Mobile jammer on CDMA signal test

D = the distance between the Tx and Rx Assume in the worst case, the mobile phones from 1 2 1 meters (assume that only the far field effect, the near field factors it is difficult to consider), will be no attenuation between two mobile phones parallel alignment and material, the antenna of mobile phone 2 will receive a signal as high as 83.92 dBm. The receiver of mobile phone 2 will have a -103.92 dBm interference signal, because the attenuation of the antenna to the overpower switch will be 20dB. This example illustrates a mobile phones in a receiving channel noise on the general reasons, according to the case made assumptions, there are many things in the actual execution will cause different results, it will have to know what kind of noise from a mobile phones into another channel. Orientation, distance, switch attenuation, shielding, antenna design and implementation mode, all of these factors will play a role in the whole conversion of noise. Several points of attention. If you pass the "overpower" connection test, the antenna has no connection than the connection. Due to mobile phone design is around spectrum required transmit and receive signal effectively, if by physical CLP connection to test, the antenna or able to receive incoming signals, add in the transmitter and receiver front-end. After the antenna is connected, it may also be able to transmit a large signal to the outside with a higher power when measuring the launch side of the phone. After eliminating the antenna port match (removing the antenna from the antenna connector) on the test frequency, the phone can receive and transmit signals on the high attenuation level. · due to external interference, the RF cable is connected to the mobile phone, so it is important to use the appropriate shielding cable, preferably the n-type connector with a triple screen cable. Of mobile phone shielding will greatly attenuation, when testing the interference from other mobile phones or unknown noise spectrum, example of mobile phones for interference in the concrete in front of the test to determine the screening attenuation is very useful. Screen mobile phone is not affected by outside interference is not the only way to eliminate noise, carefully deal with all the phone under test frequency can effectively avoid the interference, which requires more complex control software initialization, the channel number and frequency to eliminate the conflict frequency. · keeping a close eye on the distance between phones that are using two of the same frequencies can be used repeatedly. Examples of cell phone jammer are very useful in determining the safe reuse distance.

 

A major concern for mobile phone testing is its response in a wide range of dynamic ranges. CDMA mobile phones with analog or TDMA is especially, because it is within the range is very wide bandwidth with 80 db dynamic range, the large dynamic range is a unique advantage of CDMA technology, CDMA mobile phone and base station transmission power on average were lower than other technologies. Due to the mobile phone to receive below - 104 DBM signal, so the rules within the spectrum of noise will affect the minimum performance standards such as TIA/EIA - 98 - c listed a number of tests, so understand the impact of interference of CDMA mobile phone receiver test is very important. When the noise affects the test of the mobile phone, the structure of the phone should be understood before considering the noise. There is a transmitter (TX) and a receiver (RX) in the cell phone, and the transmitter emits power between + 30dBm and -55dbm, and the receiver range is between -20dbm and -108dbm. CDMA mobile phone transmitters and receivers of large dynamic range, more than 80 db, maximum power (grade Ⅲ phones as + 23 DBM) and receiver sensitivity (104 DBM) is the most important indicators need to know. The CDMA mobile phone test will carry out several tests to ensure that the phone meets certain standard requirements. For example test mobile phone transmitter power guarantee transmission power range is accurate in a wide dynamic range, particularly to test mobile phone maximum transmitted power, to ensure that mobile phone radiation power near the biggest EIRP (effective isotropic radiated power) regulation, the smallest value of Ⅲ mobile transmission power level range is + 23 DBM ~ + 30 DBM. Compared with noise, the measurement of the power of the instrument is larger than the noise, so the noise is generally only an insignificant factor in the total power measured. Mobile launcher also to test to see whether conform to the requirements of the lowest emission, CDMA must be smaller than the minimum power emission regulations mobile launch - 50 DBM, even in this case, launch the channel noise influence is usually small and will not affect the minimum power measurement. The problem of measuring the lowest power of CDMA is generally caused by the minimum noise of the power meter used. The receiver sensitivity measurement will be affected by the noise on the cell phone reception channel. The sensitivity of CDMA mobile phone receiver is -104dbm, and the phone must be able to demodulate the positive link signal with -104dbm transmission with the error rate of less than 0.5%. Eb/Nt is said mobile phone accurate signal receiving and demodulation is link capacity parameters, Eb is a communication channel of each energy, Nt is receiving the total noise on the bandwidth, it is a bit like analog circuits of signal to noise ratio (S/N). When the Eb/Nt ratio increases, the receiver can better demodulate the signal; As Eb/Nt decreases, the phone is likely to misinterpret positive link signals. Positive link communication channel of the actual energy than e. low total positive link power - 104 dBm 15.6 dB, in other words, in the measurement of mobile phone to receive the actual signal is 119.6 dBm, starting from this, we will be in a mixture of Walsh code is link in the content of the reference signal. According to different mobile phone receiver design tolerance, its sensitivity to noise is not the same, usually when mobile performance at the margins on general forward link channel will have the noise problem, there are many factors affect the Eb/Nt in the Nt. The noise source on the receiving channel.

wifi signal jammer device

The essence of noise Nt in KTB is thermal noise, which is always present in the environment. Thermal noise is also known as KTB background noise.

