JPH03151725A - Training signal detector - Google Patents

Abstract

PURPOSE:To surely decide a MODEM adjustment start timing without making the hardware of the MODEM complicate by detecting a prescribed repetitive patterns segment based on the quantity of extraction of a baud timing outputted from a timing extraction section. CONSTITUTION:A timing extraction section 30 acts like a timing extraction section for a reception side MODEM and is shared for a part of a timing extraction control section for various processing synchronously with a reception signal. A counter 20 is counted up or reset with a control signal from a comparator and when samples of predetermined number or above reach consecutively a value above the threshold level, a segment detection signal is outputted to the main control section of a succeeding MODEM to start the equalizer adjustment processing. The extraction quantity in the baud timing component is made largest in the repetitive pattern segments for the entire period of turn-on sequence. Thus, the prescribed repetitive patterns segment is detected base on the extraction quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a training signal detection device, and particularly to a training signal detection device for a receiving modem that detects a repetitive pattern segment consisting of repetitions of a plurality of signals in a training sequence transmitted from a transmitting modem. The present invention relates to a training signal detection device.

[Prior art] Conventionally, CCITT has been used in facsimile machines, etc.
Recommendation V, 27ter j: Comply with (-dem jJ and v
, 29 is used.

In the V,27ter modem and the V,29 modem, after the transmitting and receiving modems are connected via a communication line.

The transmitting modem sends out a predetermined training signal sequence (turn-on sequence) in order to initialize each signal processing section of the receiving modem.

For example, in V, 27ter modem, ■, 29 modem,
The training signal sequence is defined as shown in the table below.

Table 1 V, 27ter Training signal sequence SI Nishinpol interval (number of modulations) Table 2 V
, 29 Training Signal Sequence The receiving modem receives this training signal sequence and initializes the AGC1 automatic equalizer etc. which are the main constituent blocks of the receiving section.

In Table 1.2, V, 27ter segment 4, ■, 29
Segment 3 is for adjusting the tap coefficient at the initial setting stage so that the automatic equalizer provided in the receiving modem can realize the inverse characteristics of the communication line.

The initial setting operation of the receiving modem is to select V, 27ter, which is received earlier than the above-mentioned segment for adjustment.
Segment 3, ■, 29 Starts from the start of segment 2.

Figure 3 (A) shows the absolute phase and amplitude of the received signal using a polar coordinate system, V, 27ter 8-phase phase modulation 4800bp
3 shows the structure of the demodulated baseband signal in segment 3 at s (1600 baud). In the figure, Re indicates the real axis of the complex coordinate plane, and Im indicates the imaginary axis. In the figure, as shown by black circles, a series of signals whose phases are reversed by 180 degrees are received.

FIG. 3(B) shows the frequency components of the bus band received signal in this segment. As shown in the figure, the passband received signal at this time is ■.

27ter carrier frequency (1800Hz) ± 100 which is the Nyquist frequency (1600/2Hz)
It has a line spectrum at 0Hz and 2600Hz.

Also, Figure 3() is v in the same format as Figure 3(,A).
, 29 16-level quadrature amplitude modulation 9600bps (240
2 shows the structure of the demodulated baseband signal in segment 2 at 0 baud), and when the transmission rate is 9600 bps, an alternating pattern of points A and B in the figure is received.

Figure 3 (D) shows the frequency components of the passband received signal at this time, and shows the carrier frequency components of ■, 29 (17
00Hz), and 1700Hz±2400/2
Hz (7) It can be seen that 500 Hz and 2900 Hz are included as a line spectrum.

Next, the configuration of a conventional training signal detection device for a modem will be explained. FIG. 4 shows a conventional V.

This is a signal detection device for segment 3 in a 27ter4800bps training sequence.

The analog reception signal that reached the analog input terminal 40 is A
The signal is sampled by the /D converter 41 at a sampling frequency of 9600 Hz and converted into a discrete value signal.

