JPH01241249A - Training signal detection system - Google Patents

Abstract

PURPOSE:To simply and easily detect a training signal and its change by multi plying a demodulated base band signal and a signal of complex number conjuga tion being the result of delay so as to decide and detect its phase inversion. CONSTITUTION:When a deciding section 9 detects that a product between a base band signal demodulated by a demodulator 1 or a signal ai being result of carrier shift by a multiplier 4 as necessary and a complex conjugation signal of a signal ai-1 retarded by a delay element 6 exists in a prescribed discriminat ing face, it is decided to be a training signal such as relevant AA, AC or S signal. Moreover, when the signal ai is given to a phase inversion detection section 10 and the phase inversion is detected, it is detected that the signal is changed from AA into CC, from AC into CA and CA into AC, etc. Since the base band signal is used to detect the training signal and its change, the detection accuracy is improved.

Description

[Detailed Description of the Invention] [Summary] Regarding a training signal detection method for detecting a training signal, it is possible to detect a training signal such as an AA double signal AC signal or an S signal using a simple configuration from a baseband signal obtained by demodulating a received signal. , and a change from an AC signal to a CA multiplied signal, etc., and information on whether or not the received signal has been carrier-shifted with respect to the demodulated baseband signal, and the baseband signal or carrier-shifted signal. The configuration is configured to detect a training signal such as AA (, j signal, AC signal, S signal, etc.) based on the result of multiplication by the complex conjugate of the delayed signal. For signals carrier-shifted as necessary, phase inversion is detected to detect changes from AA times signal to CC signal, AC signal to CA times signal, CA times signal to AC signal, S signal to S signal, etc. Configure.

[Industrial application field]

The present invention relates to a training (epsilon detection method) for detecting a training signal.

[Problems to be solved by conventional technology and invention] CCI
In the TT protocol, when communicating with each other using a line connected between a calling mode modem and an answering mode modem, various training signals such as AA double signal AC signal, It is necessary to send out the S signal, receive it, and detect it. For example, after a calling modem sends an AA double signal to an answering modem, it is necessary to detect the AC signal that would be returned from the answering modem. Furthermore, the calling mode modem needs to detect the state in which the AC alternating signal sent from the answering modem changes to the CA alternating signal, and then transmitting the CC signal to the answering modem.

An object of the present invention is to detect training signals such as AA multiplied signals, AC signals, and S signals, and to detect changes from AC signals to CA multiplied signals, etc., using a simple configuration from a baseband signal obtained by demodulating a received signal. It is said that

[Means for solving problems]

Means for solving the problem will be explained with reference to FIG.

In FIG. 1, a demodulator 1 demodulates a received signal to generate a baseband signal.

The multiplier 4 carrier-shifts the baseband signal as necessary.

The delay element 6 delays the baseband signal or the carrier-shifted signal ai.

The multiplier 7 multiplies the baseband signal or carrier-shifted signal aI by a complex conjugate signal of the delayed signal ai-j.

The determination unit 9 determines whether the signal is an AA multiplied signal AC signal or a training signal such as an S signal, based on the result of multiplication by the multiplier 7 and the like.

The phase inversion detection unit IO detects that the phase is inverted.

[Effect]

As shown in FIG. When the determination unit 9 detects that the value obtained by multiplying the signal of the complex conjugate of i-1 exists within a predetermined determination plane (in the determination plane in FIG. 3),
It is determined that the signal is a training signal such as a corresponding AA signal, AC signal, or S signal.

Further, the baseband signal demodulated from the received signal by the demodulator 1 or the signal al carrier-shifted by the multiplier 4 as necessary is input to the phase inversion detection section 10, and when it is detected that the phase is inverted, , a change from the corresponding AA double signal to CC (No. 3, AC signal, CA double signal, CA double signal to AC signal, etc.) is detected.

Therefore, with a simple configuration from the baseband signal obtained by demodulating the received signal, it is possible to detect training signals such as AA multiplied signals, AC signals and S signals, and to detect changes from AC signals to CA multiplied signals, etc. .

〔Example〕

Next, the configuration and operation of one embodiment of the present invention will be explained in detail using FIGS. 1 to 6.

In FIG. 1, a demodulator 1 demodulates a received A3 signal, for example, a carrier signal (cos2πf,
, -5in2 πfc).

fe is a carrier frequency, for example 1800H2.

A roll-off filter (ROF) 2 blocks harmonic components and extracts a baseband signal.

The AGC (self-OJ gain control (In circuit)) 3 controls the gain so that the amplitude of the baseband signal extracted by the roll-off filter 2 is constant. A baseband signal is obtained.

The multiplier 4 receives a baseband signal, for example, AC (, 8, 1, CAR,
Al1. Multiply by Y・-5IN2 πf czt, f
A carrier shift corresponding to c2=1200H2 is performed. There is no need to carrier shift for other AA multiplied signal S (such as No. 3 baseband signal), so
Multiply by CAR,X=1 and CAR,Y=0. The signal ``as a result of multiplication by the multiplier 4'' becomes as shown in ``■'' in FIG.

L P F (115 is for cutting off the high frequency component of the signal multiplied by the multiplier 4 and extracting the desired DC component. The signal output from L P F (115 is shown in FIG. As shown in the figure, there is only a DC component.

The delay element 6 generates a signal ai-5 by delaying the signal al.

The multiplier 7 multiplies the signal a by the complex conjugate of the delayed signal ai-1.

The LPF (218) cuts off high frequency components of the multiplication results and extracts low frequency components.

