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Improve Bluetooth signal: Methods for skillful. Planar Antenna Bluetooth Systems in Cell Phones Connecting External Antenna to Bluetooth Module

Now quite often release smartphones, phones or communicators with built-in wi-Fi adapter. And the radius of Wi-Fi is about a hundred meters, but the phones that are equipped with Bluetooth transmit and receive files only for a distance of no more than ten meters. If you have a USB blutooth for a computer, as well as a phone with Bluetooth, but you would like to gain an increase in reception range. All this is quite possible, but you need to improve usb-bluetooth.

Well, start. We disassemble the Bluetooth adapter for the computer, then you need to debug the Bluetooth housing and very carefully inspect the adapter fee.

In all models of adapters at the end of the board there are copper contact, similar to a spiral, in the photo is number 1. This helix is \u200b\u200ban antenna Bluetooth, an additional homemade antenna will be soldered to it.

We need a wire single-core with a diameter of 0.4 to 0.8 mm. The wire is covered with a varnish insulation, and it is not necessary to get rid of it completely. We will spin the wire as shown in the photo, then we will carry out the processing of the tip of the copper wire using rosin, then tin. The same procedure should be done with a copper spiral in Bluetooth, do not overheat the adapter fee, make all the work very carefully.

Then, you need to make a hole in the case itself for the Bluetooth adapter, at the exit place homemade antenna. Now very carefully close the board in the housing. Here is the upgraded Bluetooth, which gives an increase in the range of receiving times in 4.

To further increase the range of reception, you can take a multi-core rather long wire, which will be covered with insulation, it is necessary to clean the tip and climb it to the antenna, the second tip can be attached to a small carnation driven into the wall.

Several firms, such as Hitachi Metals, Murata, YoCowo, Antek Wireless, Centurion, and others, have already produced a wide range of antennas that are used in cellular telephony and are specifically designed for Bluetooth systems using ceramic materials with good high-frequency properties.

Hitachi Metals released antennas of the E-Type Electrode Configuration (Fig. 28), well-suitable for Bluetooth applications. The place required for the new antenna is very small (15x3x2 mm), it is not sensitive to the location of the peripheral parts, can be made in the form of a highly efficient crystal antenna for Bluetooth, easy to use.

Fig. 28.

Antek Wireless Inc. Developed a new 2,4-GHz antenna of an original design, which provides effectiveness exceeding actually any technical requirements of the project, miniature, and can be installed almost any device. Antenna is applicable to various application of the type of wireless video signal, audio equipment, headphones, modems, mobile computers, portable phones and other portable pocket devices that use Bluetooth protocols, IEEE 802.11 and HOMERF.

CENTURION INTERNATIONAL has developed an internal PIFA antenna or a kind of flat antenna for use in portable computers using Bluetooth technology. New antenna gives computer firms to manufacturers to develop portable deviceswhich are easily associated with portable phones and messaging systems are connected to the Internet at high data rates.

Murata Manufacturing Co. Beginning the production and sale of built-in dielectric antennas for laptops using Bluetooth technology (Fig. 29). Dimensions of the module new Series G2 - 15x5.8x7.0 mm.

Fig. 29.

MIYAZAKI MATSUSHITA Electric Industrial Co. Ltd. Releases an overcompact antenna for Bluetooth devices (30). The antenna is performed on a ceramic basis and has dimensions of 5x1.2x1.2 mm. This is the smallest antenna in the Bluetooth industry. The characteristics of the antenna are as follows: The operating frequency is 2.4 GHz, the gain coefficient -2 DBI, the coefficient of standing wave for voltage (KSVN) 2.0.

TDK Corp. Releases two half-wave small-size antennas (7 by 7 mm) for use in products based on Bluetooth technology. The antenna canpb0715 has an amplification coefficient -5 DBI, and the antenna canpb0716 - 3 DBI. Most other small antennas are quarter-wave. Their use is possible only in larger mobile devices, such as laptops, where grounding is performed on the device body.

Previously, the antennas had two main configurations: reverse asymmetric F-type antenna and a flat antenna. The inverted F-antenna has one side open, and the other is grounded, which is done to reduce the size, but the open side is subordinate to the influence of the grounding electrode.

Fig. thirty

Therefore, a large area is required to implement antenna properties in a given space, and caution is necessary when designing the location of the peripheral components. In addition, a flat antenna is highly sensitive (high gain) and has strong directed properties, making it unsuitable for Bluetooth applications, where omnidarity is needed.

