Design Methodology (GPS)

For any research project to succeed, clear objectives have to be defined. The more specific the objectives, the more likely they can be achieved. Specific objectives will be used to develop a GPS/Galileo front-end, the benefits of which will be described in this topic. To ease reader comprehension, the contents and structure of this topic are briefly explained.


The main objective of this topic is to describe a methodology in order to design, fabricate, and test a highly integrated, low-noise, low-power, and low-cost RF front-end prototype for both satellite-based global navigation systems, GPS and Galileo. As shown earlier in this topic, this receiver will be a key component for accessing a variety of new services offered by these systems.

This main objective must be divided into intermediate goals that will lead to the design of the front-end. These have to be accomplished step by step; that is, once the first goal has been fulfilled, the second one will be ready to be tackled. The objectives to be carried out are as follows:

■ A study of GPS and Galileo standards in order to set the requirements for the receiver.

■ Specification of the receiver as a whole and the integrated circuit to be designed, particularly the features of the different blocks. It covers the technology, front-end, and receiver block architectures and selection of the necessary external components, and so on.

■ Design of the receiver spanning from simulation to postlayout results that fulfil the previously defined specifications. It covers not only the receiver blocks, but also the internal logic and the electrostatic discharge (ESD) of the different input/output (I/O) PADs.

■ On-wafer characterisation of the different circuits in the IC, including the passive components and the active circuits.

■ Design and fabrication of the printed circuit board (PCB) for the final application.

■ Measurement of the whole IC in order to validate the prototype.

Throughout this topic, a dual GPS/Galileo RF front-end will be described as an example. This design hails from CEITs COMMIC group of the Electronics and Communications Department (www.ceit. es/electrocom/RF/), which has previous experience in researching GPS front-end receivers.

Benefits of the Receiver

The most promising objective of the proposed dual RF front-end is its compatibility with both GPS and Galileo. Thus, receiver accuracy will be improved, offering the user a range of new services not yet available. GPS/Galileo will change the way many people do their work. It will fundamentally alter business as we know it and provide opportunities for new applications we have not yet imagined.

Additional objectives are proposed to improve features and reduce costs compared to those of actual receivers existing on the market. Among the improvements, a high integration of the proposed architecture is intended; that is, it integrates components that previously were left out, minimising the number of external components needed. Component integration and external component minimisation offers the user a number of advantages: cost, size and weight reduction for the receiver, and at the same time lower power consumption, improvement of features, and reliability enhancement due to the drastic reduction of the number of interconnections and soldering. For users, this means longer battery life and higher receiver quality.

Topic Structure

This topic is arranged according to the logical order in which an IC should be designed. It consists of six topics briefly described as follows.

This topic serves as an introduction to and briefly takes a look at the history of Global Navigation Satellite Systems. It goes on to present the driving force of this topic by showing the strength and versatility of a dual GPS/Galileo receiver. Moreover, a state-of-the-art GPS RF front-end is also included and both commercial and academic receivers are analysed. Finally, the methodology to be followed for the design is described, the benefits of the receiver are expounded, and the structure of this topic is shown.

The second topic deals with the specifications of the receiver. How its specifications have been obtained is described, beginning with a technical explanation and study of GPS and Galileo. With the introductory to specifications, the third topic shows the design of all the IC blocks, including the receiver chain, PLL, control logic, and PADs, as well as the front-end and its component architectures. In addition, the floor planning of the entire IC is shown. Then, the fourth topic deals with the characterisation of the fabricated devices designed in the previous topic. It illustrates the procedures taken to measure them as well as the entire front-end. The fifth topic names some fields that will benefit from such a receiver, and shows an application module for cars that includes the RF front-end design example described in detail in this topic. Conclusions to this topic are summarised in the sixth topic. Finally, the bibliography referenced throughout the topic is also listed.

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