JP3432262B2 - Wireless telephone equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio telephone, and more particularly to a reduction in gain at a strong reception input level and a reduction in power consumption. 2. Description of the Related Art In a portable communication device such as a cordless telephone or a portable telephone, when the transmission side and the reception side are close to each other, there is a case where a problem that the transmission or reception level is too strong may be a problem. In the case of digital communication, if the reception level is too high on the receiving side, a saturation distortion occurs in the receiving circuit, inter-symbol interference increases, and a bit error rate increases. In order to prevent this, in the conventional apparatus, an attenuator circuit for attenuating the transmission level or the reception level is provided on the transmission side or the reception side, and the attenuator circuit is selected according to the signal level. For example, FIG. 16 is a block diagram of a front end portion of a receiving circuit of a digital radio telephone of a linear modulation system. The function will be described with reference to FIG. [0005] Radio frequency (RF:
The Radio Frequency signal is amplified by a low noise amplifier (LNA) 81, and when the reception level is large, is attenuated by a radio frequency attenuator (RF-ATT) 86 and unnecessary out of band by a radio frequency (RF) filter 82. After the frequency component is removed, the first mixer (1st Mix)
At 83, the signal is mixed with the primary local signal supplied from the synthesizer and converted to a primary intermediate frequency (1st IF) signal. The primary intermediate frequency signal is a primary intermediate frequency filter 8
At 4, the signal in the selected band is removed and output to the intermediate frequency section. In this circuit, a radio frequency attenuator 86 is provided at the output of the low noise amplifier 81, and when the reception level is strong, the signal is attenuated by the attenuator 86 to prevent saturation in the first mixer 83. However, in this method, even when the signal level is low and the radio frequency attenuator 86 is turned off, there is an insertion loss at the insertion portion of the radio frequency attenuator 86, which is a factor of deteriorating the noise figure of the entire receiver. In addition, the presence of the radio frequency attenuator 86 increases the number of components, which causes a problem of increased cost, reduced reliability, increased circuit space and weight, and increased power consumption. To solve this problem, as shown in FIG. 17, there is a method of controlling the gain by lowering the level of the primary local signal supplied from the synthesizer unit. However, the output saturation level of the first mixer 83 is reduced. As a result, a phenomenon occurs in which the dynamic range is narrowed and the output level is reduced, but the output level is saturated. FIG. 18 is a block diagram of a transmission circuit of a digital radio telephone in a linear modulation system. In the transmission circuit of the radio device of the digital linear modulation system, the output amplifier 93 is a linear (class A) amplifier of GaAs because of the necessity of linear operation.
A circuit using an FET is used. FIG. 19 shows the output of each block of the transmission circuit when the transmission output level is reduced by −N dB from the rating. Focusing on the current consumption at this time, the transmission output level is controlled to reduce the transmission output level by more than -Nd.
Even when B decreases, each circuit element operates with the same current consumption as in the case of full power output without performing transmission output reduction control. In particular, the current consumption of the output amplifier 93 that consumes the most power does not change. For this reason, a wireless telephone such as a mobile telephone that operates using a battery as a power source has a problem that current consumption is increased and battery life is shortened. FIG. 20 shows a TDMA-TDD (Time D
vision MultipleAccess-Ti
FIG. 2 is a block diagram of a cordless telephone device based on a “me Division Duplex: time division multiple access—time division two-way communication” method. This circuit also has an attenuator 123 on the transmission side for transmission power control. Also T
Transmitting circuit 121 for DMA-TDD system
Transmission / reception switching circuit 1 for switching to and receiving circuit 120
08 is provided. In a cordless telephone device or the like, particularly in a portable device or a child device, an increase in the number of components is not preferable because it causes an increase in cost, a decrease in reliability, an increase in power consumption, an increase in weight, and the like. As described above, in a conventional radio telephone such as a cordless telephone or a portable telephone, in order to prevent an increase in intersymbol interference due to saturation distortion when the reception level is too high. Means such as providing an attenuator circuit on the transmission side or the reception side have been used to suppress the reception level. Providing such a circuit which is not necessary at a normal reception level results in an increase in the number of parts, resulting in an increase in cost, a decrease in reliability, an increase in weight, and the like. In such a case, the current consumption did not decrease, and in many cases, it was not preferable as a portable communication device. It is an object of the present invention to solve the above problem and to provide a radio telephone apparatus which can control a transmission level without increasing the number of parts and can prevent an increase in intersymbol interference. The present invention comprises an antenna,
