JP2022131330A - Wireless transmitter - Google Patents

Abstract

To provide a wireless transmitter capable of correcting a phase shifter without adding a phase detection element to an antenna output side and without deteriorating an output power.SOLUTION: A wireless transmitter 100 comprises: a multiplexer 3 that adds a signal from a local oscillator to an intermediate frequency signal; a multiplexer 4 that adds the signal from the local oscillator to a reverse-phase signal of the intermediate frequency signal; secondary harmonic frequency mixers 5 and 6 that generate a desired wave and an unwanted wave from outputs of the multiplexers 3 and 4, respectively; an adder/subtracter 7 that performs addition and subtraction to outputs of the secondary harmonic frequency mixers 5 and 6; a power detector 8 that detects a power of the added output of the adder/subtracter 7; and a correction circuit 101 that corrects a shift amount of a first phase shifter or a second phase shifter.SELECTED DRAWING: Figure 1

Description

The present invention relates to radio transmitters.

In a phased array radio transmitter, a signal having a frequency higher than the maximum oscillation frequency of a transistor may be used as a carrier wave. Since a power amplifier cannot be realized at a frequency higher than the maximum oscillation frequency of a transistor, a configuration has been proposed in which an IF signal is amplified at an intermediate frequency (IF) and a square mixer is used to generate a high-frequency transmission signal (RF signal) (Patent document 1, 2). In order to realize a phased array radio transmitter using this configuration, it is necessary to use a phase shifter to change the phase of the local oscillator (LO) signal (hereinafter also referred to as the LO signal). .

The method of changing the phase of the RF signal using a phase shifter cannot be used because the loss of the phase shifter is large. Moreover, the method of changing the phase of the IF signal using a phase shifter is difficult to implement because the phase shifter requires a large fractional bandwidth. On the other hand, the phase shifter for the LO signal is easy to implement because it is sufficient to change the phase of the LO signal only. In this transmitter, it is necessary to simultaneously change the phases of the RF signals generated from the positive-phase IF signal and the negative-phase IF signal, so that the two phase shifters must be corrected. A technique has been proposed in which an RF signal is branched by a branching device, down-converted, the phase is detected by a phase detector, and the phase is adjusted to a desired phase (see Non-Patent Document 1).

JP 2018-125733 A WO2020/110814

Y. Wang et al., "A 39-GHz 64-Element Phased-Array Transceiver With Built-In Phase and Amplitude Calibrations for Large-Array 5G NR in 65-nm CMOS," IEEE Journal of Solid-State Circuits, vol. 55, no. 5: pp. 1249-1269, May 2020.

However, at frequencies above the maximum oscillation frequency of the transistor, the branching device causes power loss, so it is not desirable to insert the branching device on the RF signal side. Moreover, since the frequency of the RF signal is high in the technique of Non-Patent Document 1, the performance required for the down-conversion mixer is high, and it is difficult to realize the technique.

The present invention has been made in view of the above points, and provides a radio transmitter that corrects a phase shifter without adding a phase detection element to the antenna output side and without degrading the output power. intended to

A radio transmitter according to a first aspect of the present invention includes a first phase shifter and a second phase shifter that respectively shift the phase of a signal output by a local oscillator, an output of the first phase shifter, an intermediate frequency a second adder for adding the output of the second phase shifter and the reverse phase signal of the intermediate frequency signal; a desired wave and a desired wave from the output of the first adder; A first mixer that generates an unwanted wave, a second mixer that generates a desired wave and an unwanted wave from the output of the second adder, an output of the first mixer, and an output of the second mixer. an adder/subtractor that performs addition and subtraction of the output of the second mixer from the output of the first mixer; a power detector that detects the power of the addition output in the adder/subtractor; the first phase shifter or the Using the change characteristic of the detected voltage of the power detector obtained by changing the other phase while fixing one phase of the second phase shifter, the first phase shifter or the second phase shifter and a correction circuit for correcting the shift amount.

A radio transmitter according to a second aspect of the present invention is the radio transmitter according to the first aspect, wherein the correction circuit is configured to correct the phase of the first phase shifter while fixing the phase of the second phase shifter. a first change characteristic for at least one cycle of the detected voltage of the power detector obtained by changing the phase, and the phase of the first phase shifter, the phase at which the voltage of the first change characteristic is minimized; and a second change characteristic for at least one cycle of the detected voltage of the power detector obtained by changing the phase of the second phase shifter in a state fixed to the first phase shifter or the Correct the shift amount of the second phase shifter.

