What is the difference between a series fed and a corporate fed microstrip antenna array?
Array Feed Architectures
The series-fed array connects elements along a single microstrip transmission line. Each element taps off a portion of the traveling wave. The inter-element phase is determined by the transmission line length between elements. Since the electrical length changes with frequency (phase = β × d, where β = 2πf√εeff/c), the beam direction changes with frequency. This beam squint is approximately: Δθ = sin⁻¹(Δf/f × d/λ × √εeff) degrees per percent bandwidth.
| Parameter | Low Gain | Medium Gain | High Gain |
|---|---|---|---|
| Gain Range | 2-6 dBi | 6-15 dBi | 15-45 dBi |
| Beamwidth | 60-360° | 15-60° | 1-15° |
| Typical Types | Dipole, monopole, patch | Yagi, helical, horn | Parabolic, array, Cassegrain |
| Bandwidth | Narrow to wide | Moderate | Narrow to moderate |
| Complexity | Low | Medium | High |
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
Frequently Asked Questions
How much beam squint is acceptable?
For communications: beam squint should be less than θ3dB/4 across the operating bandwidth. For a 10° beamwidth antenna: maximum acceptable squint is 2.5°. For a 5% bandwidth series-fed array at broadside: squint is approximately 3-5°, which may be unacceptable for narrow-beam applications.
Can I compensate for beam squint?
Partially. Using meandered feed lines between elements can equalize the frequency-dependent phase. This technique reduces beam squint but does not eliminate it entirely. True broadband operation requires a corporate feed or true-time-delay feed network.
What about resonant vs traveling-wave series arrays?
Resonant arrays have elements spaced at exactly λg. They produce a broadside beam but have very narrow bandwidth (< 1%). Traveling-wave arrays have non-resonant spacing and terminate in a matched load, providing wider bandwidth but with the beam squint characteristic.