JP2552948B2 - Modulator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a modulator that performs modulation using a quadrature modulator.

[Conventional technology]

FIG. 4 is a block diagram showing a conventional modulator. In the figure, 1 is a voltage-controlled frequency variable oscillator (hereinafter, VC
11), a prescaler 12, a frequency divider circuit 13, a temperature-compensated crystal oscillator (hereinafter referred to as TCXO) 14, and a phase-locked loop (hereinafter referred to as PLL) by a phase comparison circuit 15 and is four times the local carrier wave. Is a frequency generator using a frequency synthesizer for generating a first local oscillation signal having a frequency of.

Similarly, 2 is VCO21, prescaler 22, frequency divider 23, T
It is a frequency generator composed of a CXO 24 and a PLL composed of a phase comparison circuit 25, and a frequency synthesizer for generating a second local oscillation signal. Reference numeral 3 is a waveform generation circuit that generates a baseband signal that modulates the carrier wave. A quadrature modulator 4 quadrature-modulates a local carrier wave based on the first local oscillation signal from the frequency generator 1 with a baseband signal from the waveform generation circuit 3.

In the quadrature modulator 4, reference numeral 41 divides the first local oscillation signal, which is four times the local carrier generated by the frequency generator 1, by four to generate a local carrier having an accurate 90-degree phase difference. This is a phase shift circuit. As described above, in order to generate a local carrier wave having a phase difference of 90 degrees, for example, it is necessary to divide the frequency by 4, and in the frequency generator 1, the phase shift circuit 41 has 4 times.
Since the frequency is divided, it is necessary to previously generate the first local oscillation signal having a frequency four times as high as that of the local carrier. 42 is an analog switch as a modulation circuit that modulates the local carrier waves having a phase difference of 90 degrees generated by this phase shift circuit with the baseband signal generated by the waveform generation circuit 3,
Reference numeral 43 is a low-pass filter (hereinafter referred to as LPF) that extracts a fundamental modulated wave from the output signal of the analog switch 42.

An up-converter 5 mixes the basic modulated wave output from the quadrature modulator 4 with the second local oscillation signal generated by the frequency generator 2 to generate a modulated transmission wave at a predetermined transmission frequency.

Next, the operation will be described. VCO11 of frequency generator 1
Generate a first local oscillator signal having a frequency four times that of the local carrier.

The first local oscillation signal is input to the quadrature modulator 4 and divided by 4 by the phase shift circuit 41, and becomes a local carrier wave having a phase difference of 90 degrees and is input to the analog switch 42. The analog switch 42 modulates the local carrier wave having a phase difference of 90 degrees by the baseband signal generated by the waveform generation circuit 3 and sends it to the LPF 43. The LPF 43 extracts the basic modulated wave from the modulated output from the analog switch 42 and uses it as the output of the quadrature modulator 4.

The basic modulation wave output from the quadrature modulator 4 is sent to the up converter 5, and the up converter 5 mixes the basic modulation wave with the second local oscillation signal output from the frequency generator 2 to obtain a predetermined transmission frequency. Generate and output a modulated wave for transmission.

Note that technical literature similar to such a conventional modulator is, for example, the paper 473 “Experimental Study of Digitized GMSK Modulator” published at the National Conference of the Communications Division of the Institute of Electronics and Communication Engineers in 1980. )and so on.

[Problems to be Solved by the Invention]

Since the conventional modulator is configured as described above,
A first local oscillation signal that is modulated to obtain a transmission modulated wave and a second local oscillation signal that is used to raise the frequency to a predetermined transmission frequency.
2 types of local oscillation signals are required,
Two frequency generators 1 and 2 for generating them
There was a problem that required.

The inventions set forth in claims (1) and (2) have been made to solve the above problems, and are modulations that can obtain a transmission modulation wave at a predetermined transmission frequency with one type of local oscillation signal. The purpose is to obtain the device.

