JP4952402B2 - Amplifier unit - Google Patents

Description

  The present invention relates to an amplifier unit, and is particularly suitable for application to an amplifier unit for transmitting / receiving RF signals in a radio base station of a mobile communication system.

  Since the RF amplifier of a radio base station is usually installed outdoors, the amplifier gain is monitored by drawing the amplifier output into the station and monitoring it. Specifically, as shown in FIG. 7B, pilot signals P of different levels (that is, frequencies outside this predetermined band) are injected (multiplexed) into the main signal S having a predetermined bandwidth, and these signals are injected (multiplexed). In addition, the gain of the amplifier can be indirectly monitored by externally monitoring the amplified pilot signal level. Details will be described below.

  FIG. 7A is a circuit diagram of a conventional amplifier unit. In the figure, 10 is an amplifier unit, 11 is a previous band pass filter (BPF) that passes the main signal band, 12 is a pilot signal oscillator, and 14 is a direction. A coupler (Cup) composed of a sex coupler, 15 is a transistor (Tr) as an amplifying element, and 13A and 13B are isolators (Iso).

  Next, the basic flow of the pilot signal in this configuration will be described. When the pilot signal P of the oscillator 12 is coupled to the main line by the coupler 14, a pilot signal (forward component) Pf having a fraction of the power appears on the terminal 2 side of the coupler 14, and the terminal 1 side. In addition, a pilot signal (directional component) Pr of 1/10 or less of the power appears. Further, the forward component Pf is partially reflected at the input due to the mismatch of the transistor 15, and the reflected component Pfr is combined (multiplexed) with the directional component Pr and returns to the input terminal side of the amplifier unit 10. Hereinafter, the reflection component Pfr and the directional component Pr of the pilot signal are collectively referred to as a pilot signal return component (Pr).

  Further, since the return component of the pilot signal leaked to the outside from the input terminal of the amplifier unit 10 is totally reflected by the BPF 11 in the previous stage, it is input again to the amplifier unit 10 and finally the input point ( It is superimposed on the forward component Pf of the pilot signal at the specified point RP). For this reason, the pilot signal level that should be known (constant) changes. Along with this, the monitor level of the pilot signal after amplification also changes. However, since the pilot signal level at the specified point RP is no longer constant (known), the gain of the amplifier 15 cannot be monitored properly.

Conventionally, by providing the isolators 13A and 13B before and after the coupler 14, the return component of the pilot signal is exclusively reduced. Here, 13B is an isolator for blocking the reflection component Pfr of the pilot signal, and 13A is an isolator for blocking the directional component Pr (+ Pfr) of the pilot signal.
Japanese Patent Laid-Open No. 5-90843

  However, when two isolators that are generally expensive and large in size (for example, 20 × 20 mm) are provided as in the prior art described above, there is a problem in that the cost and the mounting area are increased.

  The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to stabilize the level of a pilot signal (for example, to suppress reflection components) by a method different from the conventional one. Another object of the present invention is to provide an amplifier unit that can stabilize the pilot signal level at the amplifier input and that is inexpensive or downsized.

The amplifier unit according to the first aspect of the present invention synthesizes a pilot signal having a frequency different from that of the main signal via a coupler with the main signal input to the main line via the band-pass filter circuit of the main signal, And an amplifier unit for amplifying the pilot signal by an amplifier, wherein an input port and an output port of the circulator are inserted and connected between the input terminal of the main signal and the input terminal of the coupler, and the isolation port of the circulator and the ground A phase shifter is provided between them , returning to the circulator side via the main line, and the return component of the pilot signal reflected by the bandpass filter circuit and input to the amplifier is directly sent to the amplifier side via the coupler. It is configured to be superimposed on the main component of the input pilot signal at a predetermined phase .

  In the present invention, since the reflection type phase shift circuit is provided between the input terminal of the main signal and the coupler, the return component of the pilot signal is finally phase-adjusted by the reflection type phase shift circuit, and then finally Therefore, the pilot signal level at the specified point can be stabilized at a required (known) set value because it is stably superimposed (synthesized) on the main component of the pilot signal at the input end (specified point) of the amplifier. . Further, since only one circulator is relatively expensive and takes up space, this type of amplifier unit can be provided at a low cost and in a small size.

