JP3222011B2 - TDD communication equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a time-division bidirectional (TD)
D) The present invention relates to a communication device of a communication system, and particularly to a communication device having an antenna switching unit for connecting or disconnecting an antenna to or from a receiving unit.

[0002]

2. Description of the Related Art In mobile radio communication, TDMA-TDD is used.
Communication systems have been put into practical use. First, the TDMA communication system is a time division multiple access communication system in which one set of frequency is used by a plurality of users by dividing time. The TDD communication system is a time-division two-way communication system in which transmission and reception are temporally switched and alternately performed at the same frequency. Hereinafter, the 4TDMA-TDD communication system in which the number of multiplexing is set to 4 will be described in more detail.

In the 4TDMA-TDD communication system, as shown by A in FIG. 5, a predetermined time is one frame, and one frame is composed of eight time slots (hereinafter, referred to as slots).
Is divided into These eight slots are designated T1 through T
4 and four reception slots R1 to R4, and the transmission slot T1 and the reception slot R1 are divided.
Are used as a set. That is, for one set of users, 1 /
The transmission time is only 8 frames, and the reception time is 1/8 frame.

FIG. 2 shows a general circuit configuration of a conventional TDD communication device. Referring to FIG. 2, a TDD communication device will be described. Reference numeral 2 denotes a transmitting unit, 3 denotes a receiving unit, and 4 denotes a local unit. The oscillating unit, 5 is an audio unit and a control unit, and 6 is an antenna switching unit.

[0005] In the transmitting section 2, 11 is a QPSK modulator,
12 is a mixer, 13 is a transmission filter, 14 is a power amplifier, and 15 is a transmission on / off circuit. In the receiving unit 3, 16 is an RF amplifier, 17 is a band filter, 18 is a first mixer, 19 is a first IF filter, 20 is a second mixer, 2
1 is a second IF filter, 22 is an IF amplifier, and 23 is a reception on / off circuit. 2 in the audio unit and the control unit 5
4 is an audio circuit, 25 is an AD converter, and 26 is control means provided with a microcomputer. In addition to the above configuration, a handset (not shown) is connected to the audio circuit 24.

In the local oscillator 4, reference numeral 27 denotes a first local oscillator, reference numeral 28 denotes a second local oscillator, and reference numerals 29 to 32 denote OSC amplifiers, respectively, and a local oscillation wave oscillated by the first local oscillator 27 or the second local oscillator 28. To amplify. 33
And 34 are PLLs for controlling the frequency of the local oscillation wave oscillated by the first local oscillator 27 or the second local oscillator 28.

In the antenna switching section 6, reference numeral 8 denotes an antenna switch, and reference numeral 10 denotes a switching control circuit. Reference numeral 41 denotes an antenna connection end; 43 to 45, output ends from the control means 26; 43, a transmission control end for outputting a transmission control signal;
44 is a data output terminal, 45 is a reception control terminal for outputting a reception control signal, 46 and 47 are signal output terminals for outputting I and Q signals from the audio circuit 24, and 48 is an IF signal output terminal of the IF amplifier 22. , 49 are RSSI signal output terminals.

The operation of the communication device will be briefly described below with reference to FIG. In FIG. 5, A is a transmission slot T
1 to T4 and reception slots R1 to R4
Indicates a transmission control signal and C indicates a reception control signal in time series.

First, in the transmission slot T1, a transmission control signal consisting of a low level voltage is supplied from the transmission control terminal 43 of the control means 26 to the transmission on / off circuit 15 and the switching control circuit 10. The power amplifier 14 is turned on by the transmission on / off circuit 15, and the switching control circuit 10 is turned on.
The antenna switch 8 is controlled by this, and the antenna connection terminal 41 is alternatively connected to the output terminal of the power amplifier 14.
A reception control signal consisting of a high-level voltage is supplied from the reception control end 45 of the control means 26 to the reception on / off circuit 23, and the RF amplifier 16 and the IF amplifier 22 are stopped by the reception on / off circuit 23. The configurations and operations of the switching control circuit 10 and the antenna switch 8 will be described later in detail.

