JP3063454U - Mobile phone - Google Patents

Abstract

(57) [Summary] [Problem] Full-duplex communication without feedback is possible.
An object of the present invention is to provide a mobile phone which is easy to carry and has excellent call performance. In a portable telephone, a handset uses a gutter first speakerphone which can be inserted into an ear for converting an audio input into an electric transmission signal and an electric reception signal indicating audio data into an audio output at the same time. An amplifier / compressor 24 for communicating with the first speakerphone 20 is provided. The amplifier / compressor 24 receives a composite signal including the transmission signal and the reception signal, amplifies the transmission signal, and amplifies the reception signal. To generate an output signal in which the transmission signal is at least ten times larger than the reception signal.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a mobile phone that performs transmission and reception while holding all handsets.

[0002]

[Prior art]

 2. Description of the Related Art Conventionally, all handset handsets of mobile phones have a structure for handset transmission and reception. That is, when making a call, the user talks with the handset facing the ear and the mouth by hand, but there are various inconveniences. For example, when talking for a long time, the hand holding the handset tends to get tired. Also, in loud places such as stations and department stores, it may be difficult to hear the received voice due to external noise.

[0003] In a mobile phone, it is preferable to use full-duplex communication for a speakerphone, but it is difficult to apply "full-duplex communication" to a speakerphone due to problems of voice and electric feedback. When audio returns from the speaker to the microphone, audio feedback occurs. The same applies to electrical feedback, except that electrical feedback is due to audio inputs (signals sent to the remote controller) and audio outputs (signals received from the remote controller). If the transmitting circuit and the receiving circuit are not separated from each other, and if the gain of the formed loop is greater than 1, electric feedback occurs. To completely eliminate feedback, the total loop gain, including audio and electrical, must be less than one.

[0004] Speaker horns for hands-free and group communication are mainly in half-duplex arrangement. In such an arrangement, the following mutual switching (1) and (2) is performed using a high-speed switch circuit. (1) Output audio through a speaker. (2) Listen with a separate microphone. Without such switching, there would be a path for audio feedback from the speaker to the microphone, and the speaker would generate annoying noise. Since the switch circuit can prevent the speaker and the microphone from operating at the same time, the audio output from the speaker does not induce an electrical signal to the microphone. Switching circuits can cancel the annoying noise, but it has various disadvantages. That is, the user cannot transmit and listen at the same time. The switch circuit compares the strengths of the signals emitted by both, and transmits only the strongest signal.

[0005] Since full-duplex communication requires a complete closed loop circuit for both calling and receiving at the same time, its total loop gain must be less than one. As a method of reducing the loop gain to 1 or less, there is a method of detecting and canceling feedback using a digital signal process. A speakerphone according to this method is sometimes called a digital or full-duplex speaker. This type of device consists of separate speakers and microphones, and analog circuits corresponding to digital arithmetic circuits. The analog circuit has a suitable filter for determining the difference in signal gain between the transmission path and the reception path. This difference value is generated by the audio output of the received signal reaching the transmitter of the loop via the microphone. Depending on the result of detecting the feedback, the system reduces the loop gain to less than one with either electronically controlled attenuator on either side of the loop.

[0006] The attenuator can reduce the annoying noise due to the feedback and reduce the gain of the audio output so that the user cannot hear it, so that the potential function of the device can be exhibited. However, sometimes the attenuator may reduce the gain of the received signal so that the user does not even hear the other party. Also, the cost of a digital circuit arrangement is several times higher than that of a half-duplex speakerphone arrangement.

[0007] US Pat. No. 4,002,860 provides a method for solving a kind of voice feedback problem. Although the communication circuit described in this patent uses a speakerphone that serves both as a voice feedback and a microphone, the communication circuit according to this patent cannot efficiently cancel the electrical feedback. Although this communication circuit uses a hybrid speakerphone to separate a transmission signal and a reception signal, it can actually separate only 15 dB. The amount of separation depends primarily on the ability of the circuit to blend the impedance of the speakerphone and the telephone line. As long as the circuit does not have the ability to separate the transmitted and received signals, significant feedback is inevitable.

Another disadvantage of the US Pat. No. 4,002,860 patent is that the circuit carries the load through a speakerphone. The speakerphone load interferes with the transmission signal generated in the speakerphone due to voice input, and thus impairs the function of the circuit. In a typical microphone, the signal due to the user's sound is only about 10 mV, which is very small. Any load on the speakerphone will cause the energy of the signal to be lost. To compensate for such energy loss, the transmit signal processing circuit may amplify small audio signals. However, if any received signal feedback is fed back to the amplifier of the transmitting circuit, the aforementioned feedback problem is significant.

[0009]

[Problems to be solved by the invention]

 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a portable telephone which can perform full-duplex communication without feedback, is easy to carry, and has excellent call performance.

