JP6864344B2 - Transmitter and signal generation method - Google Patents

Description

The present invention relates to a transmitter and a signal generation method.

Conventionally, a transmitter has been developed that generates a high-frequency transmission signal by converting an intermediate frequency signal obtained by mixing a modulation signal and a locally oscillating signal, which is a carrier signal, with a harmonic frequency mixer, a frequency multiplier, or the like. Has been done. In such a transmitter, when a high frequency transmission signal is generated, an unnecessary signal other than the transmission signal is generated. Removal of unnecessary signals is generally performed using a band-passing waver (for example, Non-Patent Document 1).

K.Katayama, et al., “A 300 GHz CMOS Transmitter With 32-QAM 17.5 Gb / s / ch Capability Over Six Channels”, IEEE Journal of Solid-State Circuits, vol.51, no.12, p. 3037- 3048, Dec. 2016

When a passband filter is used as in Non-Patent Document 1, the passband filter is required to have a steep cutoff frequency characteristic in order to obtain a high-quality signal having a high signal-to-noise ratio. However, in a high frequency band, it is difficult to realize a band passband having a steep cutoff frequency characteristic with low loss.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transmitter and a signal generation method capable of removing unnecessary signals with low loss.

In order to achieve the above object, the transmitter according to the first aspect of the present invention is
A first adder that adds and outputs an input signal having a predetermined frequency band and a local oscillation signal, and
The first multiplication unit that multiplies the output signal of the first addition unit, and
A second adder that adds and outputs a signal having the opposite phase of the input signal and the local oscillation signal, and
A second multiplication unit that multiplies the output signal of the second addition unit, and
A subtraction unit that subtracts the signal multiplied by the second multiplication unit from the signal multiplied by the first multiplication unit and removes an unnecessary wave represented by at least LO ⁿ (n is a natural number).
To be equipped.

Further, the first multiplying portion and the second multiplying portion are
A double multiplier that doubles the input signal is provided.
It may be that.

In addition, the input signal is
An intermediate frequency signal obtained by mixing a baseband signal and the local oscillation signal.
It may be that.

Further, a first amplification unit which is connected to the subsequent stage of the first addition unit, amplifies the output signal of the first addition unit, and inputs the output signal to the first multiplication unit.
It is provided with a second amplification unit which is connected to the subsequent stage of the second addition unit, amplifies the output signal of the second addition unit, and inputs the output signal to the second multiplication unit.
The amplification factor of the first amplification unit is equal to the amplification factor of the second amplification unit.
It may be that.

Further, the signal generation method according to the second aspect of the present invention is described.
The first addition step of adding the local oscillation signal to the input signal having a predetermined frequency band, and
The first multiplication step of multiplying the signal added in the first addition step, and
The second addition step of adding the local oscillation signal to the signal having the opposite phase of the input signal, and
A second multiplication step that multiplies the signal added in the second addition step, and
A subtraction step of subtracting the signal multiplied in the second multiplication step from the signal multiplied in the first multiplication step and removing at least ^{an unnecessary wave represented by LO n} (n is a natural number) .
including.

According to the present invention, unnecessary waves can be removed from the harmonic signal of the mixed signal of the input signal and the locally oscillated signal without using a band-passing waver, so that a low-loss harmonic signal can be generated. it can.

It is a block diagram of the transmitter which concerns on embodiment. It is a block diagram which shows the structure of the frequency mixing part. It is a conceptual diagram which shows the operation of the frequency mixing part. It is a conceptual diagram which shows the output power spectrum of the signal which concerns on the up-conversion of an IF signal. It is a figure which shows an example of the output power spectrum of a transmitter.

Hereinafter, the transmitter according to the embodiment of the present invention will be described with reference to the drawings.

As shown in the block diagram of FIG. 1, the transmitter 1 according to the present embodiment includes a baseband unit 11, a local oscillator 12, a modulation unit 13, a frequency mixing unit 20, a power amplifier 14, and an antenna 15. It is a wireless transmitter equipped with.

The baseband unit 11 outputs the information transmitted from the transmitter 1 to the modulation unit 13 as a baseband signal.

The local oscillator 12 generates a local oscillation signal (hereinafter referred to as LO signal) used as a carrier wave. The local oscillator 12 outputs the LO signal to the modulation unit 13 and the frequency mixing unit 20.

The modulation unit 13 is a mixer that mixes the baseband signal, which is the output signal of the baseband unit 11, and the LO signal, which is the output signal of the local oscillator 12, to generate an intermediate frequency signal (hereinafter referred to as an IF signal). To be equipped. The modulation unit 13 outputs the IF signal to the frequency mixing unit 20.

The frequency mixing unit 20 inputs the IF signal generated by the modulation unit 13 and up-converts the IF signal to generate a transmission signal (hereinafter referred to as an RF signal). The detailed configuration of the frequency mixing unit 20 will be described later.