The type of antenna developed by Hitachi Metals has unique advantages of the F-type reverse antenna, but includes grounding electrodes on both sides and is added central, cone-shaped electrode. In other words, the new E-Type Electrode configuration, invented in Hitachi Metals, can be even more miniaturized, and does not significantly affect the nearby grounding electrodes. The smaller the antenna, the smaller the case affects its parameters.

An analysis of all the antenna designs for the Bluetooth system above, allows you to select the main antenna parameters included in the antenna specification, on the basis of which you can choose the method of designing a cell phone with such an antenna.

Technical requirements for the Bluetooth system antenna:

Frequency operating strip: 2400 ... 2500 MHz;

Average amplification: -3 DBI;

Input resistance: 50 ohms;

VSWR: 3 or less.

In the process of designing an antenna system, it is necessary:

Optimize the earth surface (sometimes called counterweight), that is, to find the optimal filling of the inner surface of the body of the phone with conductive areas. Currently, this is often implemented by the crucible individual parts of the conductive paint.

The purpose of the design of the antenna is to obtain the required orientation diagram (DN) and good matching in the working strip of frequencies.

Planar Bluetooth Antenna Systems in cell phones

V. Kalinichev, A. Kurushin, V. Sublayer

Planar Bluetooth Antenna Systems in Cell Phones

The use of planar microstrip antennas in the Bluetooth wireless LAN system is considered. Designed structures and methods for analyzing a planar ceramic antenna, taking into account losses in ceramics. For numerical antenna analysis, the HFSS program has been used in the case. Calculations are made for a specific handset: the current distribution over the surface of the metal, topped with a dielectric, phone body, orientation charts for various cell phone orientation. An overview of the serial Bluetooth antennas is given, as well as recommendations for the installation of these antennas in the housing.

Introduction

An increase in the rate of exchange of information contributed to the development of wireless communication systems on the "home" level. Personal computers and laptops, cell phones, CD- and MP3 players, digital photo and video cameras and a mass of other digital devices (Fig. 1), often connected to each other and to stationary computers, created the problem of their connection.

Figure 1. Local connection system using Bluetooth wireless technology

The cable became inconvenient - it is necessary to connect often, the sizes of the cable itself with the connectors are barely no more than the connected device itself and so on. Against this background, the relevance of WLAN wireless local technology (Wireless Local Area Networking) has sharply increased, providing a contactless connection of the device to the drive disk.

As a result, the system was proposed and began to quickly develop. wireless communication Bluetooth (Fig. 1). In the spectrum of radio frequencies, it is assigned 79 channels in the 37 MHz band (about 2 MHz each) in the range of 2.4465-2,4835 GHz.

Essence bluetooth standard In equipping electronic devices Releases operating at a frequency of 2.45 GHz having a radius of up to 10 m and the rate of information transfer to 1 Mbps. The possibilities of applying these devices are truly limitless. Wireless headphones, mice, keyboard, connection mobile phones And laptops, the exchange of information between pocket computers is not to list.

The Bluetooth system operates in a resolved 2,45 GHz strip (ISM - Industry, Science, Medicine, Science, Medicine), which allows you to freely use Bluetooth devices throughout the world. The technology uses a jump-like frequency restructuring (1600 jumps / s) with spectrum expansion. During operation, the transmitter jumps from one operating frequency to another by the pseudo-random algorithm. To separate the receiving and transmit channels, a temporary separation is used (Fig. 2). Synchronous and asynchronous data transmission is supported and integration with TCP / IP is provided. Temporary intervals are synchronized to transfer packets, each of which is transmitted at its radio signal frequency.

Figure 2. Alternate data exchange between the device A and the device B

The power consumption of Bluetooth devices must be within 0.1 watts. Each device has a unique 48-bit network addressCompatible Standard Format local networks IEEE 802.

The basic principle of building Bluetooth systems is the use of the spectrum expansion method with a jump-like frequency change (FHSS - Frequency Hop Spread Spectrum). All selected for Bluetooth radio frequency range of 2.402 ... 2,480 GHz is divided into N frequency channels. The band of each channel is 1 MHz, the separation of the channels is 140 ... 175 kHz. For coding packet information uses frequency manipulation.

