Target Tracking - MATLAB Simulations for Radar Systems Design - page 411

9.3. Phase Comparison Monopulse
Phase comparison monopulse is similar to amplitude comparison monopulse
in the sense that the target angular coordinates are extracted from one sum and
two difference channels. The main difference is that the four signals produced
in amplitude comparison monopulse will have similar phases but different
amplitudes; however, in phase comparison monopulse the signals have the
same amplitude and different phases. Phase comparison monopulse tracking
radars use a minimum of a two-element array antenna for each coordinate (azi-
muth and elevation), as illustrated in Fig. 9.14. A phase error signal (for each
coordinate) is computed from the phase difference between the signals gener-
ated in the antenna elements.

antenna
axis

target

R 1

R 2

R

ϕ

α

d

Figure 9.14. Single coordinate phase comparison monopulse antenna.

Consider Fig. 9.14; since the angle α is equal to ϕ π 2 + ⁄ , it follows that

 2

d
-- 

2 d

π
---

 

R 2 R 2

--- R

= + – cos ϕ +

(9.12)

 

d

--- 2

R 2 = + – dR sin ϕ

and since dR « we can use the binomial series expansion to get

d
2 R

 

-------

R 1 ≈ R 1 + sin ϕ

(9.13)

 