CN102891658A - Programmable gain amplifier circuit with orthogonal phase correction - Google Patents

Abstract

The invention discloses a programmable gain amplifier circuit with orthogonal phase correction. The circuit consists of two paths of differential amplifiers, namely an I-path differential amplifier and a Q-path differential amplifier, and an IQ-phase phase correction circuit. The resistance ratio is changed, so that the gain value can be controlled; and the resistance interaction relationship between paths I and Q is changed, so that the signal phase relationship can be controlled; and therefore, programmable amplification of two paths of orthogonal differential signals can be realized, and the phase difference of IQ signals can be controlled to be increased or reduced.

Description

A kind of programmable gain amplifier circuit with the quadrature phase correction

Technical field

The present invention relates generally to the design field of programmable gain amplifier, refers in particular to a kind of programmable gain amplifier circuit with the quadrature phase correction.

Background technology

In present analog CMOS integrated circuit design, particularly in the radio frequency signal receiver, owing to need to faint radiofrequency signal be quantized, usually with high-precision adc it is quantized into digital signal, because the excursion of radiofrequency signal is usually larger, for the radio-frequency front-end signal satisfies the ADC dynamic range, usually the front end at ADC all can increase a programmable gain amplifier, its objective is according to the amplitude of radiofrequency signal and control its gain, so that the input of ADC drops within its dynamic range, thereby reduce the dynamic range requirement to ADC, alleviate the design pressure of high-precision adc; Can there be a problem in radiofrequency signal when receiving demodulation in addition, be that mirror image suppresses, for the mirror image that improves receiver suppresses ability, usually all can adopt quadrature to quantize, the mode of demodulation, namely before signal quantization, signal is orthogonal signal intensity first, this function is finished by frequency mixer usually, yet because can there be error in frequency mixer when converting signal to orthogonal signalling, add the error that programmable gain amplifier and signal transmission path are introduced, its amplitude was not identical when signal arrived ADC, its phase place is not complete quadrature yet, and phase error will be much larger than the impact of range error on the receiver performance on the impact of receiver, thus suppress ability and introduce quadrature demodulation in order to improve the receiver mirror image, and the phase error that how to solve orthogonal signalling becomes a key issue and difficult point.

Summary of the invention

The problem to be solved in the present invention is: for the problem that prior art exists, propose a kind of programmable gain amplifier circuit with the quadrature phase correction.

The solution that the present invention proposes is: aspect gain control, utilize amplifier to add the resistance mode, ride gain changes by the ratio of controlling resistance; For phasing, when IQ two paths of signals orthogonal signalling are amplified, introduced 4 resistance and fed back, by the annexation of controlling these 4 resistance can control the phase difference variable of two-way orthogonal signalling large, diminish or constant.

Description of drawings

Fig. 1 is circuit theory schematic diagram of the present invention;

Reduced graph when Fig. 2 is K switch 1 closure among Fig. 1, K2 disconnection;

To be Fig. 2 be converted into reduced graph after the Single-end output form from the fully differential form to Fig. 3;

Reduced graph when Fig. 4 is K switch 2 closures among Fig. 1, K1 disconnection;

To be Fig. 4 be converted into reduced graph after the Single-end output form from the fully differential form to Fig. 5;

Embodiment

Below with reference to accompanying drawing and implementation the present invention is described in further details.

As shown in Figure 1, this circuit is that I road differential amplifier, Q road differential amplifier and an IQ phase-correcting circuit form by the two-pass DINSAR amplifier, by changing the ratio of resistance, thereby change the size of gain, by the resistance interactive relation of control I, Q two-way, namely change resistance R 9, R10, R11, R12 and change the phase relation of IQ signal, thereby can realize the amplification able to programme of two-way orthogonal differential signal, and the phase difference that can control the IQ signal increases, reduces, and is perhaps constant.

