Generally speaking, we ordinary users only need to learn how to use the mobile phone well, and we don't need to study its specific working principle carefully; However, in the process of using mobile phones, due to various factors, mobile phones will inevitably malfunction. If you encounter even the smallest fault every time, it may be troublesome to send it to a professional repair shop for repair. If you have good electrical knowledge, you may want to learn to repair it yourself, but if you want to learn to repair it, you must be familiar with the working principle of the mobile phone first. Only in this way can you judge the cause of the fault and find out the corresponding solution. At the same time, understanding the working principle of mobile phones can also be used as a knowledge reserve for ordinary people. In order to help these users who love mobile phones learn to repair quickly, the author takes Motorola mobile phones as an example to introduce how mobile phones work in detail.
The reason why mobile phones can communicate with each other is because it is the result of the cooperative work of radio frequency part, logic part and power supply part. To understand the working principle of mobile phones, we only need to understand how these three parts work. The following author will introduce the working principles of these three parts respectively.
Radio frequency part
Generally, the RF part consists of a signal receiving part and a signal transmitting part. When a mobile phone receives a signal, it first separates the received RF signal of 935-960MHz from the received RF signal through U400 and SW363, so that the transceivers do not interfere with each other. Input the fourth pin of U400 and output the fifth pin, and enter the receiving front-end loop. The working state of U400 is controlled by the third pin potential, which in turn is controlled by TXON and RXON signals sent by CPU. The RF signal passing through the antenna switch is filtered by the band-pass filter FL45 1 and then sent to the high-frequency amplifier Q4 18 for amplification. The output of Q4 18 is filtered by FL452 and sent to Q420 mixer for mixing. The local oscillator signal is generated by RXVCO, filtered by FL453 and sent to the base of Q420 for mixing, and the difference is taken. The collector of Q420 outputs an intermediate frequency signal of 153MHz, and after filtering by FL420, a pure signal of 153MHz is obtained. Now it is amplified by Q42 1 and sent to 3 1 of U2065438. The intermediate frequency signal of 153MHz and the carrier signal of 153MHz are demodulated within 32D53 to generate RXI and RXQ analog baseband signals, which are sent to U50 1 14# and/kloc-through 46# and 48# of U20 1. After A/D conversion in U50 1, it is sent to digital signal processor for further processing. The carrier wave of 153MHz is a 306MHz oscillator circuit composed of 4 1#, 42# and 43# of U20 1, which forms a wave signal of 306MHz, and after two frequencies, forms the carrier wave of 153MHz. In the transmitting part, TXIN, TXIP, TXQN and TXQP signals output from 2 1#, 22#, 23# and 24# of 50 1 enter 6 1#, 62#, 63# and U20 1. U20 1 6#, 7# and 10# are externally connected with a VCO of 2 16MHz to generate a carrier signal of 2 16MHz, which is divided by the frequency divider in U20 1 to generate the transmission of 108MHz. Four modulated signals are modulated by 108MHz carrier in U20 1 and output from the 4 # pin of U300. U300 completes the phase smoothing frequency between the transmitted sampling signal and TXVCO, and takes the difference to obtain 108MHz signal and TXIF input of No.4 to generate phase discrimination error voltage, which is output from the eighth pin to control the capacity of varactor CR300 and change the oscillation frequency of TXVCO. The 890-9 15MHz transmission signal output from the C pole of Q300 enters the power amplifier Q302 after being amplified by Q30 1 and pushed by Q302. The amplified signal enters the 1 pin of the antenna U400, and then is emitted from the 4# transmitting antenna of U400.
