JP4893394B2 - Communication device - Google Patents

Description

  The present invention relates to a digital modulation communication apparatus.

  Conventionally, various digital modulation communication devices have been provided (see, for example, Patent Document 1). FIG. 7 shows a conventional configuration of a digital modulation communication apparatus. The transmission signal digitally modulated by the signal processing unit 30 is digital-analog converted by the D / A conversion unit 31, amplified to a desired signal level by the transmission side amplifier 33 via the filter circuit 32, and then transmitted to the transmission line Ls. Is done. The transmission signal received from the transmission line Ls is amplified by the reception side amplifier 35 through the filter circuit 34, then analog-to-digital converted by the A / D conversion unit 36, and digitally demodulated by the signal processing unit 30.

In general, since a digital-analog converted signal includes aliasing noise (alias) on the high band side, an unnecessary high frequency is provided by providing a filter circuit 32 having a low-pass characteristic at the subsequent stage of the D / A converter 31. Ingredients are removed. Similarly, in order to suppress the influence of aliasing noise in the analog-to-digital conversion of the receiving system, an unnecessary high frequency component is removed by providing a filter circuit 34 having a low-pass characteristic in the previous stage of the A / D converter 36. is doing. In the filter circuits 32 and 34, steep filter characteristics are necessary to avoid interference with unnecessary high frequency components.
JP 2004-56275 A

  However, in order to realize steep filter characteristics, a high-order filter is required, and if such a high-order filter is to be realized with a passive filter configuration, the number of circuit elements (resistors, inductors, capacitors, etc.) is large. In particular, the mounting area also increases due to the influence of the inductor. On the other hand, when an active filter configuration is used, the circuit scale and power consumption increase as compared with the passive type. Therefore, in the digital modulation type communication apparatus, downsizing of the filter circuit is an important issue.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a communication apparatus that can be reduced in size and power consumption due to a reduction in circuit scale.

In order to achieve the above object, a first aspect of the present invention provides a modulation unit that digitally modulates transmission data, a D / A conversion unit that converts a digital transmission signal modulated by the modulation unit into an analog transmission signal, Filter circuit for removing high frequency components contained in analog signal, A / D converter for converting analog received signal received through transmission path to digital received signal, and converted by A / D converter A demodulator that demodulates received data from a digital received signal, a transmission path that transmits an analog transmission signal from a D / A converter to a transmission path via a filter circuit, and a filter circuit that receives an analog reception signal from the transmission path and a reception path switching means for switching alternatively the receive path to be input to the a / D converter through the transmission and reception path switching means, response to the path of the transmission path or the receive path It characterized by having a variable gain amplifier which amplifies an analog signal output from the filter circuit gain.

  According to a second aspect of the present invention, in the first aspect of the invention, the transmission / reception path switching means includes a pair of amplifiers provided on the input side and output side of the filter circuit in the transmission path, and the input side and output of the filter circuit in the reception path. And a pair of amplifiers provided on the side, and the transmission path and the reception path are selectively switched by ON / OFF control of the operation of each pair of amplifiers.

According to a third aspect of the present invention, in the first or second aspect of the invention, when the transmission / reception path switching means is switched to the reception path, the gain corresponding to the signal level of the reception signal is set in the amplifier and the transmission path is switched. A predetermined gain is set in the amplifier.

The invention of claim 4 is the invention according to any one of claims 1 to 3 , wherein the transmission / reception path switching means always forms a path from the output end of the filter circuit to the A / D converter. .

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the transmission / reception path switching means is configured to transmit or It is characterized by switching to a reception path.

According to the invention of claim 1, since one filter circuit is shared by the transmission path and the reception path, as compared with the case where a dedicated filter circuit is provided for each of the transmission path and the reception path as in the conventional example, Miniaturization and low power consumption can be achieved by reducing the circuit scale. In addition, the amplifier that amplifies the transmission signal and the amplifier that amplifies the reception signal can be shared by one amplifier, and the circuit scale can be further reduced.

  According to the second aspect of the present invention, signal attenuation accompanying switching can be reduced as compared with the case where the transmission path and the reception path are switched by a switch.

According to the invention of claim 3 , the reception sensitivity can be improved.

