Basic knowledge of antenna
 
First, the antenna: (antenna) is the high-frequency current or waveguide form of energy converted into electromagnetic waves transmitted out to the provisions of the direction or the direction of the electromagnetic waves from a certain reduction of the high-frequency current of a device.
Second, the antenna Category:
1) Classification by use: can be divided into communication antennas, TV antennas, radar antennas, etc.;
2) Press the working frequency band Category: can be divided into short-wave antenna, FM antenna, microwave antenna;
3) classification by directional: can be divided into omnidirectional antenna, directional antenna;
4) Press the shape classification; can be divided into linear antennas, planar antennas.
Third, the omni-directional antenna, that is, the performance graph in the horizontal direction is 360 ° are uniform radiation, which is usually referred to no direction, the performance graph in the vertical direction to have a certain width of beam, beam width under normal circumstances the more small, the greater the gain.
Fourth, directional antenna, in the performance graph in the horizontal direction for a certain angle range of radiation, which is usually referred to a direction perpendicular to the direction of the map in the performance of a certain width of the beam, with the omni-directional antennas, beam width The smaller the greater the gain.
Fifth, the gain
    Gain refers to: the input power equal conditions, the actual antenna radiating elements and the ideal premises in the same point in space generated by the ratio of signal power density. It quantitatively describes an antenna input power to the degree of concentration of radiation. Antenna gain is obviously closely related, the narrower the main lobe pattern, side lobe smaller, the higher the gain. Can be to understand the physical meaning of ------ to gain a certain distance of a point on a certain size of the signal, if the ideal point source as a non-directional antennas, you need 100W of input power, and with a gain G = 13 dB = 20 of a directional antenna as the transmitting antenna, the input power of only 100 / 20 = 5W. In other words, an antenna gain to the maximum radiation direction of the radiation effect, with no direction of an ideal point source compared to a multiple of the input power amplifier.
Sixth, the antenna operating frequency range (band width)
    Both the transmitting antenna or receiving antenna, they are always at a certain frequency range (band width) to work, the antenna bandwidth, there are two different definitions ------
  A means: in the standing wave ratio SWR ≤ 1.5 conditions, the antenna frequency band width;
  A means: down 3 dB antenna gain within the band width.
   In the mobile communication system, usually defined by the former, specifically, the bandwidth of the antenna VSWR antenna SWR is less than 1.5, the antenna operating frequency range.
   In general, all work within the band width of frequencies, the antenna performance is different, but the performance degradation caused by this difference is acceptable.

VII, 3G introduction of knowledge

What is 3G licenses
Wireless communications and multimedia communications with the Internet and other new generation mobile communication system operating license. Like, like all sectors of the business license, and must have state approval to operate this business departments
* Why 3G licenses issued
According to the Chinese market space, and promote competition in the telecommunications market in China; effective use of frequency; specification section number, section number will be from 15 to 18; control operating costs related to the development of China's mobile communication industry.
Operators in order to get any 3G licenses, should have the strength in five areas:
First, the network strength. Second, the strength of need for funds. Third, technical strength. Fourth, the business strength. Fifth, the user strength. China Telecom, China Netcom's PHS system, China Mobile, China Unicom. So you said is wrong, not the package does not include the question of who is the manufacturer sure you say no such power.
· 3G standard of the three standard
TD-SCDMA: full name of the Time Division - Synchronous CDMA (Time Division Synchronous CDMA), the standard proposed by the Chinese 3G standard.
Features: In the spectrum efficiency, flexibility on business support and other unique advantages. Internet speed is four times CDMA1X, free T network and G network in the conversion.
 
 
WCDMA: also known as WCDMA, all known as Wideband CDMA, also known as CDMA Direct Spread, intended for the wideband code division multiple access, which is based on the GSM network developed 3G technology standard, is Europe's wideband CDMA technology.
Characteristics: a higher spreading gain, the development of larger space, the strongest global roaming, but the technical maturity of the general.
CDMA2000: CDMA2000 is a narrow-band CDMA (CDMA IS95) broadband technology from CDMA technology, also known as CDMA Multi-Carrier, North America led by a Qualcomm proposed that South Korea has now become the dominant standard.
Features: CDMAOne from the original structure can be directly upgraded to 3G, the construction cost.
The status of the global 3G development of the root *
67 around the world have commercial 3G network, as of August this year, 45 countries around the world have issued 146 permits, and now is 138 effective
  

Pat and telecommunications technical terms explained: What is CDMA and CDMA2000


    CDMA is a CDMA (Code-Division Multiple Access) technology, abbreviation of digital mobile communications in recent years in the process of the emergence of a sophisticated wireless spread spectrum communication technology, it can meet the market for mobile communications capacity and high quality requirements and has high spectrum efficiency, voice quality, confidentiality, call drop rate is low, electromagnetic radiation, large capacity, wide coverage cover features, can significantly reduce investment and lower operating costs.

 CDMA was first introduced by the Qualcomm, and the same GSM, CDMA also has 2 generation, 2.5G and 3G technology. China Unicom will be launched later this year are 2.5 generation CDMA technology. CDMA is considered to be the 3rd generation mobile communication technology of choice, the current standards are WCDMA, CDMA2000, TD-SCDMA.

What is CDMA2000?

CDMA2000 is the TIA standards organization used to refer to the name of the third generation of CDMA. TIA for the 3G CDMA specification is called IS-2000, the technology itself is known as CDMA2000.
  The first phase, also known as CDMA2000 1x, it gives the existing IS-95 system has a communications company can double its overall system capacity, and increased data rates up to 614kbps. CDMA2000 1x higher than technical progress, including 1xEV (high-speed data rate). Introduced by the QCT MSM5000 chipset solution backward compatible CDMA2000 cdmaOne (IS-95 CDMA).


    Organizations to develop by the 3GPP2 CDMA2000 standard, the version including the Release 0, Release A, EV-DO and EV-DV, Release 0 followed the main features of the core based on ANSI-41D network, the wireless access network and core network to support packet services to increase network entities, this version has been stable. China Unicom's CDMA Phase II is about to open is used in this version, the highest single-carrier uplink and downlink rate can reach 153.6kbit / s. Release 0 Release A is the strengthening of the highest rates of single-carrier can reach 307.2kbit / s, and packet voice services and support concurrent operations. EV-DO uses a separate carrier to support data services available in the standard carrier of 1.25MHz, while providing voice and high-speed packet data service, the maximum rate of up to 3.1Mbit / s.



What is 3G
3G, the third generation digital communications. In 1995 came the first generation analogue phones (1G) can only make voice calls; 1996 and 1997 the second generation appeared GSM, TDMA and other digital mobile phone standard (2G) will increase the function of receiving data, such as receiving e-mail or web; third-generation main difference with the previous two generations of voice and data in the transmission speed of the upgrade, it can be better in the global seamless roaming, and handle images, music, video streaming and other forms of media of services including web browsing, conference calls, e-commerce and other information services, taking into account also the second-generation system with the existing good compatibility. In order to provide this service, wireless network must be able to support different data transfer speed, which means that in the indoor, outdoor and vehicular environments, respectively, can support at least 2Mbps (megabits / second), 384kbps (kilobits / second) and 144kbps transmission speed. (This value will change according to the network environment.)

The so-called 3G standard

International Telecommunication Union (ITU) is currently a total of four major global 3G standards identified, they are WCDMA, CDMA2000 and TD-SCDMA and WiMAX. One TD-SCDMA is China's self-developed 3G standard.