A radio transmitter according to a third aspect of the present invention is the radio transmitter according to the second aspect, wherein the correction circuit approximates the first change characteristic and the second change characteristic with functions, The shift amount of the first phase shifter or the second phase shifter is corrected while maintaining equal values of the two functions.

A radio transmitter according to a fourth aspect of the present invention is the radio transmitter according to any one of the first to third aspects, wherein the first mixer performs a predetermined operation on the output of the first adder and the second mixer outputs the result of a predetermined operation on the output of the second adder.

A radio transmitter according to a fifth aspect of the present invention is the radio transmitter according to the fourth aspect, wherein the first mixer squares and outputs the output of the first adder, and the second mixer A unit squares the output of the second adder and outputs the result.

According to the present invention, it is possible to provide a radio transmitter that corrects a phase shifter without adding a phase detection element to the antenna output side and without degrading the output power.

1 is a diagram showing a schematic configuration of a wireless transmitter according to this embodiment; FIG. Fig. 4 is a flow chart illustrating a method of correcting a phase shifter of a wireless transmitter; It is a figure which shows the specific structural example of the radio|wireless transmitter which concerns on this embodiment. 4 is a spectrum diagram of a signal input to a power detector obtained by functional simulation of the radio transmitter according to the present embodiment; FIG. FIG. 4 is a diagram showing detected power in a power detector and results of approximating the detected power with a function; FIG. 10 is a diagram showing a modification of the radio transmitter;

An example of an embodiment of the present disclosure will be described below with reference to the drawings. In each drawing, the same or equivalent components and portions are given the same reference numerals. Also, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

FIG. 1 is a diagram showing a schematic configuration of a radio transmitter according to this embodiment. FIG. 1 also shows an example of the power spectrum at each point.

The radio transmitter 100 according to this embodiment includes phase shifters 1 and 2, multiplexers 3 and 4, second harmonic frequency mixers 5 and 6, an adder/subtractor 7, a power detector 8, a bandpass filter 9, 10, an antenna 11, and a correction circuit 101. FIG.

Phase shifters 1 and 2 change the phase of the signal (LO signal) from the local oscillator. Let v _LO be the voltage of the LO signal. Phase shifter 1 is an example of the first phase shifter of the present invention, and phase shifter 2 is an example of the second phase shifter of the present invention.

A multiplexer 3 combines the LO signal whose phase has been changed by the phase shifter 1 and an intermediate frequency signal (IF signal) and outputs the combined signal. The multiplexer 3 is an example of the first adder of the present invention. Assuming that the voltage of the IF signal is v _IF , the voltage of the output signal of the multiplexer 3 is v _LO +v _IF . The voltage v _IF of the IF signal is v _IF =A _IF ·sinω _IF t. A _IF is the amplitude of the IF signal and ω _IF is the angular frequency of the IF signal.

A multiplexer 4 combines the LO signal whose phase has been changed by the phase shifter 2 and the opposite phase signal of the IF signal, and outputs the combined signal. The multiplexer 4 is an example of the second adder of the present invention. The voltage of the output signal of the multiplexer 4 becomes v _LO -v _IF .

A secondary harmonic frequency mixer 5 squares the output of the multiplexer 3 and outputs the result. The voltage of the output signal of the second harmonic frequency mixer 5 is (v _LO +v _IF ) ² .

A secondary harmonic frequency mixer 6 squares the output of the multiplexer 4 and outputs it. The voltage of the output signal of the second harmonic frequency mixer 6 is (v _LO -v _IF ) ² .

From the second-order harmonic frequency mixers 5 and 6, desired waves v _LO and v _IF are output differentially, and unwanted waves v _LO ² and v _IF ² are output in phase.

The adder/subtractor 7 adds the output of the second harmonic frequency mixer 5 and the output of the second harmonic frequency mixer 6 and outputs the result. The adder/subtractor 7 subtracts the output of the secondary harmonic frequency mixer 6 from the output of the secondary harmonic frequency mixer 5 and outputs the result. The signal after subtraction by the adder/subtractor 7 becomes the transmission signal from the antenna 11 . On the other hand, the signal added by the adder/subtractor 7 is sent to the power detector 8 .

