CN201219265Y - Automatic gain control device - Google Patents

Abstract

The utility model provides a automatic gain control device, comprising a variable gain amplifier, an analog to digital converter, an average power measurer and an object power comparator connected in turn; an output end of the object power comparator is connected with an input end of the variable gain amplifier; the input first wireless signal is amplified through the variable gain amplifier, then outputs the second wireless signal after converting through the analog to digital converter. The utility model better overcomes effect of the up and down power difference in the TDD system on automatic gain control; the device has simple structure, adopted timing control is comparatively wide, which is easy to realize, a general digital processor is adopted, occupied resource is little.

Description

A kind of automatic gain control equipment

Technical field

The utility model relates to a kind of time division duplex (Time Division Duplex, the TDD) control of the automatic gain in the wireless communication system (Automatic Gain Control, AGC) device of being used for.

Background technology

In wireless communication system, the decline of radio communication channel, shade, multipath effect, and other various factors all can cause the amplitude of received signal and the variation of power, and this variation is extremely not steady, has very big dynamic range.

For because of above-mentioned former thereby cause the received signal that dynamic range is very big, generally can handle by following dual mode: the one, increase analog to digital converter (Analog to Digital Converter, ADC) word length is no more than certain level thereby enlarge the ADC dynamic range with the treatment loss that guarantees large-signal and small-signal; The 2nd, by adjusting receiving gain, large-signal is contracted to or small-signal is amplified to suitable level.This under the condition that does not increase the ADC word length, the technology that the signal of great dynamic range is adjusted into automatically the signal that is suitable for the ADC small dynamic range is referred to as automatic gain control.The signal of small dynamic range is lower for the design and the realization requirement of receiving filter, thereby has reduced the cost of whole receiver.Mode one is processed into original guaranteed performance by increase, and the word length that increases will improve the complexity of subsequent treatment, has limited its application like this.And two of modes need functional module of increase just can make full use of the existing resource of handling, thereby have reduced the realization cost, thereby have obtained using widely.

In the TDD system, following situation has proposed new challenge for automatic gain control.

As shown in Figure 1, be that an employing comprises the frame structure schematic diagram that can be used for the uplink and downlink communication time slot respectively in the TDD communication system.In the received signal frame structure of TDD system, the performance number phase missionary society between the uplink and downlink timeslot is very big.For example, in time-division-synchronization code multi-address division system TD-SCDMA, (User Equipment, UE) the phase difference can reach dozens of decibel (dB) for user terminal.

Do not set up as yet under the synchronous situation at user terminal, this UE still can't distinguish the downlink synchronous signal of base station transmission and the uplink and downlink signals of contiguous UE.The uplink synchronizing signals that particularly contiguous UE sends is compared the descending common signal that the base station sends with the uplink service signal power can be very big, and the reception of downlink synchronous signal has been caused very big interference.

Above-mentioned factor will cause received signal amplitude and power in a time period (a for example frame) violent variation to be arranged, and very big dynamic range is promptly arranged.In traditional automatic gain control usually through new gain more after the some cycles.Therefore, when variable power is very big, among the signal of the great dynamic range input ADC.Large-signal will make ADC saturated and small-signal ADC can't represent, cause the precise decreasing of ADC, influence receptivity even cause can't setting up or interrupt of communication.

In addition, the scheme that adopts in the most of TDD system is the signal that the corresponding time slot of next frame is controlled in the gain that utilizes previous frame time slot calculated signals to go out.Yet before receiver does not have to obtain synchronously the original position that can't determine time slot.If the power difference is very big between the interior different time-gap of frame length scope, when the average power of down-going synchronous/pilot signal that the average power of especially whole data segment and receiver need detect differs greatly, the receiving gain that calculates according to whole data segment will be not suitable for the downlink synchronous signal of required detection, thereby have a strong impact on the reception to down-going synchronous/pilot signal.

The utility model content

The purpose of this utility model is to provide a kind of automatic gain control equipment that is used for the TDD radio communication system receiver, this device can make very big and do not set up as yet under the synchronous situation at uplink and downlink timeslot power, suitable gain is provided for the signal that will receive, thus make communication system normal set up synchronous with communicate by letter.

