JP2007228468A - Multi-carrier frequency hopping system, transmission circuit and receiving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve throughput by preventing deterioration in the code error rate of multi-carrier FH. <P>SOLUTION: In a modulator, a sending data SD is assigned for each carrier with a code mapping unit 11, the assigned sending data SD are then multiplied with carriers applied from a hopping pattern generator 13 in multipliers 12<SB>0</SB>to 12<SB>3</SB>, and moreover, the multiplied data are combined as a sending signal after the band-pass frequency is controlled with BPF14<SB>0</SB>to 14<SB>3</SB>for the center frequency of each carrier which is under the control of a coefficient-computing unit 15. In a demodulator, information band for the center frequency of carrier, corresponding to the sending signal, is extracted with BPF22<SB>0</SB>to 22<SB>3</SB>provided to each carrier and is then multiplied by the corresponding carrier with each multiplier 24<SB>0</SB>to 24<SB>3</SB>. Moreover, a sequence of data is rearranged with a decoder 26, and receiving data RD are generated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multi-carrier frequency hopping system (hereinafter referred to as “multi-carrier FH”) using a multi-level frequency shift keying modulation / demodulation method.

  2A to 2C are block diagrams showing the configuration of a conventional frequency shift (hereinafter referred to as “FSK”) modulation / demodulation system.

In the modulation block shown in FIG. 2A, the code string IN is input to two multipliers 1 ₀ and 1 ₁ , and is modulated by these multipliers 1 ₀ and 1 ₁ with different carrier frequencies f 0 and f ₁ , respectively. The modulated signals that are modulated and output by the multipliers 1 ₀ and 1 ₁ are added by the adder 2, converted to an analog signal by a digital / analog converter (hereinafter referred to as “DAC”) 3, It becomes an analog transmission signal SND in the frequency (IF) band or the radio frequency (RF) band.

In the demodulation block based on synchronous detection shown in FIG. 2B, a signal input to an antenna (not shown) passes through an analog circuit such as a gain amplifier and a filter, and an analog / digital converter (hereinafter referred to as “ADC”) 4. To receive signal RCV. Received signal RCV is converted into digital data by the ADC 4, is input to two multipliers ₅ 0, _{5 1,} are demodulated, respectively, by these multipliers ₅ 0, _{5 1} at different carrier frequencies f0, f1. The demodulated signals demodulated and output by the multipliers 5 ₀ and 5 ₁ pass through band pass filters (hereinafter referred to as “BPF”) 6 ₀ and 6 ₁ to become output signals OUT. In FSK modulation / demodulation, since only one of the two carrier frequencies f0 and f1 is an effective carrier wave, an invalid modulated signal is removed by the BPF 6 ₀ (or 6 ₁ ) after the demodulation operation, and an effective carrier wave is obtained. Is output as an output signal OUT.

  The demodulating block by asynchronous detection shown in FIG. 2 (c) includes an ADC 4, an envelope detector 7 and a maximum value discriminator 8 to which the received signal RCV is inputted. OUT is output.

JP-A-8-274752

  However, in the conventional FSK modulation / demodulation system, the values of the carrier frequencies f0 and f1 are defined by frequency intervals that satisfy the condition that the modulated frequencies are orthogonal in the case of MSK (Minimum Shift Keying) modulation. At this time, the values of the carrier frequencies f0 and f1 are invariant values. In the case of FSK for 2-bit transmission, four carrier waves are required, and the center frequency between the carrier waves is a constant value. In this case, since there is a one-to-one mapping between the transmission frequency and the code, the code arrangement of the transmission signal SND and the throughput are greatly related.

  When multilevel FSK modulation is performed by primary modulation, unless the orthogonality of each carrier is guaranteed, the code error rate (BER) deteriorates due to interference between carriers. Further, the conventional FH has a problem that the throughput cannot be improved because the hopping frequency is variable with respect to one reference carrier wave.

  An object of the present invention is to provide a multi-carrier FH that can prevent deterioration of a code error rate of a system that depends on a code arrangement and improve throughput.