This discrete value signal is branched into a first bus which is squared by a multiplier 41a, and a second bus which is input to bandpass filters 42 and 43 having center frequencies at 1 kHz and 2.6 kHz, respectively. In the second bus, the output of each bandpass filter is squared by multipliers 42a and 43a and sent to adder 4.
4 is added.

In this way, the output of the multiplier 41a on the first bus and the output of the adder 44 on the second bus are the power of all frequency components in the bus band of the received signal, respectively.
This is the power of a specific frequency component that the received signal has when it is within the segment that is the detection target.

Therefore, the output of both paths is the segment where the received signal is the detection target (here V,
It matches when it is within the 27ter segment 3), and it does not match at other times, so we need to take the difference between the outputs of both paths and judge the point at which the value matches 0 as the start point of the detection target segment. Bye.

In this conventional example, in order to detect the segment start point, a constant α (α<1.0) is applied to the output of the multiplier 41a.
The signal X multiplied by The configuration is such that the signal 2 is input to the determiner 47. Here, the reason why the integrator 46 performs addition and integration is to prevent false detection due to noise.

The determiner 47 generates a determination signal 48 indicating that a segment is detected when Z>0 and that a segment is not detected when 2≦0, thereby determining the time point at which the adjustment operation of the receiving modem starts.

[Problems to be Solved by the Invention] In the conventional example described above, segments are detected based on the polarity of the value of (power of a specific frequency component - power of all frequency components) of the received signal, so the received signal has no power. This method has the advantage that the target segment can be reliably detected even when additive white noise, which has a -like level over the entire frequency range, is added.

However, when colored noise whose power peak value is near the specific frequency component is added, or when a single tone signal near the specific frequency component is input, false segment detection tends to occur.

Furthermore, in the conventional example described above, it is necessary to separately provide a segment detection device completely independent of the other signal processing sections of the receiving modem, so there is a problem that the hardware size of the receiving modem increases.

An object of the present invention is to solve the above-mentioned problems and to make it possible to reliably determine the modem adjustment start timing without complicating the modem hardware.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a method for a receiving modem to detect a repetitive pattern segment consisting of repetition of a plurality of signals in a training sequence transmitted from a transmitting modem. In the training signal detection device, a timing extraction unit that generates a plurality of timing phase error signals having amplitude values proportional to sampling timing phase errors between the transmitter and receiver and mutually orthogonal phases from the demodulated baseband signal of the received signal; addition means for adding the absolute values of the plurality of timing phase error signals;
a comparison means for comparing the output signal of the adder with a predetermined threshold; and a period in which the absolute value of the timing phase error signal exceeds the threshold continues for a period longer than the predetermined period according to the output of the comparison means; A configuration is adopted in which a determination means is provided for outputting a detection signal indicating detection of a desired repetitive pattern segment when the repeated pattern segment is detected.

[Function] In the above configuration, the repetitive pattern segment for the purpose of detection includes a richer number of po timings than the isometric adjustment pattern, user data, etc. of the subsequent segment. The length of the period in which the sum of the absolute values of the plurality of timing phase error signals output from the timing extraction section exceeds a predetermined threshold value, that is, the amount of extracted baud timing component, is determined by repeating the above repeating pattern during the entire period of the turn-on sequence. Since it is the largest in the segment, the desired repeating pattern segment can be detected based on this extracted amount.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 is a block diagram showing the configuration of a training signal detection device according to the present invention. The illustrated circuit is used in the receiving modem of a facsimile machine, and detects the start timing of V,27er segment 3 to V,29 segment 2, which corresponds to the starting point of training of the receiving modem. It is something.

In Fig. 1, the symbol IO is an input terminal, and the symbol 11 is an A/D
Converter, reference numeral 12 is a demodulator that demodulates the passband reception signal and converts it into a baseband signal, and reference numeral 13 is a baud rate frequency fb/2 (Hz), where fb (Hz) is the baud rate frequency.
Filter the demodulated baseband seven signals with a narrowband bandpass filter having a center frequency at .

