JPH04110038U - Wireless transmitter/receiver using spread spectrum - Google Patents

Abstract

(57) [Summary] [Objective] To realize a wireless transmitting/receiving device with a relatively simple configuration, which is difficult to mix with leakage of other SS modulated wave signal components during demodulation, and can reliably handle multiplexed signals. [Configuration] On the transmitter side, there are multiple FM modulators that frequency modulate multiple input modulated signals with carrier waves of different frequencies.
The receiver includes a modulation circuit, an adder that adds the outputs of these FM modulation circuits to obtain a multiplexed signal, and a spreading means that multiplies the multiplexed signal by a spreading code to spread the spectrum and outputs an SS modulated signal. On the side, there is a frequency converter that inputs an SS modulated signal and converts it to an intermediate frequency by heterodyne detection, and a frequency converter that despreads the frequency-converted SS signal by square operation to obtain a despread output (FM modulated wave). a despreading means, a plurality of bandpass filters each selectively transmitting only one FM modulation wave from among the plurality of FM modulation waves included in the despread output, and an audio signal by FM demodulating the output of each bandpass filter. and a plurality of FM demodulation circuits for obtaining signals such as information and information.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention uses FM modulation multiplexed signals to spread spectrum (Spread Spectrum). (also referred to as “SS” below) performs wireless transmission (communication, sending and receiving). The present invention relates to a wireless transmitting/receiving device.

0002

[Prior art and problems to be solved by the invention]

Regarding the handling of multiplexed signals in SS (spread spectrum), generally speaking, mutual This method combines multiple SS signals obtained using different broadband noise-like spreading codes. This refers to a code division multiplexing method in which multiplexing is performed using This has no choice but to be realized using a demodulation circuit and an SS demodulation circuit, and in a multiplexing system using a simple demodulation method. It is difficult to apply such a code division multiplexing method. The reason For explanation purposes, a conventional code division multiplexing method will be described below.

In primary modulation, the first modulated wave d ₁ (t)cosω ₁ t obtained by multiplying the first information d ₁ (t) by the first carrier wave cosω ₁ t is The first SS signal d ₁ (t)P ₁ (t)cosω ₁ t is obtained by multiplying by the spreading code P ₁ (t). Similarly _{, the} second spreading code _{P 2 (} t) to obtain the second SS signal d ₂ (t)P ₂ (t)cosω ₂ t (the same applies to the third and subsequent SS signals, so the explanation will be omitted). A common method is to add these SS signals together to obtain a composite SS signal, which is then output (transmitted) from an antenna or the like for practical use, and its application and widespread use are expected in the future.

[0004] On the demodulation (reception) side, there is a method of performing correlation demodulation using a correlation device such as a compolver or a matched filter, or a method of performing correlation demodulation using a correlation device such as a comporba or a matched filter, or a method of performing correlation demodulation using a first spreading code P ₁ (t) and a second spreading code equivalent to the above at the time of demodulation. There are methods to independently generate P ₂ (t) and perform despreading, but none of these methods can be called simple demodulation methods, and moreover, there is a problem that leakage of other SS modulated wave components is mixed in during demodulation. Therefore, it is desired to realize a simple demodulator (wireless transmitter/receiver) that can reliably handle multiple waves (composite SS signals).

[0005]

[Means to solve the problem]

The spread spectrum wireless transmitter/receiver of this invention uses voice signals and information on the transmitter side. Input multiple modulated signals such as signals and transmit them using carrier waves of different frequencies. Multiple FM modulation circuits that perform frequency modulation and the outputs of these FM modulation circuits are added together. Adder that obtains multiplexed signals and multiplies the multiplexed signals by a spreading code to perform spectrum spreading. , a first multiplier for outputting a spread spectrum modulated signal, The receiver side inputs the spread spectrum signal received from the antenna and converts it into a heterogeneous signal. A frequency converter that converts into an intermediate frequency by in-detection and a frequency-converted spectrum. A second method that despreads the spread signal by square operation and obtains the despread output (FM modulated wave). A multiplication means (despreading means) and a multiplication means (despreading means), A plurality of bandpass filters each selectively transmitting only one FM modulated wave, and each bandpass filter Equipped with multiple FM demodulation circuits to obtain signals such as audio signals and information by FM demodulating the output of the The above problem has been solved by configuring the system in a different manner.

[0006]

【Example】

A specific embodiment of the spread spectrum radio transmitter/receiver (hereinafter also simply referred to as "wireless transmitter/receiver") of the present invention will be described with reference to FIG. FIG. 1 is a block system diagram of an embodiment of a wireless transmitter/receiver according to the present invention, in which (A) shows a modulation section (transmission side) and (B) shows a demodulation section (reception side). In both figures, 2 to 4 are multipliers, 7 is an adder (synthesizing circuit), 9 is PNG (spreading code generation circuit), 11 to 15 is BPF (bandpass filter), and 16 is LPF (low pass filter). ), 21 to 23 are FM modulation circuits, 24 to 26 are FM demodulation circuits, A _{1 and} A ₂ are antennas, In ₁ to In ₅ are input terminals, and Out 1 to Out 3 are output terminals. Note that the cutoff frequency of the LPF 16 is 1/T, and it has a function of passing and transmitting only the main lobe of the spreading code.

