The difference between omnidirectional antenna and directional antenna

Antennas have different radiation or receiving capabilities in different directions in space, which is the directivity of the antenna. Depending on the directivity, there are two types of antennas: omnidirectional and directional.

Omnidirectional Antenna:

Omnidirectional antenna, it is shows uniform radiation at 360° on the horizontal pattern, which is commonly referred to as non-directional. In general, the smaller the lobe width, the greater the gain. Omnidirectional antennas are generally used in communication systems with short distances, large coverage areas and low prices. The gain is generally below 9dB. The figure below shows the signal radiation pattern of an omnidirectional antenna. (The radiation range of the omnidirectional antenna is more like an apple)

Omnidirectional antenna

Omnidirectional antenna

Directional Antenna

Directional antennas show a certain angular range of radiation on the horizontal pattern, which is usually said to have directivity. Like the omnidirectional antenna, the smaller the lobe width, the greater the gain. Directional antennas are generally used in communication systems where the communication distance is long, the coverage area is small, the target density is high, and the frequency utilization rate is high.

From the point of view of gain, there is no difference between the two antennas, but there is a very important point: Because of its sharp pointing, the directional antenna is well shielded from the interference signal from the pointing out, which is also very useful for evaluating the receiving effect. Important indicator! We can also think about the relationship between omnidirectional antennas and directional antennas in this way: omnidirectional antennas will transmit signals in all directions, and the signals can be received front, back, left, and right. The directional antenna is like a strong reflective surface behind the antenna. , The signal can only be transmitted to the front, and the signal to the back is blocked by the reflective surface and reflected to the front, which strengthens the signal strength in the front. (The main radiation range of the directional antenna is like an inverted, incomplete cone)

 

Omnidirectional and Directional Antenna

Omnidirectional and Directional Antenna

Through the above analysis, we can visually recognize what is an omnidirectional antenna and what is a directional antenna. So what should be paid attention to in actual application?

If the antenna selection needs to meet multiple sites, and these sites are distributed in different directions of the AP, omnidirectional antennas are required; if they are concentrated in one direction, it is recommended to use directional antennas; in addition, consider whether the antenna joint form is compatible Whether the AP matching and antenna gain size meet your needs; the antenna installation For outdoor antennas, lightning protection equipment needs to be added between the antenna and the wireless AP; for directional antennas, pay attention to the front of the antenna facing the direction of the remote site; the antenna should be installed At the highest possible position, the line of sight between the antenna and the site is as high as possible (visible to the naked eye, avoid obstacles in the middle).

Introduction to the use of coaxial connectors

Coaxial connector is one of the indispensable components in the radio frequency signal transmission line, and its main function is to play a role in connection. With the development of radio frequency communication technology, the scale of radio frequency signal transmission networks has become larger and larger, and the use of radio frequency signal transmission lines has become more and more extensive. Correspondingly, more and more places where coaxial connectors are used are in use. In the process, in order to meet various usage requirements, some different types of RF coaxial connectors have appeared, and different types have different uses. Let’s talk about the situation in this regard.

RF coaxial connector

RF coaxial connector

Generally, the structure and purpose of the radio frequency connection tools are mainly divided into three different kinds of soups, namely, ordinary radio frequency coaxial connectors, large and small radio frequency coaxial connectors, and single-wire to multi-wire radio frequency coaxial connectors. , Ordinary radio frequency coaxial connector is the basic model of radio frequency coaxial connector, and also the simplest radio frequency coaxial connector. The purpose of this connector is to connect with the same interface model. Big change to small radio frequency coaxial The purpose of the connector is to connect between interfaces of different thicknesses, because coaxial cables are divided into thick cables and thin cables. Thick cables are used to build the trunk of the radio frequency signal transmission network, and thin cables are used to connect to thousands of homes. To realize the connection between the thick cable and the thin cable for the branch line of ten thousand households, it is necessary to use large and small RF coaxial connectors. Single-wire to multi-wire RF coaxial connectors are the same RF coaxial connectors with a single inlet and multiple outlets. Shaft connector, its main purpose is to establish multiple radio signal transmission sub-line, for example, there are two TV series at home, but there is only one cable TV signal line, you can use single-line to multi-line RF coaxial connector to change it Two lines.

In addition, in the radio frequency signal transmission network, the audio encoder is also an indispensable device. Its main function is to turn the audio signal into a digital signal, and then into a radio frequency signal through a certain path, so that the audio can be The radio frequency signal transmission network spreads. The use of radio frequency coaxial connectors is very extensive, covering all aspects of people’s lives, so the procurement market for radio frequency coaxial connectors has also become popular.

