CN103546409A - Continuous phase QPSK (quadrature phase shift keying) modulation method and device - Google Patents
Continuous phase QPSK (quadrature phase shift keying) modulation method and device Download PDFInfo
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Abstract
The invention discloses a continuous phase QPSK (quadrature phase shift keying) modulation device. The continuous phase QPSK modulation device comprises a data change detector, a frequency selector, a carrier phase control word generator, an additional accumulated phase control word generator, a noise gate, a phase control word calculator, a phase control word accumulator and an ROM (read only memory) lookup table. The continuous phase QPSK modulation device is simple in structure and easy to implement. The invention further discloses a continuous phase QPSK modulation method. In the continuous phase QPSK modulation method, continuity of modulation waveforms is realized by smoothly transiting continuous transitional waveforms of a data waveform phase to the modulation waveforms of the current data, phase jump existing in the modulation waveforms of transmitted data before and after adjacent clocks is eliminated, and accordingly, pulse response caused by jumping phases is eliminated, symbol rate information contained in waveform signals is hidden, and communication safety and confidentiality are improved.
Description
Technical field
The present invention relates to a kind of modulator approach, particularly a kind of quaternary phase shift keying of continuous phase (Quadrature Phase Shift Keying is called for short QPSK) modulator approach.
Background technology
Phase shift keying (Phase Shift Keying is called for short PSK) is a kind of modulation technique that represents input signal information by carrier phase, utilizes phase place to change and carrys out transmitting digital information.In IS-95 and the two-phase PSK using in IMT-2000 (Binary Phase Shift Keying, abbreviation BPSK), quarternary phase-shift keying (QPSK) (Quadri Phase Shift Keying, be called for short QPSK) and offset quadraphase shift keying (Offset QPSK, abbreviation OQPSK) etc. all belong to phase shift keying modulation system.
While adopting phase shift keying technology to carry out signal modulation, phase place variation happens suddenly.In QPSK, the carrier signal of transmission has 4 desirable phase values, can be expressed as
, wherein
for initial phase place value, and
.Therefore, when sending data and change, the carrier phase difference of adjacent transmission data may be ± pi/2, ± π or ± 3 pi/2s.Because phase place changes, happen suddenly, therefore at SPA sudden phase anomalies point, to understand the inevitably very large impulse response of introducing, these impulse responses be similar to impulse function (
function), there is very strong frequency spectrum observability, greatly increased signal and intercepted and captured the probability with demodulation.Meanwhile, SPA sudden phase anomalies can cause system spectrum broadening, and when Bandwidth-Constrained, video stretching impels modulation signal envelope to change.In addition, PSK is higher to the linearity of amplifier, and then to the having relatively high expectations of modulating equipment, improves the cost of communication equipment.
The above-mentioned defect existing for PSK modulation system, this area researcher has proposed Continuous Phase Modulation (Continuous Phase Modulation is called for short CPM) modulation system.CPM modulation system is that information data is included in instantaneous carrier phase place or frequency, utilizes phase place memory effect to guarantee that carrier phase is all continuous at any time, thereby has avoided SPA sudden phase anomalies.The class modulation technique greatly that CPM modulation system has comprised that carrier phase changes with conitnuous forms, minimum shift keying (the Minimum Shift Keying for example using in current Generation Mobile Telecommunication System, abbreviation MSK), GMSK (Guassian Minimum Shift Keying) (Gaussian Minimum Shift Keying is called for short GMSK) is exactly common CPM modulation system.CPM modulation system has been avoided SPA sudden phase anomalies, compares with PSK modulation system, and CPM has better spectral characteristic, and power spectrum is more concentrated; The modulation signal envelope of CPM is constant simultaneously, and nonlinear amplifier easy to use, has reduced equipment cost.But, compare with linear modulation, the concrete form of CPM signal is not only relevant with moulding pulse, also relevant with the value of modulation index h, frequency response function pulse correlation length L, therefore CPM modulation system, than general linear modulation (as PSK) complexity, has increased the implementation complexity of modulating equipment.
Summary of the invention
The object of the invention is to overcome problem and the higher deficiency of CPM modulation system implementation complexity of the SPA sudden phase anomalies that in prior art, existing PSK modulation system exists, a kind of continuous phase QPSK modulator approach and modulating device thereof are provided, this modulator approach can overcome the shortcoming of the strong frequency spectrum observability of signal waveform that in PSK modulation system, phase hit causes, and the apparatus structure of realizing this modulator approach is simple, and complexity is low.
