JPH09181643A - Spread spectrum communication equipment - Google Patents

Abstract

(57) Abstract: Gain amplification and AGC function at high intermediate frequency make circuit design and component mounting difficult. In a wireless communication device that performs wireless communication by a spread spectrum method using direct spread, a received signal is converted into a first intermediate frequency signal, and the level of the first intermediate frequency signal is amplified to a constant level. This is converted into a second intermediate frequency signal having a higher frequency than this signal. Then, the analog correlation calculator extracts the clock synchronization signal from the second intermediate frequency signal, receives the clock synchronization signal, and demodulates the data from the first intermediate frequency signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication device for directly performing spread spectrum using an analog correlation calculator.

[0002]

2. Description of the Related Art Conventionally, a communication system using a spread spectrum system has been known. In a system using this method, for example, in a single-channel spread spectrum communication system, the original signal is multiplied by a signal (spread code) having a much wider band to perform spread spectrum, and the receiving side transmits the transmitted signal. The same spread code used for spread spectrum is used as a replica, and by performing periodic correlation calculation between this replica and the received signal, code synchronization is maintained at the same time as information transmission. .

FIG. 3 is a block diagram showing a configuration example of a receiver of a conventional wireless communication apparatus. In the figure, a high frequency signal processing unit (RF) 202 filters and amplifies a received signal from the receiving antenna 201, and converts it into a predetermined frequency signal. Then, the synchronization circuit 203 uses an analog correlation calculator or the like to capture and maintain synchronization with the spread code and the clock signal on the transmission side.

The spread code generator 204 is a synchronization circuit 203.
By the code synchronization signal and clock signal input from
The same n + 1 spreading codes as the spreading code group on the transmitting side are generated. Further, to the carrier reproduction circuit 205, of the output of the high frequency signal processing unit 202 and the output of the spread code generator 204, the spread code for carrier reproduction of PN0 is input,
The carrier signal is regenerated.

Also, the baseband demodulation circuit 206 outputs the output from the carrier reproduction circuit 205 and the high frequency signal processing section 2
Demodulation is performed in the base band by using n spread codes (PN1 to PNn) out of the output of 02 and the output from the spread code generator 204. And the parallel-serial converter 20
Reference numeral 7 converts n parallel demodulated data output from the baseband demodulation circuit 206 into serial data and outputs the serial data.

In the receiver having the above configuration, the signal received by the receiving antenna 201 is appropriately filtered and amplified by the high frequency signal processing section 202, as described above, and it remains the transmission frequency band signal, or It is converted into an appropriate intermediate frequency band signal and output. Then, this signal is input to the synchronization circuit 203, where spreading code synchronization and clock synchronization with the transmission signal are established using the reference spreading code PN0 output from the spreading code generator 204, and the code synchronization signal and The clock signal is output to the spread code generator 204.

After such synchronization is established, the spread code generator 2
Reference numeral 04 generates a spreading code group in which the clock and the spreading code phase match the spreading code group on the transmission side. Of these code groups, the spread code PN0 dedicated to synchronization is input to the carrier reproduction circuit 205. This carrier reproduction circuit 205
Then, the spread code PN0 dedicated to synchronization described above despreads the received signal converted to the transmission frequency band or the intermediate frequency band, which is the output of the high-frequency signal processing unit 202, and transmits the carrier wave in the transmission frequency band or the intermediate frequency band. To play.

In the above baseband demodulation circuit 206,
A reproduction carrier wave and a high frequency signal processing unit 20 by a multiplier (not shown)
The received signal is converted into a baseband signal by multiplying the output from 2 and removing an unnecessary signal from the obtained signal with a low-pass filter. Then, this baseband signal is distributed to n branches, and each branch is subjected to multiplication processing for each of the spreading codes (PN1 to PNn) output from the spreading code generator 204 and filtering by a low-pass filter. Correlation detection is performed on the divided channels and the baseband received spread signal is despread.

[0009]

However, the conventional receiver described above has the following problems.

For example, an analog correlation calculator represented by a SAW device generally requires a signal modulated into a carrier having a high frequency of 100 MHz or more. Therefore, the input of the synchronization circuit 203 is 10
It becomes 0MHz or more.

Further, since the analog correlation calculator requires a constant and relatively high level input signal in which the strength of the signal due to wireless transmission is corrected, an amplifier having a high gain at the intermediate frequency is used to adjust the level. AGC (Automatic Gain Control) control for controlling the signal level at a constant level is performed as the signal level is raised.

The high gain amplification and AGC function at such a high intermediate frequency make circuit design and component mounting difficult. Further, compared to a circuit handling a low intermediate frequency, costly parts are required, which further increases power consumption.

Further, in the receiver shown in FIG. 3, the output from the high frequency signal processing unit (RF) 202 is the synchronization circuit 203,
The carrier recovery circuit 205 and the base band demodulation circuit 206 are branched. In such a configuration,
In the actual device design, if it is designed so that signals of appropriate levels are given to the inputs of both blocks at this branch point, fine level matching is required at each node, which complicates the circuit.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to simplify the circuit configuration of a direct spread spectrum receiver using an analog correlation calculation element and further reduce the consumption. It is to realize power saving and cost reduction.