Introduction of RF coaxial connector

Coaxial connector, (some people also call it radio frequency connector or RF connector. In fact, radio frequency connector is not exactly equivalent to coaxial connector. Radio frequency connector is from the perspective of the frequency of use of the connector. Coaxial connectors are classified from the structure of the connector. Some connectors are not necessarily coaxial, but they are also used in the radio frequency field. Coaxial connectors can also be used in low frequencies, such as common audio earphones. Plug, the frequency does not exceed 3MHz. From a traditional point of view, radio frequency refers to the MHz category. Nowadays coaxial connectors are often used in the microwave field. In the GHz category, the term radio frequency has always been used, overlapping the term microwave), It is a branch of the connector, which has the commonality of the connector and its particularity.

rf connector,RF coaxial connector

rf connector,RF coaxial connector

The coaxial connector has an inner conductor and an outer conductor. The inner conductor is used to connect the signal line and the outer conductor is not only the ground wire of the signal line (reflected on the inner surface of the outer conductor), but also plays a role in shielding the electromagnetic field (shielding the internal electromagnetic waves from the outside The interference acts on the inner surface of the outer conductor, and the shielding of the external electromagnetic field from the internal interference acts on the outer surface of the outer conductor. This feature gives the coaxial connector great space and structural advantages. The outer surface of the inner conductor of the coaxial connector and the inner surface of the outer conductor are basically cylindrical-special cases are often required for mechanical fixing and have a common axis, so they are called coaxial connectors.

rf connector,rf connector,RF coaxial connector

rf connector,rf connector,RF coaxial connector

Among the several forms of transmission lines, coaxial cables are commonly used because of their outstanding advantages (simple structure, high space utilization, easier **, and superior transmission performance). Demand, the coaxial connector will be applied. Due to the superiority of the coaxial structure, the continuity of the characteristic impedance of the (coaxial) connector (relative to other connectors) is more easily guaranteed, the transmission interference and interference (EMI) are very low, and the transmission loss is almost unique. The ground is used in radio frequency and microwave fields. And because it is almost absolutely used at high frequencies, it produces some. Different from the electrical performance requirements of other connectors.

Introduction to multiple input and multiple output antennas

The full name of MIMO is Multi Input Multi Output (Multi Input Multi Output). By using multiple antennas, MIMO antennas can achieve higher throughput and transmission distance than a single antenna under the same radio transmission power. Where multiple antennas are used at the source (transmitter) and destination (receiver). MIMO is one of several forms of smart antenna technology. Other forms are MISO (multiple input, single output) and SIMO (single input, multiple output).

In addition, compared with single-antenna systems, MIMO antennas can improve link reliability and reduce attenuation. Because multiple data streams are transmitted at the same time, MIMO antennas can also increase wireless capacity.

Three transmission methods of MIMO:

  1. Space diversity:

Space diversity is divided into receive diversity and transmit diversity. The advantages of using diversity are: easy to obtain a relatively stable signal, obtain a diversity processing gain and improve the signal-to-noise ratio.

Multi Input Multi Output Antenna

Multi Input Multi Output Antenna

Receiving diversity means that multiple antennas receive multiple independent signal copies that carry the same information from multiple channels. Since the signals cannot be in deep sinking conditions at the same time, at any given moment, the receiver can at least guarantee the reception A copy of the signal that is strong enough to improve the signal-to-noise ratio of the received signal. Transmit diversity is the use of multiple transmitting antennas at the transmitting end to transmit the same information, and a higher signal-to-noise ratio at the receiving end than a single antenna.

  1. Spatial reuse:

Spatial multiplexing realizes the high data rate and high spectrum utilization of the MlMO system by transmitting independent signals on different antennas at the same time. The transmitted high-speed data stream is divided into several parallel low-speed data streams, which are simultaneously transmitted from multiple antennas in the same frequency band. Due to multipath propagation, each transmitting antenna generates a different spatial signature for the receiver. The receiver uses these different signatures to separate independent data streams, and finally restores to the original data stream. The data transmission rate can be doubled.

Multi Input Multi Output Antenna

Multi Input Multi Output Antenna

  1. Space division multiple access

Space division multiple access uses the weak correlation of natural channels brought about by the spatial location of multiple users to transmit data to users in different locations respectively to increase the number of connections and capacity of the system. This method of use is also called multi-user MIMO (MU-MIMO). ). In fact, space division multiplexing and space division multiple access are different ways of utilizing the spatial freedom of the MIMO system.

