JPH0290711A - Booster amplifier for radio wave relay and its gain control method - Google Patents

Abstract

PURPOSE:To prevent destruction of an amplifier element due to thermal runaway thereof caused by the oscillation of an amplifier by controlling the gain in response to a change in the radio wave propagation state around the radio wave relay booster amplifier. CONSTITUTION:With the radio wave relay booster amplifier 20 starting the AGC operation due to the saturation of an amplifier 22 caused by an excess input signal or the saturation of the amplifier 22 through the production of the oscillation caused by the reduction in the propagation loss L between transmission reception antennas 26, 30, an oscillation stop circuit 44 of the booster amplifier 20 decides whether the cause to the saturation of output is due to an excess input or due to the oscillation. If the saturation is decided due to the excess input, the gain control using an AGC control loop is implemented and if it is decided due to the oscillation, the oscillation stop circuit 44 applies the gain control so as to keep the relay gain G from being decreased till the oscillation is terminated. Thus, the saturation of the amplifier output is prevented even if an excess reception signal is applied.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a booster amplifier for radio relay and a gain control method thereof. Automatically controls the gain of a wireless relay booster amplifier that retransmits at the same frequency from an antenna to prevent oscillation phenomena occurring in the wireless relay booster amplifier and saturation of the wireless relay booster amplifier. The present invention relates to a booster amplifier for wireless relay and a gain control method thereof.

[Background of the invention] In the field of wireless communication that uses radio frequencies, such as television broadcasting, car telephones, MCA, pagers, and mobile communication such as train radio, it is necessary to maintain good reception of radio waves even in remote areas. Therefore, efforts are being made to utilize a radio relay booster amplifier that amplifies the radio frequency signal received by the receiving antenna and transmits it from the transmitting antenna at the same frequency as the received radio frequency signal.

FIG. 1 shows a general circuit configuration of this type of booster amplifier. In other words, the wireless relay booster amplifier 2
is composed of a receiving antenna 4, an amplifier 6, and a transmitting antenna 8, and the received signal 10 received by the receiving antenna 4 is
is amplified by an amplifier 6 and then wirelessly transmitted from a transmitting antenna 8 as a transmitting signal 12. In this radio relay booster amplifier 2, a received signal 10 and a transmitted signal 1
2 have the same frequency, and the relay gain G is the relay gain G-G + x when the gain of the receiving antenna 4 is G1, the gain of the amplifier 6 is G2, and the gain of the transmitting antenna 8 is 03.
It is expressed as G2 x G3. Furthermore, if the propagation loss between the transmitting antenna 8 and the receiving antenna 4 is L, then the signal 1 that wraps around from the transmitting antenna 8 to the receiving antenna 4 by positive feedback
The level value of 4 becomes the level value of 1/L of the transmission signal 12.

Incidentally, in such a radio relay booster amplifier 2, when the values of the relay gain G and the propagation loss become the same value, an oscillation phenomenon occurs. When the oscillation phenomenon occurs, it has a negative effect on the wireless communication system that uses the wireless relay booster amplifier 2, and in the worst case, the amplifier 6 may be destroyed, which may cause the transmission to stop. . Therefore, when amplifying a received signal using the amplifier 6, the propagation loss between the transmitting and receiving antennas 4 and 8 is normally made to be sufficiently large compared to the relay gain G of the radio relay booster amplifier 2. The mounting position of the transmitting/receiving antenna 4.8 and the amplification degree of the amplifier 6 are determined.

However, even if the installation of the radio relay booster amplifier 2 is initially set so that the propagation loss between the transmitting and receiving antennas 4 and 8 is sufficiently large relative to the relay gain G, During the operation of a wireless communication system using the relay booster amplifier 2, the transmitting/receiving antenna 4. There is a possibility that the radio wave propagation loss between . However, there still remains a fear that the amplifier 6 may be destroyed.