In order to realize foregoing invention object, the invention provides following technical scheme:
A QPSK modulating device, comprising:
Data variation detector, sends data for detection of present clock whether identical with adjacent last clock transmission data, and according to testing result output unlike signal;
Frequency selector, for selecting the required carrier frequency of output modulation;
The carrier phase control word generator being connected with frequency selector, described carrier phase control word generator is for producing carrier phase control word according to selected carrier frequency;
The extra cumulative phase control word generator being connected with frequency selector, described extra cumulative phase control word generator is for generation of extra cumulative phase control words;
Gate, described gate is connected with extra cumulative phase control word generator with described data variation detector respectively, and described gate is for gating the outer phase control words of amount of exports;
Phase control words calculator, described phase control words calculator is connected with carrier phase control word generator with gate respectively, described phase control words calculator, for carrier phase control word and extra phase control words are carried out to addition calculation, obtains phase control words step-length;
The phase control word accumulator being connected with phase control words calculator, described phase control word accumulator is cumulative for phase control words step-length, obtains total phase control words, and this total phase control words is the address of ROM look-up table, and R0M is delivered to in this address;
The ROM look-up table that the degree of depth being connected with phase control word accumulator is K, described ROM look-up table is for storing the sinusoidal waveform value of discretization.
According to embodiments of the invention, it is identical with adjacent last clock transmission data that described data variation detector detects present clock transmission data, output signal first signal, otherwise according to the phase difference value between adjacent transmission data waveform, export unlike signal: if phase difference value is pi/2 or-3 pi/2s, export secondary signal; If phase difference value is ± π to export the 3rd signal; If phase difference value be 3 pi/2s or-pi/2, export the 4th signal.
According to embodiments of the invention, if data variation detector output first signal, described gate output zero control word; If data variation detector output secondary signal, gate continuous wave output M extra cumulative phase control words; If data variation detector output the 3rd signal, gate continuous wave output 2 * M extra cumulative phase control words; If data variation detector output the 4th signal, gate continuous wave output 3 * M extra cumulative phase control words, wherein, the implication of described M is: the phase place that additionally adds up after M clock cycle reaches pi/2.
A kind of continuous phase QPSK modulator approach, the method is based on Direct Digital frequency synthesis, by extra cumulative phase control words, directly change the mode of control word, utilize the transition waveform continuous with previous data waveform phase place to be smoothly transitted into the modulation waveform of current data, realize the continuity of modulation waveform, its concrete steps comprise:
Step 1: carrier phase control word generator, according to the selected carrier frequency of frequency selector, produces carrier phase control word; Extra cumulative phase control word generator, according to the selected carrier frequency of frequency selector and transition waveform length M, produces extra cumulative phase control words;
Step 2: whether the data that data variation detector detection present clock sends are identical with the data that adjacent last clock sends, if identical, export first signal, and enter step 4; Otherwise enter step 3;
Step 3: calculate the phase difference value between adjacent transmission data waveform, if phase difference value is pi/2 or-3 pi/2s, export secondary signal; If phase difference value is ± π to export the 3rd signal; If phase difference value be 3 pi/2s or-pi/2, export the 4th signal, enter step 4;
Step 4: gate is according to the output signal gating of data variation monitor the outer phase control words of amount of exports, if the output signal of data variation monitor is first signal, the outer phase control words of gate amount of exports is zero control word; If data variation detector output signal is secondary signal, gate continuous wave output M extra phase control words is extra cumulative phase control words; If data variation detector output signal is the 3rd signal, gate continuous wave output 2 * M extra phase control words is extra cumulative phase control words; If data variation detector output signal is the 4th signal, gate continuous wave output 3 * M extra phase control words is extra cumulative phase control words;
Step 5: phase control words calculator is added carrier phase control word and extra phase control words, obtains phase control words step-length;
Step 6: it is cumulative that phase control word accumulator carries out phase control words step-length, obtains total phase control words, obtains the ROM look-up table address of each clock;
Step 7: the look-up table address producing according to step 6, in ROM, search the modulation waveform signal value of present clock, and this modulation waveform signal value is exported;
Step 8: whether the total phase control words that judges the output of phase control word accumulator reaches ROM look-up table address higher limit, if reach higher limit, enters step 9; If do not reach higher limit, enter step 10;
Step 9: by total phase control words zero clearing in phase control word accumulator, enter step 10;
Step 10: judge whether reach the one-period of original modulation waveform running time, if reach, finish the modulation of current data, if do not reach, return to step 6, proceed total phase control words cumulative.