For the US and Europe n \u003d 79. The exceptions are Spain and France, where 23 frequency channels are used for Bluetooth. Channel change is made according to the pseudo-random law with a frequency of 1600 Hz. Permanent frequency alternation allows Bluetooth radio interface to broadcast information over the ISM range and avoid the impact of interference from devices operating in the same range. If this channel is incredible, the system will switch to another, and so will occur until the channel is found free from interference.

Fast start Bluetooth systems have a lot of facilitated the simplicity of the structure. It includes a transceiver radio module, a communication controller (it is the same processor) and managing device, Actually implementing Bluetooth protocols upper levelsas well as an interface with a terminal device. Moreover, if the transceiver and the communication controller are specialized chips (integral or hybrid), the communication management devices are implemented on standard microcontrollers, signal processors, or its functions support central processors of powerful terminal devices (for example, laptops).

Besides, in bluetooth devices use integrated circuits used in other applications, since the microwave range of 2 GHz is mastered quite well, and laid in Bluetooth technical Solutions themselves do not contain special novelty. In fact, the modulation scheme is widespread, the spectrum expansion technology by the method of frequency jumps is well worked out, the power is small.

The key to the success of Bluetooth technology is a radio receiver. Low price and low power were primary considerations both when implementing the technical requirements of the interface (short aerial radioline) and when designing the receptionist. Bluetooth technology allows you to create a single-chip receptionist, combining the RF scheme and the digital streaming scheme on one silicon crystal.

Bluetooth transceiver

The Bluetooth receiver can be divided into three functional blocks (Fig. 3). The radio block contains converters up and down by RF, an inverter with a strip of modulating frequencies, a channel filter, modulator / demodulator and frequency synthesizer.

Figure 3. Basic Bluetooth receiver elements

The radio roll performs the transformation of the FM signal at a frequency of 2.45 GHz in a bitstream and vice versa. Antenna is a very important element of the system. The antenna must be omnidirectional and gain 0 DBI, the user's presence should not affect the signal distribution. Due to the small wavelength at the frequency of 2.45 GHz, the antenna size is limited to several see. Currently, flat or PIFA antennas are most often used, but even more miniature E-type designs on a ceramic substrate are proposed. The antenna is complemented by a strip filter that elames the frequency of 2.45 GHz from the ISM band.

To implement simple and stable receivers and non-coherent detection, Bluetooth uses binary frequency manipulation (FM, FSK), with a rolling jump with a Gaussian pulse, with a speed of 1 Mbps. The area of \u200b\u200bsuch a signal Bt \u003d 0.5, where b strip, T is the pulse duration, under the modulation index from 0.28 to 0.35 and the pulse duration of 1 μs. The World Cup eliminates the need for ARU, which is difficult to work when switching frequencies, and when the data come in uneven time intervals. The input part of the RF receiver consists of a converter with a decrease in the frequency, channel band filter and frequency detector.

The channel filter highlights a band of 1 MHz, and quite high selectivity requirements are presented to it. Since the ISM band must be divided into other systems in this lane (among which other Bluetooth systems can be, measures should be taken to prevent instrument interaction. Usually the Bluetooth receiver is built with the frequency conversion down (that is, when the mirror canal falls into the PC band). For the junction near the Bluetooth operating systems, the blocking coefficients on the mirror channel must be 20, 30 and 40 dB for the first, second and third adjacent channels.

Due to the features of the Bluetooth system, the technical requirements for the intermodulation are tough than to the sensitivity of the receiver.

To overlap the distance of 10 m with an output power of 0 dBm, the sensitivity of the receiver P min \u003d -70 dBm is sufficient. Taking into account the noise level at the input of the receiver -114 dBm (in the noise band 1 MHz) and the requirements at the output of the receiving path K M \u003d 21 dB, to ensure the maximum information transfer error rate of BER \u003d 0.1%, we obtain that the noise coefficient is 13 dB . This value is calculated from the formula for sensitivity.

P Min \u003d -174 dBm + NF + 10LGB + A + K M, (1)

where -174 dBm is the power of thermal (KTB) noise in the 1 Hz strip in normal temperature; NF - noise coefficient, dB; B - frequency band before the demodulator, 1 MHz; a - trigger threshold, a \u003d 3 dB; K M - coefficient depending on the type of modulation.

Compared to the noise coefficient achieved for today, which is significantly lower than 13 dB, this value seems to be a rather poor meaning. However, this low requirement allows you to use cheap components with losses and protects against interfering signals (tipping in the substrate and the power wiring).

