JPH0659788A - Portable computer - Google Patents

Abstract

PURPOSE:To provide a portable computer which can achieve the transmission speed of the same level as a case by a MODEM or an NCU even at a place where there is no modular jack in the case that communication is executed through a public line. CONSTITUTION:The communication is executed by sound-coupling this portable computer with the handset of a telephone set by an acoustic coupler 109, and adaptive noise canceling processing at the time of sound coupling is executed by an adaptive equalizer 115.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable computer, and more particularly to a portable computer having a communication interface with a public line.

[0002]

2. Description of the Related Art Conventionally, this type of portable computer has a modem and an NCU (Network Control Unit) built-in or externally attached, is connected to a public line through a modular jack, and is connected to another computer. I was communicating.

In a place where the modular jack cannot be used, for example, in a public telephone box, an acoustic coupler is used for communication via a handset.

[0004]

However, in the communication technology using the conventional portable computer as described above, when connecting to the public line through the modular jack by the modem and the NCU, the equipment provided with the modular jack is limited. Therefore, it has a drawback that the range of use as a portable computer is narrowed.

Further, when the handset is connected via the acoustic coupler, although the above-mentioned drawbacks are not present, the frequency characteristic is deteriorated due to the acoustic coupling characteristic between the acoustic coupler and the handset, or depending on the surrounding conditions. Since the coupling characteristics change, the communication speed needs to be set significantly lower than that in the above case. Therefore, there is a drawback that the communication time becomes long and the communication cost becomes high.

The present invention has been made to solve the above-mentioned problems, and provides a portable computer capable of achieving a communication speed comparable to that obtained by a modem and NCU even in a place without a modular jack. The purpose is to do.

[0007]

To achieve this object, a portable computer of the present invention comprises an acoustic coupler for acoustically coupling with a handset of a telephone, and an adaptive noise when the acoustic coupler acoustically couples with the handset. It is equipped with an adaptive equalizer that performs canceling processing.

[0008]

In the portable computer of the present invention having the above-mentioned structure, the acoustic coupler acoustically couples with the handset of the telephone for communication, and the adaptive equalizer performs adaptive noise canceling processing at the acoustic coupling.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a portable workstation as an embodiment of the portable computer of the present invention. In this embodiment, the acoustic coupler is composed of the acoustic coupler 25, and the adaptive equalizer is composed of the DSP (digital signal processor) 11.

The CPU 1, the FPU (floating point arithmetic unit) 3 and the cache memory 5 operate at high speed, and the CPU 1 operates according to the instructions and data stored in the cache memory 5.
And FPU3 execute the program. If the instruction and data are not in the cache memory 5, D
Access from the RAM 31. On the main bus, a memory and I / O that are slower than the cache memory 5 are connected. A boot program is mainly stored in the ROM 9.

Devices such as a hard disk and a network that perform block transfer are connected to the main bus via the DMA controller 33. Cereal,
A device such as a keyboard that transfers data in byte units is connected to the main bus via the serial controller 37. The display 43 is connected to the main bus via the display controller 41.

The DSP 11 is an A / D (A / D converter)
A signal processing algorithm is executed on the basis of an input signal from 13 and the signal is output to a D / A (D / A converter) 15. Also, connected to the main bus, CPU
It exchanges data with 1. The NCU 23 is used when communication is performed by connecting to a public line through a modular jack. In addition, the acoustic coupler 25 is used when communication is performed by connecting to a public line through a handset. The MPX (multiplexer) 17 includes an analog input port 21, an NCU 23, and an acoustic coupler 25.
Select the analog input signal from the
It is to be sent to D13. The MPX 19 sends the analog output signal from the D / A 15 to the analog output port 27,
If necessary, the NCU 23 and the acoustic coupler 25 are selected and output.

FIG. 3 is a block diagram of a transmission system when the portable computer of the present invention is connected to a public line. In FIG. 3, the inside of the broken line is the portion related to the portable computer of the present invention, and each processing is the DSP of FIG.
It is realized by digital signal processing by 11.

