Rectangular PatchEdit

Rectangular patch refers to a planar antenna design that uses a rectangular conducting patch placed on a dielectric substrate with a conducting ground plane beneath. This configuration, often described as a rectangular microstrip patch antenna, is valued for its low profile, light weight, and compatibility with printed-circuit-board fabrication techniques. The patch radiates mainly through fringing fields at its edges, producing a directive, though typically modest-gain, radiation pattern compared to bulkier antennas. Rectangular patches are widely deployed in satellite communications, mobile devices, and wireless networks because they can be manufactured cheaply and integrated easily with other electronics on the same substrate patch antenna and microstrip antenna.

The concept sits at the intersection of electromagnetics and practical engineering: a resonant element that behaves like a short section of a radiating slot, but implemented as a planar, conductive sheet on a dielectric medium. The geometry and materials determine the resonant frequency, impedance, bandwidth, and efficiency. In practice, designers tune the patch length to set the resonant frequency and adjust the patch width to influence bandwidth and input impedance, then select a substrate with appropriate dielectric properties to balance size, losses, and cost. Rectangular patches can be manufactured on flexible or rigid substrates and can be integrated into conformal or compact devices, including handheld radios, global navigation satellite system receivers, and keep-out zones in aircraft or automotive applications antenna substrate (electronics) dielectric.

Overview

Type and geometry: The basic element is a rectangular conductive patch on a dielectric layer with a ground plane. The patch is typically fed by a network that matches the patch’s input impedance to the feed line, often 50 ohms in commercial systems.
Operating principle: The patch supports a resonant surface current distribution. The resonant length corresponds to roughly half a free-space wavelength at the target frequency, modified by the dielectric environment and fringing fields. Radiation arises mainly from the edges of the patch where the current has a nonzero divergence, producing a directive beam perpendicular to the patch plane radiation pattern.
Advantages: Planar, compact, lightweight, and compatible with low-cost, high-volume fabrication. Can be integrated with other circuit elements on the same substrate, enabling compact multi-function assemblies for wireless devices antenna patch antenna.
Limitations: Typically narrow bandwidth and moderate gain unless special techniques are used. Sensitivity to substrate losses and manufacturing tolerances, which can affect impedance matching and efficiency. The size grows with decreasing frequency, making very low-frequency applications bulky bandwidth.

Design and operation

Geometry and resonance

Length and frequency: The resonant frequency f0 is approximately determined by the patch length L through a relation close to f0 ≈ c/(2 L √ε_eff), where c is the speed of light and ε_eff is the effective dielectric constant seen by the patch. In practice, ε_eff lies between the substrate’s dielectric constant ε_r and 1, because fringing fields extend into air above the patch. This dependency means that as ε_r increases or as the substrate becomes thicker, the effective wavelength on the patch changes, altering f0 for a given L.
Width and bandwidth: The patch width W mainly influences the radiation conductance and thus the bandwidth and input impedance. A wider patch generally yields higher gain and a broader bandwidth, up to practical limits set by the operating frequency and the feeding network. The usual starting point is to choose W to satisfy a target impedance and polarization while L sets the resonance.
Simple formulas (approximate): For a single rectangular patch,
- f0 ≈ c/(2 L √ε_eff)
- W ≈ (c/(2 f0)) √(2/(ε_r + 1))
- ε_eff ≈ (ε_r + 1)/2 + (ε_r − 1)/2 [1 + 12 h/W]^(−1/2) where h is the substrate thickness. These relations are used as design starting points, with full-wave simulations or measurements used to fine-tune the geometry for the exact environment microwave engineering electromagnetic theory.

Feeding techniques

Inset-fed patch: The feed line is connected to the patch at a location inset from the edge. By selecting the inset position, the input impedance can be adjusted to match a 50-ohm system, simplifying integration with a transmission line. This method is common for compact, low-cost designs impedance matching.
Coaxial feed: A coaxial connector is attached to the patch with the inner conductor connected to the patch and the outer conductor to the ground plane. This technique provides a straightforward feed but can introduce mechanical limitations and may require careful isolation to avoid unwanted coupling.
Proximity-coupled and aperture-coupled feeds: These methods use coupling through the substrate or through an aperture in a second layer to excite the patch without a direct electrical connection. They offer broader bandwidth and more flexibility for multi-layer designs but add fabrication complexity feed network.
Stacked and multi-layer patches: For higher gain or wider bandwidth, designers may place two or more patches in proximity with coupling between them, sometimes separated by a spacer or another dielectric layer. Stacked configurations can dramatically improve bandwidth and efficiency at the cost of increased thickness and fabrication complexity antenna array.

Bandwidth, gain, and efficiency

Bandwidth: A single rectangular patch typically exhibits narrow bandwidth, especially at higher frequencies. BW can be enhanced by employing stacking, aperture coupling, or using a substrate with lower loss tangent and optimized thickness. However, practical limits exist due to substrate losses and the quality factor of the resonant mode.
Gain and efficiency: The directivity of a single patch is moderate, with gains commonly in the 5–9 dBi range depending on geometry and substrate. Efficiency is influenced by dielectric losses in the substrate and conductor losses in the patch and ground plane. Array configurations can substantially raise the effective gain by combining the radiated fields antenna array.
Polarization: Rectangular patches typically produce linear polarization, with the orientation set by the patch geometry and feed. Circular polarization can be achieved through perturbations to the patch or by using a stacked or rotated arrangement, though with additional design complexity polarization.

Materials and fabrication

Substrates: Popular choices include low-loss dielectric materials such as Rogers laminates or similar substrates with known ε_r and low loss tangent. The dielectric constant and loss tangent influence size, efficiency, and the achievable bandwidth. In cost-sensitive consumer electronics, simpler substrates may be used, trading performance for lower production cost dielectric.
Conductors and coatings: Copper is standard for patches, often with a protective solder mask or conformal coating in consumer devices. Surface roughness and plating quality can affect conductor losses, especially at higher frequencies.
Fabrication methods: Printed-circuit-board processes or additive fabrication techniques can produce rectangular patches. Alignment tolerances, copper thickness, and substrate uniformity all contribute to the final performance, making design margin an important consideration in production runs manufacturing.

Applications and deployment

Satellite communications: Rectangular patches are common in lightweight, compact antenna systems for small satellites and handheld ground terminals, where form factor and mass matter.
Global navigation satellite systems (GNSS): Patch antennas provide stable, robust reception in consumer devices and professional equipment due to their planar form factor and compatibility with other electronics GNSS.
Wireless local area networks and mobile devices: The low-profile nature of patch antennas makes them suitable for integration into laptops, access points, and smartphones where space is at a premium WLAN.
Automotive and aerospace: Conformal or roam-friendly patches can be embedded into vehicles and aircraft to support telematics and communication systems, sometimes in arrays to meet required coverage and gain targets antenna.

Comparisons and variants

Rectangular vs circular patches: Circular patches offer certain symmetry advantages and can present different bandwidth and impedance characteristics. The rectangular form is favored for ease of integration with standard fabrication geometries and predictable resonance along a single axis. Designers may choose between shapes based on space constraints, bandwidth needs, and integration goals patch antenna.
Patch arrays vs single patches: An array of rectangular patches can achieve higher gain and more controlled beam steering, at the expense of more complex feeding networks and calibration requirements. Arrays enable adaptive or scanned beams in modern communication systems antenna array.