Spread spectrum communication device, spread spectrum communication system, control circuit, storage medium, and communication method

Abstract

A spread spectrum communication device (10) comprises: a weighting multiplication unit A (106) and a weighting multiplication unit B (107) that control modulation signals so as to have the same or different amplitudes and phases for individual weighting coefficient periods, which are periods obtained by dividing the modulation signal by time, multiply each of all samples of the modulation signals by a corresponding weighting coefficient among a plurality of weighting coefficients of which the amplitudes change for each sample of the modulation signal, and generate weighted modulation signals, which are weighted signals of the modulation signals; and a frequency conversion unit A (108) and a frequency conversion unit B (109) that convert carrier frequencies of the weighted modulation signals to the same or different carrier frequencies for each weighting coefficient period, and generate modulation signals obtained by time-multiplexing the plurality of carrier frequencies.

Description

Spread spectrum communication device, spread spectrum communication system, control circuit, storage medium, and communication method

[0001] This disclosure relates to spread spectrum communication devices, spread spectrum communication systems, control circuits, storage media, and communication methods in wireless communication.

[0002] Frequency hopping is a type of spread spectrum technique in wireless communication that periodically switches signals to different frequencies according to a specific pattern, transmitting signals over a wide bandwidth. Frequency hopping improves the reliability of wireless communication by making it less susceptible to interference from other systems, and also improves confidentiality by making signal detection difficult and preventing interception. For this reason, frequency hopping is widely used in wireless standards such as wireless LAN (Local Area Network) and Bluetooth®.

[0003] Frequency hopping is classified into slow frequency hopping and fast frequency hopping based on the speed of frequency switching. While fast frequency hopping involves rapid frequency switching, it utilizes a wider frequency bandwidth compared to slow frequency hopping. For example, in fast frequency hopping, where frequencies are switched at a short period shorter than the symbol time of the modulated signal, a frequency bandwidth wider than the signal bandwidth of the symbol rate is required. However, due to the fast frequency switching speed, fast frequency hopping offers superior interference resistance, interception resistance, and security compared to slow frequency hopping.

[0004] Thus, since the frequency hopping effect and frequency bandwidth are determined by the frequency switching speed, it is desirable to flexibly adjust the frequency switching speed according to the available frequency bandwidth. Patent Document 1 discloses a device for performing high-speed frequency hopping spread spectrum modulation, in which a chip signal shaped by a Nyquist filter is multiplied with a primary modulated signal, and the resulting signal is frequency hopped, and the occupied frequency bandwidth of each chip signal can be freely changed and transmitted by changing the coefficients of the Nyquist filter.

[0005] Japanese Patent Application Publication No. 8-32553

[0006] However, the technology disclosed in Patent Document 1 involves shaping each chip signal with a Nyquist filter, which causes intersymbol interference between adjacent chips. Therefore, the technology disclosed in Patent Document 1 has the problem of a decrease in SNR (Signal to Noise Ratio) during demodulation on the receiver side. Furthermore, in order to change the occupied frequency bandwidth of each chip signal within the same communication, it is necessary to prepare as many Nyquist filter coefficients as there are types of bandwidths to be changed, and it is also necessary to prepare multiple dedicated Nyquist filters according to the tap length of the Nyquist filter. Thus, the technology disclosed in Patent Document 1 has the problem of an increased circuit size.

[0007] This disclosure has been made in view of the above, and aims to provide a spread spectrum communication device that can efficiently utilize available frequency bands and improve frequency utilization efficiency by flexibly adjusting the frequency switching speed according to the available frequency band conditions, while suppressing the effects of intersymbol interference and the increase in circuit size in high-speed frequency hopping transmission.

[0008] To solve the above-mentioned problems and achieve the objective, the spread spectrum communication device according to this disclosure is characterized by comprising: a modulation unit that converts a transmission bit sequence into a modulated signal using one or more of the phase, frequency, and amplitude of a carrier wave; a weighting multiplication unit that controls the modulated signal so that the amplitude and phase are the same or different for each weighting coefficient period, which is a period divided by time, and multiplies each of all samples of the modulated signal by a corresponding weighting coefficient from a plurality of weighting coefficients whose amplitude changes for each sample of the modulated signal to generate a weighted modulated signal which is a weighted signal of the modulated signal; a frequency conversion unit that converts the carrier frequency of the weighted modulated signal into the same or different carrier frequency for each weighting coefficient period and generates a modulated signal obtained by time multiplexing a plurality of carrier frequencies; and a channel combining unit that adds up the weighted modulated signals of a plurality of carrier frequencies to generate a composite signal of the weighted modulated signals of a plurality of carrier frequencies.

[0009] The spread spectrum communication device described herein has the effect of improving frequency utilization efficiency by flexibly adjusting the frequency switching speed according to the available frequency band conditions, while suppressing the effects of intersymbol interference and the increase in circuit size during high-speed frequency hopping transmission, thereby efficiently utilizing available frequency bands.

