KR970000654B1 - Antenna impedance control device of cellular phone - Google Patents

Abstract

The impedance adjusting apparatus is composed of a low noise filtering part(400) eliminating an unnecessary signal from a high frequency signal transmitted from the base station and received through antenna of a communication terminal; a first and a second impedance matching parts(403,404) coupling an impedance of the antenna of a transceiver and an input impedance of a transmit-receive terminal part of an inside of a communication terminal; a matching selection parts(401,402) being connected to both ends of the first and the second impedance matching parts, respectively, to select a suitable first or second impedances matching parts according to the result value of a power comparing part(407), transmitting the signal of the transmitting terminal to the base station through the first and the second impedance matching parts, the low noise filtering part(400) and the antenna, and transmitting radio wave of the base station to the receiving means through a reverse direction path; a circulator(405) transmitting selectively the radio wave of the transmitting terminal or the radio wave which is impedance-matched to be provided to the receiving terminal, to a power measuring part(406) or the first matching selection part(402).

Description

Impedance regulator of cell phone antenna

1 is a view for explaining the change in the antenna resistance value according to the ambient environment of a typical cellular phone,

(a) shows the state of change when there is no object around the antenna,

(b) shows the state of change when there is an object around the antenna.

FIG. 2 is an antenna transmission / reception circuit for explaining FIG. 1 in more detail. FIG.

3 is an impedance matching circuit diagram of a conventional cell phone antenna.

4 is a block diagram of an impedance control device of a cellular phone antenna of the present invention.

* Explanation of symbols for main parts of the drawings

400: low noise filter 401: first matching selector

402: second matching selector 403: first impedance matching part

404: second impedance matching unit 405: circulator

406: power measurement unit 407: power comparison unit

The present invention relates to impedance control of a cellular phone antenna, and more particularly, to optimize a call rate between a base station and a terminal by optimally adjusting the impedance of a resistance value change of a cellular phone antenna that varies according to the surrounding environment regardless of the surrounding environment. It relates to an impedance control device of a cellular phone antenna to be.

In general, in a mobile communication system, a mobile identification number (MINI) corresponding to a unique number for each mobile station, for example, the area code of the mobile station, and a serial number (SN) for identifying a mobile station to a cellular system, which is a producer A code (including a Manufacturer's Code) is assigned to communicate with other mobile stations based on this unique number.

However, such a mobile communication system, according to the protocol of the cellular radio communication terminal specified in the call processing of the Electronic Industries Association (EIA), may cause the cellular radio communication terminal to miss the call message sent by the base station under special circumstances. When the case occurs, the cellular radio communication terminal is called to fail.

Another big problem in cellular wireless communication terminals is that the transmit / receive antenna is influenced by the surrounding environment so that it is almost impossible for the user to transmit / receive in a sealed area surrounded by iron, concrete, water or land.

This is more severe when the antenna is closed or retracted in a non-call mode, not in a call (call waiting state), and the call is not started at all.

There are many kinds of antennas used in the cell phone, the most common of which is a monopole antenna, which is a variation of a dipole antenna.

The monopole antenna usually operates on a ground plane, in which the body of the phone acts as a ground plane.

The cell phone antenna has a fixed antenna resistance value determined by the length of the antenna itself, the material of the covering surrounding the antenna, and the role of the ground plane of the cellular phone itself, but the human body and surrounding buildings such as the hand of the person touching the cellular phone (terminal) It can cause a severe change under the influence of, etc. This will have a big impact on efficient radio transmission and reception.

FIG. 1 shows how the antenna resistance is changed by the surrounding environment of the cellular phone antenna. As shown in (a) of FIG. 1, when there is no object around the monopole antenna 100, the monopole antenna Impedance (ZA) measured at the inlet of (100) can be expressed as pure resistance (R) and reactance (X). The designer can optimize the impedance (ZA) value by changing the antenna size.

For example, reactance can be minimized to avoid severe resonances and to operate at broadband.

As an easy example, assume that the structure of the monopole antenna 100 is designed such that the resistance R is 50 (Ω) and the reactance (X) is 0 (Ω), as shown in (B) of FIG. When the object, that is, the metal 101 is in the direction of the monopole antenna 100, the resistance value is greatly reduced due to a shorting effect on the E-field to be coupled to the monopole antenna 100. (R) changes to 5 (Ω) and reactance (X) changes to about 0 (Ω).