According to embodiments of the invention, described in step 1, the computational methods of extra cumulative phase control words are: establish extra cumulative phase place after M clock cycle and reach pi/2,
, additionally cumulative phase step is
, additionally cumulative phase control words is
, wherein, the implication of K is: the degree of depth of ROM look-up table.
According to embodiments of the invention, described M value is
, wherein, the implication of N is: the sinusoidal carrier signal that adopts N discrete sample signals value representation one-period.
According to embodiments of the invention, the computational methods of the control word of carrier phase described in step 1 are: suppose to adopt
the sinusoidal carrier signal of individual discrete sample signals value representation one-period, the phase difference between two adjacent discrete sampling points is
, carrier phase control word is
.
compared with prior art, beneficial effect of the present invention:
1, continuous phase QPSK modulator approach of the present invention, based on Direct Digital frequency synthesis, by extra cumulative phase control words, directly change the mode of control word, produce the discontinuous waveform that transition waveform replaces phase hit in traditional Q PSK modulation, realized the continuity of modulation waveform, before and after having eliminated adjacent clock, send the phase hit existing in the modulation waveform of data, thereby eliminated the impulse response producing because of SPA sudden phase anomalies, the hidden symbol rate information containing in waveform signal, has increased fail safe and the confidentiality of communication.
2, continuous phase QPSK modulator approach of the present invention is compared with CPM modulator approach, the value of the concrete form of the modulation signal of employing the inventive method and moulding pulse, modulation index h, frequency response function pulse correlation length L is irrelevant, so it is low to realize the complexity of modulator approach of the present invention, more easily realize, modulating equipment is simple in structure, and cost is low.
Accompanying drawing explanation:
Fig. 1 is the structured flowchart of continuous phase QPSK modulating device of the present invention.
Fig. 2 is the FB(flow block) of continuous phase QPSK modulator approach of the present invention.
Fig. 3 (a), Fig. 3 (b) and Fig. 3 (c) are for adopting the modulation waveform figure of continuous phase QPSK modulator approach of the present invention in embodiment.
Fig. 4 is phase difference that in embodiment, data jump causes while being pi/2, the phase place variation comparison diagram of traditional Q PSK modulation and continuous phase QPSK of the present invention modulation.
Fig. 5 is phase difference that in embodiment, data jump causes while being π, the phase place variation comparison diagram of traditional Q PSK modulation and continuous phase QPSK of the present invention modulation.
Mark in figure: 101-data variation detector, 102-gate, 103-is cumulative phase control word generator additionally, 104-frequency selector, 105-carrier phase control word generator, 106-phase control words calculator, 107-phase control word accumulator, 108-ROM look-up table.
Embodiment
Below in conjunction with test example and embodiment, the present invention is described in further detail.But this should be interpreted as to the scope of the above-mentioned theme of the present invention only limits to following embodiment, all technology realizing based on content of the present invention all belong to scope of the present invention.
Continuous phase QPSK modulator approach of the present invention realizes based on Direct Digital frequency synthesis (DDS) method, first the concise and to the point basic principle that adopts DDS to produce discrete digital modulation signal of setting forth.DDS generally includes 3 basic modules: phase control word modules, phase accumulator module and sinusoidal ROM look-up table means.Phase control words is by the determined ROM look-up table of two adjacent sampled point phase differences address increment; Phase accumulator is responsible for phase control words to carry out accumulating operation, and the total phase control words calculating is final ROM look-up table address; ROM look-up table, by carrier signal range value output corresponding to Input Address, obtains intermediate frequency digital modulation signals.
Suppose to adopt the pure oscillation signal of K discrete sample signals value representation one-period, so the phase difference between two adjacent discrete sampling points is
, the
the value of individual sinusoidal sampled signal is
,
.
it is the minimum phase precision that DDS can reach.The pure oscillation signal value of this group sampling is pre-deposited in ROM, and its address is followed successively by
, K value is the degree of depth of sine lookup table.Phase control words
by corresponding carrier wave physical frequencies
, the systematic sampling frequency while realizing
and sine lookup table degree of depth K determines jointly, its computational methods are:
Carrier wave physical frequencies
with sample frequency
between ratio be phase intervals between two neighbouring sample points of carrier wave (with
for unit metering), the phase accuracy that phase intervals can reach with DDS again
compare (being that phase intervals is divided by phase accuracy), can calculate the ROM look-up table address increment between two neighbouring sample points of carrier wave, this value is phase control words.For example, sample frequency
it is carrier wave physical frequencies
16 times time,
, so the sinusoidal carrier signal of a complete cycle of every 16 somes output of DDS.
