1. What is RF?
A: RF is the radio frequency radio, mainly including wireless transceivers.
2. What is the frequency of mobile phones in today's world (CDMA, GSM, local calls, PHS, analog phones, etc.)?
A: EGSM RX: 925-960MHz, TX: 880-915MHz;
CDMA cellular (IS-95) RX: 869-894 MHz, TX: 824-849 MHz.
3. How should a newcomer who is engaged in Rf work for a long time be improved?
A: First of all, you should have a systematic understanding of the RF system (such as functionality), then you can select some chipsets and study the connectivity between them (connecTIviTIes among them).
4. What is the role of RF simulation software in mobile phone design and debugging?
A: The purpose is to give the designer some idea of ​​the product to be designed before implementing the design.
5. What are the basic principles when designing a mobile phone's PCB?
A: The basic principle is to minimize EMC.
6. The hardware of the mobile phone is composed of RF/ABB/DBB/MCU/PMU. What are the representatives of ABB, DBB and PMU here?
A: ABB is Analog BaseBand,
The DBB is a DiTItal Baseband, and the MCU is often included in the DBB chip.
The PMU is a Power Management Unit, and now there are mobile phones PMU and ABB on top of one chip. In the future, these chips (RF, ABB, DBB, MCU, PMU) will be integrated on one chip to save cost and size.
7. What are the main functions of the DSP and MCU? What is the difference between the two?
A: Actually, both MCU and DSP are processors. There is not much difference in theory. However, in practical systems, based on efficiency considerations, the DSP generally processes various algorithms, such as channel codec, encryption, etc., while the MCU processes signaling and communicates with most hardware peripherals (such as LCDs).
8. What should be noted by newcomers who are just beginning to work on RF front-end design?
A: First of all, you can choose an RF topic, such as PLL, and learn some basic theories, and then start designing some simple circuits. Only in debugging can you gain some experience and help deepen understanding.
9. Recommended RF simulation software and its features?
A: Agilent ADS simulation software for RF simulation. This software supports discrete RF design and complete system design. See the Agilent website for details.
10. Where can I download the corresponding knowledge about the design of the mobile phone, including the functions of several modules, the functions of each module, and the performance requirements of the hardware?
A: You can look at and maybe help. For TI's wireless solution, check out the wireless communications.
11. Why does GSM use GMSK modulation, while W-CDMA uses HPSK modulation?
A: Mainly due to the GSM and WCDMA standards. If you are interested, you can read some books on digital modulation to understand the pros and cons of using different digital modulation techniques.
12. How to solve the LCD model's interference with RF?
A: During the PCB design process, LCD wiring can be performed in a single layer.
13. In the process of designing the mobile phone, in the newly added function, the baseband chip generates noise interference to the FM when transmitting data. How to solve this problem?
A: Check PCB design, find sources of interference and enhance isolation.
14. How to solve the RF interference problem when designing the RF transceiver part of the mobile phone?
A: GSM mobile phones are TDMA working methods, and RF transceivers are not performed at the same time. The basic principle of reducing RF interference is to strengthen matching and isolation. It is necessary to consider that the transmitter is in a high-power transmission state when designing, and it is more likely to cause interference than the receiver, so it is necessary to particularly ensure the matching of the PA. In addition, the isolation of the RF front-end filter is also an important indicator. The PCB board is typically 6 or 8 layers and must have enough ground plane to reduce RF interference.
15. How to eliminate GSM burst interference?
A: In the PCB layout, the digital and RF parts should be well separated, and a good ground plane must be guaranteed. Some power and signal lines must be effectively capacitively filtered.
16. How to solve RF power interference?
A: You must ensure that the RF power is well filtered. A separate power supply can be used for different RF lines if necessary.
17. With RF application circuit, the CPU and other related peripherals work normally when the RF part is not working; however, when the RF starts up, the CPU-independent RF port is also subject to spike-like interference. Excuse me, what is the cause? How to overcome such interference?
A: It may be that the RF part is not well isolated from the CPU. Please check the PCB layout.
18. What are the main considerations when choosing a mobile phone RF chip?
A: The following points are mainly considered when selecting an RF chip:
1 RF performance, including reliability.
2 high integration, requiring fewer peripheral components.
3 cost factors.
19. How to reduce the number of peripheral chips by using mobile phone RF chips?
A: The higher the integration of the mobile phone RF chip, the less peripheral components are required.
20. Will the RF chip generate electromagnetic interference for the peripheral chip, and how should it be eliminated?
A: It should be said that the RF system will generate electromagnetic interference to other DBBs and ABBs, not just RF chips. Strengthening RF shielding is an effective measure.
21. In the wireless communication system, whether the baseband time-domain equalization should be located in the baseband demodulation and bit-synchronized extraction, the result of each bit extraction, after time domain equalization, and then the threshold decision?
A: Yes. It needs to be balanced first and then the threshold decision.
22. The same transmission power, when the frequency is different, is the transmission frequency of high frequency (such as 900MHz) far, and the transmission frequency of low frequency (such as 30MHz) is short (in the open area)?
A: The wavelength factor should be considered. The higher the frequency, the shorter the wavelength, and the larger the transmission loss in the open area, the shorter the transmission distance.
Digital Timer Switch Sockets,Digital Timer Outlet,Plug-in Time Controller,Plug In Timers,Sockets with Timers
NINGBO COWELL ELECTRONICS & TECHNOLOGY CO., LTD , https://www.cowellsockets.com