JP2003273818A - Apparatus and method for converting frequency - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for converting frequency which has a simple structure and method therefor. <P>SOLUTION: The frequency converter is provided with a noise generator (a white noise generator 9, a spectrum-shaping filter 10 and an attenuator 11) capable of arbitrarily varying a frequency spectrum, and a frequency modulator 13 for applying frequency modulation to a local oscillated signal by a noise generated by means of this noise generator, and adds phase noise to intermediate frequency signal by the local oscillation signal from the modulator 13 and converts the frequency of the intermediate frequency signal. By means of this configuration, in a high-frequency signal transmission system having frequency conversion, arbitrary phase noise can be added and transmitted with a simple structure. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency converter, and more particularly to a frequency converter and method for frequency converting a high frequency signal by a heterodyne method.

[0002]

2. Description of the Related Art In a system for transmitting digital signals,
A method of transmitting information by changing the phase of a high frequency signal is widely used. For example, OFDM
In terrestrial digital broadcasting using (Orthogonal Frequency Division Multiplexing) signals,
A method of transmitting a signal of each carrier using a phase change such as 64QAM, 16QAM, or QPSK is used.

The method of transmitting information by changing the phase is susceptible to so-called phase noise. When an OFDM signal or the like is received by the common reception facility, it is assumed that the OFDM signal is frequency-converted and received. In this case, if the amount of phase noise included in the frequency-converted signal is allowed, it can be reflected in the line design of the entire receiving equipment.

On the other hand, the heterodyne system is widely used as a system for converting the frequency of a high frequency signal. This heterodyne system requires a sinusoidal local oscillator signal. Since this local oscillation signal also contains phase noise, the phase noise is added to the signal after frequency conversion when received by the joint reception facility.

Therefore, in order to grasp the influence of the phase noise, it is necessary to generate a signal to which the phase noise is added. A frequency converter is used to generate the desired signal. This frequency converter is composed of a combination of a high-frequency signal generator, a bandpass filter, a mixer, a noise generator, a high-frequency signal generator capable of frequency modulation with an external signal, and the like. In the conventional frequency converter, in order to change the frequency spectrum of the phase noise, the noise generator itself is replaced, or a filter that can obtain a target signal is inserted in the output signal of this noise generator. To do.

[0006]

However, the above-mentioned conventional frequency converter includes a high-frequency signal generator, a bandpass filter, a mixer, a noise generator, and a high-frequency signal generator capable of frequency modulation by an external signal. There is a problem that the equipment becomes very large-scale because it requires a vessel and the like.

Further, in order to change the frequency spectrum of the phase noise, it is necessary to replace the noise generator itself or insert a filter for obtaining an intended signal on the output side of the noise generator. Therefore, there is a problem that the allowable amount of phase noise cannot be easily grasped.

An object of the present invention is to solve the above problems and provide a frequency conversion device and method having a simple structure.

[0009]

In order to solve the above-mentioned problems, the invention of claim 1 provides a local oscillation signal by a noise generator capable of arbitrarily changing a frequency spectrum and noise generated by the noise generator. A frequency oscillating modulation section, and phase noise is added to the intermediate frequency signal by the local oscillation signal from the modulating section to which the noise is added, and the frequency of the intermediate frequency signal is converted. It is a frequency converter. The invention of claim 3 is
Noise is generated by arbitrarily changing the frequency spectrum, the local oscillation signal is frequency-modulated by the noise, and phase noise is added to the intermediate frequency signal by the local oscillation signal with the added noise. It is a frequency conversion method characterized by converting the frequency of a signal.

In the present invention, a noise generator capable of arbitrarily changing the frequency spectrum is provided inside, and the noise generated from the noise generator frequency-modulates the local oscillation signal used inside the device, thereby achieving the object of the present invention. It has a function to add phase noise to the output signal.

When an OFDM signal or the like is frequency-converted and transmitted by the common reception equipment, the phase noise allowed by the equipment can be easily grasped by arbitrarily changing the spectrum or level of the phase noise. .

According to a second aspect of the present invention, in the frequency conversion device according to the first aspect, the noise generating section shapes the spectrum of white noise to generate noise.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a frequency conversion device according to this embodiment. This frequency converter is the UH input to this device.
The broadcast wave signal of the F band has a frequency of 108 to 170 MHz,
The so-called MID band signal is frequency-converted and output.

The frequency converter of FIG. 1 has terminals 1, 15 and
16, 17, amplifiers 2, 4, attenuators 3, 11, mixers 5, 8, local oscillation signal generators 6, 12, bandpass filters 7, 14, white noise generator 9, spectrum shaping filter 10, and modulation A frequency modulator 13 is provided as a part.