As shown in Figure 1, continuous phase QPSK modulating device of the present invention comprises data variation detector 101, frequency selector 104, carrier phase control word generator 105, the phase control word generator 103 that additionally adds up, gate 102, phase control words calculator 106, phase control word accumulator 107 and ROM look-up table 108, wherein
Whether described data variation detector 101 sends data for detection of present clock identical with adjacent last clock transmission data, if it is identical with adjacent last clock transmission data that data variation detector detects present clock transmission data, output signal " 00 ", if it is different to send data, according to the phase difference output unlike signal between adjacent transmission data waveform: if phase difference value is pi/2 or-3 pi/2s, output signal " 01 "; If phase difference value is ± π, output signal " 10 "; If phase difference value be 3 pi/2s or-pi/2, output signal " 11 ";
Described frequency selector 104 is for selecting the required carrier frequency of output modulation.
Described carrier phase control word generator 105 is connected with frequency selector 104, for producing carrier phase control word according to the selected carrier frequency of frequency selector 104.
Described extra cumulative phase control word generator 103 is connected with frequency selector 104, and additionally cumulative phase control word generator 103 is for generation of extra cumulative phase control words.
Described gate 102 is connected with extra cumulative phase control word generator 103 with data variation detector 101 respectively, and gate is for gating the outer phase control words of amount of exports.If data variation detector 201 output signals are " 00 ", the extra phase control words of gate 102 outputs is zero control word; If data variation detector 101 output signals are " 01 ", the M of gate 102 continuous wave outputs extra phase control words is extra cumulative phase control words; If data variation detector 101 output signals are " 10 ", 2 * M of gate 102 continuous wave outputs extra phase control words is extra cumulative phase control words; If data variation detector 101 output signals are " 11 ", 3 * M of gate 102 continuous wave outputs extra phase control words is extra cumulative phase control words, and wherein, the implication of described M is: after M clock cycle, extra cumulative phase place reaches pi/2.
Described phase control words calculator 106 respectively be connected gate 102 and be connected with carrier phase control word generator 105, phase control words calculator 106, for carrier phase control word and extra phase control words are carried out to addition calculation, obtains phase control words step-length.
Described phase control word accumulator 107 is connected with phase control words calculator 106, phase control word accumulator 107 is cumulative for phase control words step-length, obtain total phase control words, this total phase control words is the address of ROM look-up table 108, and R0M is delivered to in this address;
Described ROM look-up table 108 is connected with phase control word accumulator 107, and ROM look-up table 108 is for storing the sinusoidal waveform value of discretization.
It should be noted that, K represents the degree of depth of ROM look-up table, i.e. the higher limit of ROM look-up table address.
It should be noted that, in the present embodiment, M represents: after M clock cycle, extra cumulative phase place reaches pi/2, and M also represents the fundamental length of excessive waveform.When phase difference be pi/2 or-during 3 pi/2, the excessively modulation waveform smooth connection of waveform and current data after M clock cycle; When phase difference be ± during π, the excessively modulation waveform smooth connection of waveform and current data after 2 * M clock cycle; When phase difference be 3 pi/2s or-during pi/2, the excessively modulation waveform smooth connection of waveform and current data after 3 * M clock cycle.
Also can represent with M1 the fundamental length of excessive waveform, after M1 clock cycle, extra cumulative phase place reaches π.So, when phase difference be pi/2 or-during 3 pi/2, the excessively modulation waveform smooth connection of waveform and current data after M1/2 clock cycle; When phase difference be ± during π, the excessively modulation waveform smooth connection of waveform and current data after M1 clock cycle; When phase difference be 3 pi/2s or-during pi/2, the excessively modulation waveform smooth connection of waveform and current data after 3 * M1/2 clock cycle.Same, can represent with M2 the fundamental length of excessive waveform, after M2 clock cycle, extra cumulative phase place reaches 3 pi/2s.So, when phase difference be pi/2 or-during 3 pi/2, the excessively modulation waveform smooth connection of waveform and current data after M2/3 clock cycle; When phase difference be ± during π, the excessively modulation waveform smooth connection of waveform and current data after 2 * M2/3 clock cycle; When phase difference be 3 pi/2s or-during pi/2, the excessively modulation waveform smooth connection of waveform and current data after M2 clock cycle.
