CN101136705B - Full optical subcarrier demodulator and method of millimeter wave optical fiber radio uplink - Google Patents

Abstract

This invention relates to a full optical sub-carrier demodulation device and a method for mm wave fiber radio up link, in which, this invented demodulation device includes a base station and a central station characterizing that the base station of the mm wave fiber radio up-link includes a laser and a demodulator, the central station includes an optical filter and an optical process module, the optical demodulation module includes an optical detector and a low-pass filter device for 2ASK modulation signals, and the optical demodulation module includes one-bit difference time delay module, photoelectric converting device and a low-pass filter to side band of the DPSK modulation signal, avoiding using HF signal generator, HF broadband mixer, HF broadband merger and filters in the generation and transmission of mm wave signals.

Description

The full light sub carrier demodulating equipment and the method for millimeter wave optical fiber radio up link

Technical field:

A kind of full optical millimeter wave subcarrier demodulation techniques belong to the optical communication technology field, particularly millimeter wave subcarrier light territory down-conversion, demodulation and the signal processing of up link in the millimeter wave optical fiber radio connecting system.

Background technology:

Radio communication fast development in the last few years, wireless user's cumulative year after year, business be variation more, and data service is sharply soaring, makes broadband wireless signal and carrier frequency urgent day by day to the demand of high frequency millimeter wave expansion.The electronic bottleneck of electronic device makes it can not satisfy the growth of tomorrow requirement far away, and the millimeter wave optical fiber radio technology is utilized the low characteristic of decreasing in the broadband of optical fiber technology just, for the various wireless traffic information of comprehensive transmission provide necessary enormous bandwidth and transmission quality, can efficiently solve the difficult point problem that the broadband wireless communication network development is faced.Advantages such as the millimeter wave optical fiber radio system of high frequency wireless wide band signal has that volume is little, in light weight, cost is low, loss is little, anti-electromagnetic interference, broadband, low chromatic dispersion and high power capacity have solved that the traditional microwave transmission system exists in millimere-wave band that loss is big, problem such as a little less than the antijamming capability.In addition, it organically combines the adaptability and the mobility of the huge capacity of fiber optic network and Radio Access Network, for wireless network provides " last kilometer " seamless access, realized real meaning " anyone, any time; in any place, communication in any form " demand.

At present, in existing millimeter wave optical fiber radio up link, the millimeter wave subcarrier signal in light territory obtains the millimeter wave carrier signal in electric territory at central station by direct detection, by the down-conversion and the signal demodulation techniques in electric territory, obtains digital signal in the carrier wave again.This method all needs a large amount of electric territory millimetric wave device and subsystem for each millimeter wave subcarrier channel, costs an arm and a leg, and system bandwidth is subjected to the storage battery neck restriction of millimetric wave device, is difficult to further lifting.

Summary of the invention

The objective of the invention is to propose a kind of signal processing technology of full light, directly handle the multichannel millimeter wave subcarrier,, directly obtain baseband digital signal light territory millimeter wave appendix ripple down-conversion and demodulation in the light territory for solving the problems of the technologies described above.

The full light sub carrier demodulating equipment of a kind of millimeter wave optical fiber radio up link provided by the invention comprises base station and central station, and the base station comprises laser and optical modulator; Millimeter-wave signal has directly been transferred to the light territory by laser and optical modulator with signal after being received by antenna for base station, by Optical Fiber Transmission to central station; The central station of millimeter wave optical fiber radio up link comprises optical filter and optical modulator module;

Sideband for the 2ASK modulation signal: the optical modulator module comprises photo-detector, low-pass filtering device; The sub-sideband of the 2ASK that optical filter leaches is finished opto-electronic conversion by photo-detector, obtains base-band data signal through low-pass filtering then; For the sideband of DPSK modulation signal, the optical modulator module comprises one 1 bit difference time delay module, electrooptical device, low pass filter; The sub-sideband of the DPSK that optical filter leaches carries out opto-electronic conversion then by one 1 bit difference time delay module, and the output point signal obtains base-band data signal through low-pass filtering.

