CN113037306A

CN113037306A - Amplitude limiting protection circuit of RRU receiver and RRU receiver

Info

Publication number: CN113037306A
Application number: CN201911364257.4A
Authority: CN
Inventors: 赵超亚; 任丽达
Original assignee: Chengdu TD Tech Ltd
Current assignee: TD Tech Chengdu Co Ltd; Chengdu TD Tech Ltd
Priority date: 2019-12-25
Filing date: 2019-12-25
Publication date: 2021-06-25

Abstract

The embodiment of the invention provides a limiting protection circuit of an RRU (remote radio unit) receiver and the RRU receiver, wherein the circuit comprises a diode group, the diode group is connected in parallel to the front end of an LNA (low-noise amplifier) of the RRU receiver, the diode group comprises a first PIN diode and a second PIN diode, the first PIN diode is arranged in a reverse bias mode, and the second PIN diode is arranged in a forward bias mode. When an abnormal high-power signal is injected into the receiver, the PIN diode is in a conducting state, the front end of the receiver presents a short-circuit surface of a transmission line, and impedance is seriously mismatched, so that most of power is reflected, only a small power signal is transmitted to a rear stage, the receiver is protected, and the LNA is prevented from being burnt; and the diodes adopt a parallel design of positive bias and reverse bias, and no matter the radio frequency signal is in a positive half shaft or a negative half shaft of voltage, one diode is in a conducting state, the bidirectional peak value of the radio frequency signal is limited within a certain range, and the protection reliability of the receiver is high.

Description

Amplitude limiting protection circuit of RRU receiver and RRU receiver

Technical Field

The embodiment of the invention relates to the technical field of communication, in particular to an amplitude limiting protection circuit of an RRU (radio remote unit) receiver and the RRU receiver.

Background

A Remote Radio Unit (RRU) is a novel distributed network coverage mode, a large-capacity macro-cellular base station is centrally placed in an available central machine room, a baseband part is centrally processed, a Radio frequency module in the base station is pulled to a Remote Radio frequency Unit by adopting optical fibers and is respectively placed on a station determined by network planning, so that a large number of machine rooms required by a conventional solution are saved, and simultaneously, a large number of optical fiber removals are supported by a large-capacity macro base station, so that conversion between capacity and coverage can be realized.

When the traditional RRU is used for networking in scenes such as a track, an antenna (special for a private network) is shared through a bridge or a power divider. The RRU clock is abnormal due to Common Public Radio Interface (CPRI) flash, or the A/B network is respectively connected with a non-communicated Base Band Unit (BBU) and the BBU clocks have different problems, thus the RRU receiving and transmitting switches of the A/B network are not synchronous; the near side of the bridge is provided with a large standing wave point, and the isolation of the bridge is deteriorated under the mismatch condition; when the above conditions occur simultaneously, an abnormal high-power signal is injected into the RRU receiving end, and a Low Noise Amplifier (LNA) is burned out.

The traditional solutions are: LNA balanced design, TDD switch active control, use limiter.

For example, as shown in fig. 1, fig. 1 is a block diagram of LNA balance design, a 3dB bridge is used to divide Input signals into two paths, which are respectively connected to a matching network + LNA + matching network, and then the 3dB bridge is used to combine the signals, so as to finally achieve the purpose of increasing the maximum Input level of 3dB by outputting the signals. However, the layout area of the scheme is limited, the cost is high, and the maximum input level increase is limited.

Fig. 2 is an active control block diagram of a TDD switch, which requires a wave-building and control circuit between the TDD switch and a circulator. When the wave-building circuit detects a high-power signal, the TDD switch is switched from a receiving state to a transmitting state to protect the receiver, specifically, the drawing includes standing wave detection, original switch control, and the like. However, the scheme has more devices, high cost and complex control.

In addition, an encapsulated limiter is used at the front end of the receiver, but the existing limiter has high price and inconsistent performance, and cannot be flexibly debugged according to requirements to meet various scenes.

Disclosure of Invention

The embodiment of the invention provides a limiting protection circuit of an RRU (radio remote unit) receiver and the RRU receiver, which are used for overcoming at least one problem.