The terminal 1 has, for example, frequencies 470 to 7
A modulation signal S1 of 70 MHz and an arbitrary 6 MHz bandwidth is input. The input modulation signal S1 is a modulation wave of an OFDM signal or a conventional analog television signal. The modulated signal S1 is formed by, for example, as shown in FIG. 2, signals S11, S12, ..., S1n having carrier frequencies at predetermined frequency intervals.

The amplifier 2, the attenuator 3 and the amplifier 4 form a regulation circuit. This adjusting circuit adjusts the level of the modulation signal S1.

The local oscillator signal generator 6 has a frequency of 870.
A local oscillation signal of ˜1170 MHz is generated and applied to the mixer 5. The mixer 5 frequency-converts the modulation signal S1 by the local oscillation signal from the local oscillation signal generator 6. As a result, the mixer 5 outputs the modulated signal S1 to 40
Convert to an intermediate frequency signal of 0 to 406 MHz. That is,
The local oscillation signal generator 6 outputs the modulated signal S1 from 400 to 40
A local oscillation signal is generated so as to be an intermediate frequency signal of 6 MHz.

The bandpass filter 7 is 400 to 406.
Has a pass band of MHz. The signals applied from the mixer 5 to the bandpass filter 7 include the local oscillation signal generated by the local oscillation signal generator 6 and an image frequency signal in addition to the intermediate frequency signal of 400 to 406 MHz. The band pass filter 7 passes an intermediate frequency signal of 400 to 406 MHz from these signals.

The white noise generator 9, the spectrum shaping filter 10 and the attenuator 11 form a noise generator.
This noise generator generates noise having an arbitrary frequency spectrum. The white noise generator 9 of the noise generator generates white noise having a wide frequency distribution. Upon receiving the white noise from the white noise generator 9, the spectrum shaping filter 10 forms noise having a preset arbitrary frequency spectrum.

An example of the spectrum shaping filter 10 is shown in FIG.
Shown in. The spectrum shaping filter of FIG.
0A to 10D and low-pass filter (LPF) 10E to 10I
It has and. Low-pass filters 10E to 10G are connected in parallel between the switch 10A and the switch 10B. The switch 10B is connected to the switch 10C, and low-pass filters 10H and 10I are connected in parallel between the switch 10C and the switch 10D.

The low pass filters 10E to 10I have different characteristics. In the spectrum shaping filter of FIG.
By switching the switches 10A to 10D, one of the low-pass filters 10E to 10G and one of the low-pass filters 10H and 10I are combined. Thereby, as shown in FIG. 4, for example, characteristics A1 to A4 having different pass bands can be obtained.

Upon receiving noise from the white noise generator 9, the spectrum shaping filter 10 shapes the spectrum of this noise based on the preset characteristics. That is, the spectrum shaping filter 10 forms noise having an arbitrary frequency spectrum.

The attenuator 11 is the spectrum shaping filter 1
When spectrum shaped noise is received from 0, the level of this noise is adjusted and sent to the frequency modulator 13. That is, the attenuator 11 adjusts the amount of added phase noise.

The local oscillation signal generator 12 generates a 508 to 570 MHz sine wave signal having high frequency purity and applies it to the frequency modulator 13 as a local oscillation signal.

The frequency modulator 13 frequency-modulates the local oscillation signal from the local oscillation signal generator 12 by the noise from the attenuator 11. As a result, the frequency modulator 13
Adds the phase noise shaped by the spectrum shaping filter 10 and the attenuator 11 to the local oscillation signal from the local oscillation signal generator 12. As a result, the frequency modulator 1
The signal output from 3 is, for example, as shown in FIG. 5A, with respect to the local oscillation signal S10 having no phase noise,
As shown in FIG. 5B, the phase noise S11 is added.

Further, it is possible to switch whether or not frequency modulation is performed by the frequency modulator 13. This switching is performed manually or automatically. Furthermore, attenuator 1
A terminal 16 is provided between the frequency modulator 13 and the mixer 8, and a terminal 17 is provided between the frequency modulator 13 and the mixer 8. Terminals 16 and 17 are for monitoring the quantitative level of phase noise. That is, the terminal 16
Is a monitor terminal for quantitatively measuring the noise generated from the white noise generator 9 whose frequency spectrum and noise amount can be arbitrarily changed. Further, the terminal 17 quantitatively measures the phase noise added by the frequency modulator 13 that frequency-modulates the local oscillation signal by the noise generated from the white noise generator 9 whose frequency spectrum and noise amount can be arbitrarily changed. It is for doing.

The mixer 8 is provided from the frequency modulator 13,
The intermediate frequency signal from the band pass filter 7 is frequency-converted by the local oscillation signal to which the phase noise is added. That is, the mixer 8 converts the intermediate frequency signal into a signal of an arbitrary channel in the MID band of 108 to 170 MHz by frequency conversion.