A good example of this would be the case where the monopole antenna 100 is placed on a metal desk.

FIG. 2 is an antenna transmission / reception circuit diagram for describing FIG. 1 in more detail.

That is, in the case of reception, the signal source may be simply moved from the generator 200 toward the antenna.

As in the general circuit theory, the impedance of the generator 200 is compared with the value of the resistance of the antenna 201 so that the resistance R is long and the reactance X is the same with the sign changed. In order to satisfy this condition, a matching communication network circuit portion 202 is connected between the generator 200 and the antenna resistor 201.

As a simple example, when the antenna resistance 201 is R = 50, the reactance X is -20, and the resistance 203 of the generator 200 is R = 50 and the reactance X is 0, the matching communication network unit 202 It is good to design so that the value of R = 0 and X = 20 may be the same.

In general, a high frequency circuit uses a reflection coefficient as a measure to determine whether radio waves are efficiently transmitted. When a circuit including an antenna and a matching communication circuit unit 202 is viewed from the generator 200, the reflection coefficient should be designed to be small.

The standard is to ensure that less than 10 dB, or less than 10 percent, of the radio waves are reflected.

If the radio wave from the generator 200 is reflected without passing through the matching network unit 202 and the antenna, this loss is called a mismatch loss. If the loss can be eliminated, a large amount of radio wave is generated from the terminal (cell phone). ) Can be sent to the base station, allowing for a smoother call.

The current matched state can be monitored from the amount of reflected radio waves.

Currently, the antenna matching circuit of a cellular phone consists of a passive element having a fixed value, that is, a lumped inductor and a capacitor.

As a way of more actively coping with the matching problem, the characteristics of the matching circuit can be adjusted to a desired value by inserting active devices such as transistors and diodes into the matching circuit to change the DC bias applied to the device or devices.

However, the resistance values that can be switched by this type of active matching network circuitry are extremely limited in many cases and may not provide adequate matching when the antenna resistance is severely changed.

In addition, although there is an advantage that the value of the matching circuit can be continuously changed according to the bias, the possibility of operation failure of the complicated bias circuit and the active element has a problem in the application.

As such, current junction circuits are mostly inexpensive and simple in structure, but their values are fixed, providing a good match by satisfying only one of the resistance values that an antenna can have.

In recent years, even when one or more antennas are standardized, matching problems become more difficult, and matching circuits with only one fixed value are inadequate to deal with antenna resistance that varies with the environment.

One way to approach this problem is to introduce an active matching network, as in Figure 3, to vary the characteristics of the circuit to some extent.

That is, FIG. 3 is an impedance matching circuit diagram of a conventional cellular phone. The low noise filter unit 300 removes an unnecessary signal from a high frequency signal transmitted to a base station and received through an antenna ANT of the terminal, and the antenna ANT. Matching network circuit unit 301 to match the resistance to the input resistance of the transmitting and receiving end so that the received radio wave is not reflected, and a high frequency signal input by impedance matching from the matching communication network circuit unit 301 in one direction, that is, the receiving end In addition, the transmission message is transmitted to the base station input from the transmitter, and is composed of an isolator 302 for transmitting to the base station through the matching communication network circuit unit 301, the low noise filter unit 300 and the antenna (ANT).

In this way, the impedance matching circuit of the conventional cellular phone antenna configured is first transmitted to the base station, when a high frequency signal is received by the low noise filter unit 300 through the antenna ANT of the terminal (cell phone), the low noise filter unit 300 described above. ) Removes unnecessary signals from the received high frequency signals and inputs them to the matching communication network circuit 301.

The matching communication network unit 301 matches the impedance of the antenna ANT with the input resistance of the transmitting and receiving terminals and inputs the impedance to the isolator 302.

The isolator 302 transmits a high frequency signal input by impedance matching in the matching communication network unit 301 in only one direction and does not transmit in the reverse direction.

That is, the high frequency signal received through impedance matching through the matching network circuit unit 301 is supplied to the receiving end, and during transmission, the transmission message supplied from the transmitting end is matched with the matching network circuit unit 301, the low noise filter unit 300, and the antenna ANT. ) Is transmitted to the base station.

