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CPM modulation digital realization method based on table lookup method and digital CPM modulation module
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An implementation method, a technology of look-up table method, applied in the direction of digital transmission system, modulated carrier system, phase-modulated carrier system, etc., can solve the problems of high complexity and inability to accommodate the phase information of modulated signals
Active Publication Date: 2016-06-01
BEIJING RES INST OF TELEMETRY +1
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49 pages-51 pages) introduced a binary continuous phase IF modulator based on DDS, used 4 trigonometric function look-up tables, 4 multipliers and 2 adders in the implementation process of CPM baseband modulation, the complexity is relatively Higher, and can only achieve binary full response CPM modulation with a single modulation index
In the implementation process, two trigonometric function lookup tables and one phase lookup table are used. Compared with the previous paper, storage resources and multiplication resources are saved, and the implementation complexity is relatively low. There is no corresponding implementation method for the longer multi-ary CPM modulation, such as multi-exponential CPM modulation form ARTMCPM, SOQPSK-TG modulation with correlation length L=8, etc. In addition, a phase lookup table may not be able to accommodate the modulation signal phase information, which the paper did not analyze
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Embodiment 1
[0140] For the PCM / FM modulation system, M=2, L=1, R=1, single modulation index, h=0.7, the baseband signal phase expression is as follows:
[0143] q ( t ) = 0 , t ≤ 0 ∫ 0 t g ( τ ) d τ , 0 ...
Embodiment 2
[0160] For the ARTMCPM modulation system, M=4, L=3, R=2, h∈{4 / 16,5 / 16}, the phase expression of the baseband signal is as follows:
[0161]
[0162] where a i ∈ {±1,±3}, h (i) Alternately equals 4 / 16 or 5 / 16, where the subscript (i) means i modulo 2. The expressions of phase pulse function q(t) and frequency pulse function g(t) are as follows:
[0163] q ( t ) = 0 , t ≤ 0 ∫ 0 t g ( τ ) d τ ...
Embodiment 3
[0182] For the SOQPSK-TG modulation system, M=3, L=8, R=1, single modulation index, h=0.5, the baseband signal phase expression is as follows:
[0183]
[0184] where a i ∈{±1,0}, it is through the binary bit data b i obtained by precoding. b i ∈{0,1}, the corresponding relationship between the two is shown in Table 4 below.
[0185] Table 4{b n} with {a n} mapping relationship
[0186]
[0187] The expressions of phase pulse function q(t) and frequency pulse function g(t) are as follows:
[0188] q ( t ) = 0 , t ≤ 0 ∫ 0 t g ...
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Abstract
The invention relates to a CPM modulation digital realization method based on a table lookup method and a digital CPM modulation module. The method comprises the steps that (1) the instantaneous phase of a CPM baseband modulation signal is composed of two parts of a correlation phase and an accumulation phase, correlation phase information is stored in a phase table in advance, and the correlation phase of the signal is obtained by looking up the table; (2) an accumulator performs continuous accumulation of phase increment so that the accumulation phase is obtained; (3) the correlation phase and the accumulation phase are added so that the instantaneous phase of the CPM baseband modulation signal can be obtained; and (4) the CPM baseband modulation signal is obtained by looking up a sine table and a cosine table according to the phase information of the CPM modulation signal. According to the method, realization is easy, complexity is low and range of application is wide, and the established phase table is correlated with sampling time so that continuity of the CPM modulation phase can be guaranteed, and realization precision is high and thus use of coherent demodulation is facilitated for a receiver.
Description
technical field [0001] The invention relates to a digital realization method of CPM modulation based on a look-up table method and a digital CPM modulation module, belonging to the technical field of digital signalprocessing. Background technique [0002] The CPM modulation system is a modulation method with constant envelope and continuous phase, which has high bandwidth and spectrum utilization efficiency, and because of its constant envelope, it is robust to the nonlinear power amplifier of the receiver, and has a wide application prospect. [0003] According to the different modulation parameters such as CPM modulation signal symbol base number, correlation length, modulation index and phase pulse function, CPM modulation has many different manifestations. Such as PCM / FM, GMSK, SOQPSK and multi-index CPM, etc. [0004] At present, the relatively direct implementation method is to first calculate the phase information of the modulated signal according to the expression ...
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