M and N do not have proportionate relationship, and M can get arbitrary value, in the present embodiment, get
, N represents: the sinusoidal carrier signal that adopts N discrete sample signals value representation one-period.
With reference to figure 2, when traditional Q PSK modulates, if two adjacent data differences, can produce ± pi/2 of modulation waveform or ± π or ± the phase hit point of 3 pi/2 degree.Continuous phase QPSK modulator approach of the present invention is by extra cumulative phase control words, directly change the mode of phase control words, utilize the transition waveform continuous with previous data waveform phase place to be smoothly transitted into the modulation waveform of current data, utilize this transition waveform to replace the discontinuous waveform of phase hit in traditional Q PSK modulation, realize the continuity of modulation waveform, its concrete steps comprise:
Step 201: carrier phase control word generator, according to the selected carrier frequency of frequency selector, produces carrier phase control word; Extra cumulative phase control word generator, according to the selected carrier frequency of frequency selector and transition waveform length M, produces extra cumulative phase control words;
Suppose that extra cumulative phase place reaches pi/2 after M clock,
, additionally cumulative phase step is
, phase control words additionally adds up
; Suppose to adopt
the sinusoidal carrier signal of individual discrete sample signals value representation one-period, the phase difference between two adjacent discrete carrier sampled points is
, carrier phase step-length is
, carrier phase control word is
.
In the present embodiment, K value 128, N value is that 16, M value is
, additionally cumulative phase step is
, phase control words additionally adds up
, carrier phase step-length is
, carrier phase control word is
.
Step 202: whether data variation detector detects data that present clock sends identical with the data of adjacent last clock transmission, if identical, output signal " 00 ", and enter step 204, if different, enter step 203.
Step 203: calculate the phase difference value between adjacent transmission data carrier waveform, it is the phase value that the phase value of current data deducts last data, thereby determine gating time length, data variation detector is again according to gating time length output unlike signal: if phase difference value is pi/2 or-3 pi/2s, output signal " 01 "; If phase difference value is ± π, output signal " 10 "; If phase difference value be 3 pi/2s or-pi/2, output signal " 11 ", enters step 204.
Step 204: gate is according to the output signal gating of data variation detector the outer phase control words of amount of exports, if the output signal of data variation detector is " 00 ", the outer phase control words of gate amount of exports is zero control word; If data variation detector output signal is " 01 ", gate continuous wave output M(M=4) individual extra phase control words is extra cumulative phase control words, i.e. continuous 4 clock amount of exportss cumulative phase control words outward; If data variation detector output signal is " 10 ", gate continuous wave output 2 * M=8 extra phase control words is extra cumulative phase control words; If data variation detector output signal is " 11 ", gate continuous wave output 3 * M=12 extra phase control words is extra cumulative phase control words.
Step 205: phase control words calculator is added carrier phase control word and extra phase control words, obtains phase control words step-length.In the present embodiment, when the output signal of data variation detector is " 00 ", phase control words step-length is carrier phase control word
, corresponding phase step is carrier phase step-length
; When data variation detector output signal is " 01 " or " 10 " or " 11 ", phase control words step-length is carrier phase control word
with extra phase control words
sum,
, corresponding phase step is carrier phase step-length and extra cumulative phase step sum, for
.
Step 206: it is cumulative that phase control word accumulator carries out phase control words step-length, obtain total phase control words, it is the ROM look-up table address of each clock, its accumulation calculating method is: phase control word accumulator feeds back to the new total phase control words producing after a upper clock input of self, at next clock, continue to be added with phase control words step-length, obtain total phase control words of this clock, this total phase control words is this ROM look-up table address constantly, and input ROM is as the address of tabling look-up of modulation waveform.
Step 207: the look-up table address producing according to step 206, in ROM, search the modulation waveform signal value of present clock, and this modulation waveform signal value is exported.
Step 208: judge whether total phase control words of phase control word accumulator output reaches the higher limit of setting, in the present embodiment, judges whether total phase control words reaches 128, if reach 128, enters step 209; If do not reach 128, enter step 210.
Step 209: by total phase control words zero clearing in phase control word accumulator, enter step 210.