In a wireless telephone apparatus having a transmitting circuit, a receiving circuit, a receiving input level detecting means for detecting a receiving input level, and a transmission / reception switch for connecting the antenna to the transmitting circuit or the receiving circuit, the receiving input level detecting means When the transmission / reception switch determines that the reception input level is higher than a certain value, the transmission / reception switch includes connection control means for connecting the antenna and the reception circuit during transmission. According to the present invention, when the reception input level is higher than a certain value, even if the transmission / reception switch is transmitting, the transmission is performed with the antenna and the reception circuit connected. In this case, the transmission level is reduced without providing an attenuator circuit by utilizing signal leakage between the antenna and the transmission circuit. According to this configuration, when the reception input level is higher than a certain value, the transmission level can be reduced to reduce the intersymbol interference, and the omission of the attenuator circuit can reduce the number of parts, reduce the cost, and increase the reliability. Thus, the circuit space and weight can be reduced, and portability can be improved. Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a reception front-end circuit of a radio telephone according to an embodiment of the first invention. In the figure, 1 is a variable gain amplifier, 2 is a radio frequency filter, 3 is the first
Mixer, 4 is an intermediate frequency filter, 5 is a local oscillation frequency filter, and 6 is an RSSI (Re
ceive Signal Strength Ind
i.c.) A level detection unit, 7 is an attenuation selection determination unit in the control unit, and 8 is an attenuation selection switch. FIG. 2 is an operation flowchart of the circuit shown in the block diagram of FIG. The signal received from the antenna is frequency-converted, and a DC signal corresponding to the level detected by the RSSI level detector 6 is sent to the controller.
The RSSI output has a correlation with the received signal level, and the attenuation selection determining unit 7 in the control unit determines whether the gain is reduced or not based on the DC signal. The attenuation selection switch 8 controls the gain of the variable gain amplifier 1. FIG. 3 is a circuit diagram of one embodiment of the variable gain amplifier 1 used in the embodiment shown in FIG. This circuit is a typical grounded emitter current feedback type bias circuit. In the figure, 9 and 10 are input / output DCs.
Coupling capacitors for cutting, 11 and 12 are base bias resistors, 13 is an emitter resistor, 14 is a damping inductor, 15 and 16 are bypass capacitors, 17 is a base bias variable resistor, 18 is a variable resistor short-circuit switch, and 19 is an amplifying transistor. Where A is the base input and B is
Indicates the collector output. In this circuit, the variable resistance short-circuit switch 18
Control the gain by shorting or releasing the base bias variable resistor 17. Normally, variable resistance short-circuit switch 1
8 is turned on, the base bias variable resistor 17 is short-circuited, and the power supply voltage Vcc is directly applied to the base bias resistor 11. When the RSSI level detector 6 detects that the received signal level is high, and the radio frequency attenuation control signal from the attenuation selection determiner 7 turns off the variable resistance short-circuit switch 18, the base between the power supply voltage Vcc and the base bias resistor 11 is turned off. When the bias variable resistor 17 is inserted, the division ratio of the resistors 11, 12, and 17 that give the base bias voltage changes, the base bias voltage decreases, and the potential of the base input decreases, so that the potential of the collector output also decreases. , The collector current also decreases, and the gain decreases. FIG. 4 shows a circuit diagram of another embodiment of the variable gain amplifier 1 of the present invention. This circuit controls the gain by using the switching operation of a transistor. In the figure, 20 and 22 are switching transistors, and 21 and 23 are base input resistors. At a normal reception signal level, the radio frequency attenuation control signal (“H”) from the attenuation selection determining unit 7 is input to the switching transistor 22 through the base input resistor 23, and when the switching transistor 22 is turned on, the switching transistor 20 is also turned on, and the base bias variable resistor 17 is short-circuited. When the received signal level becomes strong, the radio frequency attenuation control signal becomes 0V ("L") voltage, the switching transistors 20 and 22 are turned off, and the power supply voltage Vcc
