编者的注意事项 - 在本系列中，我们将落后于场景，看看工程师如何从头到尾巩固项目。有什么挑战会出现？我们如何面对问题并提出解决方案？除了项目完成之外，我们可以在路上庆祝的成功是什么？
In this entry I will be going over the hardware which will be used in the RF Front End board that I’m working on for the series, expected functionality, RF Electronic circuit design considerations, compactness of design, and challenges involved in such a design.
对RF前端芯片的需求对于设计小巧，紧凑和功率有效的无线传输至关重要daughter board(a circuit board that plugs into and extends the circuitry of another circuit board). The design will incorporate the AD9361, which is a high performance, highly-integrated radio frequency (RF) Agile Transceiver™ from Analog Devices. Packaged in a 10 mm × 10 mm, 144-ball chip scale package ball grid array, the AD9361 combines a RF front end with a flexible mixed-signal baseband section and integrated frequency synthesizers, simplifying design-in by providing a configurable digital interface to a processor. With the ability to operate between 70MHz and 6GHz, the AD9361 is ideal for a wide range of radio frequency applications such as 3G and 4G base stations, making it a very versatile chip and giving us the ability to experiment with various frequencies of transmission and reception of the wireless signals. The chip also provides two transmission ports and two reception ports, which will both be utilized in the design. In fact, one of the transmission outputs will be connected to an RF power amplifier in order to increase the wireless transmission range. The designed board is expected to be able to handle various wireless transmission and reception techniques, which will be used to study the best wireless transmission protocol and frequency for a given application such as audio and video transmission. Figure 1 (below) illustrates the AD9361 functional block diagram, the internal architecture of the chip.
The complete circuit design around the AD9361 incorporates, power supplies with decoupling circuitry, RF differential signal couplers and decouplers, power supply, monitor, analog-to-digital converter (Serial Peripheral Interface SPI), on board EEPROM for data storage (SPI), and other components. An SPI bus will be used to communicate with the RF front end chip (AD9361), EEPROM and analog-to-digital converter.
Design For Electromagnetic Compatibility
Such a circuit presents a number of challenges when migrating from a schematic to a printed circuit board (PCB) design. This is due to physical phenomena related to high frequency signals propagating trough conductors such as copper. When a high frequency signal is propagating through a conductor, a number of effects can be observed such as the conductor behaving similarly to inductors or capacitors or the conductor behaving as an antenna due to internal reflections. In order to rectify these effects as much as possible, impedance matching between devices, conductors and ports is imperative. Additionally, a perfectly matched system will be able to maximize the power transmitted from one point to the other.
为了降低电磁干扰，具有战略放置的地面和电力平面的多层PCB是重要的。数字信号线必须在地面和电源平面之间埋入PCB内，以便最小化干扰。以上图说明了PCB轨道的理想设置，这将用于实现这种设计。物理分离的RF信号轨迹是进一步减少串扰的另一重要技术。
当开始新的硬件设计时，电子工程师必须由电子工程师进行这种考虑，以便尽可能减少与硬件的合理可行的未来问题。
In the next entry for “Engineers in the Wild”, I will be discussing the design in terms of the resulting Zmod daughter board, providing details on what one may use such a board for and how communication between the ZYNQ chip on a Digilent board will communicate to the AD9361. See you then!
