Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/02—Transmitters
  • H04B1/04—Circuits
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
  • H04B1/40—Circuits
  • H04B1/44—Transmit/receive switching
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B15/00—Suppression or limitation of noise or interference
  • H04B15/02—Reducing interference from electric apparatus by means located at or near the interfering apparatus
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B2215/00—Reducing interference at the transmission system level
  • H04B2215/061—Reduction of burst noise, e.g. in TDMA systems

Definitions

• the invention relates to the increasing of voltage in radio equipment, particularly in radio equipment employing the TDMA principle.
• GSM radio equipment Global System for Mobile
• TDMA Time Division Multiple Access
• radios of the new European open digital TETRA radio network TErrestrial Trunked RAdio
• the 3.6V voltage is not, however, sufficient for an RF transmitter (Radio Frequency) in the TETRA where the transmitter is required to offer both good linear properties and high output power at the same time.
• RF transmitter Radio Frequency
• TETRA radio equipment therefore has to be operated using a 7.2V battery with antenna powers of 1 and 3 watts.
• charge pumps are commonly used for generating the supply voltage for very low-power devices where the maximum load current may be about 200mA.
• the oscillator of the charge pump remains switched on all the time the output voltage is to be fed to the device using the voltage.
• a typical feature in charge pumps is that as the load increases, the output voltage decreases strongly, because it does not include stabilisation.
• the efficiency of a charge pump is usually 85%.
• Charge pumps used at high frequencies have smaller components, the filtering of disturbances being then easier than at low frequencies.
• Choppers can be used for generating high voltages and currents, Choppers need an inductive component proportional to the output power, the component being the greater the higher the desired power.
• a capacitor and possibly a serial coil are needed for filtering the output voltage.
• the output voltage ripple mainly depends on the frequency of the chopper, the capacitance of the capacitor and the load current. As the load current increases, ripple increases, unless the chopper frequency or the capacitance of the capacitor is increased simultaneously.
• the ripple frequency components in the supply voltage of RF transmitters move to both sides of the transmission spectrum, thereby forming spurious emissions at the nearby area, i.e. within a distance of about 100 to 200 kHz and more from the carrier.
• the chopper should be able to feed at least the power needed by an external device.
• Choppers usually have an efficiency of the order of 80-95%. Because of the inductive components they contain, choppers always cause electromagnetic disturbance to near-by devices and components. The disturbances are difficult to filter because choppers usually operate within a frequency range of 100 to 200 kHz. The filtering of low frequencies requires large filtering components and it is all the more difficult, the closer the devices affected by disturbance are to the chopper. Furthermore, if the operation of the chopper is based on pulse width modulation (PWM), false frequencies produced by the chopper have a wide spectrum.
• PWM pulse width modulation
• a transmitter device comprising a direct voltage source, a radio transmitter for cyclic transmission, the transmitter requiring a supply voltage which is higher than said direct voltage, and means for generating said supply voltage from the direct voltage.
• the means are characterized in that they comprise a capacitive component; switching means which connect the capacitive component in parallel with the direct voltage source to charge the capacitive component between the transmitter's transmission periods and which connect the capacitive component in series with the direct voltage source during transmission periods, the voltage obtained as the sum of the direct voltage and the voltage of the capacitive component providing the supply voltage for the radio transmitter.
• the invention also relates to a method for increasing voltage in equipment which employs the TDMA principle and in which the supply voltage required during active time slots is higher than the voltage of a direct current source, the method being characterized by comprising the steps of charging a capacitive component connected in parallel with the direct current source during inactive time slots; connecting the capacitive component in series with the direct voltage source during active time slots to generate a substantially double direct voltage for the supply voltage of the equipment.
• the direct voltage source is connected in parallel with the capacitive component during unused time slots (such as receive time slots) to charge the capacitive component, whereas during an active time slots (such as transmit time slots) it is connected in series with the capacitive component to obtain a substantially double voltage.
• An advantage of the invention is that it allows a sufficiently high voltage with low disturbance to be generated for a device utilizing the TDMA. Another advantage is that the charging of the capacitive element takes place at an extremely high efficiency, almost 100%.
