7/29/2019 Phased Array Antenna Calibration Method in Operating Condition - Rev Method

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PHASED ARRAY ANTENNA CALIBRATION METHOD IN OPERATING CONDITION- REV METHOD -

Isamu Chiba(1), Nobuo Kumagae(2), Rumiko Yonezawa(1), Ken-ichi Hariu(1), and Naoya Morita(1)

(1) Mitsubishi Electric Corporation325 Kamimachiya, Kamakura, Kanagawa 247-8520, Japan

Phone : 0467-41-6165 / Fax : 0467-41-6952Email : Isamu.Chiba@kama.melco.co.jp

(2) Japan Resources Observation System Organization2-20-1 Hatchobori, Chuo-ku, Tokyo 104-0032, Japan

ABSTRACT

A review on recent phased array antenna technologies is presented.The technologies referred to in this presentation are antenna calibration,low sidelobe pattern synthesis for conformal array antennas and densitytapering for active phased array antennas.

1. REV METHOD

To realize an active phased array system, precise phased array antennacalibration is necessary. The Rotating Element electric-field Vector(REV) method[1] is a method to determine the amplitude and phasevalues of the electric field vector radiated from each antenna element ofa phased array under operation. Figure 1 shows the configuration of aphased array used as a receiving antenna. As shown in Figure 2, thecomposite electric field vector of the antenna array of Figure.1 in aspecific direction is a superposition of the electric field vectors of theantenna elements. When the phase of an antenna element is changedby controlling the phase shifter, the composite field vector varies as theelement field vector rotates. Measuring the amplitude variation of thecomposite vector, the amplitude and phase of the element can bedetermined as described hereafter.

In Figure 2, the amplitude and phase of the composite field vector in the

initial state are denoted by 0E and 0 , and those of the i-th element

byiE and i . When the phase of the i-th element is varied by ,

the composite field can be expressed as:( )+

+= iij

ij

ij

eEeEeEE0

0& (1)

Here, the relative amplitude and relative phase of the i-th elementare defined as follows:

00

, == ii X

E

EK (2)

E1ej1

E2ej

2

EN-1ej

N-1

ENej

N

Phase shifters

Combiner

Figure 1. Configuration of a phased array antenna.

00

jeE

iji eE

E&

Figure 2. Composite field vector of a phased array antenna

Figure 3 indicates that the composite power varies sinusoidally asthe phase of one of the elements changes. The relative amplitude

K and relative phase X of the element are determined by thefollowing equations[3]:

20cos21 ++

=K (3)

+

=

0

01

cos

sintanX (4)

where is11+

rr

and r is the ratio of the maximum and

minimum of the composite power, and0

is the phase that

gives the maximum value of the composite power. Here, we can

detect the relative amplitude and phase distribution of the phased

array in operation by changing the phase of each element one by

one and measuring the change of the composite power.

Max

0-

Phase variation

Power

Min

Figure 3. Phase variation vs. composite power.

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7/29/2019 Phased Array Antenna Calibration Method in Operating Condition - Rev Method

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Figure 4 shows the low sidelobe pattern calibrated with REVmethod. This result verified that REV method is effective foraccurate calibration of phased array antennas.

experimentedcalculated

Figure 4. Resultant radiation pattern.

2. ON BOARD REV METH OD

For phased array antennas used in satellite or other mobiles,calibration must be carried out under actual operating condition,in most cases on the antenna apparatus. We call this condition as"On Board". REV can be applied to this "On Board" case. The

procedure of this On Board REV is as follows:

(1) Measure the electric field of mutual coupling (C0i) by REVmethod on Assembly Integration Test in a factory or test field.We call this as AIT.

(2) Far field electric field of i-th element Fi is measured by REVmethod on AIT.

(3) Memorize the difference between D0i = Fi - C0i.

(4) Measure the electric field of mutual coupling C1i by REVmethod on board.

(5) Adjust the excitation phase to D1i ( = Fi - C1i ) using D01 onboard.

The configuration of this procedure is shown in Figure.5.

The On Board REV method was applied to calibrate the phased

array antenna mounted on PALSAR (Phased Array Type L-bandSynthetic Aperture Radar).

TxRx

C0i

Figure 5. Configuration of On Board REV antenna.

3. REFERENCES

[1] S.Mano and T.Katagi :Trans. IECE Japan, J65-B, 5,pp.555-560,1982.

[2] R.Yonezawa , I. Chiba and T. Katagi: IEEE Trans on AP,Vol.AP-47,No.3, 1998.

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