Step 210: judge whether reach the one-period of original modulation waveform running time, if reach, finish the modulation of current data, if do not reach, return to step 206, proceed total phase control words cumulative.
With reference to figure 3 (a), Fig. 3 (b) and Fig. 3 (c), suppose once to transmit data variation when modulating signal phase is 4 π, for example, shown in Fig. 3 (a), the phase place of traditional Q PSK modulation waveform (dotted line waveform in Fig. 3 (a)) has the saltus step that a size is pi/2, as shown in A point in Fig. 3 (a); Again for example, shown in Fig. 3 (b), the phase place of traditional Q PSK modulation waveform (dotted line waveform in Fig. 3 (b)) has the saltus step that a size is π, as shown in B point in Fig. 3 (b); Again for example, shown in Fig. 3 (c), it is the saltus step of 3 pi/2s that the phase place of traditional Q PSK modulation waveform (dotted line waveform in Fig. 3 (c)) has a size, as shown in C point in Fig. 3 (c).Adopt continuous phase QPSK modulator approach of the present invention, utilize the fast transition waveform continuous with previous data waveform phase place (in Fig. 3 (a), phase place is that in solid line waveform between 4 π to 4.5 π or Fig. 3 (b), phase place is that solid line waveform or the middle phase place of Fig. 3 (c) between 4 π to 5 π is the solid line waveform between 4 π to 5.5 π) to be smoothly transitted into the modulation waveform of current data, thereby hide symbol trip point information, reduce the high fdrequency component of SPA sudden phase anomalies point.According to 2 π periodic characteristics of pure oscillation signal phase, can learn, Fig. 3 (a), Fig. 3 (b) and Fig. 3 (c) be also respectively phase difference size for-3 pi/2s ,-π and-situation during pi/2, be that phase difference is that pi/2 is consistent with the waveform of-3 pi/2s, it is consistent with the waveform of-π that phase difference is π, and it is consistent with the waveform of-pi/2 that phase difference is 3 pi/2s.
With reference to figure 4, suppose k
1total phase control words in+1 moment is 112, and signal phase is
.At k
1+ 3 and k
1between+4 clocks, once transmit the variation of data, this changes corresponding phase difference value is pi/2.Carrier phase in Fig. 4 shown in secondary series is continuous.At k
1+ 1 to k
1+ 3 clock periods, the total phase control words under the inventive method increases with step-length 8, and corresponding modulating waveform phase is with step-length
change, modulation waveform phase place is consistent with the phase preserving of traditional Q PSK modulation waveform.At k
1+ 3 clocks, in phase control word accumulator, master control word has reached higher limit 128(phase value and has reached 2 π), so total phase control words zero clearing in phase control word accumulator.K
1+ 4 clocks are to k
1between+7 clocks, in Fig. 4 the 4th row, total phase control words of traditional Q PSK modulation waveform is because of k
1the data variation of+4 clocks and the saltus step that produces pi/2, become 40 from 8, and extra address increment is K/4=32, corresponding modulating waveform phase from
jump to
, the total phase control words of all the other clocks still increases by step-length 8, and modulation waveform phase place is by step-length
increase.And there is not obvious phase hit in modulation waveform under modulator approach of the present invention, but with 16 phase control words step-length,
phase step " catch up with " waveform phase in traditional Q PSK modulation.At k
1+ 4 clocks, in phase control word accumulator, total phase control words is 16, corresponding modulation waveform phase place is
, at k
1+ 5 clocks, in phase control word accumulator, total phase control words is 32, corresponding modulation waveform phase place is
.To k
1+ 7 clocks, total phase control words under modulator approach of the present invention and modulation waveform phase place be identical with under traditional Q PSK modulation, so extra phase control words vanishing of gate output, phase control words step-length revert to carrier phase control word 8, completes the modulation waveform smooth connection with current data.