However, the impedance matching circuit of the conventional cellular phone antenna, as described above, can change the characteristics of the impedance to some extent, but there is a problem in that the complexity of the circuit arises.

Accordingly, an object of the present invention is to provide an impedance adjusting apparatus for a cellular phone antenna that optimizes a call rate between a base station and a terminal by optimally adjusting a change in resistance value of a cellular phone antenna regardless of the surrounding environment in view of such a conventional problem. In providing.

Means for achieving the object of the present invention includes at least one impedance matching means for matching the impedance of the antenna side and the impedance of the internal transceiver end of the communication terminal and the amount of radio waves reflected from the transceiver end side A power comparing means for comparing the electric wave amount measured by the power measuring means with a set reference value and outputting a result value, and selecting an appropriate impedance matching means according to the result value of the power comparing means. At least one or more matching selection means for transmitting the radio wave of the base station through an impedance matching means and transmitting the radio wave of the base station to the receiving means, and the power measurement means or the matching selection of the radio wave of the transmitting end or the impedance-matched electric wave provided to the receiving end. Circulators selectively transmitting by means To be achieved as yirueojim, hereinafter will be described in detail based on the accompanying drawings, the present invention.

4 is a block diagram of an impedance adjusting device of a cellular phone antenna according to the present invention. As shown in FIG. The first and second impedance matching units 403 and 404 for matching the low noise filter unit 400 and the impedance of the antenna ANT to the input impedance of the transmission and reception terminals inside the communication terminal. And a power measurement unit 406 for measuring the amount of radio waves reflected from the transmission and reception short-circuit of the communication terminal, and comparing the radio wave amount measured by the power measurement unit 406 with a set reference value. A power comparison unit 406 for outputting, a power comparison unit 407 for comparing the radio wave amount measured by the power measurement unit 406 with a set reference value, and outputting a result value, and matching the first and second impedances Both ends of part 403, 404 The respective first and second impedance matching units 403 and 404 are connected to select the appropriate first and second impedance matching units 403 and 404 according to the result of the power comparing unit 407, respectively. The first and second matching selectors 401 and 402 for transmitting the low noise filter 400 to the base station through the antenna ANT and transmitting the radio waves of the base station to the receiving means through the reverse path. The circulator 405 selectively transmits the radio wave of the transmitter or the impedance matched signal to the receiver to the power measurement unit 406 or the first matching selector 402.

In the above, since the impedance of the cellular phone is set by various kinds of antenna structures and surroundings attached to the phone, the first and second impedance matching units 403 and 404 are sampled in the most common situations. In this situation, the impedance of the antenna ANT is measured.

For example, when there is no object around during normal communication (R = 50, X = 0Ω), when the cell phone is placed on the desk (R = 20, X = 10Ω), when there is a human body around the cell phone (R = 30, X = -20 Ω) such as the most commonly occur case is to set the resistance of the antenna (ANT) corresponding to the measurement table.

If two or three cases are set, the impedance matching unit corresponding thereto is further configured to be configured.

Thus, the operation and effect of the present invention configured in detail with reference to Figure 4 as follows.

First, when the communication terminal (cell phone) transmits a modulated high frequency signal to the circulator 405 to send a message to the base station, the circulator 405 secondly matches the radio wave of the high frequency input from the transmitting end. It is input to the selection unit 402.

At this time, if the movable terminal a 'of the second matching unit 402 and the movable terminal a of the first matching selecting unit 401 are connected to their fixed terminals b) and b', respectively, The radio wave of the transmission short circuit provided from the circulator 405 is input to the first impedance matching unit 403 through the second matching selection unit 402.

The first impedance matching unit 403 matches the impedance so that the input resistance of the transmitting end is equal to the resistance of the antenna ANT to match the fixed terminal b and the movable terminal a of the first matching selector 401. Input to the low noise filter 400 through.

The low noise filter 400 removes unnecessary noise signals from the input high frequency signals and transmits them to the base station through the antenna ANT.