According to the fourth aspect of the present invention, it is possible to reduce the noise input to the demodulator when the path is switched.

According to the fifth aspect of the present invention, it is possible to prevent the transmission path and the reception path from being short-circuited to form a closed loop, thereby enabling stable communication.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, in each embodiment described below, a communication apparatus used in a communication system adopting a TDMA (Time Division Multiple Access) system is illustrated, but for example, used in a communication system adopting a CSMA (Carrier Detection Connection) system. It is possible to apply the technical idea of the present invention to a communication apparatus.

(Embodiment 1)
As shown in FIG. 1A, the communication apparatus according to the present embodiment includes a modulation unit 1 that digitally modulates transmission data, and a D / A that converts a digital transmission signal modulated by the modulation unit 1 into an analog transmission signal. A conversion unit 2; a filter circuit 3 that removes high-frequency components contained in the analog signal; an A / D conversion unit 4 that converts an analog reception signal received via the transmission line Ls into a digital reception signal; A demodulator 5 for demodulating received data from the digital received signal converted by the / D converter 4, an amplifier 6 for amplifying an analog signal output from the filter circuit 3, and a filter circuit 3 from the D / A converter 2 A transmission path for transmitting an analog transmission signal to the transmission line Ls via the transmission line, and a reception path for inputting an analog reception signal received from the transmission line Ls to the A / D conversion unit 4 via the filter circuit 3. And a reception path switching means for switching to one basis.

  At the time of transmission, the transmission signal Ls digitally modulated by the modulation unit 1 is digital-analog converted by the D / A conversion unit 2, amplified to a desired signal level by the amplifier 6 through the filter circuit 3, and then the transmission line Ls. Sent to. At the time of reception, the received signal received from the transmission line Ls is amplified to a desired signal level by the amplifier 6 through the filter circuit 3 and then analog-digital converted by the A / D converter 4 to be demodulated by the demodulator 5. Is digitally demodulated. As described in the conventional example, the high-frequency aliasing noise included in the digital-analog converted transmission signal is removed by the filter circuit 3 having a low-pass characteristic, and similarly, the influence of the aliasing noise in the reception signal is suppressed. Therefore, unnecessary high frequency components are removed by the filter circuit 3 before the A / D conversion unit 4.

  The transmission / reception path switching means includes a normally closed contact 7a connected to the transmission path Ls, a normally open contact 7b connected to the output end of the D / A converter 2, and a common contact 7c connected to the input end of the filter circuit 3. Connected to the first switching unit 7 comprising an analog switch, a normally open contact 8b connected to the transmission line Ls, a normally closed contact 8a connected to the input end of the A / D converter 4, and an output end of the amplifier 6 The second switching unit 8 is an analog switch having a common contact 8c, and the control unit 9 outputs a switching signal for switching the first switching unit 7 and the second switching unit 8. However, in the present embodiment, the modulation unit 1, the demodulation unit 5, and the control unit 9 are configured as one integrated circuit IC.

  Here, when the control unit 9 is not outputting a switching signal, the common contacts 7c and 8c of the first switching unit 7 and the second switching unit 8 are both connected to the normally closed contacts 7a and 8a. The path (reception path) of the transmission path Ls → the first switching unit 7 → the filter circuit 3 → the amplifier 6 → the second switching unit 8 → the A / D conversion unit 4 → the demodulation unit 5 is formed. On the other hand, when the control unit 9 is outputting a switching signal, the common contacts 7c and 8c of the first switching unit 7 and the second switching unit 8 are all switched and connected to the normally open contacts 7b and 8b. A path (transmission path) of section 1 → D / A conversion section 2 → first switching section 7 → filter circuit 3 → amplifier 6 → second switching section 8 → transmission path Ls is formed. That is, in this embodiment, since the same transmission path Ls is used for transmission and reception, the transmission operation and the reception operation can be performed only alternatively, and the D / A conversion unit 2 and the A / D conversion are performed. Since the sampling frequency is also common to the unit 4, the filter characteristics for removing unnecessary high frequency components from the analog signal (analog transmission signal and analog reception signal) may be the same. For this reason, the transmission system and the reception system Thus, the filter circuit 3 can be shared.

