JPH11215037A - Bidirectional transmitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bidirectional transmitting device which enables automatic gain control of receiving signals following fading. SOLUTION: This bidirectional transmitting device consists of a base station transmitting device and a mobile station transmitting device and performs the automatic switching between the transmitting and receiving periods to carry out bidirectional transmission. Such a constitution is further provided with two types of automatic gain control circuits 9 and 16 for automatically controlling gains of receiving signals together with a function that automatically switches the circuit 9 and 16, a function given to one of both circuits 9 and 16 to automatically control gains only during the receiving period of the receiving signals, and a function that automatically switches the period, when the gains of receiving signals are automatically controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional transmission apparatus for transmitting information bidirectionally by alternately switching between transmission and reception over time using one transmission band.

[0002]

2. Description of the Related Art For terrestrial transmission of moving image signals, FPU
(Field Pick Up) communication devices (hereinafter, referred to as FPUs) are widely used. Signal transmission using mobile radio or semi-fixed radio such as FPU is a system in which a moving image signal transmitted from a mobile station in which a camera or the like is installed is received by a base station such as a broadcast center. FIG. 12 shows the block configuration of this FPU. The transmission control unit 21, the transmission high-frequency unit 22, the transmission antenna 23, and the reception antenna 2
4. A transmission system including a reception high frequency unit 25 and a reception control unit 26. Hereinafter, this operation will be described. The transmission data rate of the transmission control unit 21 is determined by the clock oscillator CK OSC
Is determined by The data input to the ID terminal of the transmission control unit 21 is digitally modulated,
Is modulated and output to an IF signal having a frequency determined by

[0003] The input transmission high frequency section 22 includes a transmission control section 21.
Is converted to a designated RF frequency and transmitted by the antenna 23. The reception high frequency unit 25
Only the RF signal of the frequency designated by the antenna 24 is received and converted to an IF signal. The reception control unit 26 demodulates the input reception IF signal according to the frequency of the local oscillator LO VCO, and then outputs a digital signal at a rate determined by the output of the clock oscillator CK OSC.

An outline of the operation at this time will be described with reference to FIGS. First, FIG. 6 will be described. The transmission signal has a frame structure, and is composed of several types of synchronization symbol groups and data symbol groups for transmitting information codes. As an example of this group of synchronization symbols, a null symbol having a signal power intensity of "0" as a first symbol, an autocorrelation function having a sharp peak value as a second symbol, and a sweep for indicating a specific time point on a time axis. There are symbols etc. As a modulation scheme of the data symbol group, a quadrature phase shift keying scheme (QPSK: Quad
rature Phase Shift Keying) and 16-level quadrature amplitude modulation (1
6QAM: 16 Quadrature Amplitude Modulation) can be used, but it is difficult to adapt to an analog AM / FM method or the like, which is a modulation method that does not include a synchronization symbol or a synchronization header.

Next, FIG. 7 will be described. A transmission signal transmitted from a mobile station is transmitted in frame units. The transmission signal Tm is a transmission signal for each frame. The transmission signal Tm transmitted from the mobile station in units of one frame is
The base station receives the received signal Rs in units of one frame. The radio wave propagation time at this time, that is, the propagation delay is
Propagation delay increases as the distance increases in proportion to the distance between the base stations. Also, the level (amplitude value) of the received signal Rs
Is also proportional to the distance between the mobile station and the base station, and the longer the distance, the greater the attenuation. Therefore, an automatic gain adjustment circuit is required to receive a transmission signal transmitted from a mobile station at the same level (amplitude value) regardless of the distance between the mobile station and the base station. This automatic gain adjustment circuit is usually provided in the reception high frequency section 25, and automatically adjusts the RF signal received by the antenna 24.