Further, the invention described in claim (3) has an object to obtain a modulator capable of sharing one synthesizer between the transmission system and the reception system.

[Means for solving the problem]

The modulation device according to the invention described in claim (1) is a first frequency dividing circuit for dividing a local oscillation signal by N to generate a local carrier having a phase difference, and a local carrier wave from the first frequency dividing circuit. The modulation circuit that modulates the signal with the signal generated by the waveform generation circuit and the frequency generator with N / (N + 1) times the transmission frequency or N / (N
-1) Generate one kind of local oscillation signal having a doubled frequency, supply it to the first frequency dividing circuit, and mix the local oscillation signal and the fundamental modulation wave from the modulation circuit with an up converter. , A transmission modulated wave having a predetermined transmission frequency is obtained.

A modulator according to a second aspect of the present invention comprises a quadrature modulator, a phase shift circuit which divides a local oscillation signal by N to generate local carriers having a phase difference of 90 degrees, and the phase shift circuit. Consists of a modulation circuit that modulates the local carrier wave from the circuit with the baseband signal generated by the waveform generation circuit, and the frequency generator has a frequency N / (N + 1) or N / (N-1) times the transmission frequency. One kind of local oscillation signal is generated and supplied to the quadrature modulator, and this local oscillation signal and the basic modulation wave from the quadrature modulator are mixed by an up converter, and a transmission modulation wave at a predetermined transmission frequency is generated. Is to get.

In addition, the modulation device according to the invention described in claim (3),
Generate a signal with a frequency that is a natural multiple of the transmission frequency in the frequency generator, divide the signal and divide by N / (N +
1) times or N / (N-1) times the local oscillation signal is generated,
A frequency divider for supplying the quadrature modulator and the up-converter is provided.

[Action]

The modulation device according to the invention described in claim (1) is the first device.
The frequency dividing circuit divides the local oscillation signal N / (N + 1) times or N / (N-1) times the predetermined transmission frequency by N to divide it by 1 / (N + 1) times the transmission frequency with a phase difference. Or 1 / (N-
1) Double local carrier is generated, and the modulating circuit modulates the local carrier with the signal from the waveform generating circuit. Further, the up-converter converts the basic modulated wave from the modulating circuit to N / (N + 1) of the transmission frequency. ) Or N / (N-1) times the local oscillation signal is mixed to realize a modulator that can obtain a transmission modulated wave at a predetermined transmission frequency with only one type of local oscillation signal.

The quadrature modulator in the invention according to claim (2) divides the local oscillation signal of N / (N + 1) times or N / (N-1) times of a predetermined transmission frequency by N and divides it by 90 degrees. A local carrier having a phase difference of 1 / (N + 1) times or 1 / (N-1) times the transmission frequency is generated, and the local carrier is modulated by the baseband signal from the waveform generation circuit. Is the fundamental modulated wave from this quadrature modulator
By mixing with N / (N + 1) times or N / (N-1) times the local oscillation signal, it is possible to realize a modulator that can obtain a transmission modulated wave at a predetermined transmission frequency with only one type of local oscillation signal.

Further, the second frequency divider in the invention according to claim (3) divides the signal generated by the frequency generator to N / (N + 1) times or N / (N-1) times the predetermined transmission frequency. By generating the doubled local oscillation signal and supplying it to the quadrature modulator and the up-converter, it is possible to realize a modulation device in which one synthesizer can be shared by the transmission system and the reception system.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. First
The figure is a block diagram showing an embodiment of the invention described in claims (1) and (2). In the figure, 3 is a waveform generation circuit, 4 is a quadrature modulator, 41 is a phase shift circuit (first frequency dividing circuit),
42 is an analog switch as a modulation circuit, 43 is an LPF, 5
Is an up-converter, which is the same as or equivalent to those of the conventional one denoted by the same reference numeral in FIG. 4, and therefore detailed description thereof will be omitted.