[0010] Figures showing the configuration of a spread spectrum communication system according to Embodiment 1 Figures showing the configuration of a spread spectrum communication device according to Embodiment 1 Figures showing examples of weight coefficients A and B applied to the modulation signal in Embodiment 1 Figures showing examples of frequency hopping patterns A and B in Embodiment 1 Block diagram showing the configuration of a control circuit that realizes the spread spectrum communication device according to Embodiment 1 Figures showing a processing circuit when some or all of the functions of the modulation unit, weighted multiplication unit A, weighted multiplication unit B, frequency conversion unit A, frequency conversion unit B, channel synthesis unit, digital-to-analog conversion unit and transmission high-frequency unit of the spread spectrum communication device according to Embodiment 1 are realized by a processing circuit that is dedicated hardware Figures showing the configuration of a spread spectrum communication device according to Embodiment 2 Figures showing examples of weight coefficients A' and B' applied to the modulation signal in Embodiment 2 Figures showing examples of frequency hopping patterns A' and B' in Embodiment 2 Explanatory diagram showing an example of a transmission signal in Embodiment 2 Figures showing the configuration of a spread spectrum communication device according to Embodiment 3 Figures showing examples of weight coefficients A'' and B'' applied to the modulation signal in Embodiment 3 Explanatory diagram showing an example of a transmission signal in Embodiment 3 Figures showing a storage medium that stores a program for executing the operation of a spread spectrum communication device according to any of the embodiments from Embodiments 1 to 3

[0011] The spread spectrum communication device, spread spectrum communication system, control circuit, storage medium, and communication method according to the embodiment will be described in detail below with reference to the drawings.

[0012] Embodiment 1. FIG. 1 is a diagram showing a configuration of a spread spectrum communication system 5 according to Embodiment 1. The spread spectrum communication system 5 includes a spread spectrum communication apparatus 10 and a receiving apparatus 20. Wireless communication using a spread spectrum communication scheme is performed between the spread spectrum communication apparatus 10 and the receiving apparatus 20. Hereinafter, "spread spectrum communication apparatus" may be referred to as "transmitting apparatus".

[0013] FIG. 2 is a diagram showing a configuration of the spread spectrum communication apparatus 10 according to Embodiment 1. As shown in FIG. 2, the transmitting apparatus 10 includes a modulation unit 105, a weighting multiplication unit A 106, a weighting multiplication unit B 107, a frequency conversion unit A 108, a frequency conversion unit B 109, a channel combining unit 110, a digital-to-analog conversion unit 111, a transmission high-frequency unit 112, and a transmission antenna 113. A transmission bit sequence 100, a weighting factor A 101, a weighting factor B 102, a frequency hopping pattern A 103, and a frequency hopping pattern B 104 are input to the transmitting apparatus 10. First, information input to the transmitting apparatus 10 will be described, and then each component of the transmitting apparatus 10 will be described.

[0014] The transmission bit sequence 100 is a transmission information bit or a bit sequence encoded for the transmission information bit, and is input to the modulation unit 105.

[0015] The weighting factor A 101 is a weighting coefficient for controlling the amplitude and phase of the modulated signal to adjust the bandwidth of the modulated signal and suppress the peak factor after frequency channel signals are combined, and is input to the weighting multiplication unit A 106.

[0016] Similarly to the weighting factor A 101, the weighting factor B 102 is a weighting coefficient for controlling the amplitude and phase of the modulated signal to adjust the bandwidth of the modulated signal and suppress the peak factor after frequency channel signals are combined, and is input to the weighting multiplication unit B 107.

[0017] Each of the weighting factor A 101 and the weighting factor B 102 is a coefficient for controlling the amplitude and phase of the modulated signal, and is represented as a complex number in Embodiment 1. When the imaginary part of the weighting factor is 0, the coefficient only controls the amplitude.

[0018] Figure 3 is a diagram illustrating an example of weighting factor A 101 and weighting factor B 102 applied to a modulated signal in the first embodiment. Here, θ Ａ０ , θ Ａ１ , θ Ａ２ , θ Ａ３ are the phase control amounts of the modulated signal controlled for each weighting factor A period by weighting factor A, θ Ｂ０ , θ Ｂ１ , θ Ｂ２ , θ Ｂ３ indicates the phase control amount of the modulated signal controlled for each weighting factor B period by weighting factor B. In the example of Figure 3, a symbol period is divided into 8 chips, and the weighting factor period is 2 chip periods. The periods of weighting factor A 101 and weighting factor B 102 are the same, but the start timing of the weighting factor A period and the start timing of the weighting factor B period are shifted by 1 chip period.

[0019] The maximum amplitude position of each of weighting factor A 101 and weighting factor B 102 is the center timing of the chip signal. In order to prevent mutual interference between weighting factor A 101 and weighting factor B 102 at the center point of a chip signal, at the timing when one of weighting factor A 101 and weighting factor B 102 reaches the maximum amplitude, the amplitude of the other weighting factor is reduced to suppress inter-chip interference. For example, by setting the amplitude of the other weighting factor to 0 at the timing when one weighting factor reaches the maximum amplitude, inter-chip interference in the transmission signal can be reduced to zero.

[0020] For the amplitude of each of weighting factor A 101 and weighting factor B 102, a time window function such as a commonly known Hann window can be used, for example, according to the conditions of the bandwidth to be adjusted and the peak factor to be suppressed. However, the values applied to the weighting factors in the first embodiment are not limited thereto.

[0021] The weighting factor A 101 controls the phase of a modulated signal by providing a different phase offset 200 for each period of the weighting factor A corresponding to each chip signal. The weighting factor B 102 controls the phase of a modulated signal by providing a different phase offset 201 for each period of the weighting factor B corresponding to each chip signal. For example, as in π / 2-shift BPSK (Binary Phase Shift Keying), the weighting factor A 101 is selected from {0, π} for each period of the weighting factor A to determine the amount of phase rotation, and the weighting factor B 102 is selected from {π / 2, -π / 2} for each period of the weighting factor B to determine the amount of phase rotation. By orthogonalizing the phases between temporally adjacent weighting factor periods, intersymbol interference can be suppressed in transmission and reception.

[0022] In the first embodiment, the phase rotation applied to each of the weighting factor A 101 and the weighting factor B 102 is not limited to that described above, and may be arbitrarily selected. Shortening the period of the weighting factor A and the period of the weighting factor B adds steep amplitude fluctuations to the modulated signal, thereby broadening the bandwidth. Conversely, lengthening the period of the weighting factor A and the period of the weighting factor B narrows the bandwidth of the modulated signal. Accordingly, the bandwidth of the modulated signal can be freely set by adjusting the period of the weighting factor A and the period of the weighting factor B.

