JPH06326738A - Digital modulator - Google Patents

Abstract

PURPOSE:To realize the modulator with a low loss by which digital modulation is executed without using a circulator and a 90 deg. hybrid circuit by which cause the factor of an increase in insertion loss. CONSTITUTION:A input-side 4-branch switch circuit 1 and an output-side 4-branch switch circuit 6 are operated based on an switching signal outputted from a matrix circuit 7 to pass a RF carrier signal through either one of a 0 deg. phase shifter 2 or a 90 deg. phase shifter 3, a 180 deg. phase shifter 4, or a 270 deg. phase shifter 5 thereby applying QPSK modulation to the RF carrier signal. A modulated wave signal obtained by the modulation is outputted. Thus, digital modulation is executed without using a circulator and a 90 deg. hybrid circuit by which cause the factor of an increase in insertion loss.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital modulator used in a 42 GHz high-definition digital FPU or the like, and particularly to a digital modulator which drives a switching element by a digital signal and selects a path having different amplitude and phase to obtain a modulated wave. Regarding modulators.

SUMMARY OF THE INVENTION The present invention relates to a digital modulator for obtaining a digitally modulated wave with low loss. An N-branch switch circuit is provided on the input / output side of the digital modulator, depending on the state of a digital signal. By selecting one branch path of each N-branch switch circuit, an RF signal having an amplitude and phase set for each branch path is formed, thereby obtaining a low-loss digital modulated wave. is there.

[0003]

2. Description of the Related Art Conventionally, various modulators of various modulation systems have been developed, and some of them have already been put into practical use. Similarly, in the 4-phase phase modulation method (QPSK modulation method), the digital modulators shown in FIGS. 3 and 4 have been developed and put into practical use.

The digital modulator shown in FIG. 3 has an input / output terminal 1
RF carrier signal input to 02a (input terminal 10
1. The circulator 102 that takes in the RF carrier signal input to the signal No. 1 and outputs it from the input / output terminal 102b, and also takes in the modulated wave signal input to this input / output terminal 102b and outputs it from the input / output terminal 102c; The RF carrier signal output from the input / output terminal 102b is taken in and a matrix circuit (not shown) of the two path lengths is taken.
A reflection type two-phase PSK modulator 1 which selects a path length based on a switching signal output from the RF carrier signal, performs two-phase PSK modulation on the RF carrier signal, and returns to the input / output terminal 102b.
03 and the modulated wave signal from the circulator 102 input to the input / output terminal 104a and output from the input / output terminal 104b.
Input / output terminal 10 by capturing the modulated wave signal input to b
4c, and a circulator 104 to be output from an output terminal 106 to a circuit (not shown) in the next stage, and a modulated wave signal output from the input / output terminal 104b of the circulator 104. A reflection type two-phase PSK modulator 105 which selects a path length based on a switching signal output from the matrix circuit to perform two-phase PSK modulation of the modulated wave signal and returns the modulated wave signal to the input / output terminal 104b. There is.

Each reflection type two-phase PSK is based on each switching signal output from the matrix circuit.
By operating the modulators 103 and 105, two-phase PSK modulation is performed twice on the RF carrier signal input to the input terminal 101 to perform QPSK modulation, and the modulated wave signal obtained by this modulation operation is output terminal 106. Output from.

Further, the digital modulator shown in FIG. 4 takes in a distributor 112 which divides an RF carrier signal inputted through an input terminal 111 into two, and one RF carrier signal outputted from the distributor 112. In addition, a two-phase PSK modulator 113 that performs two-phase PSK modulation of the RF carrier signal based on a switching signal output from a matrix circuit (not shown), and the other RF carrier signal output from the distributor 112. Of the RF carrier signal based on the switching signal output from the matrix circuit.
The two-phase PSK modulator 114 for performing the phase PSK modulation and the modulated wave signals output from each of the two-phase PSK modulators 113 and 114 are combined by shifting by 90 degrees, and are combined from the output terminal 116 to the next stage circuit (not shown). 90 degree hybrid circuit 115 which outputs to (1).

