1. The working principle of mobile phones:
Generally speaking, we ordinary users only need to learn how to use mobile phones well, and there is no need to delve into its specific working principles; however, in In the process of using a mobile phone, due to the influence of various factors, the mobile phone will inevitably malfunction. If you have to send it to a professional repair shop for repair every time you encounter even the smallest malfunction, you may find it troublesome. If you have considerable electrical knowledge, you may want to learn to repair it yourself, but to learn to repair it, you must first be familiar with the working principle of the mobile phone. Only in this way can you determine the cause of the malfunction and find the corresponding solution. At the same time, understanding the working principle of mobile phones can also serve as a reserve of knowledge for ordinary people. In order to help these users who love mobile phones learn to repair quickly, the author will use Motorola mobile phones as an example to introduce in detail how mobile phones work.
The reason why mobile phones can communicate with each other is the result of the coordinated work of three parts. These three parts are the radio frequency part, the logic part and the power part. To understand the working principle of mobile phones, you only need to understand this. Just how the three parts work is enough. The author will introduce the working principles of these three parts separately.
Radio frequency part
Usually the radio frequency part is composed of a signal receiving part and a signal transmitting part. When the mobile phone receives a signal, it first uses the antenna to pass the received 935-960MHz radio frequency signal through U400 and SW363 to separate the transmitted signal and the received signal so that the sending and receiving do not interfere with each other. Input the fifth pin output from the fourth pin of U400 and enter the receiving front-end loop. The working status of U400 is controlled by the potential of the third pin, which in turn is controlled by the TXON and RXON signals from the CPU. The RF signal passing through the antenna switch is first filtered by the bandpass filter FL451, and then sent to the high-frequency amplifier tube Q418 for amplification. The output of Q418 is filtered by FL452 and then sent to the Q420 mixing tube for mixing. The local oscillation signal is generated by RXVCO, and is filtered by FL453 before being sent to the base of Q420 for mixing. Taking the difference, a 153MHz intermediate frequency signal is output from the collector of Q420. After filtering by FL420, a 153MHz pure medium-frequency diesel engine signal is obtained. Now it is amplified by Q421 and sent to pin 31 of U201. The 153MHz IF signal and the 153MHz carrier signal are demodulated in 32D53 to generate RXI and RXQ analog baseband signals, which are sent to 14# and 15# of U501 via 46# and 48# of U201. After A/D conversion in U501, it is sent to a digital signal processor for further processing. The 153MHz carrier wave consists of U201's 41#, 42#, and 43# connected to the 306MHz oscillation circuit composed of peripheral circuits to form a 306MHz Hui wave signal, which forms a 153MHz carrier wave after the second frequency. For the transmitting part, the TXIN, TXIP, TXQN, and TXQP transmit frequency band signals output from 21#, 22#, 23#, and 24# of 501 enter 61#, 62#, 63#, and 64# of U201. 6#, 7#, and 10# of U201 are externally connected to a 216MHz VCO to generate a 216MHz carrier signal. This signal is divided by the frequency divider in U201 to generate a 108MHz transmit intermediate frequency signal. The four modulated signals complete 108MHz carrier modulation in U201 and are output from pin 4 to 4# of U300. U300 completes the transmission of the sampling signal and the TXVCO phase gentle frequency, and takes the difference to get the 108MHz signal and the TXIF phase detection of the 4# input to generate a phase detection error voltage, which is output from the 8th pin to control the capacity of the varactor diode CR300 to change the oscillation of the TXVCO Frequency, the 890-915MHz transmit signal output from the C pole of Q300 is amplified by the Q301 preamplifier and driven by Q302, and then enters the power amplifier Q302. The amplified signal enters the first pin of the antenna U400, and then is emitted from the 4# sending antenna of U400.
