JPH10224149A - Signal generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce using times of an expensive phase lock loop circuit (PLL) by deciding the frequency of two orthogonal signals from a reference frequency signal and obtaining an output signal from an orthogonal signal by a local input signal and the output of a phase shifter. SOLUTION: This generator is constituted of a signal source 1, an orthogonal modulator 2, an output signal 3, an I0 signal 4 outputted by an IQ signal generator 10 generating mutually orthogonal two signals, a Q0 signal 5, a phase shifter 6, an I1 signal and an Q1 signal 8 obtained from phase-shifting by the phase shifter 6, a control signal 9 controlling the phase shifter 6, and a reference frequency signal 11. Then the generator 10 decides the frequency of the two orthogonal signals by the signal 11 to output. In addition, the phase shifter 6 shifts the phase relation between the two orthogonal signals by the signal 9. In addition, the orthogonal demodulator 2 obtains an output signal from the two orthogonal signals 7 and 8 by the local input signal and the output of the phase shifter 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal generator used for a local signal source for transmission / reception for performing channel switching at a specific frequency step, which is used in mobile communication and the like.

[0002]

2. Description of the Related Art A phase locked loop circuit (Phase Locked L) having a variable step frequency smaller than a desired output frequency.
oop (hereinafter, abbreviated as PLL)).
Since the frequency of the comparison frequency signal is a variable step frequency, the frequency division number for dividing the output frequency to the comparison frequency becomes large, and the deterioration of signal purity such as generation of jitter and spurious becomes remarkable.

To prevent this, a technique of obtaining a desired frequency range and frequency resolution from two signal sources having different frequency steps is often used. The prior art in this case will be described with reference to FIGS. FIG. 6 is a block diagram of a signal generator for obtaining a desired frequency range and frequency resolution from two signal sources having different frequency steps.

The output of a first signal source 1a whose frequency can be varied in a first frequency step and the output of a second signal source 4a whose frequency can be varied in a second frequency step are input to a mixer 2a which is a frequency converter. Then, an output signal 3a is obtained as the output. Usually, the frequency step of the second signal source 4a is made smaller than the frequency step of the first signal source 1a, and a desired output is obtained by using the output of the mixer 2a that outputs the sum or difference frequency of the two signal sources. An output signal 3a having a frequency is obtained.

For example, the outputtable frequency of the first signal source is 800 to 900 MHz, and the frequency step is 400 kHz.
And the frequency at which the second signal source can output is 100 to 10
Assuming that the frequency of the output signal 3a is 0.4 MHz and the frequency step is 25 kHz, and the frequency component of the sum of the first signal source and the second signal source among the frequency components of the mixer 2a is obtained, the output signal 3a is obtained. Frequency is 900-1
A signal having a frequency of 0.004 MHz and a frequency resolution of 25 kHz can be obtained. In order to obtain 900.025 MHz with this configuration, the frequency of the first signal source is set to 800 MHz,
The frequency of the second signal source may be 100.025 MHz.

Next, the prior art shown in the block diagram of FIG. 7 will be described. The signal generator shown in the configuration of FIG. 7 is a baseband signal I that is input to the quadrature modulator.
This is a signal generator that can vary a minute frequency by performing a phase rotation operation on the signal 4b and the Q signal 5b. (See JP-A-07-065015)

In the signal generator using the configuration shown in FIG. 7, the frequency range and the frequency resolution are controlled by the low-frequency signal source 9b.
And the phase rotation amount Q for each fAF generated in the phase rotation signal generator 10b.

[0008]

However, in the method according to FIG. 6, the two signal sources having different frequency steps need to be constituted by synthesizers each having a PLL, and the signal obtained as the output of the mixer is required. Is
In addition to a desired frequency component, which is a sum component of the frequencies of the first signal source and the second signal source, a component of a frequency difference between the first signal source and the second signal source, and a first signal source and a second signal source This causes a local leak component, and it is necessary to remove this unnecessary component.

[0009] However, the filter for removing the unnecessary component is required to have extremely sharp characteristics when the frequencies of the first signal source and the second signal source are close or the frequency of the second signal source is low. The output frequency width of the second signal source needs to have a frequency width corresponding to the step frequency of the first signal source.

In the configuration shown in FIG. 7, a digital signal processor (hereinafter abbreviated as DSP) having a high processing speed is required for the phase rotation signal generating section, and the frequency of the low-frequency signal source 9b is determined by the DSP. , The upper limit is suppressed due to the processing speed of the phase rotation signal generation unit. For this reason, with this configuration, a high frequency resolution can be obtained, but a configuration of a frequency step in a variable range over several tens of kHz cannot be performed.

