency interference far away simultaneously.

In the present embodiment, for there is adjacent frequency disturbed condition far away, designing adjacent frequency far away interference and there is scene 3 and emulate.

There is scene 3:4 road neighbour 4FSK signal disturbing and a great distance adjacent frequency 4FSK signal disturbing frequently in adjacent frequency interference far away, wherein 1 ~ 4 road 4FSK signal is identical with scene 2.

1st road 4FSK signal carrier frequency: F _c1=f _c-12.5kHz/2-12.5kHz=4.78125MHz

2nd road 4FSK signal carrier frequency: F _c2=f _c-12.5kHz/2=4.79375MHz

3rd road 4FSK signal carrier frequency: F _c3=f _c+ 12.5kHz/2=4.80625MHz

4th road 4FSK signal carrier frequency: F _c4=f _c+ 12.5kHz/2+12.5kHz=4.81875MHz

6th road 4FSK signal carrier frequency: F _c6=f _c+ 6*12.5kHz=4.875MHz

Under this scene, native system receiving terminal: MPPSK modulation signal is after impact filtering and coherent demodulation process, and 1st ~ 4 road 4FSK signals are identical with 1 ~ 4 tunnel in scene 2, therefore adopt the band pass filter identical with scene 2, carry out " filtering of code check territory " process, frequency spectrum as shown in Figure 8.

But for the carrier frequency on the 6th tunnel | F _c6-f _c|=75kHz, so move near 75kHz, the signal bandwidth due to 4FSK is B _4FSK=12.5kHz, so the adjacent frequency signal of the 6th road 4FSK signal is " (75-B to the interference range of MPPSK base band frequency _4FSK/ 2) kHz ~ (75+B _4FSK/ 2) kHz ", i.e. 68.75kHz ~ 81.25kHz, its interference is at " the 1.5R of MPPSK _b~ 2.5R _b" between, drop on R _b~ (8 ~ 10) R _bbetween, have impact on the demodulation performance of MPPSK, the bandwidth of rejection of band stop filter should slightly larger than adjacent frequency jamming signal bandwidth far away as requested, stopband attenuation is at least greater than-40dB, therefore the present embodiment adopts the stopband range of band stop filter to be " 64.75kHz ~ 85.25kHz ", stopband attenuation-50dB, with the monkey chatter far away of the 4FSK signal on filtering the 6th tunnel, frequency spectrum as shown in Figure 9, then wish that left and right cut-off frequency is tried one's best near corresponding stop-band frequency with the MPPSK signal remained with simultaneously, namely make transition band narrower more precipitous, this band pass filter transition band design principle with " filtering of code check territory " is consistent, repeat no more.

5) MPPSK signal correction demodulation

After the reception process combined through above-mentioned " filtering of code check territory " and band stop filter, the frequency spectrum of MPPSK signal has been limited in narrower base band frequency range, and thus ADC sample frequency now can reduce greatly, and reduces the operand of correlation demodulation simultaneously.We can retain one section of sequence of impacts m (t) after bandpass filtering as related operation template or matched filtering impulse response at receiving terminal, be used for bandpass filtering after signal in code element 0,1,2...M-1 or 1,2,3...M impact occurs that integration judgement is carried out after being multiplied respectively in position, by the MPPSK code element of integrated value the maximum judgement for demodulating wherein.

6) DMR digital handset receiving terminal 4FSK signal receiving

Native system carries out in " plug hole " transmitting procedure, is the nearest right boundary of 4FSK signal channel to the most serious conditions of the interference of DMR digital handset.From 4FSK channel more away from MPPSK signal, disturb less.Therefore in the present embodiment, just only emulate for the most serious situation of interference.For DMR digital handset receiving terminal, before 4FSK signal receiving, only need get final product the interference of filtering native system through a band pass filter.The passband width of this filter is close with DMR digital handset channel spacing, and stopband attenuation is the bigger the better.In the present embodiment, the bandwidth of this band pass filter is 12.5kHz, and stopband attenuation is that-50dB, 4FSK demodulation adopts orthogonal differential demodulation.

3, simulation result

The present embodiment will verify the transmission performance of native system mainly for error rate index.