Calculation of the dynamic range of Bluetooth receiver

The upper limit of the dynamic range can be estimated by the level of the product of the intermodulation distortion of the 3rd order, if we assume that 2 signals with frequencies of two adjacent channels act on the input.

Two signals with frequencies F 0 + D F and F 0 + 2D F produce a product of the intermodulation distortion of the third order P IM3 in the considered radio channel with the frequency F 0. The power level of the product P IM3 depends on the input signal of the interfering power P in and the nonlinear parameter of the entire receiver - the intersection points of the third order IP 3 - and equal:

P im3 \u003d 3p in - 2IP 3 [dB]. (2)

Free from distortion dynamic range It is determined from the condition that distortions of linear and nonlinear origin are equally affected by distortion in the demodulator and the detection of its own signal is equally worsen. It means that BER does not exceed the same value of 0.1%, which was set when determining the sensitivity, it is necessary that the power of the received signal was 3 dB above the noise level (which corresponds to the sensitivity of the PM receiver). Therefore, IP3 \u003d -16 dBm was obtained in expression (2), provided that the PIM3 intermodulation product is equal to the sensitivity of the receiver, two interfering signals have a power of 0 dBm, and the interference is present at a distance of 1 m.

Combining the value of IP3 \u003d -16 dBm with the sensitivity of the receiver P min \u003d -70 dBm, from (1) and (2) we get that free from distortion dynamic range (SFDR) Bluetooth receiver must be equal to

SFDR \u003d 2/3 (IP 3 - (p min + 3 dB)) \u003d 50 dB. (3)

The transmitter block is also quite simple. Binary GFSK modulation was obtained by direct modulation of the CM-Gometerodine. Additional phase transformations with increasing frequency are why not needed. The modulating signal is filtered by a Gaussian filter so as to maintain the width of the spectrum of 1 MHz, as required for FM systems operating in the ISM frequency at 2.45 GHz. Modulation with Gaussian envelope does not impose high requirements for the linearity of the output cascade of the transmitter, the cost-effective amplifiers of class C.

Bluetooth transmitter power is about 0 dBm (it is allowed to use the maximum power up to 20 dBm). For power levels exceeding 0 dBm, power control over a closed contour is applied.

Calculation of the range of the cell phone in the Bluetooth system

It is known that the power of the radio signal at the point of reception P n is equal to:

where P is power radiated by the transmitter; G M is the maximum gain of the transmitting antenna; A ech.m - the maximum effective area of \u200b\u200bthe receiving antenna (proportional to the geometric area of \u200b\u200bthe antenna); F (,) - the function of the selectivity diagram of the transmitting antenna; F "(", ") - the function of the selection of the reception antenna.

From this formula, you can get the maximum range of radio communications, provided that the antennas are directed to each other,

where p n.min is the sensitivity of the receiver, in our case p n.min \u003d 10-10 W (-70 dBm).

Substituting in formula (4) the power of the transmitter P \u003d 10-3 W, G M \u003d 0.5, A Eff.m \u003d 25 · 10 -6 (5 to 5 mm), we obtain R m \u003d 3 m.

This value approximately complies with the requirements of the Bluetooth system, and can serve as a starting point for calculating the antenna geometry, since the remaining characteristics are determined by the standard for the selection chip.

Bluetooth Antennas (Overview of manufacturers and solutions)

Hitachi Metals released antennas of type "E-Type Electrode Configuration" (Fig. 4), well-suitable for Bluetooth applications. The place required for the new antenna is very small (15x3x2 mm), it is not sensitive to the location of the peripheral parts, can be made in the form of a highly efficient crystal antenna for Bluetooth, easy to use.

Figure 4. View of the Hitachi Metals antenna for Bluetooth

Antek Wireless Inc. Developed a new 2,4-GHz antenna of an original design, which provides effectiveness exceeding actually any technical requirements of the project, miniature, and can be installed almost any device. The antenna is applicable to various application of the type of wireless video signal, audio equipment, headphones, modems, mobile computers, portable phones and other portable pocket devices using Bluetooth protocols, IEEE 802.11 and Homerf.

CENTURION INTERNATIONAL has developed an internal PIFA antenna or a kind of flat antenna for use in portable computers using Bluetooth technology. The new antenna enables computer firms to develop portable devices that are easily associated with portable phones and messaging systems are connected to the Internet at high data transmission rates.