FIG. 8 shows an example of this automatic gain adjustment circuit, which will be described. The received signal is input to the full-wave rectifier circuit 18 and the gain adjustment circuit 20. In the full-wave rectifier circuit 18,
Full-wave rectification of the input received signal. Full-wave rectifier circuit 1
The signal that has been full-wave rectified at 8 is integrated by the integration circuit 19. At this time, the time constant integrated by the integration circuit 19 is performed in units of several symbols. Here, the reason why the time constant of the integration circuit 19 is set to several symbol units will be described. In mobile communication, communication is often performed between a mobile object that moves out of line of sight and moves at high speed. For this reason, the communication path becomes a so-called multipath transmission path in which a large number of reflected waves are combined, and transmission path distortion (hereinafter, referred to as fading) occurs. The fluctuation of the reception level due to the fading is several tens of dB. The fading speed changes in proportion to the radio frequency and the moving speed of the moving object. Further, a frequency displacement due to the Doppler effect caused by the movement of the transmission side or the reception side is also conceivable.

That is, the automatic gain adjustment circuit shown in FIG. 8 must adjust the gain in accordance with the fading.
For this reason, the time constant of the integration circuit 19 in FIG. 8 needs to be in units of several symbols. The signal integrated by the integration circuit 19 is input to the gain adjustment circuit 20 as a gain adjustment signal. The gain adjustment circuit 20 performs gain adjustment based on the gain adjustment signal from the integration circuit 19 and outputs the result.
Therefore, regardless of the distance between the mobile station and the base station, the gain of the received signal can be adjusted to the same level (amplitude value). FIG.
The automatic gain adjustment circuit similar to that shown in FIG.

Next, a case where the automatic gain adjustment circuit of FIG. 8 is used for bidirectional transmission using one transmission band will be described. Bidirectional transmission means that a transmission line from the mobile station side to the base station side (hereinafter referred to as uplink) and a transmission line from the base station side to the mobile station side (hereinafter referred to as downlink) are alternated in time. , And the transmission is performed, and bidirectional transmission in the same defined frequency band is possible. FIG. 11 shows the configuration of an FPU for bidirectional transmission using this one transmission band, and FIG. 4 shows an outline of the operation of this bidirectional transmission. The master-side transmission control unit 27, transmission high-frequency unit 29, reception control unit 28,
RF receiving section 30, RF switching circuit 31, transmitting / receiving antenna 32, and transmitting / receiving antenna 33 on the slave side, RF
The transmission system includes a switching circuit 34, a reception high-frequency unit 35, a reception control unit 37, a transmission high-frequency unit 36, and a transmission control unit 38.

Hereinafter, this operation will be described. The transmission data rate of the transmission control unit 27 on the master side is determined by the clock oscillator CK OSC. The data input to the ID terminal is digitally modulated, then modulated into an IF signal having a frequency determined by the local oscillator LO OSC, and output.
The input transmission high-frequency unit 29 converts the IF signal from the transmission control unit 27 into a specified RF frequency. Converted R
The F signal is input to the RF switching circuit 31, and the RF switching circuit 31 performs switching with the signal received by the transmission / reception antenna 32 in order to perform bidirectional transmission using one transmission band. Then, it is transmitted by the transmitting / receiving antenna 32. Further, the signal received by the transmitting / receiving antenna 32 is switched by the RF switching circuit 31, and
At 0, it is converted to an IF signal. Reception control unit 28
After demodulating the input received IF signal with the frequency of the local oscillator LO VCO, the received IF signal is output as a digital signal having a rate determined by the output of the clock oscillator CK VCO.