[0023] FIG. 4 is a diagram showing an example of frequency hopping pattern A 103 and frequency hopping pattern B 104 in the first embodiment. The frequency hopping pattern A 103 is configured to frequency-hop the modulated signal multiplied by the weighting factor A 101 output from the weighting multiplier A 106 to any one of frequency channels f ０ , f １ , f ２ , f ３ , and is a sequence indicating the order of frequency channels. In the example shown in FIG. 4, the frequency hopping pattern A 103 follows the order of f ３ →f ２ →f ３ →f ０ within a symbol period, and is a sequence indicating this order.

[0024] The frequency hopping pattern B104 modulates the modulated signal, which has been multiplied by the weight coefficient B102 output from the weighted multiplication unit B107, at a frequency channel f with a period of weight coefficient B. ０ , f １ , f ２ , f ３ This is a sequence of frequency channels indicating the order of frequency channels for frequency hopping to one of the following. In the example shown in Figure 4, frequency hopping pattern B104 is f within the symbol period. ０ →f １ →f ２ →f １ This is a sequence that shows the order. In the example in Figure 4, each of frequency hopping pattern A103 and frequency hopping pattern B104 is a pattern that is repeated with each symbol period. Each of frequency hopping pattern A103 and frequency hopping pattern B104 may be a sequence of different frequency hopping patterns with each symbol period.

[0025] Returning to Figure 2, each processing unit of the transmitting device 10 will be described. The modulation unit 105 performs primary modulation on the transmitted bit sequence 100 using one or more of the phase, frequency, and amplitude of the carrier wave, and converts the transmitted bit sequence 100 into a modulated signal which is a data symbol sequence. Examples of modulation methods in primary modulation are PSK (Phase Shift Keying) or FSK (Frequency Shift Keying). However, the modulation method applied in Embodiment 1 is not limited to these. The modulated signal output by the modulation unit 105 is input to the weighted multiplication unit A106 and the weighted multiplication unit B107.

[0026] The weighted multiplication unit A106 multiplies the modulated signal output from the modulation unit 105 by a weighting coefficient A101, controlling the amplitude and phase of the modulated signal over a period of A weighting coefficients. The weighting coefficient A101 is used repeatedly for multiplication with the modulated signal every A weighting coefficients. More specifically, the weighted multiplication unit A106 controls the modulated signal so that its amplitude and phase are the same or different for each weighting coefficient period, which is a time-divided period. It then multiplies each of all samples of the modulated signal by the corresponding weighting coefficient from among a plurality of weighting coefficients whose amplitude changes for each sample of the modulated signal, thereby generating a weighted modulated signal, which is a weighted version of the modulated signal.

[0027] The weighted multiplier unit B107 multiplies the modulated signal output from the modulation unit 105 by a weighting coefficient B102, controlling the amplitude and phase of the modulated signal over a period of weighting coefficient B. The weighting coefficient B102 is used repeatedly for multiplication with the modulated signal every B period of weighting coefficient. More specifically, the weighted multiplier unit B107 controls the modulated signal so that its amplitude and phase are the same or different for each weighting coefficient period, which is a period divided by time. It then multiplies each of all samples of the modulated signal by the corresponding weighting coefficient from among a plurality of weighting coefficients whose amplitude changes for each sample of the modulated signal, thereby generating a weighted modulated signal, which is a weighted version of the modulated signal.

[0028] The frequency conversion unit A108 converts the carrier frequency of the modulated signal output from the weighted multiplication unit A106 according to the frequency hopping pattern A103 at each period of weight coefficient A. More specifically, the frequency conversion unit A108 converts the carrier frequency of the weighted modulated signal output from the weighted multiplication unit A106 to the same or different carrier frequencies at each period of weight coefficient A, thereby generating a modulated signal with multiple carrier frequencies time-multiplexed.

[0029] The frequency conversion unit B109 converts the carrier frequency of the modulated signal output from the weighted multiplication unit B107 according to the frequency hopping pattern B104 at each weighting coefficient B period. More specifically, the frequency conversion unit B109 converts the carrier frequency of the weighted modulated signal output from the weighted multiplication unit B107 to the same or different carrier frequencies at each weighting coefficient B period, generating a modulated signal with multiple carrier frequencies time-multiplexed.

[0030] The channel combining unit 110 adds the frequency hopping signals output from the frequency conversion unit A108 and the frequency conversion unit B109 to generate a combined signal of modulated signals containing multiple carrier frequencies. More specifically, the channel combining unit 110 adds the weighted modulated signals of two carrier frequencies output from the frequency conversion unit A108 and the frequency conversion unit B109 to generate a combined signal of weighted modulated signals of two carrier frequencies.

[0031] The digital-to-analog conversion unit 111 converts the digital modulated signal output from the channel combining unit 110 into an analog modulated signal.

[0032] The transmitting high-frequency unit 112 performs frequency conversion on the analog modulated signal output from the digital-to-analog conversion unit 111 to generate a radio frequency signal, which is a transmission signal in the radio frequency band. However, if the frequency conversion unit A108 and frequency conversion unit B109 each perform the conversion to radio frequency, the frequency conversion of the analog modulated signal performed by the transmitting high-frequency unit 112 becomes unnecessary.

[0033] The transmitting antenna 113 radiates the radio frequency signal generated by the transmitting high-frequency unit 112 as radio waves.