• the charging of the capacitive component is controlled using the same control lines that are used for connecting the biasing of the output stage of a transmitter in a device employing the TDMA principle. This provides the advantage that the charging of the capacitive component coincides precisely with frame timing, which allows the effect of any coupling interference on the operation of a receiver or a frequency synthesizer, for example, to be automatically minimized.
• a further advantage of the invention is it reduces the costs of radio equipment and additional devices for radio equipment utilizing the TDMA principle because it allows lower battery voltages to be used. This also reduces the amount of power loss because the performance of modern signal processors and other baseband elements increases continuously, thereby requiring increasingly lower supply voltages to be generated in any case.
• the signal Before a high-frequency, modulated signal RFIN that carries information and is to be inputted to an output stage is supplied to a filter FILTER and an antenna ANTENNA, the signal has to be amplified. As shown in Figure 1 , this power amplification takes place at a driver DRIVER and a power amplifier PA. However, since the RF output stage power amplifier PA employs the TDMA principle, the supply voltage VCC of 3.6V used in other parts of the transmitter is not sufficient for obtaining the required signal linearity and output power. For this reason the supply voltage must be increased to at least about 6 to 7 volts, the increased voltage being then supplied to the power amplifier PA as the supply voltage.
• the voltage is increased using a charge pump VP of Figure 1 comprising two electronic switches SW1 , SW2 and a capacitive element C.
• the first electronic switch SW1 comprises a first and a second terminal and a control member, the second terminal of the switch SW1 being coupled to the direct voltage source VCC.
• the second electronic switch SW2 comprises a first and a second terminal and a control member, the first terminal of the switch SW2 being coupled to the first terminal of the first electronic switch SW1 , the second terminal of the switch SW2 being connected to substantially constant potential.
• the capacitive component C is arranged between the first terminal of the first electronic switch SW1 , the first terminal of the second electronic switch SW2 and the output of the charge pump.
• the operation of the switches SW1 and SW2 is controlled using a line BIAS meant for controlling transmitter biasing so that when one switch is in position I, the other switch is in position II.
• the control of the switches SW1 and SW2 can also be implemented using a separate line.
• the charge pump VP of the invention is operated by charging the capacitive component of the charge pump VP, such as the capacitor C, outside transmission time slots and by discharging it during transmission time slots by means of the switches SW1 , SW2.
• a switching signal from the control member guides the first switch SW1 to position I and the second switch SW2 to position II, the capacitive component being thereby connected in parallel with a direct voltage source BATTERY to charge the capacitive component to reach a direct voltage VCC.
• the capacitive component is connected parallel with the actual direct voltage VCC.
• the capacitance must be sufficiently high to ensure that the load current does not reduce the voltage V1 too much during the TDMA transmit time slot.
• the capacitive component may alternatively be a battery, provided that it can be used, i.e. charged and discharged, in all conditions, for example in extreme temperatures, and that the battery has sufficiently high capacity.
• switches SW1 and SW2 are implemented as Metal Oxide Semiconductor transistors MOS, although other electronic structures may also be used.
• one of the switches (SW1) may be replaced with a diode, provided that a decrease in the maximum output voltage equal to the diode threshold voltage is accepted.
• Other possible switching components include SOI, HEMT and HBT transistors, microwave tubes and vacuum tubes.
• the invention can also be implemented by applying bipolar technology alone.
• the voltage of the invention produced by the charge pump VP is particularly suitable for generating the output stage voltage for RF transmitters employing the TDMA principle, and it allows the voltage to be used as the supply voltage of a power amplifier and for obtaining sufficient dynamics in a cartesian linearization circuit of a TETRA transmitter, for example, and for broadband local oscillators of frequency synthesizers.
• switching implemented according to the principle of the invention can also be used for increasing the supply voltage of other radio parts.

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

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ID=8555181

Family Applications (1)

Country Status (3)

Cited By (1)

Citations (4)

• 1999
  • 1999-08-23 FI FI991786A patent/FI19991786A/fi unknown
• 2000
  • 2000-08-22 AU AU67055/00A patent/AU6705500A/en not_active Abandoned
  • 2000-08-22 WO PCT/FI2000/000711 patent/WO2001015327A1/en active Application Filing

Patent Citations (4)

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