Broadband I-Q Vector Modulator: Model 7218

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Application Notes for Microwave Phase Shifter

The Model 7218 is the latest addition to the family of high performance I.Q. Vector Modulators. Its broadband capability is ideally suited for today’s more demanding and complex Electronic Warfare systems.

 

The Model 7218 covers a frequency range of 2 to 18 GHz, is capable of a full 360 Degrees phase control and a minimum of 20 dB amplitude control. Response time is 1 microsecond, maximum. Digital control is accomplished by two 12 bit TTL inputs, for I and Q channels, which provide for high precision calibration of phase and amplitude. Operation is guaranteed to be monotonic.

 

  • Broad Frequency range - 2 to 18 GHz
  • Simultaneous control of phase and amplitude
  • Digitally programmable - 12 Bits for both I & Q
  • High Speed
  • Guaranteed monotonic

 

Broadband I-Q vector modulator model 7218

 

 

Model 7218 I-Q vector modulator block diagram

Fig. 1 - Model 7218 Block Diagram

THEORY OF OPERATION
The block diagram of the microwave I-Q Vector Modulator is shown in Figure 1. An RF signal incident on a 3 dB quadrature hybrid is divided into two equal outputs, with a 90° phase difference between them. The in-phase, or 0°, channel is designated the I channel and the Quadrature, or 90°, channel is designated the Q channel. Each signal passes through a biphase modulator which sets the 0° or 180° state and the attenuation level for both the I and Q paths. The outputs of the I and Q path are combined to yield the resultant vector which may fall anywhere within the bounded area shown in Figure 2. Any signal applied to the I?Q Vector Modulator can be shifted in phase and adjusted in amplitude by applying the following relationships:


1. Let the desired attenuation level = X dB and the desired phase shift
    = θ° (with respect to 0 dB and 0° reference states).
2. The normalized output voltage magnitude is given by: ? V ? =
    10?(x/20).
3. The values of the I and Q attenuator control inputs are then
    expressed as:

I = V cos θ
and
Q = V sin θ.

Figure 3 shows the nominal value of I and Q vs. either digital word (Series 71) or analog voltage (Series 72). Thus, to achieve an attenuation level of 3 dB with a phase offset of 112.5° (with respect to 0 dB and 0° reference states) the values of I and Q can be calculated as follows:

V = 10–(3/20) = 0.707
I = 0.707 cos (112.5°) =–0.027
Q = 0.707 sin (112.5°) =+0.65

From Figure 3, the control inputs to yield the desired amplitude and phase are approximately:

            Analog Units (72 Series)                   Digital Units (71 Series)
                   I = 5.78 volts                                  100101000000
                  Q = 2.84 volts                                  010010001011

While these values for I and Q will yield an output signal whose amplitude and phase are close to the nominal values over the entire operating frequency range of the vector modulator, the use of an iterative measurement procedure will determine the I and Q inputs which exactly define the desired parameter at any selected frequency. 

 I-Q phase relationship for model 7218

 IQ vs control input for vector modulator model 7218

 

PERFORMANCE CHARACTERISTICS 
PARAMETER
SPECIFICATION
OPERATING FREQUENCY RANGE 2.0 - 18.0 GHz
   Band 1
2 - 6 GHz
    Band 2
6 - 18 GHz
    Band Switching Speed,max 250 nanoseconds
INSERTION LOSS (MAX) 16 dB
VSWR (MAX) 2.2:1
POWER HANDLING CAPABILITY
   Without performance degradation
+20 dBm
    Survival 1 W
ABSOLUTE INSERTION PHASE ACCURACY VS. FREQUENCY (MAX) ±15o (in each band)
VARIATION OF PHASE VS. TEMPERATURE (MAX)

±0.1 deg./ oC

ATTENUATION RANGE (MIN)

20 dB

VARIATION OF AMPLITUDE VS. TEMPERATURE (MAX)

0.02 dB/ oC

RESPONSE TIME (MAX)

1.0 µsec

POWER SUPPLY

+5 V ±2% @ 200 mA, max.
+12 to +15V @ 150 mA, max.
-5.2 V ±2% @ 400 mA, max.
-12 to -15V @ 150 mA, max

MONOTONICITY

GUARANTEED

Control INPUT

12 BIT TTL FOR BOTH I & Q INPUTS

CONNECTORS

   RF Input/output

SMA Female, 2X

   Control/Power

Cannon DC-37P or Equivalent

TEMPERATURE RANGE

   Operating

-55 oC to +85 oC

   Storage

-65 oC to +125 oC

 

ACCESSORY FURNISHED
Mating power/control connector
AVAILABLE OPTIONS
Option No.
Description
G09
Guaranteed to meet Environmental
Ratings
G12
RoHS Compliant
 G16  RoHS Plus REACH Compliant
   
DIMENSIONS AND WEIGHT

 

J3 PIN FUNCTION
PIN FUNCTION PIN FUNCTION
19 Q-9
1 I-5 20 I-4
2

I-6 

21 I-7
3 I-8 22 I-3
4 I-9 23 I-2
5 I-10 24 I-1 (LSB)
6 I-11 25 I-12 (MSB
7 BAND 1 (notes 1 & 2) 26 N/C
8 +12 to +15V 27 +5V ±2%
9 GND 28 GND
10 GND 29 BAND 1 (notes 1 & 2)
11 -12 to -15V 30 -5.2V ±2%
12 Q-3 31 BAND 2 (notes 1 & 2)
13 Q-2 32 Q-4
14 Q-1 (LSB) 33 BAND 2 (notes 1 & 2)
15 Q-5 34 N.C.
16 Q-6 35 Q-12 (MSB)
17 Q-7 36 Q-11
18 Q-8 37 Q-10

NOTES:
1. BAND SELECT: Band 1 (2 to 6 GHz) - Apply TTL 0 to Pin 7 or Pin 29
     Band 2 (6 to 18 GHz) - Apply TTL 0 to Pin 31 or Pin 33
2. With no band selected, there will be maximum Isolation between J1 and J2