[0034] Next, the hardware configuration of the transmitting device 10 according to Embodiment 1 will be described. The modulation unit 105, weighted multiplication unit A106, weighted multiplication unit B107, frequency conversion unit A108, frequency conversion unit B109, channel combining unit 110, digital-to-analog conversion unit 111, and transmission high-frequency unit 112 of the transmitting device 10 are realized by a processing circuit. The processing circuit may be dedicated hardware, or it may be a control circuit having a memory and a CPU (Central Processing Unit) that executes a program which is a computer program stored in the memory.

[0035] Examples of memory include non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), or flash memory, as well as magnetic disks or optical disks. When the processing circuit is a control circuit with a CPU, an example of the control circuit is the control circuit 400 with the configuration shown in Figure 5.

[0036] Figure 5 is a block diagram showing the configuration of a control circuit 400 that realizes the spread spectrum communication device 10 according to Embodiment 1. As shown in Figure 5, the control circuit 400 has a processor 401 which is a CPU and a memory 402. When the modulation unit 105, weighted multiplication unit A106, weighted multiplication unit B107, frequency conversion unit A108, frequency conversion unit B109, channel combining unit 110, digital-to-analog conversion unit 111, and transmission high-frequency unit 112 of the transmitting device 10 are realized by the control circuit 400 shown in Figure 5, programs for realizing each of the functions of the modulation unit 105, weighted multiplication unit A106, weighted multiplication unit B107, frequency conversion unit A108, frequency conversion unit B109, channel combining unit 110, digital-to-analog conversion unit 111, and transmission high-frequency unit 112 are stored in the memory 402.

[0037] The functions of the modulation unit 105, weighted multiplication unit A106, weighted multiplication unit B107, frequency conversion unit A108, frequency conversion unit B109, channel combining unit 110, digital-to-analog conversion unit 111, and transmission high-frequency unit 112 are realized when the processor 401 reads and executes the program stored in memory 402. Memory 402 is also used as temporary memory for each process executed by the processor 401.

[0038] Some functions of the modulation unit 105, weighted multiplication unit A106, weighted multiplication unit B107, frequency conversion unit A108, frequency conversion unit B109, channel combining unit 110, digital-to-analog conversion unit 111, and transmission high-frequency unit 112 may be implemented by dedicated hardware, while the remaining functions may be implemented by the control circuit 400. The dedicated hardware may be a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit combining these.

[0039] Figure 6 shows a processing circuit 500 in which some or all of the functions of the modulation unit 105, weighted multiplication unit A106, weighted multiplication unit B107, frequency conversion unit A108, frequency conversion unit B109, channel combining unit 110, digital-to-analog conversion unit 111, and transmission high-frequency unit 112 of the spread spectrum communication device 10 according to Embodiment 1 are realized by a processing circuit 500 which is dedicated hardware. The processing circuit 500 is dedicated hardware.

[0040] As described above, the spread spectrum communication device 10 according to Embodiment 1 controls the amplitude and phase of the modulated signal using one weighting coefficient having a period, amplitude, and phase determined so that the modulated signal has a desired bandwidth, and another weighting coefficient obtained by time-offsetting the said weighting coefficient by the chip period, thereby generating two types of modulated signals with widened bandwidths. By performing frequency conversion on each of the two types of modulated signals according to two types of frequency hopping patterns to generate a composite signal, it is possible to generate a high-speed frequency-hopping signal that spreads the modulated signal to an arbitrary bandwidth while rapidly hopping to an arbitrary carrier frequency.

[0041] Conventionally, when using multiple discrete unused frequencies, each with a different bandwidth, for communication, it is necessary to prepare multiple circuits that generate modulated signals corresponding to the bandwidth of the unused frequencies in order to efficiently utilize the frequencies. However, the transmitter 10 can easily adjust the bandwidth of the modulated signal simply by changing the period of the weighting coefficient according to the bandwidth of the unused frequencies. As a result, the transmitter 10 can improve frequency utilization efficiency without increasing the circuit size or computational load. Furthermore, in high-speed frequency hopping transmission, the transmitter 10 can efficiently utilize unused frequency bands and improve frequency utilization efficiency by flexibly adjusting the frequency switching speed according to the available frequency band conditions, while suppressing the effects of intersymbol interference and the increase in circuit size.

[0042] By using a time window function, such as a Han window, to time-offset the two weighting coefficients so that one weighting coefficient has maximum amplitude and the other weighting coefficient has zero amplitude at the center of the chip signal, thereby preventing intersymbol interference, the peak factor of high-speed frequency-hopping signals can be reduced, enabling transmission with high transmission power efficiency. As a result, compared to conventional frequency-hopping transmission without weighting, higher power efficiency is achieved, and it becomes possible to use inexpensive amplifiers such as Class C amplifiers, and the wireless transmission distance can also be extended.

[0043] By irregularly changing the period, amplitude, and phase of the weighting coefficients and the frequency hopping pattern, the transmitting device 10 can make it difficult for the receiving side to reconstruct the signal, similar to the spread sequence and frequency hopping pattern in conventional direct spread spectrum, thereby improving interception resistance and confidentiality.

[0044] Furthermore, the weighted multiplication unit A106 and the weighted multiplication unit B107 may be configured as follows: Each of the weighted multiplication unit A106 and the weighted multiplication unit B107 divides the symbol period into weight coefficient periods. The amplitude of each weight coefficient in the multiple weight coefficient periods is controlled by applying a time window. Each of the weighted multiplication unit A106 and the weighted multiplication unit B107 uses a sequence that controls the phase by giving each of the multiple weight coefficient periods a different phase offset, and multiplies the modulated signal by the corresponding weight coefficient from a plurality of weight coefficients that have been cyclically shifted by a different sample offset for each sequence, thereby generating a weighted modulated signal.

[0045] The phase controlled at each weight coefficient period may be determined by using multiple weight coefficients with phase offsets such that there is a phase difference of π / 2 or -π / 2 between adjacent chip signals.