  Since the communication system using the communication apparatus according to the present embodiment performs TDMA communication, signals are transmitted in a plurality of time slots TM1, TM2,... Defined by synchronization signals (not shown) as shown in FIG. Is transmitted. Then, before the time slot TM1 for reception ends and the time slot TM2 for transmission starts, the control unit 9 outputs a switching signal to switch from the reception path to the transmission path, and the time slot TM2 for transmission ends. Then, before the reception time slot TM3 starts, the control unit 9 stops the output of the switching signal and switches from the transmission path to the reception path.

  As described above, since one filter circuit 3 is shared by the transmission path and the reception path in the present embodiment, the circuit is compared with a case in which dedicated filter circuits are provided in the transmission path and the reception path as in the conventional example. The scale can be reduced and the communication apparatus can be reduced in size, and since only one filter circuit 3 is required, power consumption can be reduced as compared with the conventional example. In the present embodiment, not only the filter circuit 3 but also the amplifier 6 is shared. However, if necessary, separate amplifiers may be provided for the transmission path and the reception path to amplify the transmission signal and the reception signal separately. I do not care.

(Embodiment 2)
The present embodiment is characterized by the configurations of the first switching unit 10 and the second switching unit 11 that constitute the transmission / reception path switching means together with the control unit 9, and the other configurations are the same as those of the first embodiment. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The first switching unit 10 includes a buffer amplifier 10 a having an input end connected to the transmission line Ls and an output end connected to the input end of the filter circuit 3, and an input end connected to the output end of the D / A converter 2. And a buffer amplifier 10 b whose output end is connected to the input end of the filter circuit 3. The operation state of the two buffer amplifiers 10a and 10b is turned on / off by the switching signal output from the control unit 9 (the output impedance is relatively high when it is off, and the output impedance is relatively low when it is on). When the switching signal is not output from the control unit 9, the buffer amplifier 10a is turned on and the buffer amplifier 10b is turned off. When the switching signal is output from the control unit 9, the buffer amplifier 10a is turned off. 10b is turned on.

  The second switching unit 11 has an output end connected to the transmission line Ls and an input end connected to the output end of the amplifier 6 and an output end connected to the input end of the A / D conversion unit 4. And a buffer amplifier 11b whose input end is connected to the output end of the amplifier 6. The two buffer amplifiers 11a and 11b are turned on / off by a switching signal output from the control unit 9. When the switching signal is not output from the control unit 9, the buffer amplifier 11a is turned off. When 11b is turned on and a switching signal is output from the control unit 9, the buffer amplifier 11a is turned on and the buffer amplifier 11b is turned off.

  Thus, as shown in FIG. 2B, when the control unit 9 outputs a switching signal before the reception time slot TM1 ends and the transmission time slot TM2 starts, the first switching unit 10 When the buffer amplifier 10a is turned off, the buffer amplifier 10b is turned on, and the buffer amplifier 11a is turned on and the buffer amplifier 11b is turned off in the second switching unit 11, the modulation unit 1 → D / A conversion unit 2 → first switching unit. 10 (buffer amplifier 10b) → filter circuit 3 → amplifier 6 → second switching unit 11 (buffer amplifier 11a) → transmission path Ls (transmission path) is formed, and the reception path can be switched to the transmission path. On the other hand, if the control unit 9 stops outputting the switching signal before the transmission time slot TM2 ends and the reception time slot TM3 starts, the buffer amplifier 10a is turned on and the buffer amplifier 10b is turned on in the first switching unit 10. Is turned off and the buffer amplifier 11a is turned off and the buffer amplifier 11b is turned on in the second switching unit 11, whereby the transmission line Ls → the first switching unit 10 (buffer amplifier 10a) → the filter circuit 3 → the amplifier 6 → second. A path (reception path) of the switching unit 11 (buffer amplifier 11b) → A / D conversion unit 4 → demodulation unit 5 is formed, and the transmission path can be switched to the reception path.