The phase shift circuit 41 and the phase shift circuit 44 shown in FIGS. 2 and 3 described later divide the frequency of the input local oscillation signal and output local carriers having a phase shift difference of 90 degrees. However, of the phase shift circuits 41 and 44, a portion having a function of converting the frequency of the local oscillation signal by dividing the frequency of the input local oscillation signal is referred to as a first frequency dividing circuit.

Further, 6 is a VCO 61, a prescaler 62, a frequency dividing circuit 63, a TCX.
A frequency generator using a frequency synthesizer, which is composed of a PLL including an O64 and a phase comparison circuit 65 and generates a local oscillation signal that is 4/5 times the transmission frequency.

Next, the operation will be described. VCO61 of frequency generator 6
First, a local oscillation signal having a frequency that is 4/5 times the transmission frequency is generated.

This local oscillation signal is input to the quadrature modulator 4 and divided by 4 by the phase shift circuit 41, and becomes a local carrier wave having a phase shift difference of 90 degrees with the frequency being 1/5 times the transmission frequency, and becomes an analog switch. Entered in 42. This is the analog switch 42
A local carrier having a transmission frequency of 1/5 times having a phase shift difference of 90 degrees is modulated by the baseband signal generated by the waveform generation circuit 3 and sent to the LPF 43. The LPF 43 extracts the basic modulated wave from the modulated output from the analog switch 42 and uses it as the output of the quadrature modulator 4.

The basic modulated wave based on the frequency of 1/5 times the transmission frequency output from the quadrature modulator 4 is sent to the up converter 5, and the up converter 5 outputs the basic modulated wave and the transmission frequency output from the frequency generator 6. A 4/5 times local oscillation signal is mixed to generate and output a transmission modulation wave having the same frequency as a predetermined transmission frequency.

In the above embodiment, the case where the frequency is divided by 4 has been described, but the frequency may be divided by N in general. FIG. 2 is a block diagram showing such an embodiment, and in order to avoid redundant explanation, the same parts are assigned the same reference numerals as those in FIG.

In the figure, 7 is a VCO 71, a prescaler 72, a frequency dividing circuit 7
3, a TCXO74, and a PLL composed of a phase comparison circuit 75, and a frequency generated by a frequency synthesizer that generates a local oscillation signal that is N / (N + 1) times the transmission frequency (where N is an even integer of 2 or more). It is a generator.

44 is N / of the transmission frequency generated by this frequency generator 7.
A phase shift circuit that divides the (N + 1) -fold local oscillation signal by N to generate local carrier waves having a frequency of 1 / (N + 1) times the transmission frequency and a highly accurate 90-degree phase difference (first Frequency divider circuit). The quadrature modulator 4 is different from that shown in FIG. 1 in that the phase shift circuit 41 is provided with the phase shift circuit 44.

Next, the operation will be described. VCO 71 of frequency generator 7
First, a local oscillation signal having a frequency N / (N + 1) times the transmission frequency is generated.

This local oscillation signal is input to the quadrature modulator 4 and divided by N in the phase shift circuit 44, and the frequency is 1 / (N of the transmission frequency.
It becomes a local carrier wave having a phase difference of 90 degrees with each other by +1) times and is input to the analog switch 42. Analog switch
42 is 1 / (N + of the transmission frequency with a phase difference of 90 degrees)
1) The doubled local carrier wave is modulated by the baseband signal generated by the waveform generation circuit 3 and sent to the LPF 43. The LPF 43 extracts the basic modulated wave from the modulated output from the analog switch 42 and uses it as the output of the quadrature modulator 4.

1 / (N + of the transmission frequency output from the quadrature modulator 4
1) Upconverter 5 is the fundamental modulated wave with double frequency
The up-converter 5 mixes the basic modulated wave and the local oscillation signal output from the frequency generator 7 by N / (N + 1) times the transmission frequency, and the transmission modulation is performed at the same frequency as the predetermined transmission frequency. Output waves.