[0010]

[Means for Solving the Problems]

 In order to achieve the above object, the invention according to claim 1 is directed to a portable telephone comprising a telephone body and a handset connected to the telephone body, wherein the handset converts an audio input into an electric transmission signal. At the same time, a first speakerphone that can be inserted into the ear for converting an electric reception signal indicating audio data into an audio output is used, and a compression / amplifier that communicates with the first speakerphone is provided. It is characterized by receiving a composite signal composed of a transmission signal and a reception signal, amplifying the transmission signal and compressing the reception signal to generate an output signal in which the transmission signal is at least ten times larger than the reception signal.

The invention according to claim 2 provides a matching impedance element that matches the impedance of the first speakerphone and receives the reception signal, a compressor connected to the matching impedance element, And a differential amplifier connected to the compression / amplifier and the compressor.

The invention according to claim 3, wherein the matching impedance element is a second speakerphone that converts an audio input into a second electric transmission signal and converts the electric reception signal into an audio output. The compressor is a part of the second compression / amplifier, and is connected to the second speakerphone, and the differential amplifier is connected to the second compression / amplifier.

[0013] In the invention according to claim 4, in order to transmit a received signal to the first speakerphone without applying a load to the first speakerphone, the first speakerphone is connected to a linear amplifier. It is characterized by.

In the invention according to claim 5, the linear amplifier uses an operational amplifier having a non-reversing input and a reversing input, the non-reversing input receiving the reception signal, and the reversing input being the same. The linear amplifier is connected to a first speakerphone, and transmits a received signal to the speakerphone by the reverse input without applying a load to the speakerphone.

[0015] The invention according to claim 6 is characterized in that the speakerphone is driven by the received signal, and a two-way transistor for amplifying a transmission signal from the speakerphone is provided. .

A device according to claim 7, wherein said transistor has a base, a collector and an emitter, said base receiving said received signal and said speakerphone being a matching circuit connected to said emitter and collector. It is characterized by being connected to an impedance element.

In the invention according to claim 8, an inverter connected to the collector, an amplifier connected to an output of the speakerphone between the speakerphone and the compression / amplifier, and compressing the received signal. A compressor connected to the inverter, and a differential amplifier connected to the compressor / amplifier and the compressor, and the differential amplifier includes the composite signal from the compressor / amplifier and the compressor. It is characterized by receiving the received signal from the device and almost canceling the received signal.

The invention according to claim 9 is characterized in that it has an output stage for receiving the output signal of the compression / amplifier and amplifying the transmission signal and compressing the reception signal. The invention according to claim 10 is characterized in that the speakerphone is both a speaker and an earphone, and the invention according to claim 11 is characterized in that a microphone of the speakerphone uses a bone microphone. The invention according to claim 1, wherein the telephone body is attached to an arm, and the invention according to claim 13, wherein attachments for attaching the telephone body to the arm are provided at both ends of the telephone body. In the invention according to claim 14, each of the attachments uses a band which is attached to an end of the telephone body with a metal fitting, and both ends of the band are provided with mats. The invention is characterized in that a zip tape is provided, and the invention according to claim 15 is characterized in that the liquid crystal display section of the telephone body serves as a monitor of the telephone and also serves as a display section of a digital clock.

[0019]

[Embodiment of the invention]

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a telephone body according to an embodiment of the present invention, FIG. 2 is a perspective view showing a handset according to the embodiment of the present invention, and FIG. 3 is a perspective view showing a use mode of the mobile phone. . As shown in FIGS. 1 and 2, this mobile phone comprises a mobile phone body 1 and a handset 2 connected to the phone body 1. In particular, the telephone body 1 is attached to the wrist, and the handset 2 is a speakerphone (speaker and earphone) 20 that converts an audio input into an electric transmission signal and simultaneously converts an electric reception signal indicating audio data into an audio output. As shown in FIG. 4, an amplifier 22 connected to the speakerphone 20 and a compression / amplifier 24 connected to the amplifier 22 are provided, and the speakerphone 20, the amplifier 22 and the compression / amplifier 24 are provided. Thus, a full-duplex audio communication circuit is formed.

The amplifier 22 receives an electric input signal (received signal Rx) indicating an audio input and transmits the signal to the speakerphone 20. The speakerphone 20 converts the received signal into an audio output. The speakerphone 20 converts an audio input such as a user's voice into an electric transmission signal (transmission signal Tx). Therefore, if the speakerphone 20 has a function of a microphone for converting an audio input into an electric transmission signal, it also has a function of a speaker (earphone) for converting an electric signal from an external source into an audio output. . In particular, since the function of the speaker and the microphone is realized by a single speakerphone, there is no audio feedback path. Therefore, there is no need to use electronically controlled attenuators to reduce the effects of audio feedback.