Murata Manufacturing Co. The production and sale of built-in dielectric antennas for laptops using Bluetooth technology (Fig. 5). The dimensions of the module of the new G2 series - 15x5.8x7.0 mm.

Figure 5. Chip Antenna ANCG22G41 MURATA

MIYAZAKI MATSUSHITA Electric Industrial Co. Ltd. Releases a super-compact antenna for Bluetooth devices. The antenna is performed on a ceramic basis and has dimensions of 5x1.2x1.2 mm. This is the smallest antenna in the Bluetooth industry. The characteristics of the antenna are as follows: The operating frequency is 2.4 GHz, the gain coefficient -2 DBI, the coefficient of standing wave for voltage (KSVN) 2.0.

Figure 6. Ceramic antenna in a cell phone housing (photo)

Figure 7. 3D-View Bluetooth Antenna in Metallized Cell Phone Case (Drawing in HFSS)

E-type antenna configuration

Previously, the antennas had two main configurations: reverse asymmetric F-type antenna and a flat antenna.

The inverted F-antenna has one side open, and the other is grounded, which is done to reduce the size, but the open side is subordinate to the influence of the grounding electrode. Therefore, a large area is required to implement antenna properties in a given space, and caution is necessary when designing the location of the peripheral components.

In addition, the flat antenna is highly sensitive (high gain) and has strong directed properties, making it inappropriate for Bluetooth applications where omnidarity is necessary.

Technical requirements for the Bluetooth system antenna:

frequency operating strip: 2400 ... 2500 MHz;
average amplification: -3 DBI;
input resistance: 50 ohms;
VSWR: 3 or less.

In the process of designing an antenna system, it is necessary:

calculate the matching structure between the filter entrance and the microstrip antenna power point;
optimize the earth surface (sometimes called counterweight), that is, to find the optimal filling of the inner surface of the body of the phone with conductive areas. Currently, this is often implemented by the crucible individual parts of the conductive paint.

The purpose of the design of the antenna is to obtain the required orientation diagram (DN) and good matching in the working strip of frequencies.

Analysis of the generalized structure of the planar antenna

From the review of the existing antennas for the Bluetooth system it is clear that they have metal forms of complex configuration, sprayed on one or more sides of the three-dimensional substrate, most often ceramic with large permeability (Fig. 8). Therefore, we can say that each of these forms is a resonator. It is known that the dimensions of the antenna are associated with the working frequency. If we assume that the antenna resonates along a longer side, then the length of the antenna can be estimated according to the next simple formula:

where f r is a given resonant frequency; - relative dielectric permeability of the substrate material. This formula does not take into account the effect of the width of the antenna substrate and the substrate thickness into the resonant frequency, but this effect is usually insignificant. Formula (1) reflects the physical nature of the printed antenna (Fig. 9) as a half-wave resonator, which is formed in the space between the upper conductor and the excavation board of the antenna. For example, at a frequency f r \u003d 2.5 GHz and \u003d 34 (ceramics) from (1) we have a ~ \u003d 10.3 mm.

Figure 8. Geometry of Bluetooth antenna YCE-5207 in the AutoCAD system

Figure 9. Bluetooth antenna (top view) designed in AutoCAD

The antenna length can be reduced at least twice (when working at the same frequency), if one end is grounded. In this case, it turns out the so-called inverted F-antenna (PIFA), which represents the quarter-wave resonator, one end is grounded, and the other is open (idle). PIFA (Fig. 3) is excited by a coaxial line at a point where the antenna's input resistance is close to 50 ohms. Thus, the PIFA length can be approximately appreciated as

For an antenna configured to the same frequency f R \u003d 2.5 GHz and \u003d 34, we obtain A ~ \u003d 5.1 mm, which is already occupied by much less space than in the previous case. The actual antenna size may even be less, due to the effect of the regional near field focused at the open end of the resonator.

The size of the E-antenna, since it is cooled from both sides, may be roughly estimated as

Since the antennas for the Bluetooth system are located in the semi-cranked screen of complex shape, the characteristics of the antenna system can differ significantly on the characteristics calculated on theoretical formulas. In this case, the antenna parameters (the size of the conductors and the distance between them in height) can be optimized with one of software packagessimulating electromagnetic structures (Fig. 10).

Figure 10. The near field in the cell phone (in the HFSS field)

It should be noted that the advantage of the small size of the PIFA antenna is achieved by reducing its radiative ability (only one edge radiates), besides, usually PIFA antennas are narrowband.