[0010] Similarly, the transmission control unit 3
The transmission data rate of 8 is determined by the clock oscillator CK OSC. The data input to the ID terminal is digitally modulated, then modulated into an IF signal having a frequency determined by the local oscillator LO OSC, and output. The input transmission high-frequency unit 36 converts the IF signal from the transmission control unit 38 into a specified RF frequency. The converted RF signal is input to the RF switching circuit 34, and the RF switching circuit 34 performs switching with the signal received by the transmission / reception antenna 33 in order to perform bidirectional transmission using one transmission band. And
It is transmitted by the transmitting / receiving antenna 33. The signal received by the transmitting / receiving antenna 33 is transmitted to the RF switching circuit 34.
, And is converted into an IF signal in the reception high frequency section 35. The reception control unit 37 demodulates the input reception IF signal with the frequency of the local oscillator LO VCO,
It is output as a digital signal at a rate determined by the clock oscillator CK VCO output. Here, as shown in FIG. 3, each of the uplink and downlink transmission signals has a frame structure, and several types of synchronization symbols, a data symbol group for transmitting an information code, and a symbol in the latter half of the frame are included in a reception period. And a pause period at a time interval in consideration of the radio wave propagation time. The synchronization symbol group and the data symbol group are the same as those described above. The downlink transmission signal Tm is transmitted in frame units, and the reception signal Rs
As received by the mobile station. Further, an uplink transmission signal Ts is also transmitted in frame units, and received by the base station as a reception signal Rm. Here, the operation when the automatic gain adjustment circuit of FIG. 8 is used for the received signal Rs on the mobile station side will be described.

The automatic gain adjustment circuit includes a reception high frequency section 30,
35 and received by the transmitting and receiving antennas 32 and 33.
Automatic gain adjustment of the F signal. The transmission signal on the mobile station side is a repetition of a pause period in consideration of the reception signal Rs, the transmission signal Ts, and the radio wave propagation time on the time axis. At this time,
Since the transmission signal Ts is included in the transmission signal on the mobile station side, it is assumed that it is not input to the automatic gain adjustment circuit. That is, a signal (hereinafter referred to as A) input to the automatic gain adjustment circuit of FIG.
GC input signal) is absent on the time axis except for the received signal Rs. The AGC input signal is a full-wave rectifier circuit 1
8 and a gain adjustment circuit 19. Full-wave rectifier circuit 1
In step 8, the input AGC input signal is full-wave rectified.
The signal subjected to full-wave rectification by the full-wave rectification circuit 18
9 is integrated. At this time, the time constant of the integration circuit 19 is in units of several symbols as described above. The signal integrated by the integration circuit 19 is input to the gain adjustment circuit 20 as a gain adjustment signal.

The gain adjustment circuit 20 performs gain adjustment based on the gain adjustment signal from the integration circuit 19 and outputs the result. FIG. 10 shows the AGC output signal at this time. FIG.
0, the received signal R
In the s part, the gain adjustment is controlled normally, but in the part other than the received signal Rs (no signal), the AG of the gain adjustment circuit 20 is controlled.
Control is performed to increase the gain until the C output signal is saturated. Portions other than the received signal Rs are no signals,
Noise is present. That is, the AGC of the gain adjustment circuit 20
Controlling to increase the gain until the output signal is saturated increases the noise level. When the noise level rises, there arises a problem that synchronous detection becomes difficult. To remedy this problem, the integration circuit 1 is used to prevent the noise level from rising unnecessarily.
It is necessary to set the time constant of 9 in units of several frames. However, as described above, if the time constant of the integration circuit 19 is set to a unit of several frames, there is a problem that it does not follow the fading.

[0013]

In the above-mentioned prior art, bidirectional transmission using one transmission band is performed as shown in FIGS.
In order to use this automatic gain adjustment circuit, it is necessary to set the time constants of these integration circuits in units of several frames.
However, in mobile communication, communication is often performed between a moving object that moves out of line of sight and moves at high speed. For this reason, the communication path becomes a so-called multipath transmission path in which a large number of reflected waves are combined, and fading occurs. The fluctuation of the reception level due to the fading is several tens of dB. The fading speed changes in proportion to the radio frequency and the moving speed of the moving object. Further, a frequency displacement due to the Doppler effect caused by the movement of the transmission side or the reception side is also conceivable. That is, the automatic gain adjustment circuits shown in FIGS. 8 and 9 must adjust the gain following the fading. For this reason, the time constant of the integrating circuits in FIGS. 8 and 9 must be set in units of several symbols. That is, in bi-directional transmission using one transmission band, the time constant of the integrating circuit shown in FIGS. 8 and 9 must be set in units of several frames in order to normally perform automatic gain control of a received signal. However, there is a problem that it becomes difficult to control the gain following the fading. The present invention eliminates these drawbacks, and in a bidirectional transmission apparatus comprising a base station transmission apparatus and a mobile station transmission apparatus, which automatically switches between a transmission period and a reception period and performs bidirectional transmission, receives signals following fading. An object of the present invention is to realize a bidirectional transmission device capable of automatically adjusting a signal gain.