  The present invention relates to a multicarrier that modulates data to be transmitted by performing frequency shift modulation using a plurality of carrier frequencies on the transmission side, and demodulates signals received at the plurality of carrier frequencies to reproduce data on the reception side The transmission side and reception side of the FH are configured as follows.

  That is, the transmission side is provided with a code mapping unit that allocates data to be transmitted to a plurality of carriers, a transmission hopping pattern generator that generates carrier frequencies of a plurality of carriers in accordance with the transmission timing, and a transmission side provided for each carrier. A plurality of transmission side multipliers for multiplying the carrier wave output from the hopping pattern generator and the data assigned by the code mapping unit, and a signal provided for each transmission side multiplier and output from the transmission side multiplier Output from multiple transmission-side filters that pass the information band centered on the corresponding carrier wave, transmission-side coefficient calculator that controls the passband for multiple transmission-side filters according to the transmission timing, and multiple transmission-side filters And an output unit that outputs a transmission signal by combining the signals to be transmitted.

  In addition, the receiving side is provided for each carrier wave, and a plurality of receiving side filters that pass through an information band centered on the corresponding carrier wave from among transmission signals sent from the transmitting side, and a plurality of receiving side filters according to the reception timing A reception side coefficient calculator for controlling the pass band for the reception side filter, a reception side hopping pattern generator for generating carrier frequencies of a plurality of carriers in accordance with reception timing, and a reception side filter provided for each carrier wave A plurality of reception side multipliers for multiplying the output signal by the carrier wave output from the reception side hopping pattern generator; and a decoder for decoding the signals output from the plurality of reception side multipliers to generate reception data. I have.

  In the present invention, the frequency of a plurality of carriers is set so as to maintain the orthogonality of the modulated signal, and the signal error rate of the system depending on the code arrangement is not deteriorated by simultaneously hopping the signal to a plurality of frequency bands. In addition, the throughput can be improved.

  In the multi-level FSK modulation / demodulation, the correlation between two modulated signals is set to 0, thereby using the least common multiple of the minimum transmission duration corresponding to the modulation index of 0.5 and simultaneously hopping the signals in a plurality of frequency bands. As a result, throughput is improved. Further, security can be improved by separately receiving decoding information for reconstructing a signal that reaches the receiving side at the same time.

  The above and other objects and novel features of the present invention will become more fully apparent when the following description of the preferred embodiment is read in conjunction with the accompanying drawings. However, the drawings are for explanation only, and do not limit the scope of the present invention.

  FIGS. 1A and 1B are configuration diagrams of an FSK modulation / demodulation system showing an embodiment of the present invention. FIG. 1A shows a modulation unit, and FIG. 1B shows a demodulation unit.

As shown in FIG. 1A, the modulation unit of the FSK modulation / demodulation system includes a code mapping unit 11 that allocates transmission data SD to the respective carriers f0 to f3. Connected to the output side of the code mapping unit 11 are multipliers 12 _{0 to} 12 ₃ that respectively multiply assigned data and corresponding carriers f ₀ to f ₃ . Further, the carrier waves f0 to f3 are supplied from the hopping pattern generator 13 in accordance with the main clock CLK that is the transmission timing. The frequencies of the carrier waves f0 to f3 are set to f1 = f0 + a, f2 = f0 + 2a, and f3 = f0 + 3a so as to have a constant interval.

The output side of the multiplier ₁₂ 0-12 ₃ are connected to each BPF 14 ₀ to 14 _3. In these BPFs 14 _{0 to} 14 ₃ , the frequency band to be passed is controlled according to the respective coefficients given from the coefficient calculator 15. That is, each of the BPFs 14 _{0 to} 14 ₃ is controlled so as to have a cutoff frequency equivalent to the one-side band of information from the center frequency of the corresponding carrier wave.

DACs 16 _{0 to} 16 ₃ are connected to the output sides of the BPFs 14 _{0 to} 14 ₃ , respectively. Output circuits such as a synthesis / amplification / filter (not shown) for generating transmission signals are connected to the output sides of the DACs 16 _{0 to} 16 ₃ .

