CN100536452C

CN100536452C - Method for judging TFM signal

Info

Publication number: CN100536452C
Application number: CNB2006101135406A
Authority: CN
Inventors: 朱柏承; 孙云刚; 李翔; 张宏
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2006-09-29
Filing date: 2006-09-29
Publication date: 2009-09-02
Anticipated expiration: 2026-09-29
Also published as: CN1946070A

Abstract

This invention provides a method for judging tfm signals aiming at the character of tfm signals including: 1, setting up a histogram of restriction relation for tfm signals, 2, using the histogram and applying the mode of viterbi decode to look for the optimum path of the maximum likelihood rule then to trace it to finish the decode, which balances the system complexity and demodulation performance to get demodulation even better.

Description

The method that the TFM signal is adjudicated

Technical field

The present invention relates to communication technique field, particularly a kind of method that the TFM signal is adjudicated.

Background technology

Tamed frequency modulation, TFM (tfm) modulation technique is a kind of permanent envelope modulation technology that new development is got up, and it is narrow that it has the power spectrum main lobe, availability of frequency spectrum height, and Lin Dao disturbs characteristics such as little.But, therefore be difficult to a kind of performance excellent reception machine simple in structure of structure because intersymbol interference has been introduced in the tfm modulation.

Can obtain relation such as accompanying drawing 1 between phase increment, baseband waveform and the input data according to the characteristic of TFM signal.Traditional decision method is the data that recover modulation according to homophase, quadrature two paths of signals, i.e. intersection control by two paths of signals just can recover to send data.Concrete decision device such as the accompanying drawing 2 that adopts.

In the tfm modulation, the energy of a symbol is diffused in the scope of three code-element periods from a code-element period, has produced intersymbol interference.Traditional decision method has only been noted the energy of a symbol, has ignored two symbol energies of more less important diffusion, so this method can only just can reach the lower error rate under than the situation of high s/n ratio.

Summary of the invention

At above-mentioned analysis, the purpose of this invention is to provide a kind of method that the TFM signal is adjudicated to current TFM signal modulation technique pluses and minuses.

Above-mentioned purpose of the present invention is achieved by the following technical solutions:

A kind of method that the TFM signal is adjudicated comprises:

(1) be excitation with current input binary system TFM signal, is Status Flag with all TFM signals of past in the accumulation of phase of sampling instant, is exciter response with excitation TFM signal and all TFM signals of past in the accumulation of phase of sampling instant, makes up the restriction relation state diagram of a TFM signal;

(2) utilize above-mentioned state diagram, the mode that adopts viterbi to decode is sought out the optimal path under the maximum likelihood rule, and this path is recalled, and finishes decoding.

One is sampled point in 8 phase points of employing TFM signal, and state A and state B determine the state of state diagram jointly, and signal is N*pi/2 in the phase place contribution of sampling instant among the state A; State B to the contribution of sampling instant phase place be+3pi/8 or-3pi/8, depend on the symbol of state B signal; Excitation to the contribution of sampling instant phase place be+pi/8 or-pi/8, depend on the symbol of pumping signal.

State A can be divided into odd even and clap handle, state A initial value is 0, then odd number clap state A be pi/2 or-pi/2, clapping state A at even number is 0 or pi.

The tfm signal has stable sampled point--and the integral multiple of ∏/4, totally eight phase points are as accompanying drawing 3.And the data of modulation are because carried out pre-filtering.So correlation is arranged between the data,

The tfm signal has following characteristics: (4 explanations in conjunction with the accompanying drawings)

(putative signal is+1 o'clock to putative signal in 0 input constantly, reduce corresponding amount if signal be-1 phase place), then its phase response as shown in Figure 4, the phase place among the figure is to be accurately in sampling instant, the concrete condition that changes constantly in the centre omits to say not influence of decoding.Signal can expand in three symbol times the influence of phase place, and phase increment is 1/8pi when t=1T, and phase increment is 3/8pi when t=2T, and phase increment is 1/2pi when t＞=3T.

The required restriction relation state diagram of this method that the present invention is directed to the tfm signal configuration is used this method to choose maximum likelihood path, thereby has been collected that part of propagation energy that conventional method is not used, and has reached the improvement to traditional decision method performance.

Technique effect of the present invention is as follows:

Because there is intersymbol interference in the tfm signal, thisly crosstalk that to cause the signal in the adjacent code elementary time be not independently, the correlation of sort signal must cause the existence of certain constraint between signal.These constraints of reasonable use just can be constructed a kind of good decision method.

Technique effect such as accompanying drawing 5.Adopting after this method error performance than the improvement of the nearly 2dB of conventional method.

Description of drawings

The characteristic of Fig. 1-TFM signal can obtain the relation between phase increment, baseband waveform and the input data;

The decision device of tfm signal in Fig. 2-conventional method;

Fig. 3-tfm signals sampling point;

Fig. 4-technique effect tfm signal phase changes;

Fig. 5-the present invention adopts decision method and traditional decision method technique effect comparison diagram;

Fig. 6-tfm signal flow and Status Flag rule;

Essential state diagram during Fig. 7-viterbi decoding.

Embodiment

Describe the present invention in detail below in conjunction with accompanying drawing, but the scope that does not limit the present invention in any way.

The characteristics of comprehensive tfm signal are the base configuration state diagram with accompanying drawing 6.

