JPH0360251A - Modulator - Google Patents

Abstract

PURPOSE:To effectively utilize a frequency by varying a modulation- demodulation system and a transmission signal bit rate having been fixed conven tionally, and applying adaptive transmission with a control signal controlled depending on the state of the transmission line. CONSTITUTION:The modulator is provided with a data input terminal 1-1, an RF signal output terminal 1-2, a control circuit 1-3, a serial/parallel conversion circuit 1-4, a channel designation device 1-5, a modulator section 1-6, an adder 1-7, a D/A converter 1-8 and an orthogonal modulator 1-9. When the signal propagation state is excellent in response to the change in the state of a trans mission line for the signal attended with the change in the distance, multivalue modulation-demodulation with efficient frequency is used for the signal, or high bit rate transmission is applied by widening the signal transmission band, and when the propagation state near the surrounding of a zone is deteriorated, the modulation-demodulation system with excellent error rate characteristic is used or the signal is sent while making the signal transmission band narrow. Thus, the utilizing efficiency of the frequency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a modulator suitable for mobile communication using the 5CPC system.

Specifically, the present invention relates to a modulator that has a plurality of modulation functions such as frequency modulation, phase modulation, and amplitude phase modulation, and can select one of them at high speed based on an external command.

[Conventional technology]

In current mobile communications such as car phones and pagers, 1
5CPC method that allocates one channel to two frequency bands (
Single-Channel PerCarrie
r) is used. In this case, the frequency spacing used by each channel is fixed, and in current analog signal car phones, the channel spacing is 25kHz and 12.5kHz.
It is z.

In the future, it is thought that digital signal transmission will be put into practical use in mobile communications as we move toward the establishment of 15DN$4 mobile communications, and transmission signals will also be used to transmit data, WRa information, etc. in addition to the current voice. It is considered to be.

TDM is the channel access method for digital mobile communications.
The A method and the 5CPC method are considered, but when using the 5CPC method, the channel spacing is usually constant.

However, since there can be many types of transmission signals as described above, it is conceivable that different bands are required for each type of transmission signal.

For example, sending a facsimile requires 4.8 kb/s (
(kilobits/second), 2.4 kb/s for data, and 16 kb/s for audio. This is due to redundancy as well as the content of the original signal.

Therefore, the line quality required to accurately transmit these signals also differs depending on the signal type.

In terms of code error rate, facsimile is 10-1 to 10-
4, for voice it should be about 10-2, and for data transmission such as PC communication, 10-4 or less is required. Therefore, for example, in data transmission and facsimile transmission, which require strict quality, there is a margin in transmission speed compared to voice transmission, so it is possible to improve reliability by applying error control.

However, the appropriate bandwidth will still not be the same for each transmitted signal.

Dinotal modulation methods used in mobile communications include frequency position modulation (FSK), phase modulation (PSK), and amplitude phase modulation I.
I (QAM), PSK has two-phase P depending on the number of multi-values.
SK (BPSK), 4-phase PSK (QPSK)
, 8-phase PSK, etc., and QAM also includes 16QAM, 25QAM, etc.
There are 6QAM, etc.

As is well known, as multi-level data is used, the margin for noise decreases, so the bit error rate deteriorates for the same reception level.

In the 5CPC method, the optimal modulation method is determined according to the required transmission speed and required quality. Conventionally, when the modulation method was determined by the system in this way, good transmission quality was achieved under that modulation method. We have applied technology to ensure this.

[Problem to be solved by the invention]

When a mobile station moves through a radio zone around a base station,
Land mobile propagation characteristics include distance fluctuations due to changes in the distance between the mobile station and other stations, median fluctuations caused by the influence of other things such as buildings around the mobile station, and instantaneous values caused by diffuse reflection from buildings etc. It is expressed by three types of fluctuation.

The instantaneous value fluctuation is Rayleigh 7 with a fast pitch and deep drop.
However, various ubiquity techniques can be applied to ensure signal transmission quality.

The current system also uses receive diversity, which involves installing two receiving systems in a mobile device and selecting the received signal with a higher reception level, and by transmitting signals from multiple base stations at the same time with slightly different frequencies or waveforms. A waveform offset type or frequency offset type guiversity is used, which can be expected to produce a guiversity effect near the boundary of the zone.

Furthermore, regarding distance fluctuations, transmission power control from the base station is performed. This notifies the other party of information about the reception level and controls the transmission power so that the level remains constant, which is effective in reducing channel interference. This transmission power is the only parameter that is controlled according to changes in the propagation state mainly due to the distance between the base station and the mobile station.