2.4 GHz WIFI Omnidirectional Antenna With Magnetic Base

2.4 GHz WIFI Omnidirectional Antenna With Magnetic Base

Advantages of MIMO

When the signal sent by the radio is reflected, multiple signals are generated. Each signal is a spatial stream. A system using single input single output (SISO) can only send or receive one spatial stream at a time. MIMO allows multiple antennas to transmit and receive multiple spatial streams at the same time, and can distribute signals to or from different spatial directions. The application of MIMO technology makes space a resource that can be used to improve performance and can increase the coverage of wireless systems.

  1. Increase the capacity of the channel

Between the MIMO access point and the MIMO client, multiple spatial streams can be sent and received at the same time. The channel capacity can increase linearly with the increase in the number of antennas. Therefore, the MIMO channel can be used to double the wireless channel capacity. Without increasing the bandwidth and antenna transmission power, the spectrum utilization rate can be doubled.

  1. Improve channel reliability

Using the spatial multiplexing gain and spatial diversity gain provided by the MIMO channel, multiple antennas can be used to suppress channel fading. The application of the multi-antenna system enables parallel data streams to be transmitted at the same time, which can significantly overcome the fading of the channel and reduce the bit error rate.

The Principle of 2.4GHz/5.8GHz WIFI Antenna

If you find that your newly purchased 2.4GHz or 5.8GHz device does not provide the wireless coverage that you expected, it does not necessarily mean that there is a problem with the device, or that you have placed the device in the wrong location. More than 90% of the reason is that you did not configure the device.

Connect a suitable antenna; even if your WiFi client can access the Internet through your home wireless router, have you checked the actual wireless signal strength, if the signal-to-noise ratio (SNR) is too low, the wireless transmission speed cannot reach 54Mbps or more High speed, of course, wireless interference will also affect the transmission speed, but even the basic wireless signal is not good, so don’t expect high-speed Internet access.

WIFI Antenna

WIFI Antenna

So which type of antenna should we choose?
This cannot be explained clearly in a few words. Choosing a suitable antenna is actually a science. We must start with understanding the basic knowledge of the antenna. The following article will introduce the principle of the antenna and some antenna parameters. I believe it can help you select and install the appropriate antenna, thereby enhancing the effective coverage and performance of the wireless system.

The antenna is a passive body, that is, it does not need to provide power or other energy. It is also not a power amplifier and will not amplify the input wireless signal. On the contrary, due to the signal attenuation caused by the feeder and the connector, the wireless energy emitted will be greater than that of the input The energy of the antenna contact is low.

In fact, the antenna only plays the role of a directional amplifier, so that the transmitting and receiving energy is concentrated in a specific area of ​​the space. The only purpose of the antenna is to change the energy distribution area to the place where it is needed. In some places without wireless equipment, or over-distributing energy to a certain area, it is wasteful. According to the law of invariance of energy, increasing the energy distributed in one direction means reducing the energy in other areas.

The Development Of RF Coaxial Connectors

 

The radio frequency coaxial connector (hereinafter referred to as the RF connector) is usually regarded as a component installed on the cable or installed on the instrument as a component for electrical connection or separation of the transmission line. It belongs to mechatronics products. Simply speaking, it mainly serves as a bridge.

Compared with other electronic components, the development history of RF connectors is relatively short. The UHF connector that appeared in 1930 was the earliest RF connector. During the Second World War, due to the urgent needs of the war, with the development of radar, radio and microwave communications, medium series such as N, C, BNC, TNC, etc. were produced.

After 1958, small products such as SMA, SMB, and SMC appeared. In 1964, the US military standard MIL-C-39012 “General Specification for Radio Frequency Coaxial Connectors” was formulated. Since then, RF connectors have begun to develop in the direction of standardization, serialization and generalization.

In more than sixty years, through the joint efforts of experts from various countries, the RF connector has formed an independent and complete professional system and has become an important part of the connector family. It is an indispensable key component of the coaxial transmission system.

The research and development technology of RF connectors in the United States, Britain, France and other countries are in a leading position. Its design, production, testing and use technologies have been completed and tended to be perfect. Not only has it formed a complete standard system, but also raw materials, auxiliary materials, testing systems, Assembly tools have also been standardized, and specialized scale production has been carried out.