Above-mentioned according to being divided into 3 scenes under disturbance signal: co-channel interference scene 1, neighbour's frequently interference and very far away adjacent disturb and deposits scene 2 and adjacent frequency far away disturb and there is scene 3.The present embodiment is analyzed from the MPPSK ber curve different carrier/interface ratio native system demodulation performance.

1) co-channel interference scene 1 and neighbour interference frequently and neighbour very far away disturb and deposit scene 2

From Figure 10 and Figure 11, the demodulation performance well about 1.5dB under the MPPSK signal receiving Performance Ratio AWGN of native system, the band mainly in " filtering of code check territory " leads to stripper can not only filtering 4FSK interference signal, also filtering noise more.Known under co-channel interference, neighbour interference frequently and adjacent frequency interference very far away, pass through " filtering of code domain rate " 4FSK interference and MPPSK signal can be separated completely.Simultaneously along with the power increase of 4FSK signal, carrier/interface ratio reduces, as long as the stopband attenuation of band pass filter is enough large, and also basic energy filtering 4FSK signal, thus do not affect MPPSK signal receiving.

2) there is scene 3 in adjacent frequency interference far away

As shown in Figure 12, under 5 road 4FSK adjacent frequency are disturbed altogether, the 4FSK neighbour interference frequently on 1st ~ 4 tunnels (is numerically MPPSK chip rate R in MPPSK fundamental frequency _b) in interference, by bandpass filtering remove, the modulation intelligence of MPPSK signal is substantially unaffected.

But the 4FSK on the 6th tunnel interference far is frequently at MPPSK signal fundamental frequency R _b~ (8 ~ 10) R _binterior interference, needs to arrange specific bandreject filtering filtering.Because the 6th road 4FSK interference is after all in the useful information band limits of MPPSK, how many demodulation all having influence on MPPSK, so demodulation performance is inferior to classical awgn channel demodulation performance, but within the scope of acceptable, performance loss can be compensated by chnnel coding.Simultaneously along with the increase of carrier/interface ratio, as long as the stopband decline of band stop filter is enough large, can filtering 4FSK adjacent frequency interference signal far away substantially, on the demodulation performance impact of MPPSK signal not quite.

For under adjacent frequency interference far away, namely 4FSK signal disturbing is at the fundamental frequency R of MPPSK _b~ (8 ~ 10) * R _binterior situation, understand some performance loss, so the present embodiment adopts convolutional encoding to compensate, Channel coding parameters is: convolution code (2,1,9), the Viterbi decoding of hard decision, simulation result is as shown in Figure 13, convolution code promotes the demodulation performance of MPPSK, make the performance that it is better than at awgn channel, at about error rate 10e-3, the demodulation performance of the 7dB that has an appointment promotes.

3) demodulation performance of DMR digital handset

The present embodiment adopts the native system in " MPPSK demodulator " described in the 6th trifle to emulate the most serious conditions of the interference of DMR digital handset, and wherein the ber curve of 4FSK as shown in figure 14.As shown in Figure 14, under awgn channel condition and when not adopting any chnnel coding, the MPPSK signal in certain power bracket is little to 4FSK interference, does not substantially affect existing digital handset communication.

Above result shows, the digital handset system based on MPPSK modulation that the present invention proposes is a kind of novel digital handset system, there is high spectrum utilization, the frequency spectrum space of existing digital handset can be utilized to carry out " plug hole " transmission, solve the present situation of frequency spectrum resource shortage.The most key, the reception processing mode that native system combines by means of only exclusive " filtering of code check territory " of MPPSK and suitable bandreject filtering, just can obtain high adjacent frequency or with isolation frequently, ensure that the reliable communication of native system, thus have important practical value.

The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (8)

1., based on a digital handset system for MPPSK modulation, described MPPSK is modulated at code-element period [0 a, T=NT _c] expression formula as follows:

$s_k\left(t\right)=\left\{\begin{array}{ccc}{\mathrm{sin\&omega;}}_{c}t,& 0\&le;t<{\mathrm{NT}}_c,& k=0\\ \left\{\begin{array}{c}{\mathrm{sin\&omega;}}_{c}t,\\ -{\mathrm{sin\&omega;}}_{c}t,\\ {\mathrm{sin\&omega;}}_{c}t,\end{array}\right.& \begin{array}{c}0\&le;t\&le;\left(k-1\right)\left(K+r_g\right)T_c,\\ \left(k-1\right)\left(K+r_g\right)T_c<t<\&lsqb;\left(k-1\right)\left(K+r_g\right)+K\&rsqb;T_c,\\ \left(k-r_g\right){\mathrm{KT}}_c\&le;t<{\mathrm{NT}}_c,\end{array}& 1\&le;k\&le;M-1\end{array}\right.---\left(1\right)$