A base bias variable resistor 17 is inserted between the base bias resistor 11 and the base bias resistor 11. As a result, the gain decreases as in the example of FIG. FIG. 5 is a graph showing the input / output characteristics of the variable gain amplifier 1 in the examples shown in FIGS. From this, it can be seen that when the base bias variable resistor 17 is inserted by the switch operation and the gain is reduced, the amplifier is not saturated over a wider range of the input signal level, and the linearity is maintained. FIG. 6 shows still another embodiment of the variable gain amplifier 1 of the present invention. In this example, according to the received signal level, 2
By outputting the different types of base bias control signals C and D from the attenuation selection judging unit 7, the gain of the variable gain amplifier 1 can be changed in multiple stages, and the gain control can be performed widely. FIG. 7 is a block diagram of a transmission circuit of a radio telephone according to an embodiment of the second invention. In FIG. 7, 41 is an attenuator, 42 is an up-converter mixer, 43 is an output amplifier, 44 is a bandpass filter, 45 is an antenna,
Reference numeral 6 denotes a switching circuit. Before describing this circuit, the output amplifier 43
The operation of the amplifier using the gallium arsenide FET used in the above will be described. FIG. 8 shows the relationship between the gate bias voltage Vg and the amplifier gain of the output amplifier 43 using a gallium arsenide FET. As can be seen from the figure, even if the gate bias voltage is changed from Vg1 to Vg2, there is no significant change in the gain of the amplifier at the small signal level. On the other hand, the relationship between the gate bias voltage Vg and the drain current of the output amplifier 3 is as shown in FIG. 9, which greatly changes by changing the gate bias voltage from Vg1 to Vg2. In order to operate the gallium arsenide FET stably with respect to a normal input and obtain the maximum transmission output, a voltage of Vg1 is required as a gate bias voltage, and therefore, a drain current is also required of Id1. However, when the transmission output is controlled, the output of the wireless device is reduced to −Ndb, so that if the gain of the amplifier is obtained, the gate bias voltage is set to Vg2.
Thus, the drain current can be reduced to Id2. By utilizing the characteristics of the amplifier using such a gallium arsenide FET, a transmission circuit of a radio is constructed as shown in FIG. When the transmission output is controlled by turning on the attenuator 41, the gate bias voltage Vg of the output amplifier 43 is switched by the switching circuit 46 from Vg1 to Vg2 using this control signal. As a result, the transmission output becomes -NdB, and the drain current of the output amplifier 43 decreases from Id1 to Id2. Therefore, the output amplifier 4
3 can be reduced without changing the gain. FIG. 10 shows a modification of the second embodiment of the present invention, in which the output amplifier 3 is connected to a MIC (Microwave).
The integrated circuit has an integrated circuit and includes an attenuator circuit and a gate bias voltage switching circuit. FIG. 11 shows a specific circuit of the output amplifier MIC43. By constructing the dedicated MIC in this way, the configuration of the transmission circuit can be made smaller and simpler. FIG. 12 is a circuit diagram showing a third embodiment of the present invention. This is a circuit of a cordless telephone according to the TDMA-TDD system. The basic operation of this circuit will be described. On the transmitting side, the audio signal input from the microphone 51 is
After being converted into digital data by the voice encoder 52 and temporally compressed by the burst data generator 53, the data is converted into burst data with additional bits added before and after. The digital modulator 54 generates a phase modulated wave (intermediate frequency signal) from the burst data. Further, the phase modulated wave signal is mixed with a local oscillation signal output from the frequency synthesizer 56 by an up-converter mixer 55T, converted into a transmission frequency signal, amplified to a predetermined power by a transmission power amplifier 57, and transmitted and received by a transmission / reception switch 58. Is supplied to the antenna 59 and is radiated as a burst-like phase modulated wave. On the other hand, on the receiving side, the burst phase modulated wave is received by the antenna 59, is amplified by the low noise amplifier 60 via the transmission / reception switch 58, and is input to the down converter mixer 55R. Downconverter mixer 55R
Then, this signal is mixed with a local oscillation signal output from the frequency synthesizer 56 to obtain an intermediate frequency signal. The output of the mixer 55R is amplified to a required level by an intermediate frequency amplifier 61 with an RSSI output, demodulated by phase modulation by a digital demodulator 62, frame-synchronized and bit-synchronized, and then reproduced as digital data. You. This digital data is subjected to error detection and the like in the burst data combiner 63, and is restored on the time axis to the original form, returned to the analog audio signal in the audio decoder 64, and transmitted from the speaker 65. Is output. In the case of control data instead of voice data, the data is directly input to the burst data generator 53 from the control microcomputer 66 on the transmission side. On the receiving side, the data is passed from the burst data combiner 63 directly to the control microcomputer 66. The control microcomputer 66 and control circuit 67 execute control of the entire apparatus and each block.