Numerical design methods of planar antennas

Antennas are the main components of all radio communications systems and use free space as a transfer medium. They are used to associate the transmitter or receiver in free space using the interface.

Antennas have a number of important parameters, the greatest interest of which have increased, radiation pattern diagram, range width and polarization.

Modern design of cellular antennas (Fig. 11) is based on modeling electromagnetic phenomena on a computer, using the results obtained on the basis of sketch calculations and heuristic considerations as initial data.

Figure 11. View of Bluetooth Antenna in Cell Phone Case

When creating a model, it is necessary to remember that the geometry must comply with the real position of the antenna during operation, that is, such that the body is in a vertical position (or at a low angle). In this case, the flat antenna is in the position "on the edge".

Features of miniature ceramic antennas

The ceramic antenna is made on a substrate with high dielectric constant. Material with high permeability has also large losses.

Therefore, the calculation of such antennas must be carried out using programs that fundamentally take into account losses in ceramics. Such a program is the HFSS program.

In order to successfully install a flat antenna in the design of a cell phone tube, you need to conduct settlement studies that would show the dependence of the characteristics of an antenna system from certain elements of the phone designs.

We note the following features of microstrip antennas:

microforn antennas are more narrow-band, compared to spirals;
microstrip antennas are easily implemented by circular polarization, compared with predominantly vertical polarization in spiral antennas;
microforn antennas have a more uneven radiation diagram in azimuthal plane than spiral and vibratory, due to its asymmetry relative to the vertical axis.

As already noted, the ceramic antenna is a 3D structure, on the surface of each side of which metal conductors of a certain form are applied. This design may have one or more excitation points. In these points on the antenna, an excitation voltage is supplied, which leads in the structure of radiation currents. Excitation points can be associated with a symmetrous transformer (baluster).

In addition to the excitation points, there may be grounding points on the printed antenna (attachment to the grounding plane). The currents entrusted in this complex design form a radiation diagram and implement other antenna characteristics necessary to establish communication with personal computer or another device.

Since, as a result of electrodynamic calculation, it is possible to determine the distribution of currents in the system, then their analysis can serve as a basis for upgrading an antenna.

In the process of designing an antenna, it is necessary, first of all, to obtain the input resistance close to 50 ohms, since in this case it will be possible to negotiate the antenna with a low-noise input amplifier and the power amplifier of the transmitting path.

For example, if the magnitude of the return loss of the antenna (parameter 20 log | s 11 |), order -20 dB, this suggests that the operating range of the antenna will work with good agreement with the surrounding space. The value of -20 dB shows that the generator power will be absorbed almost without reflection by the antenna, which in turn is loaded with free space. The antenna is a transformer between the output of the power amplifier (or the input of the low noise amplifier) \u200b\u200band the free space, wave resistance which for a flat wave in the far zone can be considered equal to 377 ohms.

The following requirement is the characteristics of the radiation that determine the ability of the antenna emit in different directions. When designing and calculating the antennas are usually interested in cross-sections of a focus diagram in two mutually perpendicular planes: azimuthal and angry. The azimuthal DN determines the ability of the antenna to emit in a horizontal plane, the angry bottom - in the vertical. And the same day are important for a cell phone, but the first determines the omnidarity, and it is more characteristic to estimate the radiation under operating conditions. The parameters of the direction of the printed antenna or its modifications should not be worse than the existing spiral-pin antennas.

Bluetooth Antenna Radiation Characteristics

The table presents the results of the antenna modeling in the housing using the exact geometric sizes of a particular design. The table shows that the parameters of the calculated design are significantly different from the measured matching parameters (Fig. 16). Therefore, analyze the reasons for these differences.

Table. Power, radiated antenna, direction, amplification and magnetyud in the absence of losses in the substrate (the tangent of dielectric permeability \u003d 0). Power The nominal generator at the entrance (port) is 1 W

F Frequency	P SAL Emitted power, calculation, W (calculated power sums through the radiation plane)	D Food, dB (calculation on HFSS)	G reinforcement, dB \u003d p	S 11 calculation on HFSS	20 Logs 11 dB
2	0,07	3,47	-7,8	0,96	-0,5
2,2	0,15	2,87	-5,4	0,92	-1
2,4	0,3	2,5	-2,7	0,83	-2
2,6	0,47	2,6	-0,6	0,73	-3
2,8	0,08	2,8	-8,3	0,96	-0,4
3	0,02	3,8	-12,3	0,99	-0,2

The largest principal difference between the estimated and real design lies in the parameters of the substrate. Thus, the calculation data shown in the table corresponds to an idealized case of the absence of losses in a ceramic substrate. In this idealized case without loss, we will find the relationship of the table parameters.

