JPH0583308A - Digital modulation signal generator - Google Patents

Abstract

PURPOSE:To adjust a local signal so as to minimize its leakage by controlling a DC bias automatically with a controller at calibration. CONSTITUTION:Two signals inputted via a serial parallel converter 1, digital filters 2a, 2b and switches 19a, 19b are added to two outputs from a DC bias circuit 18 at adders 20a, 20b respectively and the result is given to D/A converters 3a, 3b, from which analog signals are obtained. Furthermore, an orthogonal modulation signal extracted by a branching filter 13 is given to a band pass filter 14, in which the signal is subject to band limit and a signal detected by a power detector 15 is converted into a digital signal at an A/D converter 16, a controller 17 generates a DC bias control signal by the digital signal and a switch control signal is generated therefrom. Then each control signal controls respectively the DC bias circuit 18 and the switches 19a, 19b. That is, the output of the DC bias circuit 18 is adjusted by minimizing the leakage of a local signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital radio communication device, and more particularly to a signal generator having a quadrature modulation function used as a signal source.

[0002]

2. Description of the Related Art A block diagram of a conventional embodiment is shown in FIG. Since the mixer is not ideal in the quadrature modulator, the local signal leaks to the output, and the leak amount also changes depending on the temperature change. FIG. 4 shows an embodiment in which the leakage of the local signal is reduced. In FIG. 4, the input data string is converted by the serial / parallel converter 1 and separated into I channel and Q channel. The respective signals are digital filters 2a, 2b, D / A converters 3a, 3
b, after being processed by the low-pass filters 4a and 4b,
Output cos .omega _L t and 90 ° outputs -sinω _L t phaser 8 of the local signal source 5 is mixed by the mixer 6a, 6b, are added respectively by adders 9, output by the frequency converter 10 and a level adjuster 11 To be done.
FIG. 5 shows a configuration example of a mixer used as the mixers 6a and 6b.
And shown in FIG. In the double balance mixer of FIG. 5, the DC bias of the I signal 101 and the Q signal 102 is
In the Gilbert-type multiplier shown in FIG. 6, the relative value of the DC bias of the I signal 101a and the inverted signal 101b of the I signal and the relative value of the DC bias of the Q signal 102a and the inverted signal 102b of the Q signal are respectively set to the DC bias circuit in FIG. By adjusting the local signal 100, 10
It is possible to reduce the leakage of 0a and the inverted signal 100b of the local signal. 103, 103a and 103
b is the mixed output. In the configuration of FIG. 4, the leakage of the local signals 100 and 100a and the inverted signal 100b of the local signal is manually adjusted by the DC bias circuit 7 or the DC bias value of the DC bias circuit 7 is fixed. And it was decreasing.

[0003]

However, since the adjustment is manual, frequent adjustment is troublesome, and if the DC bias value is fixed, it is not possible to adjust it at any time with respect to changes in ambient temperature. Can not. Therefore, an object of the present invention is to realize a digital modulation signal generator that does not leak a local signal due to the characteristics of a mixer by automatically controlling a DC bias circuit during calibration.

[0004]

In order to achieve such an object, in the present invention, a digital signal processor for digitally processing a data signal sequence to obtain I channel and Q channel signals, and the two signals are analog. A quadrature modulation signal generator that converts the signal into a signal and modulates the in-phase component and quadrature component of a carrier wave with each of the analog signals to obtain a quadrature modulation wave, and an output that performs frequency conversion of the quadrature modulation wave, adjusts the level, and outputs In a digital modulation signal generator including a converter, a DC bias circuit provided in the digital signal processor, an adder for adding the DC bias from the DC bias circuit to the I and Q channel signals, respectively, and the addition A switch that opens and closes the I and Q channel signals that are input to the detector, and a detector that detects leakage of a local signal in the quadrature modulated wave, In which the the output of the detector to control the DC bias circuit, also characterized in that a controller for controlling the switch.

[0005]

In the calibration, by setting the DC bias value so that the leakage of the local signal is minimized, it is possible to generate the digital modulation signal with less leakage of the local signal.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.
FIG. 1 shows an embodiment of a digital modulation signal generator according to the present invention. In FIG. 1, the same elements as those of the conventional example shown in FIG. Duplexer 1
3 is connected to the bandpass filter 14, the bandpass filter 14 is connected to the power detector 15, and the power detector 1
5 is connected to the A / D converter 16. The output of the A / D converter 16 is input to the controller 17. The DC bias circuit 18 and the switches 19a and 19b control the controller 17 according to the control signal.
Connected to. The outputs of the digital filters 2a and 2b are connected to the D / A converters 3a and 3b via the switches 19a and 19b and the adders 20a and 20b. The output of the DC bias circuit 18 is input to the adders 20a and 20b. The input data string is converted by the serial / parallel converter 1 and separated into I channel and Q channel. This signal is band-limited by the digital filters 2a and 2b, and is added via the switches 19a and 19b to the adders 20a and 2b.
0b. The two signals are added by the adders 20a, 2
0b adds the two outputs of the DC bias circuit 18, respectively, and the D / A converters 3a and 3b produce analog signals. These analog signals are low pass filter 4
After the clock components of the D / A converters 3a and 3b are removed by a and 4b, the output cos ω _L t of the local signal source 5 is removed.
And the output of the 90 ° phase shifter −sin ω _L t is the mixer 6
The signals are mixed by a and 6b and combined by the demultiplexer 12 to perform quadrature modulation.