In a first aspect, an embodiment of the present invention provides a clipping protection circuit for an RRU receiver, including a diode group, where the diode group is connected in parallel to a front end of an LNA of the RRU receiver, and the diode group includes a first PIN diode and a second PIN diode, where the first PIN diode is set in a reverse bias mode, and the second PIN diode is set in a forward bias mode.

In a possible design, the above circuit further includes a circuit match, the circuit match is connected in parallel with the diode set, and the circuit match is used for forming a resonance with the diode set, and the frequency of the resonance is equal to the center frequency of the RRU receiver.

In a possible design, the circuit further includes a capacitor bank connected in series with the diode bank, and the capacitor bank is used for isolating the voltage flowing into the diode bank.

In a possible design, the number of the diode groups is multiple, and each diode group is connected in parallel to the front end of the LNA of the RRU receiver.

In a possible design, the diode group further includes one or more first PIN diodes and one or more second PIN diodes, wherein the first PIN diodes are sequentially connected in series and then connected to the circuit in a forward direction, the second PIN diodes are sequentially connected in series and then connected to the circuit in a reverse direction, and the number of the first PIN diodes in the diode group is equal to the number of the second PIN diodes.

In one possible design, the circuit matching includes a first inductor and a second inductor, the first inductor is connected in parallel to one end of the diode group, and the second inductor is connected in parallel to the other end of the diode group.

In one possible design, the capacitor bank includes a first capacitor connected in series to one end of the diode bank and a second capacitor connected in series to the other end of the diode bank.

In one possible design, the first capacitor and the second capacitor are both dc blocking capacitors.

In a second aspect, an embodiment of the present invention provides a method for debugging a clipping protection circuit, which is based on the above first aspect and various possible designs of the clipping protection circuit of an RRU receiver.

In a third aspect, an embodiment of the present invention provides an RRU receiver, which includes the clipping protection circuit of the RRU receiver according to the first aspect and various possible designs of the first aspect.

The amplitude limiting protection circuit of the RRU receiver and the RRU receiver provided in this embodiment include a diode group, the diode group is connected in parallel to the front end of the LNA of the RRU receiver, the diode group includes a first PIN diode and a second PIN diode, the first PIN diode is arranged in a reverse bias manner, and the second PIN diode is arranged in a forward bias manner, so that when the receiver normally works, a received signal is small, the PIN diodes all present a high resistance state, and the signal can be smoothly transmitted to the rear stage, when an abnormally high power signal is injected into the receiver, the PIN diodes present a conduction state, the front end of the receiver presents a short circuit surface of a transmission line, and the impedance is severely mismatched, so that most of the power is reflected back, only a small power signal is transmitted to the rear stage, thereby protecting the receiver and avoiding burning the LNA, and because the PIN diodes in the circuit adopt a parallel design of a forward bias and a reverse bias, therefore, no matter the radio frequency signal is in a positive half shaft or a negative half shaft of the voltage, a PIN diode is in a conducting state, the bidirectional amplitude limiting can perfectly limit the bidirectional peak value of the radio frequency signal within a certain range, and the protection reliability of a receiver is high.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic diagram of a conventional balanced LNA design;

FIG. 2 is a schematic diagram of the active control of a conventional switch;

fig. 3 is a schematic diagram of an amplitude limiting protection circuit of an RRU receiver according to an embodiment of the present invention;

fig. 4 is a schematic diagram of an amplitude limiting protection circuit of another RRU receiver according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a clipping protection circuit of an RRU receiver according to another embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terms "first," "second," "third," "fourth," and the like in the description and in the claims, as well as in the drawings, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

When RRU is in scenes such as a track and the like, the networking design is carried out, and an antenna (special for a private network) is shared through a bridge or a power divider; the RRU clock is abnormal due to CPRI flash, or the A/B network is respectively connected with a non-connected BBU and the BBU clocks have different problems, so that the RRU receiving and sending switches of the A/B network are not synchronous; the bridge has a large standing wave point near the bridge, and the bridge isolation is deteriorated under the condition of mismatch. When the above conditions occur simultaneously, the RRU receiving end is caused to have abnormally high power signal injection, and the LNA is burnt out.

