AN3001 [TE]

PIN diode Vector Modulators - Fundamentals and Drive Requirements; PIN二极管矢量调制器 - 基本原理和驱动器的要求


型号：	AN3001
厂家：	TE CONNECTIVITY
描述：	PIN diode Vector Modulators - Fundamentals and Drive Requirements PIN二极管矢量调制器 - 基本原理和驱动器的要求驱动器二极管
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Application Note

AN3001

PIN diode Vector Modulators -

Fundamentals and Drive Requirements

Rev. V4

Introduction

•

Case 2. If the diodes in the top VVA are set to

an impedance of 50 ohms, the top VVA will be

in a high loss state. The output of the bottom

VVA will have a phase of -90° or 90°, depend-

ing on the impedance of the terminating di-

odes. See the “B” or “/B” labels.

M/A-COM’s Chip Scale Package (CSP) vector

modulator platform offers a means of varying

attenuation and phase in a single surface mount

package. These vector modulators offer linear

phase and minimal amplitude ripple in their bands of

operation. Due to using PIN diodes as the active

devices, these vector modulators have high intercept

points. These vector modulators operate in tandem

with a dual linearizer, MADRCC0002 that has been

developed by M/A-COM.

Case 3. If the output of the top VVA has a

phase of 0° with a magnitude of 1, and the out-

put of the bottom VVA has a phase of 90° with

a magnitude of 1, the resultant vector will have

a magnitude of 1.414 (square root of 2) at an

angle of 45°.

Basic Vector Modulator Operation

The block diagram for the vector modulator is given

in Figure 1. The vector modulator consists of four

elements: an input quadrature hybrid, two voltage

variable attenuators (four-port quadrature hybrids

with both outputs terminated in PIN diodes), and an

output power combiner.

Definition of RF Parameters

It is helpful to define some of the parameters used

to specify the electrical performance of a vector

modulator, so that the specifications are clearly

understood. Note that this type of vector modulator

is designed to have continuous phase shift over

360°.

One of the keys to understanding how vector

modulators work is to understand that there is a

phase shift of 180° when the impedance of the

diodes (for a single VVA) crosses 50 ohms. For

diode impedance of greater than 50 ohms, there is

no phase change when the signal reflects off of the

diodes. This can also be noted on the Smith Chart.

Note that when the impedance of the diodes is less

than 50 ohms, there is no phase shift. The following

will describe the vectors in three cases. See Figure

2 for additional insight into how single vectors pass

through the vector modulator.

Reference Loss: This is the minimum loss where

all phases from 0° to 360° are available. This is

measured at the center frequency of the specified

band.

Attenuation Range: This is the attenuation (relative

to the reference loss), where the performance of

the vector modulator is defined. For example, if a

vector modulator has an attenuation range of 10

dB, and a reference loss of 12 dB, the vector

modulator will operate over an absolute loss range

between 12 and 22 dB. Note that in the case of

SA90-0001, the vector modulator has a higher at-

tenuation range than the specified range, but the

attenuation is difficult to control, and the phase line-

arity and amplitude ripple start to degrade.

•

Case 1. If the diodes in the bottom VVA are set

to an impedance of 50 ohms, the bottom VVA

will be in a high loss state. The output of the top

VVA will have a phase of 0° or 180°, depending

on the impedance of the terminating diodes.

See the “A” or “/A” labels.

Frequency Band (MHz)

925 - 960

Band

GSM

PCS

Model Number

MAMDCC0005

MAMDCC0002

SA90-0001

Model Number of Prototype with Driver

MAMDCC0005-DC000

Availability

Q2 2002

1930 - 1990

MAMDCC0002-DC000

In Stock

2040 - 2240

UMTS

SA90-0001-DC000

In Stock

Table 1. Selection Guide for Vector Modulator

• North America Tel: 800.366.2266 • Europe Tel: +353.21.244.6400

• India Tel: +91.80.4155721 • China Tel: +86.21.2407.1588

Visit www.macomtech.com for additional data sheets and product information.

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

Application Note

AN3001

PIN diode Vector Modulators -

Fundamentals and Drive Requirements

Rev. V4

0°

180°

90°

-90°

Figure 1. Block Diagram

Figure 2. Summation of Vectors

Amplitude Ripple: This is one half of the peak-to-peak

ripple in the specified frequency band. For example, if

the minimum loss is 11.8 dB, and the maximum loss

is 12.2 dB, the peak to peak ripple is 0.4 dB, so the

Amplitude Ripple would be 0.2 dB.

The four outer curves are found by sweeping the bi-

ases as follows:

1. Set Bias2 to 0.0V. Sweep Bias1 from 0.0 to 5.0V

in 0.1V increments.