[0046] Embodiment 2. In Embodiment 1, the weight coefficient multiplication unit A106 and the weight coefficient multiplication unit B107 generate a modulated signal with a bandwidth adjusted by a fixed period using fixed period weight coefficients A101 and B102. The spread spectrum communication device according to Embodiment 2 generates modulated signals with multiple bandwidths within the same communication and generates a multiplexed frequency hopping signal.

[0047] Figure 7 shows the configuration of the spread spectrum communication device 50 according to Embodiment 2. The configuration of the transmitting device 50 is the same as that of the transmitting device 10 according to Embodiment 1 shown in Figure 2, but the difference between Embodiment 2 and Embodiment 1 is that multiple weight coefficient periods having multiple periods are applied to each of the weight coefficient A'501 and weight coefficient B'502 within the same communication, and frequency hopping patterns A'503 and B'504 corresponding to these multiple weight coefficient periods are input to the transmitting device 50. In Embodiment 2, the same reference numerals are used for components that are the same as those in Embodiment 1, and their descriptions are omitted.

[0048] As shown in Figure 7, in Embodiment 2, the weight coefficients A'501 and B'502 input to the transmitting device 50 are different from the weight coefficients A101 and B102 in Embodiment 1. Therefore, the weight coefficients A'501 and B'502 will be described below.

[0049] Figure 8 shows an example of weight coefficients A'501 and B'502 applied to the modulated signal in Embodiment 2. In the example in Figure 8, the symbol period is divided into 31 samples, and three types of weight coefficient periods are set: period 1 with a 2-sample period, period 2 with an 8-sample period, and period 3 with a 4-sample period. When the weight coefficient period changes, the chip period also changes accordingly. Chip period 1 corresponding to period 1 is 1 sample time, chip period 2 corresponding to period 2 is 4 sample time, and chip period 3 corresponding to period 3 is 2 sample time.

[0050] For each of the weight coefficients A'501 and B'502, the position of maximum amplitude is the center timing of the chip signal. To prevent interference between weight coefficients A'501 and B'502 at the center point of the chip signal, the amplitude of the other weight coefficient is reduced at the timing when one of the weight coefficients reaches its maximum amplitude to suppress interference between chips. For example, by setting the amplitude of the other weight coefficient to zero at the timing when one weight coefficient reaches its maximum amplitude, interference between chips in the transmitted signal can be reduced to zero.

[0051] For the amplitudes of weight coefficients A'501 and B'502, a time window function with an adjusted period can be used depending on the bandwidth to be adjusted. For example, a generally known Han window can be used as the time window function. However, the values ​​applied to the weight coefficients in Embodiment 2 are not limited to this.

[0052] Each of the weighting coefficients A'501 and B'502 controls the phase of the modulated signal by applying a different phase offset for each period 1, period 2, and period 3. For example, in π / 2 shift BPSK, the weighting coefficient A'501 is selected from {0, π} and the amount of phase rotation is determined for each period, and the weighting coefficient B'502 is selected from {π / 2, -π / 2} and the amount of phase rotation is determined for each period. This orthogonals the phases between adjacent weighting coefficient periods, thereby suppressing intersymbol interference during transmission and reception. However, in Embodiment 2, the phase rotation applied to each of the weighting coefficients A'501 and B'502 is not limited to those described above and may be arbitrarily selected.

[0053] Figure 9 shows examples of frequency hopping patterns A'503 and B'504 in Embodiment 2. Frequency hopping pattern A'503 multiplies the modulated signal, which has been multiplied by the weighting coefficient A'501 output from the weighting multiplication unit A106, to the frequency channel f according to one of the periods 1, 2, and 3 of the weighting coefficient A' period. ０ , f １ , f ２ This is a sequence of frequency channels indicating the order of frequency channels for frequency hopping to one of the following. In the example shown in Figure 9, frequency hopping pattern A'503 is f within the symbol period. ０ →f ０ →f １ →f １ →f ２ →f ２ →f ０ This is a sequence that shows the order of [the elements].

[0054] The frequency hopping pattern B'504 multiplies the modulated signal, which has been multiplied by the weighting coefficient B'502 output from the weighting multiplication unit B107, to the frequency channel f, according to one of the periods 1, 2, or 3 of the weighting coefficient B' period. ０ , f １ , f ２ This is a sequence of frequency channels indicating the order of frequency channels for frequency hopping to one of the following. In the example shown in Figure 9, the frequency hopping pattern B'504 is f within the symbol period. ０ →f０ →f １ →f １ →f ２ →f ２ →f ０ This is a sequence that shows the order of [the elements].

[0055] Thus, in the example of the frequency hopping pattern of Embodiment 2, the chip signal with period 1 is on frequency channel f ０ The chip signal with period 2 hops to frequency channel f １ The chip signal with period 3 hops to frequency channel f ２ The weight coefficient period patterns are set to hop between them. Period 1, which has the shortest weight coefficient period time, has the widest bandwidth for the chip signal, and as the weight coefficient period time increases, the bandwidth narrows in the order of period 3, then period 2.

[0056] In other words, since the three weighting coefficient periods are period 1 (2-sample period), period 2 (8-sample period), and period 3 (4-sample period), a chip signal with 1 / 4 the bandwidth is generated for period 2 compared to period 1, and a chip signal with 1 / 2 the bandwidth is generated for period 3 compared to period 1. Therefore, the frequency hopping pattern can efficiently utilize frequency by selecting a chip signal with one of the periods (period 1, period 2, or period 3) and performing frequency hopping according to the bandwidth available at the frequency to be hopped.

