CN1368642A - Circuit and method for detecting standing wave - Google Patents

Abstract

A circuit and its method for detecting stationary wave includes monolithic processor, bidirectional coupler, module for detecting and magneifying radio-frequency signal. The detecting and magnifying model consists of single pole double throw switch, logarithm wave detector and operational amplifier. Under the control of the monolithic processor, alternately passing through the single pole double throw switch and the bidirectional radio frequency power signal enters the logarithm wave detector and A/D converter, thus the signal is first changed to direct current signal, and then to digital signal. The said digital signal is compared to preset values for giving an alarm by stages. The control of monolithic procesosr, design of single channel and high accuracy logarithm wave detector are adopted in the invention so as to ensure the detecting accuracy in wide range of temperatures. The invented circuit and method have already been used in CDU and WCDMA system in GSM base station successfully.

Description

Standing wave detection circuit and detection method thereof

The invention belongs to wireless communication technology field, specifically is a kind of standing wave detection circuit that is used to the alarm signal that detects the standing-wave ratio (SWR) of antenna-feedback system and export different stage, and based on the method for detecting standing wave of this circuit.

At wireless communication fields such as GSM, the match condition of base station antenna feeder system and high-power emission coefficient directly has influence on the signal transmitting and receiving quality.In fact the standing wave detection technique comes from power detection techniques, and standing wave detection circuit can be divided into detector diode circuit and logarithmic detector modular circuit according to the difference of power-sensing circuit.Existing standing wave detection circuit adopts analogue technique more, promptly adopt detection tube or detection module that radiofrequency signal is converted to analog DC voltage after, again through a series of correction comparison process output standing-wave ratio (SWR) signal, with the protection power amplifier.

The design of existing standing wave detection circuit divides two kinds: adopt mimic channel and single chip circuit.Adopt the standing wave detection ubiquity accuracy of detection of traditional Analog Circuit Design not high, interference free performance is poor.Because of the output voltage of power detection device is nonlinearities change with power input, therefore adopt the circuit of Analog Circuit Design to realize that difficulty is big, the circuit complexity.

Adopt the standing wave detection circuit of single-chip microcomputer design that forward and reverse two-way sense channel are generally arranged at present, if the temperature characterisitic of two-way sense channel is inconsistent, then under different temperatures, accuracy of detection is poor.

The objective of the invention is to overcome the above-mentioned deficiency of prior art, the standing wave detection circuit of wireless communication systems such as a kind of GSM of being used for is provided, and based on the method for detecting standing wave of this circuit.It reports operation maintenance center by the base station with this alarm signal again according to the alarm signal of the size output different stage of the antenna-feedback system standing-wave ratio (SWR) that detects, and guarantees the normal operation of communication apparatus.

The present invention a kind ofly comprises single-chip microcomputer by monolithic processor controlled standing wave detection circuit, it is characterized in that also comprising:

Be placed on the bidirectional coupler between power amplifier output terminal or diplexer and the feeder;

The radio-frequency signal detection amplification module is used for logarithmic detector, amplification to forward and reverse two-way rf power signal of bidirectional coupler coupling;

Two control ends of described single-chip microcomputer connect the switching controls end of the forward and reverse power signal of radio-frequency signal detection amplification module, its input end received RF signal detects the direct current signal of amplification module output, by A/D transducer in its sheet described direct current signal is transformed to digital quantity, and then compares processing, segmentation warning with setting value.

Above-mentioned standing wave detection circuit adopts the single channel design, realizes that under Single-chip Controlling standing wave detects and alarm.Its method for detecting standing wave key step is as follows:

A, under the control of single-chip microcomputer, forward and reverse rf power signal alternately by single-pole double-throw switch (SPDT), enters logarithmic detector and is converted to forward and reverse direct current signal;

B, described forward and reverse direct current signal is transformed into digital signal corresponding, gets its mean value by A/D transducer in the single-chip microcomputer sheet;

C, described forward and reverse digital signal average value subtracted each other obtains return loss value, with the two-stage threshold value of setting relatively, export corresponding alarm signal.

Advantage of the present invention compared with the prior art is as follows:

Make the power basically identical that arrives logarithmic detector by the differential declines amount that forward and reverse attenuator is set, eliminated like this because the error that the logarithmic detector non-linear factor brings.