A transmitting terminal 101 and a receiving terminal 103, which are communication partners, are connected to a transmission line 105. Here, the transmission line 105 is an abstraction of a public line network such as a line cable and an exchange. In the transmission line 105,
There is linear distortion due to the frequency characteristics of the line cable and nonlinear distortion due to carrier phase fluctuation (jitter) and frequency offset due to the exchange. Furthermore, thermal noise, impulsive noise from the surrounding environment, crosstalk from other lines, etc. add as transmission line noise. Handset 1
When 07 and the acoustic coupler 109 are acoustically coupled, in addition to distortion due to the frequency characteristic of the acoustic coupler 109, coupler noise due to the environment of the coupling point is added. Therefore, the quality of the transmission system deteriorates as compared with the normal case (when connecting directly to the line using the NCU without using the acoustic coupler). Therefore, for example, when transmitting in a 4-phase PSK (phase modulation) system, the adaptive equalization process that is usually used in a 16-value QAM (quadrature amplitude modulation) system or the like is performed to follow up even if the characteristics of the transmission system change You need to compensate.

Here, an example of the operation of the present invention will be described by taking the case of transmitting by the 4-phase PSK system as an example. The 4-phase PSK modulation waveform is

[0017]

[Equation 1]

It is represented by Here, fc is a carrier frequency and a is an amplitude, which is a constant value (it changes in QAM). The modulation is performed by changing θi. 4-phase P
In the case of SK, θi takes values of 0, π / 2, π, 3 / 2π. In FIG. 3, the transmission data string is grouped in 2-bit units in the code conversion unit 125. The signal point generator 127 sets "00" for the grouped data.
Is θi = 0, “01” is θi = π / 2, and “1” is
Θi = π is assigned to 0 ”and θi = 3 / 2π is assigned to“ 11 ”, and two independent time series xi and yi in the equation 1 are generated.

Now, xi and yi take the values of + a, 0, and -a, but when viewed as a time series, they change in a square wave shape, so that they cannot be accurately transmitted as they are. Therefore, the band is limited through the roll-off filter 129. Here, the roll-off filter 129 has a frequency characteristic that does not cause code interference between adjacent symbols, and its impulse response is h (t) and the symbol interval is T,

[0020]

[Equation 2]

Band-limited time series x'i and y'i are obtained by a 2N + 1-tap FIR (finite impulse response) type digital filter (convolution operation). The modulator 131 multiplies x′i and y′i by orthogonal carriers cos (2πfct) and sin (2πfct), respectively, and performs frequency conversion from the baseband to the passband. The fixed equalizer 133 corrects in anticipation of deterioration of the frequency characteristic of the transmission system due to a cable or the like expected in advance, but may be omitted when adaptive equalization is performed. As described above, the transmission data is modulated and sent to the transmission line via the acoustic coupler 109.

At the time of reception, the processing is performed by tracing the reverse of that at the time of transmission. The demodulation unit 111 receives the passband received signal r (t) input from the transmission line via the acoustic coupler 109 by the orthogonal carriers cos (2πfct), sin.
By multiplying by (2πfct), the frequency is converted into two sets of baseband signals of x and y. Further, by the roll-off filter 113, the band-limited baseband signal x ′,
It becomes y '. Due to the linear distortion of the transmission line, not only in-phase distortions of x ′ and y ′ but also quadrature distortions that interfere with each other occur.

Therefore, the adaptive equalizer 115 needs to handle it as a two-dimensional (complex) signal. I.e.