Then, the distributor 112 inputs the input terminal 1
After dividing the RF carrier signal input to 11 into two, each two-phase PSK modulator 113, 114 is operated based on the switching signal output from the matrix circuit to perform each two-phase PSK modulation, and 90 degree hybrid circuit 115 shifts by 90 degrees to synthesize,
Output terminal 1 of the modulated wave signal obtained by this combining operation
Output from 16.

[0008]

By the way, in the case of considering the digital modulation, if the modulation is performed at the final stage of the transmission system, the deterioration of the modulated wave characteristic due to the frequency conversion can be reduced, and the transmission power due to the reduction of the back-off can be reduced. Can be used efficiently.

However, in such a modulation method,
Modulation with low loss is essential because it requires modulation in high power stages.

From this point of view, the digital modulator shown in FIG. 3 has an insertion loss of each circulator 102, 104, and the digital modulator shown in FIG. 4 has a combined loss (principle) in the 90-degree hybrid circuit 115. Specifically, 3
Therefore, when these digital modulators are used as modulators in the high power stage, there is a problem that the insertion loss in the high power stage portion becomes large.

In view of the above-mentioned circumstances, the present invention can perform digital modulation without using a circulator or a 90-degree hybrid circuit, which causes an increase in insertion loss, and thus can achieve the conventional 4 dB or less. Realized a low-loss modulator that can reduce the insertion loss to 3 dB or less, and enabled modulation at the final stage of the transmission system,
An object of the present invention is to provide a digital modulator that can reduce deterioration of modulated wave characteristics due to frequency conversion and can efficiently use transmission power by reducing backoff.

[0012]

To achieve the above object, the present invention provides a digital modulator that modulates an input RF carrier signal based on an input digital signal to generate a digital modulated wave signal. In, an input having an N-branch path for receiving the input RF carrier signal and selecting one of the N-branch paths based on the input switching signal to output the RF carrier signal A side N branch switch circuit and N transmission paths having phase and amplitude characteristics respectively corresponding to the branch paths of the input side N branch switch circuit, and among the branch paths of the input side N branch switch circuit. , A modulated wave signal is generated by giving phase and amplitude characteristics to the RF carrier signal through a transmission path corresponding to a branch path that outputs the RF carrier signal. It has a transmission path group and N branch paths, and selects one of these N branch paths corresponding to the selected branch path of the input side N branch switch circuit based on the input switching signal. An output-side N-branch switch circuit that takes in the modulated wave signal output from the transmission path group via this branch path and outputs it to the outside is provided.

[0013]

In the above structure, the RF carrier signal input by the input side N branch switch circuit is taken in, and one of the N branch paths is selected based on the input switching signal to select the RF signal.
A carrier signal is output, and among the respective branch paths of the input side N branch switch circuit of the transmission path group, the R is selected by the transmission path corresponding to the branch path that outputs the RF carrier signal.
A phase and amplitude characteristic is given to the F carrier signal to generate a modulated wave signal, which corresponds to the selected branch path of the input side N branch switch circuit based on the switching signal input by the output side N branch switch circuit. 1
One of the branch paths is selected, and the modulated wave signal output from the transmission path group is taken in through the branch path and output to the outside.

[0014]

1 is a block diagram showing an embodiment of a digital modulator according to the present invention.

The digital modulator shown in this figure includes an input side 4-branch switch circuit 1, a 0-degree phase shifter 2, and a 90-degree phase shifter 3.
And a 180-degree phase shifter 4, a 270-degree phase shifter 5, an output side 4-branch switch circuit 6, and a matrix circuit 7. The input side is based on a switching signal output from the matrix circuit 7. The 4-branch switch circuit 1 and the output 4-branch switch circuit 6 are operated to move the RF carrier signal to 0 degree phase shifter 2 or 90 degree phase shifter 3, 180 degree phase shifter 4, 270 degree phase shifter 5 Of the RF carrier signal to be QPSK-modulated and the modulated wave signal obtained by this modulation operation is output.