The power amplifier 14 is a power amplifier that amplifies an RF signal input from the frequency mixing unit 20.

The antenna 15 transmits the output signal of the power amplifier 14 as a radio wave.

Subsequently, the frequency mixing unit 20 according to the present embodiment will be described. As shown in FIG. 2, the frequency mixing unit 20 includes a first addition unit 21, a second addition unit 22, a first amplification unit 23, a second amplification unit 24, a first multiplication unit 25, and a second. A multiplication unit 26 and a subtraction unit 27 are provided.

The first addition unit 21 inputs the IF signal generated by the modulation unit 13 and the LO signal generated by the local oscillator 12, and outputs a signal obtained by adding the IF signal and the LO signal.

The second addition unit 22 includes an anti-phase signal (hereinafter referred to as -IF signal) obtained by inverting the phase of the IF signal generated by the modulation unit 13 by a phase inversion circuit (not shown) and an LO generated by the local oscillator 12. Outputs a signal that is the sum of the signal.

The first amplification unit 23 is a power amplifier that amplifies the output signal of the first addition unit 21. Thereby, the output power of the RF signal can be increased.

The second amplification unit 24 is a power amplifier that amplifies the output signal of the second addition unit 22. Thereby, the output power of the RF signal can be increased. The amplification factor of the signal amplified by the second amplification unit 24 is equal to the amplification factor of the signal amplified by the first amplification unit 23.

The first multiplication unit 25 up-converts the IF signal to generate a high-frequency transmission signal. Specifically, the output signal of the first addition unit 21 including the IF signal is multiplied and output. In the present embodiment, the first multiplier 25 includes a second multiplier that doubles the input signal using a square mixer that is a multiplier, and outputs the signal input from the first adder 21 by doubling the signal. To do.

Similar to the first multiplication unit 25, the second multiplication unit 26 up-converts the input signal to generate a high-frequency transmission signal. Specifically, the output signal of the second addition unit 22 including the −IF signal is multiplied and output. In the present embodiment, the second multiplication unit 26 includes a second multiplier that doubles the input signal using a square mixer that is a multiplier, and outputs the signal input from the second multiplier 22 by doubling. To do.

The subtraction unit 27 includes a subtractor that subtracts the output signal of the second multiplication unit 26 from the output signal of the first multiplication unit 25, and outputs the subtracted signal as an RF signal. In the subtraction unit 27 according to the present embodiment, an RF signal is generated using a balun (balance-unbalanced converter). Specifically, the output signal of the first multiplication unit 25 and the output signal of the second multiplication unit 26 are input to the balun. As a result, the subtraction unit 27 cancels the signal component having the opposite phase to the output signal of the first multiplication unit 25 due to the −IF signal among the output signals of the second multiplication unit 26, and outputs the signal as one signal. can do.

Subsequently, the operation of the frequency mixing unit 20 will be described with reference to the conceptual diagram of FIG.

First, the first addition unit 21 inputs a signal (LO + IF) obtained by adding an IF signal and an LO signal to the first multiplication unit 25. The first multiplication unit 25 multiplies LO + IF. The multiplication of LO + IF is performed by a frequency mixer, that is, a multiplier. ^{More specifically, the signal (LO + IF) n} obtained by multiplying LO + IF by n (n is a natural number) is expressed by the following equation (1).

Regarding the above equation, the signal obtained by up-converting the IF signal, that is, the signal used as the RF signal is the LO ^n-1 · IF signal of the second term on the right side. The signal components of the other items are unnecessary signals. Since the first multiplication unit 25 of the present embodiment doubles the output signal of the first addition unit 21, the calculation represented by the following equation (2) is substantially performed.

FIG. 4 is a conceptual diagram showing the output power spectrum of the signal of each term of the equation (2). In FIG. 4, f _LO is the frequency of the LO signal, and 2f _LO is the frequency of ^{LO 2} squared by the LO signal. As described above, the LO / IF term of the second term on the right side is the desired signal obtained by up-converting the IF signal, and the LO ^{2 term of the first term on the right side and the IF 2} term of the third term on the right side are unnecessary signals. ..

The second addition unit 22 inputs a signal (LO-IF) obtained by adding the −IF signal and the LO signal to the second multiplication unit 26. The second multiplication unit 26 multiplies LO-IF by two in the same manner as the first multiplication unit 25 described above, and outputs a signal represented by the following equation (3).

The subtraction unit 27 subtracts the output signal of the second multiplication unit 26 from the output signal of the first multiplication unit 25. As in the output power spectrum conceptually shown in the above equations (2) and (3) and the block diagram of FIG. 3, the LO ² term and the IF ² term of the output signal of the first multiplication unit 25 are the first. It is equal to ^{the LO 2} term and the IF ² term of the output signal of the 2 multiplication unit 26. Therefore, the output signal of the subtraction unit 27 obtained by subtracting the output signal of the second multiplication unit 26 from the output signal of the first multiplication unit 25 retains the LO · IF term, while the LO ² and IF ² terms which are unnecessary waves. Is the signal that has been removed.

