JP2000332622A - Radio transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the power efficiency of an A class operation power amplification part in the radio transmitter of a π/4QPSK modulation system and the like. SOLUTION: An I signal voltage level detection part 11 and a Q signal voltage level detection part 12 detect the voltage levels of an I signal S1 and a Q signal S2 based on the I signal S1 and the Q signal S2 of base bands from root Nyquist roll-off filters 4 and 5 for I signal and Q signal. A power calculation part 13 calculates a power level from the detected I signal voltage level and the Q signal voltage level. Bias voltage Vg is outputted from a bias voltage output part 14 in accordance with the calculated power level and the bias of a power amplification part 10 is set with bias voltage. Thus, bias is set to be shallow when the input level to the power amplification part 10 is small and it is set to be deep when the level is large, so that the power efficiency of DC power (B) is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio transmitter,
More specifically, the present invention relates to improvement in power efficiency of a power amplification unit in a transmitter using a modulation method such as 、 ４ (π / 4) QPSK (phase shift keying) or QAM (quadrature amplitude modulation).

[0002]

2. Description of the Related Art One form of digital transmission equipment is π / 4
There is a wireless transmitter using a modulation method such as QPSK or 16-level QAM. FIG. 3 is a main block diagram showing an example of a conventional radio transmitter using the quarter-πQPSK modulation method. Hereinafter, the operation of FIG. 3 will be described. The original data Di to be transmitted is input to a serial / parallel (S / P) converter 1 where it is converted from serial data to parallel data. The converted parallel data is branched and input to the I signal mapping processing unit 2 and the Q signal mapping processing unit 3.
The mapping processing units 2 and 3 perform mapping processing on input data in accordance with a predetermined format in the π-QPSK modulation scheme of four quarters. For each symbol (2 bits) of input data, the phase is determined according to the data content. Set. Specifically, with respect to a predetermined reference point on one of the orthogonal I axis and Q axis,
If the symbol is “00”, the phase is rotated by + π / 4. If the symbol is “01”, the phase is rotated by + 3π / 4. If the symbol is “10”, the phase is rotated by −π / 4. If -3π
/ 4 phase rotation.

Each of the signals subjected to the mapping processing is a root Nyquist roll-off filter (hereinafter, referred to as a Nyquist filter) 4 for an I signal and a Q signal.
Enter the same in 5. This Nyquist filter is a kind of LP
It is a well-known device having an F (low-pass filter) function, and filters the signal after the mapping process so as not to cause intersymbol interference. The output signals of the Nyquist filters 4 and 5 are converted from digital signals to analog signals in D / A converters 6 and 7, respectively, and sent to a quadrature modulator 8. The quadrature modulation unit 8 receives the I signal from the D / A conversion unit 6 and the Q signal from the D / A conversion unit 7.
A quadrature modulation process is performed based on the signal and the signal from the oscillating unit 9 that generates the carrier frequency signal. The quadrature-modulated signal is amplified to a predetermined transmission power in a power amplifier 31 and the signal is amplified.
Outputs So. In the case of a modulation method such as quadrature π QPSK or QAM, the operation mode of the power amplifier 31 is a class A operation. Conventionally, the bias setting in this class A operation is almost always fixed.

[0004]

Therefore, the power amplifier 31
Irrespective of the level of the signal input to the power amplifier 31, constant DC power is always consumed, and the power amplifier 31 has a low power efficiency. An object of the present invention is to improve this disadvantage, and an object of the present invention is to provide a wireless transmitter in which a bias voltage of a power amplifier is varied according to an input level for power amplification to improve power efficiency.

[0005]

SUMMARY OF THE INVENTION The present invention provides a .pi.
A radio transmitter that amplifies a signal that has been subjected to data processing based on a modulation scheme such as SK or QAM to a predetermined power by a power amplifier for class A operation and transmits the signal, generates a baseband I signal and a Q signal.
A wireless transmitter comprising a bias setting means for detecting a level of a signal input to the power amplifier based on a signal and setting a bias voltage for the power amplifier in accordance with the detected signal level. To provide.