It is the single channel design at center that standing wave detection circuit adopts single-chip microcomputer, and the utilization AD high precision logarithmic detector AD8313 of company can guarantee the accuracy that detects in very wide temperature range.

On software processes, adopt digital filtering technique elimination noise jamming, and adopt smoothing technique to realize reliable and stable standing wave alarm in a large number.

After tested, this method for detecting standing wave and circuit are alarmed under the various states of GSM signal normally.This standing wave detection circuit successful operation at present is in the merit deciliter unit, road (CDU) of GSM base station.The present invention program has been successfully applied to the standing wave detection of sophisticated signals such as WCDMA in addition.

The present invention is further described below in conjunction with the embodiment accompanying drawing.

Fig. 1 is the standing wave detection circuit theory diagram;

Fig. 2 is its radio-frequency signal detection amplification module schematic diagram;

Fig. 3 is logarithmic detector circuit AD8313 output voltage and power input relation curve;

Fig. 4 is the primary control program process flow diagram.

Fig. 5 is A/D sampling subroutine flow chart;

Fig. 6 is the warning subroutine flow chart.

Shown in standing wave detection circuit theory diagram 1, its first half is a bidirectional coupler, and it is placed between the output terminal or diplexer and feeder of power amplifier, and its effect is the forward and reverse power of coupling, offers standing wave detection circuit and uses.By transmission line theory as can be known: $\mathrm{\ρ}=\frac{1+\left|\mathrm{\Γ}\right|}{1-\left|\mathrm{\Γ}\right|}$ $\left|\mathrm{\Γ}\right|=\frac{\mathrm{\ρ}-1}{\mathrm{\ρ}+1}$

P _F(dBm)-P _R(dBm)=20log (V ₊)-20log (V _-)=20log (V ₊/ V _-P in the 20log of)=-(Γ) formula _FCoupling mechanism forward coupled power

P _RCoupling mechanism reverse coupled power

V ₊Port incident wave voltage

V _-Port reflection wave voltage

Γ port reflection coefficient

ρ: standing-wave ratio (SWR)

By following formula as can be known standing-wave ratio (SWR) only be exponential relationship with forward and reverse difference power, and irrelevant with the size of power input.

Fig. 1 the latter half is radio-frequency signal detection amplification module and single chip part, and the radio-frequency signal detection amplification module is used for logarithmic detector and the amplification to forward and reverse two-way rf power signal of bidirectional coupler coupling.

Radio-frequency signal detection amplification module principle as shown in Figure 2, it is made up of single-pole double-throw switch (SPDT) (SPDT), logarithmic detector (DETECTOR) and operational amplifier (AMP), logarithmic detector is connected between single-pole double-throw switch (SPDT) output terminal and the operational amplifier, and the switching controls end of single-pole double-throw switch (SPDT) is controlled by single-chip microcomputer (MCU).

At first forward and reverse power is input in the logarithmic detector by the switch switching in turn, and logarithmic detector is converted to the DC voltage proportional with power input with the radiofrequency signal of input.Then this aanalogvoltage is amplified and be input in the single-chip microcomputer by operational amplifier, single-chip microcomputer aligns reverse voltage, and to carry out sample conversion be digital signal, and this digital signal is carried out after a series of average calculating operation comparing the specific alarm signal of output with given threshold value.

The Primary Component logarithmic detector of radio-frequency signal detection amplification module adopts the AD8313 logarithmic detector of AD company, and this logarithmic detector has following characteristics:

Broadband character: 0.1GHz～2.5GHz

High dynamic range: 70dB

High precision: ± 1dB (@1.9GHz in the 65dB scope)

Fast response time: 40nS (in full scale)

Wide voltage range :+2.7V～+ 5.5V

Low-power consumption: 40mW (3V)

Logarithmic detector is transformed to DC voltage with rf power signal, the power input of logarithmic detector AD8313-70～-during 10dBm, output voltage is that output voltage is directly proportional with power input between 0.55～1.65V, and AD8313 output voltage and power input relation curve are seen shown in Figure 3.