At this time, the voice and data are digitized.
The I signal and the Q signal of the phase and phase modulation signal are
Modulator 11 through the signal output terminals 46 and 47
, And the 240 MHz oscillation wave from the second local oscillator 28 is converted by the QPSK modulator 11 into a transmission IF signal subjected to four-phase modulation. The transmission IF signal is, for example, 166
The frequency is mixed with the oscillating wave of 0 MHz and converted to a transmission wave of 1900 MHz. An unnecessary frequency component is removed from the transmission wave by the band filter 13, the power is amplified by the power amplifier 14, and is output from the antenna connection end 41 to the antenna via the antenna switch 8.

On the other hand, in the receiving slot R1, a transmission control signal consisting of a high-level voltage is supplied from the transmission control terminal 43 of the control means 26 to the transmission on / off circuit 15 and the switching control circuit 10. Then, the power amplifier 14 is stopped by the transmission ON / OFF circuit 15, and the switching control circuit 10
The antenna switch 8 is controlled by the control signal, and the antenna connection terminal 41 is alternatively connected to the input terminal of the RF amplifier 16.
A reception control signal consisting of a low-level voltage is supplied from the reception control terminal 45 of the control means 26 to the reception on / off circuit 23, and the RF amplifier 16 and the IF amplifier 22 are operated by the reception on / off circuit 23.

At this time, for example, a 1900 MHz antenna reception signal (hereinafter, referred to as reception signal) input from the antenna connection end 41 passes through the antenna switch 8 and is converted into a reception unit input signal (hereinafter, referred to as input signal) by the RF amplifier 16. The signal is amplified by the bandpass filter 17, the unnecessary wave is removed by the bandpass filter 17, and the frequency is mixed with the 1660 MHz oscillation wave from the first local oscillator 27 in the first mixer 18,
It is converted to a first IF signal of MHz. The first IF signal is
Unwanted waves are further removed by the first IF filter 19, and the second IF signal from the second local oscillator 28 is output to the second mixer 20.
The frequency is mixed with the 9.3MHz oscillation wave and 10.7MH
z is converted into a second IF signal. The second IF signal is the second IF signal.
The desired wave is selected by the IF filter 21, amplified by the IF amplifier 22, and supplied to the audio circuit 24 from the IF signal output terminal 48.

The IF amplifier 22 is connected to the RF amplifier 16
Second IF having an intensity proportional to the intensity of the input signal input to the second IF
The signal is input, and an RSSI signal having a voltage proportional to the strength of the second IF signal is supplied from the RSSI signal output terminal 49 to the AD converter 25 and converted into a digital RSSI signal.
This digital RSSI signal is given to the control means 26 and used for various controls.

The frequency of the local oscillation wave of the first local oscillator 27 can be changed according to the communication channel, but is the same for both transmission and reception, for example, 1660 MHz. The frequency of the control means 2 is different between the transmission time and the reception time irrespective of the communication channel.
6 and the PLL 33.

Next, FIG. 4 shows an example of the antenna switching unit 6 in the conventional TDD communication apparatus, and the antenna switching unit 8 and the switching control circuit 10 will be described in detail with reference to FIG.

In the antenna switch 8, 41 is an antenna connection end connected to an antenna (not shown), 51 is a transmission end connected to the transmission unit 2, 52 is a reception end connected to the reception unit 3, and 53 is a reception end. Controlled end. A capacitor C1 having one end connected to the antenna connection end 41; a diode D1 having a cathode connected to the other end of the capacitor C1;
A capacitor C2 connecting the anode of the diode D1 to the transmitting end 51; a diode D2 having an anode connected to the other end of the capacitor C1; a capacitor C3 connecting the cathode of the diode D2 to the receiving end 52; An inverter I1 connected to the controlled end 53, a resistor R4 connecting the output side of the inverter I1 and the other end of the capacitor C1, a resistor R5 connecting the controlled end 53 and the anode of the diode D1. , And a resistor R6 connecting the controlled end 53 and the cathode of the diode D2.

In the switching control circuit 10, reference numeral 54 denotes a control input terminal, 55 denotes a power supply terminal to which power is applied, and 56 denotes a control output terminal connected to the controlled terminal 53 of the antenna switch 8. The base is connected to the control input terminal 54 via the resistor R1.
, The emitter is grounded, the collector is connected to the control output terminal 56, and the power supply terminal 5 is connected via a resistor R2.
5 is connected to the transistor TR1.