[0057] Figure 10 is an explanatory diagram showing an example of a transmitted signal in Embodiment 2. Figure 10 shows the transmitted signal spectrum, including a frequency band 800 that cannot be used for communication and a frequency channel f that can be used for communication. ０ 801, frequency channel f １ 802 and frequency channel f ２ This indicates 803. As shown in Figure 10, depending on the availability of frequency channels, the chip signal with period 1 that has the widest bandwidth is sent to frequency channel f ０ The 801 is frequency-hopped, and the chip signal with period 2 that has the narrowest bandwidth is transmitted to frequency channel f １The 802 is frequency-hopped, and a chip signal with period 3, which becomes the intermediate bandwidth, is transmitted to frequency channel f. ２ Transmission is performed by frequency hopping to 803.

[0058] Thus, the spread spectrum communication device 50 according to Embodiment 2 generates multiple modulation signals with different bandwidths within the same communication and generates a multiplexed frequency-hopping signal. This allows the device to assign a chip signal with an appropriate bandwidth to an appropriate frequency channel according to the availability of usable frequency channels and transmit the signal. Therefore, compared to conventional transmitters that generate modulation signals with a fixed bandwidth, the device can improve frequency utilization efficiency without increasing circuit size or computational load.

[0059] Each of the multiple weighting coefficients may contain multiple different weighting coefficient periods.

[0060] Embodiment 3. In Embodiment 2, the weight coefficient multiplication unit A106 and the weight coefficient multiplication unit B107 generate modulated signals with multiple bandwidths using weight coefficients A'501 and B'502, which have multiple periods within the same communication. The spread spectrum communication device according to Embodiment 3 generates modulated signals with multiple bandwidths within the same communication and generates a multiplexed frequency hopping signal by adjusting the transmission power so that the power density per frequency is constant for each modulated signal with a different bandwidth.

[0061] Figure 11 shows the configuration of the spread spectrum communication device 90 according to Embodiment 3. The configuration of the transmitting device 90 is the same as that of the transmitting device 50 according to Embodiment 2 shown in Figure 7, but the difference between Embodiment 3 and Embodiment 2 is that each of the weighting coefficients A''901 and B''902 has multiple weighting coefficient periods within the same communication, and furthermore, it has a function to adjust the transmission power for each chip signal so that the power density per frequency is constant between modulated signals multiplied by weighting coefficients with different periods. For this reason, the same reference numerals are used for components identical to those in Embodiment 2, and their descriptions are omitted.

[0062] As shown in Figure 11, in Embodiment 3, the weight coefficients A''901 and B''902 input to the transmitting device 90 are different from the weight coefficients A'501 and B'502 in Embodiment 2. Therefore, the weight coefficients A''901 and B''902 will be described below.

[0063] Figure 12 shows an example of weight coefficients A"901" and B"902" applied to the modulated signal in Embodiment 3. In the example in Figure 12, the symbol period is divided into 31 samples, and three types of weight coefficient periods are set: period 1 with a 2-sample period, period 2 with an 8-sample period, and period 3 with a 4-sample period. When the weight coefficient period changes, the chip period also changes accordingly. Chip period 1 corresponding to period 1 is 1 sample time, chip period 2 corresponding to period 2 is 4 sample time, and chip period 3 corresponding to period 3 is 2 sample time.

[0064] For each of the weight coefficients A"901" and B"902", the position of maximum amplitude is the center timing of the chip signal, and to prevent interference between weight coefficients A"901" and B"902 at the center point of the chip signal, the amplitude of the other weight coefficient is reduced at the timing when one weight coefficient reaches its maximum amplitude to suppress interference between chips. For example, by setting the amplitude of the other weight coefficient to 0 at the timing when one weight coefficient reaches its maximum amplitude, interference between chips in the transmitted signal can be reduced to 0.

[0065] The amplitudes of weighting coefficients A''901 and B''902 are adjusted so that the power density per frequency remains constant between the modulated signals after multiplying by the weighting coefficients for each different weighting coefficient period. In the example in Figure 12, if the power in period 1, which has the narrowest bandwidth and the highest power density per frequency, is √P, then the power in period 3, which has twice the bandwidth of period 1, becomes √2P, and the power in period 2, which has four times the bandwidth of period 1, becomes √4P, thus adjusting the power in each period.

[0066] For each of the weighting coefficients A''901 and B''902, a time window function with adjusted period and amplitude can be used depending on the bandwidth and power to be adjusted. For example, a commonly known Han window can be used as the time window function. However, the values ​​applied to the weighting coefficients in Embodiment 3 are not limited to these.

[0067] Each of the weighting coefficients A''901 and B''902 controls the phase of the modulated signal by applying a different phase offset for each period 1, period 2, and period 3. For example, in π / 2 shift BPSK, the weighting coefficient A''901 is selected from {0, π} and the amount of phase rotation is determined for each period, and the weighting coefficient B''902 is selected from {π / 2, -π / 2} and the amount of phase rotation is determined for each period. This orthogonals the phases between adjacent weighting coefficient periods, thereby suppressing intersymbol interference during transmission and reception. However, in Embodiment 3, the phase rotation applied to weighting coefficients A''901 and B''902 is not limited to those described above and may be arbitrarily selected.

[0068] The transmitting device 90 inputs the weighting coefficient A''901 to the weighting multiplication unit A106 and the weighting coefficient B''902 to the weighting multiplication unit B107, and controls the amplitude and phase of the modulated signal according to the weighting coefficients.