The Main Features of BNC Connector

1. BNC Characteristic impedance
The characteristic impedance of BNC radio frequency connectors is 50Ω and 75Ω. Many series of connectors have both 50Ω and 75Ω specifications. Generally speaking, 50Ω connectors are mostly used for high-frequency and high-performance products; 75Ω connectors are mostly used for products with lower frequencies, and the frequency is mostly below 4GHz, especially for consumer electronic video. Users should choose a connector that matches their impedance according to their own products. If the user uses a 75Ω RG 59 Cable, he should choose a 75Ω connector.

BNC Connector for RG174 Cable Plug Crimp Type

BNC Connector for RG174 Cable Plug Crimp Type

2. BNC Frequency
Each type of radio frequency connector has a frequency range, and the user should understand the working frequency of his product to choose the connector. Choosing a connector lower than the required operating frequency will affect the electrical performance of the whole machine; or choosing expensive, high-precision and high-frequency connectors will cause waste. It should be noted that the frequency of use of connectors designed by different companies is quite different, and the frequency of use of inferior products is far from reaching the industry standard. When selecting the connector, the user should confirm the electrical performance description of the product.

BNC Connector for Coaxial Cable for RG178 180 Degree Male to N Type Female 4 Hole Square Flange Female

3. BNC VSWR
VSWR is one of the most important performance indicators of RF connectors. It is a measure of the amount of signal returned from the connector. It is a vector unit including amplitude and phase components. The VSWR of the same type of connector is different at different frequency of use. Generally speaking, the higher the frequency of use, the higher the VSWR. If the user wants to know the VWSR of the connector at a certain frequency, he can ask the manufacturer.

The Difference Between Omnidirectional and Directional Antenna

An omnidirectional antenna, that is, it shows uniform radiation in 360° on the horizontal pattern, which is commonly referred to as non-directional, and shows a beam with a certain width on the vertical pattern.

In general, the smaller the lobe width, The greater the gain. The omnidirectional antenna is generally used in the mobile communication system with the station type of the suburban district system, and the coverage is large.

Directional antennas show a certain angular range of radiation on the horizontal pattern, which is usually called directional, and show a beam with a certain width on the vertical pattern. Like omnidirectional antennas, the smaller the lobe width , The greater the gain.

Omnidirectional and Directional Antenna

Omnidirectional and Directional Antenna

Directional antennas are generally used in urban cell-based stations in mobile communication systems, with small coverage, high user density, and high frequency utilization. Different types of base stations can be established according to the requirements of the networking, and different types of base stations can choose different types of antennas according to their needs. The selection is based on the above technical parameters.

For example, an omnidirectional station uses an omnidirectional antenna with basically the same gain in each horizontal direction, while a directional station uses a directional antenna with a significant change in the horizontal gain.

Omnidirectional antenna

Omnidirectional antenna

Generally, an antenna with a horizontal beam width B of 65° is selected in the urban area, and an antenna with a horizontal beam width B of 65°, 90° or 120° can be selected in the suburbs (depending on the station configuration and local geographic environment), and in the countryside It is the most economical to choose an omnidirectional antenna that can achieve large-scale coverage.

Specifically, you have to say which one is good, and this one is not easy to determine, depending on your use case.

Is an internal antenna better, or an external antenna?

Is it faster with 2 antennas or 4 antennas? I believe there must be many friends who are swaying around because of the “antenna” problem when choosing a router, and they can’t make up their minds. Let’s take Huawei Router A1 as an example, let’s talk about those things between the chat line and the router!

 

Which is faster, internal antenna or external antenna?

To answer this question, you might as well take a look at the status quo and differences between external antennas and internal antennas: external antennas appeared earlier than internal antennas. Early wireless router antennas were basically external; in recent years, internal antennas It has become popular, and all mainstream manufacturers have introduced routers with built-in antennas. Due to the built-in antenna, the appearance of the router is more fashionable and concise, and it is more in line with the aesthetics of modern people.

 

The angle of the external antenna can be adjusted, and the different placement of the antenna has a greater impact on the performance and network speed of the router. If the angle is not placed properly, it will affect the user’s Internet experience; and the built-in antenna is designed to be optimized by default. No need for user adjustment.

 

External antennas are easier to implement. If you encounter complex scenarios and environments, there are more solutions; built-in antennas must take into account the optimal space and antenna performance, which is relatively difficult to implement and requires manufacturers to have higher capabilities.

 

In fact, the internal and external antennas are just a solution to the router antenna design. Under current technical conditions, the router will not simply differ due to the internal or external antennas and the signal. Therefore, whether the external antenna or the internal antenna should not be the primary consideration when choosing a router.

 

What is the relationship between the wireless protocol and the number of antennas?