[0014]

In order to achieve the above object, the present invention comprises a base station transmission apparatus and a mobile station transmission apparatus, and performs bidirectional transmission by automatically switching between a transmission period and a reception period. In one-way transmission device, there are two types of circuits for automatically adjusting the gain of the received signal, and the function of automatically switching between the two types of circuits is provided. One of the two types of automatic gain adjustment circuits includes: It has a function of adjusting the automatic gain only during the reception period of the received signal, and a function of automatically switching the period of the automatic gain adjustment of the received signal.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 shows an outline of the operation of bidirectional transmission which comprises a base station transmission apparatus and a mobile station transmission apparatus and automatically switches between a transmission period and a reception period. As described above, the bidirectional transmission is a method in which transmission is performed by alternately switching the uplink and the downlink in time, and bidirectional transmission in the same defined frequency band is possible. Each of the uplink and downlink transmission signals has a frame structure as shown in FIG. 3, and several types of synchronization symbol groups, data symbol groups for transmitting information codes, and symbols in the latter half of the frame take into account the reception period and radio wave propagation time. It consists of a pause period of the specified time interval. The synchronization symbol group and the data symbol group are the same as described above. Downlink transmission signal Tm
Are transmitted in frame units and received by the mobile station as a received signal Rs. Further, an uplink transmission signal Ts is also transmitted in frame units, and received by the base station as a reception signal Rm. The transmission signal on the mobile station side is a repetition of a pause period in consideration of the reception signal Rs, the transmission signal Ts, and the radio wave propagation time on the time axis. At this time, since the transmission signal Ts is added to the transmission signal on the mobile station side, it is assumed that it is not input to the automatic gain adjustment circuit. That is, A of the automatic gain adjustment circuit
The GC input signal is absent on the time axis except for the received signal Rs. The same applies to transmission signals on the base station side. In order to automatically adjust the gain of the AGC input signal, it is necessary to set the time constant of the integrating circuit in units of several frames as described above. However, there is a problem that it becomes difficult to perform gain control following fading.

FIG. 1 shows the configuration of an embodiment of the present invention which solves this problem, and will be described below. The AGC input signal is input to the IN1 terminal of the switching circuit 1. The switching circuit 1 is A
Switching is performed by the GC circuit switching signal 2. The AGC circuit switching signal 2 is a switching signal between the AGC circuit unit 3 and the AGC circuit unit 4. OUT1, which is the output of the switching circuit 1, is
Full-wave rectification circuit 5 and gain adjustment circuit 9 in AGC circuit section 3
Is input to The full-wave rectifier circuit 5 performs full-wave rectification on the input signal. The signal subjected to full-wave rectification by the full-wave rectification circuit 5 is integrated by the integration circuit 6. At this time, the integration time constant in the integration circuit 6 is in units of several frames. Integration circuit 6
Is integrated as a gain adjustment signal by the variable amplifier 7.
Is input to The variable amplifier 7 adjusts the input signal to an optimum value of the gain adjustment signal based on the gain adjustment signal from the integration circuit 6 and outputs the adjusted signal. Here, the reference signal for adjusting to the optimum value is the gain level setting signal 8. The gain level setting signal 8 is necessary when bidirectional transmission is performed by changing the ratio between the transmission signal and the reception signal within one frame period in FIG. That is, if the ratio of the received signal within one frame period changes, the signal level of the gain adjustment signal from the integration circuit 6 changes. Since the gain adjustment circuit 9 performs gain adjustment based on the gain adjustment signal, if the signal level of the gain adjustment signal changes, the signal level of the AGC output signal changes.
That is, automatic gain adjustment becomes impossible.