The switching control circuit 10 and the antenna switch 8 operate as follows. First, when a low-level control signal is applied to the control input terminal 54 of the switching control circuit 10, the transistor TR1 becomes non-conductive, the voltage applied to the power supply terminal 55 appears at the control output terminal 56, and the output becomes high. Become a level. Therefore, in the antenna switch 8, a high-level voltage is applied to the anode of the diode D1 and the cathode of the diode D2 by the resistors R5 and R6, respectively. The low-level voltage converted by the inverter I1 is applied to the cathode of the diode D1 and the anode of the diode D2 by the resistor R4. That is, the diode D1 is turned on when a forward bias voltage is applied, and the diode D2 is turned off when a reverse bias voltage is applied. As a result, the antenna connection end 41 and the transmission end 51 are connected by the series circuit of the capacitor C1, the diode D1, and the capacitor C2, and the antenna connection end 41 and the reception end 52 are cut off by the diode D2. That is, the diode D
1 and D2 are alternatively made conductive or non-conductive,
The transmitting end 51 and the receiving end 52 are alternatively connected to the antenna connection end 41.

Next, when a high-level control signal is applied to the control input terminal 54, the transistor TR1 is turned on, and the control output terminal 56 is grounded by the transistor TR1 to make the output low. So diode D1
Is turned off when a reverse bias voltage is applied, and the diode D2 is turned on when a forward bias voltage is applied. As a result, the antenna connection end 41 and the transmission end 51 are cut off by the diode D1, and the antenna connection end 41 and the reception end 52 are connected by a series circuit of the capacitor C1, the diode D2, and the capacitor C3.

The switching control circuit 10 and the antenna switch 8 connect the control input terminal 54 to the transmission control terminal 4 of the control means 26.
3 and the transmitting unit end 51 is connected to the power amplifier 1 of the transmitting unit 2.
4 and the receiving end 52 is connected to the RF of the receiving
The input terminal of the amplifier 16 is connected. Therefore, a low-level transmission control signal is applied to the control input terminal 54 in the transmission slot T1, the antenna and the power amplifier 14 are connected, a transmission wave is transmitted from the antenna, and a high-level transmission control signal is received in the reception slot R1. Is added,
The antenna and the RF amplifier 16 are connected, and the antenna reception signal is input to the RF amplifier 16 as an input signal.

In such an antenna switch 8, when the diodes D1 and D2 are in a non-conductive state, a small capacitance exists between the electrodes of the diodes D1 and D2. It is not completely blocked by D1 and D2, but passes through after being attenuated by about 20 dB.

[0022]

In a mobile communication, the strength of a received signal is easily spread over a wide range, and when a received signal having an excessive strength is input to the receiving unit 3 as an input signal, the receiving unit 3
, The first mixer 18 and the second mixer 20 are saturated. When they saturate, their input / output impedance changes from the value at the time of non-saturation input.

In particular, when the input / output impedance of the first mixer 18 and the second mixer 20 changes, the first IF filter 1
9, the terminating impedance condition of the second IF filter 21 changes, and the first IF filter 19 and the second IF filter 21
And the group delay characteristics change within the passband of the above. This change causes a change in the phase of the signal in the limiter amplifier or demodulator provided in the audio circuit 24, the signal is not correctly demodulated, and a bit error occurs in the demodulated signal.

In order to reduce this bit error, RF
The AGC control of the amplifier 16 or the provision of an attenuator at the input terminal of the RF amplifier 16 controls the intensity of the input signal input to the receiver 3 within a predetermined range. However, when such circuits are provided, there is a problem that not only the circuit scale becomes large and the manufacturing cost increases, but also that the communication device becomes heavy and the portability deteriorates.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a TDD communication device which solves the problem caused by excessive input with a simple circuit whose circuit scale does not increase.