Since the speakerphone 20 simultaneously receives the Rx signal and generates the Tx signal, a combined transmission / reception signal (Tx + Rx) is obtained at the output end of the speakerphone 20. The amplifier 22 transmits the composite signal to the compression / amplifier 24. The compression / amplifier 24 compresses the Rx signal and amplifies the Tx signal in the composite signal.

It is desirable that the compression / amplifier 24 uses a logarithmic circuit. This type of circuit amplifies the Tx signal by a logarithmic function and compresses the Rx signal. For example, in the speakerphone 20, the generated Tx signal is much smaller (about 3 mV) than the Rx signal (about 300 mV). The compression / amplifier 24 has a function of compressing a signal within a certain voltage range, but amplifies a signal within another voltage range. The purpose is to transmit the Tx signal and almost cancel the Rx signal so that no feedback occurs. To accomplish this, the compression and amplifier 24 compresses beyond a certain threshold voltage level, while amplifying it so as not to exceed a certain threshold level. In this manner, the compression / amplifier 24 can actually amplify the Tx signal and reduce the Rx signal by simultaneously compressing or amplifying different signals. Therefore, the difference between the transmission signal and the reception signal can be reduced.

A very good feature of the embodiment is that the amplifier 22 avoids loading on the speakerphone 20. Amplifier 22 drives speakerphone 20 to minimize the loss of received and transmitted signals. To obtain the best performance, the load applied to the received signal speakerphone 20 must be minimized. Any load on the speakerphone 20 will cause a portion of the transmitted signal to be lost. Usually, the transmitted signal is much smaller than the received signal, so loss of a portion of the transmitted signal can degrade performance. Also, when generating the transmit signal, the receive signal in speakerphone 20 must not be lost. In order to prevent the interference between the transmission signal and the reception signal, a method of providing an impedance (shunt) between the speakerphone 20 and the reception signal source has been proposed. Therefore, it is not preferable to divide the current into the speakerphone 20. In this embodiment, the amplifier 22 is connected to the speakerphone 20 in order to prevent a load from being applied to the speakerphone 20 and to prevent a shunt. Therefore, the amplifier 22 transmits the Tx signal with almost negligible loss, and applies the Rx signal to the speakerphone 20 with almost negligible loss.

The mobile phone according to FIG. 1 may use the audio communication circuit shown in FIG. In this circuit, the difference between the Tx and Rx signal levels is small (or both are at substantially the same level). This circuit has two input stages of matching, each of which has speakers and earphones 40 and 42 and amplifiers 44 and 46, respectively. Either of the two input stages operates as described above for FIG. However, the speaker / earphones 40 and 42 are connected with different polarities. Thus, the transmission signals of the two input stages have a phase difference of 180 °. Since the impedances of the two input stages are balanced, both received signals have substantially the same magnitude and phase, and the transmitted signals have the same magnitude, but differ by 180 ° in phase.

The circuit has a differential amplifier 48. The differential amplifier 48 receives a composite transmission / reception signal as input, amplifies the transmission signal Tx, and cancels the reception signal Rx. Normally, the output of differential amplifier 48 is proportional to the two input signals. Since the two received signals Rx and Rx have substantially the same phase, they are canceled each other. However, how much the two received signals Rx and Rx cancel each other depends on the matching state of the two input stages. Theoretically, the impedances of the two input stages are perfectly matched, but in practice, it is difficult to achieve perfect balance due to variations in each facility. Therefore, when the two input stages are matched, the received signals Rx and Rx are almost canceled at the output terminal of the differential amplifier 48, but are not completely canceled. Also, since the impedance of the received signal source changes well, there is a possibility that a phase difference may occur in the impedance of each input stage.

However, since the received signal is canceled using the differential amplifier 48, the speaker / earphone 40 or 42 is not necessarily used in all input stages. The speaker / earphone 40 or 42 may be replaced with a matching impedance. The matching impedance here is an induct or an RLC circuit having the same impedance function as the speaker / earphone 40 or 42. When a matching impedance device is used instead of the speaker / earphone 40 or 42, the transmission signal Tx is not generated at the input stage without the speaker / earphone 40 or 42. It has a similar function to the side where the amplifier is located. The differential amplifier 48 substantially cancels the reception signals on the various sides and amplifies the transmission signal Tx on the side having the speaker / earphone 40 or 42. Although not all input stages use the speaker / earphone 40 or 42, it is advantageous to use the same type of speaker / earphone for all input stages. One is to give the user a feeling of truth and a sense of the field. For example, audio output can be heard through the two speakers / earphones 40 and 42 to both the left and right ears. Since the differential amplifier 48 enhances the input signals with reverse polarity, the transmitted signal from the circuit is large. Also, when the same type of speaker / earphone is used on various sides, matching of impedance and phase can be easily achieved.

