JPS62157450A - Telephone set - Google Patents

Abstract

PURPOSE:To realize the full duplex by providing a leakage signal erasure means erasing a leakage signal from a reception system to a transmission system so as to apply transmission/reception in parallel simultaneously. CONSTITUTION:The leakage signal erasure circuit 30 is provided between digital signal systems of a transmission system 4 and a reception system 10 to erase the leakage signal component of a leakage signal path E1 from a digitized transmission signal. A pseudo leakage signal generating circuit 38 decides the filter coefficient of a transversal filter 40 according to a prescribed algorithm, generates a pseudo leakage signal Se equivalent to the leakage signal Se, which is subtracted from the digitized sending signal (St+Se). Thus, the effect of the leakage signal from the leakage signal path E1 is avoided, resulting that the full duplexing where the transmission/reception is applied in parallel simultaneously is attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a telephone device such as a speakerphone with a desktop handset attached to it for transmitting and receiving calls, and particularly to a telephone device for transmitting and receiving calls, and in particular for erasing leakage signals between transmitting and receiving systems. Regarding.

[Conventional technology]

In a telephone device, such as a speakerphone, in which a handset is installed on a table to make a call, as shown in FIG. A received signal from the exchange that is sent out and received via the telephone line 8 is applied from the hybrid circuit 6 to the receiving system 10, and is reproduced by the speaker 12 as received audio. In this case, the transmitted signal from the microphone 2 is amplified by the amplifier 14 and applied to the hybrid circuit 6, and the received signal to be reproduced is amplified by the amplifier 16 and applied to the speaker power 12.

A call switching circuit 18 is installed between the transmitting system 4 and the receiving system 10 to switch the direction of the call depending on the level of the transmitting signal and the receiving signal. Call switching circuit 1
8 is an electronic volume circuit 20 for selectively blocking the transmission signal of the transmission system 4 and the reception signal of the reception system 10;
．． 22, a comparator 24 for comparing the signal level between the transmitting system 4 and the receiving system 10 is installed, and this comparator 2
The volume circuits 20 and 22 are controlled by the output of 4 to switch the communication direction. Therefore, in such a telephone device, half-duplex call switching is realized by the switching operation of the call switching circuit 18.

By the way, in such a telephone device, in the handset of the speakerphone, the microphone 2 and the speaker 12 are installed adjacent to each other on the table, so in order to prevent the reproduced sound from the speaker 12 from going around to the microphone 2, for example, As shown in FIG. 7, mounting surfaces 26a and 26b are set on the front side of the transmitter/receiver case 26 to form a certain angle so as to block mutual influence, and the speaker 12 is mounted on one mounting surface 26a, and the speaker 12 is mounted on the other mounting surface 26a. By attaching the microphone 2 to the mounting surface 26b of the
Measures are being taken to prevent this from happening.

[Problem that the invention seeks to solve]

In telephone equipment that switches transmission and reception by comparing the signal levels between the transmission and reception systems, it takes time to detect the signals for the level comparison, so when switching, the beginning of the transmission and reception signal may be cut off, resulting in unclear calls. There is a drawback. In particular, depending on the environment such as the room in which the telephone device is placed, the sound reproduced by the speaker 12 is delayed from the leakage signal path E+ and enters the microphone 2, as shown in FIG. Since leakage signals are also subject to level comparison, the break between reception and transmission becomes unclear due to the leakage signals, and simple level comparison is often impossible.

Furthermore, a leakage signal path E2 through which a part of the transmission signal goes around to the reception system 10 is formed between the transmission system 4 and the reception system 10 via a line that is a circuit on the line sending side and the hybrid circuit 6.

Therefore, in such a telephone device, there is a leakage signal path E1 between the speaker 12 and the microphone 2, and a leakage signal path E2 via the hybrid circuit 6, etc., but the call switching of such a telephone device At this time, the most disturbing of the leakage components is the leakage signal generated via the leakage signal path E1. In particular, since this leakage signal path El changes significantly depending on the environment in which the speakerphone is placed, its influence cannot be removed even when comparing levels for call switching in a telephone device assuming half duplex.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a telephone device that avoids the influence of leakage signals through such leakage signal paths.

[Means for solving problems]

As shown in FIG. 1, the telephone device of the present invention has a transmission system between a transmission system 4 that sends transmission signals to a telephone line and a reception system 1o that regenerates reception signals from the exchange side. A leakage signal erasing means (the leakage signal erasing circuit 30 of the embodiment) is installed for erasing the leakage signal to.

[For production]

The telephone device of the present invention eliminates leakage signals in the leakage signal path between the transmission system and the reception system, and avoids the influence of the leakage signals.

