CN203504504U

CN203504504U - Automatic gain control (AGC) intermediate frequency amplifier

Info

Publication number: CN203504504U
Application number: CN201320566369.XU
Authority: CN
Inventors: 蒋礼平
Original assignee: Guizhou Aerospace Electronic Technology Co Ltd
Current assignee: Guizhou Aerospace Electronic Technology Co Ltd
Priority date: 2013-09-12
Filing date: 2013-09-12
Publication date: 2014-03-26
Anticipated expiration: 2023-09-12

Abstract

The utility model discloses an automatic gain control (AGC) intermediate frequency amplifier. In a signal line, a pre-amplification module, two cascaded AGC amplifiers and a final stage amplification module are connected in series in order; VGA chips are employed by the two AGC amplifiers, two matching network modules are connected in series between the two cascaded AGC amplifiers and the pre-amplification module, and a matching network module is connected in series between a signal input terminal and the pre-amplification module. When receiving weak signals, the AGC intermediate frequency amplifier amplifies useful signals to the maximum gain; when receiving strong signals, the AGC intermediate frequency amplifier can compress the gain and the amplitude of signals is not limited, and the signals are undistorted; serving as an important part of a radio fuse receiver, the AGC intermediate frequency amplifier reaches main technical parameters such as broadband, high gain, wide dynamic scope, low noise and the like, the automatic gain control scope of the AGC intermediate frequency amplifier is more than 80 dB, and the wide dynamic scope requirement of a receiving system is satisfied.

Description

A kind of AGC intermediate frequency amplifier

Technical field

The utility model relates to a kind of AGC intermediate frequency amplifier.

Background technology

Air-to-air missile (AAM) because required detection of a target radar area difference is large, play order intersection distance range wide, so the input end signal level of receiver may in very large range change without electric wire fuse.For making to obtain under various encounter conditionses the signal detection quality of high-fidelity, fuse receiver needs the amplifier of broadband great dynamic range, and compression of dynamic range is to realize by adopting automatic gain to control (AGC) circuit conventionally.

When processing the vision signal of electronic fuse, this signal spectrum complex structure, it is a lot of that maximum amplitude but differs, when guaranteeing to receive signal bandwidth, need be adjusted accordingly the gain of amplifier, but in prior art when using band automatic gain to control the adaptive amplifier of (AGC), often because making full use of such amplifier gain, control the good linear characteristic of curve interlude, and the saturated and loss of data that occurs measuring channel, thereby the output signal distortion after amplification caused.

Utility model content

For solving the defect existing in prior art, the utility model provides a kind of AGC intermediate frequency amplifier, this AGC intermediate frequency amplifier is by adopting two-stage cascade mode dynamic range expanded, can effectively guarantee that electronic fuse receiver is when the input vision signal power that to receive that the strong and the weak differ greatly larger, the output signal after amplification is undistorted.

The utility model is achieved by the following technical programs:

An AGC intermediate frequency amplifier, is characterized in that: on signal line, AGC amplifier, the final stage amplification module of pre-amplifying module, two-stage cascade are connected successively; Two-stage AGC amplifier adopts VGA chip.

Described pre-amplifying module adopts low-noise wide-band amplifier.

In described two-stage AGC amplifier, the first order works in VGA mode, and the second level works in AGC mode.

On the control voltage circuit of described two-stage AGC amplifier, be in series with filter circuit module.

On signal line, in the AGC amplifier of two-stage cascade and pre-amplifying module, be in series with two-stage matching network module, in signal input part and pre-amplifying module, be in series with a matching network module.

The beneficial effects of the utility model are: while guaranteeing to receive weak signal, can maximum gain amplify useful signal, receive strong signal, can guarantee not amplitude limit, undistorted of signal by compression gains; As part and parcel in electronic fuse receiver, reached the key technical indexes such as broadband, high-gain, great dynamic range, low noise, its AGC control range, more than 80dB, has met the requirement of receiving system great dynamic range.

Accompanying drawing explanation

Fig. 1 is theory diagram of the present utility model;

Fig. 2 is that the voltage gain of VGA chip in the utility model is controlled curve;

Fig. 3 is the voltage indicator diagram of input signal RSSI in the utility model;

Embodiment

Below in conjunction with accompanying drawing, further describe the technical solution of the utility model, but described in claimed scope is not limited to.

A kind of AGC intermediate frequency amplifier as shown in Figure 1, on signal line, AGC amplifier, the final stage amplification module of pre-amplifying module, two-stage cascade are connected successively; Two-stage AGC amplifier adopts VGA chip.

Described pre-amplifying module adopts low-noise wide-band amplifier.

