FI104523B - Mobile radio telephone - Google Patents

Description

104523

MOBILE PHONE - MOBILE RADIO TELEPHONE

This invention relates to mobile radiotelephones. The invention has a special, though not exclusive, connection to the mobile radiotelephones used in the pan-European cellular radio network, commonly referred to as the Groupe Special Mobile (GSM) system.

Mobile phones have to face conflicting demands of compact size, long battery life, and high transmit power. In addition, in order to accommodate GSM specification, the mobile radiotelephone must agree to a number of special classes. These classes combine the transmitter power capability with the receiver's dynamic range performance, and thus any increase in power to the transmitter alters the receiver performance specification.

Manufacturers of mobile radiotelephones used in the GSM system produce a range of products that meet the requirements of mobile radiotelephones used in the GSM system. At one extreme, the telephone may take the form of a handheld unit, which is designed to be as small and light as possible, this at the expense of transmit power and receiver performance. At the other end, the phone may be installed in a car that uses the car battery or a large stand-alone NiCd battery to provide. : Output power of a large earth transmitter, but the result is a larger unit that is less portable.

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To achieve the benefits of both these extremes, manual 3Q. the portable unit can be connected to a unit called a power amplifier * · «* · * ·, installed eg in the boot of a car *. This allows the handheld unit to have such a phone in the car. * ··. performance when the handheld unit is connected to a 35,; t amplifier unit. However, it is necessary to know the effect of the amplifier unit on the · · * · 2 104523 receiver in the handheld unit in order to accurately measure the magnitude of the received signal. In known mobile radiotelephones, for example, as disclosed in European Patent Application EP-0338834, signals are transmitted between a transmitter in a handheld unit and a power amplifier at a final signal frequency. The principal unknown in predicting the effect of the gain unit on the receiver in the Kos portable unit is thus the length and hence the losses produced by the cable which manually combines the 10 portable unit and the gain device through which the radio frequency signals at the carrier frequency are transmitted.

It is an object of the present invention to provide a mobile radio-helix comprising a mobile unit and an amplification unit in which the above drawbacks are minimized.

In accordance with the present invention, there is provided a cellular radio telephone comprising a portable unit and an amplifier unit, each of the 20 portable unit and the amplifier unit being effective in receiving and transmitting signals, means for generating intermediate signals in a portable unit from signals received by the portable unit, being: characterized in that it comprises means for generating intermediate 25.J frequency signals in the amplifier unit from the signals received by the amplifier unit and means for enabling the portable unit to receive the amplifier units-. . intermediate frequency signals produced by KÖ.

Thus, in the mobile radiotelephone according to the invention, the signals ·· 'are transmitted between the amplifier unit and the portable unit at intermediate frequencies, which results in a minimal loss in the cable connecting the two units.

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Preferably, the portable unit comprises means for generating signals which the amplification unit can use to produce intermediate frequency signals.

Preferably, the mobile radiotelephone comprises intermediate frequency signal processing means and conversion means which permit the intermediate frequency signal processing means to process the intermediate frequencies of the signals received from either the portable unit or the gain unit. Thus, the mobile radiotelephone 10 according to the invention minimizes the doubling of the connection in the amplification unit and the portable unit, thereby saving the telephone size and cost.

An embodiment of a mobile radiotelephone according to the invention will now be described, by way of example, with reference to the accompanying drawing, which is a block diagram of a telephone.

With reference to the drawing, the mobile radio telephone described is for use in a GSM system. The telephone comprises 20 handheld units, denoted by 1, and a gain unit, denoted by 3, located, for example, in the luggage compartment of the car (not shown). The handheld portable unit 1 is designed to be capable of autonomous operation, but contains components that, overall, have lower performance than those incorporated in the amplifier unit.