In the telephone device of the present invention, for example, the leakage signal canceling means is configured using a filter that obtains a pseudo leakage signal from the reception signal that is equivalent to a leakage signal of the reproduced voice of the reception signal to the microphone, and the filter If the leakage signal from the reception system to the transmission system is canceled by the pseudo leakage signal obtained in , the leakage signal of the reproduced audio from the reception system to the transmission system is canceled by the equivalent pseudo leakage signal obtained by the filter. can. That is, the leakage signal path E
1 is formed by a filter equivalent to it, and after determining the coefficients of the filter at the time of making a call, the filter path in the telephone is used to cancel the leakage signal from the leakage signal path E1 at the time of sending a call. can be achieved.

Further, in the telephone device of the present invention, the coefficient of the filter is set, for example, at the time of reception, according to the difference component between the calling signal and the leakage signal due to the looping around to the microphone, and the coefficient is set depending on the surrounding environment for each call. If you change it accordingly,
When a telephone is called, leakage signals from a receiving system adapted to the surrounding environment to a transmitting system of reproduced audio can be eliminated.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

(First example) FIG. 1 shows a first embodiment of the telephone device of the present invention.

In FIG. 1, the transmission signal obtained by the transmission system 4 on the output side of the amplifier 14 is converted into a digital signal by an analog-to-digital converter (A/D) 28, and the digitized transmission signal is converted to a leakage signal canceling circuit 30. is added to cancel the leakage signal from the leakage signal path El. The digitized transmission signal from which leakage signal components have been removed is applied to a digital-to-analog converter (D/A) 32 to be converted back into an analog signal, and then applied to a hybrid circuit 6 and sent out to a telephone line 8. Ru.

Further, the reception signal from the exchange received via the telephone line 8 is transmitted to the reception system 10 via the hybrid circuit 6.
It is converted into a digital signal by the D34 and applied to the leakage signal canceling circuit 30, and is also applied to the D/A 36 where it is converted back into an analog signal, which is then passed through the amplifier 16 and reproduced from the speaker 12 as received audio.

The leakage signal canceling circuit 30 includes a transmission system 4 and a reception system 1.
It is installed between the 0 digital signal systems and eliminates the leakage signal component of the leakage signal path E1 from the digitized transmission signal. In this embodiment, the leakage signal canceling circuit 30 includes a pseudo leakage signal generating circuit 38 as a pseudo leakage signal generating means for generating a pseudo leakage signal equivalent to the leakage signal obtained on the leakage signal path E1. This pseudo leakage signal generation circuit 38 is equipped with a transversal filter 40 as an adaptive filter in which an arbitrary frequency band is set by setting coefficients, and the filter coefficients of this transversal filter 40 are set by a coefficient determination circuit 42. Create a pseudo-leakage signal necessary to cancel the signal. The coefficient determining circuit 42 receives a detection signal from a calling signal detection circuit 44 that detects a calling signal sent from the telephone line 8;
Based on the digitized transmission signal from the transmission system 4 and the digitized reception signal from the reception system 10, the transversal filter coefficients are determined according to a predetermined algorithm when the call is in a calling state, and when the call is finished, the leakage signal and the The filter coefficients required to generate an equivalent pseudo leakage signal are calculated, and the calculated coefficients are set in the transversal filter 40.

The pseudo leakage signal obtained by the transversal filter 40 is transmitted to the A/D 28 and D/A 32 of the transmission system 4.
The signal is added to a subtracter 46 installed between the digital signal lines of the digitized transmission signal and subtracted from the digitized transmission signal, thereby canceling the leakage signal contained in the digitization transmission signal by canceling it with the pseudo leakage signal.

In such a telephone device, if the genuine transmission signal added from the microphone 2 by the voice of the caller is SL, and the leakage signal entering the microphone 2 from the speaker 12 via the leakage signal path EI is 80, then the signal output from the microphone 2 is 80. The transmitted signal is a sum signal (st+S,) of the genuine transmitted signal St and the leakage signal s0. After this sending signal (S, +S,) is amplified by the amplifier 14, the A/D
It is converted into a digital signal at 28 and applied to a subtracter 46. Here, when the calling signal detection circuit 44 detects a calling signal from the telephone line 8 and is in the calling state for making a telephone call, the pseudo leakage signal generating circuit 38 controls the transversal filter 40 according to a predetermined algorithm. After determining the filter coefficients and completing the call, a pseudo leakage signal S,1 equivalent to the leakage signal S, is generated, and this pseudo leakage signal S,l
Since has been digitized, it is subtracted from the digitized outgoing signal (st + so ). In this case, (St
+30) So '=St (However, S, -8・
'), the leakage signal from the speaker 12 is removed, and only the transmission signal consisting of the caller's voice is applied to the D/A 32, and after being converted into an analog signal again, it is sent via the hybrid circuit 6. and then sent to the telephone line 8.