The full light sub carrier demodulation method of a kind of millimeter wave optical fiber radio up link provided by the invention is characterized in that, may further comprise the steps:

The signal that the wireless terminal emission comes is a millimeter-wave signal; The frequency spectrum of this millimeter-wave signal is shown in Fig. 2 (a);

By optical modulator this signal is modulated on the direct current light that produces by laser in the base station of millimeter wave optical fiber radio up link and obtains light signal.Direct current light (δ _Vopt+ δ _-vopt) expression; Modulation signal is with (F (ω)+F (ω)) represents; M is the modulation depth of intensity modulated; Through the spectrum F that obtains after the intensity modulated of modulator _Opt(ω) shown in Fig. 2 (b), can be expressed as:

$F_{\mathrm{opt}}\left(\mathrm{\ω}\right)=(1+\mathrm{mF}\left(\mathrm{\ω}\right)+\mathrm{mF}(-\mathrm{\ω}))*({\mathrm{\δ}}_{v_{\mathrm{OPT}}}+{\mathrm{\δ}}_{-v_{\mathrm{OPT}}})$

$={\mathrm{\δ}}_{v_{\mathrm{OPT}}}+{\mathrm{\δ}}_{-v_{\mathrm{OPT}}}+\mathrm{mF}(v_{\mathrm{OPT}}+\mathrm{\ω})+\mathrm{mF}(-v_{\mathrm{OPT}}-\mathrm{\ω})+\mathrm{mF}(-v_{\mathrm{OPT}}+\mathrm{\ω})+\mathrm{mF}(v_{\mathrm{OPT}}-\mathrm{\ω})$

After above-mentioned spectral signal is sent to central station, by optical filter, the filtering sideband

MF (ω+v _OPT) and mF (ω+v _OPT), the spectrum F of remaining sideband _Residual(ω) shown in Fig. 2 (c):

F _residual(ω)＝mF(ω-v _OPT)+mF(-ω-v _OPT)

The optical modulator module is according to signal format demodulation to be demodulated:

To the sideband of 2ASK modulation signal, finish opto-electronic conversion, low-pass filtering by existing photo-detector and just can obtain base-band data signal; If the sideband of DPSK modulation signal then can be finished optical modulator by the system of Fig. 4; The sub-sideband of the DPSK that leaches carries out opto-electronic conversion then by one 1 bit difference time delay module, and the output point signal can obtain base-band data signal through low-pass filtering.

Millimeter wave optical fiber radio up link full light sub carrier demodulation techniques basic principle such as Fig. 1 that the present invention proposes.In the base station portion of millimeter wave optical fiber radio up link, wireless terminal launch the frequency spectrum F of millimeter-wave signal _RFComprise that positive frequency component F (ω) and negative frequency divide two parts F (ω), to be expressed as F _RF=F (ω)+F is (ω), shown in Fig. 2 (a).

This signal is modulated on the direct current light that produces by laser by optical modulator, obtains modulated optical signal.Direct current light (δ _Vopt+ δ _-vopt) expression, modulation signal is with (F (ω)+F (ω)) expression is through the spectrum F that is obtained after the intensity modulated of optical modulator _Opt(ω) can be expressed as:

$F_{\mathrm{opt}}\left(\mathrm{\ω}\right)=(1+\mathrm{mF}\left(\mathrm{\ω}\right)+\mathrm{mF}(-\mathrm{\ω}))*({\mathrm{\δ}}_{v_{\mathrm{OPT}}}+{\mathrm{\δ}}_{{-v}_{\mathrm{OPT}}})$

$={\mathrm{\δ}}_{v_{\mathrm{OPT}}}+{\mathrm{\δ}}_{{-v}_{\mathrm{OPT}}}+\mathrm{mF}(v_{\mathrm{OPT}}+\mathrm{\ω})+\mathrm{mF}(-v_{\mathrm{OPT}}-\mathrm{\ω})+\mathrm{mF}(-v_{\mathrm{OPT}}+\mathrm{\ω})+\mathrm{mF}(v_{\mathrm{OPT}}-\mathrm{\ω})$

" * " is convolution algorithm in the formula, and m is the modulation depth of intensity modulated; Gained spectrum is shown in Fig. 2 (b).