A power detector 8 detects the power of the signal added by the adder/subtractor 7 . A detection result by the power detector 8 is used for correction by the correction circuit 101 of the phase changed by the phase shifters 1 and 2 .

The band-pass filters 9 and 10 are filters that pass signals in a desired frequency band and attenuate signals in bands other than the desired frequency band.

The correction circuit 101 is a circuit that corrects the phases changed by the phase shifters 1 and 2 using the detection result of the power detector 8 . The correction circuit 101 is composed of, for example, a digital circuit.

A phase method for the phase shifters 1 and 2 using the radio transmitter 100 shown in FIG. 1 will be described.

Let the voltage v _LO of the input LO signal be v _LO =A _LO ·sinω _LO t. A _LO is the amplitude of the LO signal and ω _LO is the angular frequency of the LO signal. Let the voltage v _LOp of the LO signal that has passed through the phase shifter 1 be v _LOp =A _LO ·sin(ω _LO t+Δθ). Assume that the voltage v _LOn of the LO signal that has passed through the phase shifter 2 is v _LOn =−A _LO ·sinω _LO t. Δθ is the phase difference between phase shifter 1 and phase shifter 2 .

When the LO signal that has passed through the phase shifter 1 is added to the IF signal in the multiplexer 3, the voltage of the output signal from the multiplexer 3 becomes v _LOp +v _IF . The voltage v _IF of the IF signal is v _IF =A _IF ·sinω _IF t. A _IF is the amplitude of the IF signal and ω _IF is the angular frequency of the IF signal.

When the LO signal that has passed through the phase shifter 2 is added to the opposite phase signal of the IF signal in the combiner 4, the voltage of the output signal from the combiner 4 becomes v _LOn -v _IF .

When the output of the combiner 3 is squared by the second harmonic frequency mixer 5, the voltage of the output signal of the second harmonic frequency mixer 5 becomes (v _LOp +v _IF ) ² . When the output of the multiplexer 4 is squared by the second harmonic frequency mixer 6, the voltage of the output signal of the second harmonic frequency mixer 6 becomes (v _LOn -v _IF ) ² .

A signal obtained by adding the outputs of the two second-order harmonic frequency mixers 5 and 6 by the adder/subtractor 7 is output to the power detector 8 side. The voltage of the addition signal added by the adder/subtractor 7 is v _LOp ² +v _LOn ² +2v _LOp ·v _IF −2v _LOn ·v _IF +v _IF ² . A band-pass filter 9 removes the difference frequency component from this added signal. The voltage of the signal after removal by the band-pass filter 9 is given by the following formula (1).

The power obtained by the power detector 8 is given by the following formula (2).

It can be seen that the output voltage of the power detector 8 changes periodically when Δθ in the above equation (2) is changed. By acquiring this change characteristic for one cycle or more, Δθ can be obtained from the change characteristic. The phase shifters 1 and 2 can be corrected by obtaining Δθ from the variation characteristics.

A correction method for phase shifters 1 and 2 of radio transmitter 100 will be described. FIG. 2 is a flow chart showing a correction method for the phase shifters 1 and 2 of the radio transmitter 100. As shown in FIG.

Radio transmitter 100 fixes the phase of phase shifter 2 on the opposite phase signal side of the IF signal, changes the phase of phase shifter 1 on the IF signal side, and sets the change characteristic of the output voltage of power detector 8 to 1. It acquires more than a period (step S11).

Radio transmitter 100 then fixes the phase of phase shifter 1 on the IF signal side to the phase that minimizes the detected power in the variation characteristics acquired in step S11, and fixes the phase of phase shifter 2 on the opposite phase signal side. The phase is changed, and the change characteristic of the output voltage of the power detector 8 is obtained for one or more cycles (step S12).

The radio transmitter 100 then approximates the change characteristics obtained in steps S11 and S12 with a function (step S13). The radio transmitter 100 approximates the change characteristics obtained in steps S11 and S12 with a function P _d =a·cos2Δθ+b·cos Δθ+c to obtain P _dp and P _dn , respectively. a, b, and c are constants. Δθ is a function of the control voltage of the phase shifters 1,2 and is determined by the characteristics of the phase shifters 1,2. If the control voltage phase characteristics of the phase shifters 1 and 2 are linear, then Δθ=αV _c +β. α, β are constants and Vc is the control voltage of the phase _shifters 1,2.

