How Do I Choose the Best GPS Patch Antenna?

Mal Baxter

Global positioning system (GPS) receivers often use GPS patch antenna elements. These components are small, thin, and easily integrated with varied electronics systems. Essentially a square conductor mounted on a planar surface or microstrip, this antenna can be added into numerous applications while maintaining the high gain that aids in satellite signal reception. Determining factors include uses such as car navigation, phones, and watches, as well as portable computing and remote control airplane navigation. Common varieties can be broken down into active, passive, and reradiating antennas designed for either internal or external mount.

A GPS antenna may help increase the reception signal to a GPS unit.
A GPS antenna may help increase the reception signal to a GPS unit.

Passive and active types differ in power use. The passive type of GPS patch antenna doesn't require its own power. It relies on a short cable to connect with a handheld receiver or can be mounted with magnets inside a car.

A GPS device may be mounted inside of the car of a teen driver to help her navigate the roadways.
A GPS device may be mounted inside of the car of a teen driver to help her navigate the roadways.

Active types require power to amplify signals over greater distances. This permits more versatile placements. These are sometimes powered by batteries or car cigarette lighter adapters.

Reradiating antennas relay satellite signals from outside and send them indoors via cable to devices that have no external antenna jacks. Such types may require clear line-of-sight operation. These units require a power source.

Internal antennas best serve space-limited placements, usually in mobile applications. External antennas are designed to deliver positioning accuracy for wide-band gain and higher performance. Consider the placement conditions and gain requirements for your application and understand the limitations of each.

GPS signals are low-power and high-frequency digital signals. The best type of antenna to receive them depends on various environment and component conditions. For example, a passive ceramic GPS patch antenna provides sensitivity and omnidirectionality for a relatively lower cost. These antennas, like most patch types, function better with the largest possible ground planes.

Conversely, external-type active antennas may contain built-in low noise amplifiers (LNA). This addition provides better performance in low-signal environments, but at a higher cost than passive types. Reradiating antennas best serve areas under heavy cover, where line-of-sight satellite access may be obstructed. Units must first obtain a clear signal before use of an amplifier would make a difference.

Mounting techniques for internal and external antennas vary. The internal GPS patch antenna that suits fixed wireless transmissions, such as placement on a wall, can be mounted to a module or onboard connector. This may be affixed to a component's plastic housing with adhesive tape, screws, or slots. Heavy-duty external antennas are protected against the elements and mounted with screws, adhesives, magnets, or threads. These types may also be resistant to rain or physical abuse.

Other factors influencing which GPS patch antenna to choose can include bandwidth, size, gain, and noise. A GPS receiver tends to perform better with increased size; the larger the ground plane, the more gain. Its radiation pattern may also influence your choice. The shape and direction of its strongest signal may affect, for example, whether a remote-controlled airplane can fly high at a short distance or low at a far distance.

Patch size can influence performance at your targeted bandwidth. Directionality of signal strength can influence gain. You'll get the optimal performance from an antenna with careful consideration of its application and assessment of these and other product specifications.

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