Wherein, ω _c=2 π f _cfor the angular frequency of modulated carrier, T _c=2 π/ω _cfor carrier cycle, 0≤r _g<1 is the symbol protection Separation control factor, and M, N, K are integer, it is characterized in that: the MPPSK modulation described in use is as the physical layer modulation demodulation mode of digital handset, and chip rate R _b=f _c/ N is at least higher than 12.5kHz.

2. digital handset system according to claim 1, it is characterized in that: according to the particular frequency spectrum characteristic of MPPSK modulation signal, this system utilizes the spectral slots in existing digital handset system, or the idle frequency spectrum between adjacent channel, plug hole transmission of one line high speed intercommunication information.

3. digital handset system according to claim 1, is characterized in that: the adjacent frequency or the co-channel interference elimination that complete existing digital handset at the receiving terminal digital baseband of this system, can ensure proper communication.

4. digital handset system according to claim 1, is characterized in that: the digital modulation signals in this system adopts multielement positional phase shift keying, and the expression formula of described multielement positional phase shift keying is such as formula shown in (1):

1) N=(M-1) * K, force down its power spectrum sidebands levels with the line spectrum eliminated in described MPPSK modulation signal power spectrum, ensure that native system is little to the interference of other digital handsets of neighboring trace while plug hole transmission is carried out in digital handset channel space;

2) described multielement positional phase shift keying modulation signal transmission code rate is at least higher than existing digital handset channel spacing.

5. digital handset system according to claim 3, is characterized in that: receiver comprises following steps in the method for adjacent frequency or co-channel interference that digital baseband eliminates other digital handsets:

1) first carrying out impact filtering to the aliasing signal of received MPPSK modulation signal and interference, is that stronger parasitic amplitude modulation is impacted by the phase place change transitions of non-zero code element in described MPPSK modulation signal;

2) be multiplied by the suppression of coherent carrier, bandpass filtering, correlation demodulation and suitable bandreject filtering method to adjacent frequency or with other digital handset interference signals frequently to impacting filtered output signals combination, and reliably demodulate MPPSK signal.

6. digital handset system according to claim 3, is characterized in that: for the co-channel interference (f of other digital handsets _c=F _c), neighbour's frequently interference (| F-f _c| <R _b), adjacent frequency interference very far away (| F-f _c| >10*R _b), adopt described reception processing procedure to carry out interference and eliminate, wherein the left cut-off frequency of band pass filter should be greater than zero-frequency, and band connection frequency is set to R _b~ ￣ (8 ~ ￣ 10) * R _b, left and right stopband attenuation should be tried one's best greatly simultaneously, to utilize the spectrum distribution difference filtering interference signals receiving MPPSK signal and existing digital handset signal, wherein F _cfor the carrier frequency of other digital handsets, F is the interference spectrum of other digital handsets.

7. a kind of digital handset system based on MPPSK modulation according to claim 3, is characterized in that: for the adjacent frequency interference (R far away of other digital handsets _b≤ | F-f _c|≤10*R _b), adopt suitable bandreject filtering to eliminate, wherein the bandwidth of rejection of band stop filter should slightly larger than adjacent frequency jamming signal bandwidth far away, and stopband attenuation is at least greater than-40dB.

8. according to claim 3, 5, digital handset system in 6 or 7 described in any one, it is characterized in that: described receiving terminal is after eliminating adjacent frequency or the digital handset interference signal with frequency, utilize the whole surge waveform sample sequence of broadening after bandpass filtering prestored as related operation template or matched filtering impulse response, slip fixed step size is to code element 0 successively, 1, or code element 1 2...M-1, 2, 3...M impact there is position after, be multiplied with the MPPSK Received signal strength of the current symbol after bandpass filtering respectively and carry out integration judgement, integrated value the maximum is demodulated into corresponding transmission code element.