With reference to figure 5, suppose k
2total phase control words in+1 moment is 112, and signal phase is
.At k
2+ 3 and k
2between+4 clocks, once transmit the variation of data, this changes corresponding phase difference value is π.Carrier phase in Fig. 5 shown in secondary series is continuous.At k
2+ 1 to k
2+ 3 clock periods, the total phase control words under the inventive method increases with step-length 8, and corresponding modulating waveform phase is with step-length
change, modulation waveform phase place is consistent with the phase preserving of traditional Q PSK modulation waveform.At k
2+ 3 clocks, in phase control word accumulator, master control word has reached higher limit 128(phase value and has reached 2 π), so total phase control words zero clearing in phase control word accumulator.K
2+ 4 clocks are to k
2between+11 clocks, in Fig. 5 the 4th row, total phase control words of traditional Q PSK modulation waveform is because of k
2the data polarity reversion of+4 clocks and saltus step occurs, becomes 72 from 8, and extra address increment is K/2=64, corresponding modulating waveform phase from
jump to
, the total phase control words of all the other clocks still increases by step-length 8, and modulation waveform phase place is by step-length
increase.And there is not phase hit in modulation waveform under modulator approach of the present invention, but with 16 phase control words step-length,
phase step " catch up with " waveform phase in traditional Q PSK modulation.At k
2+ 4 clocks, in phase control word accumulator, total phase control words is 16, corresponding modulation waveform phase place is
, at k
2+ 5 clocks, in phase control word accumulator, total phase control words is 32, corresponding modulation waveform phase place is
.To k
2+ 11 clocks, total phase control words under modulator approach of the present invention and modulation waveform phase place be identical with under traditional Q PSK modulation, so extra cumulative phase control words vanishing of gate output, phase control words step-length revert to carrier phase control word 8, completes the modulation waveform smooth connection with current data.K
2during+11 clock, in phase control word accumulator, total phase control words has reached higher limit 128, so total phase control words zero clearing in phase control word accumulator.K
2+ 11 clocks and k
2between+12 clocks, transmit data and do not change, the control word of modulation waveform is with step-length 8, and phase place is with step-length
continue to change, so, at k
2during+12 clock, in phase control word accumulator, total phase control words is 8, and carrier phase is
.
The phase difference that data variation causes modulation waveform phase place when-3 pi/2 changes the phase place that is pi/2 with phase difference and changes unanimously, and the phase difference phase place variation that the variation of modulation waveform phase place is π with phase difference during for-π is consistent, is not repeating herein.
Same, when the phase difference that data variation causes is 3 pi/2, the modulation waveform phase place under the inventive method is with 16 phase control words step-length,
phase step " catch up with " waveform phase in traditional Q PSK modulation, until complete the modulation waveform smooth connection with current data.Phase difference is-modulation waveform phase place changes unanimously with the phase place variation of 3 pi/2s during pi/2, do not repeating herein.
Continuous phase QPSK modulator approach of the present invention, based on Direct Digital frequency synthesis, by extra cumulative phase control words, directly change the mode of control word, produce the discontinuous waveform that transition waveform replaces phase hit in traditional Q PSK modulation, realized the continuity of modulation waveform, before and after having eliminated adjacent clock, send the phase hit existing in the modulation waveform of data, thereby eliminated the impulse response producing because of SPA sudden phase anomalies, the hidden symbol rate information containing in waveform signal, fail safe and the confidentiality of communication have been increased, this modulator approach and application of installation are in the military wireless communication system of anti-intercepting and capturing, or civilian narrowband wireless communication is.
Continuous phase QPSK modulator approach of the present invention is compared with CPM modulator approach, the value of the concrete form of the modulation signal of employing the inventive method and moulding pulse, modulation index h, frequency response function pulse correlation length L is irrelevant, so it is low to realize the complexity of modulator approach of the present invention, more easily realize, modulating equipment is simple in structure, and cost is low.
Claims (7)
1. a continuous phase QPSK modulating device, is characterized in that, this modulating device comprises:
Data variation detector, sends data for detection of present clock whether identical with adjacent last clock transmission data, and according to testing result output unlike signal;
Frequency selector, for selecting the required carrier frequency of output modulation;
The carrier phase control word generator being connected with frequency selector, described carrier phase control word generator is for producing carrier phase control word according to selected carrier frequency;
The extra cumulative phase control word generator being connected with frequency selector, described extra cumulative phase control word generator is for generation of extra cumulative phase control words;
Gate, described gate is connected with extra cumulative phase control word generator with described data variation detector respectively, and described gate is for gating the outer phase control words of amount of exports;
Phase control words calculator, described phase control words calculator is connected with carrier phase control word generator with gate respectively, described phase control words calculator, for carrier phase control word and extra phase control words are carried out to addition calculation, obtains phase control words step-length;
The phase control word accumulator being connected with phase control words calculator, described phase control word accumulator is cumulative for phase control words step-length, obtains total phase control words, and this total phase control words is the address of ROM look-up table, and R0M is delivered to in this address;
The ROM look-up table that the degree of depth being connected with phase control word accumulator is K, described ROM look-up table is for storing the sinusoidal waveform value of discretization.