Operational amplifier adopts LMC6482 rail-rail operational amplifier, its objective is 3 times of logarithmic detector output 0.55～1.65V voltage amplifications, increases the dynamic range of A/D sampling.

Single-pole double-throw switch (SPDT) (SPDT) is used for switching positive and negative two-way rf power signal, and having selected Mini company isolation among the embodiment for use is the SPDT of 48dB, and its model is RSW-2-25P.

Power module is simple relatively, stable+5V DC voltage that this module is used to provide, by the NS company monolithic that the output voltage precision is higher adjustable/fixing+5V linear voltage regulator LM2951 forms.Maximum output current is 100mA, and the voltage accuracy is ± 1.5%.This module needs+8V DC voltage.

Single-chip microcomputer adopts PIC12C671 to be with 8 A/D single-chip microcomputers, and this device is a reduced instruction set computer Harvard structure single-chip microcomputer, and it has following characteristics:

Number of pins is few, and only 8 pin DIP or SOIP encapsulate, and is useful for the place of and saving volume few to I/O mouth quantitative requirement;

Inside contains 8 A/D transducers of 4 passages, and is easy to use;

Built-in Watchdog, 8 frequency counter and timers in advance;

Reduced instruction set computer only has 35 one-byte instructions;

Built-in RC oscillator only need power up the work of getting final product when using built-in oscillator;

Low-power consumption ,≤2mA@5V, 4MHz;

Single chip part is transformed to digital signal with the direct current signal of radio-frequency signal detection amplification module output through ADC, by single-chip microcomputer the signal of A/D sampling is carried out certain processing computing after, the standing wave alarm signal of output two-way COMS level.The switching controls of the single-pole double-throw switch (SPDT) of detection amplification module is by monolithic processor controlled.

Its software main flow as shown in Figure 6.On software design, by the forward and reverse watt level of Single-chip Controlling continuous sampling, and the size of judging forward and reverse power whether in the fixed scope, then the effective numerical value of continuous sampling is averaged processing, after subtracting each other, forward and reverse mean values obtains return loss value, compare processing with the threshold value that sets, export corresponding alarm signal.

Master routine at first carries out system initialization work, and some parameters are set, and then calls A/D sampling subroutine, and whether sampling successfully determines whether to call the warning subroutine according to A/D.

A/D sampling subroutine as shown in Figure 5.This subroutine is finished forward and reverse two paths of signals is taken turns sampling, and whether judgment data is effective, withdraws from after calculating the mean value of 4 continuous samplings then.If continuous sampling to 256 invalid data then withdraws from this subroutine.

Suction parameter:

Suction parameter is global variable, the dynamic range when detecting in order to be provided with, and ripple factor.

CONSTANT??????????POWER_MAX＝0×E0

CONSTANT??????????POWER_MIN＝0×90

CONSTANT??????????MARGIN???＝0×03

Outlet parameter:

Outlet also is a global variable, the BUF_ADFWD register returns forward power value after average, the BUF_ADREV register returns backward power value after average, AD_FAIL_CNT returns the position whether effective marker position of A/D sampling numerical value, it is invalid to return 1 explanation A/D sampling numerical value, it is effective to return numerical value 0 explanation A/D sampling numerical value, and numerical value is placed on respectively in BUF_ADFWD and the BUF_ADREV register.

Function call: this subroutine call Delay time delay subroutine.

This subroutine is at first carried out clear operation to the register of depositing A/D sampling numerical value, and the then positive and negative two-way numerical value of sequential sampling compares with given threshold value, guarantees that power is in the dynamic range of setting.Respectively the numerical value and the preceding once numerical value of sampling of sampling is compared then, it is effective that both differ in given threshold range this numerical value, then with last numerical value addition, after forward and reverse totally 8 samplings of continuous sampling, respectively forward and reverse numerical value is averaged, put into BUF_ADFWD and BUF_ADREV register.When in the dynamic range that the numerical value of being sampled is not setting, with the replacement averaged counter, A/D sampling fail counter subtracts 1, restarts sampling, when A/D sampling fail counter is 0, withdraws from this subroutine.

The warning subroutine as shown in Figure 6.This subroutine is at first subtracted each other forward and reverse numerical value, obtains return loss value, compares with given thresholding then, if the alarm of one-level standing wave then provides Level 1Alarming, if the alarm of secondary standing wave then provides the secondary alarm, as normally then removing all alarms.