The input side 4-branch switch circuit 1 has four T-branch waveguide circuits 8 in which straight pipe sections are cascade-connected at appropriate intervals.
And the T of the final stage of each of these T-branch waveguide circuits 8.
A short plunger 9 for short-circuiting a preset position of a straight pipe portion of the branch waveguide circuit 8 and a branch waveguide of each of the T branch waveguide circuits 8 provided from the matrix circuit 7. Four switching elements 10 that bring each of the branch waveguides into either a short-circuited state or a passing state based on the switching signal output, and based on the switching signal output from the matrix circuit 7. Any one of the switching elements 10 to pass, and the remaining switching elements 1
0 is short-circuited, and the RF carrier signal input to the straight tube portion of the T-branch waveguide circuit 8 arranged at the input stage is output from the branch waveguide in which the switching element 10 in the passing state is arranged. , 0 degree phase shifter 2 or 90 degree phase shifter 3, 180 degree phase shifter 4, 1 of 270 degree phase shifter 5
Supply to one.

In this case, each T-branch waveguide circuit 8 is short-circuited by the switching element 10 to bring it into a reflective state due to the general property of a three-terminal circuit. The wave tube circuit 8 can be equivalently equivalent to a straight tube.

In the input-side four-branch switch circuit 1, one terminal of each straight tube forming each T-branch waveguide circuit 8 is used as an input terminal and the other terminal is used as an output terminal, and each branch waveguide is appropriately connected. Since the switching element 10 is arranged at such a position and the output terminal of the straight tube which constitutes the final stage T-branch waveguide circuit 8 is short-circuited by the short plunger 9, Of these, when the switching elements arranged in the three T-branch waveguide circuits 8 are short-circuited and the switching elements 10 arranged in the remaining T-branch waveguide circuits 8 are in the open state, the first-stage T It is possible to realize low-loss transmission from the input terminal of the straight pipe forming the branch waveguide circuit 8 to the end portion of the branch waveguide forming the T-branch waveguide circuit 8 in the open state.

Further, one terminal of the 0-degree phase shifter 2 is connected to the terminal of the branch waveguide which constitutes the first-stage (first-stage) T-branch waveguide circuit 8. When the RF carrier signal is output from the device, the RF carrier signal is taken in, then output from the other terminal and supplied to the output side 4-branch switch circuit 6.

Further, one terminal of the 90-degree phase shifter 3 is connected to the terminal of the branch waveguide which constitutes the T-branch waveguide circuit 8 of the second stage, and the RF waveguide carries the RF carrier from the branch waveguide. When a signal is output, it is taken in, phase-shifted by 90 degrees, then output from the other terminal and supplied to the output side four-branch switch circuit 6.

The 180-degree phase shifter 4 has one terminal of 3 terminals.
It is connected to the terminal of the branch waveguide which constitutes the T-branch waveguide circuit 8 of the stage, and when an RF carrier signal is output from the branch waveguide, it is taken in and
After the phase is shifted by 0 degree, it is output from the other terminal and supplied to the output side four-branch switch circuit 6.

The 270-degree phase shifter 5 has one terminal of 4
It is connected to a terminal of a branch waveguide which constitutes the T-branch waveguide circuit 8 of the stage, and when an RF carrier signal is output from the branch waveguide, the RF carrier signal is taken in and 27
After the phase is shifted by 0 degree, it is output from the other terminal and supplied to the output side four-branch switch circuit 6.

In the output side four-branch switch circuit 6, the straight pipe portions are cascade-connected at appropriate intervals, and the terminals of each branch waveguide are the 0 ° phase shifter 2, 90 ° phase shifter 3, 180 °. Four T-branch waveguide circuits 11 each connected to the other terminals of the phase shifters 4 and 270 degree phase shifter 5, and the first-stage T-branch waveguide of these T-branch waveguide circuits 11 A short plunger 12 for shorting a preset position of a straight pipe portion of the circuit 11 and each of the T-branch waveguide circuits 11
And four switching elements 13 which are provided in the branch waveguides and which bring each of the branch waveguides into either a short state or a passing state based on the switching signal output from the matrix circuit 7. Based on the switching signal output from the matrix circuit 7, one of the switching elements 13 is set in a passing state, the remaining switching elements 13 are set in a short state, and the T-branch waveguide arranged in the final stage. The straight wave portion of the circuit 11 outputs a modulated wave signal that has been QPSK modulated.