The present invention has been made under such a background, and uses a phase shifter unnecessary for a DSP as a signal generator, and increases the output frequency width of a signal source having a small frequency step. An object of the present invention is to reduce the number of expensive PLLs used by setting the step width to about half.

[0012]

According to a first aspect of the present invention, there is provided a signal generator for obtaining a desired frequency range and frequency resolution from two signal sources having different frequency steps. A quadrature signal generator for determining and outputting a signal frequency, a phase shifter for shifting a phase relationship between the two quadrature signals by a control signal, and two quadrature signals based on a local input signal and an output of the phase shifter And a quadrature modulator for obtaining an output signal from the signal generator.

According to a second aspect of the present invention, in the signal generator according to the first aspect, the phase shifter of the phase shifter includes a first signal of the quadrature signal input to the phase shifter and the first signal. A first signal among the quadrature signals output from the phase shifter is equal, and a second signal among the quadrature signals input to the phase shifter and a second signal among the quadrature signals output from the phase shifter are equal to each other. The state of being equal, the first signal of the input quadrature signal to the phase shifter and the second signal of the output quadrature signal of the phase shifter are equal, and the input quadrature signal input to the phase shifter is A signal generator is provided which switches between a state where the second signal is equal to the first signal among the output quadrature signals of the phase shifter.

According to a third aspect of the present invention, in the signal generator according to the first aspect, the phase shifter of the phase shifter includes a first signal of the quadrature signal input to the phase shifter and the first signal. A first signal among the quadrature signals output from the phase shifter is equal, and a second signal among the quadrature signals input to the phase shifter and a second signal among the quadrature signals output from the phase shifter are equal to each other. The state of being equal, the first signal of the input quadrature signal to the phase shifter and the first signal of the output quadrature signal of the phase shifter are equal, and the input quadrature signal input to the phase shifter is equal. A signal generator characterized by switching between a signal obtained by inverting the phase of the second signal and a state in which the second signal among the quadrature signals output from the phase shifter becomes equal.

According to a fourth aspect of the present invention, in the signal generator according to the first aspect, different output frequencies for the two states of the phase shifter are obtained as the output signal frequency for the local signal frequency. A signal generator is provided.

According to a fifth aspect of the present invention, in the signal generator of the first aspect, the quadrature signal generator does not generate a quadrature output signal, and a frequency of the output signal is the same as a local signal frequency. And a signal generator capable of producing a state capable of outputting the frequency of the signal.

[0017]

FIG. 1 is a block diagram showing the configuration of a first embodiment of a signal generator according to the present invention. In this figure, reference numeral 1 denotes a signal source, 2 denotes a quadrature modulator, 3 denotes an output signal, and 4 and 5 denote I signals for generating two signals orthogonal to each other.
The I0 and Q0 signals output by the Q signal generator 10, 6 is a phase shifter, 7 and 8 are I1 and Q1 signals obtained by shifting the I0 and Q0 by the phase shifter 6, and 9 is the phase shifter 6. A control signal 11 to be controlled is a reference frequency signal.

In FIG. 1, the signal of the signal source 1 input to the quadrature modulator 2 is cos (2πfLt), and the I1 signal 7 output from the phase shifter 6 and input to 2 is I1 = cos (2πfLt).
t), if the Q1 signal 8 is Q1 = sin (2πft) and the output signal 3 output from the quadrature modulator 2 is fout, fout = I1 · cos (2πfLt) −Q1 · sin (2πfLt) = cos ｛2π (FL + f) t｝ formula, and the frequency fL of the signal source 1 which is a local input signal depends on the frequency of the IQ signal input to the quadrature modulator 2.
From this, the frequency of the output signal 3 converted to (fL + f) is obtained.

Next, the phase shifting means of the phase shifter 6 will be described. First, one state of the first phase shift means is a state in which I1 signal = I0 signal and Q1 signal = Q0 signal, and the frequency of the output signal 3 in the above equation is obtained. Substituting the I1 signal = Q0 signal and the Q1 signal = I0 signal, which is another state of the first phase shifting means, into the equation, (I0 signal 4 becomes I0 = cos (2πft), Q0 signal 5 becomes Q0 = sin Fout = Q0πcos (2πfLt) -I0 ・ sin (2πfLt) = sin {2π (f-fL) t} =-sin {2π (fL-f) t} Expression formula The frequency 3 is obtained by converting the frequency of the signal source 1 into (fL-f). In other words, this indicates that the phase shifter of the phase shifter 6 converts the frequency of the output signal 3 from the frequency of the signal source 1 to the sum and difference frequencies by the frequency of the IQ signal.