On the other hand, as shown in FIG. 1B, the demodulator of this FSK modulation / demodulation system corresponds to ADCs 21 _{0 to} 21 ₃ for converting received signals into digital signals and the band of information signals centering on the modulation frequency at the time of transmission. a BPF 22 ₀ to 22 ₃ having a pass band, BPF 22 ₀ a to 22 ₃ of the coefficients, a coefficient calculator 23 for controlling in accordance with the main clock CLK is received timing, BPF 22 ₀ to 22 ₃ and the output signal from the carrier wave f0 a multiplier ₂₄ 0 - 24 ₃ for multiplying the f3, the main clock and hopping pattern generator 25 which generates a carrier wave f0~f3 in accordance with the CLK, received by decoding the output signal of the multiplier ₂₄ 0 - 24 ₃ data Decoder 26 that generates RD, and symbol synchronization is detected based on the output signal of decoder 26 to generate hopping pattern generator 2 It is composed of a synchronization detector 27 for timing control.

FIG. 3 is a configuration diagram showing a part of the hopping pattern generators 13 and 25.
This hopping pattern generator includes a phase comparator (CMP) 31, a loop filter (LPF) 32, a VCO (Voltage Controlled Oscillator) 33, a frequency divider (DIV) 34, and a voltage control unit 35. In addition to generating an n-fold frequency, it has an automatic frequency control function for the main clock CLK, and can further control the voltage of the VCO according to the oscillation frequency. When the oscillation frequency is not a multiplication of the main clock CLK, the voltage control unit 35 can directly control the VCO. FIG. 3 shows a circuit for one frequency, but when a plurality of carrier waves are generated, the same circuit is used as many as the number of carrier waves.

FIG. 4 is a configuration diagram showing a part of the decoder 26.
This decoder includes a decoding information storage unit 41 in which data of data reconstruction information is stored, a selector 42 that selects two channels according to decoding information from an input four-channel signal, and decoding information on the selected two-channel data. It is comprised by the rearrangement part 43 which rearranges according to.

Next, the operation will be described.
In the modulation unit, modulation is performed using the four carrier waves f0 to f3 generated by the hopping pattern generator 13. The frequency of the generated carrier waves f0 to f3 is controlled by the hopping pattern generator 13. After modulation, the coefficient calculator 15 calculates the coefficients of the BPFs 14 _{0 to} 14 ₃ from the cut-off frequency COF obtained from the hopping pattern generator 13, and the coefficients of these BPFs 14 _{0 to} 14 ₃ are sequentially determined for each symbol. The The cut-off frequency COF is determined by F−Fb and F + Fb (where F is the carrier frequency and Fb is one side band of the information signal).

On the other hand, the demodulator generates a frequency synchronized with the transmission side by the oscillation frequency controlled by the hopping pattern generator 25, similarly to the modulator. Also, the coefficients of BPFs 22 _{0 to} 22 ₃ are determined by changing the cutoff frequency of the next symbol in symbol units by the coefficient calculator 23 with respect to the input signal of the demodulator. Here, after the received signal is converted into a digital signal by the ADCs 21 _{0 to} 21 ₃ , BPFs 22 _{0 to} 22 ₃ having a cutoff corresponding to one side band of the information signal from the center frequency of each of the carriers f ₀ to f ₃ are received signals Established synchronously. Data of the frequency modulated by each of the carrier waves f0 to f3 is reconstructed by the decoder 26 to obtain received data RD.
In the coefficient calculator 23, the following equation (1) is processed.

  Here, αm is a filter coefficient, N is the number of samples, and m is a number obtained by adding a number to the number of samples.

The modulated signals v0 (t) to v3 (t) modulated by the respective carriers f0 to f3 are expressed by the following equation (2).
v0 (t) = Acos (2πf0t)
v1 (t) = Acos (2πf1t)
v2 (t) = Acos (2πf2t)
v3 (t) = Acos (2πf3t) (2)
The frequency of each carrier has the following relationship as described above.
f1 = f0 + a
f2 = f0 + 2a
f3 = f0 + 3a

In order to minimize the mutual interference of the modulated signals in Equation (2), it is necessary to satisfy all orthogonal conditions in ₄ C _two combinations. The condition for the correlation by each modulated signal to be 0 is shown in the following equation (3). Note that T0 to T5 in Equation (3) represent the transmission duration of one symbol data.