Furthermore, another problem with the wireless communication system using the radio relay booster amplifier 2 is that the radio relay booster amplifier 2 When approaching the installation position of the receiving antenna 4 constituting the wireless relay booster amplifier 2, a received signal of a high level higher than a predetermined level is input to the wireless relay booster amplifier 2, and this causes the amplifier 6, in other words, the wireless relay booster amplifier 2 to 2 may become saturated and fall into a state where high-quality wireless communication cannot be performed.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages. In addition to stopping the oscillation of the wireless relay booster amplifier that occurs due to the reduction in loss, the gain of the wireless relay booster amplifier is automatically adjusted even if an excessive received signal is manually applied to the wireless relay booster amplifier. Moreover, it is an object of the present invention to provide a radio relay booster amplifier and its gain control method that can be properly adjusted to always carry out stable and high-quality radio wave propagation.

[Means for achieving the object] In order to achieve the above object, the present invention receives a radio frequency signal with a receiving antenna, amplifies it with an amplifier, and then transmits it from a transmitting antenna at the same frequency as the receiving frequency. In a radio relay booster amplifier that detects a part of the output signal of the amplifier with a detector and controls the gain of the amplifier according to the output signal of the detector, the output signal of the detector is generated by gain control by an AGC loop. a comparator whose threshold is a predetermined level between the maximum value of the ripple component and a detector output value corresponding to the saturation level of the amplifier, and whose comparison human power value is the output signal of the detector; When two or more output pulses of the comparator arrive within a time equal to 1/2 the period of the ripple component connected to the output terminal and related to the ΔGC loop plus a predetermined margin time, the wireless relay booster amplifier The amplifier is characterized by comprising an oscillation determination circuit that determines that the amplifier is in an oscillation state, and a gain control circuit that substantially controls the gain of the amplifier by a predetermined amount in accordance with an output value of the oscillation determination circuit.

In addition, the present invention receives a radio frequency signal with a receiving antenna, amplifies it with an amplifier, transmits it from the transmitting antenna at the same frequency as the receiving frequency, and detects a part of the output signal of the amplifier with a detector. A gain control method for a radio relay booster amplifier, which controls the gain of the amplifier according to an output signal of the detector, the output signal of the detector intermittently reaching the saturation level of the amplifier twice or more within a predetermined time. When the booster amplifier for wireless relay increases to a corresponding level, the wireless relay booster amplifier is identified as being in an oscillating state, and the gain of the amplifier is controlled to be substantially limited, thereby suppressing the oscillation of the wireless relay booster amplifier. It is characterized by stopping.

Furthermore, the present invention receives a radio frequency signal with a receiving antenna, amplifies it with an amplifier, transmits it from the transmitting antenna at the same frequency as the receiving frequency, and detects a part of the output signal of the amplifier with a detector. A gain control method for a radio relay booster amplifier, which controls the gain of the amplifier according to an output signal of the detector, the output signal of the detector intermittently reaching the saturation level of the amplifier twice or more within a predetermined time. When the booster amplifier for radio relay increases, it is determined that the radio relay booster amplifier is in an oscillation state, and the gain of the amplifier is controlled to be substantially limited, while the output signal of the detector increases substantially monotonically, or The feature is that when the gain increases in a substantially stepwise manner, the gain is controlled to be limited by an AGC loop.

[Embodiments] Next, preferred embodiments of the wireless relay booster amplifier gain control method according to the present invention in relation to the wireless relay booster amplifier to which the method is applied will be listed, and the details will be described below with reference to the accompanying drawings. Explain.

In FIG. 2, reference numeral 20 indicates a wireless relay booster amplifier to which the wireless relay booster amplifier control method according to the present embodiment is applied.

The wireless relay booster amplifier 20 basically includes an amplifier 22, a reception antenna 26 that supplies a reception signal 24 to the amplifier 22, a transmission antenna 30 that transmits a signal from the amplifier 22 as a transmission signal 28, and the present invention. and a gain control section 32 related to the main part of.

