Integrated global positioning system receiver

Abstract: A GPS receiver (1) has an antenna (3) mounted directly to a first side (4) of a multilayer printed circuit board (PCB) substrate (2). Electrical conductors interconnect the antenna (3) with an RF processing system and a digital processing system mounted directly to an opposite side of the PCB substrate (2). An electrical connector (17) is disposed on the PCB substrate (2) providing power, ground, and electrical access to digital data representing a processed GPS signal supplied by the digital processing system.

Description: The present invention relates to antennas and,more particularly,to antennas having higher levels of integration than previously known. An antenna appropriate for receiving radio frequency (RF) signals transmitted by global positioning system (GPS) satellites is known. It is desirable to incorporate the positioning capabilities of the GPS into an automobile. The known antenna, for example M/A-COM part ANPC 128B-N-7-2, receives 1.51Ghz radio frequency signals and launches the received signal onto a cable to a coaxial connector termination. A printed circuit board (PCB) in the automobile receives the RF signal to process it further down to an intermediate frequency (IF). The IF is then launched to another PCB populated with digital circuitry having GPS intelligence for interpretation of the signal into positioning information. Disadvantageously, the transmission of the RF signal through the cable injects noise and generates loss, which can degrade the signal prior to processing. Degradation of the RF signal has a direct impact in reducing the sensitivity and reducing the effectiveness of the overall system. The known GPS solution also requires relatively large packaging and is expensive to design and maintain at the system level due to the number of functional modules that comprise the overall system. The problem is exacerbated in an automobile because the standard form factor of a passenger automobile, the desirable physical size of the automobile, and the desirability of passenger space limits the available "on board" space for functional components. Once a system is installed in an automobile, because it is aesthetically desirable to hide the automobile's functional systems, access to the system's component parts is also limited. The problem is further exacerbated by the difficulty in installing coaxial cable and connectors in a vehicle. Coaxial cable is not a standard for the automobile industry and not only degrades GPS performance but also causes coupling of unwanted signals to other electronic components such as the radio. Much of the wiring in vehicles is now implemented as a data bus. EP-A-0 725 457 describes an integral type flat antenna comprising an antenna element and integrally formed multilayer substrate for supporting the antenna element. The substrate includes a grounding plane layer on which the antenna element is mounted, a first insulating layer disposed below the grounding layer, a second insulating layer positioned below the first insulating layer, and a conducting layer disposed between the insulating layers. The first insulating layer mounts a frequency conversion circuit for converting RF signals into IF signals and the conducting layer connects the antenna element to the frequency conversion circuit. The output from the frequency conversion circuit is transmitted from the substrate via an output connector. An object of the present invention is to provide a smaller, more efficient, and less expensive GPS receiver system especially packaged to connect directly to standard vehicle wiring harnesses and data buses. The invention resides in a GPS receiver as set forth in claim 1 hereof. It is a feature of the GPS receiver according to the teachings of the present invention that a receiving antenna and digital data connector (implementing the bus, power and Ground interfaces) are integrated on a single PCB with all intervening analog and digital circuitry also mounted on the PCB. It is another feature of the teachings of the present invention that the GPS receiver provides for a direct connection of the GPS receiver to a data bus including al of the GPS signal intelligence and electronics to transmit signals to and from the vehicle bus. Advantages of a GPS receiver according to the teachings of the present invention are that the system sensitivity is improved over prior art GPS systems; the system can be smaller, less expensive to manufacture, and more reliable than prior art GPS systems; the overall system complexity is less than prior art GPS systems; the receiver will be less susceptible to electromagnetic interference and will cause less interference in other electronic components; and the ease of installation will be substantially improved by a direct or "one touch" installation procedure onto a vehicle bus. It is yet another advantage of a GPS receiver according to the present invention that overall installation of GPS onto a vehicle will be less obtrusive affecting the styling and vehicle design and allowing the GPS antenna to be hidden. This means it is less likely to be forcefully removed if the vehicle is stolen. It is a further advantage of a GPS receiver according to the present invention that a GPS receiver with the physical means to connect to a vehicle bus can provide additional networking features not yet contemplated by the current state of the art including output of GPS data directly to the vehicle standard wiring harness, reading data messages from the vehicle to perform diagnostic self checking, and output of data on demand. Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a plan view of a first side of a GPS receiver system according to the teachings of the present invention. Figure 2 is a plan view of a second side of a GPS receiver system according to the teachings of the present invention. Figure 3 is a side view of a GPS receiver system according to the teachings of the present invention. With specific reference to Figure 1 of the drawings, there is shown an integrated GPS receiver system 1 according to the teachings of the present invention. What is shown and described herein specifically describes a GPS receiver system optimized for an on board automobile application. The teachings of the invention, however, are applicable to other applications having similar functional requirements such as embedded cell telephones and data terminals, proximity sensors, or any other wireless communications device. The integrated receiver system 1 comprises a multilayer PCB substrate 2 having a patch antenna 3 mounted directly on a first side 4 of the PCB 2. The patch antenna 3 is optimized to receive a 1.51Ghz RF signal from GPS satellites. A multilayer PCB refers to a PCB having a number of alternating layers of dielectric and conductive printed traces interconnected by conductive vias in a particular pattern that is appropriate for a given electrical circuit. Surface mountable two-pole filter 6, diode 7, and capacitor 8 are also surface mounted onto the first side 4 of the PCB. An output of the antenna (not shown) is interconnected to the filter 6, diode 7, and capacitor 8 through interconnecting vias and traces (not shown) on an intermediate layer of the PCB to complete the RF filter system. A filtered RF signal is output out of the RF filter system. All, but a portion of the first side 4 of the PCB surrounding the components mounted thereto is metalized to form a shielding ground plane to improve performance of the receiver system. With specific reference to Figure 2 of the drawings, there is shown a second side 5 of the PCB substrate 2 on which a RF processing system 9 and digital processing system 10 is disposed. The RF processing system comprises a RF application specific integrated circuit (ASIC) die 11, which in the disclosed embodiment is a NAVSTAR ROC3 integrated circuit. The RF ASIC die 11 is mounted directly to the board using "chip on board" manufacturing technology. "Chip on board" manufacturing technology is known in the art and comprises mounting IC die directly to a PCB substrate, wirebonding IC contacts to conductive traces printed onto the PCB 2, and covering the IC and wirebonds with a protective polymer. "Chip on board" manufacturing technology advantageously obviates the need for separately packaging each IC which helps to reduce the physical size and cost of the resulting circuit. Circuitry 12 supporting the RF ASIC is also mounted to the second side 5 of the PCB 2 using either "chip on board" or surface mount technology as appropriate. Interconnecting traces and vias present in the PCB 2 interconnect the RF ASIC 11 with the supporting circuitry 12. Advantageously, the "chip on board" technology removes the use of packaging for the RF ASIC and significantly shortens the length of interconnecting traces through which the analog signals travel. The shortened length reduces the amount of resistive and reactive impedances and, therefore, also reduces signal degradation and loss present in prior art solutions. The RF ASIC 11 and supporting circuitry 12 perform functions that include frequency generation of the local oscillator (LO) and downconversion of the RF signal to an intermediate frequency (IF). The RF processing system 9 outputs an IF signal indicative of the received RF signal. An IF OUT interconnecting trace 13 interconnects the processed RF signal to a digital processing system. The digital processing system comprises a digital ASIC 10, which in a preferred embodiment is a NAVSTAR XR7 digital ASIC specifically optimized to receive and process an IF signal from a received GPS RF signal and write this processed data to the bus or receive data from the bus, and supporting digital circuitry comprising program memory 14 and data memory 15. The digital ASIC 10 is interconnected to the program and data memories 14,15 through a plurality