[0015]

In order to achieve the above object, the present invention provides a first frequency conversion means for converting a received signal into a first intermediate frequency signal, and the first intermediate frequency signal, Second frequency conversion means for converting into a second intermediate frequency signal having a frequency higher than that of the first intermediate frequency signal, correlation calculation means for extracting a synchronization signal from the second intermediate frequency signal, and receiving the synchronization signal Demodulation means for demodulating data from the first intermediate frequency signal.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of a receiver of a spread spectrum communication system according to the present invention.
In the receiving apparatus shown in the figure, a reception signal (for example, 2.4 GHz) from the antenna 11 is amplified by the RF Amp 12 at a predetermined amplification factor, and the amplified signal is used as the frequency converter MIX1 (1
Input to 3). This frequency converter MIX1 (13)
Then, the intermediate frequency IF1 corresponding to the local frequency Lo1
Is converted to Then, the frequency converter MIX1 (1
The output of IF1Amp14 following 3) is the AGC control unit 1
7. Baseband conversion frequency converter MIX3 (1
5), is input in parallel to the carrier reproducing unit 16 and the frequency converter MIX2 (20) for analog correlation calculation.

Incidentally, here, for example, 45 MHz is used as the intermediate frequency IF1, and as the intermediate frequency IF2, it matches the characteristics of the analog correlation calculator 22 described later.
For example, 180 MHz is used. Further, the input for analog correlation calculation must give a signal of a level sufficient for correlation calculation and a constant level in the preamble section 41 of the packet data shown in FIG.
That is, in the configuration of the wireless packet shown in FIG. 2, as described above, prior to the data demodulation, there is the print ampule section 41 for establishing clock synchronization, and the data section 42 in which the transmission data is modulated follows.

The level of the received signal from the antenna 11 greatly varies depending on the propagation condition of the space from the transmitting side as described above. Therefore, IF1Amp14 is added with an AGC function by the AGC circuit 17 for amplifying the fluctuating input signal to a predetermined level.

In the synchronizing circuit 23, the analog correlation calculator 2
By processing the output signal from 2, the clock signal synchronized with the data signal modulated into the received signal is extracted. In the above AGC circuit 17, the AGC from IF1Amp (14) is maintained so that the signal level of IF1 is kept constant.
It is fed back to the control input, and the carrier regeneration circuit 16
Frequency converter MIX by extracting carrier component from one signal
3 (15) obtains a baseband signal by using the extracted reproduction carrier.

The baseband signal thus obtained is sampled in the A / D converter 19 with the clock output from the synchronizing circuit 23, so that the digital processing section 24 in the next stage can Input synchronized digital data. The digital processing unit 24 reproduces the transmission data by a predetermined process.

As described above, according to the present embodiment, a relatively low frequency is selected as the first intermediate frequency irrespective of the characteristics of the analog calculator, and the signal input to the analog correlation calculator is: By converting the first intermediate frequency to a second frequency of 100 MHz or higher and a signal of an appropriate level so as to match the characteristics of this analog correlation calculator, the receiver circuit can be simplified and the circuit design can be facilitated. And the functions such as AGC can be easily realized.

Further, the first frequency conversion section and the subsequent demodulation section perform one frequency conversion configuration for frequency conversion, and a single branch point of the signal after AGC control is provided to each block in the subsequent stage. Since it is easy to distribute the appropriate level of, and the circuit configuration becomes simple as a result,
It is possible to realize low power consumption and low cost of the device.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus. In this case, the system or device can enjoy the effects of the present invention by reading the program into the system or device from a storage medium storing a program represented by software for achieving the present invention. Becomes

[0025]

As described above, according to the present invention,
The received signal is amplified to a sufficiently high level by a relatively low first intermediate frequency conversion, and the signal is converted to a second intermediate frequency higher than the first intermediate frequency conversion by the second frequency conversion means. With such a configuration, a circuit design optimized only for analog correlation calculation requiring a high frequency can be easily performed, and the circuit configuration can be simplified.

[0026]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a wireless packet according to the embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional spread spectrum communication receiver.

[Explanation of symbols]

 11 antenna 12 RF Amp 13 frequency converter MIX1 14 IF1Amp 15 frequency converter MIX3 16 carrier regeneration circuit 17 AGC control unit 19 A / D converter 20 frequency converter MIX2 22 analog correlation calculator 23 synchronization circuit 24 digital processing unit

Claims (4)

[Claims] 1. A first frequency conversion means for converting a received signal into a first intermediate frequency signal, and a second intermediate frequency having a frequency higher than that of the first intermediate frequency signal. Second to convert to a signal
Frequency conversion means, correlation operation means for extracting a synchronization signal from the second intermediate frequency signal, and demodulation means for receiving the synchronization signal and demodulating data from the first intermediate frequency signal. Spread spectrum communication device. 2. A means for holding the level of the first intermediate frequency signal at a predetermined level, wherein the predetermined level is a constant level that is not affected by the strength of the received signal. Item 1. The spread spectrum communication device according to Item 1. 3. The spread spectrum communication device according to claim 1, wherein the correlation calculation means is an analog correlation calculation element. 4. The spread spectrum communication device according to claim 1, wherein the demodulation processing by the demodulation means is processing for generating a baseband signal.