[0026]

To achieve the above object, according to an aspect of, TDD scheme communication apparatus according to claim 1, as one connection state either of the transmitter or receiver antennas, other
How and the antenna switch to a non-connected state, and control means for controlling the switching state of the antenna switch, upon receipt
An input signal strength detecting means for outputting an input signal intensity proportional to the intensity of the receiver input signal input to the receiving unit, the input signal intensity than the first predetermined value and said first predetermined value
And comparison means for comparing also the lower second predetermined value, the
The antenna switching device includes at least the antenna and the receiving unit.
Having a diode interposed in series between
The arm can be switched between conducting and non-conducting states.
The antenna and the receiver are connected to each other
State or the non-connection state, and the control means turns off the diode when receiving and the input signal strength is equal to or higher than the first predetermined value and when transmitting.
And the diode is in a non-conducting state during reception.
And the input signal strength is equal to or less than the second predetermined value.
When the control means turns on the diode.
The difference between the first predetermined value and the second predetermined value.
During reception and when the diode is conducting.
The input signal when in a non-conductive state with the input signal strength of
It was set larger than the difference from the signal strength.

A TDD communication apparatus according to claim 2.
Converts the second predetermined value to an input signal required for the receiving unit.
The lower limit of intensity was set.

[0028]

[0029]

In the case where the input signal strength of the receiving section is larger than the first predetermined value, the antenna switch of the antenna switch is not used even during reception.
Is turned off. At this time, between the electrodes of the diode
Since very small capacitance is present, the antenna switch acts as a high-frequency attenuator, antenna reception signals are input to the receiving unit as the receiving unit input signal attenuated by the antenna switch. In this state, if the input signal strength is less than the second predetermined value, the diode is turned on.
The antenna reception signal is input to the receiver as an unattenuated receiver input signal.

[0030]

FIG. 1 is a circuit diagram showing an embodiment of a TDD communication apparatus according to the present invention. The TDD communication apparatus according to the present invention will be described below with reference to FIG.

The TD according to the embodiment of the present invention shown in FIG.
In the D system communication device, a configuration different from the conventional TDD system communication device shown in FIG. 2 is provided with a switching control circuit 9 instead of the switching control circuit 10, an attenuation control terminal 42 provided in the control means 26, and a control means 26. Thus, the switching control circuit 9 is provided with an attenuation instruction signal. That is, the switching control circuit 9
Is supplied with a transmission control signal and an attenuation instruction signal from the control means 26. The other configuration is the same as the configuration of the conventional communication device shown in FIG. 2, and the same reference numerals are given and the detailed description is omitted.

In FIG. 1, the IF amplifier 22 converts an RSSI signal having a voltage proportional to the intensity of a receiver input signal (hereinafter, referred to as an input signal) input to the RF amplifier 16 into a reception slot R1 (see FIG. 5). Output. RSSI
The signal is converted into a digital RSSI signal by the AD converter 25 and supplied to the control means 26. The control means 26 also has a function of a comparison means for comparing the magnitude of the input signal intensity represented by the digital RSSI signal with first and second predetermined values set in advance. Outputs a value attenuation instruction signal. The attenuation instruction signal is at a high level when the input signal strength is larger than a first predetermined value, and is at a low level when the input signal strength is smaller than a second predetermined value.

FIG. 3 shows an antenna switch 8 and a switch control circuit 9.
It is. In FIG. 3, the antenna switching device 8
Since the configuration and the operation are the same as those of the antenna switching device 8 described with reference to FIG.

In the switching control circuit 9, 54 is a control input terminal, 55 is a power supply terminal to which power is applied, 56 is a control output terminal connected to the controlled terminal 53 of the antenna switch 8, and 57 is an attenuation control input terminal. . A transistor TR1 having a base connected to the control input terminal 54 via the resistor R1, an emitter grounded, a collector connected to the control output terminal 56, and connected to the power supply terminal 55 via the resistor R2;
The base is connected to the attenuation control input terminal 57 via the resistor R3, the emitter is grounded, and the collector is the transistor T3.
It has a transistor TR2 connected to the base of R1.

The switching control circuit 9 operates as follows.

First, when a low-level control signal is applied to the control input terminal 54, regardless of the control signal applied to the attenuation control input terminal 57, the transistor TR1 is turned off, and the control output terminal is turned off. Reference numeral 56 indicates the voltage applied to the power supply terminal 55, and the output goes high.