Therefore, since the transmission speed is not made variable or the modulation method is not made variable depending on the content of the signal to be sent, the transmission quality and frequency band may become excessive.

Since most of the conventional methods transmit audio,
Although this did not pose a problem, these points may become a problem in the future as the content of signals to be sent becomes more diverse.

From the standpoint of effective frequency utilization, the present invention provides a multi-level system for transmitting signals with good frequency efficiency when the signal propagation conditions are good, depending on changes in the signal transmission path conditions mainly due to distance fluctuations. Ai11 is used or the signal transmission band is widened to perform high bit rate transmission, and if the propagation conditions near the zone are poor, a modulation/demodulation method with good error rate characteristics is used to ensure transmission quality. Alternatively, it is an object of the present invention to provide a modulation/demodulation circuit for use in narrowing the signal transmission band for transmission. .

[Means to solve the problem]

According to the invention, the above-mentioned objects are further related to the means defined in the claims.

That is, the present invention provides a means for converting an input signal into a plurality of series of signals having different transmission speeds, a means for band-limiting the input signal,
Based on the offset frequency signal, there are 1* or 2 or more variable elements for each different type of modulation method that output channel and Q channel signals, and the above band limit width and offset frequency are set for each modulation element. A digital modulation section that can be specified externally, and the signals converted into the above multiple series,
means for selectively connecting to each modulation element based on external designation;
Each of the above changes! The I channel and Q channel signals of the element are
This modulator is characterized in that it is provided with means for digitally adding and converting into analog quantities, and an orthogonal modulator section that applies orthogonal modulation to the analog signals of the channel (1) and Q channel.

[For production]

The present invention utilizes modulation and demodulation methods that were conventionally fixed, and modulation that makes it possible to perform adaptive transmission by making the transmission signal bit rate variable and using a control signal that is controlled according to the conditions of the transmission path. It is a vessel.

When realizing a multi-mode modulator that can change the modulation method, it is not practical to arrange a large number of individual modulators.

Therefore, a baseband dinotal signal processing circuit constitutes a modulator that can change the modulation method and signal band, and can specify a channel using the baseband signal.

Hereinafter, the specific configuration, operation, etc. of the modulator of the present invention will be explained based on examples.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 1 is a diagram showing the III# command of a variable band digital modulator in a baseband channel access variable mode,
1-1 is a data input terminal, 1-2 is an RFM signal output terminal,
1-3 is a control circuit, 1-4 is a serial/parallel conversion circuit, 1-5 is a channel selector (channel designator), 1-6 is a modulation section, 1-7 is an adder, 1-8 is a D/A @ converter (D/A),
1-9 represent quadrature modulators.

In this embodiment, the serial/parallel conversion circuit 1-4 converts an input signal into multiple series of data at a lower speed, and the channel selector 1-5 divides the data into four data.

The variable IR unit 1-6 shows a case where 16QAM and QPSK%GMSK are used.

Q P S K to G M S K no strange 111 child! An example will be given later, but as in this example, 16QAM
#! I/QPSK modulates two sequences of input data, and GMSK modulates one sequence of input data.

In other words, the 16QAM modulation element has channel CH(1).
A signal is input from the selector of CH (1), and the QPSK (1) modulation element receives a signal from the selector of CH (1).
(2) Signals are input to each modulation element from the selector of channel CH(2).

GMSK (1) - GMSK (4) Signals are input to the 11 variable elements from the selectors of the corresponding channels CH(1) to CH(4), respectively.

This is weird! Elements are mainly ROM (read only memory) or RAM (random access memory).
A band limit filter and a predetermined offset frequency are applied to the signal in a signal processing section.

This band limit and offset information is received from the control circuit 1-3. Since the output of the modulation element is the amplitude information of the in-phase component and the orthogonal valve, the adder 1-7 calculates the amplitude envelope 4! The signals are summed and sent to respective D/A converters 1-
After the signal is converted into an analog signal in step 8 and harmonic components are removed, an RF modulated signal is generated in quadrature modulator 1-9. M
Cross modulation n1-9 is example L if ¥t II Hei 1-42
The configuration disclosed in '815 can be used.

Further, a specific example of the GMSK modulation element is shown in FIG.

That is, FIG. 2 is a diagram showing the #1B example of a GMSK modulator (center frequency offset), in which 2-1 is a data input terminal, 2-2 is a channel designation terminal, 2-3 is an I channel output terminal, -4 is a Q channel output terminal, 2-5 is a Gaussian ROM filter, 2-6 is an adder, 2-7 is an integrator, 2
-8 is ROM CO3 table, 2-9 is ROM5I
N represents a table.