Therefore, in view of the above problems, the present invention provides a limiting protection circuit for an RRU receiver, a core device of the circuit is a PIN diode (PIN diode), the PIN diode exhibits an impedance characteristic of approximately on or off under forward and reverse bias voltages, and the PIN diode is connected in parallel to a main signal path of a front end of the receiver by using the characteristic. When the radio frequency signal is small, the pin diode is not enough to be positively biased, the pin diode presents a high-resistance state, the transmission line is well matched, the radio frequency signal is smoothly transmitted, and the attenuation is extremely small (within 0.5 dB); when the radio frequency signal is large, the pin diode is conducted in a forward bias mode to form a short-circuit surface of the transmission line, impedance is seriously mismatched, most of power is reflected, only a signal with certain power is transmitted to a lower level, and therefore the function of protecting the receiver against high-power burning is achieved. Among them, the PIN diode is a crystal diode constructed by sandwiching a layer of an intrinsic semiconductor (or a semiconductor with a low concentration of impurities) between a P region and an N region. I in PIN is the english abbreviation in the sense of "intrinsic". When its operating frequency exceeds 100MHz, its diode loses rectification due to the storage effect of minority carriers and the transit time effect in the "intrinsic" layer to become an impedance element, and its impedance value changes with the bias voltage. The impedance of the "intrinsic" region is high at zero bias or dc reverse bias; when forward biased by a direct current, the "intrinsic" region assumes a low resistance state due to carrier injection into the "intrinsic" region. Therefore, the PIN diode can be used as a variable impedance element. It is often applied to circuits such as high frequency switching (i.e. microwave switching), phase shifting, modulation, amplitude limiting, etc.

The amplitude limiting protection circuit of the RRU receiver provided by the embodiment of the present invention may include: the diode group is connected to the front end of an LNA of the RRU receiver in parallel and comprises a first PIN diode and a second PIN diode, wherein the first PIN diode is arranged in a reverse bias mode, and the second PIN diode is arranged in a forward bias mode.

The forward bias of the diode means that forward bias is applied to the diode, namely, the anode of the diode is connected with high level, the cathode of the diode is connected with low level, and the diode is conducted at the moment. Reverse bias is opposite, the high level is connected with the cathode of the diode, the low level is connected with the anode of the diode, and the diode is cut off. The first PIN diode is reversely biased, and the second PIN diode is positively biased, namely, the anode of the first PIN diode and the cathode of the second PIN diode are respectively grounded, and the cathode of the first PIN diode and the anode of the second PIN diode are respectively connected to the front end of the LNA of the RRU receiver.

The type, type and the like of the first PIN diode and the second PIN diode can be selected according to actual conditions.

Optionally, the above circuit further comprises a circuit match, the circuit match is connected in parallel with the diode group, the circuit match is used for forming a resonance with the diode group, and the frequency of the resonance is equal to the center frequency of the RRU receiver.

Optionally, the circuit matching includes a first inductor and a second inductor, the first inductor is connected to one end of the diode set in parallel, and the second inductor is connected to the other end of the diode set in parallel

Here, an inductor is connected in parallel to the diode group for matching the diode group impedance and optimizing the insertion loss. The type, type and the like of the first inductor (second inductor) can also be selected according to actual conditions.

Optionally, the circuit further includes a capacitor bank connected in series with the diode bank, and the capacitor bank is configured to isolate a voltage flowing into the diode bank.

Optionally, the capacitor bank includes a first capacitor and a second capacitor, the first capacitor is connected in series to one end of the diode bank, and the second capacitor is connected in series to the other end of the diode bank.

Optionally, the first capacitor and the second capacitor are both blocking capacitors.

Here, a capacitor is connected in series across the diode group to serve as a voltage isolation. As above, the type, etc. of the first capacitor (second capacitor) may also be selected according to actual situations.

Fig. 3 is a schematic diagram of an amplitude limiting protection circuit of an RRU receiver according to an embodiment of the present invention, and as shown in fig. 3, a core of the circuit is a pin diode group, where the pin diode group includes a pin diode _ 1-and a pin diode _1+, that is, the pin diode group is composed of 2 pin diodes, a forward bias is placed in parallel in the circuit, and a reverse bias is placed in parallel in the circuit. The two capacitors C1 and C2 are respectively connected in series at two ends of the circuit to play a role in isolating voltage. The two inductors L1 and L2 are arranged on two sides of the pin diode in a left-right adjacent mode to match the impedance of the pin diode, and are suitable for limiting frequency bands. In the figure, PIN _ diode represents a PIN diode, L represents an inductance, C represents a capacitance, PIN represents a signal input terminal, and Pout represents a signal output terminal.