In general, the circuit shown in FIG. 5 has effects similar to the circuit shown in FIG. That is, the received signal can be reduced and the transmitted signal can be amplified. However, if the amount of separation between the Tx signal and the Rx signal is too large, a matching method between the compression / amplifier and the differential amplifier is used to effectively cancel the Rx signal in the Tx-Rx composite signal. There is a need to. The Tx signal generated in the speaker and earphone 40 or 42 by the audio input is much smaller than the Rx signal from the telephone line. The compressor / amplifier can reduce the amount of separation between the Tx signal and the Rx signal, and effectively causes the differential amplifier to cancel the Rx signal in the same mode as the Tx signal.

This mobile phone may use the audio communication circuit shown in FIG. The circuit shown in FIG. 6 summarizes the characteristics of the circuits shown in FIGS. That is, this circuit uses not only the differential amplifier 72 but also the compression / amplifiers 68 and 70 to simultaneously compress the received signal and amplify the transmitted signal. The differential amplifier arrangement of this circuit has an input stage with two matching impedances. The two input stages have loudspeakers and earphones 60 and 62 and amplifiers 64 and 66, respectively. Each side of the differential amplifier arrangement has compression and amplifiers 68, 70 for simultaneously compressing the received signal and amplifying the transmitted signal. The differential amplifier 72 receives the combined transmission / reception signal (Tx + Rx) from each side, cancels the reception signal Rx of the opposite side, and enhances the transmission signal Tx.

The circuit shown in FIG. 6 can effectively cancel the received signal and amplify the transmitted signal by integrating the differential amplifier arrangement and the compression / amplifier. It has higher performance than the circuit shown. This circuit preferably has a speaker and earphone on each side. Further, the speaker / earphone 60 or 62 may be replaced with an appropriate impedance element on one side. In this case, a compressor is used instead of the compression / amplifier 68 or 70 because there is no reception signal on the side having impedance.

The circuits shown in FIGS. 4 to 6 can both receive a composite signal based on the Tx and Rx signal amounts, amplify the Tx signal amount and compress the Rx signal amount, and connect to the speaker / earphone. It has an audio process circuit. For an audio process circuit, the ability to substantially cancel Rx and generate a Tx signal that is larger than the Rx signal depends on the levels of the Tx and Rx signals in the loudspeaker / earphone and the specific arrangement of this audio circuit. It is.

In FIG. 4, the audio process circuit has a compression / amplifier 24. If the Tx signal is much smaller than the Rx signal, this amplifier 24 is very effective in reducing the difference between the Tx and Rx signals. However, in a normal case, the Tx signal from the speaker / earphone is very small. Therefore, it is not possible to cancel the Rx signal by making the Tx signal larger than the Rx signal only by this compression / amplifier.

In FIG. 5, the audio process circuit has a differential amplifier 48. If the two input sides of the differential amplifier 48 are well matched and the separation between the Tx and Rx signals is very small, then the differential amplifier will effectively cancel the Rx signal corresponding to the Tx signal. Can be. However, when the levels of the Tx signal and the Rx signal do not sufficiently match, the differential amplifier alone does not provide an excellent effect.

In FIG. 6, the audio process circuit is a circuit that includes compression / amplifiers 68 and 70 and a differential amplifier 72. First, the compression / amplifiers 68 and 70 reduce the difference between the Tx and Rx signals, and the differential amplifier 72 almost cancels the common mode Rx signal, so that the audio process circuit effectively uses the Rx signal corresponding to the Tx signal. The signal can be canceled.

The detailed contents of the various audio process circuits shown in FIGS. 4, 5 and 6 are shown in the detailed configuration diagram of the full-duplex audio communication circuit of FIG. The circuit shown in FIG. 7 amplifies the transmission signal at the same time and reduces the reception signal from the external audio source in the same way as the circuit shown in FIG. Is also used. Speaker / earphones 100 and 102, amplifiers 104 and 106, and compression / amplifiers 108 and 110 are provided on all sides of the differential amplifier arrangement.

The output terminals 112, 114 of the compression / amplifiers provided on both sides of the differential amplifier arrangement are connected to a differential amplifier 116. The output of the differential amplifier 116 is connected to the output stage 118. Output stage 118 amplifies the transmitted signal, compresses the received signal, and adjusts the output voltage level to a normal level. The output stage 118 is capable of producing a final transmitted signal 120 and a substantially negligible received signal that is at least 30 dB below this transmitted signal. This circuit can achieve a full-duplex function with very little feedback by simultaneously compressing the received signal and amplifying the transmitted signal.