The signal after the above filtering has a baud rate period of Tb
(=1/f:b), the sample value is delayed by the delay device 14a which performs a delay process of Tb/2 time, and the multiplier 15a multiplies the current sample value by the sample value delayed by Tb/2. It will be done. The timing phase error signal a obtained as a result is the timing phase error Δφ(r
ad) has an amplitude value proportional to sin (Δφ).

On the other hand, the signal after −F filtering is still Tb/
After being delayed by a delay device 14b that performs a two-hour delay process, the signal is squared by a multiplier 15b, and the difference between the signal and the same signal which is squared by a multiplier 15c is determined by an adder 16. The resulting timing phase error signal S has an amplitude value proportional to CO8(Δφ) with respect to the timing phase error Δφ. In other words, (Δφ) (Δφ) This is a set of timing extraction signals having amplitude values proportional to the timing phase error and orthogonal to each other.

The absolute values of both signals a and b are taken by full-wave rectifiers 17a and 17b, respectively, and then added by an adder 18, and the result of this addition is provided to a comparator 19.

In this way, the signal whose magnitude is compared with the threshold value given in advance in the comparator 19 is 1si
Since the signal corresponds to n(Δψ)l+1cos(Δφ)1, even if the timing phase error Δφ can take any value, comparison with a fixed threshold value is possible.

Comparison with the threshold value may be performed using only the timing extraction signal a or b, but in this case, 1 sin (Δφ)1 is determined by the value of the timing phase error Δφ.
(or Icos(Δφ)1) is large (varies), so there is a problem that it is difficult to determine the threshold value of the comparator 19 to be a constant value.

A timing extraction circuit 30 indicated by a dotted line in the figure functions as a timing extraction section of the receiving modem, and is also used as a part of the timing extraction/control section in order to perform various processes in synchronization with the received signal.

The comparator 19 is l5in(Δφ)l+1cos(Δφ)
A count up signal is output for a sample value where 1 is greater than or equal to the threshold value, and a counter reset signal is output for a sample value that is less than the threshold value.

The counter 20 performs a count-up/reset operation based on the control signal from the comparator, and when a predetermined number or more of sample values consecutively exceed the threshold value, the timing phase error signal is detected. a,
When the period in which the sum of the absolute values of b exceeds the threshold value of the comparator 18 continues for a longer period than a predetermined period, a segment detection signal is output to the main control section of the subsequent modem, and the isolator adjustment process is started. .

FIG. 2 shows computer simulation results according to this example. Figure 2 (A) is V, 27ter 4800bps
Training sequence, (B) is V, 29 96
1s extracted from 00bps training sequence
in(Δφ)1 (solid line part: corresponds to signal a in Figure 1) 8
and Icos(Δφ)1 (dotted line portion: corresponds to the signal shown in FIG. 1).

As is clear from Fig. 2, the number of samples in which 1 sin (Δφ) l + 1 cos (Δ 3 4 φ) 1 exceeds the threshold during the repetitive pattern segment that is the detection target and when receiving other data patterns is , even in the presence of any timing phase error Δφ, there is a clear difference, which allows us to reliably capture repeating pattern segments.

Segment 3 of V, 27 ter/b i s, which should be detected as the modem training start timing, is 18
Since v, 29 segment 2 is composed of a repeating pattern of A and B signals from alternating signals whose phases are inverted by 0°, it has a richer baud timing compared to the equalizer adjustment pattern and user data of subsequent segments. Contains.

Therefore, the length of the period during which the sum of the absolute values of the timing phase error signals a and b having orthogonal phases obtained by the timing extraction section 30 of FIG. The amount is highest during the above repeating pattern segment during the entire turn-on sequence, and relatively small at other times;
The conventional configuration has the advantage that highly accurate segment detection can be performed even when colored noise or specific single tone signals that cause false detection are included.