The quadrature modulation signal extracted by the demultiplexer 13 is band-limited by the bandpass filter 14, and the signal detected by the power detector 15 is converted into a digital signal by the A / D converter 16. This digital signal causes the controller 17 to generate a DC bias control signal, and
Generates a switch control signal. These control signals are applied to the DC bias circuit 18 and the switches 19a and 19b, respectively.
To control. Reference numeral 50 is a local signal leakage level detector including a bandpass filter 14, a power detector 15, and an A / D converter 16.

When a calibration command is input to the controller 17 so as to minimize the leakage of the local signal, the DC bias is set in accordance with the flow chart shown in FIG. 3 so as to minimize the leakage of the local signal, for example, -60 dBc or less. Circuit 1
Adjust the output of 8. That is, the controller 17 opens the switches 19a and 19b and disconnects the I and Q channel signals according to the calibration command. The output of the A / D converter 16 is read and designated as "a". The DC bias of the I channel is increased by ΔV by the DC bias circuit 18. Here, the output of the A / D converter 16 is read and designated as "b".
If "a>b", the value of b is substituted for a, and "a <
3 are repeated until “b” or “a = b”. If “a <b” or “a = b”, the value of b is substituted for a and the I channel The DC bias is reduced by ΔV by the DC bias circuit 18. Next, the DC bias of the Q channel is increased by ΔV by the DC bias circuit 18. Here, the output of the A / D converter 16 is read and designated as “b”. If "a>b", the value of b is substituted for a, and "a <b" or "a = b"
The operations of C and D in FIG. 3 are repeated until if,"
If a <b ”or“ a = b ”, the value of b is substituted for a to set the DC bias of the Q channel to the DC bias circuit 18
Reduces by ΔV. Next, the DC bias of the I channel is reduced by ΔV by the DC bias circuit 18. Here, the output of the A / D converter 16 is read and "b" is read.
And If "a>b", the value of b is substituted for a, and the operations of e and f in FIG. 3 are repeated until "a <b" or "a = b". If "a <b" or "
If a = b ″, the value of b is substituted for a and the DC bias of the I channel is increased by ΔV by the DC bias circuit 18. Next, the DC bias of the Q channel is decreased by ΔV by the DC bias circuit 18. Here, the output of the A / D converter 16 is read and designated as "b." If "a>"
In the case of "b", the value of "b" is substituted for "a", and the operations of G and C in Fig. 3 are repeated until "a <b" or "a = b". In the case of b ″, the value of b is substituted for a and the DC bias of the Q channel is increased by ΔV by the DC bias circuit 18. Here, if “a” is not less than −60 dB, then in FIG. Return the operation of b and b, and perform the series of operations described above. ”
If "a" is -60 dBc or less, it is considered that the calibration is completed, and the controller 17 short-circuits the switches 19a and 19b.
And the Q channel signal.

When the Gilbert type multiplier shown in FIG. 6 is used as a mixer, the I signal and the Q signal are differential inputs. Therefore, in this case, as shown in FIG.
A differential amplifier 21 is used for signals, a DC bias is removed from the differential amplifier 21 for non-inverted signals, and a DC component is removed for inverted signals by a capacitor 23. Supply. The I signal is also shown in FIG.
Supply the DC bias as shown in. 6c in FIG.
Is a Gilbert-type multiplier.

[0010]

As is clear from the above description,
The present invention has the following effects. That is, it is possible to automatically control the DC bias by the controller at the time of calibration and adjust so that the leakage of the local signal is minimized. In addition, it is possible to reduce the leakage of the local signal even when the ambient temperature changes by performing the calibration again as necessary.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a digital modulation signal generator according to the present invention.

FIG. 2 is a configuration diagram showing a connection method of Gilbert type multipliers in the digital modulation signal generator of FIG.

FIG. 3 is a flowchart showing a calibration operation of the digital modulation signal generator of FIG.

FIG. 4 is a configuration diagram showing an embodiment of a conventional digital modulation signal generator.

FIG. 5 is a circuit diagram showing a configuration of a double balance mixer.

FIG. 6 is a circuit diagram showing a configuration of a mixer including a Gilbert-type multiplier.

[Explanation of symbols]

 1 serial-parallel converter 2 digital filter 3 D / A converter 4 low-pass filter 5 local signal source 6 mixer 7, 18, 22 DC bias circuit 8 phaser 9, 20 adder 10 frequency converter 11 level adjuster 12 , 13 demultiplexer 14 band pass filter 15 power detector 16 A / D converter 17 controller 19 switch 21 differential amplifier 23 capacitance 50 local signal leakage level detector 100 local signal 101 I signal 102 Q signal 103 output signal

Claims (1)

[Claims] 1. A digital signal processor for digitally processing a data signal sequence to obtain I-channel and Q-channel signals, and converting the two signals into analog signals, and the in-phase component and quadrature component of a carrier wave in each of these analog signals. A quadrature modulation signal generator for modulating a quadrature to obtain a quadrature modulation wave; A DC bias circuit, an adder for adding the DC bias from the DC bias circuit to the I and Q channel signals, a switch for opening and closing the I and Q channel signals input to the adder, A detector for detecting the leakage of the local signal in the modulated wave, and controlling the DC bias circuit by the output of this detector, Digital modulation signal generator, characterized in that a controller for controlling the serial switch.