[0069] Figure 13 is an explanatory diagram showing an example of a transmitted signal in Embodiment 3. Figure 13 shows the transmitted signal spectrum, including a frequency band 800 that cannot be used for communication and a frequency channel f that can be used for communication. ０ 1101, frequency channel f １ 1102 and frequency channel f ２ This indicates 1103. As shown in Figure 13, the transmitting device 90 transmits a chip signal with period 1 that has the widest bandwidth to frequency channel f, depending on the availability of frequency channels. ０ Frequency hopping is performed on 1101, and the chip signal with period 2 that has the narrowest bandwidth is transmitted to frequency channel f １ Frequency hopping is performed on 1102, and a chip signal with period 3, which has an intermediate bandwidth, is transmitted to frequency channel f ２The signal is transmitted by frequency hopping to 1103. As shown in Figure 12, the transmitting device 90 can generate a frequency-hopping multiplexed signal with a constant power density per frequency between frequency channels by controlling the transmission power for each different weighting coefficient period.

[0070] Thus, the spread spectrum communication device 90 according to Embodiment 3 generates a modulation signal with a constant power density per frequency across multiple bandwidths within the same communication, thereby generating a frequency-hopping multiplexed signal. As a result, the transmitting device 90 can assign a chip signal with power controlled by an appropriate bandwidth to an appropriate frequency channel and transmit it, depending on the availability of usable frequency channels. Therefore, in addition to achieving the effects obtained in Embodiment 2, the transmitting device 90 also has the effect of preventing interference with other systems and achieving efficient frequency utilization when applied to wireless communication systems where an upper limit on frequency power density is defined.

[0071] For example, a weighting coefficient that includes multiple weighting coefficient periods uses multiple weighting coefficients with amplitude ratios assigned so that the power density of the frequency spectrum is equivalent between chip signals generated with different weighting coefficient periods.

[0072] Figure 14 shows a storage medium 600 that stores a program for executing the operation of a spread spectrum communication device 10, 50, 90 according to any of the embodiments 1 to 3. The storage medium 600 is a storage medium that stores a program for controlling the spread spectrum communication devices 10, 50, and 90 that perform spread spectrum in the spread spectrum communication system 5, and stores a program that causes the spread spectrum communication devices 10, 50, and 90 to perform the following steps: a modulation step in which a transmission bit sequence is converted into a modulated signal using one or more of the phase, frequency, and amplitude of a carrier wave; a weighting multiplication step in which the modulated signal is controlled so that the amplitude and phase are the same or different for each weighting coefficient period, which is a period divided by time, and each of all samples of the modulated signal is multiplied by a corresponding weighting coefficient from a plurality of weighting coefficients whose amplitude changes for each sample of the modulated signal to generate a weighted modulated signal, which is a weighted signal of the modulated signal; a frequency conversion step in which the carrier frequency of the weighted modulated signal is converted to the same or different carrier frequency for each weighting coefficient period, and a modulated signal obtained by time multiplexing a plurality of carrier frequencies; and a channel synthesis step in which the weighted modulated signals of a plurality of carrier frequencies are added together to generate a composite signal of the weighted modulated signals of a plurality of carrier frequencies.

[0073] The configurations shown in the above embodiments are examples only, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the spirit of the invention.

[0074] 5. Spread Spectrum Communication System, 10, 50, 90. Spread Spectrum Communication Device, 20. Receiving Device, 100. Transmit Bit Sequence, 101. Weighting Coefficient A, 102. Weighting Coefficient B, 103. Frequency Hopping Pattern A, 104. Frequency Hopping Pattern B, 105. Modulation Unit, 106. Weighted Multiplication Unit A, 107. Weighted Multiplication Unit B, 108. Frequency Conversion Unit A, 109. Frequency Conversion Unit B, 110. Channel Synthesis Unit, 111. Digital-to-Analog Conversion Unit, 112. Transmit High-Frequency Unit, 113. Transmitting Antenna, 200, 201. Phase Offset, 400. Control Circuit, 401. Processor, 402. Memory, 500. Processing Circuit, 501. Weighting Coefficient A', 502. Weighting Coefficient B', 503. Frequency Hopping Pattern A', 504. Frequency Hopping Pattern B', 600. Storage Medium, 800. Frequency band, 801, 1101 frequency channels f ０ , 802, 1102 frequency channel f １ , 803, 1103 frequency channel f ２ , 901 Weight coefficient A'', 902 Weight coefficient B''.

Claims

1. A spread spectrum communication device comprising: a modulation unit that converts a transmission bit sequence into a modulated signal using one or more of the phase, frequency, and amplitude of a carrier wave; a weighting multiplication unit that controls the modulated signal so that its amplitude and phase are the same or different for each weighting coefficient period, which is a time-divided period, and multiplies each of all samples of the modulated signal by a corresponding weighting coefficient from a plurality of weighting coefficients whose amplitude changes for each sample of the modulated signal to generate a weighted modulated signal which is a weighted signal of the modulated signal; a frequency conversion unit that converts the carrier frequency of the weighted modulated signal into the same or different carrier frequency for each weighting coefficient period, and generates a modulated signal obtained by time-multiplexing a plurality of carrier frequencies; and a channel combining unit that adds the weighted modulated signals of the plurality of carrier frequencies to generate a combined signal of the weighted modulated signals of the plurality of carrier frequencies.

2. The spread spectrum communication device according to claim 1, characterized in that the weighted multiplication unit divides the symbol period into the weight coefficient period, controls the amplitude of each of the multiple weight coefficient periods by applying a time window, and the weighted multiplication unit uses a sequence that controls the phase by giving each of the multiple weight coefficient periods a different phase offset, and multiplies the modulated signal by the corresponding weight coefficient from a plurality of weight coefficients that have been cyclically shifted by a different sample offset for each sequence, thereby generating the weighted modulated signal.

3. The spread spectrum communication device according to claim 2, characterized in that the phase controlled at each weight coefficient period is obtained by using the plurality of weight coefficients to which a phase offset is given such that there is a phase difference of π / 2 or -π / 2 between adjacent chip signals.