Suction parameter:

Suction parameter is global variable.Comprise forward and reverse numerical value and standing-wave ratio (SWR) is set than threshold registers.

VARIABLE?????????????BUF_ADFWD＝20H

VARIABLE?????????????BUF_ADREV＝BUF_ADFWD+1

VARIABLE?????????????REF_VAL15＝BUF_ADREV+1

VARIABLE?????????????REF_VAL30＝REF_VAL15+1

Outlet parameter:

Outlet also is a global variable, for alarming time counter.

VARIABLE?????????????VSWR15_CNT＝AD_RESULT_F2+1

VARIABLE?????????????VSWR30_CNT＝VSWR15_CNT+1

VARIABLE?????????????VS_NOR_CNT＝VSWR30_CNT+1

This subroutine workflow is as follows:

At first calculate return loss, then with given threshold value comparison, if the alarm of secondary standing wave, then turn to the secondary alarming processing, program continuous counter alarm here just is provided with the port alarm for 5 times, in addition, if alarm status is not then operated port identical with the last time next time.Level 1Alarming is the same with the secondary alarming processing, normally then removes all alarm signals.

This standing wave detection circuit leading indicator is as follows:

Radio frequency signal frequency scope: 1805～1880MHz

The dynamic range of detection power: 20dB

Alarming threshold: as shown in the table

Power level	Alarm level	VSWR	?J5	?J6
					＞((26～30)-L)dBm	One-level	1.6～2.5	?H	?L
＞((26～30)-L)dBm	Secondary	＞2.5	?L	?H
					＜((26～30)-L)dBm	Do not have	-	?L	?L

Power consumption: less than 500mW

VSWR veneer total current is 17.5mA.

The selection of VSWR_MARGIN.Currency is 03H.The fluctuating of power level is ± 1dB in a time slot.Then VSWR_MARGIN can be set to 05H in software.

The selection of time constant:

In software control, the time that switches to another AD passage from an AD passage is 50 μ S.Therefore suitable time constant must be selected, just the circuit operate as normal can be made.

Claims (6)

1, a kind of standing wave detection circuit comprises single-chip microcomputer, it is characterized in that also comprising:

Be positioned over the bidirectional coupler between power amplifier output terminal or diplexer and the feeder;

The radio-frequency signal detection amplification module is used for logarithmic detector and amplification to forward and reverse two-way rf power signal of bidirectional coupler coupling;

Two control ends of described single-chip microcomputer connect the switching controls end of the forward and reverse power signal of radio-frequency signal detection amplification module, its input end received RF signal detects the direct current signal of amplification module output, by A/D transducer in its sheet described direct current signal is transformed to digital signal, and then compares processing, segmentation warning with setting value.

2, standing wave detection circuit according to claim 1, it is characterized in that: described radio-frequency signal detection amplification module is made up of single-pole double-throw switch (SPDT), logarithmic detector and operational amplifier, logarithmic detector is connected between single-pole double-throw switch (SPDT) output terminal and the operational amplifier, and the switching controls end of single-pole double-throw switch (SPDT) is by Single-chip Controlling.

3, standing wave detection circuit according to claim 2 is characterized in that: described logarithmic detector adopts the AD8313 circuit.

4, standing wave detection circuit according to claim 2 is characterized in that: described single-pole double-throw switch (SPDT) adopts the RSW-2-25P circuit.

5, standing wave detection circuit according to claim 2 is characterized in that: described operational amplifier adopts LMC6482 rail-rail operational amplifier.

6,, it is characterized in that taking following steps based on the method for detecting standing wave of above-mentioned standing wave detection circuit:

A, under the control of single-chip microcomputer, forward and reverse rf power signal alternately by single-pole double-throw switch (SPDT), enters logarithmic detector and is converted to forward and reverse direct current signal;

B, described forward and reverse direct current signal is transformed into digital signal corresponding, gets its mean value by A/D transducer in the single-chip microcomputer sheet;

C, described forward and reverse digital signal average value subtracted each other obtains return loss value, with the two-stage threshold value of setting relatively, export corresponding alarm signal.

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