The signal received by the receiving antenna 26 is transmitted to the gain controller 3.
The signal is introduced into the input terminal of the amplifier 22 through the variable attenuators 34 and 36 that constitute the antenna 2, is amplified by the amplifier 22, and is then introduced into the transmitting antenna 30 via the duplexer 38. In this case, a part of the signal is branched from the output signal V6□ of the amplifier 22 as the main signal in the branching filter 38, and the branched signal is passed through the detector 40 as an output signal V d 11 L to A G C (Automatic
ic Ga1n (:ontrol) loop control circuit 4
2 and comparators 46 and 48 constituting the oscillation stop circuit 44
is introduced into the negative input terminal of

The positive input terminals of the comparators 46 and 48 are supplied with reference voltages VRI and Vi12 from the reference voltage generators 50 and 52, respectively.
is introduced, and a voltage signal VCI and a pulse signal as analog signals are sent to the output terminals of the comparators 46 and 48, respectively, according to the voltage difference between the output signal Vast of the detector 40 and the reference voltage vi l SV R2. The voltage signal V as .

2 occurs.

The output signal VCI of the comparator 46 is converted into an attenuation control signal VAI by an attenuation controller 54, and then introduced to an attenuation l control terminal ATI of the variable attenuator 36. On the other hand, the oscillation determination section 56 based on the output signal VC2 of the comparator 48
It is determined whether the radio relay booster amplifier 20 is oscillating or not, and the oscillation determination section 56 introduces the determination signal V, 2 to the attenuation amount controller 58 based on the determination result. The attenuation amount controller 58 receives the determination signal V. 2, the attenuation amount control signal VA2 is generated based on the variable attenuator 34.
is supplied to the attenuation amount control terminal AT2. The variable attenuator 34 adjusts its attenuation amount AT according to the attenuation amount control signal VA2.
N is controlled. The oscillation determining unit 5G is configured with a timer or the like to determine that the wireless relay booster amplifier 20 is in an oscillating state when two or more pulse-like voltage signals VC2 arrive within a predetermined time period to be described later. ing.

The wireless relay booster amplifier to which the wireless relay booster amplifier gain control method according to the present embodiment is applied is basically configured as described above, and its operation and effects will be explained next.

FIGS. 3A, B, and C are explanatory diagrams of the operation of the wireless relay booster amplifier 20 shown in FIG. There is. Therefore, first, the monotonically increasing ramp-shaped received signal 24 as shown in FIG. 3A (a) reaches time t. The case where the signal is input to the wireless relay booster amplifier 20 at this point will be explained. In this case, as shown in FIG. 3A, the four output signals v of the amplifier 22 are
Therefore, the output signal Vdet of the detector 40 changes in proportion to the output signal V asp as shown in FIG. 3A(C), and this output signal V d
comparator 4 where e t constitutes the AGC loop control circuit 42;
6 is introduced into the negative input terminal. Therefore, the output signal Vdat of the wave detector 40 is set to the reference voltage Vll of the reference voltage generator 50.
If it exceeds the analog output signal VCI of the comparator 46
Accordingly, an attenuation control signal VAI is introduced from the attenuation controller 54 to the variable attenuator 36 in order to attenuate the attenuation of the variable attenuator 36 by a predetermined amount (time is also 2 points). As shown in (b), at time t2 after the response time of the AGC loop has elapsed, the gain limiting operation of the relay gain G is started, and the signal level of the output signal V 6 a P of the amplifier 22 is decreased. In FIG. 3A(b), the two broken lines indicate the saturation level V2□80. of the amplifier 22, respectively. and the AGC control level V A corresponding to the reference voltage V Rl
It represents a c.

On the other hand, the comparator 48 constituting the oscillation stop circuit 44
As understood from the output signal V d e t of the detector 40 in FIG. A (C), the reference voltage V of the reference voltage generator 52
R2 is the reference voltage v as the control level of the AGC loop
Since it is set to a higher voltage compared to m +,
As shown in FIG. 3A(d), the output signal V c
2 does not change. Therefore, the attenuation amount AT of the variable attenuator 34
N also does not change as shown in FIG. 3A(e). That is, in the radio relay booster amplifier 20 according to the present invention, when an excessive ramp-shaped received signal 24 is manually generated, the relay gain G is controlled by a predetermined amount by the control action of the AGC loop control circuit 42, and the excessive transmitted signal is 28 is never sent. The above description is an explanation of the operation and effect when the ramp-shaped received signal 24 shown in FIG. 3A (a) is input to the wireless relay booster amplifier 20.