Logic part
In the logic part, the received RXI and RXQ analog baseband signals complete D/A conversion, decryption and adaptive equalization inside the modem U501, and then the digital baseband signal is transferred from U501 to The 6# is sent to the 10# of the CPU, and the channel is decoded in the CPU. After the error correction code source is removed and the real control information is obtained, the recovered voice data flows through the data line and address line, and is transmitted to the voice unit U801 for decoding. The generated digital voice signal is sent from 78# of U801 to 8# of PCM decoder U803. The digital voice signal completes pressure reduction and A/D conversion in the PCM decoder, and then passes through the digital volume positioner to adjust the received signal and volume. Then the analog audio signal is output from U803's 4# to U900's 6# and 21 #. The ringing signal input from 6# is amplified by the internal ringing driver and drives the ringer to send audio signals from the 4# and 5# outputs of U900. It is input from 21# and passes through the internal audio amplifier. 19# and 20# output amplified voice signals to drive the earpiece to sound. When our user is speaking, the voice is sent to 9# of the power integrated circuit U0- after being converted by the earpiece. After being amplified by the internal audio, the amplified analog audio signal is output from 10#.
The signal is sent to 18# of PCM codec U803 and PCM encoding is completed inside U803. The PCM signal output from 13# is sent to 89# of the speech encoder 801. The voice data line and address line are inserted into U801 to flow the voice data to the central processor U701. After U701 completes the channel coding, the voice data flow passes through U701 11# is sent to the 4# of the modem U501. After the signal undergoes D/A conversion, encryption and other processing in U501, the generated four-way modulated signals TXIP, TXIN, TXQP and TXQN are sent to the transceiver intermediate frequency circuit U201. To generate and transmit intermediate frequency ITX and IF signals.
Power supply part
As for the power supply part, once we install the battery on the mobile phone, the electronic Q999 is connected; at the same time, 48# of 32D54 is connected to the positive pole of the power supply. At this time, if we press Press the power button, U900's 24# changes to low level, and the four stable output voltages of U900 are R275V, L2.75V, R4.75V, and L5.0V. No. 30# generates a reset signal and No. 27# generates a boot application signal. The 13MHz clock oscillator is composed of 32D53, 13MHz crystal and transformer diode to generate a 13MHz clock. After internal shaping and amplification in 32D53, it is sent from the 59# output to the 17# of the buffer interface circuit U703, and from the 37# of U703 Send the CPU's 50# to send the boot maintenance signal to the U900's 29# to maintain normal booting. In addition, the collector voltages of Q202 and Q203 are both 2.75V, which supply power to the internal receiving or transmitting circuit of 32D53. The L5.0V sent by U900 No. 3 supplies power to the negative voltage generating circuit. Version, SIM card and PCM codec U803 are also powered by L5.0V. The R2.75V voltage sent by U900 No. 28 supplies power to all logic modules. The 2.75V voltage sent out by U900 No. 28 is supplied to the RF part. The R4.75V voltage sent by U900 No. 41 supplies power to the transceiver IF circuit 32D53, and the VXW conversion voltage output by U900 No. 37 supplies power to the emitters of Q202 and Q203.
Since the models and manufacturers of each mobile phone are different, the working principle described above may not apply to some mobile phones, but the general workflow should be the same.
2. Knowledge related to mobile phone manufacturing
Nowadays, mobile phones have gradually broken away from their status as simple communication tools and gradually transformed into a multimedia and information terminal device. They will be used for daily communication and entertainment in the future. , financial management and other activities can all be carried out through mobile phones. Every time you see a novel mobile phone with high performance and bright appearance, are you curious about how such a mobile phone is designed and manufactured?
So today we try to use a technical and objective perspective to briefly describe the structure of the mobile phone design department and the relationship between departments. Finally, we will show you the various tests of mobile phones from manufacturing to launch. So that everyone can learn more about mobile phones and cherish your favorite phone more. Maybe you won’t replace it easily in the future!
1. Mobile phone design process
Using a simpler explanation, a general mobile phone design company needs to have six basic departments: ID, MD, HW, SW, PM , Sourcing, QA.
1. ID (Industry Design) Industrial design
Including the appearance, material, feel, color matching of the mobile phone, the realization of the main interface and the design of color.
For example, the translucence of Motorola’s “clear” flip cover, the arc-shaped appearance of Nokia 7610, and the sunshine orange of Sony Ericsson W550. These special feelings and experiences given to users all belong to the category of mobile phone industrial design. Whether a mobile phone can become a best-selling product, the industrial design of mobile phones is particularly important!
2. MD (Mechanical Design) structural design
Selection of the front shell, back shell, and camera lens position of the mobile phone, the fixing method, how to connect the battery, and the thickness of the mobile phone degree. If it is a slider phone, how to make the phone slide up, how to automatically pop it up, and how to insert and remove the SIM card are all aspects of the structural design of the phone. Complicated parts require MD staff to be very familiar with materials and processes.