The amplifier unit according to the second aspect of the present invention synthesizes a pilot signal having a frequency different from that of the main signal via a coupler with the main signal input to the main line via the band-pass filter circuit of the main signal, And an amplifier unit for amplifying the pilot signal by an amplifier, a first circulator having an input port and an output port inserted and connected between an input terminal of the main signal and an input terminal of the coupler, A second circulator having an input port connected to the isolation port, the output port of the second circulator being terminated by a characteristic impedance of a circuit via a band pass filter for the main signal, and the second circulator the phase shifter is provided between the isolation port and the ground, the first through the main line The reflected component of the main signal returning to the circulator side is terminated by the characteristic impedance of the circuit through the band pass filter, and returned to the first circulator side through the main line and reflected by the bandpass filter circuit. Amplifier
In this configuration, the return component of the pilot signal input to is superimposed on the main component of the pilot signal input directly to the amplifier via the coupler at a predetermined phase .

  According to the present invention, as in the case of the pilot signal, the reflected component of the main signal reflected at the input of the amplifier passes through the bandpass filter of the main signal connected to the output port of the second circulator. Therefore, the interference between main signals at the input end (specified point) of the amplifier can be effectively suppressed. Accordingly, the pilot signal level at the input of the amplifier can be stabilized with higher reliability.

In the third aspect of the present invention, an attenuator is provided in series with the phase shifter. Thus, not only the phase of the return component of the pilot signal but also the amplitude can be set as required, so that the pilot signal level at the input of the amplifier can be stabilized with higher accuracy.
The

Preferably, the amplifier unit of the present invention is configured to synthesize a pilot signal having a frequency different from that of the main signal through a coupler with the main signal, and amplify the main signal and the pilot signal by an amplifier. A series circuit composed of a phase shifter and an isolator is provided between the input terminal of the coupler and the input terminal of the coupler.

  In the present invention, most of the return component of the pilot signal is blocked by the isolator, and after the partially leaked return component is phase-adjusted by the phase shifter, the forward component of the pilot signal is finally obtained. Is superimposed on. Therefore, the pilot signal level at the input of the amplifier can be effectively stabilized with a simple configuration.

An amplifier unit according to a fourth aspect of the present invention synthesizes a pilot signal having a frequency different from that of the main signal via a coupler with a main signal input to the main line via a band-pass filter circuit for the main signal, and in the amplifier unit for amplifying the pilot signal by an amplifier, and insert the series circuit connected to the phase shifter and circulator input / output port between the input terminal of the input terminal and the coupler of the main signal, the circulator The isolation component of the main signal is terminated by the characteristic impedance of the circuit through the band pass filter for the main signal, and the reflected component of the main signal returning to the first circulator side through the main line is passed through the band pass filter. Terminate with the characteristic impedance of the circuit and return to the circulator side via the main line, Is reflected by the serial bandpass filter circuit is obtained by configured so as to overlap with the main component in a predetermined phase of the pilot signal the return component of the pilot signal is input directly to the side of the amplifier via the coupler to be input to the amplifier.

  According to the present invention, similar to the pilot signal, the reflection component of the main signal reflected at the input of the amplifier is terminated by the characteristic impedance of the circuit through the bandpass filter of the main signal connected to the output port of the circulator. Therefore, it is possible to effectively suppress interference between main signals at the input end (specified point) of the amplifier. Along with this, the pilot signal level at the input of the amplifier is also stabilized with higher reliability.

In a fifth aspect of the present invention, the phase shifter is a variable phase shifter. Therefore, it is possible to easily cope with various characteristic changes of the amplifier unit such as variations in circuit element parameters and aging.

In a sixth aspect of the present invention, a part of the pilot signal is extracted and detected from the input terminal of the amplifier to detect its signal level, and the comparison signal between the detected signal level and a predetermined value is used to output the signal from the amplifier. A feedback control unit that feedback-controls the variable phase shifter so that the level of the pilot signal at the input end is constant. Therefore, the pilot signal level at the amplifier input can be automatically stabilized.

As described above, according to the present invention, it is possible to stabilize the level of the pilot signal (for example, to suppress the reflection component). Also, an amplifier unit capable of accurately and stably monitoring the gain of the amplifier from the outside can be provided at a low cost and in a small size.