  As a result of the calculation formula (3), the minimum value (the one with the minimum frequency interval: modulation index = 0.5) is shown in the following formula (4).

  In order to always maintain the orthogonality of the modulated signals v0 (t) to v3 (t), it is necessary to satisfy all T0 to T5 in Expression (4). Therefore, the least common multiple T (LCM) of T0 to T5 in Equation (4) is the minimum transmission duration that satisfies Equation (4). Further, the condition that the least common multiple T (LCM) is minimum is when the frequency interval of the carrier wave is constant. Multi-level FSK modulation / demodulation satisfying this minimum duration is multi-level MSK modulation / demodulation in this embodiment. In the case of quaternary MSK modulation / demodulation, codes 00, 01, 10, and 11 are assigned to the carrier waves f0 to f3 of the modulation unit.

Next, data reorganization in the decoder 26 of the demodulator will be described.
Signals modulated simultaneously by two carrier frequencies on the transmitting side theoretically arrive at the receiving side simultaneously. Therefore, in order to reconstruct the demodulated data, it is necessary to determine the order of the signals that arrive at the same time.

FIG. 5 is a diagram showing a frame format sent from the transmission side to the reception side.
This frame format is an example of Bluetooth (registered trademark), and transmits a control frame before transmitting a data frame similar to the conventional one.

  In the data frame, an access code for establishing synchronization is arranged at the head of the frame, information such as the data length is arranged in the subsequent header part, and data and an error detection code are arranged in the subsequent payload part It is. On the other hand, in the control frame, an access code for establishing synchronization is arranged at the head of the frame, and then data reconfiguration information for reconstructing data in the payload part of the data frame is arranged for several symbols in advance. Is. Note that the number of bits necessary for the data reconstruction information depends on the data length of the payload portion. In addition, the code mapping unit 11 selects a modulation frequency so that modulation that matches the data reconstruction information is performed.

  FIG. 6 is a diagram illustrating an example of the data reconstruction information. The data reconstruction information shows a data reconstruction example in which the data reconstruction information is 0 or 1 with respect to the cases where the data demodulated with respect to the modulation frequency is 00, 10 and 01, 11.

  In the data reconstruction information, it is defined by the relationship of the frequency such that “code 0 = high frequency signal is the previous data” and “code 1 = high frequency signal is the subsequent data”. In the decoder of FIG. 4, two channels selected based on the data reconstruction information among the four channels input to the selector 42 are given to the rearrangement unit 43 as demodulated data. Further, the rearrangement unit 43 determines the output order based on the data reconstruction information. Further, when establishing synchronization, it is possible to establish synchronization by defining the use of a specific carrier wave.

As described above, the FSK modulation / demodulation system of this embodiment has the following advantages.
(1) The conventional MSK modulation / demodulation was applied only to binary transmission with a modulation index of 0.5. Therefore, the transmission rate could not be increased. In the present embodiment, even when multilevel processing is performed, the orthogonality of the modulated signal can be maintained, so that an improvement in transmission rate and throughput can be realized.
(2) Since the step width of the HF synthesizer may be 1 MHz or less, it is advantageous in terms of frequency utilization efficiency. FIG. 7 is a modulation image for explaining the effect of this embodiment. For example, Bluetooth
When applied to BPF, BPF needs to be switched at a rate of 1 Mbps. The step width of the HF synthesizer is 1 MHz × real number, and the frequency band is selected in the range of 2.4 to 2.48 MHz. In addition, the baseband main clock CLK is in time for arithmetic processing for switching the BPF coefficient at a rate of 1 MHz. For example, if the order of the BPF is quaternary, processing is in time if it is about 10 MHz.
(3) As shown in the frame format of FIG. 5, the transmission frame is transmitted by being separated into a control frame for transmitting data reconfiguration information and a data frame for transmitting data. As a result, the system is strong in security.

In addition, this invention is not limited to the said Example, A various deformation | transformation is possible. Examples of this modification include the following.
(A) Since a modulation / demodulation system that performs 2-bit multi-level processing has been described as an example, 2 ² = 4 carrier waves f0 to f3 are used, but when k-bit multi-level processing is performed, 2 2 ^It is configured to perform digital frequency modulation using ^k carrier waves f0 to f2k-1.
(B) Although the processing by the BPF or the multiplier is configured to be performed by digital processing, the processing may be performed using an analog circuit.