The input keys and the display section 68 are for the user to input and output information other than voice. The power supply circuit 69 supplies necessary power to each block. Here, the transmission / reception switch 58 will be considered.
This circuit has a switching function of connecting the antenna 59 to the transmission circuit 71 or the reception circuit 70 by a control voltage from the control circuit 67 in order to realize bidirectional communication in a time-division manner. To speed up the switching, the circuit is composed of semiconductor switches. FIG. 13 shows an embodiment of the circuit of the transmission / reception switch 58. In such a transmission / reception switch 58, assuming that the antenna 59 is now connected to the transmission circuit 71,
The connection with the receiving circuit 70 is blocked,
, The connection with the transmission circuit 71 is blocked. However, since the transmission / reception frequency is an extremely high frequency of quasi-microwave, there is a slight signal leakage even in the blocking state. By making good use of this leakage and connecting the antenna 59 to the receiving circuit 70 in the transmitting state to prevent the connection with the transmitting circuit 71, the transmission output can be reduced without providing an attenuator circuit. It can be performed. FIGS. 14A and 14B show the switching state of the transmission / reception switch 58. FIG. 14A shows the transmission state and FIG. 14B shows the reception state. The attenuation shown in the figure indicates a value that can be normally obtained when a semiconductor switch is used in the quasi-microwave band. FIG. 15 shows a case where the equalizing circuit of the transmitting section is in the transmitting state and the switching state shown in FIG.
The case (b) in the switching state of (b) is shown. RSS
RSSI output 72 from intermediate frequency amplifier 61 with I output
When the control unit 67 determines that the partner station is far away, the control unit 67 changes the switching state of FIG. 14A so that the equalizing circuit of FIG. 14A is obtained, and determines that the partner station is too close. Is (b)
The switching state of FIG. 14B is selected so that the equalizing circuit of FIG. Thus, when the switching state shown in FIG. 14B is selected, it is equivalent to the insertion of an attenuator of about 24 dB on the transmission side, and the attenuator circuit is removed without providing an attenuator circuit in the transmission circuit. An equivalent function can be realized by making only a slight change in the conventional circuit. As described above, according to the present invention,
If the reception input level detection means determines that the reception input level is higher than a certain value, the transmission / reception switch is provided with connection control means for connecting the antenna and the reception circuit during transmission. Performs transmission in a state where the antenna and the receiving circuit are connected even when the transmission / reception switch is transmitting, without using an attenuator circuit by using signal leakage between the antenna and the transmitting circuit. The transmission level is reduced. According to this configuration, when the reception input level is higher than a certain value, the transmission level is reduced to reduce the intersymbol interference without providing an attenuator circuit and without significantly changing the conventional circuit. Can be reduced. In addition, by omitting the attenuator circuit, the number of components can be reduced, cost can be reduced, reliability can be increased, circuit space and weight can be reduced, and portability can be improved. [0052]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one embodiment of a reception front-end circuit of a wireless telephone according to the first invention. FIG. 2 is an operation flowchart of the circuit of the embodiment of FIG. 1; FIG. 3 is a circuit diagram of one embodiment of a variable gain amplifier used in the reception front-end circuit of FIG. 1; FIG. 4 is a circuit diagram of another embodiment of the variable gain amplifier used in the reception front-end circuit of FIG. 1; FIG. 5 shows input / output characteristics of the variable gain amplifier shown in FIGS. 3 and 4; FIG. 6 is a circuit diagram of still another embodiment of the variable gain amplifier used in the reception front-end circuit of FIG. FIG. 7 is a block diagram of an embodiment of a transmission circuit of a wireless telephone according to the second invention. 8 is a gallium arsenide FET used in the embodiment of FIG.