  Hereinafter, a plurality of preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings. FIG. 1 is a circuit diagram of the amplifier unit 10A according to the first embodiment, and adjusts the phase and amplitude of the return component (Pr + Pfr) of the pilot signal and synthesizes it with the principal component Pf of the pilot signal, thereby obtaining the level specified point RP. The case where the level of the pilot signal in is stabilized is shown. In the figure, 11 is a previous band pass filter (BPF) that passes the main signal band, 12 is a pilot signal oscillator, 14 is a coupler (Cup) by a directional coupler, and 15 is a transistor (Tr) as an amplifying element. , 16 is a circulator (Cir), 17 is a voltage-controlled variable phase shifter, and 18 is an attenuator.

  When the pilot signal P of the oscillator 12 is coupled to the main line by the coupler 14, the pilot signal Pf having a fraction of the power appears on the terminal 2 (forward direction) side of the coupler 14 and the terminal 1 (opposite direction). The pilot signal Pr with a power of 1/10 or less of that appears on the () side. Further, a part of the pilot signal Pf traveling in the forward direction is reflected at the input due to the mismatch of the transistor 15, and the reflected component Pfr is combined with the directional component Pr traveling in the reverse direction to become a return component. To output port 2.

  Further, the return component passes through the circulator 16 from the output port 2 to the isolation port 3, passes through the phase shifter 17 and the attenuator 18, and is adjusted in phase and amplitude, and further reflected by the GND. Then, the signal passes through the attenuator 18 and the phase shifter 17 again, and the amplitude and phase thereof are adjusted to return to the isolation port 3 of the circulator 16.

  Further, the return component of the pilot signal leaks outside from the RF input terminal of the amplifier unit 10A, is totally reflected by a mismatch with the BPF 11 in the previous stage, and is re-input to the amplifier unit 10A, and is input from the input port 1 of the circulator 16. The output port 2 and the terminal 1 of the coupler 14 pass through the terminal 2 and reach the level regulation point RP of the pilot signal. At this time, the phase and amplitude of the return component Pr ′ at the level specified point RP can be determined as required by manual adjustment of the control voltage Vcont for the variable phase shifter 17 and setting of the attenuation amount in the attenuator 18. As a result, the pilot signal level at the level defining point RP can be adjusted to a required (known) constant value. That is, it is possible to stabilize the level of the pilot signal by suppressing the reflection component. Further, the amplifier unit 10A according to the first embodiment can be reduced by about 75% in terms of price and 15 to 20% in terms of mounting area compared to the conventional example of FIG.

  An inset (a) shows a circuit diagram of an example variable phase shifter 17. In the figure, PIN diodes D1 and D2 are respectively connected to ports 2 and 3 of a 3 dB branch line coupler (so-called 90 ° hybrid) 17a, each cathode side is grounded, and a bias voltage Vcont applied via an inductance L is applied. By controlling, the internal resistances of the PIN diodes D1 and D2 continuously change in a range of approximately 0 to ∞. As a result, the reflection phase of the pilot signal can be continuously changed. In this configuration, the same amount of phase changes between when the pilot signal passes from the terminal IN to the terminal OUT and when the pilot signal passes from the terminal OUT to the terminal IN.

  In addition, as the variable phase shifter 17, a commercially available modular phase shifter or the like can be used. Further, instead of the PIN diode, a phase shift circuit in which an inductance and a variable capacitance diode (varactor) are connected in series may be used. Although not shown, as the attenuator 18, a commercially available one-chip attenuator or a π-type or T-type attenuator combining a plurality of chip resistors can be used.

  FIG. 2 is a circuit diagram of the amplifier unit 10B according to the second embodiment, and shows a case where the pilot signal level at the level defining point RP can be automatically maintained at a predetermined value. In the figure, 20 is a coupler (directional coupler) in which a stub (so-called λ / 4 plate) having an electrical length ¼ of the pilot signal wavelength λ is coupled to the main line, and 21 is a pilot signal level feedback control unit. , 22 is a detector (DET), and 23 is a comparison control unit. Other configurations may be the same as those described in FIG.

  The coupler 20 extracts a part of the pilot signal at the level specified point RP, and the detector 22 detects the amplitude of the envelope signal. The comparison control unit 23 obtains the average value of the detection output and a preset reference value Vref. Based on the comparison result, the control voltage Vcont is feedback-controlled so that the pilot signal level at the level regulation point RP becomes a required constant value. Thereby, manual adjustment work of the variable phase shifter 17 can be reduced.