  As described above, according to the present embodiment, the transmission path and the reception path are selectively switched by turning on / off the buffer amplifiers 10a, 10b, 11a, and 11b, so that an analog switch is used as in the first embodiment. Compared with the case, the attenuation of the signal accompanying switching can be reduced. Actually, the signal is not completely cut off even when it is off, and there is a signal that passes slightly. Therefore, there is a signal component that returns to the transmission path via the buffer amplifier 10a of the first switching unit 10 at the time of transmission, but this signal component has a low output impedance of the buffer amplifier 10b of the first switching unit 10. The transmission signal is not affected.

Here, the amplifier 6 connected to the output terminal of the filter circuit 3 may be configured by an amplification circuit capable of adjusting the gain, and the gain may be adjusted by a switching signal output from the control unit 9 (see FIG. 3). . For example, when the switching signal is not output (when switched to the reception path), the gain of the amplifier 6 is set to a relatively high value, and when the switching signal is output (switched to the transmission path) The gain of the amplifier 6 may be set to a relatively low value. By adopting such a configuration, it is not necessary to provide separate amplifiers for the transmission path and the reception path, respectively, so that the circuit scale can be further reduced (Embodiment 3).
In the present embodiment, as shown in FIG. 4, the amplifier 6 connected to the output terminal of the filter circuit 3 is configured by an amplifier circuit capable of adjusting the gain, and the gain of the amplifier 6 is adjusted under the control of the control unit 9. There are features, and other configurations are the same as those in the second embodiment. Therefore, the same components as those in the second embodiment are denoted by the same reference numerals and description thereof is omitted.

  The control unit 9 calculates the signal power of the digital reception signal input from the A / D conversion unit 4 to the demodulation unit 5, and controls the gain so that the signal level of the reception signal becomes a desired value according to the calculation result. A signal is output to the amplifier 6 to adjust the gain of the amplifier 6. For example, when 2-bit data is transmitted as the gain control signal, the gain of the amplifier 6 can be adjusted in four steps (G1 <G2 <G3 <G4) from the smallest value G1 to the largest value G4. Here, in the amplifier 6, when the gain control signal is not input, the gain is set to the initial value (minimum value G1). The control unit 9 calculates the signal power of the reception signal at the beginning of switching to the reception path, compares the calculated value with a predetermined reference value, and reduces the difference between the two (G1 or G2 or G3 or G4). A gain control signal for setting is output to the amplifier 6. As a result, the signal power of the reception signal input to the demodulator 5 can always be adjusted to a substantially constant level, and the reception sensitivity can be improved. If the minimum gain value G1 is set to a value sufficient to set the signal level of the transmission signal to a desired value, the transmission signal is not output from the control unit 9 when switching to the transmission path. Gain adjustment is possible.

(Embodiment 4)
In the present embodiment, as shown in FIG. 5, the second switching unit 11 is configured only by the buffer amplifier 11a whose input terminal is connected to the output terminal of the amplifier 6 and whose output terminal is connected to the transmission line Ls. The other features are the same as those in the second embodiment. Therefore, the same components as those in the second embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 5, the output terminal of the amplifier 6 is directly connected to the input terminal of the A / D converter 4 so that a path from the output terminal of the filter circuit 3 to the A / D converter 4 is always formed. . Since no signal is fed back from the demodulator 5 to the modulator 1 in the integrated circuit IC, inconvenience occurs even if the path from the output end of the filter circuit 3 to the A / D converter 4 is always formed in this way. Absent. However, instead of directly connecting the output terminal of the amplifier 6 to the input terminal of the A / D converter 4, the input terminal is connected to the output terminal of the amplifier 6 and the output terminal is connected to the input terminal of the A / D converter 4. The connected buffer amplifier (corresponding to the buffer amplifier 11b in the second embodiment) may be always in an operating state.

  Thus, in the configuration of the second embodiment, noise is generated when the operation state of the buffer amplifier 11 b constituting the second switching unit 11 is switched, and the noise is demodulated via the A / D conversion unit 4. However, in this embodiment, a path from the output end of the filter circuit 3 to the A / D converter 4 is always present. Since it is formed, it is possible to reduce noise input to the demodulator 5 when the path is switched. In addition, if the filter circuit 3 has a filter characteristic that can remove noise caused by the path switching, noise input to the demodulator 5 can be further reduced.