When the receiver normally works, the received signal is very small, the pin diode is in a high-resistance state, and the signal can be smoothly transmitted to the rear stage. When an abnormal high-power signal is injected into the receiver, the pin diode is in a conducting state, the front end of the receiver presents a short-circuit surface of the transmission line, impedance is seriously mismatched, most power is reflected, only a small power signal is transmitted to the rear stage, and then the receiver is protected. And because the pin diode in the amplitude limiting protection circuit adopts a parallel design of positive bias and reverse bias, one pin diode is in a conducting state no matter the radio frequency signal is in a positive half shaft or a negative half shaft of voltage. The bidirectional amplitude limiting can perfectly limit the bidirectional peak value of the radio frequency signal within a certain range, and the protection reliability of the receiver is high.

Note here that the forward and reverse biased pin diodes are to be top-designed in layout so that the two pin diodes are at both ends of the main signal, respectively.

Specifically, the prior art problems and the adopted technical solutions solved by the present embodiment are shown in the following table.

Another limitation protection circuit for an RRU receiver according to an embodiment of the present invention includes a plurality of diode groups, each diode group is connected in parallel to a front end of an LNA of the RRU receiver, and each diode group includes a first PIN diode and a second PIN diode. The first PIN diode is arranged in a reverse bias mode, and the second PIN diode is arranged in a forward bias mode.

Specifically, the withstand power can be improved by the following method in addition to the selected pin diode characteristic:

the tolerance power can be effectively increased by increasing the number of positive and negative bias pin diode groups (including two positive bias and negative bias pin diodes), but the Noise coefficient (Noise figure, NF for short) is doubled when one more pin diode group is introduced, for example, one group of limiting tubes NF is NF0, and n groups of limiting tubes NF is about n × NF 0. Therefore, when the NF is introduced, the influence of NF is comprehensively considered. When using this method, it is furthermore noted that the layout is as compact as possible, while the matching inductance is in close proximity to the pin diode.

Optionally, the circuit further comprises a circuit match connected in parallel with the diode set, the circuit match configured to form a resonance with the diode set, the resonance having a frequency equal to a center frequency of the RRU receiver.

Optionally, the circuit matching includes a third inductor and a fourth inductor, the third inductor is connected to one end of the diode group after all the diode groups are connected in parallel, and the fourth inductor is connected to the other end of the diode group after all the diode groups are connected in parallel.

Optionally, the circuit further comprises a capacitor bank connected in series with the diode bank, the capacitor bank being configured to isolate a voltage flowing into the diode bank.

Optionally, the capacitor bank includes a third capacitor and a fourth capacitor, the third capacitor is connected in series to one end of the diode bank after all the diode banks are connected in parallel, and the fourth capacitor is connected in series to the other end of the diode bank after all the diode banks are connected in parallel.

Fig. 4 is a schematic diagram of another clipping protection circuit of an RRU receiver according to an embodiment of the present invention, as shown in fig. 4, a core of the circuit is a plurality of pin diode groups, that is, pin diode _1-, pin diode _1+, pin diode _2-, pin diode _2+ … … pin diode _ n-, pin diode _ n +, each group of pin diode consists of 2 pin diodes, a forward bias is placed in parallel in the circuit, and a reverse bias is placed in parallel in the circuit. The two capacitors C1 and C2 are respectively connected in series at two ends of the circuit to play a role in isolating voltage. The two inductors L1 and L2 are arranged on two sides of the pin diode in a left-right adjacent manner to match the impedance of the pin diode, and are suitable for limiting frequency bands.

Fig. 5 is a diagram of a further amplitude limiting protection circuit of an RRU receiver according to an embodiment of the present invention, which includes a diode group, where the diode group further includes one or more first PIN diodes and one or more second PIN diodes, where the first PIN diodes are sequentially connected in series, the second PIN diodes are sequentially connected in series, and the number of the first PIN diodes in the diode group is equal to the number of the second PIN diodes. The first PIN diodes are sequentially connected in series and then are connected into the circuit in a forward direction, and the second PIN diodes are sequentially connected in series and then are connected into the circuit in a reverse direction.