Similarly, one state of the second phase shifting means of the phase shifter 6 is as follows: I1 signal = I0 signal, Q1 signal = Q0 signal. The frequency is (fL + f) from the frequency of 1 to the frequency of the IQ signal.

Another state of the second phase shifting means of the phase shifter 6, ie, I1 signal = I0 signal, Q1 signal = Q0 bar signal (Q0 bar signal indicates the inverted phase of Q0 signal) is substituted into the equation. Then, (expressed by the Q0 bar signal = -Q0 signal) fout = I0.cos (2.pi.fLt)-(-Q0) .sin (2.pi.fLt) = cos {2.pi. (fL-f) t} Expression Output The frequency 3 is obtained by converting the frequency of the signal source 1 into (fL-f). That is,
This shows that the frequency of the output signal 3 is converted from the frequency of the signal source 1 to the sum and difference frequencies by the frequency of the IQ signal by the second phase shifting means by the phase shifter 6.

As described above, the first and second phase shifting means by the phase shifter 6 indicate that the same frequency conversion result can be obtained by phase shifting only by the difference in the phase shifting means. The means for this frequency conversion is selected from the ease of implementation of the circuit to be implemented.
Next, it will be shown that the frequency of the signal source 1 and the frequency of the output signal 3 are equalized by the IQ signal generator 10.

In the above equation, if the I1 signal has a value of 1 at a fixed level and has a value of 0 when the Q1 signal is not output, then fout = 1 · cos (2πfLt) −0 · sin (2πf)
Lt) = cos (2πfLt), and it can be seen that both the frequency of the signal source 1 and the frequency of the output signal 3 are the same at fL.

Next, from the signal source 1 having the frequency step of Δf1 and the IQ signal having the frequency step of Δf2, the variable width of the IQ signal is reduced to less than Δf1 by the phase shift means, and the output frequency of the output signal 3 is changed. A procedure for generating fL to fH having a frequency step of Δf1 in a frequency step of Δf2 will be described.

In state 1 of the phase shifter 6, the frequency fg of the signal source 1 is equal to the frequency fout of the output signal 3 with respect to the frequency fIQ of the IQ signal, and fout = fg + fIQ. In state 2, fout = fg-fIQ. Suppose that. fIQ
Has a frequency step of Δf2, so that fIQ = R · Δf2
(R is an integer of 0 or more). Required f
out is a frequency having n steps from fL such that fH = fL + Δf1 and Δf1 = n · Δf2. When there is no phase shifter 6, the frequency for all the n steps is f
Although necessary for IQ, the number of steps n can be reduced to about half as described below.

For the sake of simplicity, n is an even number and m = n / 2. Assuming that the frequency of the signal source 1 is fL, and R represented by fIQ = R · Δf2 is 0 to m,
The phase shifter 6 is set to state 1. This gives fout
Can obtain an output frequency of fout = fL + R ・ Δf2 (R is from 0 to m).

Next, assuming that the frequency of the signal source 1 is fH, fIQ
The phase shifter 6 is set to the state 2 when R represented by = R · Δf2 is from 0 to m−1. Thus, fout becomes fo
An output frequency of ut = fH−R · Δf2 (R is from 0 to m−1) can be obtained.

By switching the two states of the phase shifter 6 in this manner, a desired frequency fout can be obtained from the frequency of n steps of fIQ in m steps which are half steps. A specific configuration example of the phase shifter 6 is as shown in the second embodiment of FIG. 2 or the third embodiment of FIG.

The input of the phase shifter 3c of FIG.
And Q0 signal 2c, and outputs are I1 signal 6c and Q1 signal 7c. The I0 signal 1c is connected to the input terminal A of the first switch 4c and the input terminal A of the second switch 5c.
The signal 2c is connected to the input terminal B of the first switch 4c and the input terminal B of the second switch 5c. First switch 4
c, an I1 signal 6c is output from the output terminal C, a Q1 signal 7c is output from the output terminal C of the second switch 5c, and the first switch and the second switch output a switch control signal 8c, respectively.
c.