Motorola V3 set off a craze in the mobile phone market with its thickness of 13.9mm. The V3 mobile phone is ultra-thin as its selling point. Because the choice of material for its mobile phone casing is very critical, the casing of V3 is made of aviation-grade technology with advanced technology. Made of aluminum alloy material. It can be said that the choice of special shell material has contributed to the success of V3.
In addition, some users reported that when using some ultra-thin slider mobile phones, they can always feel the front shell of the mobile phone shaking left and right when answering calls. This is a problem with the structural design of the mobile phone. Because the mobile phone The casing is too thin, and the vibration of the speaker during a call can easily cause the body of the phone to vibrate.
3. HW (Hardware) Hardware Design
Hardware mainly designs circuits and antennas, and HW needs to maintain regular communication with MD.
For example, MD requires thinness, so the circuit must also be thin to make it work. At the same time, HW will also require the MD to place the antenna in a relatively large area and far enough away from the battery. HW will also require the ID not to place metal accessories near the antenna, etc. It is conceivable that the manufacturing cost of a mobile phone with a built-in antenna design will be 20-25% more expensive than a mobile phone with an external antenna design. The main factors are the antenna design, material requirements and circuit design and Manufacturing costs are generally higher.
Usually there will be arguments between structural designers (MD) and industrial designers (ID). MDs say that IDs are all painters and draw things that no one can make, while IDs will say that MDs are stupid and don’t follow the rules. Their design is done, so the phone doesn't sell well. Therefore, before a new mobile phone is designed, each department will review the design creativity of the ID department. A good ID must be an achievable idea, and the customer experience must be good. Motorola's V70 ID was a good example of the realization of creativity, and the market response was also good later. Although Siemens' Xelibri's creativity is also very good and can be realized, it is a pity that the final customer experience is not good, so A truly good idea must not only look good and be achievable, but also be easy to use.
In addition, HW will also quarrel with ID. ID likes to use metal decoration, but metal will affect the design of the antenna and easily generate static electricity, so HW will be very annoyed, and ID/MD will develop new materials. In order to cope with the ID requirements. Nokia 8800 is a good example, it has a metallic feel without affecting the antenna's reception ability.
4. SW (Software) software design
Relatively speaking, SW is easier for everyone to understand. Due to the popularity of computers, we have been exposed to various kinds of software to the greatest extent. Such software, the mode of mobile phone operation interface, and the implementation of the nine-function operation menu of mobile phones that we often see are all within the scope of SW design.
SW must fully consider the operability of the interface, whether it is user-friendly, and whether it is beautiful. SW testing is very complex and has many names. SW testing is not only looking for bugs. Consistency testing, compatibility testing, etc. are all very important items. In the current "content-oriented" information age, software is the key to mobile phones. The final pillar behind the scenes, the hardware is driven by software. I believe the conflicts between software and hardware engineers will be no less than in other departments. This relationship goes around and around, so there is a need for a PM (Project Management) project. Management came to coordinate.
5. PM (Project Management) Project Management
PMs in large-scale companies are very detailed, such as TPM (Technology Of Project Management), which is a PM who specializes in technology. An ordinary PM only manages the progress and coordination of the project. The PM department usually exists in companies that design, produce and sell mobile phones by themselves. The position of AM (Account Manager) is probably familiar to everyone. As an account manager, Internally, the company represents customers to make requests, and externally, it represents the company's overall image, playing an indispensable bridge role between the two.
6. Sourcing Resource Development Department
Employees in the Resource Development Department must constantly explore new resources, such as new materials, new mobile phone components, testing equipment, etc. When mobile phones When starting trial production, they must ensure that all production materials needed for the production line are available.
The small-batch trial production of mobile phones not only examines the maturity of software/hardware, but also examines the production process and production testing technology. Some mobile phones fail to pass this stage when they reach this stage. If not, it will end in failure. As a result, this newly designed mobile phone will not appear on the market, and the investment in development funds and manpower will be wasted, which is a huge loss.
7. QA (Quality Assurance) quality supervision
The QA department is responsible for the quality assurance of the entire process, supervises whether the development process conforms to the scheduled process, and ensures the producibility of the project. There are many newly designed mobile phones that were abandoned because they encountered some factors that could not be produced.