Next, a case will be described in which a stepwise received signal 24 increasing stepwise as shown in FIG. 3B(a) is input to the wireless relay booster amplifier 20 at time t3. In this case, the output signal Vamp of the amplifier 22
As shown in FIG. 3B(b), the amplifier 2
2 to the saturation level V22S11. In this case, the output signal Vd,1 of the detector 40 is
As shown in (C), the reference voltage V Rl increases rapidly and
, VR2 and reach the saturation level VSUT corresponding to the saturation level V22SUA of the amplifier 22. Therefore, an output signal VCI corresponding to the difference between the saturation level VSu□ and the comparison voltage VRI is generated in the comparator 46, and the attenuation amount controller 54
A predetermined attenuation amount control signal VAI corresponding to the output signal VCI is introduced into the variable attenuator 36 from the attenuation control signal VAI. by this,
The amount of attenuation of the variable attenuator 36 increases, and after a certain period of time has elapsed, for example, at time t4, the output signal V a of the amplifier 22
mp is the AGC control level and almost converges to V A G C (
(See Figure 3B(b)).

Therefore, the wireless relay booster amplifier 20 according to the present invention
In this case, even if a step-like excessively large received signal 24 is manually generated, the control action of the AGC loop control circuit 42 prevents an excessively large transmitted signal 28 from being transmitted in the same manner as described above. In this case, since a voltage exceeding the comparison voltage VR□ is applied to the negative input terminal of the comparator 48 constituting the oscillation stop circuit 44 (see FIG. 3B (C)), the output signal Vc2 of the comparator 4B As shown in FIG. 3B(d), one pulse is generated. Here, the oscillation determination unit 56 determines the time constant r (FIG. 3B (C)) specific to the AGC loop.
), the output signal V[12 of the oscillation determining section 56 is a non-oscillating state. A signal corresponding to, for example, a low level 0 signal,
The attenuation amount AT of the variable attenuator 34 is controlled by the attenuation amount controller 58.
N does not change as shown in FIG. 3B(e).

T=r+margin time...(1) (Here, the margin time is usually a time sufficiently shorter than time τ/2) The above explanation is based on the step-like received signal shown in Figure 3B (a). 24 is an explanation of the effect when inputted into the wireless relay booster amplifier.

Next, as shown in FIG. 3C(a), a radio wave reflector (not shown) appears near the wireless relay booster amplifier 20 at time t5, and the propagation loss between the transmitting and receiving antennas 26 and 30 is increased. The operation in the case of a quantitative decrease will be explained. In this case, from the transmitting antenna 30 to the receiving antenna 2
The signal level of the loop signal 60 that loops around to the amplifier 2 increases rapidly, and the signal level of the received signal 24 introduced into the variable attenuator 34 increases rapidly (not shown).
2's output signal V6□ rapidly increases to the saturation level V22SLIT (see FIG. 3C(b)). In this case, as described above, the level of the output signal V asp of the amplifier 22 is adjusted to A by the operation of the AGC loop control circuit 42.
The amount of attenuation of the variable attenuator 36 is increased to lower the GC control level to VAGC, and the relay gain G is lowered. Then, as shown at time t6 in FIG. 3C(b), when the relay gain G becomes smaller than the propagation loss between the receiving antennas 26 and 30, the oscillation temporarily stops and the output signal V
The level value of aap decreases rapidly.

However, the level value of the output signal V, □ is the AGC control level VAG. When it decreases to a level value below, the AGC loop control circuit 42 operates in the direction of increasing the relay gain G. Then, the relay gain G becomes larger than the propagation loss again, and the radio relay booster amplifier 20 starts oscillating (time ti point). In this way, the wireless relay booster amplifier 20 causes so-called blocking oscillation with the time constant T specific to the AGC loop.