  FIG. 3 is a circuit diagram of an amplifier unit 10C according to the third embodiment, and shows a case where the attenuator 18 is omitted from the second embodiment of FIG. Even if the attenuator 18 is deleted, the level of the pilot signal at the level specified point RP can be adjusted as required by adjusting the amount of phase shift of the variable phase shifter 17 as necessary. Note that the control voltage Vcont may be set manually by deleting the feedback control unit 21. The same applies to other embodiments described below.

  FIG. 4 is a circuit diagram of an amplifier unit 10D according to the fourth embodiment. A series circuit including a variable phase shifter and an isolator between a main signal input terminal and a coupler for inserting a pilot signal into the main line. The case where is provided is shown. In the figure, 13 is an isolator (Iso), and 17 is a variable phase shifter.

  According to the fourth embodiment, most of the return component of the pilot signal is blocked by the isolator 13, and after the leaked return component is phase-adjusted by the phase shifter 17, Thus, the signal is superimposed on the forward component Pf of the pilot signal at the input end of the amplifier 15. Therefore, the pilot signal level at the input of the amplifier 15 can be effectively stabilized with a simple configuration.

  Note that the variable phase shifter 17 and the isolator 13 of FIG. In this case, the return component after the phase adjustment of the pilot signal is blocked by the isolator 13, but the same multiplexing effect is obtained at the input point RP of the amplifier 15.

  FIG. 5 is a circuit diagram of an amplifier unit 10E according to the fifth embodiment. The main signal component reflected together with the pilot signal and superimposed on the return component of the pilot signal at the input end of the amplifier 15 is shown in the return path. The case where it terminates by isolation | separation and the characteristic impedance of a circuit is shown. In the figure, 16A and 16B are first and second circulators, 19 is a band pass filter (BPF) that passes only the main signal band, and R0 is a terminating resistor (corresponding to the characteristic impedance of the circuit).

  The input port 1 of the second circulator 16B is connected to the isolation port 3 of the first circulator 16A, and the output port 2 of the second circulator 16B is connected to the termination resistor R0 via the BPF 19, and The connection port 3 is connected to a reflection type phase shift circuit.

  In such a configuration, out of the return component Pr of the pilot signal returning to the output port 2 of the first circulator 16A and the reflection component Sr of the main signal, only the reflection component Sr of the main signal passes through the BPF 19 and the characteristic impedance R0 of the circuit Terminated by On the other hand, the return component Pr of the pilot signal is totally reflected by the BPF 19, is then phase-adjusted by a reflection type phase shift circuit including the variable phase shifter 17, and finally returns to the input terminal RP of the amplifier 15. As a result, only the return component Pr 'of the pilot signal can be superimposed at the input terminal RP of the amplifier 15, so that unnecessary interference due to the reflection component Sr of the main signal can be sufficiently suppressed.

  FIG. 6 is a circuit diagram of an amplifier unit 10F according to the sixth embodiment. A circulator 16 is provided in place of the isolator 13 of FIG. 4, and a band-pass filter that allows only the main signal band to pass through the isolation port 3. A case is shown in which (BPF) 19 is connected and its output is terminated by a characteristic impedance (termination resistor) R0 of the circuit.

  In such a configuration, out of the pilot signal component Pr returning to the output port 2 of the circulator 16 and the reflection component Sr of the main signal, only the reflection component Sr of the main signal passes through the BPF 19 and is terminated by the termination resistor R0. On the other hand, the return component Pr of the pilot signal is totally reflected by the BPF 19, passes through the variable phase shifter 17, is phase-adjusted, and finally returns to the input terminal RP of the amplifier 15. As a result, only the return component Pr 'of the pilot signal can be superimposed at the input terminal RP of the amplifier 15, so that unnecessary interference due to the reflection component Sr of the main signal can be sufficiently suppressed.

  Note that the variable phase shifter 17 in FIG. 6 and the circulator 16 including the termination portion due to the characteristic impedance of the circuit may be interchanged. In this case, the return component after the phase adjustment of the main signal is blocked by the circulator 16, but the same multiplexing effect is obtained at the input point RP of the amplifier 15.