Logical part
In the logic part, the received analog baseband signals RXI and RXQ are subjected to D/A conversion, decryption and adaptive equalization in the modem U50 1, and then the digital baseband signals are sent from 6# of U50 1 to 10# of CPU for channel decoding, and the recovered voice data flows through the data line and address line after removing the error correcting code source and taking the real control information. The generated digital voice signal is sent from 78# of U80 1 to 8# of PCM decoder U803. The digital voice signal is decompressed and A/D converted in PCM decoder, then the received signal and volume are adjusted by digital volume locator, and then the analog audio signal is output from 4# of U803 to 6# and 2 1# of U900. After the ringing signal of the 6# input is amplified by the internal ringing driver, the 4# and 5# outputs of U900 drive the ringer to send the inter-tone signal, the 2 1# input, and the amplified voice signals from 19# and 20# output drive the receiver to sound. When our users are on the phone, the voice is converted by the receiver and sent to the 9# terminal of the power integrated circuit U0-. After internal audio amplification, the amplified analog audio signal is output from the 10# terminal. The signal is sent to the PCM codec U803 of 18#, and the pulse code modulation is completed inside U803. The PCM signal output by 13# is sent to the 89# speech encoder of 80 1, and the speech data line and address line are fed into U80 1, and the speech data stream is loaded into the central processor U70 1. After the channel coding of the voice data stream is completed in U70 1, the 1 1# after U70 1 is sent to the 4# of the modem U50 1, and the signal is subjected to D/A conversion and encryption processing in U50 1.
supply unit
As for the power supply, once we put the battery on the mobile phone, the electronic Q999 will turn on. At the same time, 48# of 32D54 is connected to the positive pole of power supply. At this time, if we press the power-on key again, the 24# of U900 will become low level, and the four voltages stably output by U900 are R275V, L2.75V, R4.75V and L5.0V respectively. The 30th # generates a reset signal, and the 27th # generates an application start signal. The 13MHz clock oscillator consisting of 32D53 and 13MHz crystal and transformer diode * * generates the 13MHz clock, which is shaped and amplified in the 32D53, and then output from 59 # to 17# of the buffer interface circuit U703, and then sent to 57 # of the CPU from 37 # of U703. In addition, the collector voltages of Q202 and Q203 are both 2.75V, which supplies power for the receiving or transmitting circuit inside 32D53. L5.0V sent by No.3 U900 supplies power to the negative voltage generating circuit. Version, SIM card and PCM codec U803 are also powered by L5.0V The voltage of R2.75V from U900 No.28 supplies power to all logic modules. The voltage of 2.75V sent by U900 on 28th is supplied to the RF part. The R4.75V voltage sent by U900' s 4 1 # generates power for the transceiver intermediate frequency circuit 32D53, and the VXW conversion voltage output by U900' s 37 # supplies power for the emitters of Q202 and Q203.
Because the model of the mobile phone is different from the manufacturer, the working principle mentioned above may not be applicable to some mobile phones, but the general workflow should be the same.
Second, mobile phone manufacturing related knowledge
Nowadays, mobile phones have gradually separated from the identity of simple communication tools and gradually become multimedia and information terminal equipment. In the future, daily communication, entertainment, financial management and other activities can be carried out through mobile phones. Do you have such curiosity every time you see a novel mobile phone with high performance and beautiful design? How is such a mobile phone designed and manufactured?
So today, we try to briefly describe the structure of the mobile phone design department and the relationship between departments from a technical and objective perspective. Finally, I will show you all kinds of tests of mobile phones from manufacturing to listing, so that everyone can know more about mobile phones and cherish their favorite mobile phones. Maybe you won't change it easily in the future!
First, the design process of mobile phone
Briefly, a general mobile phone design company needs six basic departments: ID, MD, HW, SW, PM, Sourcing and QA.
1, ID (industrial design) industrial design
Including the appearance, material, feel and color matching of the mobile phone, the realization of the main interface and the color design.
For example, Motorola's "Ming" clamshell is translucent, Nokia's 76 10 is curved, Sony Ericsson W550 is sunny orange, and so on. These special feelings and experiences for users belong to the category of mobile phone industry design. Whether a mobile phone can become a best-selling product, the industrial design of the mobile phone is particularly important!
2.MD (mechanical design) structural design
The selection of the front and back shell of the mobile phone, the location of the camera, the fixing method, how to connect the battery and the thickness of the mobile phone. If it is a slide phone, how to make the phone slide upwards, how to automatically bounce up and how to insert and remove the SIM card are all areas of the structural design of the phone. Trivial parts require MD employees to be very familiar with materials and processes.