Next, when a high-level control signal is applied to the attenuation control input terminal 57, the transistor TR2 is turned on, the base of the transistor TR1 is grounded by the transistor TR2, and applied to the control input terminal 54. Regardless of the control signal, the transistor TR1 becomes non-conductive, the voltage applied to the power supply terminal 55 appears at the control output terminal 56, and the output goes high.

When a low-level control signal is applied to the attenuation control input terminal 57 and a high-level control signal is applied to the control input terminal 54, the transistor TR2 is turned off and the transistor TR1 is turned on. , And the control output terminal 56 is grounded by the transistor TR1, and the output becomes low level.

In summary, a low-level control signal is applied to the control input terminal 54 or the attenuation control input terminal 57
When a high level control signal is applied to the
6 is at a high level, and the antenna switch 8 connects the antenna connection end 41 to the transmission unit end 51.

The output of the control output terminal 56 is low only when a high-level control signal is applied to the control input terminal 54 and a low-level control signal is applied to the attenuation control input terminal 57. In the switch 8, the antenna connection end 41 and the reception end 52 are connected.

The switching control circuit 9 and the antenna switching unit 8 have a control input terminal 54 connected to the transmission control terminal 43 of the control unit 26.
, The attenuation control input terminal 57 is connected to the attenuation control terminal 42 of the control means 26, the transmission unit terminal 51 is connected to the output terminal of the power amplifier 14 of the transmission unit 2, and the reception unit terminal 52 is connected to the reception unit 3. It is connected to the input terminal of the RF amplifier 16.

Accordingly, in the transmission slot T1 in which the low-level transmission control signal is applied to the control input terminal 54, the antenna and the power amplifier 14 are connected, and the transmission wave is transmitted from the antenna. In the reception slot R1 to which the transmission control signal is given, the attenuation instruction signal applied to the attenuation control input terminal 57 causes
The connection state between the antenna and the RF amplifier 16 is different.

In FIG. 5, B indicates a transmission control signal, D indicates an attenuation instruction signal, and E indicates a connection state of the antenna switch 8 in time series. The transmission control signal B is at a low level in each transmission slot T1, and is at a high level in the other slots. The attenuation instruction signal D is at the low level in the first reception slot R1. At this time, if the control means 26 also serving as the comparison means determines that the reception intensity is larger than the first predetermined value, the next determination is made. It changes to the high level in the reception slot R1. The antenna is switched by the antenna switch 8 to the transmitting section 2 in the first transmitting slot T1, to the receiving section 3 in the first receiving slot R1, to the next transmitting slot T1.
Is connected to the transmission unit 2 in the next reception slot R1.

As described above, in the antenna switch 8, when the diodes D1 and D2 are in a non-conductive state, a small capacitance exists between the electrodes of the diodes D1 and D2. , The received signal is not completely blocked by the diodes D1 and D2,
Passes after being attenuated by dB. In other words, the antenna switch 8 in which the connection between the antenna connection end 41 and the reception unit end 52 is in a cut-off state is provided between the antenna and the RF amplifier 16.
It works as a high-frequency attenuator with an attenuation of 20 dB.

FIG. 6 shows the strength of the received signal received by the antenna (hereinafter referred to as the received signal strength) and the strength (hereinafter referred to as RSSI) represented by the RSSI signal output from the IF amplifier 22.
This is a graph showing the relationship between the received signal strength and the received signal strength, and the vertical axis is the RSSI strength. And R
In the SSI intensity, a is a first predetermined value, and b is a second predetermined value. Next, referring to FIG. 6, the received signal strength and RSS
A description will be given of the relationship between the I intensities and the setting of the predetermined values a and b serving as references for the control means 26 to compare and determine the RSSI intensity.

In the range where the received signal strength is B or less,
The received signal strength and the RSSI strength are linearly related, and R
The SSI strength is equal to or less than the first predetermined value a, and the antenna switch 8 is connected on the receiving unit 3 side. The first predetermined value a is set to the RSSI strength corresponding to the vicinity of the upper limit of the input signal strength allowed for the receiving unit 3.

When the received signal strength exceeds B in the relation of the straight line A, the RSSI strength also exceeds the first predetermined value a, and the receiving section 3 of the antenna switch 8 is disconnected. Then, the received signal is attenuated by about 20 dB by the antenna switch 8 and input to the receiving unit 3, and the RSSI strength is about 20 dB
B decreases. That is, the received signal strength and the RSSI strength change to a linear relationship.