After above-mentioned spectral signal is sent to central station, by optical filter, filtering sideband δ _-vOPT, δ _VOPT, mF (ω+v _OPT) and mF (ω+v _OPT), the spectrum F of remaining sideband _Residual(ω) shown in Fig. 2 (c), be expressed as:

F _residual(ω)＝mF(ω-v _OPT)+mF(-ω-v _OPT)

As can be seen: F _RFCentre frequency (ω) is ω _RF, and the skilful F of filtered residual sideband _ResidualCentre frequency (ω) is ω _RF+ v _OPT, and F _Residual(ω) also comprised F _RFAll spectrum informations that (ω) comprised.F _RF(ω) and F _ResidualDifference (ω) only is the difference of its centre frequency: F _RF(ω) at millimeter wave frequency band and F _Residual(ω) in the optical frequency frequency range.So we can utilize method of optics in the optical frequency frequency range to F _Residual(ω) handle, to substitute in electric territory F _RFThe method of (ω) handling obtains the baseband signal of needs.

In the scheme that the application proposes, received the back by the millimeter-wave signal of portable terminal emission by antenna for base station and handle without any need for electric territory, directly signal has been transferred to the light territory by laser and optical modulator, by Optical Fiber Transmission to central station.At central station, frequency band extraction and optical modulator module also are that the mode of full light is carried out signal processing in the light territory, realize the down-conversion and the demodulation of multichannel millimeter-wave signal simultaneously by method of optics.In the generation and transmission course of whole millimeter-wave signal, avoided the use of millimeter wave electric devices such as high frequency signal generator, high-frequency wideband frequency mixer, high-frequency wideband mixer, filter, simple in structure, dependable performance, with low cost.

Description of drawings

The full light down-conversion of Fig. 1 millimeter-wave signal and the basic schematic diagram of demodulation.

The full optical modulator evolution of spectrum figure of Fig. 2 millimeter-wave signal.(a) millimeter-wave signal frequency spectrum (b) to be demodulated has been modulated the spectrum (c) of millimeter-wave signal through the spectrum behind the optical filter

The full optical modulator technology of Fig. 3 multichannel millimeter wave subcarrier

The optical modulator module of Fig. 4 DPSK sideband

Fig. 5 1.5Gbps pseudo random sequence signal is through ber curve and eye pattern (subgraph among the figure) behind the demodulating equipment provided by the invention

Embodiment

Specific implementation can use the system as Fig. 3 simultaneously multichannel millimeter wave appendix ripple channel to be carried out full optical modulator with method above-mentioned.

The input pseudo random sequence is PRBS9, and speed is 1.5Gbps.Output eye pattern and ber curve are as shown in Figure 5.

In the scheme, the light source laser of central station adopts existing commercial Distributed Feedback Laser, and its wave band is in the dwdm system wavelength band of International Telecommunications Union's regulation.The used optical modulator of tip of a hair ripple that the modulation antenna is accepted, use be existing commercial Mach moral 40GHz-60GHz optical modulator once, it can be modulated to the millimeter-wave signal of the 40GHz-60GHz wave band that receives on the direct current light that laser produces.Sideband extraction module in the scheme uses existing commercial DWDM demodulation multiplexer.Its channel spacing is about 50GHz, and centered carrier is corresponding at interval with the 40GHz-60GHz between the sideband just in time and in the millimeter wave subcarrier, and it can isolate the sideband signals in the millimeter wave subcarrier.