of parallel interconnection traces 16. The digital ASIC 10 samples and digitizes the received IF signal, correlates the data, detects the satellite code, calculates position, velocity and time as a function of the received RF signal and formats the position velocity and time data to be read from the bus. The digital ASIC also reads and interprets bus data and can perform diagnostic self-check of the entire GPS system. An output of the digital ASIC 10 comprises digital data representing position and velocity of the vehicle in which the patch antenna is disposed. Similar to the first side 4 of the PCB 2, all but a portion of the second side 5 of the PCB surrounding the RF processing system 12 components and surrounding the digital processing system components and interconnecting traces are metalized to form a shielding ground plane to improve performance of the receiver system. The PCB 2 has an eight (8) position connector 17 mounted thereon. The connector 17 brings power and reference potential to the entire receiver system 1 and launches the processed GPS information external to the PCB 2. Each digital line is capacitively filtered with chip capacitors 18 positioned between each one of a plurality of signal terminals 19 and the reference potential. The digital data from the digital ASIC 10 is communicated to a main processor area (not shown), typically a large PCB, mounted in an automobile that centralizes all of the intelligence functions for the automobile. The GPS information is one of many pieces of information received and processed by the automobile's main on board computer. The connector 17, as shown in the drawings, is chosen for matability with an existing cable assembly in the automobile. Alternatively, a smaller eight(8) position connector is equally suitable provided the automobile's cable assembly is equipped to interface with the connector chosen. Advantageously, any degradation of the digital signal over the cable in the cable assembly can be recovered through signal processing without compromise in the sensitivity of the overall GPS receiver system. As will occur to one of ordinary skill in the art, the present invention may be optimized for a GPS receiver mounted in other vehicles or in a hand held unit.

Claims: A GPS (global positioning system) receiver comprising a printed circuit board substrate (2) having a GPS antenna (3) and at least one integrated circuit (10,11,12) disposed thereon, electrical conductors interconnecting the antenna and said at least one integrated circuit, said at least one integrated circuit being electrically connected to the antenna for converting RF signals from the antenna into intermediate frequency (IF) signals, and an electrical connector (17) disposed on the printed circuit board substrate and providing electrical access to said at least one integrated circuit, characterised in that said at least one integrated circuit is also adapted to process the IF signals to produce GPS signals representing the position and speed of the receiver, and the connector is a plug in connector (17) which is coupled to said at least one integrated circuit (10) so as to receive GPS signals therefrom and which plugs the receiver into the electronic system of a vehicle. A GPS receiver as claimed in claim 1, wherein said at least one integrated circuit includes a first integrated circuit (11) electrically connected to the antenna (3) for converting RF signals from the antenna into IF signals, and a second integrated circuit (10) adapted to process the IF signals to produce the GPS signals. A GPS receiver as claimed in claim 2, wherein the second integrated circuit (10) comprises circuitry for initiating a diagnostic testing operation on the receiver responsive to the data from the data bus of the electronic system of the vehicle. A GPS receiver as claimed in claim 1, 2 or 3, wherein said at least one integrated circuit transmits and receives data to and from a data bus in the electronic system of the vehicle through the electrical connector (17). A GPS receiver as claimed in any preceding claim comprising a memory module (15) disposed on the printed circuit board substrate (2) for storing data to be used with signals processed by said at least one integrated circuit. A GPS receiver as claimed in claim 5, wherein said at least one integrated circuit and the memory (15) are disposed on one side (5) of the printed circuit board substrate (2), and the antenna (3) is disposed on another side (4) of the printed circuit board substrate. A GPS receiver as claimed in any preceding claim wherein power to the receiver is supplied from the electronic system of the vehicle.

Inventors: GRIFFIN WILLIAM P, JORDAN DAVID F, LACHAPELLE JOHN, MARTIN DAVID, MCGRATH FINNBARR, GRIFFIN, WILLIAM P., JORDAN, DAVID F., LACHAPELLE, JOHN, MARTIN, DAVID, MCGRATH, FINNBARR
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1999
Main classification: H04B1
IPC codes: H04B1, G01S5, G01S1