In each of the above embodiments, the variable phase shifter 17 is used. However, the present invention is not limited to this. You may use the fixed type phase shifter which match | combined the amount of phase shift beforehand.

  In the above-described embodiment, the pilot signal frequency having the relationship shown in FIG. 7B is described, but the present invention is not limited to this. There may be another relationship between the band of the main signal and the frequency of the pilot signal.

  Moreover, although several embodiment suitable for the said invention was described, it cannot be overemphasized that the structure of each part, control, a process, and these combination can be variously changed within the range which does not deviate from this invention. .

1 is a circuit diagram of an amplifier unit according to a first embodiment. FIG. FIG. 5 is a circuit diagram of an amplifier unit according to a second embodiment. It is a circuit diagram of the amplifier unit by 3rd Embodiment. It is a circuit diagram of the amplifier unit by 4th Embodiment. FIG. 9 is a circuit diagram of an amplifier unit according to a fifth embodiment. It is a circuit diagram of the amplifier unit by 6th Embodiment. It is a figure explaining a prior art.

Explanation of symbols

10 Amplifier unit 11 Band pass filter (BPF)
12 Oscillator 13 Isolator (Iso)
14,20 Coupler (Cup)
15 Transistor (Tr)
16 Circulator (Cir)
17 Variable phase shifter 18 Attenuator 22 Detector (DET)
23 Comparison control unit

Claims (6)

In an amplifier unit that synthesizes a pilot signal having a frequency different from that of the main signal via a coupler with a main signal input to the main line via a band-pass filter circuit of the main signal, and amplifies the main signal and the pilot signal by an amplifier ,
Inserting and connecting the input port and output port of the circulator between the input terminal of the main signal and the input terminal of the coupler, and providing a phase shifter between the isolation port of the circulator and the ground ,
The return component of the pilot signal that returns to the circulator side through the main line and is reflected by the band-pass filter circuit and input to the amplifier is predetermined as the main component of the pilot signal that is input directly to the amplifier side through the coupler. An amplifier unit configured to overlap in phase . In an amplifier unit that synthesizes a pilot signal having a frequency different from that of the main signal via a coupler with a main signal input to the main line via a band-pass filter circuit of the main signal, and amplifies the main signal and the pilot signal by an amplifier ,
A first circulator in which an input port and an output port are inserted and connected between the input terminal of the main signal and the input terminal of the coupler;
A second circulator having an input port connected to the isolation port of the first circulator,
Terminating the output port of the second circulator with the characteristic impedance of the circuit through a band-pass filter for the main signal, and providing a phase shifter between the isolation port of the second circulator and ground ;
The reflection component of the main signal returning to the first circulator side through the main line is terminated by the characteristic impedance of the circuit through the band-pass filter, and returned to the first circulator side through the main line. The return component of the pilot signal reflected by the bandpass filter circuit and input to the amplifier is superimposed on the main component of the pilot signal input directly to the amplifier side via the coupler in a predetermined phase. An amplifier unit. 3. The amplifier unit according to claim 1, wherein an attenuator is provided in series with the phase shifter. In an amplifier unit that synthesizes a pilot signal having a frequency different from that of the main signal via a coupler with a main signal input to the main line via a band-pass filter circuit of the main signal, and amplifies the main signal and the pilot signal by an amplifier ,
A series circuit in which a phase shifter and an input / output port of a circulator are connected is inserted between the input terminal of the main signal and the input terminal of the coupler, and a band pass filter for the main signal is connected to the isolation port of the circulator. Terminated by the characteristic impedance of the circuit ,
The reflection component of the main signal returning to the first circulator side through the main line is terminated by the characteristic impedance of the circuit through the band pass filter, and returned to the circulator side through the main line, and the band An amplifier characterized in that a return component of a pilot signal reflected by a pass filter circuit and input to the amplifier is superposed with a predetermined phase on a principal component of the pilot signal input directly to the amplifier via the coupler. unit. The amplifier unit according to any one of claims 1 to 4 , wherein the phase shifter is a variable phase shifter. A part of the pilot signal is extracted and detected from the input end of the amplifier to detect its signal level, and the level of the pilot signal at the input end of the amplifier is constant by a comparison output between the detected signal level and a predetermined value. The amplifier unit according to claim 5 , further comprising a feedback control unit that feedback-controls the variable phase shifter so that

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