The wireless transmitter 100 then changes the control voltages of the phase shifters 1 and 2 while keeping the two approximated functions P _dp and P _dn equal (step S14). The wireless transmitter 100 changes the control voltages of the phase shifters 1 and 2 while maintaining the functions P _dp and P _dn equal, thereby controlling the phases of the RF signal and the anti-phase signal to an arbitrary phase. can be done.

Since the radio transmitter 100 according to the present embodiment obtains the phase of the phase shifter using the unwanted wave, there is no need to add a phase detection element to the output side of the antenna 11 of the radio transmitter 100 . Therefore, the wireless transmitter 100 according to this embodiment can control the phases of the RF signal and the anti-phase signal to an arbitrary phase without degrading the output power. In addition, since the radio transmitter 100 according to the present embodiment does not use a down-conversion mixer and obtains the phase only with the power detector 8, it does not require a complicated circuit. Suitable for phasers 1 and 2 correction.

FIG. 3 is a diagram showing a specific configuration example of the wireless transmitter 100 according to this embodiment. The radio transmitter 100 according to the present embodiment includes balanced unbalancers 12, 13, 18, 19, 22 to 25, frequency triplers 14 and 15, LO signal amplifiers 16 and 17, and a 90° hybrid circuit 20. , 21, phase shifters 26-29, baseband amplifiers 30-33, quadrature upconversion mixers 34, 35, IF signal amplifiers 36, 37, square mixers 38, 39, and rat race power combiners. 40 , a power detector 41 and a control circuit 42 .

In the configuration shown in FIG. 3, the left half of the circuit is for generating a positive-phase RF signal, and the right half is for generating an opposite-phase RF signal. The quadrature upconversion mixers 34 and 35 receive the quadrature differential baseband (BB) signal and the quadrature differential LO signal to generate an IF signal. To change the phase of the quadrature differential LO signals, two differential phase shifters are used in the left and right portions of the circuit of FIG.

The LO signal is used by quadrature upconversion mixers 34 and 35 to generate IF signals, and is multiplexed with the IF signals generated by quadrature upconversion mixers 34 and 35 . The square mixers 38, 39 are the second harmonic frequency mixers 5, 6 shown in FIG. Signals output from square mixers 38 and 39 are added and subtracted by rat race power combiner 40 . The signal added by the rat race type power combiner 40 is used for the antenna output, and the power of the subtracted signal is detected by the power detector 41 .

In the radio transmitter 100 according to this embodiment, the phase of the IF signal is also changed by the phase shifters 26-29. The variation characteristic obtained by the power detector 41 may be approximated by a function P _d =a·cos2Δθ+c. a and c are constants. A control circuit 42 is used to control the phase shifters 26 to 29 using the approximation function. The control circuit 42 is an example of the correction circuit of the present invention, and is composed of, for example, a digital circuit.

FIG. 4 is a spectrum diagram of a signal input to the power detector 41 obtained by functional simulation of the wireless transmitter 100 according to this embodiment. The frequency of the BB signal is 1 GHz, the frequency of the LO signal is 135 GHz, and Δθ is 10°. FIG. 5 is a diagram showing the power detected by the power detector 41 when Δθ is varied from −180° to 180°, and the result of approximating the detected power with a function. It can be seen from FIG. 5 that the detected power and the approximation function are in good agreement. Therefore, the wireless transmitter 100 according to the present embodiment can control the phases of the positive-phase RF signal and the negative-phase RF signal to arbitrary phases.

In the above embodiment, the second harmonic frequency mixer is used to generate the desired wave and the unwanted wave, but the present invention is not limited to such an example. The radio transmitter of the present invention may generate desired waves and unwanted waves using a general frequency mixer such as a double balanced mixer.

FIG. 6 is a diagram showing a configuration example of a wireless transmitter 200 according to a modification of this embodiment. The radio transmitter 200 shown in FIG. 6 includes NMOSFETs 201-206 and balance/unbalance devices 207 and 208. 6, illustration of the phase shifters 1 and 2 shown in FIG. 1 is omitted.