In addition, the baseband I signal and Q signal are subjected to mapping processing in the quarter π QPSK modulation system, and are subjected to filtering processing so as not to cause intersymbol interference. The signal is from the root Nyquist roll-off filter.

[0007] The bias setting means may control the I and Q signals based on the baseband I and Q signals.
An I signal voltage level detector and a Q signal voltage level detector for detecting the voltage level of each signal; and a power calculation for calculating a power level from the I signal voltage level and the Q signal voltage level detected by the respective detectors. And a bias voltage output unit that outputs a bias voltage according to the calculated power level.

The voltage level detected by the I signal voltage level detector or the Q signal voltage level detector is defined as an effective voltage value. . Alternatively, the same voltage level is set as an average voltage value.

Further, the power calculation unit may detect the detected I
It is assumed that the value of the half of the sum of the squares of the signal voltage level and the Q signal voltage level is calculated.

The bias voltage output from the bias voltage output section is set to a bias voltage such that the power of the DC power supply input to the power amplification section decreases as the calculated power level decreases.

[0011]

Embodiments of the present invention will be described below with reference to the drawings based on embodiments. FIG. 1 is a main block diagram showing an embodiment of a wireless transmitter according to the present invention.
In FIG. 1, components equivalent to those in FIG. 3 are denoted by the same reference numerals, and 10 is a power amplifier (PA) for class A operation, which amplifies the signal from the quadrature modulator 8 to a predetermined power. Reference numeral 11 denotes an I signal voltage level detection unit which detects the voltage level of the baseband I signal S1 from the I signal Nyquist filter 4. Reference numeral 12 denotes a Q signal voltage level detector, which is a baseband Q signal S2 from the Q signal Nyquist filter 5.
Voltage level is detected. Reference numeral 13 denotes a power calculation unit that calculates power from the detection data from the I signal voltage level detection unit 11 and the detection data from the Q signal voltage level detection unit 12. A bias voltage output unit 14 outputs a bias voltage (Vg) according to the power data calculated by the power calculation unit 13 and sets a bias voltage of the power amplification unit 10.

Next, the operation of the present invention will be described. It should be noted that reference numerals 1 to 9 are the same as those in FIG. The output signals of the I signal Nyquist filter 4 and the Q signal Nyquist filter 5 are D / A
While being sent to the conversion unit 6 or the D / A conversion unit 7, it is branched and input to the I signal voltage level detection unit 11 and the Q signal voltage level detection unit 12. The output signals S1 and S2 of the Nyquist filters 4 and 5 have waveforms that are accentuated with respect to the input signal (a) as shown in (b) of FIG. fluctuate. Each of the voltage level detectors 11 and 12 detects a voltage level from the signal S1 or S2. The detected voltage level is an effective value or an average value. Regardless of which value is detected, each of the detectors 11 and 12 detects an instantaneous value of a signal at a predetermined interval, and when an effective value is detected, calculates an effective value based on the detected instantaneous value. When the average value is detected, the detected instantaneous values are averaged for a predetermined period. In case of average value detection,
Since the long-term average of FIG. 2A is zero as it is,
The averaging is performed in a shorter time than the pulse, or after the polarities are once aligned in one direction (such as rectification), the averaging is performed.

The voltage level detected by each of the detectors 11 and 12 is calculated by a power calculator 13 as a root-mean-square value (the square root of the sum of the squares of the effective value or the average value). The calculated mean square value represents the input level of the power amplifier 10. Therefore, a bias voltage corresponding to the mean square value is output from the bias voltage output unit 14. The output bias voltage becomes smaller as the mean square value becomes smaller.
The voltage value is set so that the input power from the DC power supply (B) to 10 becomes small. Thus, the operating point of the power amplifying unit 10 is set according to the input level to the amplifying unit, and wasteful power consumption can be eliminated even when a small level is input.
FIG. 2B shows a circuit configuration example of the power amplifying unit 10. This figure uses FET (Q1) as an amplification element.
The voltage Vg applied to the gate (G) terminal is the output voltage from the above-mentioned bias voltage output unit 14, and the voltage Vg changes according to the input level to the power amplification unit 10. As a result, the input power from the DC power supply Vd (B) to the drain (D) terminal also changes. The same operation is performed when the amplifying element Q1 is a transistor. The matching circuit 21 is for matching with the quadrature modulator 8, and the matching circuit 22 is for matching with a subsequent circuit (not shown). The capacitors C1 and C2, the choke coils RFC1 and RFC2, and the like are for preventing unnecessary components.