[0007] Next, we will discuss the functions and operations of the wireless transmitter/receiver with this configuration in the frequency spectrum shown in Figure 2. This will be explained with reference to the vector diagram. First, in the modulation section (transmission side), the input terminal In ₁ ，In₂，In₃Therefore, the input signals S1(t), S2(t), and S3(t) such as information are respectively FM Different frequencies are supplied to the modulation circuits 21, 22, 23 as shown in FIG. are frequency modulated by the respective carrier waves. Each of these carrier waves is a carrier wave in multiple modulated waves. The frequency of 1/2 of the sum of the frequencies is the frequency of all the modulated waves supplied to the adder 7. The frequency allocation is set so that it does not overlap with any of the following {Figure 2 (C )reference}. The outputs of these plurality of FM modulation circuits 21 to 23 are combined by an adder 7. After converting the signal into a multiplexed FM modulated signal Mm(t), it is output to a multiplier (first multiplication means).

On the other hand, a clock signal C(t) is supplied from the input terminal In4 to the PNG 9, and a broadband noise-like spreading code PN is generated based on the clock signal. Only the main lobe of this spreading code PN is passed through the LPF 16 and transmitted to obtain a spreading code signal P(t) (see FIG. 3), which is supplied to the multiplier 2. As a result, the multiplier 2 performs SS modulation by multiplication with the multiplexed FM modulated signal Mm(t) to obtain the SS modulated wave output P(t)*Fm(t) (see FIG. 4), and the antenna It is output as radio waves from _A1 .

Next, the functional operation of the demodulator (receiving side) will be explained. First, the SS modulated wave P(t)*Fm(t) received by the antenna _A2 is supplied to the mixer (multiplier) 3 for frequency conversion via the BPF 11. On the other hand, the local oscillation signal is supplied from the input terminal In ₅ to the mixer (frequency converter) 3, where the frequency is converted to the low frequency band of the SS modulated wave, that is, the intermediate frequency by heterodyne detection, and the output is An SS modulated wave P(t)*fm(t) converted to an intermediate frequency is obtained.

This SS modulated wave P(t)*fm(t) is supplied to the despreading multiplier 4 from both input terminals via the BPF 12 (that is, forms a squaring circuit), and is Despreading is performed. Therefore, the output signal of the multiplier 4 is P ² (t)*fm ² (t). Note that, as is well known, P(t) is a spreading code that takes values of "+1" and "-1", so P ² (t) =1. As a result, only the squared FM modulation signal fm ² (t) is transmitted from the multiplier 4. Then, the FM modulation signals of one band (frequency band) are selected by the plurality of BPFs 13 to 15 having mutually different passbands, and are supplied to each of the FM demodulation circuits 24 to 26, where they are FM demodulated and converted into audio signals. Returning to signals such as information, the signals are output from output terminals Out1 to Out3, respectively.

[0011] By the way, an FM signal that has been squared has both the carrier frequency and the frequency deviation doubled. However, the fundamental properties of frequency modulation do not change, and the FM demodulated audio signal and information The information will be approximately the same as the original modulated signal on the transmitting side. Therefore, with the above configuration , to wirelessly transmit multiple signals such as audio signals and information without interfering with each other. This makes it possible to create a wireless transmitter/receiver capable of multiplex communication in a relatively simple manner. It can be provided in various configurations.

0012

[Effect of the idea]

Since the wireless transmitter/receiver of the present invention is configured as described above, the conventional SS modulated waves can be Leakage of other SS modulated wave components is mixed in during demodulation in multiplexing (code division multiplexing). There are no such inconveniences, and the simple and reliable despreading demodulation method can be used as is. It has the following characteristics. As a result, it can be used as a simple wireless communication means for consumer equipment. Excellent features such as wireless transmission and reception using SS modulation with a large amount of information can be realized at low cost. Effects can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a wireless transmitter/receiver according to the present invention.

FIG. 2 is a frequency spectrum diagram for explaining the operation of the device of the present invention.

FIG. 3 is a frequency spectrum diagram of a spreading code generated by the modulation section of the device of the present invention.

FIG. 4 is a frequency spectrum diagram of an SS modulated wave output from the modulation section of the device of the present invention.

[Explanation of symbols]

2-4 Multiplier 7 Adder 9 PNG (spreading code generation circuit) 11-15 BPF (bandpass filter) 16 LPF (low-pass filter) 21-23 FM modulation circuit 24-26 FM demodulation circuit A _1, A ₂ antenna

Claims (1)

[Scope of utility model registration request] Claim 1: The transmitter side includes a plurality of FM modulation circuits that input a plurality of modulated signals such as audio signals and information and frequency-modulates the signals using carrier waves of mutually different frequencies, and these FM modulation circuits. and a first multiplier for multiplying the multiplexed signal by a spreading code to perform spectrum spreading and outputting a spread spectrum modulated signal. a frequency converter that inputs a spread spectrum signal received from an antenna and converts it to an intermediate frequency by heterodyne detection; and a second frequency converter that despreads the frequency-converted spread spectrum signal by a squaring operation to obtain a despread output. a multiplier; a plurality of bandpass filters each selectively transmitting only one FM modulation wave from among the plurality of FM modulation waves included in the despread output; and FM demodulation of the output of each of the bandpass filters. 1. A wireless transmitting/receiving device using spread spectrum, characterized by comprising a plurality of FM demodulation circuits for obtaining signals such as audio signals and information.