2. continuous phase QPSK modulating device according to claim 1, it is characterized in that, it is identical with adjacent last clock transmission data that described data variation detector detects present clock transmission data, export first signal, otherwise according to the phase difference value between adjacent transmission data waveform, export unlike signal: if phase difference value is pi/2 or-3 pi/2s, export secondary signal; If phase difference value is ± π to export the 3rd signal; If phase difference value be 3 pi/2s or-pi/2, export the 4th signal.
3. continuous phase QPSK modulating device according to claim 2, is characterized in that, if data variation detector output first signal, described gate output zero control word; If data variation detector output secondary signal, gate continuous wave output M extra cumulative phase control words; If data variation detector output the 3rd signal, gate continuous wave output 2 * M extra cumulative phase control words; If data variation detector output the 4th signal, gate continuous wave output 3 * M extra cumulative phase control words, wherein, the implication of described M is: the phase place that additionally adds up after M clock cycle reaches pi/2.
4. a continuous phase QPSK modulator approach, it is characterized in that, the method is based on Direct Digital frequency synthesis, by extra cumulative phase control words, directly change the mode of control word, the continuous transition waveform of utilization and previous data waveform phase place is smoothly transitted into the modulation waveform of current data, realizes the continuity of modulation waveform, and its concrete steps comprise:
Step 1: carrier phase control word generator, according to the selected carrier frequency of frequency selector, produces carrier phase control word;
Step 2: it is identical with adjacent last clock transmission data that data variation detector detects present clock transmission data, exports first signal, and enter step 4; Otherwise enter step 3;
Step 3: calculate the phase difference value between adjacent transmission data waveform, if phase difference value is pi/2 or-3 pi/2s, export secondary signal; If phase difference value is ± π to export the 3rd signal; If phase difference value be 3 pi/2s or-pi/2, export the 4th signal, enter step 4;
Step 4: gate is according to the output signal gating of data variation detector the outer phase control words of amount of exports, if the output signal of data variation detector is first signal, the outer phase control words of gate amount of exports is zero control word; If data variation detector output signal is secondary signal, gate continuous wave output M extra phase control words is extra cumulative phase control words; If data variation detector output signal is the 3rd signal, gate continuous wave output 2 * M extra phase control words is extra cumulative phase control words; If data variation detector output signal is the 4th signal, gate continuous wave output 3 * M extra phase control words is extra cumulative phase control words;
Step 5: phase control words calculator is added carrier phase control word and extra phase control words, obtains phase control words step-length;
Step 6: it is cumulative that phase control word accumulator carries out phase control words step-length, obtains total phase control words, obtains the ROM look-up table address of each clock;
Step 7: the look-up table address producing according to step 6, in ROM, search the modulation waveform signal value of present clock, and this modulation waveform signal value is exported;
Step 8: whether the total phase control words that judges the output of phase control word accumulator reaches ROM look-up table address higher limit, if reach higher limit, enters step 9; If do not reach higher limit, enter step 10;
Step 9: by total phase control words zero clearing in phase control word accumulator, enter step 10;
Step 10: judge whether reach the one-period of original modulation waveform running time, if reach, finish the modulation of current data, if do not reach, return to step 6, proceed total phase control words cumulative.
5. continuous phase QPSK modulator approach according to claim 4, is characterized in that, described in step 1, the computational methods of extra cumulative phase control words are: establish extra cumulative phase place after M clock cycle and reach pi/2,
, additionally cumulative phase step is
, additionally cumulative phase control words is
, wherein, the implication of K is: the degree of depth of ROM look-up table.
6. continuous phase QPSK modulating device according to claim 5, is characterized in that, described transition waveform length M value is
, wherein, the implication of N is: the sinusoidal carrier signal that adopts N discrete sample signals value representation one-period.
7. according to the continuous phase QPSK modulator approach one of claim 4 to 6 Suo Shu, it is characterized in that, the computational methods of the control word of carrier phase described in step 1 are: the degree of depth of supposing sinusoidal ROM look-up table is K, the sinusoidal carrier signal that adopts N discrete sample signals value representation one-period, the phase difference between two adjacent discrete sampling points is
, carrier phase control word is
.
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