At this time, when the resistance value of the antenna ANT and the impedance of the transmitting end are not properly matched by the first impedance matching unit 403, the transmitted radio wave is reflected back to the circulator 405 through the reverse process and inputted. The circulator 405 supplies all of the reflected and input radio waves to the power measuring unit 406.

The power measuring unit 406 converts a radio wave reflected from the circulator 405 into a direct current voltage and inputs it to the power comparing unit 407.

The power comparison unit 407 compares the amount of radio waves detected and input by the power measurement unit 406 with the amount of radio waves originally intended to be transmitted, and the first and second matching selectors 401 when the amount of reflected radio waves is large. (A) and (a ') are connected to the fixed terminal (c) and (c') side.

Accordingly, the high frequency signal transmitted from the transmitting end is again impedance-adjusted by the second impedance matching unit 404 through the circulator 405 and the second matching selecting unit 402, and thus, the first matching selecting unit 401, The low noise amplifier 400 and the antenna ANT are transmitted to the base station.

When the reflected wave is less as a result of the comparison by the power comparing unit 407, as described above, the movable terminals (a) and (a ') of the first and second matching selection units 401 and 402 are fixed terminals thereof. The first impedance matching unit 403 is selected by switching to (b) and (b ').

In addition, the first and second in the state in which the high frequency radio waves are transmitted from the base station and input to the first matching selector 401 through the antenna ANT and the low noise filter 400 of the communication terminal through a transmission and reception path. If the movable terminals (a) and (a ') of the matching selector (401) and (402) are switched to their fixed terminals (c) and (c'), the radio waves input from the low noise filter unit 400 are described above. As described above, impedance matching is performed through the second impedance matching unit 404 and input to the circulator 405 through the second matching selecting unit 402.

The circulator 405 provides the radio wave of the base station received through the second matching selector 402 to the receiving end of the communication terminal.

At this time, the resistance value of the antenna ANT and the input impedance of the receiving end are not properly matched by the impedance matching of the second impedance matching unit 404, so that radio waves are reflected from the receiving end and the power is supplied through the circulator 405. When input to the measuring unit 406, as described above, the power measuring unit 406 converts the reflected electric wave into a DC voltage and inputs it to the power comparing unit 407.

The power comparing unit 407 compares the amount of reflected waves detected by the power measuring unit 406 with the amount of radio waves to be received, and if the amount of reflected waves is large, the movable terminals of the first and second matching selectors 401 and 402. (a) (a ') is switched to its fixed terminals (b) and (b') side, and impedance matching is normally performed through the first impedance matching unit 403 for reception.

In addition, the first and second matching selector 401, 402 can be easily formed by the respective diode and DC power supply.

That is, the cathodes of the two diodes are connected and their connection points are commonly connected to the input terminal of the circulator 405, and the respective anodes are connected to the first and second impedance matching units 403 and 404 described above. When the result value of the power comparing unit 407 is applied to the anode of each diode through the choke coil, the first and second impedance matching units 403 and 404 connected thereto according to the conduction of the respective diodes are applied. It operates to match impedance.

As described in detail above, according to the present invention, regardless of the type of antenna, the length of the antenna, the material of the covering surrounding the antenna and the surrounding environment of the cellular phone, the impedance of the transmitting and receiving end of the cellular phone of the antenna is selectively adjusted. As a result, the communication failure rate between the base station and the terminal is reduced and communication efficiency is improved.

Claims (3)

At least two impedance matching means for selectively matching the impedance of the antenna side with the internal transmitting and receiving end of the communication terminal, power measuring means for measuring the amount of radio waves reflected from the transmitting and receiving end, and in the power measuring means At least two matching selection means for selecting the impedance matching means according to the obtained radio wave amount and transmitting the radio wave of the transmitting end to the base station through the impedance matching means and transmitting the radio wave of the base station to the receiving means, and the radio wave or impedance matching of the transmitting end And a circulator for selectively transmitting a radio wave provided to a receiving end to the power measuring means or a matching selecting means. The impedance adjusting device of claim 1, wherein the impedance matching means is composed of matching circuits designed independently to correspond to representative antenna resistances. The impedance adjusting device of a cellular phone antenna according to claim 1, further comprising a power comparing means for comparing the amount of radio waves obtained from the power measuring means with a set reference value and controlling the first and second matching selecting means with the resultant values. .