It is a block diagram of the FSK modulation / demodulation system showing an embodiment of the present invention. It is a block diagram which shows the structure of a FSK modulation / demodulation system. 3 is a configuration diagram showing a part of hopping pattern generators 13 and 25. FIG. 3 is a configuration diagram showing a part of a decoder 26. FIG. It is a figure which shows the frame format sent to the receiving side from the transmission side. It is a figure which shows an example of data reconstruction information. It is a modulation image explaining the effect of a present Example.

Explanation of symbols

11 Code mapping unit 12, 24 Multiplier 13, 25 Hopping pattern generator 14, 22 BPF
15, 23 Coefficient calculator 16 DAC
21 ADC
26 Decoder 27 Synchronization detector

Claims (5)

A multi-carrier frequency hopping system that modulates data to be transmitted by performing frequency shift keying modulation using a plurality of carrier frequencies on the transmission side, and demodulates signals received at the plurality of carrier frequencies to reproduce the data on the reception side Because
The sender side
A code mapping unit that assigns the data to be transmitted to a plurality of carriers;
A transmission-side hopping pattern generator that generates carrier frequencies of the plurality of carriers in accordance with transmission timing;
A plurality of transmission-side multipliers that are provided for each of the carrier waves and that multiply the carrier wave output from the transmission-side hopping pattern generator and the data assigned by the code mapping unit;
A plurality of transmission-side filters that are provided for each transmission-side multiplier and pass an information band centered on a corresponding carrier wave from signals output from the transmission-side multiplier;
A transmission-side coefficient calculator that performs passband control for the plurality of transmission-side filters in accordance with the transmission timing;
An output unit that synthesizes signals output from the plurality of transmission-side filters and outputs a transmission signal;
The receiving side
A plurality of reception-side filters that are provided for each of the carrier waves and that pass through an information band centered on a corresponding carrier wave from transmission signals transmitted from the transmission side;
A reception-side coefficient calculator that performs passband control for the plurality of reception-side filters in accordance with reception timing;
A reception-side hopping pattern generator that generates carrier frequencies of the plurality of carriers in accordance with the reception timing;
A plurality of reception-side multipliers that are provided for each of the carrier waves and multiply a signal output from the reception-side filter and a carrier wave output from the reception-side hopping pattern generator;
A decoder that decodes signals output from the plurality of reception-side multipliers to generate reception data;
A featured multi-carrier frequency hopping system.   The multicarrier frequency hopping system according to claim 1, wherein the frequencies of the plurality of carriers are set at fixed frequency intervals.   2. The decoder according to claim 1, wherein the decoder generates the received data by rearranging the order of data received by a plurality of carriers according to a control signal transmitted prior to transmission data from the transmitting side. Multi-carrier frequency hopping system. A code mapping circuit for assigning data to be transmitted to a plurality of carriers;
A hopping pattern generation circuit for generating carrier frequencies of the plurality of carriers in accordance with transmission timing;
A plurality of multiplication circuits provided for each of the carrier waves, for multiplying the carrier wave output from the hopping pattern generation circuit and the data assigned by the code mapping circuit;
A plurality of filters that are provided for each of the multiplier circuits and pass a desired frequency band among signals output from the multiplier circuit;
A coefficient arithmetic circuit that is provided for each of the plurality of filters and controls a pass band of the filter in accordance with the transmission timing;
An output circuit comprising: an output circuit that combines and outputs signals output from the plurality of filters. Among the received signals, a plurality of filters that pass a desired frequency band;
A coefficient arithmetic circuit that is provided for each of the plurality of filters and controls the passband of the filter in accordance with reception timing;
A hopping pattern generation circuit for generating carrier frequencies of the plurality of carriers in accordance with reception timing;
A plurality of multiplication circuits provided for each filter, for multiplying a signal output from the filter and a carrier wave output from the hopping pattern generation circuit;
A receiving circuit comprising: a decoder that decodes signals output from the plurality of multiplication circuits to generate reception data.

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