Motorola V3 set off a craze in the mobile phone market with the thickness of13.9 mm. The selling point of V3 mobile phone is ultra-thin, because the material selection of its mobile phone case is very critical, so the shell of V3 adopts advanced aviation grade aluminum alloy. It can be said that the selection of special shell materials has made V3 successful.
In addition, some users complain that when using some ultra-thin slide phones, they can always feel the front shell of the phone shaking left and right when answering the phone. This is the problem of mobile phone structure design. Because the shell of the mobile phone is too thin, the vibration of the speaker can easily make the body of the mobile phone vibrate during the call.
3. Hardware design of hardware
The hardware is mainly the design circuit and antenna, and the hardware keeps regular communication with MD.
For example, MD requires thin, so the circuit needs to be thin to work. At the same time, HW will also require MD to place the antenna in a large area and far enough away from the battery. HW will also ask ID not to place metal accessories near the antenna and so on. It is conceivable that the manufacturing cost of mobile phones with built-in antennas is 20-25% higher than that of mobile phones with external antennas. The main factor is the design of the antenna, the requirements for materials and the design and manufacturing cost of the circuit are relatively high on average.
Usually, structural designers (MD) and industrial designers (ID) will argue. MD says that ID is a painter, drawing things that no one knows, while ID will say that MD is stupid and doesn't follow their design, so the mobile phone is not easy to sell. Therefore, before designing a new mobile phone, all departments will review the design ideas of ID department. A good ID must be an achievable idea, and the customer experience must feel good. At that time, the ID of Motorola V70 was a good example to realize creativity, and the market reaction in the later period was also good. Although the idea of Siemens Xelibri is also very good and can be realized, it is a pity that the end users are not satisfied with it, so a really good idea should not only look good, be realized, but also be easy to use.
In addition, HW will also quarrel with ID. ID likes to decorate with metal, but metal will affect the design of antenna and easily generate static electricity, so HW will be very angry, and ID/MD will develop new materials to meet the requirements of ID. Nokia 8800 is a good example. It has a metallic feeling without affecting the receiving ability of the antenna.
4. Software software design
Relatively speaking, SW is easier for everyone to understand. Due to the popularity of computers, we often see all kinds of software, the mode of mobile phone operation interface and the realization of mobile phone nine-official operation menu. These are all areas of software design.
SW should fully consider the operability, humanization and aesthetics of the interface. Software testing is very complicated and has various names. SW testing is not only about finding bugs, but also consistency testing and compatibility testing are very important projects. In the current "content-oriented" information age, software is the ultimate behind-the-scenes pillar of mobile phones, and hardware drivers are realized through software. I believe that the conflict between software and hardware engineers will not be less than that of other departments. This relationship goes on and on, so PM (Project Management) is needed to coordinate it.
5. Project Manager (Project Management)
Large-scale companies have very detailed PM allocation. For example, TPM (TechnoloGly for Project Management) is a PM specialized in technology, while ordinary PM only manages the progress of the project and coordinates the work. PM departments usually exist in companies that design, produce and sell their own mobile phones. I'm afraid the position of AM (account manager) is familiar to everyone. As an account manager, it is an indispensable bridge between the internal requirements of the company and the external image of the company.
6. Procurement Resources Development Department
Employees in the resource development department should constantly explore new resources, such as new materials, new mobile phone components, test equipment, etc. When the mobile phone starts trial production, they should ensure that all the production materials needed by the production line are complete.
The small batch trial production of mobile phones not only examines the maturity of software/hardware, but also examines the production technology and production testing technology. At this stage, some mobile phones can't pass this barrier and end in failure. Therefore, this newly designed mobile phone will not appear in the market, and the investment in development funds and manpower is wasted, which is a great loss.
7, QA (quality assurance) quality supervision
The QA department undertakes the whole process quality assurance, urges whether the development process conforms to the scheduled process and ensures the productivity of the project. Many newly designed mobile phones have been abandoned because of some unproductive factors.