Therefore, in such telephone equipment, the leakage signal path E
As a result of avoiding the influence of leakage signals from 1, it becomes possible to perform full duplex transmission and reception simultaneously and in parallel.

In addition, this telephone device is configured with an adaptive filter that automatically equalizes the reverberation of the space in which the microphone 2 and the speaker 12 are installed, that is, the closed space from the microphone 2 to the speaker 12. It is possible to generate a pseudo leakage signal equivalent to the leakage signal from the leakage signal path El generated by the leakage signal path El, thereby erasing the leakage signal contained in the transmitted signal, and it is possible to reliably avoid the influence of the leakage signal depending on the installation space.

(Example of configuration of pseudo leakage signal generation circuit 38) FIGS. 2 and 3 show a specific example of the circuit configuration of the pseudo leakage signal generation circuit 38, and FIG. 2 is at the time of calling (during coefficient determination training)
Figure 3 shows the configuration in call mode.

As shown in FIG. 2, the transversal filter 40 includes a plurality of delay elements 5L, 50g, 503...50.
are connected in series, and each delay element 50. ．． 50□
, 50. ...50. A calling signal (pulse) X(n) is applied to l from the calling signal detection circuit 44 when a telephone call is made, and the input is canceled during a call.

Further, the coefficient determination circuit 42 includes a delay element 508.50g,
50z . . . 507, a coefficient determination unit 62 . ．． 62□, 62, .
A subtracting amplifier 66 is installed to subtract the leakage signal output d (n) added from the A1028 at the time of call origination from the added output.

Therefore, this pseudo leakage signal generation circuit 38 constitutes a filter circuit equivalent to the characteristics of the leakage signal path E1, and after determining its filter coefficient at the time of making a call, it uses the filter path in the telephone when sending a call. This is intended to eliminate leakage signals.

Incidentally, in this pseudo leakage signal generation circuit 38, the filter coefficients are determined using the following algorithm.

That is, assuming a signal path considering the leakage signal path E1 shown in FIG. 3, input X (n), input weighting is coefficient W (n), output Y (n), d (n), error ε
(n), input X (n) is a calling pulse, and output d (n) is a signal component leaking through the leakage signal path EI during calling.

Therefore, when the input X (n) is multiplied by the weighting coefficient W (n) and the output y (n) is synthesized, the output y (n) is made equal to the desired output d (n). is weighted by the coefficient W
(n) so that the error ε (n>) between the desired output d (n) and the output y (n) is minimized. In other words, the output y (n) is y (n) - W (n)
・X (n)=X (n)W(n)
・ ・ ・(11), and the error ε (n) is ε (n)=d (n) −y
(n) ...(2) is expressed. That is, there is an error in the output y (n). However, M represents the number of data.

Here, Windrow-Hoff's Least M
When ean Square (LMS method) is used, the input weighting coefficient W can be expressed by the following equation.

W (n+1)=W (n)+2/7ε (n)・X
(n) ...(3) However, μ is a constant that compensates for the stability of the system.

In this equation (3), if n is set to infinity, W(n)
becomes W* (optimal coefficient).

Here, X (n)"' (Xt (n), Xt (n
), ・・XN (n)) ・・(4)
For, X (n) = (X (n-1> , X (n-
2).

・ ・ ・
can be realized.

In this pseudo leakage signal generation circuit 38, the output V (n) = d (n) for the input X (n), so that a filter equivalent to the leakage signal path E is formed. In this case, the filter coefficients are stored and set in the delay element 54 as delay coefficients.

In this pseudo leakage signal generation circuit 38, the filter coefficients are determined by the circuit configuration shown in FIG. It is configured as a filter.

As shown in FIG. 3, the pseudo leakage signal generation circuit 38 is connected to each coefficient determination unit 1-62. ．． 62□, 623...6
A switch 68 as a coefficient control means is connected to one input of the summing amplifier 52 of 21, and a similar switch 70 is connected to the feedback circuit of the summing amplifier 52. The circuit is broken by a similar switch 72 at the input of the subtraction amplifier 66, and each switch 70.7
2, the filter coefficients set at the time of calling are saved until the call or the next call, and the transversal filter 40 is configured as a constant coefficient filter by setting the filter coefficients.

During a call, X (n) is the transmit signal added from the A/D 28, and the delay elements 508, 502...50
, and the coefficient output of the delay element 54 output from each summing amplifier 52 are multiplied by a multiplier 60, and then each multiplication output is added by a summing amplifier 64 to form a digital signal. Output y (n) as simulated leakage signal component
is obtained. The output y (
n> is added to the subtracter 46 of the transmission system 4 and the A/D
The transmission signal is subtracted from the digital communication signal from 28 and the leakage signal component is removed from the subtracter 46 to the D/A 32.
is added to the signal, converted into an analog signal, and then sent out.

As explained above, when the calling pulse is used to determine the filter coefficients at the time of calling, there are the following advantages.