Therefore, when bidirectional transmission is performed by changing the ratio between the transmission signal and the reception signal, the gain level setting signal 8 for controlling the gain of the variable amplifier 7 based on the ratio between the transmission signal and the reception signal. Is required. The output of the gain adjustment circuit 9 is input to the IN1 terminal of the switching circuit 17. The switching circuit 17 is switched by the AGC circuit switching signal 2 similarly to the switching circuit 1, selects the IN1 side, and outputs a signal whose gain is automatically adjusted to an optimum value. OUT2, which is the output of the switching circuit 1, is input to the received signal separation circuit 10 in the AGC circuit unit 4. In the separation of the received signal from the AGC input signal, only the received signal is separated by the received signal separation signal 11. The output of the reception signal separation circuit 10 from which only the reception signal is separated is input to the hold circuit 12. The hold circuit 12 adds the last information symbol data of the received signal in one frame until the first synchronization symbol (null) of the received signal of the next frame comes. That is, the last symbol data is arranged until the first synchronization symbol (null) of the received signal of the next frame comes from the last information symbol data of the received signal in one frame.

The output of the hold circuit 12 is input to a full-wave rectifier circuit 13 and a gain adjustment circuit 16. The full-wave rectifier circuit 13 performs full-wave rectification on the input output signal of the hold circuit 12. The signal subjected to full-wave rectification by the full-wave rectification circuit 13 is integrated by the integration circuit 14. At this time, the time constant for integration by the integration circuit 14 is performed in units of several symbols. The signal integrated by the integration circuit 14 is input to the gain adjustment circuit 16 as a gain adjustment signal. The gain adjustment circuit 16 adjusts the gain of the input signal based on the gain adjustment signal from the integration circuit 14 and outputs the result. Gain adjustment circuit 16
Is input to the IN2 terminal of the switching circuit 17. The switching circuit 17 is switched by the AGC circuit switching signal 2 similarly to the switching circuit 1, selects the IN2 input, and outputs a signal whose gain is automatically adjusted to an optimum value.

Next, in the switching circuits 1 and 17, the AGC
The timing at which the circuit switching signal 2 switches is described. A transmission signal is transmitted from the base station side,
In addition, when the power of the mobile station is turned on, and when a transmission signal is transmitted from the base station and the synchronization of the mobile station is not established, the AGC input signal is switched to the AGC circuit in the switching circuit 1 in FIG. The signal is output to the OUT1 side by the switching signal 2. Then, the gain is automatically adjusted to an optimum value by the AGC circuit unit 3 and input to the IN1 terminal of the switching circuit 17.
At this time, in the switching circuit 17, as in the switching circuit 1, A
The input signal IN1 side is selected and output by the GC circuit switching signal 2. This output signal establishes synchronization between the base station and the mobile station. If the synchronization between the base station and the mobile station is established, the transmission signal from the base station side (the reception signal on the mobile station side) within one frame period of the transmission signal from the base station side
Is in which phase. That is, the transmission signal from the base station can be separated on a frame basis,
This separated signal is the received signal separated signal 11.

Therefore, when the synchronization between the base station and the mobile station is established, the AGC input signal input to the switching circuit 1 is output to the OUT2 side by the AGC circuit switching signal 2 in FIG. Then, the gain is automatically adjusted to an optimum value by the AGC circuit unit 4 and input to the IN2 terminal of the switching circuit 17. At this time, in the switching circuit 17, as in the switching circuit 1,
The input signal IN2 side is selected and output by the AGC circuit switching signal 2. The same operation is performed for a transmission signal from a mobile station to a base station. FIG. 5 shows the AGC circuit switching signal 2 before the synchronization is established, the AGC circuit switching signal 2 after the synchronization is established, and the reception signal separation circuit 10.
4 shows a timing chart of one frame period. As described above, in bidirectional transmission using one transmission band,
Automatic gain adjustment that follows fading can be performed.