Specifically, in order to reduce the NF of the clipping protection circuit of the RRU receiver, two pin diodes may be connected in series in the same direction, and then when the circuits are connected in forward bias and reverse bias respectively, the NF is expected to be reduced by 1/2. But this affects the clipped output level by about 6 dB. At this point it should be noted that the two serial pin diode contact pads are required to dissipate heat.

Optionally, the circuit further comprises a circuit match connected in parallel with the diode group, the circuit match configured to form a resonance with the diode group, the resonance having a frequency equal to a center frequency of the RRU receiver

Optionally, the circuit matching includes a fifth inductor and a sixth inductor, the fifth inductor is connected to one end of the diode set in parallel, and the sixth inductor is connected to the other end of the diode set in parallel.

Optionally, the capacitor bank includes a fifth capacitor and a sixth capacitor, the fifth capacitor is connected in series to one end of the diode bank, and the sixth capacitor is connected in series to the other end of the diode bank.

As shown in fig. 5, the core of the circuit is a group of pin diodes, i.e., pin diode _1-, pin diode _1+, pin diode _2-, and pin diode _2+, each group of pin diodes consisting of 2 pin diodes, with a forward bias placed in parallel in the circuit and a reverse bias placed in parallel in the circuit. The two capacitors C1 and C2 are respectively connected in series at two ends of the circuit to play a role in isolating voltage. The two inductors L1 and L2 are arranged on two sides of the pin diode in a left-right adjacent manner to match the impedance of the pin diode, and are suitable for limiting frequency bands.

In summary, when designing the amplitude limiting protection circuit of the RRU receiver, the optimum balance point can be selected according to the relationship among the withstand power, NF, and the amplitude limiting output level.

The amplitude limiting protection circuit of the RRU receiver is simple, small in layout area, low in cost and high in reliability.

The embodiment of the invention provides a debugging method of an amplitude limiting protection circuit, which is used for debugging the amplitude limiting protection circuit of an RRU receiver based on various possible designs.

The embodiment of the invention provides an RRU receiver, which comprises the amplitude limiting protection circuit of the RRU receiver with various possible designs.

In the embodiments provided in the present invention, it should be understood that the disclosed circuit may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or modules, and may be in an electrical, mechanical or other form.

The modules described as separate parts may or may not be physically separate, and parts displayed as modules may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The amplitude limiting protection circuit of the RRU receiver is characterized by comprising a diode group, wherein the diode group is connected in parallel to the front end of a Low Noise Amplifier (LNA) of the RRU receiver, and comprises a first PIN diode and a second PIN diode, wherein the first PIN diode is arranged in a reverse bias mode, and the second PIN diode is arranged in a forward bias mode.

2. The circuit of claim 1, further comprising a circuit match in parallel with the set of diodes, the circuit match configured to form a resonance with the set of diodes, the resonance having a frequency equal to a center frequency of the RRU receiver.

3. The circuit of claim 1, further comprising a capacitor bank in series with the diode bank, the capacitor bank for isolating a voltage flowing into the diode bank.

4. The circuit of claim 1, wherein the number of the diode groups is plural, and each of the diode groups is connected in parallel to an LNA front end of the RRU receiver.

5. The circuit of claim 1, wherein the diode bank further comprises one or more first PIN diodes and one or more second PIN diodes, wherein the first PIN diodes are serially connected in sequence and then connected in a forward direction into the circuit, the second PIN diodes are serially connected in sequence and then connected in a reverse direction into the circuit, and the number of the first PIN diodes in the diode bank is equal to the number of the second PIN diodes.

6. The circuit of claim 2, wherein the circuit match comprises a first inductor and a second inductor, the first inductor coupled in parallel to one end of the diode bank, and the second inductor coupled in parallel to the other end of the diode bank.

7. The circuit of claim 3, wherein the bank of capacitors comprises a first capacitor and a second capacitor, the first capacitor being coupled in series to one end of the bank of diodes, the second capacitor being coupled in series to the other end of the bank of diodes.

8. The circuit of claim 7, wherein the first capacitor and the second capacitor are both dc blocking capacitors.

9. A method for debugging a clipping protection circuit, wherein the method is performed based on the clipping protection circuit of the RRU receiver of any one of claims 1 to 8.

10. An RRU receiver comprising the clipping protection circuitry of the RRU receiver of any of claims 1 to 8.