After the input data is band-limited by the USB ROM filter 2-5, it is added by the adder 2-6 by the carrier frequency corresponding to the channel, and after being integrated and changed to a phase amount, CO8 and SIN weight are calculated. By taking this, the in-phase component to be input to the quadrature modulator and the amplitude information of the quadrature valve can be generated.

Further, a specific example of the QPSK modulation element is shown in FIG.

That is, FIG. 3 is a diagram showing an example of the configuration of a center frequency offset QPSK modulator, in which 3-1 is a data input terminal;
3-2 is a channel designation terminal, 3-3 is an channel output terminal, 3-4 is a Q-channel output terminal, 3-5 is a ROM roll-off filter, and 3-6 is a multiplier.

In this example, after each of the two input data sequences is band-limited by the ROM roll-off filter 3-5, the multiplier 3-5
6, the signal is multiplied by the carrier frequency component to generate in-phase and orthogonal valve amplitude information.

Next, another embodiment using the modulator of the present invention will be described.

These modulation methods and signal transmission speeds can be adaptively changed according to the received MM signal level or the error rate characteristics of the received signal.

FIG. 4 shows a conceptual diagram for adaptively changing the modulation/demodulation method.

Showing the cases of 16QAM%QPSK and GMSK from the top,
QPSK can send twice as much information as GMSK, and 16QAM can send four times as much information. If the signal propagation conditions are not very good, use the GMSK modulation method with high noise tolerance as shown in the figure, and if the signal propagation conditions are good, use a modulation method with good frequency utilization efficiency such as 16QAM modulation method. use

In this way, when data with the same transmission rate is modulated using each modulation method, 16QAM only requires a frequency band that is 1/4 that of GMSK.In other words, switching the modulation method is
This is equivalent to switching the signal transmission band.

Therefore, in order to make effective use of this modulator, it is necessary to have a variable bandpass filter and a dedicated demodulator in the receiver.

In current group-converging type mobile devices, a ceramic filter is used as a second IF filter that attenuates adjacent channel signals, and the received signal band is fixed.

In order to transmit signals aggressively, on the receiving side, a variable band filter consisting of an active filter is used to realize a fill band according to the transmission signal speed and remove adjacent unnecessary signal components. The 11th F filter for removing the image signal generated by the $2 mixer is 5AW (surface acoustic wave).
The second IF filter for removing adjacent signals is disclosed in Japanese Patent Application No. 62-313339 and Japanese Patent Application Laid-open No. 62-29.
SCF (switched capacitor filter) and MOS FET-C (Cont
(intuitive) configuration with combined filters.

SCF-MOS that performs filtering by reducing the fractional band of the signal using the folded signal from sampling
An NII example of the FET-C combined variable band filter is shown in FIG.

This is mainly composed of a switched capacitor main filter 5-2. This allows the filter frequency characteristics to be changed by an electrical control signal.

Digital FMM signal, Dinotal PM signal or QA
A synchronous detector can be used to demodulate the M signal. The clock signal regenerator and carrier wave signal regenerator can be configured with digital processing circuits, and can demodulate signals of various bit rates by changing the clock signal.

The configuration of the mobile non-A1ff1 using the modulator of the present invention is shown in the sixth example.
In the figure, 6-1 is a data input terminal;
-2 is a baseband digital signal processing unit, 6-3 is a mixer, 6-4 is a power amplifier, 6-5 is an antenna, 6-
Reference numeral 6 represents a duplexer, 6-7 a variable band filter, 6-8 a demodulator, 6-9 a control circuit, and 6-10 a frequency synthesizer.

Baseband digital signal processing unit 6- which is a modulation circuit
2 is the modulation circuit of the present invention shown in FIG. The transmitting section is comprised of a baseband digital signal processing section 6-2, which is this modulation circuit, a mixer 6-3, and a power amplifier 6-4.

The receiving section includes a duplexer 6-6, a mixer 6-3, a local frequency synthesizer 6-10, a variable band filter 6-7, a demodulator 6-8, and a control circuit 6-9.

This variable band filter 6-7 is shown in FIG.

The control circuit 6-9 controls the modulation/demodulation method and the signal transmission band based on information about the received signal level and the error rate of the received signal.

A system configured using this mobile device is shown in FIG. 7, in which 7-1 is a base station, 7-2 is a mobile station,
7-3 is a data input terminal; 7-4 is a baseband digital signal processing section; 7-5 is a mixer; 7-6 is a power amplifier; 7-7 is an antenna; 7-8 is a frequency synthesizer;
-9 is the RF filter, mark 10 is the 11th F filter, 7
-11 is an oscillator, 7-12 is a 21st F filter (variable band IF filter), 7-13 is an AGC or limiter, 7-14 is a signal level detector, and 7-15 is a control circuit.