• i ». . Both the handheld unit 1 and the amplifier unit • «« * · .. * 3 include respective antennas 5, 7. The receiver unit 1 and jb 'amplifier unit 3 also each contain corresponding combining elements 9,11, which are suitable for signals received with respective antennas 5,7. , and designed to allow a single antenna 5 or 7 to both transmit and receive signals. The connecting means 9 or 11 is 4 104523 implemented in a manner known to a person skilled in the field of mobile radiotelephony, for example a combination of filters or switching elements.

The outputs of the connecting means 9 and 11 are coupled to respective mixers 13 or 15, to which respective signal paths between the connecting means 9 or 11 and mixer 13 or 15 are, if necessary, provided with a filter (not shown). The mixer 13 included in the hand-held unit 10 is selected to meet the requirements of low power consumption, cost, and size. The mixer 15 included in the gain unit 3, on the other hand, is a high-end mixer that provides high performance as specified in the GSM specification when using a high power transmitter.

In the handheld unit 1, the input to the mixer 13 is provided with signal generating means 17 which include a local oscillator and radio frequency (RF) carrier signal generating means. The output of the mixer 13 is coupled via a switch 20 to an intermediate frequency (IF) processing circuit expressed as a unit 21 comprising channel selectivity and demodulation functions and representing the remainder of the receiver signal path capable of: · ··: all earth antennas 5.7 further processing of received signals j2§j. The third connector of the switch 19 is coupled to a reactive coupler 23 comprising a simple m inductive and capacitive network reactive. the connector 23 is connected by a coaxial cable 25 to the corresponding * · · I .. * reactive connector 27 in the amplifier unit 3, which · · · * connector 27 is connected across the two terminals ·: * of the mixer 15.

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The coaxial cable 25 is also effective in enabling the signals generated by the local oscillator in the signal generating unit 17 to be transmitted to the amplifier unit 3. This enables the amplifier unit 3 to produce its own IF signals from the RF signals received by the antenna 7.

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Both units 1.3 include the corresponding power amplifiers 29.31. The power amplifier 29 included in the Kos portable unit is designed to provide typically 3 W carrier signal power in pulses as specified in the GSM-e-10 stack controlled by hand in the portable unit. The power amplifier 31 included in the amplifier unit 3 is a high power amplifier having variable power control, the amplifier 31 being capable of generating typically 12 W carrier signal power pulses as specified by GSM, generating these pulses, and the power amplifier 31 . Amplifier 31 includes bandpass and harmonic filters (not shown) that can eliminate false signals.

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Thus, in telephony, mixers 13,15 produce corresponding IF signals from RF signals received by antennas 5,7.

The handheld unit 1 then processes either its own *: **: IF signals or the IF signals generated by the amplifier unit 3, depending on the position of the switch 19, which signals are communicated via cable 25. Since the GSM system does not require simultaneous transmission and reception, the signal. The generating unit 17 can be used to produce both a transmitted RF signal to be used as a carrier signal when the antennas 5,7 are used in the transmit mode and as a local oscillator when the antennas 5,7 are in the receive mode.

»* · * ·. ·; ·. The power control system for the power amplifier 31 in the amplifier unit 3 is designed to withstand relatively large changes in the signal level of the RF carrier signals produced by the signal generating unit 17. Thus, the frequency response and cable loss effects are minimized when the telephone is used in transmission mode. In addition, since the gain profile of the gain unit 3 5 maintains a relatively high level up to the handheld unit 1 when the gain unit 3 operates in receive mode, and the IF processing unit 21 in the handheld unit 1 contains all necessary channel filtering, the noise in the cable is minimized.