In this case, when each T-branch waveguide circuit 11 is short-circuited by the switching element 13 to be in a reflective state due to the general property of the three-terminal circuit, like each T-branch waveguide circuit 8, The T-branch waveguide circuit 11 in which the branch waveguide is short-circuited can be equivalently equivalent to a straight pipe.

In the output side four-branch switch circuit 6, one terminal of each straight tube forming each T-branch waveguide circuit 11 is used as an input terminal, and the other terminal is used as an output terminal, and each branch waveguide is appropriately connected. Since the switching element 13 is arranged at such a position and the input terminal of the straight pipe forming the first stage T-branch waveguide circuit 11 is short-circuited by the short plunger 12, Switching element 1 arranged in three T-branch waveguide circuits 11
When 3 is short-circuited and the switching element 13 arranged in the remaining T-branch waveguide circuit 11 is opened, the end of the branch waveguide that constitutes the T-branch waveguide circuit 11 in the open state It is possible to realize low-loss transmission from the output section to the output terminal of the straight tube which constitutes the final stage T-branch waveguide circuit 11.

Further, when a digital signal is input, the matrix circuit 7 outputs 0 based on this digital signal.
Degree phase shifter 2, 90 degree phase shifter 3, 180 degree phase shifter 4, 27
A switching signal necessary for selecting each branch path formed by the 0-degree phase shifter 5 is generated, and the switching signal is generated by each switching element 10 constituting the input side four branch switch circuit 1 and the output side four branch. It supplies to each switching element 13 which comprises the switch circuit 6, and each of these each of the switching elements 10 and 13 is set to one of each pair.
One open state and the other pair shorted.

As a result, of the T-branch waveguide circuits 8 constituting the input-side 4-branch switch circuit 1 and the T-branch waveguide circuits 11 constituting the output-side 4-branch switch circuit 6 by the matrix circuit 7. , Each switching element 1 provided in each first-stage T-branch waveguide circuit 8, 11
0 and 13 are opened, and the switching elements 10 and 1 provided in the remaining T-branch waveguide circuits 8 and 11, respectively.
When 3 is short-circuited and the branch path including the 0-degree phase shifter 2 is selected, the RF carrier signal input to the input 4-branch switch circuit 1 is held in a certain phase by the 0-degree phase shifter 2. The modulated wave signal thus obtained is output from the output side 4-branch switch circuit 6, and the switching elements 10 and 13 provided in the second-stage T-branch waveguide circuits 8 and 11 are in the open state. And each remaining T
When the switching elements 10 and 11 provided in the branch waveguide circuits 8 and 11 are short-circuited and the branch path including the 90-degree phase shifter 3 is selected, it is input to the input side 4-branch switch circuit 1. The RF carrier signal is phase-shifted by 90 degrees by the 90-degree phase shifter 3 compared with the phase obtained in the path including the 0-degree phase shifter 2, and the modulated wave signal thus obtained is output side 4-branch switch. It is output from the circuit 6.

Similarly, the T-branch waveguide circuit 8 of the third stage,
The switching elements 10 and 13 provided in 11 are opened, the switching elements 10 and 13 provided in the remaining T-branch waveguide circuits 8 and 11 are shorted, and a 180-degree phase shifter is provided. If the branch path including 4 is selected, the RF carrier signal input to the input side 4 branch switch circuit 1 is compared with the phase obtained by the 180 degree phase shifter 4 in the path including the 0 degree phase shifter 2. Phase-shifted by 180 degrees, the modulated wave signal obtained thereby is output from the output side 4-branch switch circuit 6, and each switching element 10 provided in the T-branch waveguide circuits 8 and 11 at the fourth stage, 1
3 is opened, the switching elements 10 and 13 provided in the remaining T-branch waveguide circuits 8 and 11 are short-circuited, and the branch path including the 270-degree phase shifter 5 is selected. , The RF carrier signal input to the input side 4-branch switch circuit 1 is 27 compared to the phase obtained by the 270 degree phase shifter 5 in the path including the 0 degree phase shifter 2.
The phase is shifted by 0 degree, and the modulated wave signal obtained thereby is output from the output side 4-branch switch circuit 6.