4. The spread spectrum communication device according to claim 3, characterized in that the plurality of weighting coefficients include a plurality of different weighting coefficient periods.

5. The spread spectrum communication device according to claim 4, characterized in that the weight coefficients, which include the plurality of weight coefficient periods, use the plurality of weight coefficients to which amplitude ratios are given such that the power density of the frequency spectrum is equivalent between chip signals generated with different weight coefficient periods.

6. A spread spectrum communication system characterized by comprising a spread spectrum communication device according to any one of claims 1 to 5.

7. A control circuit for controlling a communication device that performs spread spectrum in a spread spectrum communication system, characterized in that it causes the communication device to perform the following steps: a modulation step of converting a transmission bit sequence into a modulated signal using one or more of the phase, frequency, and amplitude of a carrier wave; a weighting multiplication step of controlling the modulated signal so that its amplitude and phase are the same or different for each weighting coefficient period, which is a period divided by time, and multiplying each of all samples of the modulated signal by a corresponding weighting coefficient from a plurality of weighting coefficients whose amplitude changes for each sample of the modulated signal to generate a weighted modulated signal which is a weighted signal of the modulated signal; a frequency conversion step of converting the carrier frequency of the weighted modulated signal into the same or different carrier frequency for each weighting coefficient period, and generating a modulated signal obtained by time multiplexing a plurality of carrier frequencies; and a channel synthesis step of adding the weighted modulated signals of the plurality of carrier frequencies to generate a composite signal of the weighted modulated signals of the plurality of carrier frequencies.

8. The control circuit according to claim 7, characterized in that, in the weighted multiplication step, the symbol period is divided into the weight coefficient period, the amplitude of each of the multiple weight coefficient periods is controlled by applying a time window, and in the weighted multiplication step, the corresponding weight coefficient from a plurality of weight coefficients that have been cyclically shifted by a different sample offset for each of the multiple weight coefficient periods is multiplied by the modulated signal using a sequence that controls the phase by giving each of the multiple weight coefficient periods a different phase offset, thereby generating the weighted modulated signal.

9. The control circuit according to claim 8, characterized in that the phase controlled at each weight coefficient period is obtained by using the plurality of weight coefficients to which a phase offset is given such that there is a phase difference of π / 2 or -π / 2 between adjacent chip signals.

10. The control circuit according to claim 9, characterized in that the plurality of weight coefficients include a plurality of different weight coefficient periods.

11. The control circuit according to claim 10, wherein the weight coefficients, which include the plurality of weight coefficient periods, are characterized in that the plurality of weight coefficients are given amplitude ratios such that the power density of the frequency spectrum is equivalent between chip signals generated with different weight coefficient periods.

12. A storage medium for storing a program for controlling a communication device that performs spread spectrum in a spread spectrum communication system, the storage medium storing a program that causes the communication device to perform the following steps: a modulation step of converting a transmission bit sequence into a modulated signal using one or more of the phase, frequency, and amplitude of a carrier wave; a weighting multiplication step of controlling the modulated signal so that it has the same or different amplitude and phase for each weighting coefficient period, which is a period divided by time, and multiplying each of all samples of the modulated signal by a corresponding weighting coefficient from a plurality of weighting coefficients whose amplitude changes for each sample of the modulated signal to generate a weighted modulated signal which is a weighted signal of the modulated signal; a frequency conversion step of converting the carrier frequency of the weighted modulated signal into the same or different carrier frequency for each weighting coefficient period to generate a modulated signal obtained by time multiplexing a plurality of carrier frequencies; and a channel synthesis step of adding the weighted modulated signals of the plurality of carrier frequencies to generate a composite signal of the weighted modulated signals of the plurality of carrier frequencies.

13. The storage medium according to claim 12, characterized in that in the weighted multiplication step, the symbol period is divided into the weight coefficient period, the amplitude of each of the multiple weight coefficient periods is controlled by applying a time window, and in the weighted multiplication step, the corresponding weight coefficient from a plurality of weight coefficients that have been cyclically shifted by a different sample offset for each of the multiple weight coefficient periods is multiplied by the modulated signal using a sequence that controls the phase by giving each of the multiple weight coefficient periods a different phase offset, thereby generating the weighted modulated signal.

14. The storage medium according to claim 13, characterized in that the phase controlled for each weight coefficient period is obtained by using the plurality of weight coefficients to which a phase offset is given such that there is a phase difference of π / 2 or -π / 2 between adjacent chip signals.

15. The storage medium according to claim 14, characterized in that the plurality of weight coefficients include a plurality of different weight coefficient periods.

16. The storage medium according to claim 15, characterized in that the weight coefficients, which include a plurality of weight coefficient periods, use a plurality of weight coefficients to which amplitude ratios are given such that the power density of the frequency spectrum is equivalent between chip signals generated with different weight coefficient periods.

17. A communication method in a communication device that performs spread spectrum in a spread spectrum communication system, comprising: a modulation step in which the communication device converts a transmission bit sequence into a modulated signal using one or more of the phase, frequency, and amplitude of a carrier wave; a weighting multiplication step in which the communication device controls the modulated signal so that it has the same or different amplitude and phase for each weighting coefficient period which is a period divided by time, and multiplies each of all samples of the modulated signal by a corresponding weighting coefficient from a plurality of weighting coefficients whose amplitude changes for each sample of the modulated signal to generate a weighted modulated signal which is a weighted signal of the modulated signal; a frequency conversion step in which the communication device converts the carrier frequency of the weighted modulated signal into the same or different carrier frequency for each weighting coefficient period to generate a modulated signal obtained by time multiplexing a plurality of carrier frequencies; and a channel synthesis step in which the communication device adds the weighted modulated signals of the plurality of carrier frequencies to generate a composite signal of the weighted modulated signals of the plurality of carrier frequencies.

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