In this case, the output signal vd□ of the detector 40 is the maximum voltage VAGC)I corresponding to the high level of the AGC operation and the saturation level of the amplifier 22, as shown in FIG. 3B(C) and C(C). The saturation level V S U corresponding to v2□soa is increased or decreased between 7. Therefore, the oscillation stop circuit 4
The value of the reference voltage vR□ introduced into the positive input terminal of the comparator 48 constituting 4 is lower than the output saturation level VSUa of the detector 40 corresponding to the saturation level V2□SIT at which the output of the amplifier 22 is saturated, and The maximum voltage of the ripple component of the detected signal V d e t when the AGC is operating normally (VAGC) I is set to a higher voltage than the right
(See (C)).

With this setting, the output signal V,2 of the comparator 48 becomes a pulse train signal having a period determined by the time constant τ specific to the AGC loop, as shown in FIG. 3C(d). Therefore, as described above, the oscillation determination unit 56 detects two or more pulses within the predetermined time T, that is, (τ0 margin time), and determines that the radio relay booster amplifier 20 is oscillating. The determined determination signal VD2, for example, a high level I signal is introduced into the attenuation amount controller 58. Therefore, the attenuation amount controller 58 outputs an attenuation amount control signal VA2 that increases the attenuation amount ATN of the variable attenuator 34 by a predetermined amount (see time t8 in FIG. 3C(e)). In this case, if the oscillation phenomenon still persists even if the attenuation amount ATN of the variable attenuator 34 increases by a predetermined amount, when the next two pulses are introduced into the oscillation determination section 56, the oscillation phenomenon shown in FIG. C
(e) time tlo point), again the attenuation amount controller 5
Attenuation control signal VA2 is output from variable attenuator 3.
The attenuation amount ATN of 4 increases. In this way, oscillation stops when the attenuation ATN of the variable attenuator 34 increases sequentially and the relay gain G becomes smaller than the propagation loss between the transmitting and receiving antennas 26 and 30 (Fig. 3C (d)). time t12 point).

In the above description, a control method is adopted in which oscillation is determined using two pulses, but it goes without saying that control may be performed so that determination is made using two or more pulses. Furthermore, as another method of controlling the attenuation i1 A T N, after determining the oscillation due to the first two pulses, for example,
After point t8, the oscillation can of course be stopped by controlling the attenuation IATN to increase every pulse as shown in FIG. 3C(f).

When the oscillation is stopped in this way, the pulse train no longer appears in the output of the voltage comparator 48, so the oscillation determining section 56 determines that the oscillation has stopped.

In this case, the attenuation amount controller 58 learns that the oscillation has stopped by the output signal VD2=O of the oscillation determination section 56, and stops increasing the attenuation amount ATN of the variable attenuator 34, so that the It operates to maintain the attenuation amount ATN.

As described above, in the wireless relay booster amplifier according to the present invention, oscillation occurs when the output level of the amplifier 22 is saturated due to an excessive input signal or due to a decrease in the propagation loss between the transmitting and receiving antennas 26 and 30. amplifier 2
When the output level of step 2 is saturated and the radio relay booster amplifier starts AGC operation due to the saturation phenomenon, the oscillation stop circuit determines whether the output saturation is due to excessive force or oscillation. Determine whether
If it is determined that the cause is excessive force, the gain is controlled by the AGC control loop, and if it is determined that the cause is oscillation, the relay gain G is controlled by the oscillation stop circuit until the oscillation phenomenon is resolved. The gain is controlled so that it continues to decrease.

Therefore, if the booster amplifier for radio relay according to the present invention is used, the amplifier output will not be saturated even when an excessive received signal is applied, and oscillation will not be caused even when the propagation loss between the transmitting and receiving antennas is reduced. It is possible to stably operate the relay amplification operation without causing any trouble.

In the above embodiment, different variable attenuators 34 and 36 are used, but they are made the same and the output signals of the attenuation controller 54 and the attenuation controller 58 are added. Of course, it may be configured to be introduced.