The band pass filter 14 has 108 to 17
It has a passband of 0 MHz. The signal applied from the mixer 8 to the bandpass filter 14 is 108 to 170 MH.
In addition to the z signal, the local oscillation signal generated by the local oscillation signal generator 12 and the signal that becomes the image frequency are output. The band pass filter 7 passes signals of 108 to 170 MHz out of these signals. As a result, for example, as shown in FIG. 6, the signals S21 and S2 having the carrier frequency of a predetermined frequency interval to which phase noise is added are added.
The modulation signal S20 formed of 2, ...
Sent to.

Next, the operation of this embodiment will be described. A modulation signal S1 having a frequency of 470 to 770 MHz and an arbitrary 6 MHz bandwidth is input to the terminal 1. The input modulation signal S1 is a modulation wave of an OFDM signal or a conventional analog television signal.

The modulated signal S1 input to the terminal 1 is level-adjusted by the amplifier 2, the attenuator 3 and the amplifier 4 and supplied to the mixer 5. The local oscillation signal which is a sine wave signal generated by the local oscillation signal generator 6 is also added to the mixer 5. The modulated signal S1 is frequency-converted into an intermediate frequency signal having a frequency of 400 to 406 MHz by the heterodyne method and output from the mixer 5. Mixer 5
The frequency of the local oscillation signal output from
The frequency of the signal generated by the local oscillation signal generator 6 is controlled so that it becomes MHz.

From the mixer 5, 400 to 406 MHz
Signal generated by the local oscillation signal generator 6,
Since a signal having a so-called image frequency is output, the bandpass filter 7 causes 400 to 406
Only the MHz signal is taken out. The intermediate frequency signal output from the bandpass filter 7 is sent to the mixer 8.

In this embodiment, the mixer 8 has a function of adding phase noise to the local oscillation signal when the frequency is converted. That is, the mixer 8 includes the frequency modulator 1
The local oscillation signal, which is a sine wave signal supplied from the local oscillation signal generator 12 via 3 and the noise from the attenuator 11, are supplied.

The signal generated by the local oscillation signal generator 12 is a sine wave having high frequency purity. When no phase noise is added to the signal output from the terminal 15, frequency modulation is turned off by the frequency modulator 13 and the signal is supplied to the mixer 8 as it is. When phase noise is added to the signal output from the terminal 15, the local oscillation signal is generated by the white noise supplied from the white noise generator 9 via the attenuator 11 and the spectrum shaping filter 10 which is a waveform shaping filter. The sine wave supplied from the generator 12 is frequency-modulated by the frequency modulator 13.

As mentioned above, the bandpass filter 7
The intermediate frequency signal output from the mixer and the sine wave signal supplied from the local oscillation signal generator 12 via the frequency modulator 13 are supplied to the mixer 8. In the mixer 8, the intermediate frequency signal from the bandpass filter 7 has a target frequency of 108 to 170 MHz by the heterodyne method.
Is converted into a signal of an arbitrary channel in the MID band. The converted signal is then passed through the bandpass filter 14
Is supplied to.

In addition to the target signal, the mixer 8 outputs a local oscillation signal which is a sine wave generated by the local oscillation signal generator 12 and an image frequency signal. Only the desired signal is taken out and output to the terminal 15.

By the above processing, the local oscillation signal generator 1
Phase noise is added to the sine wave supplied from 2, and as a result, phase noise is also added to the target modulated wave signal output from the terminal 15. The amount of added phase noise depends on the attenuator 1
1, the noise level input to the frequency modulator 13 is adjusted and controlled.

The spectrum of the phase noise is controlled by changing the spectrum of the noise input to the frequency modulator 13 by the spectrum shaping filter 10 which is a waveform shaping filter. In general, one of the causes of phase noise is fluctuation noise of 1 / f (f is frequency) of the device. To add phase noise equivalent to this,
The spectrum shaping filter 10 is given a so-called 1 / f characteristic and is input to the frequency modulator 13. In an actual transmission system, in addition to the 1 / f fluctuation noise that the device has, various types of noise caused by structural causes, noise caused by vibration, etc. It appears as phase noise in the signal.
In this embodiment, since the amplitude frequency characteristic of the spectrum shaping filter 10 can be arbitrarily changed, it is possible to add phase noise assuming various causes.

In this way, according to this embodiment, in the frequency conversion device for high frequency signals, the local oscillation signal necessary for frequency conversion is frequency-modulated by the noise signal generated inside the device. An arbitrary amount of phase noise can be added to the frequency signal and output.

Further, according to this embodiment, the broadcast wave signal in the UHF band can be frequency-converted into a so-called MID band signal having a frequency of 108 to 170 MHz and output, and the phase noise can be arbitrarily added.

