Microwave Ring Circuits and Related Structures phần 7 pdf

CPW section: Zc = 66.9 ohms (center strip Sc = 0.2 mm and gap size Gc =

0.31 mm)

CPW feed lines: Zco = 50 ohms (center strip Sco = 0.6 mm and gap size Gco =

0.31 mm)

Slotline radial stub radius: rs = 5 mm

Slotline radial stub angle: js = 45°

224 RING COUPLERS

(a)

Z co

Zc

Zs

Z co

Zs

Z co

Z co

15

15

5 15

2

1 4

3

Zs Zs

5 5

lgs lgs

lgs

lgs

lgs

lgc

Zc +180o

Zs

(b)

FIGURE 8.30 Reduced-size reverse-phase hybrid-ring coupler (a) layout and (b)

equivalent circuit [41]. (Permission from IEEE.)

To eliminate the coupled slotline mode propagating on the CPW lines, bonding

wires have been used at the coupler’s CPW-slotline discontinuities.

Figure 8.31 shows the hybrid-ring coupler’s measured frequency responses

of coupling, isolation, return loss, amplitude, and phase imbalance, respectively.

The measured results show that the couplings of power from port 1 to ports

2 and 3 are 3.6 and 3.7 dB at 4 GHz, respectively. The isolation between ports

1 and 4 is greater than 19 dB, and return loss is more than 15 dB both over

a frequency range from 2.7 to 6 GHz. The amplitude and phase imbalance

180° REVERSE-PHASE HYBRID-RING COUPLERS 225

0

-5

-10

-15

-20

10

-40

-10

-30

-20

0

-50

1 2 3 45 6

S31

S21

S41

S11

Frequency (GHz)

Return Loss and Isolation (dB)

Coupling (dB)

(a)

5

0

-5

-10

10

0

5

-5

1 2 3 45 6

Frequency (GHz)

Phase Difference (dB)

Amplitude Difference (dB)

S - 21 31 S

S21 S31

(b)

FIGURE 8.31 Measured results for (a) coupling, return loss, and isolation and (b)

amplitude imbalance and phase imbalance [41]. (Permission from IEEE.)

between ports 2 and 3 are excellent over a broad bandwidth. The reduction of

the line length to 72° has no deleterious effect on performance of the circuit.

However, the radial stub in the center of the ring can cause a problem for the

smaller circumference.

8.4.3 Asymmetrical Coplanar Strip 180° Reverse-Phase

Hybrid-Ring Couplers

Figure 8.32a shows the circuit configuration of the new hybrid-ring coupler

consisting of four CPW to ACPS T-junctions and four ACPS arms (one

of them with a 180° phase reversal) [34]. Figure 8.32b shows the equivalent

226 RING COUPLERS

1

2

3

4

(a)

1 Zo

Z ZR R

Z R

4

lg

+180o

3

4

4

lg

4

lg

4

lg

2

Z R Z R

Zo

Zo

Zo

(b)

FIGURE 8.32 ACPS 180° reverse-phase hybrid-ring coupler (a) configuration and

(b) equivalent circuit [34]. (Permission from IEEE.)