NMOSFET 201 multiplies the LO signal passed through phase shifter 1 by the IF signal and outputs the result to balance/unbalance unit 207 . NMOSFET 202 multiplies the LO signal passed through phase shifter 2 by the IF signal and outputs the result to balance/unbalance unit 208 . NMOSFET 203 sends an IF signal to NMOSFETs 201 and 202 .

The NMOSFET 204 multiplies the LO signal passed through the phase shifter 1 by the reversed-phase signal of the IF signal and outputs the result to the balance/unbalance unit 207 . The NMOSFET 205 multiplies the LO signal that has passed through the phase shifter 2 by the opposite phase signal of the IF signal, and outputs the result to the balance/unbalance unit 208 . NMOSFET 206 sends the opposite phase signal of the IF signal to NMOSFETs 204 and 205 .

Balance-unbalancer 207 mixes the signal sent from NMOSFET 201 and the signal sent from NMOSFET 205 . The balance/unbalance device 207 generates a signal transmitted from an antenna (not shown) as a desired wave and an LO leak signal as an unwanted wave. Balance-unbalancer 208 mixes the signal from NMOSFET 202 and the signal from NMOSFET 204 . The balance/unbalance device 208 generates a signal transmitted from an antenna (not shown) as a desired wave and an LO leak signal as an unwanted wave.

Radio transmitter 200 shown in FIG. 6 can correct the phase of the phase shifter similarly to radio transmitter 100 by measuring the power of unwanted waves generated by frequency mixers 207 and 208 . The radio transmitter 200 shown in FIG. 6 does not require the second harmonic frequency mixers 5 and 6 (square mixers 38 and 39) provided in the radio transmitter 100 to correct the phase of the phase shifter. .

1, 2: phase shifters 3, 4: multiplexer 5, 6: second harmonic frequency mixer 7: adder/subtractor 8: power detector 9, 10: bandpass filter 11: antenna 12, 13, 18, 19, 22-25: balanced/unbalanced devices 14, 15: frequency tripler 16, 17: LO signal amplifier 20, 21: 90° hybrid circuit 26-29: phase shifters 30-33: baseband amplifiers 34, 35 : Quadrature up-conversion mixers 36, 37: IF signal amplifiers 38, 39: Square mixer 40: Rat race power combiner 41: Power detector 42: Control circuit 100: Radio transmitter

Claims (5)

a first phase shifter and a second phase shifter for respectively shifting the phase of the signal output by the local oscillator;
a first adder that adds the output of the first phase shifter and an intermediate frequency signal;
a second adder that adds the output of the second phase shifter and the reverse phase signal of the intermediate frequency signal;
a first mixer that generates a desired wave and an unwanted wave from the output of the first adder;
a second mixer that generates a desired wave and an unwanted wave from the output of the second adder;
an adder-subtractor that adds the output of the first mixer and the output of the second mixer, and subtracts the output of the second mixer from the output of the first mixer;
a power detector that detects the power of the added output in the adder/subtractor;
The first phase shifter using the change characteristic of the detection voltage of the power detector obtained by changing the phase of one of the first phase shifter and the second phase shifter while the other phase is fixed. or a correction circuit that corrects the shift amount of the second phase shifter;
a radio transmitter. The correction circuit has a first change characteristic for at least one cycle of the detected voltage of the power detector obtained by changing the phase of the first phase shifter while the phase of the second phase shifter is fixed. and the detection of the power detector obtained by changing the phase of the second phase shifter while fixing the phase of the first phase shifter to the phase that minimizes the voltage of the first change characteristic. 2. The radio transmitter according to claim 1, wherein the shift amount of said first phase shifter or said second phase shifter is corrected using a second change characteristic for at least one cycle of voltage. The correction circuit approximates the first change characteristic and the second change characteristic with functions, and maintains a state where the values of the two functions are equal to the first phase shifter or the second phase shifter. 3. The radio transmitter according to claim 2, wherein the shift amount of is corrected. the first mixer outputs a result of a predetermined operation on the output of the first adder;
The radio transmitter according to any one of claims 1 to 3, wherein said second mixer outputs a result of a predetermined operation on the output of said second adder. The first mixer squares the output of the first adder and outputs the
5. The wireless transmitter of claim 4, wherein the second mixer squares the output of the second adder and outputs the result.

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