2. Keep Bias1 at 5.0V. Sweep Bias2 from 0.0 to

5.0V in 0.1V increments.

3. Keep Bias2 at 5.0V. Sweep Bias1 from 5.0 to

0.0V in 0.1V increments.

4. Keep Bias1 at 0.0V. Sweep Bias2 from 5.0 to

0.0V in 0.1V increments.

Deviation from Linear Phase: This is a test to see

how linear the phase of the vector modulator is. To

find Deviation from Linear Phase, a line that best

approximates the measured data points by using the

method of least squares must be found.

The

deviation from linear phase is the difference between

the calculated and measured line.

The circle that is tangent to the inside of the plot is the

reference loss circle, which is about 12 dB in this ex-

ample. Note that the plots in Figures 4 and 5 are the

same, but the lines of different bias voltages were

removed to clarify the curves that are used to find

reference loss. Figures 5 and 6 use the same axes

and scales. The tick marks on the axes are reflection

coefficients in steps of 0.1. The equation that calcu-

lates loss from reflection coefficient is:

Drive Requirements for a Vector Modulator

Driving

vector modulator requires

solid

understanding of the transfer function from the Bias1

and Bias2 inputs to the amplitude and phase change

of the vector modulator. It should be noted that vector

modulators are driven by current, due to the PIN

diode construction. The following description will

focus on how PIN diode vector modulators are driven

by dual linearizers. A chart of the drive characteristics

when driven by current will also be provided.

Mag = 10^(loss_in_dB/20)

Figure 5 provides a plot of insertion loss (in magni-

tude) and phase as the control inputs are varied in

0.5V increments from 0.0V to 5.0V. This gives a good

representation of the loss and phase. However, it

should be noted that this plot will vary lot to lot. The

primary reason for the variation is that the resistance

vs. current of PIN diodes had some lot to lot variation.

Both graphs in Figure 5 have the same data. Due to

the number of labels, the plot was repeated to ensure

legibility.

M/A-COM has designed

dual linearizer,

MADRCC0002, so that the amplitude and phase of

the vector modulators is linearized relative to the

control voltages at the inputs of the linearizer. See

the circuit in Figure

3 for the schematic of

MADRCC0002 driving the SA90-0001 vector

modulator. This same schematic also holds when

driving the MAMDCC0002 and MAMDCC0005 vector

modulators.

The first step is to determine the reference loss of the

vector modulator. See Figure 4, which provides the

transfer function of the test.

Figure 6 is similar to Figure 5, but is a plot of insertion

loss (in magnitude) and phase vs. control current.

• North America Tel: 800.366.2266 • Europe Tel: +353.21.244.6400

Visit www.macomtech.com for additional data sheets and product information.

• India Tel: +91.80.4155721

• China Tel: +86.21.2407.1588

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

Application Note

AN3001

PIN diode Vector Modulators -

Fundamentals and Drive Requirements

Rev. V4

PCB Design Guidelines

The outline drawing for the vector modulator is provided in Figure 7. The recommended PC board layout is pro-

vided in Figure 8. Note that the topology of the bias components on the layout is similar to the topology of bias

components on the schematic. It is important to have the inductors as close to the vector modulator as possible.

If the inductors are rotated around the Smith chart, they will look like capacitors, and will not provide the high

impedance to the RF signal. If the RF signal is not blocked, there can be coupling between the output ports of

the 90° hybrids, which will degrade the performance of the vector modulator. The capacitors should be centered

between the inductors and as close as possible to the inductors, as shown in the PC board layout.

The paddle (base) of the package is grounded to optimize the RF performance of the vector modulator. A chip

scale package (CSP) was used to minimize the amount of PC board space that the end user would require.

There are two RF connections (RF IN and RF OUT) and four bias connections. All of the other connections are

ground. RF IN and RF OUT should be connected to 50 ohm transmission lines. It is preferred to select the PC

board material so that the RF lines are less than 20 mils wide to minimize coupling from the RF lines to the bias

circuit. The lines in the bias circuit should be approximately 6 mils wide to minimize cross coupling.

The recommended solder for mounting surface mount packages is Sn63 (63% Sn, 37% Pb) because it is a

eutectic compound with a melting point (183ºC) high enough to exceed the standard operating limit of the de-

vices, but low enough to avoid damaging internal circuitry during proper solder reflow operations.

Figure 3. Schematic of Dual Linearizer Driving Vector Modulator

• North America Tel: 800.366.2266 • Europe Tel: +353.21.244.6400

• India Tel: +91.80.4155721 • China Tel: +86.21.2407.1588

Visit www.macomtech.com for additional data sheets and product information.