Next, a second embodiment of the present invention is shown in FIG. 2 and will be described below. The difference from the invention of FIG.
In the GC circuit section 4, there is no hold circuit 12 between the reception signal separation circuit 10 and the full-wave rectification circuit 13,
The DC level hold circuit 15 is connected between the integration circuit 14 and the gain adjustment circuit 16. All other operations are the same as those in FIG. Hereinafter, only the different parts will be described. Received signal separation signal 11
Accordingly, the signal from which only the received signal is separated by the received signal separation circuit 10 is input to the full-wave rectification circuit 13, subjected to full-wave rectification, and input to the integration circuit 14. In the integration circuit 14,
Integrate with a time constant in units of several symbols. When the integrated output is input to the gain adjustment circuit 16, as shown in FIG.
The GC output signal is saturated except for the received signal. In order to solve this problem, according to the present invention, the output of the integrating circuit 14 is input to the DC level hold circuit 15, and the last DC level of the received signal period is set to the next received signal based on the received signal separation signal 11. Hold until it comes. The output of the DC level hold circuit 15 is input to the gain adjustment circuit 16 as a gain adjustment signal, and adjusts the gain to an optimum value. That is, the DC level hold circuit 15 does not needlessly raise the gain even during periods other than the reception signal (no signal).

[0022]

According to the present invention, in a bidirectional transmission apparatus comprising a base station transmission apparatus and a mobile station transmission apparatus and performing bidirectional transmission by automatically switching between a transmission period and a reception period, the gain of a received signal is reduced. Automatic gain adjustment is possible following the fading.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention.

FIG. 3 is a diagram showing a frame structure of a signal in the bidirectional transmission system.

FIG. 4 is a timing chart of bidirectional transmission.

FIG. 5 is a timing chart of an AGC circuit switching signal and a received signal separation signal according to the present invention.

FIG. 6 is a diagram showing a frame structure of a signal in the one-way transmission system.

FIG. 7 is a timing chart of signals in the one-way transmission system.

FIG. 8 is a block diagram showing a configuration of an example of a conventional technique.

FIG. 9 is a block diagram showing a configuration of an example of a conventional technique.

FIG. 10 is a timing chart of an AGC output signal according to the related art.

FIG. 11 is a diagram showing the structure of a one-way transmission FPU.

FIG. 12 is a diagram showing a structure of an FPU for bidirectional transmission.

[Explanation of symbols]

1, 17: switching circuit, 3, 4: AGC circuit section, 5, 1
3, 18: full-wave rectifier circuit, 6, 14, 19: integrating circuit,
7: Variable amplifier, 9, 16, 20: Gain adjustment circuit, 1
0: received signal separation circuit, 12: hold circuit, 15: D
C level hold circuit, 21, 27, 38: transmission control unit, 22, 29, 36: transmission high frequency unit, 23, 24, 3
2, 33: antenna, 25, 30, 35: reception high frequency unit, 26, 28, 37: reception control unit, 31, 34: RF
Switching circuit.

Continued on the front page (72) Inventor Seiichi Sano 32 Miyukicho, Kodaira-shi, Tokyo Inside the Koganei Plant, Hitachi Electronics Co., Ltd. 72) Inventor Nobuo Tsukamoto 32, Miyukicho, Kodaira-shi, Tokyo Inside the Koganei Plant of Hitachi Electronics Co., Ltd.

Claims (3)

[Claims] 1. A bidirectional transmission device comprising a base station transmission device and a mobile station transmission device for performing a bidirectional transmission in which a transmission period and a reception period are automatically switched, wherein at least a gain of a received signal is automatically adjusted. Two kinds of gain adjusting means and the two kinds of gain adjusting means are adapted to a received signal,
A bidirectional transmission device comprising means for selecting and switching. 2. The two-way transmission device according to claim 1, wherein one of the two types of gain adjustment means has a function of performing automatic gain adjustment only during a reception period of a reception signal. . 3. A circuit for automatically adjusting the gain of a received signal of a bidirectional transmission device which comprises a base station transmission device and a mobile station transmission device and performs bidirectional transmission for automatically switching between a transmission period and a reception period. And a means for automatically switching a period for automatic gain adjustment of a received signal.