It will be seen that, since the intermediate frequencies provided by the handheld unit 1 and the amplifier unit 3 are a decade or more out of the RF frequency, the RF and IF signals can be combined using only one inductive element and one capacitive element at each combiner 23,27. The quality of the components in the combiners 23,27 is not critical and it is not necessary to further define the values of the components. When such inductive and capacitive networks have sufficient performance, performance can be enhanced by triangular networks in which the respective resistive elements are coupled across the inductor and capacitor at each of the combinations 23,27. A simple wiring harness - *: ··: can be used to combine the Amplifier Unit 3 and the Handheld Unit: 25i Unit 1, the Amplifier Unit 3 transforming the performance of the Handheld Unit 1 into a higher performance Travel Unit unit. This enables an enhanced counter ·. : receiver performance, as well as improved transmitter output power, and • meets the GSM requirements for the mobile phone ♦ · · 30, both in the handheld unit and in the amplifier unit. For example, a handheld unit can be orally "configured to meet the requirements of GSM Class 4 when unit 1. ···. Is used independently, while connected to a gain unit via cable 25 λ. The duplication of amplifiers in amplifier unit 3 and handheld unit 1 is minimized and thus cost-effective, and it should be noted that usually the receiver's performance limiter is an input mixer 5 used to convert the RF carrier signal into intermediate frequency.

It should also be noted that the telephone requires only one RF cable 10 to connect the gain unit to the handheld unit 1. Variable lengths of cable 25 are permitted without requiring the circuits included in either unit 1.3 to be matched. Since the signals received from the signals received by the antennas 5,7 communicate between the units 15 at intermediate frequencies, a minimum loss in cable 25 is achieved. In addition, low signal levels are used in cable 25, thereby reducing the risk of interference. Bandpass filtering at either end of the cable 25 reduces interference. The coaxial cable 25.2.0 can also be used for DC transmission as well as signals with RF and IF. Thus, the amplifier units 3 can be used to supply power to the handheld portable unit 1, for example, such as to charge the batteries (not shown) lit ·· in the handheld portable unit 1.

It should be noted that when the RF carrier and local oscillator signal generating units are shown to be incorporated in the handheld unit 1, they may be optionally or additionally included in the amplifier unit. 3.

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Claims (8)

8 104523 A mobile radiotelephone comprising a portable unit (1) and an amplifier unit (3), both of which the portable unit (1) and the amplifier unit (3) are capable of receiving and transmitting signals, the unit (17) for generating intermediate frequency signals in the portable unit (1). the unit (1) receiving signals, the telephone being characterized in that it comprises means (15,17) for producing intermediate frequency 10 signals in the amplifier unit (3) from the signals received by the amplifier unit (3) and a unit (25) enabling the portable unit (1) ) receives intermediate frequency signals provided by the gain unit (3). 15 A mobile radiotelephone according to claim 1, characterized in that the portable unit (1) comprises a unit for generating signals which can be used by the amplification unit (3) to produce intermediate frequency signals. 20 A mobile radiotelephone according to any one of the preceding claims, characterized in that both the portable unit (1) and the amplification unit (3) comprise respective reactive 1. connecting elements (23,27) suitable for receiving «· 2 * 5: signals from another unit (1). or 3). • ·· • · * »·« A mobile radiotelephone according to claim 3, characterized in that each reactive coupler (23 or 27) consists of one capacitive and one inductive element. A mobile radiotelephone according to any one of the preceding claims, characterized in that it comprises an intermediate frequency. a processing unit (21) and an exchange unit (19) adapted to permit the intermediate frequency processing unit (21) to process intermediate frequencies received from signals received from either the portable unit (1) or the gain unit (3). A mobile radiotelephone according to any one of the preceding claims, characterized in that the amplifier unit (3) comprises a power amplifier (31) suitable for generating signals for transmission of the amplifier unit (3) whose power level is controlled by the signals provided by the portable unit (1) through. A mobile radiotelephone according to any one of the preceding claims, characterized in that the unit (25) which enables the portable unit (1) to receive the intermediate frequency signals produced by the 15 amplification unit (3) is also suitable for transmitting DC power from the amplifier unit (3) to the portable unit (1). Travel cell diophone according to any one of the preceding claims, characterized in that the means (15,17) for generating the intermediate frequency signals in the amplifier unit (3) contain a mixer (13) of a higher quality than that of the portable unit s * (1). • '· »·« »ie» · · · · · · ii »· ·•••••••••••••••••••••••••• MM · · »Tl • M <φ Φ * I · I« t * · t · «I« «I 10 104523