When choosing a router, users should pay more attention to the wireless protocol and the number of antennas, because they directly determine the Wi-Fi transmission rate.

 

Through official promotional materials, you can basically calculate the Wi-Fi rate of Huawei Router A1.

11ac 2*2 in the data indicates that it supports 802.11ac and 2 antennas, so the Wi-Fi rate is 433.3*2=866.6. 11n 2*2 indicates that it supports 802.11n and 2 antennas, so the Wi-Fi rate is 150*2 =300. The total of the two is 1167.6 (Gigabit), rounded to about 1200Mbps. The “Gigabit WiFi”, “Gigabit wireless router”, and “11AC technology” promoted by Huawei refer to this.

 

If you master the relationship between the wireless protocol and the number of antennas, you can easily avoid the various “pits” of the merchants when choosing a router in the future. For example, if a router claims to support Gigabit, it must support 11ac. If it does not support 11ac, it is definitely false propaganda! Another example is the number of router antennas (assuming 4), but only the highest rate of 300Mbps, which means that it actually only needs 2 11n antennas (2*150=300), and the extra two antennas are very likely It’s just a display, used to bluff people and increase their worth!

 

Should the router choose a product with a relatively high price and configuration?

Whether it is necessary to buy a higher-end wireless router depends on the cost performance of the product and the actual needs of users. The main consideration here is the home broadband and the size of the apartment. At present, the home broadband in most areas in China is 100M and below, and you can choose a dual-band route of 1200M. If the home broadband is greater than 100M, you need to choose dual Gigabit routers, such as Huawei Router A1 Enjoy Edition, can give full play to every megabit speed of ultra-100M fiber. Of course, if it is a large apartment with an area of ​​more than 120 square meters, multiple routers need to be used for intelligent networking to achieve seamless Wi-Fi coverage throughout the house.

 

Knowing yourself and the enemy can survive all battles. I believe that after understanding the relationship between routers and antennas, friends will be more calm and wise, less entangled and hesitate when buying routers in the future!

Why is the walkie-talkie antenna not made the same as the mobile phone

It has been almost a hundred years since the birth of the walkie-talkie, half a century before the invention of the mobile phone. But in the last century, mobile phones have evolved from the former “big brother” to today’s smart phones, and the walkie-talkie is still the same stupid, black and thick old one, and the antenna is still external. So is the external antenna of the walkie-talkie due to technical bottlenecks or deliberately?

 

The walkie-talkie uses an external antenna

First of all, walkie-talkie is a kind of radio communication equipment, and the radio that this equipment relies on has a very important indicator called “working frequency”. The working frequency of domestic mobile phones has national standards, and mobile phones generally operate between 900MHz and 1800MHz. Communicate on two frequencies, and the state stipulates that the working frequency of public walkie-talkies (ie, civilian walkie-talkies) is between 409 and 410 MHz.

 

Civil walkie-talkies have operating frequency restrictions

In order to transmit the radio signal as much energy as possible, the antenna needs to be designed to half the wavelength. The wavelength is equal to the speed of light divided by the frequency. The higher the frequency, the longer the wavelength. In other words, the wavelength of a mobile phone is more than half smaller than that of a walkie-talkie. However, when designing an antenna, it is impossible to design the antenna to be as long as the wavelength, but the longer the better.

 

Of course, mobile phone design cannot blindly pursue signal priority. After all, the current mobile phone is a necessity, and there is only one hand. The iPhone 4 started to make the appearance of the mobile phone beautiful, so many mobile phone manufacturers will put the mobile phone antenna into the body. The interior or the outer shell is integrated, which can please consumers more. After all, people are visual animals, and good-looking things can naturally sell better.

 

The stainless steel frame of the iPhone 4 is the phone antenna

In the early days of Big Brother’s era, the antenna was externally mounted. On the one hand, the priority of the mobile phone design was not as high as it is now. On the other hand, the mobile phone signal coverage at that time was not as good as it is now. The wireless signal used by the mobile cellular network works The frequency is not as high as it is now, and the signal enhancement that a larger antenna can bring is obvious, so the mobile phone antenna in the big brother era was external, or even retractable.

 

Early Mobile Phone with external antenna

The antenna design requirements of the walkie-talkie are similar to the design requirements of the early Mobile Phone. Since the use scene of the walkie-talkie does not have high requirements for the appearance of the walkie-talkie, the priority of the appearance design is lower than the priority of the antenna design. Moreover, the operating frequency of the walkie-talkie is much lower than that of the mobile phone, and a larger and longer antenna is needed to send the signal better.