This circuit has three kinds of mode of operations, and the first situation is K switch 1 closure, and K2 disconnects; The second situation is K switch 2 closures, and K1 disconnects; The third situation is that K switch 1, K2 disconnect.The below is explained respectively:

(1) K switch 1 closure, K2 disconnects

As shown in Figure 1, because the circuit parameter of IQ two-way is identical, i.e. R ₁=R ₃=R ₅=R ₇, R ₂=R ₄=R ₆=R ₈, R ₉=R ₁₀₌R ₁₁=R ₁2, K switch 1 closure as shown in Figure 2, mode of operation when K2 disconnects, capacitor C 1 wherein, C2, C3, C4 have been the channel filtering effects, its bandwidth chahnel can not affect gain and the phase place of passband greater than signal bandwidth, for the ease of analyzing, Fig. 2 is simplified to as shown in Figure 3 single-ended format, then has:

$\frac{V_{\mathrm{in}2}}{R_1}+\frac{V_{\mathrm{in}2}-V_{o3}}{R_{10}}+\frac{V_{\mathrm{in}2}-V_{o1}}{R_2}=0---\left(1\right)$

$\frac{V_{\mathrm{in}4}}{R_5}+\frac{V_{\mathrm{in}4}-V_{o1}}{R_{12}}+\frac{V_{\mathrm{in}4}-V_{o3}}{R_6}=0---\left(2\right)$

IN1 as shown in Figure 1, IN2 are a pair of differential signals, and IN3, IN4 are a pair of differential signals, and this two teams' differential signal is orthogonality relation, now suppose V _In1=Asin ω t, V _In2=Asin (ω t+ π), V _In3=Asin (ω t+ pi/2), V _In4=Asin (ω t+3 pi/2), i.e. V _In1=Asin ω t, V _In2=-Asin ω t, V _In3=Acos ω t, V _In4=-Acos ω t.

Through type (1), formula (2) can get:

$(\frac{1}{R_1}+\frac{1}{R_{10}}+\frac{1}{R_2})\·V_{\mathrm{in}2}=\frac{V_{o3}}{R_{10}}+\frac{V_{o1}}{R_2}---\left(2\right)$

$(\frac{1}{R_1}+\frac{1}{R_{10}}+\frac{1}{R_2})\·V_{\mathrm{in}4}=\frac{V_{o1}}{R_{10}}+\frac{V_{o3}}{R_2}---\left(4\right)$

Can obtain

$V_{o1}=\frac{1}{R_2}\·\frac{(\frac{1}{R_1}+\frac{1}{R_{10}}+\frac{1}{R_2})}{\frac{1}{{R_2}^2}-\frac{1}{{R_{10}}^2}}\·A\·(-\sin \mathrm{\ωt}+\frac{R_2}{R_{10}}\cos \mathrm{\ωt})---\left(5\right)$

$V_{o3}=\frac{1}{R_2}\·\frac{(\frac{1}{R_1}+\frac{1}{R_{10}}+\frac{1}{R_2})}{\frac{1}{{R_2}^2}-\frac{1}{{R_{10}}^2}}\·A\·(-\cos \mathrm{\ωt}+\frac{R_2}{R_{10}}\sin \mathrm{\ωt})---\left(6\right)$

Further can get the trigonometric function abbreviation:

$V_{o1}=\frac{1}{R_2}\·\frac{(\frac{1}{R_1}+\frac{1}{R_{10}}+\frac{1}{R_2})}{\frac{1}{{R_2}^2}-\frac{1}{{R_{10}}^2}}\·\sqrt{1+{\left(\frac{R_2}{R_{10}}\right)}^2}\·(-A\sin (\mathrm{\ωt}-\mathrm{\θ})),$ $\mathrm{\θ}=\mathrm{arctg}\left(\frac{R_2}{R_{10}}\right)---\left(7\right)$

$V_{o3}=\frac{1}{R_2}\·\frac{(\frac{1}{R_1}+\frac{1}{R_{10}}+\frac{1}{R_2})}{\frac{1}{{R_2}^2}-\frac{1}{{R_{10}}^2}}\·\sqrt{1+{\left(\frac{R_2}{R_{10}}\right)}^2}\·(-A\cos (\mathrm{\ωt}+\mathrm{\θ})),$ $\mathrm{\θ}=\mathrm{arctg}\left(\frac{R_2}{R_{10}}\right)---\left(8\right)$