In the above embodiment, the frequency generator 6 is the PLL VCO 71.
Although a local oscillation signal that is N / (N + 1) times the transmission frequency is generated from, the PLL VCO 61 shows
A local oscillation signal of (N-1) times (where N is an even number of positive integers of 4 or more) may be generated, and the same effect as that of the above embodiment is obtained. In this case, the quadrature modulator 4 outputs a fundamental modulated wave of 1 / (N-1) times the transmission frequency,
The up-converter 5 sets it to N / (N-1) of the transmission frequency.
It mixes with the doubled local oscillation signal and outputs a transmission modulation wave having the same frequency as the predetermined transmission frequency.

In the embodiment shown in FIGS. 1 and 2, 90
In order to generate a local carrier wave having a phase difference of 10 degrees, the frequency generator 6 having a multiple of the transmission frequency and the first frequency dividing circuits 41 and 44 for dividing the frequency by N were used. In order to generate a local carrier wave having a phase difference, it is necessary to set the frequency of the local oscillation signal to, for example, 1/2 or 1/4, as described in JP-A-63-304559. As described above, in order to reduce the frequency of the local oscillation signal to 1/2 or 1/4, the first frequency dividing circuit for dividing by 2 or the first frequency dividing circuit for dividing by 4 is required. The local carrier generated by the divide-by-1 circuit has a frequency of 1/2 or 1/4.

Therefore, in order for the wave generated by using the first frequency divider circuit to wait for the phase difference of 90 degrees and to be the local carrier wave of the frequency f '(the frequency of the local carrier wave is temporarily f'), the local oscillation is required. The frequency of the signal must already have a frequency of 2f 'or 4f'. In the above example, it was explained as 1/2 or 1/4, but it can be considered in the same way even if it is 1 / N.
First frequency dividing circuits 41 and 44 for frequency division by N and a frequency generator 6 having a frequency N times as high as the local carrier frequency f'are required.

FIG. 3 is a block diagram showing an embodiment of the invention described in claim (3), and the same parts as those in FIG. 2 are designated by the same reference numerals to avoid redundant description. In the figure, 8 is composed of a VCO 81, a prescaler 82, a frequency dividing circuit 83, a TCXO 84, and a PLL by a phase comparison circuit 85, which is a natural number times the transmission frequency,
For example, it is a frequency generator using a frequency synthesizer that generates a doubled signal. 9 is a frequency divider for dividing the signal generated by the frequency generator 8 to generate a local oscillation signal of N / (N-1) times the transmission frequency (where N is an even integer of 4 or more). (Second frequency divider circuit).

The frequency divider 9 divides the input local oscillation signal. The frequency divider 9 corresponds to the second frequency dividing circuit.

Next, the operation will be described. VCO81 of frequency generator 8
The frequency-divided signal of twice the transmission frequency is generated by the frequency divider 9, and a local oscillation signal having a frequency of N / (N-1) times the transmission frequency is generated.

This local oscillation signal is input to the quadrature modulator 4 and divided by N in the phase shift circuit 44, and the frequency is 1 / (N of the transmission frequency.
It becomes a local carrier wave which waits for a phase difference of 90 degrees from each other by -1) times and is input to the analog switch 42. Analog switch
42 is 1 / (N− of the transmission frequency with a phase difference of 90 degrees.
1) The double carrier wave is modulated by the baseband signal generated by the waveform generation circuit 3 and sent to the LPF 43. The LPF 43 extracts the basic modulated wave from the modulated output from the analog switch 42 and uses it as the output of the quadrature modulator 4.

1 / (N− of the transmission frequency output from the quadrature modulator 4
1) Upconverter 5 is the fundamental modulated wave with double frequency
The up-converter 5 mixes the basic modulated wave with the local oscillation signal output from the frequency divider 9 and having a frequency N / (N-1) times the transmission frequency. Generates and outputs a modulated transmission wave.