Accompanying drawing 6 is done following explanation:

(1) arrow that makes progress is represented modulated binary signal (+1 or-1), the transverse axis express time, and the time interval that signal occurs is T (not marking among the figure).

(2) downward arrow is represented sampling instant, and sampled point is in 8 stable phase points.

(3) excitation the when state of structural regime figure and state redirect as shown in the figure, the phase place of state diagram is the sampling instant phase place.

(4) state A and state B determine the state of state diagram jointly.

Signal is N*pi/2 in the phase place contribution of sampling instant among the state A; State B to the contribution of sampling instant phase place be+3pi/8 or-3pi/8, depend on the symbol of state B signal; Excitation to the contribution of sampling instant phase place be+pi/8 or-pi/8, depend on the symbol of pumping signal.

State A has four kinds of selections, 0, pi/2, pi, 2pi under the situation of no any prior information.State B has two kinds of selection+3pi/8 ,-3pi/8.Final like this state has 8, the system constructing more complicated, be unfavorable for the hardware realization, and because the state here is by the natural state that does not have similar convolutional encoding that forms of the characteristics of the tfm signal mechanism that makes zero, so decipher initial equilibrium state at every turn is unknown, if state too much will inevitably increase uncertainty, reduce the performance of decoding.

In fact state A can abbreviation.The every bat of state A must change pi/2, therefore state A can be divided into odd even and clap processing.State A initial value is 0, then odd number clap state A must for pi/2 or-pi/2, clapping state A at even number must be 0 or pi.But clap just abbreviation of signal condition if therefore know the odd even of received signal.Fortunately when strange the bat sampled point must adopt less than pi/2 and-pi/2 cos road signal can not be zero, when idol is clapped sampled point adopt less than 0 and pi sin road can not be zero.Information according to this feature extraction odd even bat.What therefore actual decoding was adopted is the state diagram of one of four states.

So far network analysis is finished, and four kinds of states are arranged under the situation of abbreviation state, but four kinds of states are to change in the cycle.Cycle is 2 bats.So far, can construct as shown in Figure 7 state diagram.

Below state diagram is explained as follows:

(1): the labeling form of state is that AB is pi as " pi-" expression A condition among the figure, and the B state is-1.

(2): modulation signal is that binary signal so each state have two inputs of two output, indicates the respective phase of modulating output with blueness on every arm in the state diagram, just the signal of receiving terminal input under the noise-free case.

(3) figure top " very ", the odd even of " idol " expression current state is clapped.

So far, state diagram has been constructed and has been finished, code encoding/decoding mode structure viterbi decoder that can the analogy convolution code, and its vacuum metrics adopts the input phase and the accurate correlation of phase place to represent.Here do not give unnecessary details as for the concrete structure of viterbi decoder, only provide the basic function of the concrete module of hardware circuit realization.

Each module is as follows: 1. top-level module tfmviterbi; 2. system's beat control (each beat action of management decode procedure) counter; 3. correlation computations module corcal; 4. path calculation module tracecal; 5. recall module traceback; 6. relevant ram twoport corram; 7. path ram twoport traceram.Wherein, system's beat control is used to manage each beat action of decode procedure; The correlation computations module is used to calculate current input signal and writes with 8 correlations that may put mutually and with it; Path calculation module is used for reading the signal correlation values that corram stores, and calculates possible path and routing information is write traceram according to system state diagram.After reaching preset value, decoding length measures (relevant accumulated value) maximum branch road position to recalling module output; Recall module, after path calculation module provides the maximum metric path, from traceram, read this path and it is recalled, and obtain decoded signal; Relevant ram twoport is used for storing the correlation of viterbi decode procedure input signal and each possibility phase place; Path ram twoport is in order to all possible paths in the record viterbi decode procedure.

More than be embodiments of the present invention, according to content disclosed by the invention, those of ordinary skill in the art can identical, the replacement scheme of conspicuous some that expect, all should fall into the scope of protection of the invention.

Claims

1, a kind of method that tamed frequency modulation, TFM TFM signal is adjudicated, its step comprises:

(1) be excitation with current input binary system TFM signal, is Status Flag with all TFM signals of past in the accumulation of phase of sampling instant, is exciter response with excitation TFM signal and all TFM signals of past in the accumulation of phase of sampling instant, constructs the restriction relation state diagram of TFM signal;

2, the method that tamed frequency modulation, TFM TFM signal is adjudicated as claimed in claim 1, it is characterized in that: the restriction relation state diagram of TFM signal comprises state A and state B, signal is N*pi/2 in the phase place contribution of sampling instant among the state A; State B to the contribution of sampling instant phase place be+3pi/8 or-3pi/8, depend on the symbol of state B signal; Excitation to the contribution of sampling instant phase place be+pi/8 or-pi/8, depend on the symbol of pumping signal.

3, the method that tamed frequency modulation, TFM TFM signal is adjudicated as claimed in claim 2 is characterized in that: state A is divided into odd even clap handles, state A initial value is 0, then odd number clap state A be pi/2 or-pi/2, clapping state A at even number is 0 or pi.

4, as claim 1, the 2 or 3 described methods that tamed frequency modulation, TFM TFM signal is adjudicated, it is characterized in that: adopt the viterbi decoder of the code encoding/decoding mode structure of analogy convolution code at the TFM signal.

5, the method that tamed frequency modulation, TFM TFM signal is adjudicated as claimed in claim 4 is characterized in that: the tolerance of viterbi decoder adopts the input phase and the correlation of accurate phase place to represent.