(Embodiment 5)
The present embodiment is characterized in a method in which the control unit 9 controls the first switching unit 10 and the second switching unit 11, and the other configuration is common to the second embodiment. Therefore, the same components as those in the second embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 6A, the control unit 9 individually generates a first switching signal for switching control of the first switching unit 10 and a second switching signal for switching control of the second switching unit 11. It is configured to output. In the first switching unit 10, when the first switching signal is not output from the control unit 9, the buffer amplifier 10a is turned on, the buffer amplifier 10b is turned off, and the first switching signal is output from the control unit 9. The buffer amplifier 10a is turned off and the buffer amplifier 10b is turned on. Further, in the second switching section 11, when the first switching signal is not output from the control section 9, the buffer amplifier 11a is turned off and the buffer amplifier 11b is turned on. When the second switching signal is output from the control section 9, the buffer switching is performed. The amplifier 11a is turned on and the buffer amplifier 11b is turned off. Therefore, as shown in FIG. 6 (b), when the first switching signal is output from the control unit 9 and the second switching signal is not output, the transmission path is switched, and the second switching signal is output from the control unit 9. If the first switching signal is not output, the receiving path is switched.

  Here, in the second embodiment, a closed loop may be formed through the filter circuit 3 and the amplifier 6 when switching between the transmission path and the reception path. Therefore, in the present embodiment, as shown in FIG. 6B, when the transmission path and the reception path are switched, a period (dead time) DT in which the control unit 9 outputs neither the first switching signal nor the second switching signal is provided. I am doing so. In the dead time DT, since the buffer amplifier 10b of the first switching unit 10 and the buffer amplifier 11a of the second switching unit 11 are both turned off, a closed loop is established via the filter circuit 3 and the amplifier 6 as described above. It is possible to prevent the formation and stable communication is possible.

(A) is a circuit block diagram showing Embodiment 1 of the present invention, (b) is a time chart for explaining the operation. (A) is a circuit block diagram which shows Embodiment 2 of this invention, (b) is a time chart for operation | movement description. It is another circuit block diagram same as the above. It is a circuit block diagram which shows Embodiment 3 of this invention. It is a circuit block diagram which shows Embodiment 4 of this invention. (A) is a circuit block diagram which shows Embodiment 5 of this invention, (b) is a time chart for operation | movement description. It is a circuit block diagram which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Modulation part 2 D / A conversion part 3 Filter circuit 4 A / D conversion part 5 Demodulation part 7 1st switching part 8 2nd switching part 9 Control part

Claims (5)

A modulation unit that digitally modulates transmission data, a D / A conversion unit that converts a digital transmission signal modulated by the modulation unit into an analog transmission signal, a filter circuit that removes high-frequency components included in the analog signal, An A / D converter that converts an analog received signal received via the transmission path into a digital received signal, a demodulator that demodulates received data from the digital received signal converted by the A / D converter, and D A transmission path for transmitting an analog transmission signal from the / A converter to the transmission path via the filter circuit, and a reception path for inputting the analog reception signal received from the transmission path to the A / D conversion section via the filter circuit and a reception path switching means for switching alternatively, transceiver path switching means, the analog output from the filter circuit with a gain corresponding to the path of the transmission path or the receive path Communication apparatus characterized by comprising a variable gain amplifier which amplifies an issue.   The transmission / reception path switching means has a pair of amplifiers provided on the input side and output side of the filter circuit in the transmission path, and a pair of amplifiers provided on the input side and output side of the filter circuit in the reception path. 2. The communication apparatus according to claim 1, wherein the transmission path and the reception path are selectively switched by performing on / off control of the operation of each pair of amplifiers. The transmission / reception path switching means sets a gain corresponding to the signal level of the received signal in the amplifier when switching to the reception path, and sets a predetermined gain in the amplifier when switching to the transmission path. The communication device according to claim 1 or 2. The communication apparatus according to any one of claims 1 to 3, wherein the transmission / reception path switching means always forms a path from the output end of the filter circuit to the A / D converter . 5. The transmission / reception path switching means switches to a transmission path or a reception path via a state in which no path is formed when switching between a transmission path and a reception path. Communication equipment .

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