The determining unit 9 determines which training signal it is. For example, it is determined whether the signal is an AA signal (a) in Fig. 2, an AC signal (b) in Fig. 2, or an S signal in Fig. 2 (c).
L P F (When the signal output from 218 exists within the diagonal line in Fig. 3, the corresponding AA multiplied signal AC signal,
Alternatively, it is determined to be an S signal. The AC signal is carrier-shifted and outputted from the LPF (218) (determined when No. 3 exists within the diagonal line in Figure 3. AA multiplied signal S
The signal is the one detected by the AA double signal response mode modem without carrier shift and as is clear from the training signal example in Figure 6, and the S signal is detected by the calling mode modem. Therefore, we can distinguish between them.

The phase inversion detection unit 10 detects that the phase of the baseband signal or carrier-shifted signal output from the LPF fil 5 is inverted, as shown in FIG. Changes from the AC signal to the CC signal, from the AC signal to the CA flaw signal, from the CA flaw signal to the AC signal, from the S signal to the S signal, etc. are detected. This is achieved by combining the multipliers 11-1.
oop) to detect that the phase of the baseband signal or carrier-shifted signal is reversed (described later with reference to FIG. 5).

Next, the operation of detecting training signals such as the AA multiplied signal AC signal and the S signal will be explained.

In FIG. 2, when a signal on the line is received and demodulated to extract a baseband signal, the result is as shown in FIG. For the AC signal in Figure 2 (b) where the baseband signal in Figure 2 (■) does not contain a DC component, it is multiplied by a subcarrier and carrier assisted as shown in Figure 2 (b) ■. After that, the high frequency component is cut off and only the DC component is taken out as shown in FIG. Other Figure 2 (a) AA
Since the double signal and the S signal in FIG. 2(c) have a DC component in the baseband signal, only the DC component is shifted as shown in the figure (■) without carrier shifting. The DC component signal a of these O is multiplied by the complex conjugate of the delayed signal a4.1.

For example, if the signal is a8·exp (jθ), the complex conjugate of the signal a, −1·exp(jθ) delayed by one is e
xp(-jθ). Therefore, the product of both is exp(j'θ)xexp(-jθ)81.

If the product of these two exists within the shaded area in FIG. 3, it is determined that the AA multiplied signal is either the AC signal or the S signal. Note that the shaded area in FIG. 3 indicates the range where the conditions shown in the figure are satisfied.

Next, the operation of detecting changes from the AA multiplied signal to the CC signal, from the AC signal to the CA flaw signal, from the CA flaw signal to the AC signal, and from the S signal to the S signal will be described.

In FIG. 5, symbol (2) in the figure causes a PLL operation to detect the AA-multiple signal AC signal and S signal.

This is done by phase inversion in Figure 1 so that only the real component of the original signal to be detected is the change in the back of the AA multiplied signal, AC signal, S signal, as shown in Figure 4 (■). This means that the detection unit 10 is operated.

In the figure, ■ indicates a reversal of REAL from 10 to -. This is indicated by ■ in the figure and l'? as shown in ■ in Figure 4. From the state in which the positive EAL component was detected, the phase of the signal input to the phase inversion detection unit 10 is inverted by 180 degrees, and as shown in FIG.
This means detecting a state in which the REAL component changes from positive to negative as shown in FIG.

■ in the figure returns the output to (A, 0). This means that the output of the REAL component of the phase reversal detecting section 10 in FIG. 1, which was inverted to negative at ■ in the figure, is returned to positive. To return the value to positive, the phase inverter 14 in FIG. 1 changes the value input to the multiplier 11-2 from "1" to "-1" or from "-1" to "
1”.

Through the above procedure, the change in the training signal from the AA multiplied signal to the CC signal, etc. is attenuated by one.

〔Effect of the invention〕

As explained above, according to the present invention, any training signal is obtained by multiplying a base buff 1 signal obtained by demodulating a received signal or a signal obtained by carrier shifting a baseband signal by a complex conjugate signal obtained by delaying this signal. Since the system uses a configuration that detects phase reversal and detects switching of the training signal, a WJ simple configuration and fffliR processing can detect the AA double signal AC
It is possible to detect a training signal such as a signal or an S signal, and also to detect a change in the training signal from an AC signal to a CA multiplied signal, etc. Furthermore, since the training signal and its changes are detected using the baseband signal, the detection accuracy is high.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of one embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the present invention, Fig. 3 is an example of a judgment plane, Fig. 4 is an example of a vector plane, and Fig. 5 is a flowchart for detecting changes in training signals. , FIG. 6 shows an example of a training signal between modems. In the figure, 1 is a demodulator, 4.7 is a multiplier, 6 is a delay element, and 9
1 represents a determination section, and 10 represents a phase reversal detection section. AA name ■ AC number ■ S name number ■ Figure full fixed plane example spring 3 figure rich vector V surface 4 clear 4 figure

Claims (2)

[Claims] (1) In a training signal detection method that detects a training signal, information on whether or not the received signal is carrier-shifted with respect to the demodulated baseband signal, and whether the baseband signal or carrier-shifted signal and delayed signal are Based on the result of multiplication with the complex conjugate, the AA signal, AC signal,
A training signal detection method characterized by being configured to detect a training signal such as an S signal. (2) In the training signal detection method that detects training signals, phase inversion is detected for the baseband signal obtained by demodulating the received signal or a signal carrier-shifted as necessary, and the signal is converted from the AA signal to the CC signal or from the AC signal. CA signal, CA
A training signal detection method characterized by being configured to detect changes from a signal to an AC signal, from an S signal to an @S@ signal, etc.