K = boltzmann constant (1.38 x 10-23) T = reference temperature (kelvin) B = receiver effective noise bandwidth for CDMA systems working at 1.23 MHz bandwidth, thermal noise about -113dbm. You may ask, how does the receiver solve the -119dbm signal by -113dbm? This is because the CDMA processing gain is nearly 21dB, and 14.4 KBPS / 9.60 KBPS to 1.228 Mcps. Component noise.
The noise of the receiver front-end components (lower converters and amplifiers) will also produce Nt, affecting the sensitivity of the phone, which is the level of sensitivity of the -104dbm specified in the forward link power test level. All other noise factors raise Nt, and affect the success of the sensitivity test. Compared with the mobile phone at the edge of the performance index, the mobile phone with a certain tolerance will have more space to accommodate the increased noise. Environmental noise.
Noise from unknown sources also reduces Eb/Nt of forward communication channels. Such as any circuit of transmission power spectrum noise can be generated depends on the signal itself or two intermodulation interference signal if there is a higher power to fall on the measured bandwidth, it remains to be seen whether it appeared together with sensitivity test. External units also generate interference noise, especially for AMPS systems when testing 800MHz CDMA mobile phones. There are even reports pointed out that microwave ovens also interferes with cell phone sensitivity test, there are a lot of production factory lunch near the production line, if found a large number of sensitivity or rest at noon time problem, you should know where to find the reason. Close contact with the test.
In a production environment, there are a lot of test bed according to the test plan in each stage of testing the phone, that is to say is one stage test mobile phone may interfere with another phone in different stages of testing. Generally speaking, the mobile phone that is interfered with is the sensitivity. Remember positive link set in - 104 DBM, main interference may be positive link adjacent cell phones are to receive a large signal, and just a mobile phone in a sensitivity test, the forward link signal set in - 104 DBM or below. The positive link is set at a higher level of mobile phone testing including dynamic range, minimum emission power and open loop range. Generally speaking, the positive link of these tests is -25dbm. The receiver and emitter are coupled.
Influence Nt another noise source is the size of a mobile phone transmitter and receiver of * coupling, which is about the design of the mobile phone, because there is no segregation between receive and transmit channel or match. The cost of the solution is high and difficult because it is a design problem. Forward and reverse links between 45 or 80 MHZ, it respectively for unit band and PCS band interference between link is highly segregated, in mobile phone front will find from one link to another link of the crosstalk phenomenon, this is a problem of mobile phone front end design. The receiver channel sensitivity is listed on the main source of spectrum noise, and now let's take a look at how these spectrum noises get into the cell phone reception channel. We usually adopt two methods to test mobile phone, is the most commonly used by physical RF connection test, which is often referred to as "b" connection, instead of the commonly used test connection method is directly through phone antenna. We assume that all the tests discussed here are done through the physical "overpower" connector, which determines whether or not to connect the antenna based on the phone's production process. In order to find the worst case, we assumed the antenna was assembled into the phone. In most cases, the mobile phone will be susceptible to noise due to poorly shielded RF cables or unconnected antenna ports. Antenna ports are generally the main source of noise, especially if the antenna is being tested. Figure 3 said the ongoing sensitivity test of mobile phone to another power forward link - 25 DBM phone might affect, mobile phones is ongoing testing of 1, has the high - 25 DBM power forward link. Since the power of cell phone 1 transmitting channel is -25dbm, assuming that the attenuation of the unconnected switch is 20dB, the signal of the unconnected port via the antenna may be as high as -45dbm. The attenuation value is changed by design. Because the signal transmitted through the antenna is transmitted through air, its propagation attenuation can be calculated by Friis transformation equation: Pt = transmission power Gr = antenna transmission gain
Gt = antenna receiving gain
Lambda = wavelength

Addressing the problem of interference receiver, especially in a production environment, find out because of the sensitivity test in cause of failure and lower the production is not an easy thing, the location of the factory, working time, test way and other seemingly unrelated factors resulted from the stochastic sensitivity. Taking a step back to recognize the main source of interference noise and how these sources affect the receiver's front end, it is easier to solve the problem of low sensitivity test pass rate.