As described above, in this embodiment, the input side four-branch switch circuit 1 and the output side four-branch switch circuit 6 are operated based on the switching signal output from the matrix circuit 7 to set the RF carrier signal to 0. Degree phase shifter 2 or 90 degree phase shifter 3, 180 degree phase shifter 4, 270
The RF carrier signal is passed through one of the phase shifters 5 and QPSK modulated, and the modulated wave signal obtained by this modulation operation is output. It is possible to realize a low-loss modulator that can perform digital modulation without using a hybrid circuit or the like, and thereby can reduce the insertion loss to 3 dB or less, which could not be reduced to 4 dB or less in the related art. .

As a result, by using this digital modulator at the final stage of the transmission system, low loss modulation can be achieved at the final stage of the transmission system, and the deterioration of the modulated wave characteristics due to frequency conversion is reduced and the back-off is reduced. It is possible to efficiently use the transmission power due to the reduction.

FIG. 2 is a block diagram showing another embodiment of the digital modulator according to the present invention.

The digital modulator shown in this figure has an input N-branch switch circuit 20, N phase shifters 21, and an output N.
The branch switch circuit 22 and the matrix circuit 23 are provided, and the input side N branch switch circuit 20 is based on the switching signal output from the matrix circuit 23.
And the output-side N-branch switch circuit 22 are operated, and RF
The carrier signal is passed through one of the phase shifters 21 to perform N-phase QPSK modulation on the RF carrier signal, and the modulated wave signal obtained by this modulation operation is output.

The input-side N-branch switch circuit 20 includes N T-branch waveguide circuits whose straight pipe sections are cascade-connected at appropriate intervals, and the last-stage T-branch of these T-branch waveguide circuits. A short plunger that short-circuits a preset position of a straight pipe portion of the waveguide circuit, and a switching signal that is provided in the branch waveguide of each T-branch waveguide circuit and that is output from the matrix circuit. And N switching elements that bring each of the branch waveguides into either a short-circuited state or a passing state, based on the switching signal of each switching element based on the switching signal output from the matrix circuit 23. Either one of them is in the passing state, the remaining switching elements are in the shorting state,
The RF carrier signal input to the straight pipe portion of the T-branch waveguide circuit arranged in the input stage is output from the branch waveguide in which the switching element in the passing state is arranged, and the N phase shifters 21 Supply one of them.

One terminal of each of the N phase shifters 21 is connected to the terminal of the branch waveguide of each T branch waveguide circuit that constitutes the input side N branch switch circuit 20, and When the RF carrier signal is output from the branch waveguide,
This is taken in, and after shifting the phase at a preset phase angle, it is output from the other terminal and supplied to the output side N branch switch circuit 22.

The output side N branch switch circuit 22 has N pieces of straight pipe sections connected in cascade at appropriate intervals, and the terminals of each branch waveguide are respectively connected to the other terminals of the phase shifters 21. Of the T-branch waveguide circuit, a short plunger for making a preset position of a straight pipe portion of the first-stage T-branch waveguide circuit short-circuited among the T-branch waveguide circuits, and N switchings provided on the branch waveguides of the T-branch waveguide circuit to bring each of the branch waveguides into either a short state or a passing state based on a switching signal output from the matrix circuit. And one of the switching elements is set to a pass state based on a switching signal output from the matrix circuit 23, and the remaining switching elements are set to a short state. , And it outputs a modulated wave signal of N-phase PSK modulated from straight pipe portion of the T-branch waveguide circuit disposed at the final stage.

When a digital signal is input, the matrix circuit 23 generates a switching signal necessary for selecting each branch path formed by each phase shifter 21 based on this digital signal, Is supplied to each switching element that constitutes the input-side N-branch switch circuit 20 and each switching element that constitutes the output-side N-branch switch circuit 22. Open one and short the remaining pairs.

As described above, in this embodiment, the input side N-branch switch circuit 20 and the output side N-branch switch circuit 22 are operated based on the switching signal output from the matrix circuit 23 to output the RF carrier signals. Since the RF carrier signal is passed through one of the phase shifters 21 to perform N-phase PSK modulation and the modulated wave signal obtained by this modulation operation is output, the insertion loss is the same as in the above-described embodiment. Digital modulation can be performed without using a circulator or a 90-degree hybrid circuit that causes an increase, which realizes a low-loss modulator and enables modulation at the final stage of the transmission system. This enables efficient use of transmission power by reducing deterioration of modulated wave characteristics due to conversion and reducing backoff.