The input received signal 122 enters the circuit by a pass band equalizer 124. During this particular arrangement, the pass band equalizer 124 uses a conventional bipolar pass band equalizer. The function of this pass band equalizer equalizes the audio output of the speaker / earphone 100, 102. At higher frequencies, the frequency response of the received signal is particularly weak. In order to equalize the frequency of the received signal, the pass band equalizer includes a leakage circuit that offsets and balances the frequency response.

The output 126 of the pass band equalizer 124 is supplied to the amplifiers 104 and 106 on both sides of the differential amplifier arrangement. FIG. 7 shows a method in which when the received signal is applied to the speaker / earphone by the amplifier, the speaker / earphone does not load or shunt. In an embodiment, the amplifier 104 uses an operational amplifier 128 with a resistor R1 (130), which is connected between the anti-phase input 132 and the output 134 of the operational amplifier 134. Since there are so many types of operational amplifier circuits, for example, a kind of operational amplifier such as LM324 or TL084 may be used in the circuit. The received signal enters the non-inverting input 136 of the operational amplifier through a pass band equalizer. The negative-phase input 132 of the amplifier is connected to the speaker / earphone 100, and the other end of the speaker / earphone is connected to the ground.

Since the current mirror deviation of the operational amplifier 128 functions like a current source, the operational amplifier 128 receives the Rx signal at the non-inverting input and then transmits the Rx signal to the Transmit to earphone 100. Since the antiphase input 132 is provisionally grounded, the voltage to ground is approximately equal to zero. This provisional ground does not reduce the current, and all input current from the Rx signal flows through R1 (130).

Therefore, the voltage gain of the amplifier 104 is equal to −R1 / Z1. A minus sign means that the phase of the input and the output of the operational amplifier are exactly opposite. Also, since the negative-phase input is a temporary ground, the input impedance of the amplifier is equal to Z1, that is, the impedance of the speaker / earphone 100. By using a unique method of driving the speaker / earphone 100 without loading or shunting, the amplifier can convert the electric signal (approximately 300 mV) due to the audio input from the speaker / earphone with a negligible signal loss. To the output 134 of the operational amplifier.

The amplifiers 106 and 104 on both sides of the differential amplifier arrangement have a similar design. However, the speaker / earphone 102 is connected to the amplifier 106 with a polarity opposite to that of the speaker / earphone 100 on the other side of the differential amplifier arrangement. This allows the differential amplifier 116 to amplify transmission signals from both sides of the differential amplifier arrangement by about one. As a point, a device such as an inductor may be used instead of the speaker and earphone 102 as described above. This device must match the impedance of the speaker and earphone 100 on the other side of the differential amplifier arrangement. When using matching impedance instead of speaker and earphone 102, there is only a received signal on this side of the circuit. Therefore, the amplifier part in the compression / amplifier is not required.

The output signals of amplifiers 104 and 106 are transmitted to compression amplifiers 108 and 110 on both sides of the differential amplifier arrangement, respectively. The compression / amplifiers 108 and 110 compress a large received signal and amplify a small transmitted signal using a normal compander IC. The received signal, when amplified by the amplifiers 104 and 106, is 15 to 30 times larger than the transmitted signal from the audio output of the speaker and earphone. Therefore, the ratio between the reception signal and the transmission signal at the output terminals of the compression / amplifiers 108 and 110 reaches about 20: 1. In contrast, using a compander IC, the proportion between the received signal and the transmitted signal is reduced to 6: 1. This compander IC compresses a received signal by a logarithmic function and amplifies a transmitted signal.

The differential amplifier 116 receives the output of the compression / amplifier (112, 114) and generates an output signal. The transmission signal here is larger than the reception signal. The differential amplifier 116 includes an operational amplifier 150 and resistors R3, R4, R5, and R6 (152 to 158). The resistors R3 and R5 are connected between the output matched to the compression amplifier and the two inputs of the operational amplifier 150. Resistor R4 is connected between one input and output of operational amplifier 150, and resistor R6 is connected between the other input and ground.

The large received signals are transmitted to the differential amplifier 116 in a common mode, and these signals are net canceled at the output and 30-40 dB below the original level at the input. Since the small transmission signals have opposite polarities, they are first amplified by the compression / amplifiers 108 and 110, and then further amplified by the operational amplifier 150. The output of operational amplifier 150 produces a combined transmit and receive signal. The transmitted signal portion of this composite signal is 20-30 dB larger than the undesired received signal.

The output signal of the differential amplifier 116 is transmitted to a horizontal transition circuit in the output stage 118. This horizontal transition circuit comprises resistors R7 and R8 (160, 162). The reason for using this circuit is to adjust the signal level of the output terminal of another compression / amplifier 164. This special compression / amplifier 164 further amplifies the transmission signal and compresses the reception signal. Since the transmission signal level at this point is higher than that of the reception signal, a compression / amplifier 164 is provided in the output stage 118. The compression / amplifier 164 generates a signal above a certain reference threshold voltage level and also generates a signal below another reference threshold level. The horizontal transition circuit ensures that the input of the compression / amplifier 164 operates smoothly at normal levels.