Producing a mobile phone is not as simple as doing an experiment in a laboratory. Once produced, there are thousands of units. It is not a simple and easy task to ensure the high quality of each product. Producing a prototype of a mobile phone and producing 100,000 mobile phones are completely different things.
For example: Chinese restaurants only produce samples, while McDonald’s produces products, so McDonald’s can be very big. And so far, Chinese restaurants have not yet reached the scale of McDonald’s. In fact, that’s why mobile phone design companies have established many processes to prevent the design and development of mobile phones from being put into production.
Not only that, the successful launch of a mobile phone and its success requires close contact with mass mobile phone users, user feedback and rapid improvements.
2. Little-known mobile phone test items
1. Stress test
Use automatic test software to make 1,000 calls to the mobile phone continuously to check whether the mobile phone can A malfunction occurred. If something goes wrong, the relevant software will need to be rewritten. So sometimes there will be different software versions on the mobile phone. In fact, let me tell you a secret. The more versions of the mobile phone, this can prove that the mobile phone was released without sufficient testing before it was launched for sale.
2. Drop resistance test
The drop resistance test is carried out by the specialized Pprt reliability laboratory. The 0.5m micro drop test needs to be done 300 times/surface (mobile phone There are six sides). The 2m drop test needs to be done once for each side, and it also simulates a person throwing the phone on the table. The battery used in the phone must also pass through a height of at least 4m, and be hit and dropped to the ground 100 times alone without rupture. Appear.
3. High/low temperature test
Let the mobile phone be exposed to different temperature environments to test the adaptability of the mobile phone. The low temperature is generally minus 20 degrees Celsius, and the high temperature is around 80 degrees Celsius.
4. High humidity test
Use a special cabinet to conduct a drip test to simulate human sweating (a certain proportion of salt penetrates into the water). About 30 tests are required. Hour.
5. Hundred grid test (also called tofu test)
Use a H4 hardness pencil to draw 100 grids on the phone case to see if the paint will fall off the phone case. Some mobile phones with stricter requirements will apply some "name-brand" cosmetics on the phone's casing to see if the paint on the phone will smell or peel off due to different chemical compositions.
6. Flip reliability test
Flip the flip phone 100,000 times to check the wear and tear of the phone case, using a flip simulator, which can Set the strength, angle, etc. of the flip cover
7. Torque test
Clamp the two ends of the straight machine with clamps, twist one to the left and the other to the right. The torque test mainly tests the strength of the mobile phone casing and large components inside the mobile phone.
8. Static electricity test
In the northern region, the weather is relatively dry, and touching metal objects with your hands can easily generate static electricity, which can cause breakdown of the circuit of the mobile phone. Some poorly designed mobile phones are It was suddenly damaged like this. The tool for this kind of test is a copper plate called an "static gun". The static gun will be adjusted to a high voltage and low current of 10-15KV, and conduct a discharge test on all metal contact points of the mobile phone. The time is about It is about 300ms-2s and is conducted in a humidity-controlled room. The relevant charger (Fire Bull) will also undergo the same test and must pass the test before it can be released from the factory.
9. Key life test
Use the machine to hit the keyboard 100,000 times with a set force. If the user presses the key 100 times, it will be 1,000 days, which is equivalent to the user's use Cell phones are about three years old.
10. Sand and dust test
Put the phone into a specific box, and the fine sand will be blown up by the hair dryer. After about three hours, open the phone and check whether there is any dust inside the phone. Sand comes in. If so, then the sealing design of the mobile phone is not good enough and its structural design needs to be readjusted.
In addition, the test of mobile phones also includes more bizarre test items, such as placing the mobile phone on an iron plate and making a call. Since the magnetic field changes at this time, anything will happen, such as Can't find SIM card etc.
Use a wire to poke around in the connector at the bottom of the phone. The main reason is to consider whether there will be a short circuit problem in the phone if there is a key in the handbag.
There are also tests of deliberately reversing the charger/battery to see if the protection circuit design of the mobile phone can operate normally, tests of making phone calls close to fluorescent lamps, tests of the proportion of electromagnetic waves absorbed by the human body, and tests of pacing close to the heart. The various tests mentioned above are indispensable.