Be illustrated in figure 2 voltage and the gain relationship curve chart of the VGA chip that in the utility model, AGC amplifier adopts, according to the GAIN(Y in LOMODE curve in figure) and available formula 1 expression of relation VGAIN(X):

Y=45-50X （1）

And for example Figure 3 shows that in the utility model according to incoming signal level (a) and received signal strength indicator figure, therefore can represent with formula 2:

X=a/50+1.1 （2）

Received signal strength indicator (b) is AGC and controls voltage VGAIN(X), substitution above formula can obtain incoming signal level (a) and gain G AIN(Y) pass be formula 3:

Y=-a-10 （3）

By formula 1, formula 2 and formula 3, can calculate relation that input signal and output signal change as table 1:

Sequence number	Incoming level (dBV)	Overall gain (dB)	Output signal merit (dBV)	Remarks
					1	-94dBV（20μV）	84dB	-10dBV（316mV）	Mean allocation two stage gains
2	-80dBV（100μV）	70dB	-10dBV（316mV）	Mean allocation two stage gains
					3	-70dBV（316μV）	60dB	-10dBV（316mV）	Mean allocation two stage gains
4	-60dBV（1mV）	50dB	-10dBV（316mV）	Mean allocation two stage gains
					5	-50dBV（3.16mV）	40dB	-10dBV（316mV）	20dB gain two-stage mean allocation
6	-40dBV（10mV）	30dB	-10dBV（316mV）	10dB gain two-stage mean allocation
					7	-34dBV（20mV）	24dB	-10dBV（316mV）	4dB gain two-stage mean allocation
8	-30dBV（100mV）	20dB	-10dBV（316mV）	Two-stage all output out of control starts amplitude limit

The corresponding relation of table 1 incoming level and output

Because first order AGC amplifier works in VGA mode, second level AGC amplifier works in AGC mode, and therefore detection output in the available second level is controlled voltage Vgain as the AGC of two-stage.When input signal changes, the intensity of signal is after the inner square-law detection of second level AGC amplifier, feeding back to two-stage variable control portion of gain divides, gain is averagely allocated to two-stage, realize control range than the monolithic AGC function that doubles, automatically complete gain and control, the AGC so also automatically having realized up to the above dynamic range of 60dB controls.

If first order AGC amplifier is worked in to AGC mode, and now first order AGC amplifier output can not reach AGC and starts to control level point, will be all the time in gain maximum rating, and it is very large that fluctuation is controlled in now gain; And the ride gain of two-stage AGC amplifier can not mean allocation like this, cannot make full use of the good linear characteristic that curve interlude is controlled in such amplifier gain.

Therefore second level AGC amplifier detection is controlled to the gain of two-stage AGC amplifier simultaneously, both realized the function of AGC, also take full advantage of the linear characteristic of gain control koji line simultaneously.

Second level AGC amplifier detection output is as the control level of first order AGC amplifier, the intensity of signal is after the inner square-law detection of second level AGC amplifier, feeding back to two-stage variable control portion of gain divides, operating frequency is higher, and high-gain is easy to cause self-oscillation, adjustment that can be by the self-excitation capacitance that disappears and interspersed ground connection, strong and weak signals with shielding the measure such as separate and solve.

When the utility model is applied in pure analog, because circuit connects simply, can be applied to easily the occasion that noise is less.But because AGC controls voltage, be also to come by agc circuit detection simultaneously, in reality input, always have noise, gain is controlled also not accurate enough.Therefore if need additional AGC control circuit for digital if receiver, be that AGC output is through ADC if sampling, after digitlization, can be sent to FPGA and carry out follow-up IF digital process, in FPGA, digital quantity after AGC output sampling is carried out to detection, be convenient to like this signal to filter to make an uproar process and adopt control algolithm more flexibly and effectively, so that AGC amplifier is made to accurate control.

Claims

1. an AGC intermediate frequency amplifier, is characterized in that: on signal line, AGC amplifier, the final stage amplification module of pre-amplifying module, two-stage cascade are connected successively; Two-stage AGC amplifier adopts VGA chip.

2. a kind of AGC intermediate frequency amplifier as claimed in claim 1, is characterized in that: described pre-amplifying module adopts low-noise wide-band amplifier.

3. a kind of AGC intermediate frequency amplifier as claimed in claim 1, is characterized in that: in described two-stage AGC amplifier, the first order works in VGA mode, and the second level works in AGC mode.

4. a kind of AGC intermediate frequency amplifier as described in claim 1 or 3, is characterized in that: on the control voltage circuit of described two-stage AGC amplifier, be in series with filter circuit module.

5. a kind of AGC intermediate frequency amplifier as claimed in claim 1, it is characterized in that: on signal line, in the AGC amplifier of two-stage cascade and pre-amplifying module, be in series with two-stage matching network module, in signal input part and pre-amplifying module, be in series with a matching network module.