The integration of low frequency and high frequency RF wireless systems is quite different. In the high frequency band, since the CMOS process can achieve higher bandwidth than the bipolar process, it is the preferred process for RF circuits. Generally, RF-CMOS is not integrated on the same chip as digital CMOS. The most important system in the low frequency band is the cellular communication system, and the integration of RF functions of such systems focuses on the integration of passive components. This article describes strategies for integrating passive components with RF active components through multiple packages or modules. Information plays an important role in the two-point transmission of communication systems. In such systems, RF functions are often physically separated from other functions, and RF transmission and reception are typically implemented by different ICs. In order to reduce the size of the system and reduce the cost, people continue to explore ways to integrate RF with other functions of the system, especially the development of DSP technology has a very important impact. In addition to this trend of RF and non-RF integration, the RF device itself has other integration trends. These different trends are due to the different systems that require different technologies to achieve the required RF functions. For example, some systems require effective filtering of the signal before it is passed to the low noise amplifier (LNA). This requires a ceramic filter or surface acoustic wave (SAW) filter to filter the received signal, but these filters Neither can be integrated into the receiver IC. The difference between low frequency and high frequency systems An important difference between low-frequency and high-frequency systems is that the latter can only achieve signal transmission without blocking between the transmitter and the receiver, while low-frequency systems do not have such requirements, thus enabling greater Coverage area. There is no clear demarcation point between low and high frequencies, and the excess frequency is between 2-5 GHz and depends on system characteristics such as transmitter output power and receiver sensitivity. This article uses 2.4GHz as the conversion point for high and low frequencies. High-frequency systems can also be divided into long-distance systems and short-range systems. Long-distance systems such as radar, satellite links, base station links, fixed wireless broadband access (FWBA), etc., require higher transmit power than short-range systems such as Bluetooth and 802.11a/b. High frequency RF integration The target market for short-range wireless communication systems is the consumer electronics market, which requires small size and low cost, and as the demand for applications for streaming video through data increases, the data transmission rate will continue to increase. These systems are basically portable battery powered products that require long standby and talk time. High frequency systems (above 2.4 GHz) enable high bandwidth and moderate receiver selection characteristics due to fewer transmitters operating in the high frequency range. Similarly, the receiver's signal-to-noise ratio (S/N) is high, so the transmitter's output power can be low. For example, 802.11b has 11 Mbps bandwidth at 2.4 GHz and 802.11a can reach 54 Mbps at 5 GHz. The use of wider bands or more complex modulation methods requires tighter signal linearity, which is closely related to the transmitter. Figure 1 shows the comparison of the operating frequencies that CMOS and BiCOS can achieve. The process technology used in the system is related to the operating frequency that can be achieved. Figure 1 shows the comparison of the operating frequencies that can be achieved by CMOS and BiCOS. Assuming fmax is directly related to the available operating frequency, it is clear that CMOS is a better choice. In addition, CMOS can meet the requirements of less stringent selectivity, signal-to-noise ratio and output power, but the dynamic performance is reduced due to the low operating voltage. However, since many systems operate in the open frequency band, there may be many transmitting devices interfering with each other between the transmitter and the receiver. For example, microwave oven interference with Bluetooth communication is a typical example. Although CMOS has these advantages at high frequencies, BiCMOS technology has the advantages of bipolar RF model and transistor parameter matching, and BiCMOS design experience is more abundant. Size is not a major consideration in process selection because the chip size of the Bluetooth transceiver function is similar in a 0.18um CMOS or BiCMOS process. If a CMOS process is chosen, standard digital CMOS will be a trend, and since these digital CMOSs ​​themselves have adopted a multi-layer mask process, no additional options will be added. Digital functions will occupy the largest chip area, so the main cost will be generated in these digital functional parts. Does it make sense to integrate digital circuits and RF functions on a single chip using mainstream CMOS processes? This problem needs to be considered in two ways: From a technical point of view, it is possible to use standard CMOS that is improved to achieve RF functionality, such as high-impedance substrates to reduce crosstalk through the substrate and thick media for high quality passive components. Factors, etc.; from an integration perspective, there is not much benefit to applying standard CMOS to RF and integrating digital and RF functions on a single chip, because the digital and RF models and libraries are fundamentally different. Digital circuits are often designed in VHDL/Verilog languages, and digital libraries for CMOS technology are often implemented before new technologies emerge. These digital libraries are used from generation to generation, so design engineers can digitally design before the next generation of processes. For RF designs, models and libraries are only available after the process has emerged, so RF devices have their own unique characteristics. Since RF functions generally do not have 1:1 reusable modules, each new device must be developed from scratch. The RF library usually lags behind the digital library for 1-2 years. Using mainstream CMOS technology to implement RF functions means that the process will be behind generations. Therefore, integrating digital and RF functions on a single chip means that the previous generation CMOS process will be used to implement digital functions, which is usually more expensive to implement. Moreover, passive components (inductance) and RF/analog functions do not really evolve with the CMOS process technology. Therefore, the area occupied by the RF portion will increase with different technology generations. P03 Series Push Wire Connectors
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