PLL circuit which quickly adjusts VCO bias voltages

Details PLL circuit which quickly adjusts VCO bias voltages PLL circuit which quickly adjusts VCO bias voltages

1999-12-21

2001-11-13

Mis, David (Department: 2817)

Oscillators

Automatic frequency stabilization using a phase or frequency...

Particular error voltage control

C331S044000, C455S260000

Reexamination Certificate

active

06317004

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a Phase Locked Loop (PLL) circuit, a communication device using the PLL circuit, and a frequency adjustment method of a PLL circuit. More particularly, the present invention relates to a PLL circuit to be used in a portable communication apparatus, a communication device using the PLL circuit, and a frequency adjustment method of a PLL circuit.
2. Description of the Related Art
In portable communication apparatus such as a portable telephone, and so on, a PLL circuit is used as a local oscillator which is stable in frequency.
In
FIG. 7
, the block diagram of a known conventional PLL circuit is shown. In
FIG. 7
, a PLL circuit
1
is composed of a voltage-controlled oscillator
2
, a TCXO (temperature compensation crystal oscillator)
3
, frequency dividers
4
and
5
, a phase comparator
6
, a charging pump
7
, and a loop filter
8
. The voltage-controlled oscillator
2
is composed of an amplifier portion
2
a
, a resonance circuit portion
2
b
, a varactor diode VD in the resonance circuit portion
2
b
, and a trimming area
2
c
as an oscillation frequency adjustment mechanism. The trimming area
2
c
is formed of, for example, an electrode constituting a part of a resonance system. The resonance frequency of the resonance circuit portion
2
b
is changed by cutting and trimming the electrode and, accordingly, the oscillation frequency of the voltage-controlled oscillator
2
can be adjusted. The voltage-controlled oscillator
2
is provided with a control voltage terminal
2
d
for changing the oscillation frequency by applying a direct-current voltage to the varactor diode VD.
The output of the voltage-controlled oscillator
2
is divided and a part of the output is connected to the phase comparator
6
via the frequency divider
4
. The TCXO
3
is connected to the phase comparator
6
via the frequency divider
5
. The output of the phase comparator
6
is connected to the control voltage terminal
2
d
of the voltage-controlled oscillator
2
via the charging pump and loop filter in sequence. The frequency dividers
4
and
5
, phase comparator
6
, and charging pump
7
are not necessarily formed separately, typically being constructed in one PLL-IC.
Referring to the PLL circuit
1
of
FIG. 7
, because the oscillation frequency of the voltage-controlled oscillator
2
may not necessarily be attuned to an intended frequency in the initial state, the PLL circuit
1
is provided to adjust the oscillation frequency of the voltage-controlled oscillator
2
. Adjustment of the oscillation frequency of the voltage-controlled oscillator
2
requires that a predetermined direct-current voltage be applied to the control voltage terminal
2
d
, and therefore the PLL circuit
1
in its entirety must be operated. That is, the oscillation frequency of the voltage-controlled oscillator must be adjusted while the PLL circuit is in operation.
The adjustment the oscillation frequency of the voltage-controlled oscillator
2
while the PLL circuit
1
is in operation requires a computer, or like equipment, for controlling the PLL circuit
1
. The oscillation frequency adjustment also requires equipment for measuring the direct-current voltage applied to the control voltage terminal
2
d
, as well as a power source for operating the PLL circuit
1
. Accordingly, the requirement for such measuring equipment gives rise to the drawback of increased equipment costs for the PLL circuit
1
. Furthermore, it is necessary to perform the phase lock of the PLL circuit
1
, which disadvantageously requires extra time for adjusting the oscillation frequency.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a PLL circuit in which the oscillation frequency of the voltage-controlled oscillator can be quickly adjusted using fewer pieces of equipment before operating the PLL circuit in its entirety. Further objects of the present invention include the use of such a PLL circuit in a communication device, and also a method for frequency adjustment of the PLL circuit.
In order to attain the above-mentioned objects, a PLL circuit according to one embodiment of the present invention comprises a voltage-controlled oscillator having an oscillation frequency adjustment mechanism and a control voltage terminal, a charging pump, and a loop filter, wherein the output of the charging pump is connected to the control voltage terminal via the loop filter, and wherein a voltage application means for applying a direct-current voltage to the control voltage terminal is provided in the path from the output terminal of the charging pump to the control voltage terminal including the inside of the loop filter.
Further, in a PLL circuit according to another embodiment of the present invention, the voltage application means comprises a voltage application electrode and a wiring electrode connecting a point in the path from the output terminal of the charging pump to the control voltage terminal including the inside of the loop filter and the voltage application electrode.
Further, in a PLL circuit according to another embodiment of the present invention, a package having a plurality of terminal electrodes is provided, with one of the terminal electrodes defining the voltage application electrode.
Further, in a PLL circuit according to another embodiment of the present invention, a package having a plurality of terminal electrodes is provided, in which one of the terminal electrodes which is required only during operation of the PLL circuit defines the voltage application electrode, and the wiring electrode is formed so that the electrode can be disconnected.
Further, in a PLL circuit according to the present invention, the voltage application means comprises a voltage generation point for generating a direct-current voltage and a wiring electrode connecting the voltage generation point and a point in the path from the output terminal of the charging pump to the control voltage terminal including the inside of the loop filter, wherein the wiring electrode is formed so that the electrode can be disconnected.
Further, in a PLL circuit according to another embodiment of the present invention, the oscillation frequency adjustment mechanism of the voltage-controlled oscillator comprises an electrode which can be cut and trimmed, and the wiring electrode is made of the same material as that of the electrode in the oscillation frequency adjustment mechanism.
Further, in a communication device according to another embodiment of the present invention, the above PLL circuit is used.
Further, another embodiment of the present invention provides a frequency adjustment method of a PLL circuit including, a PLL circuit comprising a voltage-controlled oscillator having an oscillation frequency adjustment mechanism and a control voltage terminal, a charging pump, and a lop filter, wherein the output of the charging pump is connected to the control voltage terminal via the loop filter, and a voltage application means for applying a direct-current voltage to the control voltage terminal is provided in the path from the output terminal of the charging pump to the control voltage terminal including the inside of the loop filter; a step for applying a predetermined direct-current voltage to the control voltage terminal from the voltage application means, and a step for adjusting the oscillation frequency of the voltage-controlled oscillator by the oscillation frequency adjustment mechanism in a state that a predetermined direct-current voltage is applied to the control voltage terminal.
Further, another embodiment of the present invention provides a frequency adjustment method of a PLL circuit, wherein the voltage application means comprises a voltage application electrode and a wiring electrode connecting the voltage application electrode and a point of the path from the output terminal of the charging pump to the control voltage terminal including the inside of the loop filter.
Further, another embodiment of the present invention pro

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