This system adaptively controls the modulation/demodulation method and bandwidth according to the status of the radio link from the base station to the mobile station, and can be configured in the same way for the link from the mobile station to the base station.

After the adjacent channel signal is removed by the tI42 IF filter 7-12, the average value of the envelope level of the F received signal detected by the detector 7-14 is calculated by the microcomputer in the control circuit 7-15. The time average value is compared with a preset reference value, and a control signal for the modulation method or signal bandwidth according to the set level is transmitted to the base station at the same time as the transmission signal, and the base station converts the baseband digital signal using the control signal. The processing unit 7-4 sets the modulation method and signal transmission rate.

The mobile station controls the edible band IF filter 7-12 to set the corresponding bandwidth.

〔Effect of the invention〕

As explained above, by using the modulator of the present invention, the signal bandwidth of the transmitter and receiver can be changed according to the required band of the signal to be transmitted, so the minimum necessary band for signal transmission can be used. This is advantageous in terms of frequency utilization efficiency. When the propagation conditions are good, the signal is multivalued and transmitted, so the symbol rate can be lowered and the signal band can be narrowed.

Additionally, in the past, it was necessary to increase the transmission power of the mobile station/base station in order to increase the average reception level of the base station/mobile station at locations with poor propagation conditions near the periphery of the zone. In addition, the transmission power of the mobile station/base station can be reduced.

[Brief explanation of drawings]

Figure 1 is a diagram showing a configuration example of a baseband channel access variable mode and variable band dinotal modulator.
A diagram showing an example of the configuration of an MSK modulator, FIG. 3 is a QPS
A diagram showing an example of the configuration of a K modulator, FIG. 4 is a diagram explaining the concept of adaptively changing the modulation/demodulation method, a vJS diagram is a diagram showing an example of the configuration of a variable band filter, and FIG. 6 is a diagram of the modulator of the present invention. FIG. 7 is a diagram showing another embodiment of the present invention. 1-1...Data input terminal, 1-2
...... RF signal output terminal, 1-3
...Control circuit, 1-4 ...Serial-to-parallel converter, 1-5 ...Channel designator,
1-6 ......'Ii key part, 1-7
...Adder, 1-8...D/A converter, 1-9...Quadrature modulator,
2-1...Data input terminal, 2-
2...Channel specification terminal, 2-3...
... ■Channel output terminal, 2-4...Q
Channel output terminal, 2-5...Gauss ROM filter, 2-6...
Adder, 2-7...Integrator, 2-
8...ROM COS table, 2-9 ・
...ROM5IN table, 3-1 ...
・Data input terminal, 3-2...Channel specification terminal, 3-3...I channel output terminal, 3-4...Q channel output terminal, 3-5 ...ROM
Roll-off filter, 3-6... Multiplier,
5-1...MOSFET-C thinning filter, 5-2...Switched capacitor main filter, 5-3...MOS
FET-CFkI interpolation filter, 6-1... Data input terminal, 6-2... Baseband digital signal processing section, 6-3... Mixer, 6-4 ・... power amplifier,
6-5... Antenna, 6-6...
..... duplexer, 6-7 ..... variable band filter, 6-8 ..... demodulator,
6-9 ... Control circuit, 6-10 ・
...Frequency synthesizer, Mar1 ...
... Base station, 7-2 ... Mobile station,
7-3...Data input terminal, 7-4
...Baseband digital signal processing section,
7-5...Miku power amplifier, 7-8...Frequency 7-9...RF 7-10...No. ITF 7-11... ...Oscillator, 7 second IF filter (variable band IF 7-13 ...AGC* or 7-14 ...
...Signal level detection 7-15 ...Control circuit, 7-6 ...7-7 ...Antenna, number synthesizer, filter, router, -12. ... filter), limiter, output device,

Claims (1)

[Claims] Means for converting an input signal into a plurality of series of signals having different transmission speeds;
a digital modulation section having one or more modulation elements for each different type of modulation method that outputs I-channel and Q-channel signals, and in which the band limit width and offset frequency can be externally specified for each modulation element; Means for selectively connecting the signals converted into the plurality of series to each modulation element based on external designation, and means for digitally adding the I channel and Q channel signals of each of the modulation elements and converting them into analog quantities. and an orthogonal modulator section that applies orthogonal modulation to the I-channel and Q-channel analog signals.