Telecommunications – Transmitter – Measuring – testing – or monitoring of transmitter
Patent
1996-02-29
1998-11-17
Le, Thanh Cong
Telecommunications
Transmitter
Measuring, testing, or monitoring of transmitter
455 75, 455119, 455127, 331176, H04B 1700
Patent
active
058390596
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for starting a radio transmitter and to a radio transmitter using at start-up an estimated control voltage needed for locking onto a selected output frequency.
In a radio transmitter in which the transmission frequency is generated by a phase/frequency-locked loop, the output frequency of a voltage-controlled oscillator of the loop immediately after the start-up is undetermined. The output frequency is determined in accordance with the control voltage of the voltage-controlled oscillator, which is undetermined at the start-up of the radio transmitter. If there is no way of attenuating or muting a signal transmitted to an antenna for the duration of the start-up of the transmitter, it is yet desirable that the time needed for the oscillator to settle at the correct frequency will be as short as possible and the frequency error at the start-up as small as possible, whereby the frequency of the oscillator will lock over as narrow a frequency band as possible onto the desired frequency.
When a radio transmitter is started, it takes a while before the transmission frequency generated by the oscillator has settled at the correct value. If the radio transmitter is not provided with a separate transmission power muting operation (TXMUTE), in which the transmission power of the transmitter is muted at the start-up by means of electrically controllable attenuators and by controlling the operating voltages of the power amplifiers until the transmission frequency has settled at the correct value, then the radio transmitter interferes with the traffic at the adjacent frequencies during the short settling period.
Instead of the above-mentioned muting switch implemented by means of controllable attenuators and control of the operating voltages of the power amplifiers, a narrow-band channel filter can also be used in the radio transmitter, the narrow-band channel filter decreasing interference at the start-up. The drawback of this solution is that it is only suitable for lower frequencies since at higher frequencies the filter cannot be rendered sufficiently narrow-band.
The interference at the start-up is rather expensive to minimize by the above-described muting switch, which does not have the drawbacks of the channel filter. Further, in most applications the muting operation of the transmitter is needed very seldom. In particular, this applies to radio link applications in which the radio transmitter is started very seldom. In practice, the same transmitter may be in operation even for several years without interruption.
SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the above described drawbacks and to provide a method that minimizes the frequency error of the radio transmitter at the start-up and enables minimizing of the interference with the neighbouring channels at the start-up without separate transmission power muting operations. This is achieved with the method according to the invention, and by the radio transmitter according to the invention.
The idea of the invention is to start the voltage-controlled oscillator of the phase/frequency-locked loop used in generating the transmission frequency of the transmitter at the correct frequency by estimating its control voltage as accurately as possible and by setting the control voltage at the estimated value immediately before the transmitter is started by switching on an operating voltage to the voltage-controlled oscillator.
The solution according to the invention enables minimizing of the interference with the other radio traffic without the use of expensive attenuators.
Further, a separate antenna switch is not needed in the transmitter according to the invention for disconnecting the antenna from the transmitter when the frequency settles at its correct value, but the transmitter can be directly connected to the antenna.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention and the advantageous embodiments thereof will be described in greater detail wi
REFERENCES:
patent: 4254504 (1981-03-01), Lewis et al.
patent: 4511858 (1985-04-01), Charavit et al.
patent: 4731870 (1988-03-01), Black et al.
patent: 4746879 (1988-05-01), Ma et al.
patent: 4839613 (1989-06-01), Echols et al.
patent: 4893097 (1990-01-01), Zwack
patent: 4910473 (1990-03-01), Niwa
patent: 5379453 (1995-01-01), Tigwell
Hakkinen Hannu
Makinen Jarmo
Toivonen Mikko
Cong Le Thanh
Nokia Telecommunications Oy
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