In the relationship of the straight line b, the predetermined value is the second
Is changed to the predetermined value b. The second predetermined value b is smaller than the first predetermined value a by about 20 dB, which is the amount of attenuation of the antenna switch 8 acting as a high-frequency attenuator. The RSSI intensity is set to correspond to the lower limit of the intensity. When the received signal strength becomes equal to or less than A in the relationship of the straight line b, the RSSI strength also becomes the second
Is not more than the predetermined value b, and the receiving section 3 side of the antenna switch 8 is in the connected state. That is, received signal strength and RSSI
The intensity changes to a straight line.

To summarize the above, the received signal strength and RSS
When the received signal strength is A or less, the I strength has a relationship of a straight line A. When the received signal strength is between A and B, the I strength has a relationship of a straight line A or a straight line B. In the case, there is a relationship of a straight line b. When the relationship is a straight line a, the upper limit of the RSSI intensity is monitored by the first predetermined value a, and when the relationship is a straight line b, the lower limit of the RSSI intensity is monitored by the second predetermined value b.

In this way, even if the intensity of the received signal received by the antenna extends over a wide range, the signal is attenuated by about 20 dB at least in a range exceeding B, and is input to the receiving unit 3. The range of the input signal strength input to the receiver 3 is reduced by about 20 dB. Also receive
If the signal strength is less than A, this attenuation is eliminated.

[0051]

As described above, according to the present invention, the T
According to DD scheme communicator, when an excessive antenna reception signal has been received at the time of reception, it is possible to function the A <br/> antenna switch diode as a non-conducting state as a high-frequency attenuator, antenna reception signals Is attenuated and input to the receiving unit, which can prevent the RF amplifier and the mixer from being saturated, and the demodulator can correctly demodulate the signal without any change in the filter amplitude and group delay characteristics due to the saturation phenomenon. . When the diode is off,
If the tenor reception signal goes low, the diode becomes conductive.
The antenna switch does not function as a high frequency attenuator
The antenna reception signal enters the receiver without being attenuated.
And the receiving sensitivity does not decrease.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a TDD communication apparatus according to the present invention.

FIG. 2 is a circuit configuration diagram of a conventional TDD communication device.

FIG. 3 is a circuit diagram of an antenna switching unit in one embodiment of the TDD communication apparatus according to the present invention.

FIG. 4 is a circuit diagram of an antenna switching unit in a conventional TDD communication device.

FIG. 5 is a diagram showing various signals in time series.

FIG. 6 is a diagram showing a relationship between the strength of an antenna reception signal and the strength of an RSSI signal in the TDD communication apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna switching part 2 Transmission part 3 Receiving part 8 Antenna switching part 9 Switching control circuit 22 IF amplifier (input signal strength detection means) 26 Control means (comparative means) 41 Antenna connection end 42 Attenuation control end 43 Transmission control end 49 RSSI Signal output terminal

Claims (2)

(57) [Claims] [Claim 1] as one connection state either of the transmitter or receiver antennas, the other and the antenna switch to a non-connected state, and control means for controlling the switching state of the antenna switch, said at reception Input signal strength detection means for outputting an input signal strength proportional to the strength of the receiving section input signal input to the receiving section, and setting the input signal strength to a first predetermined value
And a comparing means for comparing with a second predetermined value lower than the first predetermined value , wherein the antenna switch is at least
A serially inserted antenna between the antenna and the receiving unit
The diode is conducting or not conducting
The antenna and the front
The receiving unit switches between connected and disconnected states
The diode is turned off by the control means at the time of reception, when the input signal strength is equal to or more than the first predetermined value, and at the time of transmission.
The diode is turned off and the input signal strength is reduced
When the value is equal to or less than the second predetermined value, the control unit controls
To bring the diode into a conducting state, and
The difference from the second predetermined value at the time of reception and the
The input signal strength and the non-conductive state when the
Greater than the difference from the input signal strength when the
TDD scheme communication device, characterized in that the. 2. The method according to claim 1, wherein the second predetermined value is required for the receiving unit.
The input signal strength is set at the lower limit.
Item 2. The TDD communication device according to Item 1.