The frequency mixing unit 20 is configured as described above, and can generate high-frequency signals LO / IF by removing unnecessary signals from the IF signal and the LO signal.

FIG. 5 is a diagram showing an example of an output power spectrum when the transmitter 1 according to the present embodiment is configured as a CMOS circuit and a transmission signal having a center frequency of 300 GHz is generated. ^{In FIG. 5, the frequency component of LO 2} , which is an unnecessary wave, is suppressed to a level smaller than that of the noise floor.

As described above, the transmitter 1 according to the present embodiment uses the IF signal which is an input signal, the −IF signal which is the opposite phase of the IF signal, and the LO signal which is a local oscillation signal generated by the local oscillator. It is possible to generate a high frequency output signal (RF signal) from which unnecessary waves are removed. Therefore, it is possible to generate an output signal from which unnecessary signals have been removed with low loss without removing unnecessary waves by a band-passing filter.

In the transmitter 1 according to the above embodiment, as shown in FIG. 1, the same LO signal output from the local oscillator 12 is input to the modulation unit 13 and the frequency mixing unit 20, but the present invention is not limited to this. .. For example, the frequency of the LO signal input to the modulation unit 13 may be different from the frequency of the LO signal input to the frequency mixing unit 20. As a result, the frequency of the IF signal, which is the output of the modulation unit 13, and the frequency of the RF signal, which is the output of the frequency mixing unit 20, can be individually adjusted so as to be suitable for each circuit configuration. ..

Further, the transmitter 1 according to the embodiment has a configuration in which a band-passing filter is not used, but the present invention is not limited to this. For example, a band-passing filter may be arranged between the power amplifier 14 and the antenna 15. As a result, it is possible to transmit a signal with more suppressed noise.

Further, in the transmitter 1 according to the above embodiment, the RF signal is amplified by the power amplifier 14 and then transmitted by the antenna 15, but the present invention is not limited to this. For example, the output signal of the frequency mixing unit 20 may be transmitted from the antenna 15 without using the power amplifier 14. As described above, the transmitter 1 according to the present invention can generate an output signal from which unnecessary signals have been removed with low loss. Therefore, a high-quality transmission signal can be generated even in a high frequency band where it is difficult to apply the power amplifier 14.

The present invention is suitable for wireless transmitters that multiply intermediate frequency signals to generate high frequency transmission signals. Further, the present invention can be applied to a high-frequency wireless transmitter in which the final stage of the transmitter is configured in parallel and a plurality of outputs are power-synthesized.

1 Transmitter, 11 Baseband, 12 Local Oscillator, 13 Modulator, 14 Power Amplifier, 15 Antenna, 20 Frequency Mixer, 21 1st Adder, 22 2nd Adder, 23 1st Amplifier, 24 2nd Amplification part, 25 1st multiplication part, 26 2nd multiplication part, 27 subtraction part

Claims (5)

A first adder that adds and outputs an input signal having a predetermined frequency band and a local oscillation signal, and
The first multiplication unit that multiplies the output signal of the first addition unit, and
A second adder that adds and outputs a signal having the opposite phase of the input signal and the local oscillation signal, and
A second multiplication unit that multiplies the output signal of the second addition unit, and
A subtraction unit that subtracts the signal multiplied by the second multiplication unit from the signal multiplied by the first multiplication unit and removes an unnecessary wave represented by at least LO ⁿ (n is a natural number).
Transmitter equipped with. The first multiplying part and the second multiplying part are
A double multiplier that doubles the input signal is provided.
The transmitter according to claim 1. The input signal is
An intermediate frequency signal obtained by mixing a baseband signal and the local oscillation signal.
The transmitter according to claim 1 or 2. A first amplification unit that is connected to the subsequent stage of the first addition unit, amplifies the output signal of the first addition unit, and inputs the output signal to the first multiplication unit.
It is provided with a second amplification unit which is connected to the subsequent stage of the second addition unit, amplifies the output signal of the second addition unit, and inputs the output signal to the second multiplication unit.
The amplification factor of the first amplification unit is equal to the amplification factor of the second amplification unit.
The transmitter according to any one of claims 1 to 3. The first addition step of adding the local oscillation signal to the input signal having a predetermined frequency band, and
The first multiplication step of multiplying the signal added in the first addition step, and
The second addition step of adding the local oscillation signal to the signal having the opposite phase of the input signal, and
A second multiplication step that multiplies the signal added in the second addition step, and
A subtraction step of subtracting the signal multiplied in the second multiplication step from the signal multiplied in the first multiplication step and removing at least ^{an unnecessary wave represented by LO n} (n is a natural number) .
Signal generation method including.

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