Furthermore, according to this embodiment, the white noise generator 9 is used as the noise generator, and the spectrum of the noise is arbitrarily changed by the spectrum shaping filter 10 cascade-connected to the white noise generator 9 to frequency-modulate the local oscillation signal. . That is, in the high frequency signal transmission system involving frequency conversion, the white noise generator 9, the spectrum shaping filter 10, the attenuator 1
With a simple device configuration including the frequency modulator 13, the frequency modulator 13, and the mixer 8, it is possible to add arbitrary phase noise for transmission. Therefore, the allowable amount of phase noise in the system can be easily grasped.

Although the embodiment of the present invention has been described in detail above, the specific configuration is not limited to this embodiment, and there are design changes and the like within a range not departing from the gist of the present invention. Also included in the present invention. For example, in the spectrum shaping filter 10, three low pass filters 10E to 10G are connected in parallel between the switch 10A and the switch 10B, and two low pass filters 10H and 10I are provided between the switch 10C and the switch 10D. Were connected in parallel. However, the number of low-pass filters connected in parallel is not limited to these.

[0042]

As described above, according to the present invention, in a high frequency signal transmission system involving frequency conversion, arbitrary phase noise can be added and transmitted with a simple device configuration.

The transmission characteristics of the OFDM signal are as follows:
If the DM signal carrier modulation method is 64 QAM and the bit error rate after the Viterbi decoding of the inner code coding rate 7/8 convolutional code is 2 × 10E-4 or less, the bit error rate after the Reed-Solomon code decoding is 1 X10E-11 or less,
Almost error free. From this, the condition that the bit error rate after Viterbi decoding is 2 × 10E-4 or less is a reference.

Further, according to the present invention, in a high-frequency signal transmission system involving frequency conversion, there is provided a conventional high-frequency signal frequency conversion device which simply performs frequency conversion by the heterodyne system and does not have a function of adding an arbitrary amount of phase noise. In comparison, it is possible to add an arbitrary amount of phase noise under the condition that the bit error rate after Viterbi decoding, which is the reference value, is 2 × 10E-4 or less. That is, a local oscillation signal necessary for frequency conversion in the device is frequency-modulated by a noise signal generated inside the device, and a desired amount of phase noise is added to the high-frequency signal to obtain the high-frequency signal. It is possible to easily quantitatively grasp the allowable amount due to the phase noise of the transmission characteristic of the transmitted system.

[Brief description of drawings]

FIG. 1 is a block diagram showing a frequency conversion device according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an example of a signal of an OFDM modulated wave without phase noise.

FIG. 3 is a block diagram showing an example of a spectrum shaping filter.

FIG. 4 is a characteristic diagram showing characteristics of a spectrum shaping filter.

FIG. 5 is an explanatory diagram for explaining addition of phase noise.

FIG. 6 is a conceptual diagram showing a signal example of an OFDM modulated wave to which phase noise is added.

[Explanation of symbols]

1, 15, 16, 17 terminals 2, 4 amplifier 3 attenuator 5, 8 mixer 6, 12 Local oscillation signal generator 13 Frequency modulator 7, 14 band pass filter 9 White noise generator 10 Spectrum shaping filter 10A-10D switch 10E-10I Low pass filter 11 attenuator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiyuki Mineyoshi             7-4-12 Fukami-nishi, Yamato City, Kanagawa Prefecture             Inside this communication device Co., Ltd. (72) Inventor Hirotaka Iwashita             7-4-12 Fukami-nishi, Yamato City, Kanagawa Prefecture             Inside this communication device Co., Ltd. (72) Inventor Toshihiro Kubo             2-2, Jinnan 2-2-1, Shibuya-ku, Tokyo             Sending Association Broadcast Center (72) Inventor Rei Suzuki             2-2, Jinnan 2-2-1, Shibuya-ku, Tokyo             Sending Association Broadcast Center F term (reference) 5K020 AA03 BB06 DD11 FF04 GG00                       HH13 NN01                 5K022 DD01 DD13                 5K042 CA02 CA23 DA21

Claims (3)

[Claims] 1. A noise generator capable of arbitrarily varying a frequency spectrum, and a modulator that frequency-modulates a local oscillation signal by noise generated from the noise generator, and the noise generator adds the noise to the modulator. 2. A frequency converter which adds phase noise to an intermediate frequency signal and converts the frequency of the intermediate frequency signal by the local oscillation signal. 2. The frequency conversion device according to claim 1, wherein the noise generation unit shapes the spectrum of white noise to generate noise. 3. The frequency spectrum is arbitrarily changed to generate noise, the local oscillation signal is frequency-modulated by the noise, and phase noise is added to the intermediate frequency signal by the local oscillation signal to which the noise is added. In addition, the frequency conversion method is characterized in that the frequency of the intermediate frequency signal is converted.