The two states of the phase shifter 3c are created by connecting the contacts to the next state of the first switch and the second switch by the switch control signal 8c. State 1: a state in which the output terminal C of the first switch is connected to the input terminal A, and the output terminal C of the second switch is connected to the input terminal B. State 2: a state in which the output terminal C of the first switch is connected to the input terminal B, and the output terminal C of the second switch is connected to the input terminal A. By controlling these two states, the phase shifting means of the phase shifter 6 according to the second aspect is obtained.

The input of the phase shifter 3d shown in FIG.
And Q0 signal 2d, and outputs are I1 signal 6d and Q1 signal 7d. The I0 signal 1d is output as an I1 signal 6d, which is an output without being operated inside the phase shifter 3d, and the Q0 signal 2d is input to the input of the inverting amplifier 5d and the input terminal B of the first switch 4d inside the phase shifter 3d. Connected, first
The Q1 signal 7d is output from the output terminal C of the switch 4d,
The first switch 4d is controlled by a switch control signal 8d.

The two states of the phase shifter 3d are created by connecting the contacts to the next state of the switch 1 by the switch control signal 8d. State 1: a state in which the output terminal C of the first switch is connected to the input terminal B State 2: a state in which the output terminal C of the first switch is connected to the input terminal A, by controlling these two states. To obtain the phase shift means of the phase shifter 6 indicated by.

Next, as the desired output frequency,
FIG. 4 is a block diagram showing a specific embodiment using the above-described phase shifter as a component of a signal generator of 900 MHz and a frequency step of 25 kHz. Using this configuration,
A signal generator for generating the above output frequency will be described below. The signal source 1e is 800 to 9 in 400 kHz steps.
A frequency of 00 MHz is output and input to the local input of the quadrature modulator 2e.

The reference frequency signal 13e is 200 kHz which is half of 400 kHz which is a variable step of the signal source 1e.
To occur at a frequency step of 25 kHz,
2 ³ × 3 × 5 × 7 × corresponding to a frequency which is the least common multiple of eight kinds of frequencies of 5 kHz × R (R = 1 to 8)
25 kHz = 21 MHz. This reference frequency signal 1
3e is input to the variable frequency divider 11e, and is set to 25 kHz × R (R = 1 to 8) set by the value of the frequency division data table 12e.
Is output from the variable frequency divider at a frequency of (integer) and input to the IQ signal generator 10e.

The IQ signal generator 10e includes a variable frequency divider 11
The I0 signal 4e and the Q0 signal 5e are output according to the input signal from e, and input to the phase shifter 6e. The phase shifter 6e outputs the I1 signal 7e and the Q1 signal 8e in a state where the input I0 signal 4e and Q0 signal 5e are determined by the control signal 9e, and inputs them to the quadrature modulator 2e. The quadrature modulator 2e outputs an output signal 3e from the input local signal and IQ signal.

Signal source 1 for frequency of output signal 3e
e, the setting of the frequency division data table 12e is as follows: When the frequency of the variable frequency divider output signal is f1, the frequency of the output signal 3e is f2, and the frequency of the signal source 1e is f0, f2 = f0 + f1 or f2 = f0−f1. The frequency of the signal source 1e and the value of the frequency-divided data table 12e are determined so that either of them is satisfied. The switch control signal 9e input to the phase shifter 6e determines that the desired f2 is f0 + f1.
Or, the state of the phase shifter is determined depending on which state of f0-f1 is obtained.

However, the frequency of the output signal 3e is equal to that of the signal source 1e.
In this case, the output of the IQ signal generator 10e outputs only the I0 signal 4e having a fixed level of 1 and does not output the Q0 signal. Thus, by selecting the frequency of the signal source 1e, the frequency-divided data table 12e, and the state setting of the phase shifter 6e and the IQ signal generator 10e with respect to the frequency of the output signal 3e, the desired frequency of the output signal 3e can be obtained. Can be obtained.

As an example of the output frequency, each setting when the frequency of the output signal 3e is 800.0 to 800.425 MHz is shown in FIG. However, the portion indicated by *** in FIG. 5 indicates that the set value is meaningless because the state of the IQ signal generator determines the frequency of the output signal 3e.

The state 1 of the phase shifter 6e corresponds to the above-mentioned f2
= F0 + f1, and state 2 is f2 = f0-f1
It shows the state that becomes. The first state of the IQ signal generator 10e is, as described above, the I0 signal 4 whose amplitude is a fixed level of 1.
e indicates that no Q0 signal 5e is output, and the second state indicates that the I0 signal 4e and the Q0 signal 5e determined by the input frequency from the variable frequency divider 11e are output.