Further, according to the above embodiment, the sum of the absolute values of two timing phase error signals having orthogonal phases is compared with a predetermined threshold, and a desired signal segment is detected according to the duration of a certain comparison result. Therefore, if there is any initial timing phase error associated with the sampling clock phase between the transmitting and receiving modems, or if there is a transmission deterioration factor (timing frequency error) that causes the same timing phase error to fluctuate over time. Also, by using a fixed threshold, it is possible to stably determine whether a target segment is detected or not.

Furthermore, the timing extraction unit 20 which is the main part of this configuration
Since the timing extraction and control section of the receiving modem can be shared with the receiving modem, the hardware scale can be reduced compared to the conventional configuration that requires independent hardware.

In the above embodiments, the timing extractor is composed of a narrowband bandpass filter and a delay device, but it goes without saying that a different circuit configuration may be used as long as it is a circuit that forms a phase error signal.

[Effects of the Invention] As is clear from the above, according to the present invention, the training signal detection of the receiving modem detects repetitions of a plurality of signals or a repetitive pattern segment consisting of a training sequence transmitted from the transmitting modem. The apparatus includes: a timing extraction unit that generates a plurality of timing phase error signals having an amplitude value proportional to a sampling timing phase error between the transmitter and receiver and mutually orthogonal phases from a demodulated baseband signal of a received signal; addition means for adding the absolute values of the phase error signals; comparison means for comparing the output signal of the adder with a predetermined threshold value; The interrogator is equipped with a determining means for outputting a detection signal indicating detection of a desired repetitive pattern segment when the period in which the threshold value is exceeded continues longer than a predetermined period.

Here, the repetitive pattern segment for the purpose of detection contains abundant baud timing compared to the equalizer adjustment pattern, user data, etc. of the subsequent segment. According to the above configuration, the length of the period in which the sum of the absolute values of a plurality of timing phase error signals having orthogonal phases exceeds a predetermined threshold value, that is, the amount of extracted baud timing component, is determined during the entire period of the turn-on sequence. Since the above-mentioned repeating pattern segment has the largest amount, the desired repeating pattern segment can be detected based on this extracted amount.

In addition, the extraction amount is relatively small in periods other than repeating pattern segments, and highly accurate segment detection can be performed even when colored noise or specific single tone signals that would cause false detection with conventional configurations are included. In addition, when there is an arbitrary initial timing phase error associated with the sampling clock phase between the transmitting and receiving modems, and when there are transmission deterioration factors that cause the same timing phase error to fluctuate over time, fixed Using a predetermined threshold, it is possible to determine whether a stable target segment has been detected or not. Furthermore, the timing extractor that generates a timing phase error signal is a synchronizer that generates a synchronization signal necessary within the modem. Since it can be used as a control means, it has excellent advantages such as simplifying the hardware configuration of the modem.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a training signal detection device according to the present invention, FIGS. 2(A) and (B) are waveform diagrams showing the operation of the device in FIG. 1, and FIGS. (D
) is an explanatory diagram showing the operation of the conventional device, and FIG. 4 is a block diagram showing the configuration of the conventional device. 11...A/D converter 12...Demodulator 13...Band pass filter 14a, l4b...Delay unit 15a=15c=-Multiplier 17a, 17b...Full wave rectifier 18... - Adder 19...Comparator 20...-Counter 9 b...Timing phase error signal 0

Claims (1)

[Claims] 1) In a training signal detection device for a receiving modem that detects a repetitive pattern segment consisting of repetitions of a plurality of signals in a training sequence transmitted from a transmitting modem, the transmission/reception is performed from a demodulated baseband signal of a received signal. a timing extractor that generates a plurality of timing phase error signals having amplitude values proportional to sampling timing phase errors between machines and mutually orthogonal phases; and an adding means that adds absolute values of the plurality of timing phase error signals. , a comparison means for comparing the output signal of the adder with a predetermined threshold; and a period in which the absolute value of the timing phase error signal exceeds the threshold is longer than the predetermined period according to the output of the comparison means. 1. A training signal detecting device comprising: a determining means for outputting a detection signal indicating detection of a desired repetitive pattern segment when consecutive pattern segments are detected.