Optical modulator module in the scheme, need mainly comprise two kinds according to signal format to be demodulated, to the sideband of 2ASK modulation signal, directly finish opto-electronic conversion, low-pass filtering and just can obtain base-band data signal by existing commercial 40GHz-60GHz photo-detector.If the sideband of DPSK modulation signal then can be finished optical modulator by the system of Fig. 4.The sub-sideband of the DPSK that leaches carries out opto-electronic conversion then by a 1bit difference time delay module (being the cycle that the difference amount of delay equals baseband signal).The output point signal can obtain base-band data signal through low-pass filtering.

Claims (2)

1. the full light sub carrier demodulating equipment of a millimeter wave optical fiber radio up link comprises base station and central station, it is characterized in that:

The base station of millimeter wave optical fiber radio up link comprises laser and optical modulator; Millimeter-wave signal has directly been transferred to the light territory by laser and optical modulator with signal after being received by antenna for base station, by Optical Fiber Transmission to central station; The central station of millimeter wave optical fiber radio up link comprises optical filter and optical modulator module;

Sideband for the 2ASK modulation signal: the optical modulator module comprises photo-detector, low-pass filtering device; The sub-sideband of the 2ASK that optical filter leaches is finished opto-electronic conversion by photo-detector, obtains base-band data signal through low-pass filtering then; For the sideband of DPSK modulation signal, the optical modulator module comprises one 1 bit difference time delay module, electrooptical device, low pass filter; The sub-sideband of the DPSK that optical filter leaches carries out opto-electronic conversion then by one 1 bit difference time delay module, and the output point signal obtains base-band data signal through low-pass filtering.

2. application rights requires the demodulation method of the full light sub carrier demodulating equipment of 1 described millimeter wave optical fiber radio up link, it is characterized in that, may further comprise the steps:

The signal that the wireless terminal emission comes is a millimeter-wave signal;

By optical modulator this signal is modulated on the direct current light that produces by laser in the base station of millimeter wave optical fiber radio up link and obtains light signal; Direct current light (δ _{ν opt}+ δ _{-ν opt}) expression; Modulation signal is with (F (ω)+F (ω)) represents; M is the modulation depth of intensity modulated; Through the spectrum F that obtains after the intensity modulated of modulator _Opt(ω) be expressed as:

$F_{\mathrm{opt}}\left(\mathrm{\ω}\right)=(1+\mathrm{mF}\left(\mathrm{\ω}\right)+\mathrm{mF}(-\mathrm{\ω}))*({\mathrm{\δ}}_{{\mathrm{\ν}}_{\mathrm{OPT}}}+{\mathrm{\δ}}_{-{\mathrm{\ν}}_{\mathrm{OPT}}})$

$={\mathrm{\δ}}_{{\mathrm{\ν}}_{\mathrm{OPT}}}+{\mathrm{\δ}}_{-{\mathrm{\ν}}_{\mathrm{OPT}}}+\mathrm{mF}({\mathrm{\ν}}_{\mathrm{OPT}}+\mathrm{\ω})+\mathrm{mF}(-{\mathrm{\ν}}_{\mathrm{OPT}}-\mathrm{\ω})+\mathrm{mF}(-{\mathrm{\ν}}_{\mathrm{OPT}}+\mathrm{\ω})+\mathrm{mF}({\mathrm{\ν}}_{\mathrm{OPT}}-\mathrm{\ω})$

After above-mentioned spectral signal is sent to central station, by optical filter, the filtering sideband

MF (ω+ν _OPT) and mF (ω+ν _OPT), the spectrum F of remaining sideband _Residual(ω): F _Residual(ω)=mF (ω-ν _OPT)+mF (ω-ν _OPT)

The optical modulator module is according to signal format demodulation to be demodulated:

For the sideband of 2ASK modulation signal, by photo-detector finish opto-electronic conversion, low-pass filtering obtains base-band data signal;

So to the sideband of DPSK modulation signal, the sub-sideband of the DPSK that leaches carries out opto-electronic conversion then by one 1 bit difference time delay module, the output point signal obtains base-band data signal through low-pass filtering.

Images