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

Application Note

AN3001

PIN diode Vector Modulators -

Fundamentals and Drive Requirements

Rev. V4

Resistor Thermistor

Quality

Thermistor

P/N for R3, R7

Frequency Range

(MHz)

Coilcraft

P/N L1 - L4

Description of

L1 - L4

Model Number

Values

R2, R6

Values

R3, R7

MAMDCC0005

MAMDCC0002

SA90-0001

925 - 960 (GSM)

1930 - 1990 (PCS)

2040 - 2240 (UMTS)

0603CS-68NXJBC

0603CS-27NXJBC

Inductor, 68 nH, ± 5%

Inductor, 27 nH, ± 5%

270 Ohms

360 Ohms

270 Ohms

750 Ohms

680 Ohms

750 Ohms

QT0805-751K

QT0805-681K

QT0805-751K

Table 2. Selection Table for Bias Inductors

Bias1 = 0.0V

Bias2 = 5.0V

Bias2 = 0.0V

Bias1 = 5.0V

Figure 4. Transfer Function of Test to Determine Reference Loss

• North America Tel: 800.366.2266 • Europe Tel: +353.21.244.6400

• India Tel: +91.80.4155721 • China Tel: +86.21.2407.1588

Visit www.macomtech.com for additional data sheets and product information.

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

Application Note

AN3001

PIN diode Vector Modulators -

Fundamentals and Drive Requirements

Rev. V4

(y)

90°

45°

bias 1 = 0.0V

0.5V

bias 2 = 5.0V

3.5V

3.0V

(x)

0°

1.0V

2.5V

2.0V

1.5V

2.0V

2.5V

1.0V

0.5V

3.0V

3.5V

bias 2 = 0.0V

bias 1 = 5.0V

bias 1 = 0V

bias 2 = +5V

bias 1 = 0V

bias 2 = 0V

(y)

90°

45°

(x)

0°

Loss = 22 dB

Loss = 17 dB

Loss = 12 dB

bias 1 = +5V

bias 2 = +5V

bias 1 = +5V

bias 2 = 0V

Reflection

coefficient = 0.5

1. Tic marks on x,y axes refer to reflection coefficient in increments of 0.1V Reflection coefficients vary from –0.5 to +0.5 on both

the x and y axes.

2. Data is for vector modulators driven by linearizers per attached schematic.

3. Inputs to the linearizers vary from 0 to 5V.

4. The phase with the inputs to both linearizers set to +5V is arbitrarily called zero degrees.

Figure 5. Phase and Attenuation of MAMDCC0006, Vector Modulator Linearized with

MADRCC0002 Linearizer

• North America Tel: 800.366.2266 • Europe Tel: +353.21.244.6400

• India Tel: +91.80.4155721 • China Tel: +86.21.2407.1588

Visit www.macomtech.com for additional data sheets and product information.

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

Application Note

AN3001

PIN diode Vector Modulators -

Fundamentals and Drive Requirements

Rev. V4

(y)

90°

45°

bias 1 = 0 µA

4 µA

bias 2 = 15 mA

6.7 mA

2.3 mA

690 µA

205 µA

112 µA

62 µA

9 µA

17 µA

(x)

0°

33 µA

62 µA

112 µA

205 µA

690 µA

2.3 mA

6.7 mA

15 mA

33 µA

17 µA

9 µA

4 µA

0 µA

bias 1 = 0 µA

bias 2 = 0 µA

(y)

90°

bias 1 = 0 µA

bias 2 = 15 mA

45°

(x)

0°

bias 1 = 15 mA

bias 2 = 15 mA

bias 1 = 15 mA

bias 2 = 0 µA

Reflection

coefficient = 0.6

Reflection

coefficient = 0.5

1. Tic marks on x,y axes refer to reflection coefficient in increments of 0.1. Reflection coefficients vary from –0.6 to +0.6 on both the x and

y axes.

2. The phase with the inputs to both linearizers set to +15V is arbitrarily called zero.

Figure 6. Phase and Attenuation of MAMDCC0006 vs. Bias Current

• North America Tel: 800.366.2266 • Europe Tel: +353.21.244.6400

• India Tel: +91.80.4155721 • China Tel: +86.21.2407.1588

Visit www.macomtech.com for additional data sheets and product information.

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

Application Note

AN3001

PIN diode Vector Modulators -

Fundamentals and Drive Requirements

Rev. V4

Figure 7. Outline Drawing

Figure 8. Recommended PC Board Mounting Pattern for Vector Modulators

• North America Tel: 800.366.2266 • Europe Tel: +353.21.244.6400

• India Tel: +91.80.4155721 • China Tel: +86.21.2407.1588

Visit www.macomtech.com for additional data sheets and product information.

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

AN3001 [TE]

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