For achieving the above object, the invention provides a kind of automatic gain control equipment, it comprises the variable gain amplifier of circuit connection successively, analog to digital converter, average power measuring appliance and target power comparator;

The output of described target power comparator connects the input of described variable gain amplifier;

First wireless signal of input amplifies through described variable gain amplifier, again output second wireless signal after analog to digital converter transforms;

Described average power measuring appliance calculates average power to second wireless signal in the section sometime;

Described target power comparator calculates the difference of this average power and predeterminated target power, and this difference is done digital processing, produces the control signal that acts on the yield value of next frame corresponding to this time period.

The automatic gain control equipment of the TDD radio communication system that the utility model provides can overcome the influence that up and down power difference is controlled for automatic gain in the TDD system well; This apparatus structure is simple, and the timing controlled of employing is looser, is easy to realize, can adopt general digital processing unit, takies resource seldom.

Description of drawings

Fig. 1 is in the TDD communication system, adopts to comprise a frame structure schematic diagram that can be used for the uplink and downlink communication time slot respectively;

Fig. 2 is the circuit block diagram of this reality and novel device.

Embodiment

Following according to Fig. 2, be example with the TD-SCDMA system, a better embodiment of the present utility model is described.

As shown in Figure 2: be the circuit block diagram of automatic gain control equipment of the present utility model, this device comprises the variable gain amplifier 313 and the analog to digital converter 314 of circuit connection successively, and described first wireless signal 301 is output second wireless signal 315 after variable gain amplifier 313 amplifications and analog to digital converter 314 conversions.

Described segmentation automatic gain control equipment 31 also comprises with lower member:

Average power measuring appliance 316 to section sometime, calculates the average power of second wireless signal 315; Concrete formula is:

$P\left(i\right)=\frac{1}{N}\underset{k\∈P}{\mathrm{\Σ}}({\left\{I\left(k\right)\right\}}^2+{\left\{Q\left(k\right)\right\}}^2)$

P in the formula (i) is the average power of i time period; P is the sample set of power calculation; N is the element number of sample set; I and Q are quadrature demodulated signals;

Target power comparator 317 calculates this average power P (i) and predeterminated target power P _TargetDifference, and this difference done digital processing, produce the control signal 318 that acts on the yield value of next frame corresponding to this time period;

Described calculating average power and predeterminated target power poor, concrete formula is:

$\mathrm{\ϵ}\left(i\right)=\sqrt{\frac{P_{t\arg \mathrm{et}}}{P\left(i\right)}}$

ε in the formula (i) is the poor of i time period power and predeterminated target power, P _TargetBe the predeterminated target power of system;

The described concrete formula that this difference is done digital processing is:

${\mathrm{\&epsiv;}}^{\&prime;}\left(i\right)=\left\{\begin{array}{cc}{\mathrm{\&epsiv;}}_{\mathrm{high}}& \mathrm{\&epsiv;}\left(i\right)>{\mathrm{\&epsiv;}}_{\mathrm{high}}\\ \mathrm{\&epsiv;}\left(i\right)& {\mathrm{\&epsiv;}}_{\mathrm{low}}\&le;\mathrm{\&epsiv;}\left(i\right)\&le;{\mathrm{\&epsiv;}}_{\mathrm{high}}\\ {\mathrm{\&epsiv;}}_{\mathrm{low}}& \mathrm{\&epsiv;}\left(i\right)<{\mathrm{\&epsiv;}}_{\mathrm{low}}\end{array}\right.$

ε ' is the poor of i time period power after handling and predeterminated target power (i) in the formula, ε _HighAnd ε _LowIt is the parameter of Processing Algorithm.

The automatic gain control equipment that the utility model provides can overcome the influence that up and down power difference is controlled for automatic gain in the TDD system well; This apparatus structure is simple, and the timing controlled of employing is looser, is easy to realize, can adopt general digital processing unit, takies resource seldom.

Claims (1)

1, a kind of automatic gain control equipment is characterized in that, comprises the variable gain amplifier of circuit connection successively, analog to digital converter, average power measuring appliance and target power comparator;

The output of described target power comparator connects the input of described variable gain amplifier;

First wireless signal of input amplifies through described variable gain amplifier, again output second wireless signal after analog to digital converter transforms;

Described average power measuring appliance calculates average power to second wireless signal in the section sometime;

Described target power comparator calculates the difference of this average power and predeterminated target power, and this difference is done digital processing, produces the control signal that acts on the yield value of next frame corresponding to this time period.

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