[0024]

[Equation 3]

It is considered that a complex number signal as shown by is input to the adaptive equalizer 115. Note that here, in order to emphasize that the time series is a sample sequence that is discrete in time, a variable n is used instead of t. In Figure 4,
3 shows a block diagram of adaptive equalizer 115. FIG. In FIG.
The signal paths are all complex numbers. For the input signal w (n), the equalized output signal v (n) is

[0026]

[Equation 4]

It is obtained by an FIR type complex digital filter (convolution operation) of M taps as shown in. Here, the tap coefficients h0 to hM-1 are variable, and the error signal e (n) between the reference signal d (n) and the output signal v (n) is changed.
From

[0028]

[Equation 5]

It is calculated by an adaptive algorithm as shown in. μ is a step size parameter, and is determined from the balance between the speed of tap coefficient convergence and stability. Also, * represents a complex conjugate. The reference signal d (n) uses a predetermined training signal in the initial state, and uses the determination output from the signal point determination unit 121 in the steady state. Number 5
Is an adaptive algorithm called LMS (Least Mean Square) method, which is an input signal w (n−
k) and the correlation value of the error signal e (n) are calculated, and the correlation coefficient is used as a correction term to correct the tap coefficient in the direction in which the square of the error becomes smaller.

FIG. 5 shows that the frequency characteristic of the transmission system is equalized by the adaptive equalizer 115. Figure 5 (a) shows
It is the frequency characteristic of the passband signal of 4-phase PSK of carrier frequency fc when there is no distortion in the transmission system. Figure 5
(B) is the frequency characteristic of distortion of the transmission system. FIG. 5C shows frequency characteristics when the signal of FIG. 5A is affected by the distortion of the transmission system. Adaptive equalizer 11
5 continues to update the tap coefficient by the adaptive algorithm, and when it reaches a steady state, it converges to the inverse characteristic of the distortion of the transmission system as shown in FIG. As a result, FIG. 5 (c)
The signal of can approach the characteristics of FIG. 5 (a).

As described above, the carrier frequencies on the transmitting side and the receiving side do not always match and there is also jitter, so that synchronous detection for synchronizing the carriers on the transmitting side and the receiving side is required. However, since the delay due to the adaptive equalizer is large, it becomes unstable when the carrier frequency is changed in the demodulation unit 111. Therefore, in FIG. 3, the carrier frequency of the demodulation unit 111 is fixed, and the rotation on the complex plane from the true value of the output signal v (n) of the equalizer caused by carrier frequency offset and jitter is corrected. This realizes synchronous detection. When the correction angle is Δθ with respect to v (n), the signal point rotation unit 117

[0032]

[Equation 6]

The processing indicated by is performed. Signal point determination unit 12
1, the output signal w ′ (n) after rotation correction is
Of the four phases of 0, π / 2, π and 3 / 2π, the closest one is determined and output as d (n). Signal point determination unit 12
1, the carrier reproducing unit 119, and the signal point rotating unit 117 form a PLL (Phase Lock Loop). The carrier regenerator 119 performs a phase comparison between w ′ (n) and d (n) and also follows a frequency offset, so that the loop filter of the PLL is configured so that the steady phase deviation becomes zero.
Determine the rotation correction angle Δθ. The code conversion unit converts the 2-bit grouped data into a normal data string for w ′ (n), and makes it the received data.

As described above, in addition to the distortion caused by the transmission system, the dynamic distortion at the coupling point of the acoustic coupler 109 is also canceled by the adaptive equalization processing.

[0035]

As is apparent from the above description, the portable computer of the present invention has an acoustic coupler for acoustically coupling with a handset of a telephone, and an adaptive noise canceler when the acoustic coupler acoustically couples with the handset. By having an adaptive equalizer that performs ring processing,
Even where there is no modular jack, it is possible to achieve the same communication speed as that by the modem and NCU.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a portable computer of the present invention.

FIG. 2 is a block diagram showing an embodiment of a portable computer of the present invention.

FIG. 3 is a block diagram of a transmission system when the portable computer of the present invention is connected to a public line.

FIG. 4 is a block diagram of an adaptive equalizer used in the portable computer of the present invention.

FIG. 5 is a diagram showing frequency characteristics of a transmission system in an embodiment of the portable computer of the present invention.

[Explanation of symbols]

 109 acoustic coupler 115 adaptive equalizer

Claims (1)

[Claims] 1. A portable device comprising: an acoustic coupler for acoustically coupling with a handset of a telephone; and an adaptive equalizer for performing adaptive noise canceling processing when the acoustic coupler acoustically couples with the handset. Computer.