(al) The optimal filter coefficient can be automatically determined according to the surrounding environment each time the telephone is called.

(b) In the coefficient determination circuit 42, input X (n)
Since it is a pulse, only "0" and "1" are taken, and the above-mentioned hardware becomes very simple and costs can be reduced. That is, it can be realized by replacing the multiplication or addition of the coefficient determining circuit 42.

(Since clX(n) is a pulse, it is convenient for finding coefficients that match the surrounding environment. In other words, since it contains harmonics as a pulse, the transfer characteristics in the high frequency band can be understood. .

(Since the calling pulse is used as an input signal in the dl coefficient determination circuit 42, it is possible to simplify the hardware, thereby reducing costs.

(Second example) FIG. 5 shows a second embodiment of the telephone device of the present invention.

In the embodiment shown in FIG. 1, two sets of A/D 28.34 and two sets of D/A 32.36 are used.
The telephone equipment shown in the figure each has one set of A/Ds 29, D
/A33, these A/D 29, D/A
33 to perform analog-to-digital conversion or digital-to-analog conversion in a time-division manner.

The leakage signal canceling circuit 30 of this embodiment includes four sets of sample and hold circuits (S/H) 74, 76 due to time division.
．． Along with 78, 80, a switch circuit 82, 84 which is switched by the sample pulse is installed, and a sample pulse from a common sample pulse generating circuit 86 is applied.

The transmission signal or reception signal obtained from the switch circuit 82 is applied to the pseudo leakage signal generation circuit 38 via the A/D 29, and the transmission signal with the leakage signal eliminated by this pseudo leakage signal generation circuit 38 or the pseudo leakage signal The received signal obtained via the generation circuit 38 is applied to the D/A 33 and converted into an analog signal, and then sent to the switch circuit 84.
added to.

In this case, the pseudo leakage signal generation circuit 38 includes a transversal filter 4o and a coefficient determination circuit 4 that determines the coefficients of the transversal filter 4o.
2 and a memory 86 for storing the determined coefficients. Therefore, in order to realize the processing necessary for time-sharing, the determined filter coefficients are stored in the memory 86, and the stored coefficients are applied to the transversal filter 4o.
I am trying to set it sequentially.

A timing signal is applied to the A/D 29, D/A 33 and the pseudo leakage signal generation circuit 38 from a common sequencer 88, and the time division operation of the A/D 29, D/A 33 and the pseudo leakage signal generation circuit 38 is performed. This is achieved in a synchronized state.

In this way, the circuit configuration can be simplified in conjunction with digitalization of the leakage signal erasing process.

〔Effect of the invention〕

As explained above, according to the present invention, the following effects can be obtained.

(a) Since the leakage of received audio into the transmitted signal can be eliminated, full duplexing can be realized in which transmission and reception can be performed simultaneously in parallel.

(b) With this full duplex system,
This eliminates the need for conventional call switching depending on the audio signal level, and prevents the call from becoming unclear, such as the beginning of the voice cutting off immediately after the call change.

(C) If such signal processing is configured with an adaptive filter, the filter coefficients will be changed to be optimal for the surrounding environment each time the telephone is called by the calling signal and the leaked signal. There is no difference depending on the environment.

(dl If the leakage signal removal process is performed by digital signal processing, the response speed can be increased and the deterioration of characteristics due to aging can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the telephone device of the present invention, and FIGS. 2 and 3 are block diagrams showing specific circuit configuration examples of the pseudo leakage signal generating circuit of the telephone device shown in FIG. 4 is a circuit diagram showing a signal path including a leakage signal path, FIG. 5 is a block diagram showing a second embodiment of the telephone device of the present invention, and FIG. 6 is a block diagram showing a conventional telephone device.
FIG. 7 is a diagram showing the handset. 2...Microphone, 4...Transmission system, 10...
Receiving system, 12... Speaker, 3°... Leakage signal cancellation circuit, 4o... Transversal filter, El
...Leakage signal path. Figure 4 Figure 6b Figure 7

Claims (3)

[Claims] (1) A leakage signal erasing means for erasing leakage signals from the reception system to the transmission system is provided between the transmission system that sends transmission signals to the telephone line and the reception system that regenerates the reception signal from the exchange side. A telephone device characterized by being installed. (2) The leakage signal canceling means is configured using a filter that obtains a pseudo leakage signal from the reception signal that is equivalent to a leakage signal to the microphone of the reproduced sound of the reception signal, and 2. The telephone device according to claim 1, wherein a signal cancels a leakage signal from the receiving system to the transmitting system. (3) The coefficient of the filter is set according to the difference component between the calling signal and the leakage signal due to its looping around to the microphone at the time of reception, and the coefficient is changed according to the surrounding environment for each call. A telephone device according to claim 2.