[Effects of the Invention] As described above, according to the present invention, in a radio relay booster amplifier in which the receiving frequency and the transmitting frequency are the same,
Gain control is performed to respond to changes in radio wave propagation conditions around the wireless relay booster amplifier. Therefore, when an excessive received signal is input to the wireless relay booster amplifier, the gain of the wireless relay booster amplifier is automatically reduced, and the gain can be appropriately controlled by so-called AGC operation. In addition, gain control is performed in response to changes in propagation loss, and if a blocking oscillation phenomenon occurs due to a decrease in propagation loss, the period related to the blocking oscillation is detected and determined to be in an oscillation state. The oscillation phenomenon can be suitably stopped by lowering the relay gain by a predetermined amount every cycle or every predetermined multiple of the cycle. This has the effect of preventing thermal runaway destruction of the amplification element due to the oscillation phenomenon of the amplifier. Therefore, according to the present invention, a stable and high quality radio relay booster amplifier and its gain control method can be obtained.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a general booster amplifier for wireless relay, FIG. 2 is an explanatory diagram of the configuration of a booster amplifier for wireless relay according to the present invention, and FIGS. 3 A to C are for the wireless relay shown in FIG. 2. FIG. 3 is an explanatory diagram of the operation of the booster amplifier. 20... Radio relay booster amplifier 22... Amplifier 24... Received signal 26... Receiving antenna 28... Transmitting signal 30... Transmitting antenna 32... Gain control unit 42... AGC Loop control circuit 44...Oscillation stop circuit 60...Detour signal Patent applicant Japan Radio Co., Ltd. Same as above Nippon Telegraph and Telephone Co., Ltd. Applicant's agent Patent attorney Tsuyoshi Chiba! 1 21N for firewood +5 +819 110111112

Claims (3)

[Claims] (1) After receiving a radio frequency signal with a receiving antenna and amplifying it with an amplifier, it is transmitted from the transmitting antenna at the same frequency as the receiving frequency, and a part of the output signal of the amplifier is detected by a detector. In a wireless relay booster amplifier that controls the gain of the amplifier according to the output signal, a detector output corresponding to the maximum value of the ripple component of the detector output signal generated by gain control by the AGC loop and the saturation level of the amplifier. a comparator that uses a predetermined level between the wave detector as a threshold and a comparison input value as the output signal of the detector;
The wireless relay booster amplifier is in an oscillating state when two or more output pulses from the comparator arrive within a time period equal to 1/2 the period of the ripple component related to the C loop plus a predetermined margin time. 1. A booster amplifier for radio relay, comprising: an oscillation determination circuit that determines that the oscillation determination circuit determines that the oscillation determination circuit determines the oscillation determination circuit; and a gain control circuit that substantially controls the gain of the amplifier by a predetermined amount in accordance with an output value of the oscillation determination circuit. (2) After receiving a radio frequency signal with a receiving antenna and amplifying it with an amplifier, it is transmitted from the transmitting antenna at the same frequency as the receiving frequency, and a part of the output signal of the amplifier is detected by a wave detector. A gain control method for a wireless relay booster amplifier, which controls the gain of the amplifier according to an output signal, wherein the output signal of the detector intermittently corresponds to the saturation level of the amplifier twice or more within a predetermined time. level, the wireless relay booster amplifier is identified as being in an oscillating state, and the gain of the amplifier is controlled to be substantially limited, thereby stopping the oscillation of the wireless relay booster amplifier. A gain control method for a wireless relay booster amplifier, characterized in that: (3) After receiving a radio frequency signal with a receiving antenna and amplifying it with an amplifier, it is transmitted from the transmitting antenna at the same frequency as the receiving frequency, and a part of the output signal of the amplifier is detected with a detector. A gain control method for a radio relay booster amplifier, which controls the gain of the amplifier according to an output signal, wherein the output signal of the detector intermittently rises to the saturation level of the amplifier twice or more within a predetermined time. When the radio relay booster amplifier is identified as being in an oscillating state, the gain of the amplifier is controlled to be substantially limited, while the output signal of the detector increases substantially monotonically or substantially stepwise. 1. A gain control method for a radio relay booster amplifier, characterized in that when the gain increases to a certain level, it is determined that the gain is over-output due to an over-input, and the gain is controlled to be limited by an AGC loop.