As the compression / amplifier 164, a normal compander IC is used. The compander IC can generate a larger delimiter between the Tx signal and the Rx signal. In this part of the circuit, the compander IC amplifies the difference between Tx and Rx, but within the input stage the compander IC will reduce the difference between the Tx and Rx signals. Thus, by performing compression and amplification at the same time, the output signal has only a negligible small signal, that is, the transmission signal portion is about 30 to 40 dB larger than the reception signal portion. Therefore, the feedback of the reception signal to the transmission signal is almost canceled.

The output stage 118 has an automatic level control circuit 168. This circuit receives the output of the compression / amplifier 164 and adjusts it to an even output level. For example, the transmission signal needs to be at a level of about -5 dB. Here, the automatic level control circuit 168 is very effective.

The full-duplex communication circuit shown in FIG. 7 has various advantages. The special arrangement of the operational amplifier that matches the speaker and earphone avoids any load or shunt on the speaker and earphone. Thus, the amplifier transmits a small electrical signal from the audio input to its output with negligible loss. Also, since there is no shunting of the received signal, interference between the received signal and the transmitted signal can be prevented, and the power of the received signal is reduced so as to be almost inaudible. Another advantage of this circuit is that since the compression / amplifier and differential amplifier are used collectively, the received signal from the output of the communication circuit is almost canceled. The compander IC and the differential amplifier simultaneously amplify the transmission signal and compress the reception signal, so that the feedback is almost canceled.

The front end of the full-duplex communication circuit shown in FIG. 8 uses a transistor to (1) drive a speakerphone having a received signal from a remote source, and (2) generate a speakerphone by an audio input. It has a function of amplifying a transmission signal. This received signal is input to the circuit via a pass band equalizer 250 for adjusting the balance of the signal frequency response. The output of this pass band equalizer 250 passes through capacitor C1 (252). Resistors R1 (258) and R2 (254) form a voltage divider that supplies the required base voltage to transistor 256. The capacitor connects the output of the pass band equalizer 250 to the input mode of the emitter arrangement of the bipolar junction transistor 256.

The transistor amplifier has an NPN transistor 256 and four resistors R 1, R 2, R 3, R 4 (258, 254, 260, 262). This transistor amplifier is connected between the supply voltage Vcc and ground. Resistor R1 is connected between the supply voltage and the base of transistor 256, and resistor R2 is connected between the base of transistor 256 and ground. The emitter is connected to the output of speakerphone 264 via resistor R4. On the collector side, the collector is connected via a resistor R3 to a matching impedance element or speakerphone 266. A speakerphone or matching impedance element on the collector side is connected between supply voltage VCC and resistor R3 (260).

Since the impedance between the collector and the emitter of the transistor is balanced, two matched outputs are formed at the collector and the emitter, and both outputs generate received signals having different phases. For a signal applied to the input of the emitter, the transistor behaves like an inverter, so the phase of the received signal at each output is different. If any of the inputs change, the resulting signal will all be included in the received phase signal. These signals are then provided to the differential amplifier and canceled. Actually, the matching impedance on the collector side may be a speakerphone exactly the same as the speakerphone 264 on the emitter side, or an element having a matching impedance of the speakerphone 264.

The communication circuit shown in FIG. 8 uses a transistor as an amplifier with a common emitter and a common base arrangement. For an arrangement having both a shared emitter and a shared collector, the current gain is equal to the current beta factor of the transistor. Similarly, for an arrangement having a shared emitter and a shared base, the voltage gain is equal to the quotient of the collector impedance and the emitter (Rc / Re). "Shared" in a bipolar transistor means that the transistor terminal is also an output terminal if it is an input terminal. That is, it means an input / output shared terminal. Therefore, for a shared emitter arrangement, the emitter terminal is an I / O shared terminal. Naturally, in a shared base arrangement, the base terminal is an input / output shared terminal. In a shared emitter arrangement, the input node is the base of the transistor and the output node is the collector. During a shared base configuration, the input node is the emitter of the transistor and the output node is the collector.

The transistor amplifier shown in FIG. 8 amplifies a received signal using a common base arrangement. Transistor 256 amplifies the current of the received signal provided to the base. The amount of amplification is equal to the current gain of the transistor. The voltage applied to the speakerphone 264 is approximately equal to the voltage of the received signal, ignoring the threshold voltage drop between the base and the emitter (about 0.7V) and the voltage drop across resistor R4.

The speakerphone 264 converts the audio output into a transmission signal at the output of the speakerphone. In a shared base arrangement, this transmit signal feeds the input of transistor 256. Therefore, this transmission signal obtains a voltage gain equal to the voltage gain suitable for the shared emitter arrangement.

