More and more end-products are integrating global positioning as a crucial feature. In addition to familiar navigation systems, “Global Navigation Satellite System” (GNSS) receivers are required in vehicle and asset tracking systems, personal locators, security systems, vending machines, health monitoring and recreational devices.
Every GNSS receiver requires an antenna to pick up the extremely weak signals broadcast from satellites typically 20 thousands kilometers away. As many customers do not have the RF/antenna tuning expertise or the sourcing capability, a performance optimized “GNSS antenna module” which combines both satellite receiver chip and antenna on the same module can be a good solution. These modules provide fast time-to-market and an economically viable solution for “instant” global positioning. A GNSS antenna module is also significantly smaller in size than a GNSS module plus an external antenna. This makes a GNSS antenna module with integrated chip antenna a very attractive and hassle-free option for very thin designs.
For small and medium production runs, sourcing external antennas in low quantities may not be practical in terms of cost and lead times. Custom tuning would also be needed, especially with patch antennas. For these customers, pre-tuned GNSS antenna modules are an attractive choice.
Currently u-blox offers two different kinds of GNSS Antenna Modules: CAM (Chip Antenna Module) which can track GPS, GLONASS or BeiDou satellites, and PAM (Patch Antenna Module) which is dedicated to GPS positioning. Both types have been designed for optimal antenna performance independent of orientation and provide high sensitivity and jamming immunity as they include integrated SAW filters.
Fig 1: CAM-M8Q GNSS chip antenna module supports GPS, GLONASS, BeiDou, QZSS plus concurrent operation
u-blox’ chip antenna module, CAM-M8Q, is a really interesting alternative when customers require both small size and multi-GNSS capability. It is based on a u-blox M8 chip and includes an integrated chip antenna plus SAW filter, LNA, TCXO, RTC crystal and passives. The chip antenna element used in CAM-M8Q can handle all L1 frequencies ranging from BeiDou (1560 MHz) and GPS (1575 MHz) up to GLONASS (1606 MHz). CAM-M8Q is also extremely low in height making very thin customer designs possible.
CAM-M8Q has a feature whereby the internal chip antenna can be used as a backup antenna if the customer chooses to use an external antenna. This is useful in applications where there is a risk that the primary antenna may malfunction or suffer damage. CAM-M8Q is targeted for all applications requiring good Multi-GNSS performance in a compact form factor.
Chip antenna modules require care in design implementation as the PCB forms part of the overall antenna (half of the dipole). For this reason, u-blox provides all necessary design-in support including System Integration Manual plus Application Engineers with many years experience in designing with chip antenna modules.
For GPS-only applications, the PAM-7Q is a highly popular form factor due to its installation flexibility. It can be mounted ‘as is’ in pre-existing designs or soldered with a pin-header to a customized PCB. The 18 x 18 mm patch antenna of PAM-7Q provides RHCP polarization not achievable with smaller patch antenna elements. The simple design and easy interfacing keeps installation costs to a minimum. PAM-7Q targets industrial and consumer applications that require a small, fast and cost efficient solution to GPS positioning.
Fig 2: PAM-7Q GNSS patch antenna module is dedicated to GPS operation
The following schematics illustrated the simplicity of designing with the CAM-M8Q GNSS antenna module. The first schematic shows a standalone solution using the internal GNSS antenna: only a few external passives used for the usual power supply filtering and protection are needed. An optional power on/off power switch is also included.
Fig. 3: CAM-M8Q GNSS antenna module schematic. The internal GNSS chip antenna is used resulting in an extremely simple design
All positioning information is communicated to the host processor via the 2-wire NMEA interface on pins 25 and 26; no host processing is required, the module delivers a final position fix.
The second schematic shows a design where an external GNSS antenna is used. Should the external antenna become damaged, or the connection broken, the module automatically switches to the internal GNSS chip antenna so that positioning may continue.
Fig 4: CAM-M8Q GNSS antenna module schematic using an external GNSS antenna. If the external antenna ceases to function, the module automatically switches to the built-in GNSS chip antenna
This is a very useful feature in vehicle applications where the external antenna could be damaged or compromised in the event of an accident.
Fig 5: A ground plane is necessary when laying out the CAM-M8Q, this is however not a “keep-out” area!
When designing the PCB layout for the CAM-M8Q, make sure the module is mounted on the perimeter of the PCB with the antenna side at the edge.
A ground plane surrounding the module is necessary for optimal RF performance. This is not a “keep-out” area, however, and may be used for mounting other components, see figure 5.
For more information about u-blox GNSS antenna modules, samples and evaluation kits, visit our GNSS antenna module technology page, or visit the PAM-7Q and CAM-M8Q product web pages.
For a video overview o