The Pizel is calculated by the HFSS program throughout the radiation boundary. All the power passed through the walls denoting the limit of the far field is summed up and gives this p.

If the substrate and conductors without loss, then all the power that has come to the antenna is emissus, that is, P is. \u003d P ANT, and this power that has come to the antenna and then emitted is determined, in turn, mismatch:

P was t \u003d P ANT \u003d P NOM (1 - | S 11 | ²), (7)

where p nom is the rated power of the generator. In the calculation on HFSS, it is given 1 W.

At a frequency of 2 GHz, in accordance with the table, from (7) have

P ANT \u003d 1 (1 - | 0.96 | ²) \u003d 0.07W,

what corresponds to the value obtained by the value in the value in the table.

Antenna strengthening by definition is equal

Substituting (7) in (8), we obtain, in a logarithmic scale,

G \u003d 10lg (1 - | s 11 | ²) + d. (nine)

For frequency of 2 GHz, we have antenna gain

G \u003d 10LG (1 - | 0.96 | ²) + 3.47 \u003d -7.8 DB.

So, we showed the connection of the antenna parameters for the case without loss in the substrate.

Refer (7) in the following form:

Analyzing the calculation of HFSS, we see that at a frequency of 2 GHz and at other frequencies, the enhancement of the antenna is bad, and, most importantly, the disorder of the antenna takes place (Fig. 12). The experiment shows however, the enhancement of the antenna is significantly higher, even without inclusion of matching chains. What is the case? It turns out that oddly enough, the presence of losses in the ceramic substrate contributes to the harmonization of the antenna and the improvement of the characteristics of a small antenna, compared with the usual antenna, the dimensions of which are commensurate with a wavelength. Indeed, increasing the loss to the value of Tg \u003d 0.1 (of course, unrealistic), by calculating the HFSS, we obtain the qualification dependences shown in Fig. 13.

Figure 12. Frequency response Bluetooth antenna with ceramic parameters \u003d 34, TG \u003d 0 (without loss). From the picture it is clear that the coordination is bad

Figure 13. Frequency response Bluetooth antenna with ceramic parameters \u003d 34, TG \u003d 0.1 (at 2 GHz frequency)

In order to investigate the effectiveness of the antenna, depending on the loss, we calculate the dependence of the characteristics of the antenna in the case from losses in ceramics. Ceramics has losses, and calculations show that if we assume that there are no losses, the antenna has bad matching, if there is a loss - the negotiation is improved.

Power P is calculated by the program is numerically as the sum of the capacities falling on all the limits of radiation. This power is less than the rated power of the generator, and is only part of it.

Since in this case we have losses, they are defined as the difference of capacity between the case without loss, formula (7), and the value of P is. Equality p was toned \u003d p AnT is no longer fair, these capacities differ in the power of losses in the substrate:

P was t \u003d P ANT - P. (eleven)

Substituting (11) in formula (8), we obtain that the enhancement of the antenna taking into account the losses in ceramics is located by the formula

which can be represented as

| S 11 | ² \u003d 1 - KTG - G / D, (13)

where k * tg \u003d p ruble / p nom, k in the general case is not equal to 1.

From (13) it can be seen that | S 11 | ² decreases with increasing losses, and it can be understood why coordination with antenna is achieved easier for the case of ceramics with losses.

Figure 14. Bluetooth Antenna System Rate Comerate Diagram

Figure 15. Azimuthal Cell Phone Directivity Chart with Bluetooth Antenna System

Calculations show that the influence of the user's body on a small antenna pattern is significantly less than on the bottom of the main cell phone antenna. The same can be said to the reverse effect of the radiated power of the Bluetooth antenna on the human body.

Experimental study of the planar antenna

Experimental antenna setting can be performed by the criterion of coordination and by the criteria of the day. In fig. 16 shows the measured frequency response of the parameter S11, applied to the Smith chart.

Figure 16. Measured on the chain analyzer. The antenna input resistance in the housing

These experimental measurements are made on the HP8632 chain meter.