Generally, R ₁₀Value all very large, and the phase place of adjusting because of needs is little, so

All smaller, then have

$V_{o1}=(1+\frac{R_2}{R_1})\·(-A\sin (\mathrm{\ωt}-\mathrm{\θ})),$ $\mathrm{\θ}=\mathrm{arctg}\left(\frac{R_2}{R_{10}}\right)---\left(9\right)$

$V_{o3}=(1+\frac{R_2}{R_1})\·(-A\cos (\mathrm{\ωt}+\mathrm{\θ})),$ $\mathrm{\θ}=\mathrm{arctg}\left(\frac{R_2}{R_{10}}\right)---\left(10\right)$

Can be easy to find out R from formula (9), formula (10) ₁₀The variation of major effect phase place can be ignored the impact of gain, and gain can be by control

Adjust, and the phase place variation can be by control Adjust, in this case, the phase difference of IQ two-way has increased

(2) K switch 2 closures, K1 disconnects

Be K switch 2 closures as shown in Figure 4, the mode of operation when K1 disconnects in like manner, in order just to analyze, is simplified to as shown in Figure 5 single-ended format with Fig. 4, then has:

$\frac{V_{\mathrm{in}2}}{R_1}+\frac{V_{\mathrm{in}2}-V_{o4}}{R_9}+\frac{V_{\mathrm{in}2}-V_{o1}}{R_2}=0---\left(11\right)$

$\frac{V_{\mathrm{in}3}}{R_7}+\frac{V_{\mathrm{in}3}-V_{o1}}{R_{12}}+\frac{V_{\mathrm{in}3}-V_{o4}}{R_8}=0---\left(12\right)$

In like manner can dissolve equation obtains

$V_{o1}=(1+\frac{R_2}{R_1})\·(-A\sin (\mathrm{\ωt}+\mathrm{\θ})),$ $\mathrm{\θ}=\mathrm{arctg}\left(\frac{R_2}{R_9}\right)---\left(13\right)$

$V_{o3}=(1+\frac{R_2}{R_1})\·(-A\cos (\mathrm{\ωt}-\mathrm{\θ})),$ $\mathrm{\θ}=\mathrm{arctg}\left(\frac{R_2}{R_9}\right)---\left(14\right)$

Can be easy to find out R from formula (13), formula (14) ₉The variation of major effect phase place can be ignored the impact of gain,

Gain can be by control

Adjust, and the phase place variation can be by control

Adjust, in this case, the phase difference of IQ two-way has reduced

(3) K switch 1, K2 disconnect

In this case, the IQ two-way is feedback not, so phase relation remains unchanged, gain remains by control

Adjust.

In sum, the present invention can realize a kind of programmable gain amplifier with phasing, and simple in structure, and control mode is simple.

Claims (1)

1. programmable gain amplifier circuit of proofreading and correct with quadrature phase is characterized in that:

By an I road differential amplifier, a Q road differential amplifier and IQ phase-correcting circuit three parts form; Identical on I road differential amplifier and the Q road differential amplifier structure, wherein I road differential amplifier is comprised of resistance R 1, resistance R 2, resistance R 3, resistance R 4, capacitor C 1, capacitor C 2 and a Differential OPAMP U1; Q road differential amplifier is comprised of resistance R 5, resistance R 6, resistance R 7, resistance R 8, capacitor C 3, capacitor C 4 and a Differential OPAMP U2; IN1, IN2 are the differential signal inputs of I road, and O1, O2 are the differential signal output of I road, and IN3, IN4 are the differential signal inputs of Q road, and O3, O4 are the difference output of Q road, and the phase place of IN1 and IN2 is quadrature, and the phase place of IN3 and IN4 is quadrature; The IQ delay control circuit is comprised of resistance R 9, resistance R 10, resistance R 11, resistance R 12 and K switch 1, K switch 2, just can control the phase relation of IQ two-way by control switch K1, K switch 2, just can control its gain by the resistance of controlling resistance R1, resistance R 3, resistance R 5, resistance R 7, thereby realize a kind of programmable gain amplifier with the quadrature phase correction.

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