Further, in each of the above-described embodiments, a plurality of input side four-branch switch circuits 1, output side input four-branch switch circuits 6, input side N-branch switch circuits 20, and output side N-branch switch circuits 22 are provided. T-branch waveguide circuit 8,
Although a circuit configured by 11 and a plurality of switching elements 10 and 13 is used, the SPDT by combining arbitrary circuits instead of such a circuit.
(Single Pole Double Throw) It is possible to use a circuit composed of a switch and not only a waveguide as a transmission line but also an MM.
IC (Monolithic Microwave Integrated Circuit), H
A circuit configured by a planar circuit such as a MIC (Hybrid Microwave Integrated Circuit) or a microstrip line may be used.

The 0-degree phase shifter 2 and the 90-degree phase shifters 3, 1
As for the 80-degree phase shifter 4, the 270-degree phase shifter 5, and each phase shifter 21, similarly, any phase shifter having any configuration may be used.

As the switching elements 10 and 13, any switching element may be used as long as it is a switchable element such as a pin diode, an FET, a HEMT, or a varactor diode.

Further, in each of the above-mentioned embodiments, the 0-degree phase shifter 2, the 90-degree phase shifter 3, the 180-degree phase shifter 4, 270.
The phase shifters 5 and the phase shifters 21 have the same amplitude characteristics, but the 0 degree phase shifter 2 and the 90 degree phase shifter 3,
180 degree phase shifter 4, 270 degree phase shifter 5, attenuator is inserted in each phase shifter 21 in series, and 0 degree phase shifter 2 or 90 degree phase shifter 3, 180 degree by matrix circuit 7, 23 When selecting a branch path including the phase shifter 4, the 270 degree phase shifter 5, and each phase shifter 21, the amplitude may be controlled together with the phase.

[0042]

As described above, according to the present invention, it is possible to perform digital modulation without using a circulator or a 90-degree hybrid circuit which causes an increase in insertion loss. The insertion loss, which could not be achieved, can be reduced to 3 dB or less, and a modulator with low loss is realized for other N-phase PSK modulation systems, enabling modulation at the final stage of the transmission system. ,
This enables efficient use of transmission power by reducing deterioration of modulated wave characteristics due to frequency conversion and reducing backoff.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a digital modulator according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the digital modulator according to the present invention.

FIG. 3 is a block diagram showing an example of a conventionally known QPSK modulation type digital modulator.

FIG. 4 is a block diagram showing another example of a conventionally known QPSK modulation type digital modulator.

[Explanation of symbols]

1 Input side 4 branch switch circuit (input side N branch switch circuit) 20 degree phase shifter (transmission path group) 3 90 degree phase shifter (transmission path group) 4 180 degree phase shifter (transmission path group) 5 270 Degree phase shifter (transmission path group) 6 output side 4 branch switch circuit (output side N branch switch circuit) 7 matrix circuit 8 T branch waveguide circuit (N branch path) 9 short plunger 10 switching element 11 T branch waveguide Tube circuit (N branch path) 12 Short plunger 13 Switching element

Claims (1)

[Claims] 1. A digital modulator for generating a digital modulated wave signal by modulating an input RF carrier signal based on an input digital signal, the digital modulator having an N branch path, An input-side N-branch switch circuit that takes in and outputs one of the N-branch paths based on an input switching signal and outputs the RF carrier signal, and each of the input-side N-branch switch circuits There are N transmission paths having phase and amplitude characteristics respectively corresponding to the branch paths, and among the branch paths of the input side N branch switch circuit, the transmission path corresponding to the branch path that outputs the RF carrier signal is used. It has a group of transmission paths for generating a modulated wave signal by giving phase and amplitude characteristics to the RF carrier signal, and N branch paths. Then, one branch path corresponding to the selected branch path of the input side N branch switch circuit is selected based on the input switching signal, and the modulated wave output from the transmission path group via this branch path. Output side N that takes in the signal and outputs it to the outside
A digital modulator comprising: a branch switch circuit.