The operation of one embodiment of the present invention has been described in detail with reference to the drawings. However, the present invention is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. The present invention is also included in the present invention.

[0041]

As described above, according to the present invention, the variable step frequency of the signal source 1 can be set higher than the frequency resolution.
In the LL loop, the effect that the loop gain can be increased and the signal purity can be improved can be obtained.

Further, since the variable width of the frequency of the IQ signal can be reduced to about half by the phase shifter 6, the IQ signal generator does not need to be constituted by the PLL, and only the frequency dividing operation as in the embodiment is performed. Can be configured. As a result, if the signal source 1 and the reference frequency signal 11 are in a synchronous relationship, an effect is obtained that the signal source 1 and the reference frequency signal 11 can be used as a synthesizer.

It is also possible to obtain a frequency with a larger step than the signal generator based on the IQ phase rotation in the prior art, and
The effect that expensive parts such as SP are not required is also obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a first embodiment of a signal generator according to the present invention.

FIG. 2 is a block diagram showing a configuration of a phase shifter part of a signal generator according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a phase shifter part of a third embodiment of the signal generator according to the present invention.

FIG. 4 is a block diagram showing a configuration of a specific embodiment of a signal generator according to the present invention.

FIG. 5 is a diagram showing output signal frequencies and set values of respective units in a specific embodiment of the signal generator according to the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional signal generator using two signal sources.

FIG. 7 is a block diagram illustrating a configuration of a conventional signal generator that performs minute frequency variation.

[Explanation of symbols]

 Reference Signs List 1 signal source 2 quadrature modulator 3 output signal 4 I0 signal 5 Q0 signal 6 phase shifter 7 I1 signal 8 Q1 signal 9 control signal 10 IQ signal generator 11 reference frequency signal 1a first signal source 2a mixer 3a output signal 4a 2 signal source 1b local signal source 2b quadrature modulator 3b output signal 4b I signal 5b Q signal 7b I 'signal 8b Q' signal 9b low frequency signal source 10b phase rotation signal generator 1c I0 signal 2c Q0 signal 3c phase shifter 4c First switch 5c second switch 6c I1 signal 7c Q1 signal 8c switch control signal 1d I0 signal 2d Q0 signal 3d phase shifter 4d first switch 5d inverting amplifier 6d I1 signal 7d Q1 signal 8d switch control signal 1e signal source 2e quadrature modulation Unit 3e Output signal 4e I0 signal 5e Q0 signal 6e Phase shifter 7e I1 signal 8e Q1 signal 9e Control No. 10e IQ signal generator 11e variable frequency divider 12e division data table 13e reference frequency signal

Claims (5)

[Claims] 1. A signal generator for obtaining a desired frequency range and frequency resolution from two signal sources having different frequency steps, wherein a frequency of two orthogonal signals is determined based on a reference frequency signal and output. A phase shifter that shifts a phase relationship between the two orthogonal signals by a control signal; and a quadrature modulator that obtains an output signal from two orthogonal signals based on a local input signal and an output of the phase shifter. A signal generator, characterized in that: 2. The phase shifter of the phase shifter in the signal generator according to claim 1, wherein: a first signal of the input quadrature signals to the phase shifter and an output quadrature signal of the phase shifter. And the second signal of the quadrature signals input to the phase shifter and the second signal of the quadrature signal output from the phase shifter are equal to each other. The first signal of the input quadrature signal to the phase shifter is equal to the second signal of the output quadrature signal of the phase shifter, and the second signal of the input quadrature signal to the phase shifter is equal to the second signal. A state in which first signals among the output quadrature signals of the phase shifter are equal to each other. 3. The phase shifter of the phase shifter in the signal generator according to claim 1, wherein: a first signal of the input quadrature signals to the phase shifter and an output quadrature signal of the phase shifter. And the second signal of the quadrature signals input to the phase shifter and the second signal of the quadrature signal output from the phase shifter are equal to each other. A first signal of the input quadrature signal to the phase shifter is equal to a first signal of the output quadrature signal of the phase shifter, and a second signal of the input quadrature signal to the phase shifter is The second of the phase-inverted signal and the quadrature signal output from the phase shifter
A signal generator for switching between a state in which the signals are equal and a state in which the signals are equal. 4. The signal generator according to claim 1, wherein different output frequencies for the two states of the phase shifter are obtained as the output signal frequency for the local signal frequency. . 5. The signal generator according to claim 1, wherein the quadrature signal generator does not generate a quadrature output signal, and the output signal can output the same frequency as the local signal frequency. Making a signal generator.