Amplifier gain characteristics. FIG. 9 shows a gallium arsenide FET used in the embodiment of FIG.
Amplifier drain current characteristics. FIG. 10 is a block diagram of another embodiment of the transmission circuit of the wireless telephone according to the second invention. 11 is an output amplification MIC used in the embodiment of FIG.
FIG. FIG. 12 is a block diagram of one embodiment of a wireless telephone according to the third invention. FIG. 13 is a circuit diagram of one embodiment of a transmission / reception switch used in the embodiment of FIG. 12; FIG. 14 is a diagram showing a switching state of the transmission / reception switch of FIG. 13; FIG. 15 is an equalizing circuit of the transmitting unit in the switching state shown in FIG. 14; FIG. 16 is a block diagram of a conventional example of a reception front-end circuit of a wireless telephone. FIG. 17 is a block diagram of another conventional example of a reception front-end circuit of a wireless telephone. FIG. 18 is a block diagram of a conventional example of a transmission circuit of a wireless telephone. 19 is an output characteristic of each block of the transmission circuit shown in FIG. FIG. 20 is a block diagram of a conventional example of a cordless telephone using the TDMA-TDD method. [Description of Signs] 1 Variable gain amplifier 2, 82 Radio frequency filter 3, 83 First mixer 4, 84 Intermediate frequency filter 5, 85 Local oscillation frequency filter 6 RSSI level detection unit 7 Attenuation selection determination unit 8 Attenuation selection switch 9, 10, 24 DC cut coupling capacitors 11, 12 Base bias resistor 13 Emitter resistor 14 Damping inductor 15, 16 Bypass capacitor 17 Base bias variable resistor 18 Variable resistor short circuit switch 19, 31 Amplification transistors 20, 22, 25, 26 Switching transistors 21, 23 Base input resistors 27-30, 74, 75 Resistors 41, 91, 123 Attenuators 42, 55T, 92, 105T Upconverter mixers 43, 93 Output amplifiers 44, 94 Bandpass filters 45, 59, 95 , 09 Antenna 46 Switching circuit 51, 101 Microphone 52, 102 Speech encoder 53, 103 Burst data generator 54, 104 Digital modulator 55R, 105R Down converter mixer 56, 106 Frequency synthesizer 57, 107 Transmission power amplifier 58, 108 Transmission / reception switching Devices 60, 110 receiving amplifier 61, 111 intermediate frequency amplifier 62 with RSSI output, 112 digital demodulator 63, 113 burst data combiner 64, 114 audio decoder 65, 115 speaker 66, 116 control microcomputer 67, 117 control circuit 68, 118 Input keys and display unit 69, 119 Power supply circuit 70, 120 Receiving circuit 71, 121 Transmission circuit 72-1, 122-1 RSSI output signal 72-2, 122-2 Control signal 73 Diode 79 Equalization attenuator 81 Low noise amplifier 86 Radio frequency attenuator

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinji Honjo 3-1-1 Asahigaoka, Hino-shi, Tokyo Inside Toshiba Hino Factory (72) Inventor Tohru Mizumoto 3-1-1 Asahigaoka, Hino-shi, Tokyo Toshiba Corporation Hino Factory (56) References JP-A-5-110464 (JP, A) JP-A-5-300039 (JP, A) JP-A-5-122123 (JP, A) JP-A-6-252797 (JP, A) JP-A-57-97240 (JP, A) JP-A-5-34737 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/24-7 / 26 102 H04Q 7/00-7/38

Claims (1)

(57) [Claims] [Claim 1] An antenna, a transmitting circuit, a receiving circuit,
Reception input level detection means for detecting a reception input level;
In a wireless telephone device having a transmission / reception switch for connecting the antenna to the transmission circuit or the reception circuit, if the reception input level detection means determines that the reception input level is higher than a certain value, the transmission / reception switch transmits the signal. A wireless telephone device comprising a connection control means for connecting the antenna and the receiving circuit therein.