[0014]

As described above, according to the present invention, 4
In a power amplifier of a digital modulation type transmitter such as π (π / 4) QPSK or QAM, a bias voltage is variably set according to a level input to the amplifier in class A operation. Power consumption can be improved and power efficiency can be improved as compared with the conventional case. In addition, since the amount of heat generated by the amplifying elements (such as FETs) and circuit components constituting the power amplifying unit is also reduced, measures for radiating heat such as the volume of the radiating plate are facilitated and the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a main part block diagram showing one embodiment of a wireless transmitter according to the present invention.

FIG. 2 is an explanatory diagram related to FIG. 1;

FIG. 3 is a main block diagram showing an example of a conventional wireless transmitter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Serial / parallel (S / P) conversion part 2 I signal mapping processing part 3 Q signal mapping processing part 4 I signal Nyquist filter 5 Q signal Nyquist filter 6, 7 D / A conversion part 8 Quadrature modulation part 9 Oscillator 10, 31 Power amplifier (PA) 11 Voltage level detector for I signal 12 Voltage level detector for Q signal 13 Power calculator 14 Bias voltage output Q1 FET 21, 22 Matching circuit

Continued from the front page F-term (reference) 5J091 AA04 AA41 AA62 CA36 FA04 FA10 HA09 HA29 HA33 KA12 KA29 KA34 KA41 KA48 KA49 KA53 KA55 MA14 MA22 SA14 TA01 TA06 UW04 UW08 5J092 AA04 AA41 AA62 CA36 FA04 KA29 KA09 KA09 KA49 KA53 KA55 MA14 MA22 SA14 TA01 TA06 VL08 5K060 BB00 CC04 CC11 FF06 HH06 HH11 LL11 LL25

Claims (7)

[Claims] 1. A radio which amplifies a signal, which has been subjected to data processing based on a modulation method such as quarter-quadrature QPSK (phase shift keying) or QAM (quadrature amplitude modulation), to a predetermined power by a power amplifier for class A operation and transmits the signal. A transmitter detects a level of a signal input to the power amplifier based on a baseband I signal and a Q signal, and sets a bias voltage for the power amplifier according to the detected signal level. A wireless transmitter comprising a bias setting means. 2. A root Nyquist roll for each of an I signal and a Q signal for filtering the baseband I signal and Q signal with respect to a signal after the mapping process in the modulation scheme so as not to cause intersymbol interference. 2. The wireless transmitter according to claim 1, wherein the signal is a signal from an off-filter. 3. An I-signal voltage level detector and a Q-signal voltage detector for detecting a voltage level of each of the I- and Q-signals based on the baseband I- and Q-signals. A level detector, a power calculator for calculating a power level from the I signal voltage level and the Q signal voltage level detected by the respective detectors, and a bias voltage output unit for outputting a bias voltage according to the calculated power level The wireless transmitter according to claim 1, wherein the wireless transmitter comprises: 4. The wireless transmitter according to claim 3, wherein the voltage level detected by the I signal voltage level detector or the Q signal voltage level detector is an effective voltage value. 5. The wireless transmitter according to claim 3, wherein the voltage level detected by the I signal voltage level detector or the Q signal voltage level detector is an average voltage value. 6. The power calculator according to claim 1, wherein the power calculator calculates a half value of a sum of squares of the detected I signal voltage level and the detected Q signal voltage level. 3. The wireless transmitter according to 3. 7. The method according to claim 7, wherein the bias voltage output from the bias voltage output unit is a bias voltage such that the power of the DC power input to the power amplification unit decreases as the calculated power level decreases. Claim 3
The wireless transmitter as described.