Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1999-07-26
2001-12-11
Trost, William (Department: 2746)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000, C455S070000, C455S126000
Reexamination Certificate
active
06330455
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission power controller for use in a mobile communication terminal equipment.
2. Description of the Prior Art
Control circuits for controlling the maximum average transmission power to be below a certain value that is stipulated under the Radio Related Law generally include the so-called ALC (Automatic Level Control) circuit in conventional mobile communication terminal equipment of an analog FM (Frequency Modulation) system.
FIG. 4
exemplifies an arrangement of this circuit.
VCXO (Voltage Controlled Crystal Oscillator)
21
generates an IF (Intermediate Frequency) signal that is frequency modulated with a modulation signal.
Band pass filter
23
restrains a bandwidth for the output signals from VCXO
21
to eliminate undesired waves and allows the IF signal with a desired frequency to pass through.
IF amplifier
24
amplifies the IF signal output from band pass filter
23
. Band pass filter
25
restrains a bandwidth for the output signals from IF amplifier
24
to eliminate undesired waves and allows the IF signal with the desired frequency to pass through.
Mixer
26
mixes the IF signal output from band pass filter
25
with a local signal output from local oscillator
27
to convert the IF signal to a RF (Radio Frequency) signal.
Band pass filter
28
restrains a bandwidth for the output signals from mixer
26
to eliminate undesired waves and allow the RF signal with a desired frequency to pass through. The RF signal output from band pass filter
28
is power-amplified at transmission power amplifier
29
and then radiated from antenna
30
as a transmission radio wave.
Branching filter
31
partly separates the output signal from transmission power amplifier
29
. Detector
32
detects the output signal from transmission power amplifier
29
separated by branching filter
31
. Smoothing circuit
33
smoothes the output signal from detector
32
. Thus obtained is a DC voltage (hereinafter referred to as a detected voltage) corresponding to an average transmission power from the mobile communication terminal equipment including the transmission power controller in FIG.
4
.
Threshold setting circuit
34
, on the other hand, outputs on the basis of a threshold data signal a threshold voltage corresponding to the maximum average transmission power stipulated under the Radio Related Law.
Voltage comparator
35
compares the detected voltage output from smoothing circuit
33
with the threshold voltage output from threshold setting circuit
34
.
A negative feedback control is further performed so as to equalize the average transmission power from the mobile communication terminal equipment with an allowable maximum average transmission power by adjusting at supply voltage controller
36
a supply voltage, bias voltage and the like of transmission power amplifier
29
.
The above is the operation of the transmission power controller (ALC circuit) in the mobile communication terminal equipment of the conventional analog FM system.
CDMA (Code Division Multiple Access) is recently proposed as a technology for mobile communication terminal equipment in the next generation.
In order to overcome the Near-Far Problem in the CDMA system, it is necessary to control the transmission power of the mobile communication terminal equipment precisely over a wide range so that radio waves transmitted from mobile communication terminal equipments belonging to the same cell can arrive at a base station with substantially identical signal levels. The range for the control is wider than 80 dB and the resolution for the control is 1 dB.
It is impossible, however, to realize such complicated transmission power control by the ALC circuit as shown in FIG.
4
.
In order to overcome this problem, a method of precisely adjusting a control voltage of a variable gain amplifier which operates at IF stage with a wide dynamic range is employed. “RF2609” available from RF Micro Device Inc. is well known as an example of such variable gain amplifier.
FIG. 5
shows an arrangement example of a transmission power controller with such variable gain amplifier. Quadrature modulator
41
is used in CDMA because modulation methods such as QPSK and offset QPSK are employed, instead of VCXO in the mobile communication terminal equipment of the analog FM system.
Quadrature modulator
41
has two base-band inputs: an in-phase component (I-signal); and a quadrature component (Q-signal). Quadrature modulator
41
modulates a local signal output from local oscillator
42
with the I-signal and Q-signal to generate an IF signal.
Band pass filter
43
restrains a bandwidth of the output signal of quadrature modulator
41
so as to eliminate undesired waves and obtain an IF signal with a desired frequency.
Variable gain amplifier
44
amplifies the IF signal output from band pass filter
43
. Band pass filter
45
restrains a bandwidth of the output signals from variable gain amplifier
44
to eliminate undesired waves and allows the IF signal with the desired frequency to pass through.
Mixer
46
mixes the IF signal output from band pass filter
45
with a local signal output from local oscillator
47
to convert the IF signal into an RF signal.
Band pass filter
48
restrains a bandwidth of the output signals from mixer
46
to eliminate undesired waves and allow an RF signal with a desired frequency to pass through. The RF signal output from band pass filter
48
is power-amplified at transmission power amplifier
49
and then radiated from antenna
50
as a transmission radio wave.
The circuit of
FIG. 5
does not use ALC circuit as shown in FIG.
4
. Instead, the circuit of
FIG. 5
includes D/A converter
57
to generate a control voltage for variable gain amplifier
44
and controller
56
to set data for D/A converter
57
.
Two types of transmission power control, which are an open loop power control and a closed loop power control, are performed in CDMA systems. In the open loop power control, a mobile communication terminal equipment monitors the transmission power from a base station. If the transmission power is relatively higher, the mobile communication terminal equipment decides that the terminal located near to the base station and lowers its own transmission power. If the transmission power from the base station is relatively lower, the mobile communication terminal equipment decides that the terminal located far from the base station and elevates its own transmission power. The open loop power control signal is improved to controller
56
by the CPU of the mobile communication terminal equipment.
In the closed loop power control, the base station monitors the transmission power from the mobile communication terminal equipment. The base station transmits to the mobile communication terminal equipment a control signal for lowering the power if the transmission power is relatively higher and for elevating the power if the transmission power is relatively lower. The mobile communication terminal equipment periodically varies a control value of the transmission power by a certain variable amount such as 1 dB step in accordance with the total power control signal.
Controller
56
comprises an up/down counter
61
as shown in FIG.
6
. The aforementioned total power control signal is a signal of 1 bit. When the signal has a value of “1”, the signal instructs to elevate the transmission power. When the signal has a value of “0”, the signal instructs to lower the transmission power. The total power control signal is fed to U/DB terminal of up/down counter
61
through TPC (Total Power Control) terminal of controller
56
.
Up/down counter
61
counts periodically in synchronism with a clock signal fed to the CK terminal and counts up or down when an input to U/DB terminal is “1” or “0”. Up/down counter
61
outputs its count value as digital data from the Dout terminal. D/A converter
57
converts the output data to an analog signal and outputs the analog signal as a control signal for variable gain amplifier
44
.
The control
Milord Marceau
NEC Corporation
Trost William
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