Even in this case, the frequency divider 9 may generate a local oscillation signal of N / (N + 1) times the transmission frequency (where N is an even integer of 2 or more). It has the same effect as the example.

〔The invention's effect〕

As described above, according to the inventions described in claims (1) and (2), N / (N + 1) times or N / (N) times the transmission frequency.
-1) frequency-divided local oscillation signal is multiplied by N to generate a carrier having a phase difference, which is modulated with a signal from a waveform generation circuit,
Since the transmission modulated wave is obtained by mixing with the local oscillation signal, it becomes possible to output the transmission modulation wave at a predetermined transmission frequency with only one type of local oscillation signal, and an economical modulator can be obtained. It is effective.

Further, according to the invention as set forth in claim (3), a signal having a natural number times the transmission frequency is generated and divided, and N / (N + 1) times or N / (N-1) times the transmission frequency is generated. Since it is configured to generate twice the local oscillation signal and supply it to the quadrature modulator and the up-converter, one synthesizer can be shared by the transmission system and the reception system, and a more economical modulator can be obtained. It is effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing a modulator according to an embodiment of the invention described in claims (1) and (2), and FIG. 2 is another embodiment of the invention described in claims (1) and (2). FIG. 3 is a block diagram showing an example, FIG. 3 is a block diagram showing an embodiment of the invention described in claim (3), and FIG. 4 is a block diagram showing a conventional modulator. 3 is a waveform generation circuit, 4 is a quadrature modulator, 41 and 44 are phase shift circuits (first frequency dividing circuits), 42 is an analog switch (modulation circuit), 5 is an up converter, 6 to 8 are frequency generators,
9 is a frequency divider (second frequency divider circuit). In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

(57) [Claims] 1. A first frequency dividing circuit for generating a local carrier by dividing a frequency of a local oscillation signal by N, and the first frequency dividing circuit using a baseband signal.
A modulation circuit for modulating the local carrier wave from the frequency dividing circuit,
N / (N + 1) or N / (N-1) times the transmission frequency (where N is 2 or more when N / (N + 1) times, N / (N-1)
A frequency generator that generates the local oscillation signal having a frequency of 3 or more when doubled and supplies the local oscillation signal to the first frequency dividing circuit, a basic modulation wave from the modulation circuit, and the frequency from the frequency generator. An up-converter that mixes a local oscillation signal to obtain a transmission modulation wave. 2. A phase shift circuit that divides a local oscillation signal by N to generate local carriers having a phase difference of 90 degrees, and a modulation circuit that modulates the local carrier from the phase shift circuit with a baseband signal. And a quadrature modulator having a transmission frequency N /
(N + 1) times or N / (N-1) times (where N is N /
When (N + 1) times, an even number of positive integers of 2 or more, N / (N-
1) When multiplied, the local oscillation signal having a frequency of positive integer of 4 or more) is generated and supplied to the phase shift circuit, a fundamental modulation wave from the quadrature modulator, and An up-converter that mixes with the local oscillation signal from a frequency generator to obtain a transmission modulation wave. 3. A phase shift circuit that divides a local oscillation signal by N to generate local carriers having a phase difference of 90 degrees, and a modulation circuit that modulates a local carrier from the phase shift circuit with a baseband signal. A quadrature modulator, a frequency generator that generates a signal that is a natural number times the transmission frequency, and a signal that the frequency generator generates by dividing the frequency by N / (N
+1) times or N / (N-1) times (where N is N / (N +
1) When multiplied, it is an even number of positive integers of 2 or more, and when N / (N-1) times, it is an even number of positive integers of 4 or more). A second frequency dividing circuit for supplying the fundamental modulated wave from the quadrature modulator and the second
An up-converter that mixes the local oscillation signal from the frequency dividing circuit to obtain a transmission modulation wave.