An experimental measurement of the displacement frequency of the antenna system when shielding an antenna screen showed that the care of the resonant frequency when an antenna is introduced into the housing was 50 MHz.

Conclusion

The article discusses the features of modeling the microstrip antenna in the Bluetooth system intended for wireless local communication. The Bluetooth system in the cell phone is considered. The main feature of the work of the antenna system is the work of the antenna in a highly metallized building, that is, with a greater counterweight. Therefore, to calculate the currents inspected by an antenna on the surface of the case, it is necessary to apply the analysis program in 3D representation. Such a program is HFSS. In this case, the simulation of the antenna together with other elements of the case is the essential part of the entire design of the design of the antenna and tube design.

The features of the modeling process are demonstrated on the examples of the YCE-5207 Antenna PATCH, which is presented by a combination of a rectangular metal platform and a microfiber line on ceramics with a large dielectric constant of sufficiently complex forms. The results of the specific analysis are presented in the form of frequency characteristics of the reflection coefficient, currents on the housing, the near field and the day. The influence of the elements of the tube body on the radiation diagram in the far zone is shown. Considered both outer and intact options for attaching antenna.

Literature

Jennifer Bray, Charles Sturman. Bluetooth: Connect without Cables. Prentice-Hall, 2001. 495 p.
Balanis C.A. Antenna Theory: Analysis and Design, Wiley & Sons. 2nd Edition. 1997.
Fujimoto K. and James J.r. (Editors). Mobile Antenna Systems Handbook. 2nd Edition. ARTECH HOUSE. 2001. 710 p.
Kesshenikh V., Ivanov E., Kondrashov Z. Bluetooth: Principles of construction and functioning // Chip News. 2001. No. 7. P. 54-56.
Kalinichev V., Kurushin A. Microforn antennas for cell phones // Chip News. 2001. No. 7. P. 6-12.

Wireless devices are very comfortable - you do not need to worry more for the wires, but you must clearly understand that the connection "by air" has its own definite limitations on the radius. And the cheaper, for example, there will be a Bluetooth adapter that you acquire for your computer, the less you can move away from it to get a stable connection. Of course, some expensive devices do not always give good results. Today we will talk about how to strengthen the Bluetooth signal and how real it is.

general information

The article describes some methods that imply a disassembly of the adapter, replacing its parts or modifying with soldering, which may come far from everyone. If you do not understand the electronics, are not very prompt in the use of a soldering iron or your device under warranty, then please avoid similar methods.

We complement the adapter

The simplest, but not the most effective method, how to increase the Bluetooth speed, can be considered an adapter addition to the reflector, which will send a signal in a specific direction, and will not strengthen its distribution to all 360 degrees.

You can try to make such a reflector from a tin beer can, cutting off her top and making a few more slots: from top to bottom and then from her a little to the side, as if slightly separating the bottom of the banks.

The Bluetooth adapter is fastened to the center of what you have to do, and connects to a USB adapter computer.

Something like this can be built from cardboard with foil pasted on it.

Another option that can work is to cut off only the top of the banks, then make a slot for the hull closer to the bottom of the jar and insert the adapter inside the side on which the antenna is located. Further, again, fix the method convenient to you and connect through the extension.

Modifications

And now we will talk about the ways that imply a physical modification of the adapter itself. In the cheaper you are unlikely to find an external antenna, in which, in fact, there is their problem.

We open the body, if there is such an opportunity, and we are looking for a SMD antenna, which is in a fee, - you need to fall out, only very carefully, not overheating item.

Further, we solder the SMA connector into the antenna place, before that, removing all unnecessary: \u200b\u200bthe part in which the antenna is screwed down, do not touch, and on the other end you cut off the edge, we divide the screen and veins, we clean them, we samp out.

If you have doubts where exactly how to solder, it is best to contact radio amateurs forums.

Now we connect to the fact that we have come out, the antenna that can be boldly twisted from the old Wi-Fi.

If you have a more expensive device already with an external antenna, but you are still dissatisfied with the signal, then save the situation Hyper Gain antenna - buy it, cut off the adapter for connecting and separate the screen with residential.

Improve Bluetooth signal: Methods for skillful. Planar Antenna Bluetooth Systems in Cell Phones Connecting External Antenna to Bluetooth Module

Planar Bluetooth Antenna Systems in Cell Phones

general information

We complement the adapter

Modifications

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