The transistor amplifier arrangement shown in FIG. 8 provided a method of effectively driving a speakerphone without a load. Since the electrical signal generated by the switch from the audio input is very small, the speakerphone can greatly reduce the transmitted signal under any load.

In FIG. 8, both outputs of the transistor amplifier are provided to opposite sides of the differential amplifier. The output of one side of the differential amplifier arrangement is obtained from the collector of transistor 256 and provided to inverter 270. When the inverter 270 inverts the transmission and reception signals, (1) the transmission signals on both sides of the differential amplifier arrangement undergo phase transition, and (2) the reception signals on both sides are in the same phase. As described above, because transistor 256 operates like an inverter, the received signal at the collector of transistor 256 is out of phase with the received signal at the base of the transistor. Therefore, the received signal output at the collector must be inverted in order for the received signals to be of the same magnitude and in phase on any side of the differential amplifier arrangement. The output on the other side of the differential amplifier arrangement is due to the output of speakerphone 264. At this output node, the received signal has the same phase as the received signal supplied to transistor 256, but undergoes a phase transition with respect to the output of the collector of transistor 256. The transmission signal from the speakerphone 264 has the same phase as the transmission signal at the transistor output.

The composite transmit / receive signal at the speakerphone output is provided to a linear amplifier 272 having a gain equal to the gain of inverter 270. This linear amplifier 272 amplifies the composite transmit / receive signal and supplies its output to the other side of the differential amplifier arrangement.

The inverter 270 uses an operational amplifier and resistors R4, R5, R6 (276, 278, 280). The gain of the inverter is equal to R5 / R4. The linear amplifier 272 has a similar configuration. However, the output is supplied to the non-inverting input of the operational amplifier 290. The linear amplifier 272 has an operational amplifier 290 and three resistors R7, R8, R9 (292, 294, 296), the gain of which is equal to R8 / R7.

The outputs of both the inverter 270 and the linear amplifier 272 are supplied to the differential amplifier. The differential amplifier sums the transmitted signals on each side and cancels most of the received signals. To achieve good performance, the output of the inverter and the linear amplifier are provided to two similar compressors / amplifiers that simultaneously compress the received signal and amplify the transmitted signal. Specifically, the outputs of the inverter and the linear amplifier are supplied to the compression / amplifiers 108 and 110 shown in FIG. The other parts of this communication circuit are the same as the circuit shown in FIG.

The handset 2 uses a speakerphone 20 (40 and 42, 60 and 62, 100 and 102, or 264) and a full-duplex communication circuit as shown in FIG. 4, 10, 11, 12, or 13. Therefore, according to FIG. 2, the handset 2 in the present embodiment can be formed into the shape of a normal earphone according to FIG. Therefore, it is possible to make a call while holding the handset 2 near the ear.

The microphone of the speakerphone 20 (40 and 42, 60 and 62, 100 and 102, or 264) is preferably a bone microphone. As a result, the human voice resonates with the skull and becomes a very good voice, and can talk under any noise.

Further, by using the handset 2 that can be plugged into the ear, when operating the telephone body 1, instead of pressing the function button of the telephone body 1, it is also possible to operate by voice alone. For example, chewing the back teeth twice can be regarded as the start of reception, and chewing the back teeth three times can be regarded as the end of the call.

On the other hand, attachments 11 and 12 for attaching the telephone main body 1 to the arm are provided at both ends of the telephone main body 1. In the present embodiment, a band 14 to be attached to the end of the telephone body 1 with a metal fitting 15 is used for each of the fittings 11 and 12. At both ends of the band 14, magic tapes 13, 13 are provided. Further, the liquid crystal display section 16 of the telephone body 1 may be used as a display of a digital clock as well as a monitor of the telephone. For this reason, the telephone body 1 is not only a telephone but also a clock.

The telephone body 1 and the transmission / reception device 2 communicate with each other wirelessly or by wire. When using the telephone, as shown in FIG. 3, the telephone main body 1 is attached to the user's arm via the attachments 11 and 12, and the handset 2 is attached to the user's ear.

[0064]

[Effect of the invention]

 As is apparent from the above description, according to the present invention, since the full-duplex communication circuit used in the telephone has neither voice feedback nor electric feedback, the handset can use a speaker and an earphone. You can talk with the handset on your ear.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a telephone body of a mobile phone according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the handset of the mobile phone according to the embodiment of the present invention;

FIG. 3 is a perspective view showing a method of using the mobile phone according to FIGS. 1 and 2;

FIG. 4 is a block diagram of a full-duplex communication circuit used by the mobile phone according to the embodiment.

FIG. 5 is a block diagram of another full-duplex communication circuit used by the mobile phone according to the embodiment.

FIG. 6 is a block diagram of another full-duplex communication circuit used by the mobile phone according to the embodiment.