Producing a mobile phone is not as simple as doing experiments in the laboratory. Once produced, there are thousands of mobile phones. It is not easy to ensure the quality of every product. Producing a sample of a mobile phone is completely different from producing 654.38+10,000 mobile phones.
For example, restaurants in China are all samples, and McDonald's is a product, so McDonald's can do a lot, and so far, it is true that restaurants in China are not as big as McDonald's for the time being, so mobile phone design companies will establish many processes to prevent the design, development and production of mobile phones.
Not only that, the successful listing of a mobile phone can sell a full house, but also requires close contact with mass mobile phone users, and it can only be successful after user feedback and rapid improvement.
Second, little-known mobile phone testing projects
1, pressure test
Use automatic test software to call 1000 continuously to the mobile phone to check whether the mobile phone will be broken. If something goes wrong, the relevant software needs to be rewritten. So sometimes there are different software versions on mobile phones. Actually, I'll tell you a secret. The more versions of mobile phones, it can be proved that mobile phones were sold without adequate testing before they went on sale.
2. Anti-fall test
The anti-fall test is carried out by a special Pprt reliability laboratory, and the 0.5m micro-fall test needs to be done 300 times on each side (six sides of the mobile phone). The 2m drop test needs to be done once on each side, and the mobile phone also simulates throwing it on the desktop. The battery for mobile phones must pass through a height of at least 4m, and it will not break until it falls to the ground 100 times.
3, high/low temperature test
Let the mobile phone be in different temperature environments and test the adaptability of the mobile phone. The low temperature is generally MINUS 20 degrees Celsius, and the high temperature is about 80 degrees Celsius.
4. High humidity test
It takes about 30 hours to do a dripping test by simulating human sweating with a special cabinet (a certain proportion of salt permeates into water).
5. Dove test (also called boundary tofu test)
Draw 100 squares on the phone case with H4 hardness pencil to see if the paint will come off the phone case. Some mobile phones with strict requirements will apply some "brand-name" cosmetics on the casing of the mobile phone to see if the paint of the mobile phone will smell or fall off because of different chemical components.
6. Reliability test of flip cover
Flip the flip phone 6,543,800 times, and check the wear of the phone case. This is done by a flip simulator, which can set the strength and angle of the flip.
7. Torsion test
Straightener clamps both ends, one on the left and the other on the right. The torque test is mainly to test the strength of the mobile phone shell and large devices inside the mobile phone.
8. Electrostatic testing
The weather in the north is relatively dry, and things that come into contact with metal are prone to generate static electricity, which will lead to the failure of the circuit of the mobile phone. Some poorly designed mobile phones are suddenly damaged in this way. The tool for this test is a copper plate called an electrostatic gun. The electrostatic gun will be set to a high voltage and low current of 10- 15KV, and all metal contacts of the mobile phone will be discharged for about 300ms-2s, which will be carried out in a room with humidity control, and so will the related chargers (Huoniu).
9. Critical life test
Hit the keyboard 65438+ million times with the given force of the machine. If the user presses 100 times, it is 1000 days, which is equivalent to the user using the mobile phone for about three years.
10, dust test
Put the mobile phone in a special box and the tiny sand will be blown up by the hair dryer. After about three hours, turn on the phone and see if there is sand in it. If so, it shows that the airtight design of the mobile phone is not good enough, and its structural design needs to be readjusted.
In addition, the testing of mobile phones also includes more and more bizarre testing items, such as putting mobile phones on iron plates and making phone calls for testing. Because the magnetic field has changed at this time, everything will happen, such as the SIM card can't be found.
Dial the wire in the connector at the bottom of the phone, mainly to see if there is a key in the handbag and the phone will be short-circuited.
There are also tests to see whether the design of mobile phone protection circuit can work normally by deliberately connecting the charger/battery in reverse, tests to make a phone call near a fluorescent lamp, tests to determine the proportion of electromagnetic waves absorbed by the human body, tests to make a phone call near a pacemaker, and so on. All the above tests are indispensable.