FIG. 7 is a detailed diagram of a full-duplex communication circuit used by the mobile phone according to the embodiment.

FIG. 8 is a detailed diagram of another full-duplex communication circuit used by the mobile phone according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Telephone main body 2 Handset 11 and 12 Fixture 13 Magic tape 14 Band 16 Liquid crystal display part 15 Metal fitting 22 Amplifier 24 Compression / amplification 40, 42 Speaker and earphone 48 Differential amplifier 68 Compression / amplifier 70 Compression / amplifier 72 Differential amplifier REFERENCE SIGNS LIST 100 speaker / earphone 102 speaker / earphone 104 amplifier 106 amplifier 108 compression / amplifier 110 compression / amplifier 112 output terminal 114 output terminal 116 differential amplifier 118 output stage 120 final transmission signal 122 input reception signal 124 pass band equalizer 126 output 128 Operational amplifier 130 Resistance R1 132 Negative phase input 134 Output 136 Non-negative phase input 150 Operational amplifier 164 Compression amplifier 168 Automatic level control circuit 250 Pass band equalizer 2 2 capacitors C1 254 resistor R1 256 transistor 258 resistor R2 260 resistor R3 262 resistor R4 264 speakerphone 270 inverter 276 resistor R4 278 resistor R5 280 resistor R6 290 operational amplifier 292 resistors R7 294 resistor R8 296 resistor R9 VCC supply voltage

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04M 1/05 H04B 7/26 Q

Claims (15)

[Utility model registration claims] 1. A portable telephone comprising a telephone body and a handset connected to the telephone body, said handset converts an audio input into an electric transmission signal and simultaneously converts an electric reception signal indicating audio data into an audio output. A first speakerphone that can be inserted into the ear of the user, and a compression / amplifier that communicates with the first speakerphone is provided. The compression / amplifier receives a composite signal including the transmission signal and the reception signal, and A portable telephone characterized by amplifying the transmission signal and compressing the reception signal to generate an output signal in which the transmission signal is at least ten times larger than the reception signal. 2. A matching method for matching the impedance of the first speakerphone and receiving the received signal.
2. The mobile phone according to claim 1, further comprising an impedance element, a compressor connected to the matching impedance element, and a differential amplifier connected to the compression / amplifier and the compressor. 3. The matching impedance element is a second speakerphone that converts an audio input to a second electrical transmission signal and converts the electrical reception signal to an audio output, and wherein the compressor is a second compression amplifier. And is connected to the second speakerphone,
The mobile phone according to claim 2, wherein the differential amplifier is connected to the second compression / amplifier. 4. The first speakerphone is connected to a linear amplifier for transmitting a received signal to the first speakerphone without applying a load to the first speakerphone. Mobile phone. 5. The linear amplifier uses an operational amplifier having a non-reversing input and a reversing input, the non-reversing input receiving the reception signal, the reversing input being connected to the first speakerphone, and 5. The mobile phone according to claim 4, wherein the linear amplifier transmits a reception signal to the speakerphone by the reverse input without applying a load to the speakerphone. 6. The mobile phone according to claim 1, further comprising a two-way transistor for driving the speakerphone with the received signal and amplifying a transmission signal from the speakerphone. 7. The transistor has a base, a collector and an emitter, the base receiving the received signal, and the speakerphone being connected to a matching impedance element connected to the emitter and the collector. The mobile phone according to claim 6, wherein: 8. An inverter connected to the collector, an amplifier connected to an output of the speakerphone between the speakerphone and the compression / amplifier, and connected to the inverter for compressing the received signal. A compressor, and a differential amplifier connected to the compressor / amplifier and the compressor, the differential amplifier receiving the composite signal from the compressor / amplifier and the received signal from the compressor; 8. The portable telephone according to claim 7, wherein said received signal is almost canceled. 9. The mobile phone according to claim 1, further comprising an output stage for receiving an output signal of the compression / amplifier, amplifying the transmission signal, and compressing the reception signal. . 10. The speakerphone according to claim 1, wherein the speakerphone is a speaker / earphone.
10. The mobile phone according to 6, 7, 8 or 9. 11. The mobile phone according to claim 1, wherein a microphone of the speakerphone uses a bone microphone. 12. The portable telephone according to claim 1, wherein said telephone body is attached to an arm. 13. The portable telephone according to claim 12, wherein attachments for attaching the telephone main body to an arm are provided at both ends of the telephone talker main body. 14. The telephone according to claim 13, wherein each of the attachments uses a band attached to an end of the telephone body with metal fittings, and a magic tape is provided at both ends of the band. Mobile phone. 15. The portable telephone according to claim 12, wherein the liquid crystal display of the telephone body serves as a monitor of the telephone and also serves as a display of a digital clock.